KENYA STANDARD  DKS 2971 :2022  
ICS 77.140 
First  Edition  
  
 © KEBS 2022   
 Standard Specifications for Design of 
Cold Formed Buildings  
 
 
 
 DKS  2971 : 2022  
ii © KEBS 2022  – All rights reserved  
 TECHNICAL COMMITTEE REPRESENTATION  
The following organizations were represented on the Technical Committee:  
Kenya Industrial Research and Development Institute  
Space and Style Ltd.  
Blackberr y House Ltd.  
Consumer Information Network  
Edge & Atelier Ltd.  
Kangemi Jua Kali Association  
Edge & Atelier Ltd.  
Kepsa/Kenya National Federation of Jua Kali  
Sub County Health Services, Kamukunji  
Dedan Kimathi University  
Aluglass Ltd.  
Mabati Rolling Mills L td. 
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from the Managing Director.KENYA S TANDARD  DKS 2971 :2022  
ICS ##.###  
First  Edition  
 
© KEBS 2022 – All rights reserved  iii 
   
Standard Sp ecifications For Design Of Cold 
Formed Buildings   
 
Kenya Bureau of Standards, Popo Road, Off Mombasa Road,  
P.O. Box 54974 - 00200,  Nairobi, Kenya  
 +254 020 6948000, + 254 722202137, + 254 734600471  
 info@kebs.org  
 @KEBS_ke  
 kenya bureau of standard s (kebs)  DKS  2971 : 2022  
iv © KEBS 2022  – All rights reserved  
 Foreword  
This Kenya Standard was prepared by the construction technology  Technical Committee under the guidance 
of the Standards Projects Committee, and it is in accordance with the procedures of the Kenya Bureau of 
Standards  
The objective of t his Standard is to provide designers of cold -formed steel structures with specifications for 
cold-formed steel structural members used for load -carrying purposes in buildings and other structures in 
simple and continuous construction. Its provisions apply to the majority of structures, although it is recognized 
that cases will arise when other proven methods of design may be more appropriate. It is intended to be 
compatible with BS 5950 -5:1998 and BS EN 1993 -1-3:2006, and at the same time to be as self -contained as 
possible.  
In the preparation of this standard, reference was made to the following publication  
AS/NZS 4600:2005 Cool Formed steel structures   
 
 DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  v 
  STANDARD SPECIFICATIONS FOR DESIGN OF COLD FORMED BUILDINGS  
1 Scope  
This Kenyan Standard specifies min imum requirements for the design of structural members cold - formed to shape from 
steel sheet, strip ,  plate  or  bar  not  more  than 8 mm in thickness and used for load -carrying purposes in  buildings. 
Sections may be either open or closed and should be made up of flat elements bounded either by free edges or by bends 
with included angles not exceeding 135 degrees  and intern al radii not exceeding 5t where t is the material thickness.  
Closed sections may be made either:  
i) by joining together two previousl y formed open sections by continuous welding;  
ii) from a single flat strip, by forming the corners to make a box, and conti nuously  
welding the longitudinal joint.  
Welded cold formed hollow sections conforming to BS EN 10219 are not covered by this Standard . 
It is  also applicable for structures other than buildings provided appropriate allowances are made for dynamic effects.  
This Standard does not apply to the design of structures subject to fire and brittle fracture  
2 Normative references  
The following re ferenced documents referred to in the text in such a way that some or all of their content constitutes 
requirements of this  document. For dated references, only the edition cited applies. For undated references, the latest 
edition of the referenced documen t (including any amendments) applies.  
3 Terms and definitions  
For the purposes of this document, the following terms and de finitions apply.  
3.1.1  Cold Fomed Steel Structural Members  
Shapes that are manufactured by press -braking blanks sheared from sheets, cut lengths of coils or plates, or 
by roll forming cold - or hot-rolled coils  or  sheets;  both  forming  operations being perfo rmed at ambient room  
temperature, that is, without  manifest addition of heat as required for hot-forming.  
 
3.1.2  Unformed Steel  
Steel as received from the steel producer or warehouse before being cold-worked as  a  result of fabricating  
operations.  
 
3.1.3  Unformed S teel Properties  
Mechanical properties of unformed steel, such as yield stress, tensile strength and ductility.  
 
3.1.4  Yield Stress  
The minimum yield stress in tension specified for the grade of steel in the appropriate Standard.  
 
3.1.5  Tensile Strength  
The minimum ult imate strength in tension specified for the grade of steel in the appropriate Standard.  
 
3.1.6  Ductility  
The capacity steel to undergo plas tic deformation without fracture.  
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vi © KEBS 2022  – All rights reserved  
 3.1.7  Structural Ductility Factor  
A numerical assessment of the ability of a structure to  sustain  cyclic  inelastic  displacements.  
 
3.1.8  Structural Performance Factor  
A numerical assessment of the ability of a building to survive  cyclic displacements.  
 
3.1.9  Structural Response Factor  
The level of force reduction available for a given system compared with an elastic structural system.  
 
3.1.10  Elements  
Simple shapes into which a cold -formed structural member is considered divided and may consis t of the following 
shapes:  
(a) Flat elements  Appearing  in cross -section  as rectangles.  (See  Figure  1.2.)  
(b) Bends Appearing in cross-section as sectors of circular rings, having the inside radius -
to-thickness  ratio less than or equal  to eight  (ri/t ≤ 8). (See  Figure  1.2.)  
(c) Arched elements Circular or parabolic  elements  having  the  inside  radius -to- 
thickness  ratio greater  than eight (ri/t > 8). (See  Figure  1.2.)  
 
3.1.11  Flat Compression Element  
A plane compression flange of  a  flexural  member or  a  plane web or flange of a compression member.  
 
3.1.12  Bend  
Portion adjacent to flat elements and having a  maximum  inside  radius -to-thickness ratio (ri/t) of 8. (See 
Figure  1.1.)  
 
3.1.13  Arch Compression Element  
A circular or parabolic arch -shaped compression element hav ing an inside radius -to-  thickness  ratio greater  
than 8, stiffened  at both ends  by edge  stiffeners.  (See  Figure  1.3(d).)  
 
3.1.14  Stiffened or p artially stiffened compression element  
A flat compression element of  which both edges parallel to  the direction of  stress are stiffened by a  web, 
flange, edge stiffener, intermediate stiffener, or  the like.  (See Figure  1.3(a).)  
 
3.1.15  Unstiffened compressi on element  
A flat compression element which is stiffened at only one edge parallel to the direction of stress. (See Fig ure 
1.3(b).)  
 
3.1.16  Multiple -stiffened element  
An element that is stiffened between webs, or between a web and a  stiffened edge, by means  of  
intermediate  stiffeners  that  are  parallel  to  the direction  of   stress.   (See  Figure  1.3(c).)  
 
3.1.17  Sub - element  
The portion between adjacent stiffeners, or between web and intermediate stiffener, or  between edge and  
stiffener  
 
3.1.18  Edge Stiffener  
Formed e lement at the edge of a flat compression element. (See Figure 1.4(a).)  
 
3.1.19  Intermediate Stiffeners  
Formed elements, employ ed in multiple -stiffened segments, and located between edges of  stiffened elements. 
(See Figure 1.4(b).)  
 
3.1.20  Segment (in a member subject to  bending)  
The length between adjacent cross -sections, which are fully or partially restrained, or the length between an 
unrestrained end and the adjacent cross -section,  which  is  fully or partially  restrained.  DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  vii 
   
3.1.21  Nominal Dimension  
A specified manufactured di mension.  
 
3.1.22  Length (of a compression member)  
The actual length (l) of an axially loaded compression member, taken as the length centre - to-centre of 
intersections with supporting members, or  the cantilevered length in the  case of a freestanding  member.  
 
3.1.23  Thickness  
The base steel thickness ( t), exclusive of coatings  
 
3.1.24  Feed Width  
Width of coiled or flat steel used in the produ ction of a cold -formed product.  
 
3.1.25  Effective Design Width  
Where the flat width of an element is reduced for design purposes, the reduced de sign width   is termed the 
effective width or effective design width.  
 
3.1.26  Point Symmetric Section  
A section symmetrical about a point (centroid) such as a Z-section  having  equal flanges.  (See Figure  
1.5(b).)  
 
3.1.27  Doubly Symmetric Section  
A section symmetric ab out two orthogonal axes through its centroid. (See Figure 1.5(a).)  
 
3.1.28  Singly Symmetric (monosymetric) Section  
A section s ymmetric about only one axis through its centroid. (See Figure 1.5(c).)  
 
3.1.29  Non- Symmetric (asymmetric) Section  
A section that is not symmet ric about either axes. (See Figure 1.5(d).)  
NOTE: if this section is cut around one axis one portion of a cut section  will not be an the exact  image of 
the part of section  that lies on the opposite face of axis.  
 
3.1.30  Assembly of Elements  
A system of interconn ected cold-formed steel elements that act together to resist action in such a way that the 
strength and deformation cap acity of the system  is  not  adversely  affected  by the buckling  or crippling  of any 
one element  of the system.  
 
3.1.31  Primary Structure  
The structural system provided to carry the forces generated in the structure to the ground.  
 
3.1.32  Braced Member  
Member for which the transverse displacement of one end of the member  relative  to  the other is effectively  
prevented.  
 
3.1.33  Load  
The value of a force approp riate for an action  
3.1.34  Action  
Set of concentrated or distributed forces acting on a structure (direct action), or deformat ion imposed on a 
structure or constrained within it (indirect action).  
 
3.1.35  Nominal Action Effect or Nominal Load  
An unfactored action effect  or load determined in accordance with the relevant loading Standard.  
 DKS  2971 : 2022  
viii © KEBS 2022  – All rights reserved  
 3.1.36  Action Effect  
Internal forces and bending moment s due to actions (stress resultants)  
 
3.1.37  Capacity Design Principles  
Appropriate material standard design and detailing provisions which enab le zones where post -elastic 
response is acceptable to be identified and detailed in a manner that ensures these  zones  are capable  of 
accepting  the inelastic  demands  placed  upon  them.  
NOTE: All other zones are to be designed to ensure that all other undesir able inelastic response mechanisms are 
suppressed and detailed in a manner that the ultimate limit state horizontal def ormations that they are expected to 
be subjected to, can be sustained without significant (e.g., greater than 20%) loss of load -carrying capacity after 
four complete cycles of loading.  
 
3.1.38  Capacity Reduction Factor  
A factor used to multiply the nominal capaci ty to obtain the design capacity.  
 
3.1.39  Nominal Capacity  
The capacity of a member or connection, calculated using the parameters specified in this Standard.  
 
3.1.40  Design Capacity  
The product of the capacity reduction factor and the nominal capacity.  
 
3.1.41  Design Action E ffect  
The action effect computed from the design values of the actions or design loads.  
 
3.1.42  Direct Strength Method  
An alternative design met hod that  provides predictions of  member resistance  without the  use of effective  
widths.  
 
3.1.43  Limit States  
States beyond  which the structure no longer satisfies the design criteria.  
 
NOTE: Limit states separate desired states (compliance) from undesired sta tes (non -compliance).  
 
3.1.44  Limit States, Serviceability  
States that correspond to conditions beyond which specified service  criteria for a  structure  or structural 
element are no longer  met. 
 
3.1.45  Limit States, Stability  
States that correspond to the loss of static equilibrium of a structure considered as a rigid body . 
 
3.1.46  Limit States, Ultimate  
States associated with collapse, or with  other similar forms of structural failure.  
 
NOTE: This generally corresponds to the maximum load -carrying resistance of a structure or s tructural element , 
but, in some cases, to the maximum applicable strain or deformation.  
 
3.1.47  Local Buckling  
A mode of buckl ing involving plate flexure alone without transverse deformation of the line or  lines of 
intersection of adjoining  plates.  
NOTE: It is tr eated separately from overall buckling resistance and modifies the capacity of cross -
sections.  
 
3.1.48  Distortional Buckling  
A mode of buckling involving change in cross -sectional shape, excluding local buckling.  
 
NOTE: It is known as lateral buckling  DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  ix 
   
3.1.49  Flexural -torsional Buckling  
A mode of buckling in which compression members can bend and twist simultaneously without change of c ross-
sectional shape.  
 
1.3.1.  Flexural Strength  
Material's ability to resist deformation under load. The flexural  strength represents the highes t stress experienced 
within the material at its moment of rupture.  
 
3.1.50  Clinching  
Structural fastening of two or more flat elements by single -point embossing or piercing without using additional 
material.  
 
3.1.51  Single -point Fastener  
A mechanical  connection  at a single discrete  point  such  as a screw  or rivet.  
 
3.1.52  Proof Testing  
Application of test loads to a  structure, sub -structure,  member or connection, to  ascertain  the structural  
characteristics  of only that one item under  test. 
 
3.1.53  Prototype Testing  
Application of test loads to one or more structures, sub -structures, members or connections , to ascertain the 
structural characteristic s of that class of structures , sub -structures, members or connections  which  are 
nominally  identical  to the units  tested.  
 
3.1.54  Pull-over (pull -through)  
Failure of a single -point connection by the sheet being pulled over the head  of the fastener or  the head  of the 
fastener  being  pulled  through  the sheet.  
 
3.1.55  Pull-out  
Failure of a single -point connection by the embedded part of the  fastener  being  pulled out  of the member.  
 
3.1.56  Can  
Implies a capability or possibility and refers to the  ability of the  user of the Standard , or to a possibility that is 
available or that might  occur.  
 
3.1.57  May  
Indicates the existence of an option.  
 
3.1.58  Shall  
Indicates that a stateme nt is mandatory.  
 
3.1.59  Should  
Indicates a recommendation (non -mandatory).  
 
3.1.60  Special Study  
A procedure for the analysis or design, or both, of the structure,  agreed  between  the  authority having 
statutory powers to control the design and erection of a structu re, and the design  engineer.  
 
 
 
 
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x © KEBS 2022  – All rights reserved  
  
 
 
                                                          
FIGURE  1.1   BENDS  
 
 
 
 
 
 
NOTE: The member illustrated consists of the following nine elements:  
(a) Elements 1, 3, 7, 9 are flat elements (flats).  
(b) Elements 2, 4, 6, 8 are bends ( ri/t ≤ 8). 
(c) Element  5 is an arched  element  (ri/t > 8). 
 
FIGURE 1.2    ELEMENTS  
 
 
 
 
 
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© KEBS 2022 – All rights reserved  xi 
  
 
 
FIGURE 1.3    STIFF ENING MODES  
 
 
 
 
FIGURE 1.4    STIFFENERS  
 
 
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xii © KEBS 2022  – All rights reserved  
 
 
 
 
 
 
FIGURE 1.5 EXAMPLES OF SECTION SYMMETRY  
 
 
 
 
3.2 Notations  
The symbols used in this Standard are listed in Table  1.4. 
Where non-dimensional ratios are involved, both the numerator and denominator are expressed in identical  
units.  
The dimensional units for length and stress in all expressions or equations are to be taken as millimetres (mm) 
and megapascals (MPa) resp ectively, unless specifically noted otherwise.  
An asterisk placed after a  symbol denotes a  design  action effect due to the design load for  the ultimate limit 
state.  
 
 
 
TABLE 1.4  DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  xiii 
  Symbol                   Description  Clause reference  
Ac minor diameter area  of a bolt  5.3.5.1  
Ae effective area of the bearing stiffener subjected to uniform 
compressive str ess; or 
effective area at the yield stress ( fy) to calculate Ns; or 
effective area at the critical stress ( fn) to calculate Nc 3.3.8.2, 3.4.1, 3.6.3  
Ag gross area of the element including stiffeners; or 
gross area of the cross -section  2.6.1, 3.2.2  
Agt gross area subject to tension in block shear rupture  5.6.3  
Agv gross area subject to shear in block shear rupture  5.6.3  
An net area of the cross -section; or 
net area of the connected part  3.2.2, 5.3.3, 5.4.2.2, 5.5.2.2  
Ant net area subject to tension in b lock shear rupture  5.6.3  
Anv net area subject to shear in block shear rupture  5.6.3  
Ao reduced area due to local buckling; or 
plain shank area of a bolt  3.6.3, 5.3.5.1  
As reduced area of a stiffener; or 
gross area of the stiffener; or 
cross -sectional ar ea of a transverse stiffener; or 
tensile stress area of a bolt  2.5.2, 2.6.2.1, 3.3.8.1,  
5.3.5.2  
Ase effective area of a stiffener  2.4.2, 2.5.2  
Ast gross ar ea of a shear stiffener  3.3.8.3  
As1, As2 area of a member in compression consisting of the 
transve rse stiffeners and a portion of the web  3.3.8.1  
Awn net area of the web  5.6.1  
a bracing interval; or 
shear panel length for unstiffened web elements; or distance 
between transverse stiffeners for stiffened web elements; or 
distance between centre -lines o f braces  3.3.3.2.1, 3.3.4.1, 3.3.8.3,  
4.3.3.4  
Bc constant  1.5.1.2  
b flat width of element excluding radii ; or 
length of the web hole; or 
flat width of elem ent excluding corners or bends; or 
half the length of the arched compression element  2.2.1.2, 2.2.4 .1, 2.5.2, 3.3.5,  
4.1.2  DKS  2971 : 2022  
xiv © KEBS 2022  – All rights reserved  
  
 
TABLE   1.4   ( continued ) 
 
Symbol              Description  Clause reference  
be effective width of uniformly compressed stiffened and 
unstiffened elements used for determining the capacity  2.2.1.2,  2.2.2.2,  2.2.3.2,  
2.3.1.2,  2. 3.1.3,  2.3.2.2,  
2.3.2.3, 2.4.2, 2.4.3, 2.5.3,  
2.6.1, 2.6.2.2, 2.7  
bed effective width of uniformly compressed stiffened and 
unstiffened elements used for de termining the deflection  2.2.1.3, 2.2.2.3  
be1, be2 effective width of stiffened element with stres s gradient  2.2.3.2, 2.2.3.3  
bf flange width of a channel - or Z-section  3.4.7, 4.3.3.3  
bo total flat width of the stiffened element  2.6.1, 2.6.2.1  
bp great est sub -element flat width  2.6.3.1  
b1 width of the flange projecting beyond the web for I -beams an d 
similar sections; or 
half the distance between webs for box - or U-type sections;  
or 
sum of the flange projection beyond the web and the depth of 
the lip fo r I-beams and similar sections; or 
width of stiffened element  2.1.3.2, 2.1.3.3, 2.3.2.2  
b2 width o f unstiffened element; or 
flat width of element with intermediate stiffener excluding 
radii; or 
total flat width of the edge -stiffened element  2.3.2.2, 2.5.2 , 2.7 
C for compression members, ratio of the total bend cross - 
sectional area to the total cross -sectional area of the full 
section; and 
for flexural members, ratio of the total bend cross -sectional 
area of the controlling flange to  the  full  cross -sectional 
area of the controlling flange;  or 
coefficient;  or 
bearing  factor  1.5.1.2, 3.3.6.2, 5.3.4.2,  
5.4.2.3  
Cb coefficient depending on moment distribution in the 
laterally unbraced segment  3.3.3.2.1  
Ci horizontal distance from the edge of the element to  the 
centre -line of the stiffener  2.6.3.1  
CTF coefficient for unequal end moment  3.3.3.2.1, 3.5.1  
Cl coefficient of bearing length  3.3.6.2  
Cms coefficient used to determine N * for multiple -span system  ib 
with midspan restraints  4.3.3.3  
Cmx, Cmy coeffi cient for unequal end moment  3.5.1  
Cr coefficient of inside bent radius  3.3.6.2  
Cs coefficient fo r moment causing compression or tension on the 
shear centre side of the centroid  3.3.3.2.1  
Cth coefficient used to determine N * for multiple -span system  ib 
with third -point restraints  4.3.3.3  
Ctr coefficient used to determine N * for multiple -span syste m ib 
with restraints at the support  4.3.3.3  DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  xv 
  Cw coefficient of web slenderness  3.3.6.2  
Cy compression strain factor  3.3.2.3  
cf amount of curling  2.1.3.2  DKS  2971 : 2022  
xvi © KEBS 2022  – All rights reserved  
  
 
TABLE   1.4   ( continued ) 
 
Symbol              Description  Clause reference  
d depth of a section;  or 
actual stiffener dimension  2.1.3.2, Figure 2.4.2(a),  
3.3.6.3, 3.4.7  
da average diameter of an arc spot weld at mid -thickness of tc; or 
average width of an arc seam weld  5.2.4.2, 5.2.5.2  
de effective diameter of a fused area of an arc spot weld; or 
effective width of an arc seam weld at fused surfaces  5.2.4.1, 5.2.4.2, 5.2.5.2  
df nominal diameter of a bolt, screw, blind rivet  Table 5.3.1, 5.3.2, 5.3.4.2,  
5.4.1,  5.4.2.1,  5.4.2.2,  
5.4.2.3,  5.5.1,  5.5.2.1,  
5.5.2.2, 5.5.2.3  
dh diameter of a hole  2.2.2. 2, Table 5.3.1, 5.3.2,  
5.6.1  
dl actual stiffener dimension; or 
overall depth of lip  Figure 2.4.2(a)  
do outside diameter of a tubular member  3.6.1, 3.6.2  
ds reduced effective width of a stiffener; or 
effective stiffener dimension  Figure 2.4.2(b)  
dse effective width of a stiffener; or 
effective stiffener dimension  Figure 2.4.2(b)  
dsh nominal shank diameter  Figure F1, Appendix F  
dw depth of the compressed p ortion of the web; or 
visible diameter of the outer surface of an arc spot weld; or 
width of an arc  seam weld; or 
screw head or washer diameter  3.3.2.3, 5.2.4.2, 5.2.5.2,  
5.4.3.2  
dwc coped depth of a web  5.6.1  
dwh depth of the web hole  2.2.4.1, 3.3.4.2  
d1 depth of the flat portion of a web measured along the plane of 
the web; or 
width of elements adj oining the stiffened element  2.1.3.4, 2.2.4.1, 2.6.1,  
3.3.4.1, 3.3.4.2, 3.3.6.2  
E Young’s modulus of elasticity (200 × 103 MPa)  2.2.1.2, 3.3.2.3, 5.2.4.2  
e edge distance measured in the line of the force from centre - 
line of an arc spot weld, arc seam weld or from centre of a 
bolt hole to the nearest edge of an adjacent weld or bolt  
hole,  or to the end of the connected  part toward  which  the 
force is directe d; or 
distance measured in the line of force from the centre of a 
standard hole to the nearest end of the connected part  5.2.4.3, 5.2.5.3, 5.3.2,  
5.4.2.4, 5.5.2.4  
ey yield strain  3.3.2.3  
F* p vertical design load supported by all purlin lines being 
restrained  4.3.3.3  
fc stress  at service  load in the cover  plate  or sheet;  or 
fatigue strength corrected  for thickness of  material  4.1.2, 6.1.3  
fcr plate elastic buckling stress  2.2.1.2, 3.4.2  DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  xvii 
  ff uncorrected fatigue strength  6.1.3  
fn critical stress  3.3.8.1 , 3.4.1, 3.6.3  
foc elastic flexural, torsional and flexural -torsional buckling 
stress  3.4.1, 3.4.2 , 3.4.3, 3.6.3  DKS  2971 : 2022  
xviii © KEBS 2022  – All rights reserved  
 TABLE   1.4 ( continued ) 
 
Symbol  Description  Clause reference  
fod elastic distortional buckling stress of the cross -section  3.3.3.3, 7.2.1.4 , 7.2.2.4,  
Paragraphs D1, D2, D3, 
Appendix D  
fol elastic local buckling stress  7.2.1.3, 7.2.2.3  
fox elastic buckling stress in an axially loaded compression 
member for flexural buckling about the x-axis 3.3.3.2.1  
foy elastic buckling stress in an axiall y loaded compression 
member for flexural buckling about the y-axis 3.3.3.2.1  
foz elastic buckling stress in an axially loaded compression 
member for torsional buckling  3.3.3.2.1, 3.4.3  
frn detail category reference fatigue strength at nr-normal 
stress  6.1.3 
frnc corrected detail category reference fatigue strength for 
normal stress  6.1.3  
frs detail category reference fatigue strength at nr-shear stress  6.1.3  
frsc corrected detail category reference fatigue strength for 
shear stress  6.1.3  
fu tensile st rength used in design; or 
tensile strength of sheet  1.5.1.1, 1.5.1.4, 1.5.1.6,  
1.5.2, 3.2.2, 5.3.4. 2 
fuf minimum tensile strength of a bolt  5.3.5.1  
fuv tensile strength of unformed steel  1.5.1.2  
fuw nominal tensile strength of a weld metal  5.2.2.2, 5.2. 3.4 
fu1 tensile strength used in the design of the connected plate of the 
thickness t1; or 
tensile  strength of the sheet in contact with the screw head or 
with the rivet head  5.2.3.3, 5.4.2.3, 5.5.2.3  
fu2 tensile strength used in the design of the connec ted plate of the 
thickness t2; or 
tensile strength of the sheet not in contact with the screw 
head or with the rivet head  5.2.3.3, 5.4.2.3, 5.5.2.3  
fy yield stress used in design; or 
yield stress of web steel; or 
yield stress of stiffener; or 
yield stress  used in design for the lower strength base steel;  
or 
tensile or compressive yield stress  1.5.1.1, 1.5.1.4, 1.5.1.6,  
1.5.2, 3.2.2, 3.3.2.3, 3.3.8.2,  
5.2.2.1, 6.1.3, 8.1.3  
fwy lower yield stress value of the beam web ( fy) or of the 
stiffener section ( fys) 3.3.8.1  
fya average design yield stress of a full section  1.5.1.2  
fyc tensile yield stress of ben ds 1.5.1.2  
fyf yield stress of flat portions; or 
yield stress of unformed steel if tests are not made; or 
yield stress of flat coupons of formed members  1.5.1.2, 8.1.4.1  
fys yield stress of stiffener steel  3.3.8.1  
fyv tensile yield stress of unformed st eel 1.5.1.2  DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  xix 
  f3 detail category fatigue strength at constant amplitude 
fatigue limit (5 × 106 cycles)  6.1.3  
 
 
 
TABLE   1.4 ( continued ) 
 
Symbol  Description  Clause reference  
f3c corrected detail category fatigue strength at constant 
amplitude fatigue limit  6.1.3  
   
f5 detail category fatigue strength at cut off limit (108 cycles)  6.1.3  
f5c corrected detail category fatigue strength at cut off limit  6.1.3  
f* design stress in the compression element calculated on the 
basis of the effective design width; or 
design stress range  2.2.1.2, 2.4.2, 6.1.3  
f * av average design stress in the full, unreduced flange width  2.1.3.2  
f * d design compressive stress in the  element being considered, 
based on the effective section at the load for which  
deflections are det ermined  2.2.1.3, 2.2.2.3, 2.6.2.2,  
2.6.3.2  
f * d1 calculated stress f * 1 2.2.3.3  
f * 
d2 calculated stress f * 2 2.2.3.3  
* fi design stress range for load ing event i 6.1.3  
* * f1  , f 2 web stresses calculated on the basis of the effective section 
specified in Clause 2.2.3.2 or the full section specified in 
Appendix F  2.2.3.2, 2.3.2.2  
G shear modulus of elasticity (80 × 103 MPa)  3.3.3.2.1  
Ia adequate sec ond moment of area of a stiffener, so that each 
component element behaves as a stiffened element  2.4.2, 2.5.2  
Ib second moment of area of the full, unreduced cross -section 
about the bending axis  3.5.1  
Ieff effective second moment of area for deflection  7.1.4 
Ig gross second moment of area  7.1.4  
Imin. minimum second moment of area  2.8 
Is second mome nt of area of a full stiffener about its own 
centroidal axis parallel to the element to be stiffened  2.4.2, 2.5.2  
Isp second moment of area of a stiffener a bout the centre -line of 
the flat portion of the element  2.6.2.1  
Iw warping constant for a cross -section  3.3.3.2.1, Paragraph E1, 
Appendix E  
Ix, Iy second moment of area of the cross -section about the 
principal x- and y-axes 3.3.3.2.1, 4.3.3.4  
Ix′ second moment of area of the cross -section about its 
centroidal axis perpendicular to the web  4.3.3.4  DKS  2971 : 2022  
xx © KEBS 2022  – All rights reserved  
 I x′y′ product of second moment of area of the full section about its 
major and minor principal axes parallel and perpendicular to 
the web  4.3.3.4  
Iyc second moment of area of the compression portion of a 
section about the centroidal axis of the full sectio n parallel 
to the web, using the full unreduced section  3.3.3.2.1  
i index for stiffener ‘ i’ 2.6.3.1  
J torsion constant for a cross -section  3.3.3.2. 1, Paragraph E1, 
Appendix E  DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  xxi 
   
TABLE   1.4   ( continued ) 
 
Symbol  Description  Clause reference  
k plate buck ling coefficient; or 
non-dimensional yield stress  2.2.1.2, 2.3.2.2, Table 2.4.2,  
2.5.2, 2.6.1  
kd plate buckling coefficient for distortional bucklin g 2.6.1  
kf total population variation due to fabrication  8.2.2  
kloc plate buckling coefficient for local sub-element buckling  2.6.1  
km total population of variation due to material  8.2.2  
ks shear stiffener coefficient  3.3.8.3  
kst stiffener type coeffi cient  3.3.8.2  
kt correction factor for distribution of forces; or 
factor to allow for variability of struc tural units  3.2.2, Tables 3.2 and 8.2.3  
kv shear buckling coefficient  3.3.4.1, 3.3.8.3  
k ′ coefficient used to determine N * where neither flange is  ib 
connected to the sheeting or connected to the sheeting with  
concealed fasteners  4.3.3.4  
l actual length of a compression member; or 
full span for simple beams; or 
distance between inflection p oints for continuous beams;  
or 
twice the length of cantilever beams; or 
unbraced length of a member; or 
laterally unbraced length of a member; or 
length of a member  1.3.21, 2.1.3.3, 3.3.3.2.1,  
3.3.3.2.2, 4.1.1, 4.3.3.3,  
6.1.3  
la lap length  Figure F1, Appe ndix F  
lb actual length of bearing  3.3.6.2, 3.3.6.3, 4.3.3.4  
lbr unsupported length of bracing or other restraint that 
restricts distortional buckling of the element  2.6.2.1  
lc unclamped length of the specimen  Figure F1, Appendix F  
le effective length of the member  3.4.2  
lex, ley, 
lez effective buckling for bending about the x- and y-axes, and for 
twisting, respectively  3.3.3.2.1  
leb effective length in the plane of bending  3.5.1  
lg gauge length for measuring the joint displacement  Figure F1, Appendi x F 
lst length of transverse stiffener  3.3.8.1  
lsb length of bearing stiffener  3.3.8.1  
lu limit of unbraced length by which lateral -torsional 
buckling is not considered  3.3.3.2.2  
lw length of the full size of the weld; or 
length of fillet weld  5.2.2.1,  5.2.3.3, 5.2.3.4,  
5.2.5.2  
lw1, lw2 leg lengths of fillet weld  5.2.3.4  
M moment due to nominal loads on member to be considered  7.1.4  DKS  2971 : 2022  
xxii © KEBS 2022  – All rights reserved  
 Mb nominal member moment capacity  2.2.1.2, 3.3.1, 3.3.3.1,  
3.3.3.2.1,  3.3.3.2.2,  3.3.3.3,  
3.3.3.4, 3.3.5, 3.6.2,  7.2.2.1 
Paragraph B2, Appendix B  DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  xxiii 
  TABLE   1.4   ( continued ) 
 
Symbol  Description  Clause reference  
Mbx, 
Mby nominal member moment capacities about the x- and 
y-axes, respectively  3.5.1, 3.5.2  
Mc critical moment  3.3.3.2.1, 3.3.3.3  
Mbd nominal member capacity for distortional buckling  7.2.2.1, 7.2.2.4  
Mbe nominal member capacity for lateral -torsional buckling  7.2.2.1, 7.2.2.2  
Mbl nominal member capacity for local buckling  7.2.2.1, 7.2.2.3  
Mmax.  absolute value of the maximum moment in the unbraced 
segment  3.3.3.2.1  
Mn nominal flexural capacity  7.1.4  
Mo elastic buckling moment; or 
elastic lateral -torsional buckling moment  3.3.3.2.1, 7.2.2.2  
Mod elastic buckling moment in the distortional mode  3.3.3.3, 7.2.2.4  
Mol elastic local buckling moment  7.2.2.3  
Ms nominal section moment capacity  2.2.1.2, 3.3.1, 3.3.2.1,  
3.3.2.2, 3.3.2.3, 3.3.3.5,  
3.3.5, 3.3.7  
Msxf, 
Msyf nominal section yield moment capacity of the full section 
about the x- and y-axes, respectively  3.5.2  
My moment causing initial yield at the extreme  compression 
fibre of a full section  2.2.1.2, 3.3.3.2.1, 3.3.3.3  
M1 smaller bending moment at the ends of the unbraced length  3.3.3.2  
M2 larger bending moment at the ends of the unbraced length  3.3.3.2  
M3 absolute value of the moment at quarter point of  the 
unbraced segment  3.3.3.2.1  
M4 absolute value of the moment at mid -point of the unbraced 
segment  3.3.3.2.1  
M5 absolute value of the moment at three -quarter point of the 
unbraced segment  3.3.3.2.1  
M* design bending moment  3.3.1, 3.3.5, 3.3.7, 3.6.2,  
Paragraph B2, Appendix B  
M * , M * x y design bending moment about the x- and y-axes, 
respectively  3.5.1, 3.5.2  
m constant; or 
non-dimensional thickness; or 
distance from the shear centre of one channel to the mid - 
plane of its web; or 
distance from the concentrated load to the brace  1.5.1.2, 4.1.1, 4.3.3.4,  
Paragraph E1, Appendix E  
Nc nominal member capacity of a member in compression  2.2.1.3, 3.3.8.1, 3.4.1, 3.4.7,  
3.5.1, 7.2.1.1  
Ncd nominal member capacity for distortional buckling  7.2.1.1, 7.2.1.4  
Nce nominal member capacity for flexural, torsional or 
flexural -torsional buckling  7.2.1.1, 7.2.1.2  
Ncl nominal member capacity for local buckling  7.2.1.1, 7.2.1.3  
Ne elastic buckling load  3.5.1  DKS  2971 : 2022  
xxiv © KEBS 2022  – All rights reserved  
 Nf nominal tensile capacity of the section of the connecte d part  5.3.3  DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  xxv 
   
 
 
TABLE   1.4   ( continued ) 
 
Symbol  Description  Clause reference  
Nft nominal tensile capacity of a bolt  5.3.5.2  
Noc least of the elastic column buckling load in flexural, 
torsional and flexural -torsional buckling  7.2.1.2  
Nod elastic dist ortional compression member buckling load  7.2.1.4  
Nol elastic local buckling load  7.2.1.3  
Nou nominal pull -out capacity of a screw  5.4.3.2  
Nov nominal pull -over (pull -through) capacity of a screw  5.4.3.2  
Ns nominal section capacity of a member in compr ession  2.2.1.2, 3.3.8.1, 3.4.1, 3.5.1  
Nsl nominal axial capacity for local buckling  7.2.1.1  
Nt nominal section capacity of a member in tension; or 
nominal capacity of the connection in tension; or 
capacity of the net section of the connected part  3.2.1, 3.5.2, 5.4.2.2, 5.4.3.2,  
5.5.2.2  
Nw nominal tensile or compressive capacity of a butt weld or an 
arc spot weld  5.2.2.1, 5.2.4.4  
Ny nominal yield capacity of a member in compression  7.2.1.2  
N* design axial force, tensile or compressive; or 
design concent rated load or reaction  1.5.1.4, 3.2.1, 3.3.8.1, 3.4.1,  
3.5.1, 3.5.2, 3.6.3, 4.1.1  
N * f design tensile force on the net section of the connected part  5.3.3  
N * ft design tensile force on a bolt  5.3.5.2, 5.3.5.3  
N * ib design force to be resisted by inte rmediate beam brace  4.3.3.3, 4.3.3.4  
N * 
t design tensile force on the net section of a connected part 
using screws or blind rivets  5.4.2.2, 5.4.3.2, 5.5.2.2  
N * w design tensile or compressive force normal to the area of a butt 
weld or an arc spot weld  5.2.2.1, 5.2.4.4  
n exponent  2.5.2  
nc number of compression flange stiffeners  Table 7.1.2  
nh number of holes in the critical plane  5.6.1  
ni number of cycles of nominal loading event i, producing  
f * i 6.1.3  
nn number of the shear planes with threads in tercepting the 
shear plane  5.3.5.1  
np number of parallel purlin lines  4.3.3.3  
nr reference number of stress cycles (2 × 106 cycles)  6.1.3  
nsc number of stress cycles  6.1.3  
nt number of tension flange stiffeners  Table 7.1.2  
nw number of web stiffeners/ folds  Table 7.1.2  
nx number of shear planes without threads intercepting the 
shear plane  5.3.5.1  
q intensity of the design load on a beam  4.1.1  DKS  2971 : 2022  
xxvi © KEBS 2022  – All rights reserved  
 R modification factor for the distortional plate buckling 
coefficient; or 
reduction factor; or 
radius of outs ide bend surface  2.6.1, 3.3.3.4, 3.3.3.5, 3.6.3,  
5.2.6.2  DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  xxvii 
  TABLE   1.4   ( continued ) 
 
Symbol  Description  Clause reference  
Rb nominal capacity for concentrated load or reaction for one 
solid web connecting top and bottom flanges  3.3.6.1, 3.3.6.2, 3.3.7  
Rd design capacity  1.6.3, 8.2.3  
Rf structural response factor  1.6.4.1  
Rmin. minimum value of the test results  8.2.3  
Rn nominal capacity for block shear rupture of the beam -end or 
tension member connection  5.6.3  
Ru nominal capacity  1.5.1.4, 1.6.3  
Rwc web crippling capacity for channel -section flexural 
member  3.3.8.2  
R* design concentrated load or reaction in the presence of 
bending moment  3.3.6.1, 3.3.7  
R* b design concentrated load or reaction  4.1.1  
r radius of gyration of the full, unreduced cross -section; or 
centre -line radius  3.4.2, Table 7.1.1  
rcy radius of gyration of one channel about its centroidal axis 
parallel to the web  4.1.1  
rf ratio of the force transmitted by the bolts or screws, or  
rivets at the section considered, divided by the tensi le force 
in the member at that section  5.4.2.2, 5.5.2.2  
ri inside bend radius  1.5.1.2, 3.3.6.2  
ro1 polar radius of gyration of the cross -section about the shear 
centre  3.3.3.2.1, 3.4.3  
rx, ry radii of gyration of the cross -section about the x- and 
y-axes, respectively  3.3.3.2  
r1 radius of gyration of I -section about the axis perpendicular to 
the direction in which buckling occurs for the given conditions 
of end support and intermediate bracing  4.1.1  
S slenderness factor; or 
fastener distance from the c entre -line of the web divided by 
the flange width for Z -section; or 
flange width minus the fastener distance from the centre - line 
of the web divided by the flange width for channel - sections; 
or 
spacing in line of the stress of welds, bolts, rivets connec ting 
a cover plate, sheet or a non -integral stiffener in compression 
to another element  2.4.2, 2.5.2, 2.7, 3.4.7, 4.1.2  
Se elastic section modulus of the effective section calculated 
with extreme compression or tension fibre at fy 3.3.3.5  
Sp structural p erformance factor  1.6.4.2.4  
S* design action effects [design actions]  5.6.3  
s fastener distance from the centre -line of the web divided by 
the flange width for Z -sections  3.4.7, 4.1.2  
sf spacing of bolts, screws or rivets perpendicular to the line of 
the force; or 
width of sheet, in the case of a single bolt, screw or rivet  5.3.3, 5.4.2.2, 5.5.2.2  DKS  2971 : 2022  
xxviii  © KEBS 2022  – All rights reserved  
  
TABLE   1.4   ( continued ) 
 
Symbol  Description  Clause reference  
sg vertical distance between two rows of connections nearest to 
the top and bottom flanges; or 
gauge, the distance measured at right angles to the direction 
of the design action in the member, centre -to- centre of 
holes in consecutive lines  4.1.1, 5.3.1  
smax.  maximum longitudinal spacing of welds or other 
connectors joining two channels to form an I-section  4.1.1  
sp staggered pitch distance measured parallel to the direction 
of the design action in the member, centre -to-centre of 
holes in consecutive  lines  5.3.1  
sw weld spacing  4.1.1  
t nominal base steel thickness of any element or section 
exclusive of coatings; or 
thickness of the uniformly compressed stiffened elements;  
or 
base thickness of beam web; or 
thickness of a channel - or Z-section; or 
thickness of the cover plate or sheet; or 
thickness of the thinnest connected part; or 
thickness of element;  or 
thickness of thinnest outside sheet; or 
thickness of the connected part; or 
thickness of the holed material; or 
base metal thickness;  or 
thickness of the part in which the end distance is measured;  
or 
thickness of coped web  1.3.52, 2.1.3.1, 2.2 .1.2, 
2.6.1, 3.3.8.1, 3.4.7, 4.1.2,  
4.3.3.3, 5.2.4.3, 5.2.5.2,  
5.2.7, 5.3.1, 5.3.2, 5.3.4.2,  
5.4.2.4, 5.5.2.4, 5.6.1  
tc total combined base steel thickness (exclusive of coatings) of 
sheets involved in shear transfer  5.2.4.2  
tf thickness of the flange  2.1.3.2  
tp plate thickness  6.1.3  
ts thickness of the stiffener  3.3.8.1  
tt design throat thickness of a butt weld  5.2.2.1, 5.2.3.4, 5.2.6.2  
tw thickness of a web  2.1.3.4, 3.3.4.1, 3.3.6.2,  
3.3.7  
t1 thickness of the connecting plate of the tensile strengt h fu1; or 
thickness of the sheet in contact with the screw head or 
rivet head  5.2.3.3, 5.4.2.3, 5.5.2.3  
t2 thickness of the connecting plate of the tensile strength fu2; or 
thickness of the sheet not in contact with the screw head or 
rivet head  5.2.3.3, 5 .4.2.3, 5.5.2.3  
Vb nominal bearing capacity of the connected part  5.3.4.2, 5.3.4.3, 5.4.2.3,  
5.5.2.3  
Vf nominal shear capacity of the connected part along two 
parallel lines in the direction of the applied force  5.3.2  
Vfv nominal shear capacity of a bol t or screw  5.3.5.1, 5.4.2.1, 5.5.2.1  DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  xxix 
  Vn nominal shear capacity of an arc seam weld or of a beam - end 
connection  5.2.5.2, 5.6.1  DKS  2971 : 2022  
xxx © KEBS 2022  – All rights reserved  
  
TABLE   1.4   ( continued ) 
 
Symbol  Description  Clause reference  
Vsc coefficient of variation of structural characteristic  8.2.2, Table 8.2.3  
Vv nominal shear capacity of the web  3.3.4.1, 3.3.4.2, 3.3.5  
Vw nominal shear capacity of a butt, fillet, arc spot, flare or 
resistance weld; or 
nominal shear force transmitted by the weld  5.2.2.2, 5.2.3.1, 5.2.4.2,  
5.2.4.3, 5.2.6.2, 5.2. 7 
V* design shear force  3.3.2.3, 3.3.4.1, 3.3.5  
V * b design bearing force on a screw or on a rivet; or 
design bearing force on the connected part  5.4.2.3, 5.5.2.3  
V * f design shear force of the connected part  5.3.2  
V * fv design shear force on a bolt , screw or rivet  5.3.5.1, 5.3.5.3, 5.4.2.4  
V * 
n design shear force on an arc seam weld or a beam -end 
connection  5.2.5.2, 5.6.1  
V * w design shear force on a butt, fillet, arc spot, flare or 
resistance weld  5.2.2.2, 5.2.3.1, 5.2.4.2,  
5.2.4.3, 5.2.6.2, 5. 2.7 
w width of the specimen  Figure F1, Appendix F  
wf feed width of the coiled or flat sheet  1.3.19, Note 2 to Figure E1, 
Appendix E  
x, y principal axes of the cross -section  3.3.3.2.1, 3.3.6.3  
xo, yo coordinates of the shear centre of the cross -section  3.3.3.2  
Zc effective section modulus calculated at a stress fc in the 
extreme compression fibre  3.3.3.3  
Ze effective section modulus calculated with the extreme 
compression or tension fibre at fy 3.3.2.2, 3.3.3.2.1  
Zf full unreduced section modulus for the extreme 
compression fibre  3.3.3.2.1, 3.3.3.3  
Zft section modulus of the full unreduced section for the 
extreme tension fibre about the appropriate axis  3.5.2  
α coefficient; or 
modification factor for type of bearing connection  4.3.3.3, 5.3.4.2  
αnx, αny moment amplification factors  3.5.1  
αs inverse of the slope of the S -N curve  6.1.3  
β coefficient  2.6.2.1  
βx, βy monosymmetry section constant about the x- and y-axes, 
respectively  3.3.3.2.1, Paragraph E2, 
Appendix E  
βtf thickness correction factor  6.1.3  
γ importance factor  2.6.2.1  
δ coefficient  2.6.2.1  
θ angle between the plane of the web and the plane of the 
bearing surface; or 
angle between the vertical a nd the plane of the web of the Z -
section  3.3.6.2, 4.3.3.3  
λ, λ1, λ2 slenderness ratio  2.2.1.2, 3.3.2.3, 3.3.7  DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  xxxi 
  λb non-dimensional slenderness used to determine Mc for 
members subject to lateral buckling  3.3.3.2.1  DKS  2971 : 2022  
xxxii © KEBS 2022  – All rights reserved  
 TABLE   1.4   ( continued ) 
 
Symbol  Descri ption  Clause reference  
λc non-dimensional slenderness used to determine fn; or non-
dimensional slenderness used to determine Nce; or non-
dimensional slenderness used to determine Mcd 3.4.1, 3.6.3, 7.2.1.2  
λd non-dimensional slenderness used to determine Mc for 
members subject to distortional buckling; or 
non-dimensional slenderness used to determine Ncd and Mbd 3.3.3.3, 7.2.1.4, 7.2.2.4  
λl non-dimensional slenderness used to determine Ncl; or 
non-dimensional slenderness used to determine Mbl 7.2.1.3, 7.2 .2.3 
μ structural ductility factor  1.6.4.2.2  
ν Poisson’s ratio = 0.3  2.2.1.2  
φ capacity reduction factor  1.5.1.4,  5.2.2.1,  5.2.2.2,  
5.2.3.1,  5.2.4.2,  5.2.4.3,  
5.2.5.2, 5.2.6.2, 5.2.7, 5.3.2,  
5.3.3, 5.3.5.1, 5.3.5.2,  
5.4.2.2, 5.4.2.3, 5.5.2.2,  
5.5.2.3,  5.5.2.4, 5.6.1, 5.6.3,  
6.1.3  
φb capacity reduction factor for bending  3.3.1, 3.5.1  
φc capacity reduction factor for compression  3.3.8.1, 3.4.1, 3.5.1  
φt capacity reduction factor for tension  3.2.1  
φv capacity reduction factor for shear  3.3.4.1  
φw capacity reduction factor for bearing  3.3.6.1, 3.3.8.2  
ρ quantity for load capacity; or 
effective width factor  1.5.1.2, 2.2.1.2, 2.3.2.2,  
2.6.1  
ωi coefficient  2.6.3.1  
ψ * * stress ratio f 2 / f1 2.2.3.2, 2.3.2.2, 3.3.8.3  
 
3.3 Materials  
3.3.1  Structural Steel   
3.3.1.1  Appli cable  steels  
Structural members or steel used in manufacturing shall comply with;  
(a)  BS EN 10025, BS EN 10111, BS EN 10147 or BS EN 10149 as appropriate; and   
(b) other  steels,  the properties  and suitability of  which  are in accordance    with Clause  
1.5.1.4. The yield stress (fy) and tensile strength ( fu) used in design shall be determined  
in accordance  with Section  8. 
(c) Other steels may be used, subject to approval of the engineer, provided due allowance is 
made for variation in properties, including ductility.  Requirements for materials are given in 
BS 5950 -7. or equvalent  
 
3.3.1.2  Strength increase resulting from cold forming  
Strength increase resulting from cold forming shall be permitted by substituting the average design yield 
stress (fya) of the full section  for  fy.  Such increase  shall  be limited to  Clauses 3.3 (excluding Clause 
3.3.3.2), 3.4, 3.5, 3.6 and 4.4. The limitations  and methods  for determining fya shall be as  follows:  DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  xxxiii  
  i (a) For axially loaded compression members and flexural members whose proportions are 
such t hat the quantity (ρ) for load capacity is unity, as determined in accordance with 
Clause 2.2 for each of the component elements of the  sections , the average design yield  
stress  (fya) shall  be determined  on the basis  of one of the following:  
 
(i) Full section t ensile tests (see Section  8). 
(ii) Stub column tests (see Section  8). 
(iii) The following  calculation:  
fya = Cfyc + (1 −  C)fyf  ≤ fuv ................................ .........................  1.5.1.2(1)  
where   
 
fya = average design yield stress of the steel in the full section of compression 
members or full flange sectio ns of flexural members  
C = for  compression  members, ratio  of  the total  bend cross -sectional 
area to the total cross -sectional area of the full section; and for 
flexural members, ratio of the total  bend  cross -sectional area  of 
the controlling flange  to the full cross -sectional area of the 
controlling  flange  
fyc = tensile yield stress of bends  
Bc f yv 
= 
(r  / t )m . . . 1.5.1.2(2)  
 
Equation 1.5.1.2(2) is applicable only if fuv/fyv is greater than or 
equal to 1.2, ri/t is less than or equal to 7 and the minimum  
included angle is less than or equal to 120°.  
Bc = constant  
 
                                             
                                           
fyv = tensile yield stress of unformed  steel  
ri = inside bend  radius  
m = constant  
         
  
fuv = tensile strength of unformed  steel  
fyf = yield stress of the flat portions (see Clause 8.1.4); or yield 
stress of unformed steel if tests are not made  
(b) For axially loaded tension members, fya shall be  determined by either  Item (a)(i) or  
Item (a)(iii). 
(c) The increase in yield strength due to cold working should not be utilized for members which 
undergo welding, annealing, galvanizing or any other heat treatment after forming which 
may produce softening.  
 DKS  2971 : 2022  
xxxiv  © KEBS 2022  – All rights reserved  
 3.3.1.3  Effect of welding  
The effect of any welding on the mechanical properties of a member shall be determined on the basis of 
tests on specimens of the full section containing the weld within the  gauge  length. Any necessary 
allowance for such effect shall be made in the structural use of the member. Welded connections for all 
grades conforming with AS 1163 and grades G250, G300, G350 and G450 steel conforming with  AS 1397, 
designed in accordance with  Clause  5.2.3  for fillet welds  and Clause  5.2.6  for flare welds  do not require  
further  testing.  
 
3.3.1.4  Ductili ty 
Steels not listed in Clause 1.5.1.1 and used for forming structural members and connections shall comply with 
the following requirements:  
 
(a) The ratio of tensile strength to yield stress shall be not less than 1.08. The total 
elongation shall be not less than 10% for a 50 mm gauge length or 7% for a 200 mm 
gauge length standard specimen tested in accordance with AS 1391. If these 
requirements  cannot  be met, the following  criteria  shall  be satisfied:  
(i) Local elongation in a 13 mm gauge length across the fracture shall be not less  
than 20%.  
(ii) Uniform  elongation  outside  the fracture  shall  be not less than 3%. 
If the ductility of the material is determined on the basis of the  local  and  uniform 
elongation criteria, the use of such material shall be restricted to  the design of 
purlins and girts in accordance with Clauses 3.3.2.2, 3.3.3.2, 3.3.3.3  and 3.3.3.4. 
For purlins and girts subject to combined axial load and bending moment (see 
Clause 3.5), N*/φRu shall  not exceed 0.15  
where  
N* = design axial  force  
φ = capacity reduction  factor  
Ru = nominal  capacity  
 
3.3.1.5  Acceptance of steels  
Certified mill test reports, or test certificates issued by the mill, shall constitute sufficient evidence of compliance 
with the Standards referred to in this Standard.  
The uncoated minimu m steel thickness at any location of the cold-formed product, as delivered to the job 
site, shall be not less than 95% of the  value  used  in  its  design.  However, lesser thicknesses shall be 
permitted at bends (forming corners) due to cold- forming  effects.  
 
3.3.1.6  Unidentified  steel  
If unidentified steel is used, it shall be free from  surface imperfections and  shall be  used  only where the 
particular physical properties of the steel and its weldability  will  not  adversely affect the design capacities 
and serviceability of the structure. Unless a full test in accordance with AS 1391 is made, the  yield stress of 
the steel used in design ( fy) shall be   170 MPa  or less,  and the tensile  strength  used  in design  (fu) shall  be 
300 MPa  or less.  
 
3.3.2  Design  stresses  
The minimum yield stress ( fy) and tensile strength ( fu) used in design shall not exceed the values given in Table 
1.5 for the appropriate steel grade.  
NOTE: Regardless of the closeness of yield stress and tensile strength of some steels, 
steel grades  given in Table 1.5 are  suitable for  cold-forming provided that an appropriate 
inside bend radius  ( ri) is chosen.  DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  xxxv 
   
 
 
 
TABLE   1.5  
MINIMUM STRENGTHS OF STEELS COMPLYING WITH  
AS 1163, AS 1397, AS/NZS 1594, AS/NZS 1595 AND AS/NZS 3678  
 
Applicable 
Standard  Grade  Yield stress ( fy) 
MPa  Tensile strength ( fu) 
MPa  
AS 1163  C250 and C250L0  250 320 
 C350 and C350L0  350 430 
 C450 and C450L0  450 500 
AS 1397  G250  250 320 
 G300  300 340 
 G350  350 420 
 G450*  450 480 
 G500†  500 520 
 G550‡  550 550 
AS/NZS 1594  HA1  (see N ote) (see Note)  
 HA3  200 300 
 HA4N  170 280 
 HA200  200 300 
 HA250, HU250  250 350 
 HA250/1  250 350 
 HA300, HU300  300 400 
 HA300/1, HU300/1  300 430 
 HW350  350 430 
 HW350  340 450 
 HA400  380 460 
 XF300  300 440 
 XF400  380 460 
 XF500  480 570 
AS/NZS 1595  CA220  210 340 
 CA260  250 350 
 CW300  300 450 
 CA350  350 430 
 CA500  500 510 
AS/NZS 3678  200 ( t ≤ 8 mm)  
200 (8 mm < t ≤ 12 mm)  200 
200 300 
300 
 250, 250L15 ( t ≤ 8 mm)  280 410 
 250, 250L15 (8 mm < t ≤ 12 mm)  260 410 
 250, 250L15 (12 mm < t ≤ 20 mm ) 250 410 
 250, 250L15 (20 mm < t ≤ 25 mm)  250 410 
 300, 300L15 ( t ≤ 8 mm)  320 430 
 300, 300L15 (8 mm < t ≤ 12 mm)  310 430 
 300, 300L15 (12 mm < t ≤ 20 mm)  300 430 
 300, 300L15 (20 mm < t ≤ 25 mm)  280 430 
 350, 350L15 ( t ≤ 8 mm)  360 450 
 350, 350L15  (8 mm < t ≤ 12 mm)  360 450 
 350, 350L15 (12 mm < t ≤ 20 mm)  350 450 
 350, 350L15 (20 mm < t ≤ 25 mm)  340 450 
 400, 400L15 ( t ≤ 8 mm)  400 480 
 400, 400L15 (8 mm < t ≤ 12 mm)  400 480 DKS  2971 : 2022  
xxxvi  © KEBS 2022  – All rights reserved  
  400, 400L15 (12 mm < t ≤ 20 mm)  380 480 
 400, 400L15 (20 mm < t ≤ 25 mm)  360 480 
 450, 450L15 ( t ≤ 8 mm)  450 520 
 450, 450L15 (8 mm < t ≤ 12 mm)  450 520 
 450, 450L15 (12 mm < t ≤ 20 mm)  450 520 
 450, 450L15 (20 mm < t ≤ 25 mm)  420 500 
 
 
TABLE   1.5   ( continued ) 
 
Applicable 
Standard  Grade  Yield stress ( fy) 
MPa  Tensil e strength ( fu) 
MPa  
 WR350, WR350/L0 ( t ≤ 8 mm)  340 450 
WR350, WR350/L0 (8 mm < t ≤ 12 mm)  340 450 
WR350, WR350/L0 (12 mm < t ≤ 20 mm)  340 450 
WR350, WR350/L0 (20 mm < t ≤ 25 mm)  340 450 
* Applies  to hard -rolled  material  of thickness  greater  than  or equal  to 1.5 mm 
† Applies to hard -rolled material of thickness greater than 1.0 mm but less than 1.5 mm  
‡ Applies to hard -rolled material of thickness less than or equal to 1.0 mm  
NOTE: For design purposes, yield and tensile strengths approximate those o f structural Grade HA200. For specific 
information contact the supplier.  
 
 
3.3.3  Fasteners and electrodes  
3.3.3.1  Steel bolts, nuts and washers  
Steel  bolts,  nuts and washers  shall   comply  with   AS 1110.1,  AS 1111.1,  AS 1112.1,  AS 1112.2, AS 
1112.3, AS 1112.4, AS/ NZS 1252, AS/NZS 1559 and AS 4291.1  
(ISO 898 -1), as appropriate.  
The use of high-strength fasteners, other than those complying with AS/NZS 1252, is permitted provided 
that evidence of their equivalence to high-strength bolts complying with AS/NZS 1252 is available.  
 
3.3.3.2  Welding  consumables  
All welding consumables shall comply with AS/NZS 1554.1, AS/NZS 1554.5 and  AS/NZS 1554.7, as 
appropriate.  
 
3.3.3.3  Screws  
Self-drilling screws shall comply with AS 3566.1 and AS 3566.2.  
 
3.3.3.4  Blind  rivets  
Blind rivets shall comply with the Industrial Fastener Institute document F114.  
3.4 Design Requirements  
3.4.1  Actions and combination of actions  
A structure and its components shall be designed for the actions and combination of actions  as specified in 
AS/NZS  1170.0.  
3.4.2  Structural analysis and desig n 
Structural analysis and design shall be in accordance with AS/NZS 1170.0.  
NOTE: Guidance on the applicability of elastic structural analysis to continuous beams 
and frames  is given in Appendix  B. 
 DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  xxxvii  
  3.4.3  Design  capacity  
The design capacity ( Rd) shall be determi ned by any one of the following:  
 
(a) The nominal capacity ( Ru) in accordance with Sections 2 to 7 and the capacity  
reduction factor (φ) given in Table 1.6 as appropriate, i.e., Rd = φRu. 
(b) Testing in accordance with Clause  8.2.3.  
 
(c) Where the composition  or  configuration  of  such  components  is  such  that  Item (a) 
or (b) cannot be made in accordance with those  provisions,  structural  performance 
shall be established from the design capacity or stiffness by rational engineering  
analysis based on appropriat e theory, related testing if data is available  and  
engineering judgement. Specifically, the design capacity shall be determined from the 
calculated  nominal  capacity  by applying  the following  capacity  reduction  factors:  
(i) For members  ................................ ................................ ..........................  φ = 0.80.  
(ii) For connections  ................................ ................................ .......................  φ = 0.65.  
 
3.4.4  Earthquake  design  
Earthquake design considerations will be as per Kenyan Code of Pactice for Design and 
Construction of Buildings & other Structures in relation to E arthquakes (1973) and Building Code 
2006 as appropriat e 
 
3.4.5  Durability  
3.4.5.1  General  
A structure shall be designed to perform its required functions during its expected life.  
Where steelwork in a structure is to be exposed to a corrosive environment, the steelwork  shall be given 
protection against corrosion. The degree of protection shall  be  determined  after consideration has been 
given to the use of the structure, its maintenance  and  the climatic or other local  conditions.  
 
3.4.5.2  Corrosion  protection  
NOTE: Corrosion protection should comply with AS/NZS 2311  and  AS/NZ S 2312,  as 
appropriate. For further information, see Appendix  C. DKS  2971 : 2022  
xxxviii  © KEBS 2022  – All rights reserved  
  
 
TABLE   1.6  
CAPACITY REDUCTION FACTOR  
 
 
Design capacity   
Clause reference  Capacity  
reduction factor 
(φ) 
(a) Stiffeners:  3.3.8   
Transverse stiffeners ( φc) 3.3.8.1  0.85 
Bearing stiffeners  (φw) 3.3.8.2  0.90 
Shear stiffeners ( φv) 3.3.8.3  0.90 
(b) Members subject to axial tension ( φt) 3.2.1  0.90 
(c) Members subject to bending:  
Section moment capacity — 
for sections with stiffened or partially stiffened 
compression flanges  (φb) 
for sections with unstiffened compression flanges ( φb) 
Member moment  capacity — 
members subject to lateral buckling ( φb) 
members subject to distortional buckling ( φb) 
beams having one flange through -fastened to sheeting 
(channels or Z -sections) ( φb) 
Web design — 
shear ( φv) 
Bearing ( φw)— 
for built -up sections  
for single web channel and channel -sections for 
single web Z -sections  
for single hat sections  
for multiple web deck sections  3.3  
3.3.2   
3.3.2  0.95 
3.3.2  0.90 
 
3.3.3.2   
0.90 
3.3.3.3  0.90 
3.3.3.4  0.90 
 
3.3.4  
0.90 
 
Table 3.3.6.2(A)   
0.75–0.90 
Table 3.3.6.2(B)  0.75–0.90 
Table 3.3.6.2(C)  0.75–0.90 
Table 3.3.6.2(D)  0.75–0.90 
Table 3.3.6.2(E)  0.60–0.90 
(d) Concentrically loaded compression members  (φc) 3.4 0.85 
(e) Combined axial load and bending: 
Compression  (φc) 
Bending ( φb)— 
using Clause 3.3.2  
using Clause 3.3.3.1  3.5 
3.5.1   
 
0.85 
3.5.1   
 0.90 or 0.95  
0.90 
(f) Cylindrical tubular members:  3.6  
 Bending ( φb) 3.6.2  0.95 
 Compression ( φc) 3.6.3  0.85 
(g) Welded  connections:  5.2  
Butt welds — 5.2.2   
tension or compression  5.2.2.1  0.90 
shear  5.2.2.2(a)  0.80 DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  xxxix  
  shear (base metal)  5.2.2.2(b)  0.90 
(continued ) DKS  2971 : 2022  
xl © KEBS 2022  – All rights reserved  
  
 
 
TABLE   1.6   ( continued ) 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
(continued )  
Design capacity   
Clause reference  Capacity  
reduction factor 
(φ) 
Fillet welds — 5.2.3   
longitudinal loading  5.2.3.2  0.55 or 0.60  
transverse loading  5.2.3.3  0.60 
Arc spot welds (puddle welds) — 5.2.4   
shear (welds)  5.2.4.2(a)  0.60 
shear (connected part)  5.2.4.2(b)  0.50 or 0.60  
shear (minimum edge distance)  5.2.4. 3 0.60 or 0.70  
tension  5.2.4.4  0.65 
Arc seam welds — 5.2.5   
shear (welds)  5.2.5.2  0.60 
shear (connected part)  5.2.5.2  0.60 
Flare welds — 5.2.6   
transverse loading  5.2.6.2(a)  0.55 
longitudinal loading  5.2.6.2(b)  0.55 
Resistance welds — 5.2.7   
spot wel ds 5.2.7(a)  0.65 
(h) Bolted  connections:  5.3  
Tearout  5.3.2  0.60 or 0.70  
Net section tension:  5.3.3   
With washers — 5.3.3(a)   
double sh ear connection   0.65 
single shear connection   0.55 
Without washers  5.3.3(b)  0.65 
Bearing  5.3.4  0.60 or 0.65  
Bolts — 5.3.5  
bolt in shear  5.3.5.1  0.80 
bolt in tension  5.3.5.2  0.80 
(i) Screwed  connections:  5.4  
Screwed connections in shear — 5.4.2   
tension in the connected part  5.4.2.2  0.65 
tilting and hole bearing  5.4.2.3  0.5 
tearout  5.4.2.4  0.60 or 0.70  
Screwed  connections in te nsion — 5.4.3   
pull-out of connected parts  5.4.3.1  0.5 
pull-over (pull -through) of connected parts  5.4.3.1  0.5 
 DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  xli 
   
 
TABLE   1.6   ( continued ) 
 
 
Design capacit y  
Clause reference  Capacity  
reduction factor 
(φ) 
(j) Blind riveted  connections:  
Riveted connections in shear — 
tension in the connected part 
tilting and hole bearing  
tearout  5.5 
5.5.2  
5.5.2.2  
5.5.2.3  
5.5.2.4   
 
 
0.65 
0.50 
0.60 or 0.70  
(k) Rupture:  
Shear rupture  
Block shear rupture (bolted connections)   
 
5.6.1  
5.6.3   
 
0.75 
0.65 DKS  2971 : 2022  
xlii © KEBS 2022  – All rights reserved  
  
 
5 SECTION 2 - ELEMENTS  
4.1 Section Properties  
4.1.1  General  
Properties of sections, such as cross -sectional area, second  moment  of area,  section 
modulus, radius of gyration, and centroid, shall be determined in accordance with 
conventiona l methods by division of the section shape into simple  elements,  including  
bends.  
Properties shall be based on nominal dimensions and nominal base steel  thickness  (see 
Clause  1.5.1.6).  
4.1.2  Design  procedures  
4.1.2.1  Full section  properties  
Properties of full, unreduced sections shall be based on the entire simplified shape with the flats and 
bends located along the element mid -lines unless the manufacturing process  warrants consideration 
of a more accurate  method.  
To calculate the stability of members, a  simplifi ed shape  where the  bends are eliminated  and the 
section is represented by straight mid -lines may be used when calculating the following  properties:  
(a) Parameters for distortional buckling (see Appendix  D). 
(b) Location  of shear  centre  (see Paragraph  E1 of Appe ndix E). 
(c) Warping constant (see Paragraph E1 of Appendix  E). 
(d) Monosymmetry  section  constant  (see Paragraph  E2 of Appendix  E). 
 
4.1.2.2   Effective section  properties  
For the design of cold-formed members with slender elements, the area of the sections shall  be 
reduc ed at specified  locations.  
The reduction of the area is required to — 
(a) compensate  for the effects  of shear  lag (see Clause  2.1.3.3);  and 
(b) compensate  for local  instabilities  of elements  in compression  (see Clauses  2.2 to 2.5).  
 
4.1.2.3   Location of reduced  width  
The l ocation of reduced width shall be determined as follows:  
(a) For the design of uniformly compressed stiffened elements, the location of the lost 
portion  shall  be taken  at the middle  of the element  (see Figures  2.2.1  and 
2.4.2(b)).  
(b) For the design of stiffened elements under a stress gradient or where only a part of 
the element is in compression (e.g., the webs), the location of the lost portion shall 
be as shown in Figure  2.2.3.  
(c) For unstiffened elements, under either a stress gradient or uniform compression , the 
lost portion shall be taken at the unstiffened edge as shown in Figure 2.3.1. If the 
unstiffened element is subjected to both tension and compression across its width, 
the lost  portion  may be taken  as specified  in Clause  2.3.2. 
(d) For the design of elements with an edge stiffener, the location of the lost portion shall DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  xliii 
  * be as shown in Figure  2.4.2.  
 
 
4.1.3  Dimensional  limits  
4.1.3.1  Maximum flat -width -to-thickness  ratios  
The maximum overall flat-width -to-thickness ratios ( b/t),  disregarding  intermediate 
stiffeners  and taking t as the nominal  thickness  of the element,  shall  be as follows:  
(a) For a stiffened compression element having one longitudinal edge connected to 
a web  or flange element and the other stiffened  by— 
(i) ................................ ................................ ................................  simple  lip 60; and 
(ii) any other kind of stiffener  when — 
(A) ................................ ................................ ...............................  Is < Ia 60; and 
(B) ................................ ................................ ................................ ...... Is ≥ Ia 90. 
(b) For a stiffened compression element with both  longitudinal  
edges connected to other  stiffened  elements  ................................ ............................  500. 
(c) ................................ ................................ ................................ ..............  For a 
unstiffened  compression  element  ................................ ................................ ..... 60. 
NOTE: Unstiffened  compression elements with b/t ratios greater than 30 and 
stiffened compression elements with b/t ratios greater than 250 are likely to  
develop  noticeable  deformation at the full design load, without affecting the ability 
of the member to carry the design load. Stiffened elements with b/t ratios greater 
than 500 can be used with adequ ate design  capacity  to sustain the design loads. 
However, substantial deformations of such elements usually will invalidate the 
design equations of this Standard.  
4.1.3.2   Flange  curling  
Where the flange of a flexural member is unusually wide and it is desired to limit the maximum amount 
of curling or movement of the flange toward the neutral  axis,  the maximum width (b1) of the 
compression and tension flanges, either stiffened or unstiffened projecting beyond the web for I-beams 
and similar sections or the maximum  half distance  (b1) between webs for box- or U-type beams, shall 
be determined from the following equation : 
….4.1.3.2  
 
where  
tf = thickness of the flange  
d = depth of the section  
 
fav = average design stress in the full, unreduced flange width (see Note  1) DKS  2971 : 2022  
xliv © KEBS 2022  – All rights reserved  
 cf = amount of curling (see Note  2) 
 
NOTES:  
1 Where members are designed by the effective design width procedure, the average 
stress  equals the maximum stress multiplied by the ratio of the effective design width 
to the actual width.  
2 The amount of curling that can be tolerated will vary with different kinds of sections and 
should be established by the designer. Amount of curling in the  order of 5% of the  
depth of the  section is usually not considered  excessive.  
4.1.3.3  Shear lag effects (usually short spans supp orting concentrated  loads)  
Where the span of the beam (l) is less than 30 b1 and the beam carries one concentrated load, or  several  
loads spaced greater  than 2b1, the effective  design width of any  flange, whether in  tension  or 
compression,  shall  be limited  to the values  given  in Table  4.1.3.3.  
For flanges of I -beams and similar sections stiffened by lips at the outer edges, b1 shall be taken as the 
sum of the flange projection beyond the web and the depth of the lip.  
 
TABLE 4 .1.3.3  
MAXIMUM RATIO OF EFFECTIVE  
DESIGN WIDTH TO ACTUAL WIDTH 
FOR SHORT WIDE FLANGE  BEAMS  
 
l/b1 Ratio  l/b
1 Ratio  
30 1.00 14 0.82 
25 0.96 12 0.78 
20 0.91 10 0.73 
18 0.89 8 0.67 
16 0.86 6 0.55 
NOTE:  
l = full span for simple beams; or 
distance between inflection points for continuous beams;  
or 
twice the length of cantilever beams  
4.1.3.4  Maximum web depth -to-thickness  ratio 
The maximum web depth -to-thickness ratio ( d1/tw) of flexural members shall not exceed the 
following:  
(a) ................................ ................................ ................................ ...... For 
unreinforced  webs:  d1/tw ................................ ................................ ........  200. 
(b) For webs with transverse stiffeners complying with Clause  3.3.8.1  
(i) ................................ ................................ .........................  if using  bearing 
stiffeners  only:  d1/tw ................................ ..............................  260; and 
(ii) ................................ ................................ .............................  if using  
bearing stiffeners and intermediate  stiffeners:  d1/tw .....................  300; 
where  
d1 = depth of the flat portion of the web measured along the plane of the web  DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  xlv 
  tw = thickness of web  
Where a web consists of two or more sheets , the ratio d1/tw shall be  calculated  for each sheet . 
 
4.2 Effective Widths Stiffened Elements  
4.2.1  Uniformly compressed stiffened  elements  
4.2.1.1  General  
For uniformly compressed stiffened elements (see Figure 4 .2.1), the effectiv e widths for section or 
member capacity and deflection calculations shall be determined in accordance with  Clauses 4.2.1.2 
and 4.2.1.3  respectively.  
4.2.1.2  Effective width for capacity  calculations  
For determining the section or member capacity, the effective widths ( be) of uniformly 
compressed stiffened  elements  shall  be determined  from   Equation 4.2.1.2(1)   or Equation 
4.2.1.2(2), as appropriate.  
 
For λ ≤ 0.673:  b ed = b             …….4.2.1.2(1)  
For λ > 0.673:  b ed = ρb                                                                                      …….4.2.1.2(2)   
 
where  
 b   = flat width of element excluding radii (see in Figure 4.2.1(a))  
ρ   = effective width factor  
 
            
 ……4.2.1.2(3)  
The slenderness ratio (λ) shall be determined as follows:  
 
               ……4.2.1.2(4)  
 
f*   = design stress in the compression element calculated on the basis of the effecti ve design 
width (see Figure 4.2.1(b))  
fcr = plate elastic buckling stress  
 
                                                                                        ……4.2.1.2(5 ) 
k   = plate buckling coefficient  
 
DKS  2971 : 2022  
xlvi © KEBS 2022  – All rights reserved  
 = 4 for stiffened elements supported by a web  on each longitudinal edge (k values for 
different types of elements are given in the applicable clauses)  
 
ν   = Poisson’s ratio = 0.3  
E = Young’s modulus of elasticity (200 × 103 MPa)  
        t    =  thickness of the uniformly compressed stiffened elements  
 
Alternatively, the plate buckling coefficient (k) for each flat element may be determined from  a  ratio nal  
elastic  buckling  analysis  of  the  whole  section  as  a  plate  assemblage subjected to the longitudinal 
stress distribution in the section prior to buckling  
 
 
 
For determining the nominal section or member capacity of flexural members, the desig n 
stress (f *) shall be taken as follows:  
(a) If the nominal section moment capacity (Ms) is based on initiation of yielding 
as specified in Clause  5.3.2.2, and the initial yielding of the element being 
considered is in compression, then f * shall be equal to fy. If the initial yielding 
of the section is in tension, then f * of the element being considered shall be 
determined on the  basis  of  the effective section at My (moment  causing 
initial yield).  
 
(b) If the nominal section moment capacity (Ms) is based on inelastic reserve 
capacity as specified in Clause 5.3.2.3, then f *  shall be the stress of  the 
element being considered  at Ms. The effective  section  shall  be used  to 
determine  Ms. 
(c) If the nominal member moment capacity (Mb) is based on lateral buckling as 
specified  in Clause 5.3.3.2 or on distortional buckling as specified in  Clause 
5.3.3.3, then  f *  shall  be equal  to fc as described  in Clauses  5.3.3.2  and 
5.3.3.3  in determining  Zc. 
 
For determining the nominal section or member compression capacity, f * shall be taken as 
follows:  
(i) If the nominal section capacity (Ns) of the member in compression is based 
on initiation  of yielding  as specified  in Clause  3.4, then f * shall  be equal  to 
fy. 
(ii) If the nominal member capacity (Nc) of the member in compression is based 
on flexural , torsional or flexural -torsional buckling as specified in Clause 
5.4, then f  * shall  be equal  to fn, as specified  in Clauses  5.4.1 and 5.4.6. DKS 2971 : 2022  
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4.2.1.3  Effective width for deflection  calculations  
For determining the deflection, the effective wid ths (bed) shall  be determined  from Equation 4.2.1.3(1) 
or Equation 4.2.1.3(2), as appropriate.  
For λ ≤ 0.673:  bed = b                                                                                     . . . 4.2.1.3(1) 
For λ > 0.673:  bed = ρb                                                                                   . . . 4.2.1.3(2) 
The effecti ve width factor (ρ) shall be determined by either  of the following  two procedures:  
(a) Procedure I  
A low estimate of effective width may be obtained from Equations 4 .2.1.2(3) and 4.2.1.2(4), 
except that f*d is substituted for f* where f*d is the design compres sive stress in the element 
being considered based on the effective section at the load for which deflections are 
determined  
(b) Procedure II  
For stiffened elements supported by a web  on each  longitudinal edge, an improved 
estimate of the effective width can be obtained by calculating ρ from Equations 4 .2.1.3(3) 
to 4.2.1.3(5), as appropriate.  
 
                   …….4.2.1.2 (3)  
                         …….4.2.1.2 (4 ) 
  
    
                               …….4.2.1.2 (5 ) 
    
                               …….4.2.1.2 (6 ) 
 
4.2.2  Uniformly compres sed stiffened  elements with circular holes  
4.2.2.1  General  
For uniformly compressed stiffened elements with circular holes, the effective widths for section or 
member capacity and deflection calculations shall be determined in accordance with  Clauses 
4.2.2.2 and 4.2.2.3,  respectively.  
 
4.2.2.2  Effective width for capacity  calculations  
For determining the section or member capacity, where 0.50 ≥ dh/b ≥ 0 and b/t ≤ 70, and the 
centre -to-centre spacing of holes >0.5 b and >3dh, the effective width ( be) of uniformly compressed 
stiffened  elements  with circular  holes   shall   be   determined   from   Equation 4 .2.2.1(1) or 
Equation 4.2.2.2(2), as appropriate.  
 
 
 DKS  2971 : 2022  
xlviii © KEBS 2022  – All rights reserved  
  
                                                                                                       …….4.2.2.2 (1 )  
 
                                                                 …….4.2.2.2 (2 )  
  
where d h    is the   diameter   of   holes and    λ   shall   be   calculated   in   accordance   with  
Clause 4 .2.1.2.  
 
The value of be shall not exceed (b − dh). 
 
4.2.2.3  Effective width for deflection  calculations  
For determining the deflection, the effective width ( bed) shall be equal to  be determined in ac corda nce 
with Procedure I of Clause 4 .2.1.3  
 
4.2.3  Stiffened elements with stress  gradient  
4.2.3.1  General  
For stiffened elements with stress gradient (see Figure 2.2.3), the effective widths for  section  or 
member capacity and deflection calculations shall be determine d in accordance with  Clauses 
4.2.3.2 and 4.2.3.3,  respectively.  
 
4.2.3.2  Effective width for capacity  calculations  
For determining the section or member capacity, the effective width ( be1) (see Figure 2.2.3) shall 
be determined from the following:  
 
                     …….4.2.3.2 (1 ) 
The effective width (b e2) (see Figure 2.2.3) sha ll be determined from Equation 4 .2.3.2(2) or  
Equation 4 .2.3.2(3), as appropriate.  
                                                  …….4.2.3.2 (2 )  
where (b e1 + b e2) shall not exceed th e compression portion of the web calculated on the basis of 
effective section.  
           …….4.2.3.2 (3 )
  
Where  
be = effective width  determined in accordance with Clause  4.2.1.2 with    f1 substituted for 
f * and with k determined as follows:  
k             = 4 + 2(1 − ψ)3 + 2(1 − ψ)                                                              . . . 4 .2.3.2(4)  DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  xlix 
  
                                                                                     …….4.2.3.2 (5 ) 
 
  = web stresses cal culated on the basis of the effective section  
(see Figure 2.2.3)  
f1    is compression (+) and f 2    can be either tension (−) or compression (+). In case f1   
and f 2   are both compression, f 1   shall be greater than or equal to f 2    
 
4.2.3.3  Effective width f or deflection  calculations  
For determining the deflection, effective widths ( be1) and ( be2) shall be determined in accordance with 
Clause 4 .2.3.2 except that f* d1 and f* d2 are substituted for f*1 and f*2. Calculations shall be based on 
the effective sectio n for the load for which deflections are determined . 
 
 
 
 
 
DKS  2971 : 2022  
l © KEBS 2022  – All rights reserved  
 
 
 
4.2.4  Channel -section webs with holes and with stress  gradient  
4.2.4.1  General  
The calculation of capacity and deflection for channel -section webs with holes and with stress  
gradient shall be applicable within  the following  limits:  
(a) dwh/d1 < 0.7 . . . 4.2.4.1  
where  
dwh = depth of the web hole  
d1 = depth of the flat portion of the web measured along the plane of the web 
(b) d1/t ≤ 200. 
(b) Holes centred at mid-depth of the web.  
(c) Clear  distance  between  holes  is greater  than or equal  to 450 mm. 
(d) Non-circular holes corner radii greater than or equal to 2 t. 
(e) Non-circular holes with dwh ≤ 65 mm and b ≤ 115 mm, where b is the length of the  
web hole.  
(f) Circular hole diameters less than or equal to 150  mm. 
(g) dwh > 15 mm. DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  li 
   
4.2.4.2  Capacity  calculations  
When dwh/d1 < 0.38, the effective widths ( b1) and ( b2) shall be  determined  in accordance  with 
Clause  4.2.3 by assuming  no hole exists  in the web.  
When dwh/d1 ≥ 0.38, the effective width shall be determined in accordance with Clause 4.3.1 
assumi ng the compression portion of the web consists of an unstiffened element adjacent to the 
hole with f * = f1 as shown in Figure  2.3.2.  
 
4.2.4.3  Deflection  calculations  
The effective widths shall be determined in accordance with Clause 4.2.3 by assuming no  hole 
exists in the  web.  
 
4.3 Effective Widths of unsiffened Elements  
4.3.1  Uniformly compressed unstiffened  elements  
4.3.1.1  General  
For uniformly compressed unstiffened elements (see Figure 2.3.1), the effective widths for 
section or member capacity and deflection calculations shall be determined in accordance with  
Clauses 4.3.1.2 and 4.3.1.3,  respectively.  
4.3.1.2  Effective width for capacity  calculations  
For determining the section or member capacity, the effective widths ( be) of uniformly 
compressed unstiffened elements shall be determi ned in accordance  with Clause  4.2.1.2 with  the 
exception  that k shall  be taken  as 0.43 and b shall  be as shown  in Figure  2.3.1.  
4.3.1.3  Effective width for deflection  calculations  
For determining the deflection, the effective widths ( be) shall be determined in acc ordance with 
Procedure I except that f*d is substituted with f* and k = 0.43.  
 
 
 
 
 
 
 
 
 
DKS  2971 : 2022  
lii © KEBS 2022  – All rights reserved  
  
4.3.2  Unstiffened elements and edge stiffeners with stress  gradient  
4.3.2.1  General  
For unstiffened elements and edge stiffeners with stress gradient, the effective widths for secti on 
or member capacity and deflection calculations shall be determined in accordance with  Clauses 
4.3.2.2 and 4.3.2.3,  respectively.  
4.3.2.2  Effective width for capacity  calculations  
For determining the section  or member  capacity, the effective widths  (be) measured  from the 
supported edge of unstiffened compression elements and edge stiffeners with  stress gradient 
shall be determined in accordance with Clause 4 .2.1.2 with f=f1 and with k=p determined in 
accordance with this clause.  
 
f1, f2 = stresses shown in Figure s 2.3.2(A) and (B) calculated on the basis of the gross section 
where f 1is compression (+) and f 2 can be either tension (−) or compression ( +).  In the case 
where f 1 and f 2 are both in compression  
f*1/f*2                     …….4.2.3.2 (5 )  * *    
The effective width factor (ρ) and the plate buckling coefficient ( k) shall be determined as 
follows:  
(a) For unstiffened elements with stress gradient causing compression at both 
longitudinal edges of the unstiffened element both in compression, as shown in Figure 
2.3.2(A).  
ρ shall be determined using Equation 4.2.1.2(3) and λ shal l be determined 
using Equatio n 4.2.1.2(4). The buckling coefficient ( k) in Equation 4 .2.1.2(5) 
shall be determined as follows:  
(i) Where the stress decreases toward the unstiffened edge of the 
element as shown in  Figure  2.3.2(A)(a),  k shall  be calculated  as 
follows:  
 
         
             ……4.3.2.2(2 )
 
(ii) Where the stress increases toward the unstiffened edge of the 
element as  shown  in Figure  2.3.2(A)(b),  k shall  be calculated  as 
follows:  
 
         
                                . . . 4.3.2.2(3)       
 DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  liii 
   
(b) For unstiffened elements with str ess gradient causing compression at one 
longitudinal edge  and tension  at the other  longitudinal  edge  of the 
unstiffened  element:  
(i) For f*1 in compression at the unsupported edge and  f*2 in tension 
as shown in Figure 2.3.2(B)(a)  ρ shall be calculated as follo ws 
 
 
               ……4.3.2.2(4)  
λ shall be determined using Equation  4.2.1.2(4)  
 
                                             ……4.3.2.2(5)        
 
 
(ii) For f*1 in compression at the unsupported edge and  f*2 
in tension a s shown in Figure 2.3.2(B)(b)  ρ shall b e 
calculated as follows;  
                 
   
              ……4.3.2.2(6 )  
λ shal l be determined using Equation 4 .2.1.2(4)  
 
                                                                         ……4.3.2.2(7 ) 
 
 
 
Alternatively, the plate buckling coefficie nt (k) in Equation 2.3.2.2(5) may be determined using 
Equation 2.3.2.2(8) for plain channels bent in the plane of symmetry with the unsupported edge of 
the unstiffened element in compression as follows:  
k = 0.1451( b2/b1) + 1.256                                                     . . . 4.3.2.2(8)  
 
where  
b2 = width of the unstiffened element  
b1 = width of the stiffened element  
For other types of sections , k in Equations  4.3.2.2(2), 4.3.2.2(3), 4 .3.2.2(5) and 4.3.2.2(7 ) for 
the unstiffened element and k for ea ch remaining flat element of the section may be 
determined from a rational elastic buckling analysis of the whole section as a plate 
assemblage subjected to the longitudinal stress distribution in the section prior  to buckling.  
In calculating the effective  section modulus (Ze) in Clause 5.3.2.2 or in Clause 5.3.3.2, the 
extreme compression fibre in Figures 2.3.2(A)(b) and 2.3.2(B)(a) is taken as the edge of the 
effective section (closer to the unsupported  edge).  
In calculating the effective section modulus (Ze) in Clause  5.3.2.2, the extreme tension fibre  in 
DKS  2971 : 2022  
liv © KEBS 2022  – All rights reserved  
 Figure 2.3.2(B)(b) is taken as the edge of the effective section (closer to the unsupported 
edge).  
 
 
 
4.3.2.3  Effective width for deflection  calculations  
For determining the deflection, the effective widths( be) of unstiffened elements and edge stiffeners 
with stress gradient shal be determined in accordance with Clause 4.3.2.2 except that f*d1 and f*d2 
are substituted for f*1 and f*2 
Calculations shall be based on effective section for thee load for which defle ctions are determined.  
 
4.4 Effective Wi dths of Uniformly Compressed El ements with an Edge Stiffener  
4.4.1  General  
For uniformly compressed elements with an edge stiffener, the effective widths  for section  or 
member capacity and deflection calculations shall be determined in accordance with Clauses 4 .4.2 
and 4.4.3 respectively.  
 DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  lv 
  4.4.2  Effective width for capacity  calculations  
For determining the section or member capacity, the effective widths ( be) of uniformly 
compressed elements with an edge stiffener shall be determine d as follows:  
(a)  
 
Ia    = 0 (no edge stiffener is required)  
= adequate second moment of area of the stiffener, so that each component 
element behaves as a stiffened element  
be   = b                                                                                         ……4.4.2(1)  
b1 = b 2 = b/2 (see Figure 2.4.2 )                                                   ……4 .4.2(2 )  
ds   =  d se      (for simple lip stiffener)                                           …….4.4.2(3)  
As = A se (for other stiffener shapes)                                                 …4.4.2(4)  
 
(b)  
 
         (see Figure 2.4.2)                 
             (see Figure 2.4.2)                 
 
            for other stiffener shapes   
 
 
 
 
 
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lvi © KEBS 2022  – All rights reserved  
  
 
 
If Is  is greater than or equal to Ia, then Is  is equal to Ia  in Equation 4.4.2(5), (7), (8) and 
Table 2.4.2.
 
 
 
 
 
be   shall  be  calculate d  in  accordanc e  with  Clau se 4.2.1.2,  where  k shall  be  as  given  in 
Table 2.4.2.
 
 
 
 
 
 DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  lvii 
  
 
  
4.4.3  Effective width for deflection  calculations  
For determining the deflection, the effective widths ( be) shall be determined in accordance with Clause 2.4.2, 
except that f*d is substituted for f*. 
 
4.5 Effective Widths of uniformly compressed elements with one interm ediate stiffener  
4.5.1  General  
For uniformly compressed elements with an intermediate stiffener (see Figure 2.5.2), the effective widths 
for section or member capacity and deflection calculations shall be determined in accordance with 
Clauses 2.5.2 and 2.5.3  respectively.  
 
4.5.2  Effective width for capacity  calculations  
For determining the section or member capacity, the effective widths ( be) of uniformly compressed DKS  2971 : 2022  
lviii © KEBS 2022  – All rights reserved  
 elements with one intermediate stiffener shall be determined as follows ; 
(a)  
 
Ia        = 0 (no intermediate stiffene r is required) 
= a d e q u a t e  second  moment  of area of the stiffener , so that  each  comp onent el ement 
behaves as a stiffened element 
          be       = b                                                                                                               . . . 4.5.2(1) 
b     = f l a t  width of element excluding corners or bends (see Figure 2.5.2) 
As     = r e d u c e d  area of the stiffe ner 
=  Ase                                                                                                                                                                                          . . . 4.5.2(2) 
Ase   = e f f e c t i v e  area of the stiffener 
 
As shall be used in calculating the overall effective section properties. The centroid of the stiffener 
shall be co nsidered located at the centroid of the full area of the stiffener, and the second moment 
of area of the stiffener about its own centroidal axis shall be that of the full  
section of the stiffener.  
(b)  
 
          
n   = exponent  
 
 
k   = plate buckling coefficient  
 
 
DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  lix 
  
 
 
 
 
 
 
 
 
 
 
 
 
 
4.5.3  Effective width for deflection  calculations  
For determining the deflection, the effective widths ( be) shall be determined in accordance with Clause 2.5.2, 
except that f*d is substituted for f*. 
 
DKS  2971 : 2022  
lx © KEBS 2022  – All rights reserved  
 4.6 Effective widths of uniformly compressed stiffened elements with multiple intermediate 
stiffeners.  
4.6.1  Determination of effective  width  
The effective width of the element shall be determined as follows:  
 
 
 
 
 
 
 
 
where  
 
be   =  effective  wid th  of  the  element,  located  at  the  end  of  the  element  including stiffeners (see Figure 
2.6.1(A))  
 
ρ   = effective width factor  
 
 
 
 
 
 
 
bo  =  total flat width of the stiffened element (see Figure 2.6.1(B))  
 
Ag =  gross area of the element including stiffeners  
 
t    =  thickness of element  
 
The plate buckling coefficient (k) shall be determined from t he minimum of Rkd and kloc, determined in accordance with 
Clause 2.6.2 or Clause 2.6.3 as appropriate, where  
 
 
 
 
 
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4.6.2  Specific case: ‘n’ identical stiffeners, equally  spaced  
4.6.2.1  Capacity  calculation  
 
                                                                                       …….4.6.2.1(1)    
                                                                   …….4.6.2.1( 2)   
                                                                                 …….4.6.2.1(3 )   
                                                                      …….4.6.2.1( 4)   
                                                                                             …….4.6.2.1(5 )   
 
 
 
 
  where  DKS  2971 : 2022  
lxii © KEBS 2022  – All rights reserved  
 β = coefficient  
γ = importance  factor  
δ = coefficient  
Isp = second moment of area of  a stiffener about the centre -line of  the flat portion of  
the element.  The radii which  connect  the stiffener  to the flat may be included  
bo = total flat width of the stiffened element (see Figure 2.6.1(B))  
As = gross area of the stiffener  
 
If lbr < βba then lbr/bo shall be permitted to be substituted for β to account  for  increased 
capacity due to bracing, where lbr is the unsupported length of bracing or other restraint that 
restricts distortional buckling of the element.  
 
4.6.2.2  Deflection  calculation  
The effective width ( be) used in calculating deflection shall be determined in accordanance with clause 
2.6.2.1, except that f*d shall be substituted for f* where f*d is the design compressive stress in th 
element being considered based on the effective sect ion at the load for which deflections are being 
determinedDKS 2971 : 2022  
© KEBS 2022 – All rights reserved  lxiii 
   
 
4.6.3  General case: Arbitrary stiffener size, location and  number  
4.6.3.1  Capacity  calculation  
 
                                                                                 ……...4.6.3.1(1)  
 
                                                          ……...4.6.3.1(2 ) 
                                                                    ……...4.6.3.1( 3) 
                                                                             ……...4.6.3.1( 4) 
                                                                           ……...4.6.3.1( 5) 
                                                                                        ……...4.6.3.1(6 )  
 
where  
bp = greatest sub-element flat width (see Figure  2.6.1(B))  
ωi = coefficient  
Ci = horizontal distance from the edge of the element to the centre -line(s) of the 
stiffener(s) (see Figure  2.6.1(B))  
i = index for stiffener  ‘i’ 
If lbr < βbo then lbr/bo shall be permitted to be substituted for β to account for increased 
capacity due to bracing.  
 
4.6.3.2  Deflection  calculation  
The effective width ( be) used in calculating deflection shall be determin ed in accordanance with clause 
4.6.3.1, except that f*d shall be substituted for f* where f*d is the design compressive stress in th 
element being considered based on the effective section at the load for which deflections are being 
determined . 
 DKS  2971 : 2022  
lxiv © KEBS 2022  – All rights reserved  
  
4.7 Effective widths of uniformly compressed edge -stiffened elements with intermediate stiffeners  
The effective width ( be) of uniformly compressed edge -stiffened elements with intermediate 
stiffeners shall be determined as follows:  
(a) If b2/t ≤ S/3, the element is fully effective and no local buckling reductions are required.  
(b) If b2/t > S/3, the plate buckling coefficient ( k) shall be determined in accor dance with this 
Clause but with b2 replacing b in all expressions,  
where  
b2 = total flat width of the edge -stiffened element (see Figure 2.5.2)  
S = slenderness factor  
If k, calculated in accordance with Clause 2.4.2, is less than 4 ( k < 4), the intermediat e stiffeners 
shall be ignored and the provisions of Clause 2.4.2 shall be followed for the calculation of be. 
If k, calculated in accordance with Clause 2.4.2, is equal to 4 ( k = 4), be  of  the  edge -  
stiffened element shall be calculated in accordance with Clause 4 .6, where the modification 
factor  for the distortional  plate  buckling  coefficient  shall  be less than or equal  to 1. 
 
 
4.8 Arched compression Elements  
A circular or parabolic arch-shaped compression element, stiffened at both ends, shall be consider ed self -
stiffened and fully effective if the second moment of area  of  the arch  about its own centroidal axis parallel to 
the base is not less than the minimum second moment of area (Imin.) specified in  Clause 2.5. For the purpose of  
this Clause, b  shall be taken as  half  the length of arch and the ratio b/t shall not exceed 60. For other 
conditions, the geometrical properties  of sections  shall  be determined  by load tests  in accordance  with 
Section  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  lxv 
  5 SECTION 3 – MEMBERS  
5.1 General  
Section properties used for the determination of structural performance, moment capacity of beams or capacity of 
axial members in compression shall be those calculated in accordance with Section 2.  
Both full and effective section properties, where applicable , shall be required. Full section properties shall be used 
for the determination of buckling moments or stresses. Effective section properties shall be used for the 
determination of section and member capacities.  
 
5.2 Members subject to axial tension  
5.2.1  Design for axial tension  
A member subject to a design axial tensile force ( N*) shall satisfy — 
N* ≤ φtNt . . . 5.2.1 
where  
φt = capacity reduction factor for members in tension (see Table 1.6)  
Nt = nominal section capacity of the member in  tension  determined in  accordance  
with Clause  3.2.2  
 
5.2.2  Nominal section  capacity  
The nominal section capacity of a  member in tension shall be taken as the lesser of — 
Nt =   Ag fy; and . . . 5.2.2(1)  
Nt =  0.85ktAn fu . . . 5.2.2(2)  
where  
Ag = gross area of the cross -section  
fy = yield stress used in design  
kt = correction factor for distribution  of forces   determined  in  accordance  with  Clause  
5.2.3.2  
An = net area of the cross -section, obtained by deducting from the gross area of the 
cross -section, the sectional area of all penetrations and holes, including  
fastener  holes  
fu = tensile strength used in design  
 
5.2.3  Distr ibution of forces  
5.2.3.1  End connections providing uniform force  distribution  
Where for design purposes it is assumed that the tensile force is distributed uniformly to a tension 
member, the end connections shall satisfy both the following:  
(a) The connections shall be made to each part of the member and shall be 
symmetrically placed about the centroidal axis of the member.  
(b) Each part of the connection shall be proportioned to transmit at least the 
maximum design force carried by the connected part of the member.  
For c onnections satisfying these requirements, the value of kt shall be taken as 1.0.  DKS  2971 : 2022  
lxvi © KEBS 2022  – All rights reserved  
  
 
5.2.3.2  End connections providing non -uniform force  distribution  
If the end connections of a tension member do not comply with Clause 3.2.3.1, then the member 
shall be designed to comply with Clause 3.5 using kt = 1.0, except that Clause 3.2.2 may be used for 
the following  members:  
(a) Eccentrically connected angles and channels Eccentrically connected angles 
and channels may be designed in accordance with Clause 3.2.2, using  the  
appropriate  value of kt given in Table  3.2. 
(b) Channels connected by  both flanges only  A  symmetrical rolled or  built-up 
member of  channel -section connected by both flanges only  may be designed 
in accordance  with Clause  3.2.2  using  a value  of kt equal  to 0.85, provided — 
(i) the length between the first and last rows of fasteners  in  the  connection,  
or when the member is welded, the length of longitudinal weld provided 
to each  side of the connected  flanges  is not less than the depth  of the 
member;  and 
(ii) each flange connection is proportioned to transmit at least half of the 
maximum design force carried by the connected  member.  DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  lxvii 
  
 
5.3 Members subject to bending  
5.3.1  Bending  moment  
The design bending moment ( M*) of a flexural member shall satisfy the following:  
(a) M* ≤ φbMs . . . 5.3.1(1)  
(b) M* ≤ φbMb . . . 5.3.1(2)  
 
where  
φb = capacity reduction factor for bending (see Table  1.6) 
Ms = nominal section moment capacity calculated in accordance with Clause 5.3.2 
Mb = nominal member moment capacity calculated in accordance wit h Clause 5.3.3 
5.3.2  Nominal section moment  capacity  
5.3.2.1  General  
The nominal section moment capacity (Ms) shall be calculated either on  the  basis  of initiation of 
yielding in  the effective section specified in  Clause 5.3.2.2 or  on the  basis of  the inelastic 
reserve capacity specified in Clause  5.3.2.3.  
 DKS  2971 : 2022  
lxviii © KEBS 2022  – All rights reserved  
 5.3.2.2  Based on initiation of yielding  
The nominal section moment capacity ( Ms) shall be determined as follows:  
Ms = Ze fy . . 5.3.2.2  
where Ze is the effective section modulus calculated with the extreme  compression or 
tension  fibre at fy. 
5.3.2.3  Based on inelastic reserve  capacity  
The inelastic flexural reserve capacity may be used if the following conditions are met:  
(a) The member is not subject to twisting or to lateral, torsional, distortional or 
flexural - torsional  bucklin g. 
(b) The effect  of cold-forming  is not included  in determining  the yield  stress  (fy). 
(c) For Item (i) (below), the ratio of the  depth of the  compressed portion of  the web 
(dw) to its thickness  (tw) does  not exceed  the slenderness  ratio (λ1). 
(d) The design shear force ( V*) does not exceed 0.35 fy times the web area (d1tw) for Item (i) 
(below) and ( bt) for Item (ii) (below).  
(e) The angle between any web and a perpendicular  to the flange does not exceed 
30°.    
 The nominal section moment capacit y (Ms) shall not exceed either 1.25Ze fy, where Ze fy 
shall be determined in accordance with Clause 3.3.2.2 or that causing a maximum 
compression strain of Cyey, 
where  
Cy = compression strain factor  
ey = yield strain  
 
                                                                                                     ……5.3.2.3(1)  
E = Young’s modulus of elasticity (200 × 103 MPa)  
NOTE: There is no limit for the maximum tensile strain.  
The compression strain factor ( Cy) shall be determined as follows:  
(i)      For stiffened compression elements without intermediate stiffeners:  
           ……5.3.2.3(2 ) 
                         ……5.3.2 .3(3) 
                                                                         ……5.3.2.3(4 )  
                                                                                             ……5.3.2.3(5 ) 
                                                                                         ……5.3.2.3(6 ) 
 
DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  lxix 
   
(ii)     For unstiff ened compression elements:  
(A)    Under stress gradien t causi ng compress ion at one longitudinal edge and tension at the other 
longitudinal edge of the unstiffe ned element.  
For λ ≤ λ3:          Cy = 3  
For λ3  < λ ≤ λ4: Cy = 3 − 2[(λ − λ3)/(λ4  − λ3)]                                 . . . 5.3.2.3(7)  
For λ ≥ λ4:          Cy = 1 
λ3 = 0.43  
λ4  = 0.673(1 − ψ)                                                      . . . 5.3.2.3(8)  
where λ and ψ shall be determined in accordance with Clause 4.3.2.2  
(B)    Under stress gradient  causing  comp ression  at both longitudinal edges  of the unstiffe ned 
element.  
Cy = 1 
 
(iii)  For multiple -stiffened compression  elements  and compression  elements  with edge  stiffeners:   
Cy = 1 
If applicable, effective design widths shall be used in  calculating  section  properties .  Ms shall 
be calculated considering equilibrium of stresses, assuming an ideally elastic -plastic stress -
strain curve that is the same in tension as in compression, small deformation and that plane 
sections remain plane during bending. Combined bending and web  crippling  shall be in  
accordance with Clause  5.3.7. 
 
5.3.3  Nominal member moment  capacity  
5.3.3.1  General  
The nominal member moment capacity (Mb) shall be the lesser of Ms and the  values  calculated in 
accordance with Clauses 5.3.3.2  and 5.3.3.3. Clause 5.3.3.4  may  be  
used inlieuofClause 3.3.3.2 where appropriate.  
 
5.3.3.2  Members subject to lateral  buckling  
5.3.3.2.1  Open section  members  
This Clause does not apply to multiple -web deck, U-box and curved or arch members subject 
to lateral buckling. It does not apply to members whose cross -sections distort laterally, such 
as those otherwise laterally stable members whose unbraced compression flanges buckle  
laterally.  
For channel - and Z-purlins in which  the tension flange is attached to sheeting , see  Clause  
5.3.3.4.  
The nominal me mber moment capacity ( Mb) of the laterally unbraced segments of singly -, doubly - 
and point -symmetric sections subjected to lateral buckling shall be calculated as follows:  
 
                                                                                                                 ……5.3.3.2(1 ) 
 
Where   
 
Zc      = effective section modulus calculated at a stress fc in the extreme compression fibre  
fc        = M c/Zf                                                                                                     . . . 5 .3.3.2(2)  
  Mc    =  critical moment  
 DKS  2971 : 2022  
lxx © KEBS 2022  – All rights reserved  
  The critical moment (Mc) shall be calculated as follows:  
                                                                          ……5.3.3.2(3 ) 
                                              ……5.3.3. 2(4) 
                                                             ……5.3.3.2(5 ) 
where  
 λb   = non -dimensional slenderness ratio used to determine Mc for members subject to lateral buckling  
                                                                                                                         ……5.3.3.2( 6)  
My    = moment causing initial yield at the extreme compression fiber of the full section  
                                                                                                                              ……5.3.3.2(7 )   
Mo    = elastic buckling moment  
 
(a) For    singly -,   doubly -   and    point -symmetric   sections (see   Figures 1.5(a ), (b) and (c)   For singly -
symmetric sections, x -axis is the axis of symmetry oriented such  that the shear centre has a negative x -
coordinate and yo is zero.  
(i) For singly -symmetric sections  bent  about  the  symmetry  axis,  for  doubly - symmetric sections bent about 
the x -axis and for Z -sections bent about an axis perpendicular to the web, Mo  shall be calculated as follows:  
 
                                                                                                   ……5.3.3.2(8 )   
where  
  
Cb     = coefficient  depending on moment distribution in the laterally u nbraced segment  
 
                                                                            ……5.3.3.2( 9)   
 
 Mmax. = absolute value of the maximum moment in the unbraced segment  
 
 M3        = absolute  value of the moment at quarter point of the unbraced segment  
 
DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  lxxi 
   M4        = absolu te   value   of   the   moment at mid -point of the unbraced segment  
 
 M5        = absolute value of the moment at three -quarter point of the unbraced 
segment  
Cb   is permitted to be taken as unity for all cases.  For cantilevers  or overhangs 
where the free end is unbraced, Cb shall be taken as unity.  
Alternatively, Cb may be computed from Table 3.3.3.2.  
A    = area of the full cross -section  
ro1     = polar radius of gyration of the cross -section about the shear centre  
 
                                                      ……5.3.3.2(10 )   
 
rx, ry       = radii of gyration of the cross -section about the x - and y-axes, respectively  
xo, yo      = coordinates of the shear centre of the cross -section  
 
foy     = elastic buckling stress in an axially loaded compression member for flexural 
buckling about the y -axis 
 
                                                                   ……5.3.3.2(1 1)   
foz     = elastic buckling stress in an axially loaded compressio n member for torsional 
buckling  
 
                                                          ……5.3.3.2(12 )     
 
lex, ley lez = effective lengths for buckling about the x - and y - axes, and for twisting, 
respectively  
G   = shear modulus of elasticity (80 × 10 3 MPa)  
J    = torsion constant for a cross -section  
Iw = warping constant for a cross -section  
 
The value of Iy to be used in the calculation of foy for  Z-sections shall be  the  value 
calculated about the inclined minor principal axis. Alternatively, for Z-sections restrained by 
sheeting against lateral movement effectively  bracing the tension flange in accordance with 
Clause 4.3.2.1, the values of  Iy  and  Iw shall be those for an equivalent channel where the 
direction of the flange of the Z-section attached to the sheeting is reversed.  
For a channel - or Z-section that is intermediately braced in accordance with Clause 4.3.2.3, 
DKS  2971 : 2022  
lxxii © KEBS 2022  – All rights reserved  
 the bracing interval (a) shall be used instead of the lengths ( ley,  lez) in the calculation of Mo. 
Values of the bracing interva l (a) and coefficient ( Cb) for uniformly distributed loads, applied 
within the span of intermediately  braced  simply  supported  beams, are given in Table  
3.3.3.2.  
Alternatively, Mo can be calculated using Equation 3.3.3.2(17) for point - symmetric Z -sections.  
 
(ii)  For singly -symmetric sections bent about the centroidal axis perpendicular to the symmetry 
axis, Mo shall be calculated as follows  
                       ……5.3.3.2(13 )    
 Where  
fox     = elastic buckling stress in an axially loaded compression me mber for flexural buckling 
about the x -axis 
 
                                                                                           ……5.3.3.2(14)  
CTF = coefficient for unequal end moment  
 
                                                                                     ……5.3.3.2(15 ) 
M1 is the smaller and M2 the lar ger bending moment at the ends of the unbraced  length. The  
ratio of end moments (M1/M2) is positive  if M1   and  M2   have  the  same  sign (reverse 
curvature bending) and negative if th ey are of opposite  sign (sing le  curvature bending). If the 
bending moment at any point within an unbraced length is larger than that at both ends of this 
length, CTF shall be taken as unity.  
 
Cs  = coefficient  
= +1, for moment causing compression on the shear centre side of the centroid (see Figure E1 
of Appendix E)  
= −1, for moment causing tension on the shear centre side of the centroid (see Figure E1 of 
Appendix E)  
 
βy =  monosymmetry  section  constant  about  the  y -axis  (see  Paragraph E2 of Appendi x E) 
 
                                                              ……5.3.3.2(16 ) 
 
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© KEBS 2022 – All rights reserved  lxxiii 
  Iy       = second moment of area of the cross -section about the y -axis 
x, y = principal axes of the cross -section  
 
(b) For point -symmetric Z -sections for point -symmetric Z -sections, Mo shall   be calculated as 
follows:  
 
                                                                              ……5.3.3.2(1 7) 
Where  
Iyc  = second moment of area of the compression portion  of the section about the centroidal axis 
of the full section parallel to the web, using the full unreduced section  
l      = unbraced length of the member  
Alternatively, the value of Mo may be determined by a rational flexural -torsional buckling 
analysis.  
 
 
 
 
 
 
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lxxiv © KEBS 2022  – All rights reserved  
 5.3.3.2.2  Closed box members  
For closed box members, the nominal member moment capacity ( Mb) shall be determined as follows:  
 
(a) If the unbraced length of the member is less than or equal to lu, Mb  shall be determined in accordance 
with Cl ause 5 .3.3.2.1,  
 
where 
lu    = limit  of unbraced length by which lateral -torsional buckling is not considered  
 
                                                     ……5.3.3.2(17)  
 
(b)  If the laterally unbraced length of a member is greater than lu, Mb shall be determined i n 
accordance with Clause 3.3.3.2.1, where the elastic buckling moment (Mo) shall be calculated as follows:  
 
                                                                                ……5.3.3.2(18 ) 
Where  
l    = laterally unbraced length of the member  
 
5.3.3.3  Members subject to distortional  buckling  
The nominal member moment capacity (Mb) of sections  subject  to  distortional  buckling shall be 
calculated as follows:  
 
                                                                                              ……5.3.3.3(1 ) 
 
The following cases, as appropriate, shall be considered:  
 
(a)  Where distortional buckling involves rotation of a flange and lip about the flange/web junction of a 
channel - or Z-section   Zc  is the full section  modulus except that when k  as given by Equation D3(2) is 
negative then Zc  is the effective section modulus  
calculated  at  a  stress  (fc)  in  the  extreme  compression  fibre  using  k = 4.0  for  the compressive 
flange in Equation 4.2.1.2(4)  and igno ring Clause 4 .4.1, where fc shall be calculated as follows  
 
fc = M c/Zf                                                                                                         ….5.3.3.3(2)  
 
where  
  
Mc    = critical moment  
 
Zf       = full section modulus  
 
The critical moment (M c) shall be calculated as follows:  
 
 
                                                                       ……5.3.3.3(3 )  
 
                                                ……5.3.3.3( 4) 
DKS 2971 : 2022  
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  (b)  Where distortio nal buckling involves transverse bending of a vertical web with lateral displacement   
of the   compression   flange   Zc    is   the   effective   section   modulus calculated at a stress (fc) in the 
extreme compression fibre, where fc   shall  be calculat ed using Equation 5 .3.3.3(2).  
 
The critical moment (Mc) shall be calculated as follows:  
 
                                                    ……5.3.3.3( 5)  
                                                    ……5.3.3.3(6 ) 
                                                           ……5.3.3.3( 7) 
 
Where  
 
My    = moment causing initial yield at the extreme compression fibre of the full section  
 
λd       = non-dimensional slenderness used to determine Mc for member subject to distortional buckling  
 
 
                                                                                                         ……5.3.3.3( 8) 
Mod = elastic buckling moment in the distortional mode  
 
                                                                                                            ……5.3.3.3(9 ) 
 
fod    = elastic distortional buckling stress  
 
NOTE: f od may be calculated using the appropriate equations given in Appendix D or a rational elastic buckling analysis.  
 
5.3.3.4  Beams having one flange through -fastened to sheeting  
The nominal member moment capacity (Mb) of a channel - or Z-section loaded in a plane parallel to the 
web, with the tension flange attached to sheeting  and with compression  flange laterally unbraced, shall 
be calculated as follows:  
Mb = RZ e fy    . . . 5.3.3.4  
where R is the reduction factor.  
The reduction factor ( R) shall be taken as follows:  
(a) Uplift loading For continu ous lapped purlins with three or more  spans  using Z -
sections, and simple spans using channel - and Z-sections  with cyclone washers, 
the  R factor shall be as follows:  
(i) ................................ ................................ ................................ ....... No bridging
 ................................ ................................ ................................ ...............  0.75.  
(ii) ................................ ................................ ................................ ....... One row of 
bridging  in end and interior  spans  ................................ ...........................  0.85.  
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 (iii) Two rows  of bridgin g in end span  and one or more  rows  
in  interior spans of  continuous  lapped  purlins  ................................ ................  0.95.  
(iv) ................................ ................................ ................................ ...... Two rows of 
bridging in  simple  span  ................................ ................................ ..........  1.00.  
The combined bending and shear at the end of the lap shall be considered for the case with 
two rows of bridging.  
For double  spans using Z -section, the R factor shall be as follows:  
(A) ................................ ................................ ................................ ....... No bridging
 ................................ ................................ ................................ ...............  0.60.  
(B) ................................ ................................ ................................ ....... One row of 
bridging  per span  ................................ ................................ .....................  0.70.  
(C)................................ ................................ ................................ ....... Two rows of 
bridging  per span  ................................ ................................ ....................  0.80.  
 
NOTE: For simple spans without cyclone washers, the values recommended in the AISI 
Specification should be u sed. 
(b) Downwards loading For continuous lapped purlins with three or more spans using Z-
section, without bridging or any other configuration, the R factor shall be equal to 
0.85.  
The combined bending and shear at the end of the lap need not be  considered  
separately for this case.  
The reduction factor ( R) shall be limited to roof and wall systems complying with the 
following:  
(i) Member  depth  shall  be less than or equal  to 300 mm. 
(ii) Flanges shall be edge -stiffened compression elements with the lip perpendicular  to   
the stiffened  flanges.  
(iii) 75 < depth/thickness < 135. 
(iv) 2.3 < depth/flange width < 3.2. 
(v) 25 < flat width/thickness of flange < 44. 
(vi) For continuous span systems, the total lap length at each interior support in each 
direction (distance between centre -line of bolts at each end of lap) shall be not less 
than— 
13% of span for triple spans;  and 15% of span for double spans, such that the support 
bolts are located at the  centre  of the lap 
(vii) Member span length shall be not greater than 10.5 m.  
(viii) For continuous span systems,  the longest member span shall be not more than 20% 
greater than the shortest  span  
(ix) Cleat plates shall be used at the supports.  
(x) Roof or wall panels shall be steel sheets, minimum of 0.42 mm base metal thickness, 
having a minimum rib depth of 27 mm, at a maximum spacing of 200 mm on centres 
and attached in such a manner as to effectively inhibit relative movement between 
the panel and purlin  flange.  
(xi) Insulation  shall  not be used  between  the roof sheeting  and purlins.  DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  lxxvii  
  (xii) Fastener type shall be minimum No. 12 self-drilling or  self-tapping sheet  metal 
screws for triple and double  spans, and No.  12 screws  with load-spreading washers 
for simple  spans.  Side lap fasteners  shall  be used  between  the sheets.  
(xiii) Screws shall be crest -fastened.   
(xiv) Fasteners shall be located at every crest.  
(xv) Bridging shall be of a type  that effectively prevents lateral and torsional deformations 
at support  points.  
If variables fall outside any of the requirements in Items (i) to (xv), full -scale tests shall be 
made in accordance with Section 6, or another  rational analysis procedure shall be applied .  In 
any case, it is permitted  to perform tests, in accordance  with Section 6, as an  alternative to  the 
procedure described in this Clause.  
 
5.3.3.5  Beams having one flange fastened to a standing seam roof or cli p-fixed deck  system  
The nominal section moment capacity (Ms) of a channel - or Z-section, added in a plane parallel  to the 
web with the top flange supporting a standing seam roof system shall be determined using a discrete 
point bracing and the provisions of Clause 5.3.3.2.1, or shall be calculated as follows:  
 
 
                                                                                                     . . . 5.3.3.5  
 
φb = 0.9  
 
where  
  
R  =  reduction factor determined by testing in accordance with Section 8  
 
Se  =  elastic  section  modulus  of  the  effective  section  calculated   with  extreme compression or tension 
fibre at fy  
 
5.3.4  Shear  
5.3.4.1  Shear capacity of webs without  holes  
The design shear force ( V*) at any cross -section  shall satisfy — 
V* ≤ φ vVv 
where  
φv = capacity reduction factor for shear (see Table 1.6)  
Vv = nominal shear capacity of the web  
The nominal shear capacity ( Vv) of a  web shall be  calculated from the  following equations, 
as appropriate.  
 
               . . . 5.3.4 (1)  
 
 
 
 
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             . . . 5.3.4 (2 ) 
                 . . . 5.3.4 (3 ) 
 
       Where;  
d1 = depth of the flat portion of the web measured along the plane of the web 
tw = thickness of web  
kv = shear buckling coefficient determined as follows:  
(i) For unstiffened webs:  kv = 5.34 
(ii) For beam  webs  with transverse  stiffeners  complying  with Clause  4.7 
 
for a/d1 ≤ 1.0: kv = 4.00 + [5.34/( a/d 1)2] . . . 5.3.4(4)  
for a/d1 > 1.0: kv = 5.34 + [4.00/( a/d 1)2] . . . 5.3.4(5)  
a = shear panel length for unstiffened  web element;  or 
distance between transverse stiffeners for stiffened web 
elements  
For a web consisting of two or more sheets, each sheet shall be considered as a separate 
element carrying its share of the shear  force.  
 
5.3.4.2  Shear capacity of channel -section webs with  holes  
Shear capacity of channel -section webs with holes shall be applicable within the following limits : 
(a) dwh/d1 <0.7, 
where  
dwh = depth of the web hole  
d1 = depth  of the flat portion  of the web measured  along  the plane  of the web 
(b) dwh/t ≤ 200. 
(c) Holes centred at mid-depth of the web.  
(d) for load bearing studs, minimum should be 8 times the diameter of the service hole  
(e) for non -load bearing studs, minimum should be 4 times the diameter of the service hole  
(f) Non-circular holes corner radii greater than or equal to 2 t. 
(g) Non-circular holes with do ≤ 65 mm and b ≤ 115 mm, where b is the length of the web 
hole.  
(h) Circular hole diameters less than or equal to 150  mm. 
(i) do > 15 mm. 
The nominal shear capacity ( Vv) determ ined in accordance with Clause 5 .3.4.1 sh all be multiplied 
by qs, where  
 DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  lxxix 
  
                                                                                          . . . 5.3.4.2(1 ) 
                                                                                          . . . 5.3.4.2(2 ) 
                                                                    . . . 5.3.4.2(3 ) 
                                                                  . . . 5.3.4.2(4 ) 
dwh   = depth of web hole  
d1      = depth of flat portion of the web measured along the plane of the web  
 
5.3.5  Combined bending and shear  
For beams with unstiffened webs, the design  bending moment (M*) and the design shear 
force  (V*) shall  satisfy  
 
                                                                            . . . 5.3.5(1 ) 
For beams with  transverse web stiffeners, the design be nding moment (M*) shall satisfy  
                                                                                                   . . . 5.3.5(2 ) 
The design  shear force (V*) shall satisfy  
                                                                                                              . . . 5.3.5(3 ) 
 
then M* and V* shall satisfy  
                                                                                  . . . 5.3.5(4 )  
Where  
Ms    = nominal sect ion moment capacity about the centroidal axes determined in  accordance 
with Clause 5 .3.2 
 DKS  2971 : 2022  
lxxx © KEBS 2022  – All rights reserved  
 Vv     = nominal shear capacity when shear alone exists determined in accordance with Clause 
5.3.4 
Mb    = nominal member moment capacity when bending alone exists de termined in accordance 
with Clause 5 .3.3 
 
5.3.6  Bearing  
5.3.6.1  Design for  bearing  
A member subject to bearing (R * ) shall satisfy  
                                                                                                                      . . . 5.3.6.1  
Where  
 
φw = capacity reduction factor for bearing (see Table 1.6)  
 
Rb    = nominal capacity for concentrated load or reaction   for one  solid  web connecting top and bottom 
flanges  
 
5.3.6.2  Bearing without  holes  
The nominal  capacity for concentrated load or reaction for one solid web connecting top   
and bottom flanges (Rb) shall be determined  as follows:  
                              . .5.3.6. 2    Where;  
C = coefficient (see Tables 3.3.6.2(A) to (E))  
tw = thickness of the web  
θ = angle between the plane of the web and the plane of the bearing surface. θ 
shall be within the following limits:  
90° ≥ θ ≥ 45°  
Cr = coefficient of inside bent radius (see Tables 3.3.6.2(A) to (E))  
ri = inside bent radius  
Cl = coefficient of bearing length (see Tables 3. 3.6.2(A) to (E))  
lb = actual bearing length. For the case  of two  equal and opposite  concentrated  loads 
distributed over unequal bearing lengths, the smaller value of lb shall be taken  
Cw = coefficient of web slenderness (see Tables 3.3.6.2(A) to (E))  
d1 = depth of the flat portion of the web measured along the plane of the web 
Webs of members in bending for which d1/tw is greater than 200 shall be provided with adequate 
means of transmitting concentrated actions or reactions directly into the web(s).  
Rb is the nominal capacity for load or reaction for one solid web connecting top and bottom 
flanges. For webs consisting of two or more such sheets, Rb shall be calculated for each 
individual sheet and the results added to obtain the  nominal load or reaction for the full 
section.2  
One-flange loading or reaction occurs when the clear distance between the bearing edges of 
adjacent opposite  concentrated actions or reactions is greater than 1.5 d1 
DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  lxxxi 
  Two-flange loading or reaction occurs when the clear distance between t he bearing edges of 
adjacent opposite concentrated actions or reactions is less than or equal to 1.5 d1. 
End loading or reaction occurs when the distance from the edge of the bearing to the  end of 
the member is less than or equal to 1.5d1. 
Interior loading  or reaction occurs when the distance from the edge of the bearing to the end 
of the member is greater than  1.5d1. 
The Capacity  reduction factors shall be given in Tables 3.3.6.2(A -E)  
 
TABLE   5 .3.6.2(A)  
BACK -TO-BACK CHANNEL -SECTIONS  
 
Support and flange 
conditions   
Load cases   
C  
Cr  
Cl  
Cw  
φw  
Limits  
Fastened to 
support  Stiffened or  
partially stiffened 
flanges  One-flange 
loading or 
reaction  End 10 0.14 0.28 0.001  0.75 r1/tw ≤ 5 
Interior  20 0.15 0.05 0.003  0.90 r1/tw ≤ 5 
Unfastened  Stiffened or  
partially stiffened 
flanges  One-flange 
loading or 
reaction  End 10 0.14 0.28 0.001  0.75 r1/tw ≤ 5 
Interior  20.5 0.17 0.11 0.001  0.85 r1/tw ≤ 3 
Two-flange 
loading or 
reaction  End 15.5 0.09 0.08 0.04 0.75  
r1/tw ≤ 3 
Interior  36 0.14 0.08 0.04 0.75 
Unstiffened 
flanges  One-flange 
loading or 
reaction  End 10 0.14 0.28 0.001  0.75 r1/tw ≤ 5 
Interior  20.5 0.17 0.11 0.001  0.85 r1/tw ≤ 3 
NOTES:  
1 Table  3.3.6.2(A)  applies  to I-beams  made  from  two channels  connected  back  to back.  
2 The coefficients  in Table  3.3.6.2(A)  apply  if lb/tw ≤ 210,  lb/dl ≤ 1.0 and θ = 90°.  
 
TABLE   5 .3.6.2(B)  
SINGLE WEB CHANNEL -SECTIONS AND  C-SECTIONS  
 
Support and flange 
conditions   
Load cases   
C Cr Cl Cw  
φw  
Limits  
Fastened 
to support  Stiffened or 
partially  
stiffened 
flanges  One-flange 
loading or 
reaction  End 4 0.14 0.35 0.02 0.85 ri/tw ≤ 9 
Interior  13 0.23 0.14 0.01 0.90 ri/tw ≤ 5 
Two-flange 
loading or 
reaction  End 7.5 0.08 0.12 0.048  0.85 ri/tw ≤ 12 
Interior  20 0.10 0.08 0.031  0.85 ri/tw ≤ 12 
Unfastened  Stiffened or 
partially 
stiffened 
flanges  One-flange 
loading or 
reaction  End 4 0.14 0.35 0.02 0.80  
ri/tw ≤ 5 
Interior  13 0.23 0.14 0.01 0.90 
Two-flange 
loading or 
reaction  End 13 0.32 0.05 0.04 0.90  
ri/tw ≤ 3 
Interior  24 0.52 0.15 0.001  0.80 
Unstiffened One-flange End 4 0.40 0.60 0.03 0.85 ri/tw ≤ 2 DKS  2971 : 2022  
lxxxii  © KEBS 2022  – All rights reserved  
 flanges loading or 
reaction  Interior  13 0.32 0.10 0.01 0.85 ri/tw ≤ 1 
Two-flange 
loading or 
reaction  End 2 0.11 0.37 0.01 0.75  
ri/tw ≤ 1 
Interior  13 0.47 0.25 0.04 0.80 
NOTE: The coefficients in Tab le 3.3.6.2(B) apply if d1/tw ≤ 200, lb/tw ≤ 210, lb/d1 ≤ 2.0 and θ = 90°.  
 
 
 
 
TABLE   5 .3.6.2(C)  
SINGLE WEB Z -SECTIONS  
 
Support and flange 
conditions   
Load cases   
C  
Cr  
Cl  
Cw  
φw  
Limits  
Fastened to 
support  Stiffened or 
partially  
stiffened flanges  One-flange 
loading or 
reaction  End 4 0.14 0.35 0.02 0.85 ri/tw ≤ 9 
Interior  13 0.23 0.14 0.01 0.90 ri/tw ≤ 5 
Two-flange 
loading or 
reaction  End 9 0.05 0.16 0.052  0.85 ri/tw ≤ 12 
Interior  24 0.07 0.07 0.04 0.80 ri/tw ≤ 12 
Unfastened  Stiffened or 
partially 
stiffened flanges  One-flange 
loading or 
reaction  End 5 0.09 0.02 0.001  0.85  
ri/tw ≤ 5 
Interior  13 0.23 0.14 0.01 0.90 
Two-flange 
loading or 
reaction  End 13 0.32 0.05 0.04 0.90  
ri/tw ≤ 3 
Interior  24 0.52 0.15 0.001  0.80 
Unstiffened 
flanges One-flange 
loading or 
reaction  End 4 0.40 0.60 0.03 0.85 ri/tw ≤ 2 
Interior  13 0.32 0.10 0.01 0.85 ri/tw ≤ 1 
Two-flange 
loading or 
reaction  End 2 0.11 0.37 0.01 0.75  
ri/tw ≤ 1 
Interior  13 0.47 0.25 0.04 0.80 
NOTE: The coefficients in Ta ble 3.3.6.2(C) apply if d1/tw ≤ 200, lb/tw ≤ 210, lb/d1 ≤ 2.0 and θ = 90°.  
 
 
TABLE   5 .3.6.2(D)  
SINGLE HAT SECTIONS  
 
Support conditions  Load cases  C Cr Cl Cw φw Limits  
 
 
Fastened to support  One-flange loading 
or reaction  End 4 0.25 0.68 0.04 0.75 ri/tw ≤ 5 
Interior  17 0.13 0.13 0.04 0.80 ri/tw ≤ 10 
Two-flange loading 
or reaction  End 9 0.10 0.07 0.03 0.85  
ri/tw ≤ 10 
Interior  10 0.14 0.22 0.02 0.85 
 
Unfastened  One-flange loading 
or reaction  End 4 0.25 0.68 0.04 0.75 ri/tw ≤ 4 
Interior  17 0.13 0.13 0.04 0.90 ri/tw ≤ 4 
NOTE: The coefficients in Table 3.3.6.2(D) apply if d1/tw ≤ 200, lb/tw ≤ 200, lb/d1 ≤ 2.0 and θ = 90°.  
 
 
 DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  lxxxiii  
  TABLE   5.3.6.2(E)  
MULTI -WEB DECK SECTIONS  
 
Support conditions  Load cases  C Cr Cl Cw φw Limits  
 
 
Fastened to support  One-flange loading 
or reaction  End 4 0.04 0.25 0.025  0.90 ri/tw ≤ 20 
Interior  8 0.10 0.17 0.004  0.85 ri/tw ≤ 10 
Two-flange loading 
or reaction  End 9 0.12 0.14 0.040  0.85  
ri/tw ≤ 10 
Interior  10 0.11 0.21 0.020  0.85 
 
 
Unfastened   
 
One-flange loading 
or reaction  End 3 0.04 0.29 0.028  0.60  
ri/tw ≤ 20 
Interior  8 0.10 0.17 0.004  0.85 
End 6 0.16 0.15 0.050  0.90  
ri/tw ≤ 5 
Interior  17 0.10 0.10 0.046  0.90 
NOTE: The coefficients in Table 3.3.6.2(E) apply if d1/tw ≤ 200, lb/tw ≤ 210, lb/d1 ≤ 3.0 and 45°< θ ≤ 90°. 
 
 
5.3.6.3  Web crippling strength of channel -section webs with  holes  
When a web hole is within the bearing length (lb ), a bearing stiffener  shall be used.  For beam  webs with 
holes, the web crippling strength shall be calculated in accordance with C lause  5.3.6.2  multiplied  by the 
reduction  factor  (Rc), given  in this Clause.  
Web  crippling strength of  channel -section   webs   with   holes, as  determined   by Clause 
5.3.6.2, shall be applicable  within the following limits : 
(a) dwh/d1 < 0.7.  
(b) d1/t ≤ 2 00. 
(c) Holes centred at mid -depth of the web.  
(d) Clear distance between holes is greater than or equal to 450 mm.  
(e) Distance between the end of the member and the edge of the hole is greater than or equal 
to d. 
(f)  Non -circular holes corner radii grea ter than or equal to 2t.  
(g) Non -circular holes with dwh ≤ 65 mm and b ≤ 115 mm.  
(h) Circular hole diameters less than or equal to 150 mm.  
(i)  dwh > 15 mm.  
When a web hole is not within the bearing length (lb ≥ 25 mm):  
 
                                 . .5.3.6. 3(1) 
When any po rtion of a web hole is not within the bearing length (lb ≥ 75 mm):  
                                                                      . .5.3.6.3(2 ) 
Where  DKS  2971 : 2022  
lxxxiv  © KEBS 2022  – All rights reserved  
 lb    = bearing length  
d   = depth of cross -section  
x   = nearest distanc e between the web hole an d the edge bearing  
 
5.3.7  Comined Bending and Bearing  
Unstiffened flat webs of shapes subjected to a combination of bending and reaction or concentrated load shall be 
designed as follows:  
 
(a) Shapes having single unstiffened webs Shapes hav ing single unstiffened we bs shall 
satisfy  
                                                                           . .5.3.7 (1) 
At the interior supports of continuous spans, the above interaction is not applicable to 
deck or beams with two or more single webs, where the compression  edges of  adjacent  
webs are laterally supported in the negative moment region by continuous or 
intermittently connected flange elements, rigid cladding, or lateral bracing, and the 
spacing between adjacent webs does not exceed  250 mm. 
(b) Back -to-back channel beams and beams with restraint against web rotation Back -to- 
back channel beams and beams with restraint against web rotation, such as I-sections 
made by welding two angles to a channel, shall satisfy  
 
                                                                 . .5.3.7. (2)  
 , the nominal concentrated load or reaction  
strength may be determ ined in accordance with Clause 5 .3.6 
 
R*     = design concentrated load or reaction in the presence of bend ing moment  
Rb     = nomin al capacity for concentrated load or reaction in the absence of bending 
moment assuming single web interior one flange loading for the nested Z -sections, i.e., the 
sum of the two webs evaluated individually determined in accordance  with Clause 5.3.6  
φ b    = capacity reduction factor for bending  
φ w   = capacity reduction factor for bearing  
M*    = design   bending   moment at, or immediately adjacent to, the   point   of application 
of the design concentrated load or reaction (R*)  
Ms    = nominal sec tion moment capacity about the centroidal axes determined in 
accordance with Clause 5.3.1  
tw       = thickness of the web  
λ     = slenderness ratio (see Clause 5.2.1.2)  
 
(c)     Two nested Z -sections   Two nested Z -sections shall satisfy  
                                                                . .5.3.7. (3 )  
DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  lxxxv  
  Where  
 
R*     = design concentrated action or reaction in the presence of bending moment  
 
Rb     = nominal capacity for concentrated action or reaction in the absence of bendi ng 
moment assuming single web interior one flange loading for the   nested   Z -sections,  i.e.,   
the   sum   of   the   two   webs   evaluated individually determined in accordance with 
Clause 3.3.6  
φ     = 0.9  
M*    = design bending moment at the section under consideration to, the point of 
application of the design concentrated load or reaction (R*)  
Ms     = nominal section moment capacity for the two nested Z -sections, i.e., the sum   of   
the   tw o   sections   evaluated   individually, determined    in accordance with Clause 5 .3.1 
 
In addition, M* and R* shall satisfy  
                                                                                                       . .5.3.7. (4 ) 
                                                                                                             . .5.3.7. (5 ) 
 
Equation 3.3.7(3) applies, if— 
(i) d1/t ≤ 150; 
(ii) lb/tw ≤ 140; 
(iii) fy ≤ 480 MPa;  and 
(iv) ri t ≤ 5.5  . 
The following conditions shall be satisfied:  
(A) The ends of each section shall be connected to the  other section by a minimum  of 
two 12.0 mm  diameter A307 bolts through the web.  
(B) The combined  section  shall  be connected  to the support  by a minimum  of two 
12.0 mm A307 bolts through the flanges.  
(C) The webs  of the two sections  shall  be in contact.  
(D) The ratio of the thicker  to the thinner  part shall  not exceed  1.3. 
 
5.3.8  Stiffeners  
5.3.8.1  Transverse  stiffeners  
Transverse stiffene rs attached to beam webs at points  of concentrated  loads or reactions  shall  be 
designed as compression members. Concentrated loads or reactions shall be applied directly into the 
stiffeners, or each stiffener shall be fitted accurately to the  flat portion  of the  flange to provide direct load-
bearing into the end of the stiffener.  Means for  shear  transfer  between the  stiffener  and the web shall  
be provided  in   accordance   with Clause  5.3.8.2.  The design  concentrated  loads  or reactions  (N*) shall  
satisfy  the following:  
 
                                                                                                                   . .5.3.8.1. (1 ) 
                                                                                                                     . .5.3.8 .1  (2) DKS  2971 : 2022  
lxxxvi  © KEBS 2022  – All rights reserved  
  
where  
φc = capacity  reduction  factor  for members  in compression  (see Table  1.6) 
Ns = nominal  section  capacity  of a member  in compression  (see Clause  3.4) 
= fwyAs1 
Nc = nominal  member  capacity  of a member  in compression  (see Clause  3.4) 
= fnAs2  
fwy = lower yield stress value of the beam web (fy) or of the stiffener 
section  (fys) 
fn = critical stress (see Clause  3.4) 
As1, As2 = area of a member in compression consisting of the transverse 
stiffeners and a portion of the  web 
As1 =   18t2 + As ................................ ................................ .................  5.3.8.1(3)  
(for transverse  stiffeners  at interior  support  and under 
concentrated  load)  
=   10t2 + As . . . 5.3.8.1(4)  
(for transverse stiffeners at end support)  
As2 =   b1t + As . . . 5.3.8.1(5)  
(for transverse  stiffeners  at interior  support  and under 
concentrated  load)  
 
=   b2t + As ................................ ................................ ...................  5.3.8.1(6)  
(for transverse stiffeners at end support)  
t = base thickness of beam  web 
As = cross -sectional area of transverse stiffeners  
 
                                      5.3.8.1(7 ) 
                                     5.3.8.1(8 ) 
 
 
5.3.8.2  Bearing stiffeners in channel -section flexural  members  
For two-flange loading of channel -section flexural members with bearing stiffeners that do  not 
meet the requirements of Clause 3.3.8.1, the design bearin g capacity (φ wRb) shall be 
determined  from— 
Rb = 0.7(Rwc + Ae fy)  ≥ Rwc . . . 5.3.8.2  
where  
φw = capacity reduction factor for bearing stiffeners (see Table 1.6)  
Rwc = web crippling capacity for channel -section flexural member calculated in 
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  accordance with Equation 3.3.6.1 for single web members, at the end  or interior  
locations  
Ae = effective area of the bearing stiffener subjected to uniform compressive stress, 
calculated at yield point  
fy = yield point of the bearing stiffener  steel  
Equat ion 5 .3.8.2 applies within the following  limits:  
(a) Full bearing of the stiffener is required. If the bearing width is narrower than the 
stiffener such that one of the stiffener flanges is unsupported, Rb shall be reduced 
by 50%.  
(b) Stiffeners shall be channel -section stud or track members with a  minimum  web depth 
of 90 mm and a minimum  base  steel  thickness  of 0.85 mm. 
(c) The stiffener shall be attached to the flexural member web with at  least  three  
fasteners  (screws or bolts).  
(d) The distance from the flexural member flanges to the first fastener(s) shall be not less 
than d/8, where  d is the overall  depth  of the flexural  member.  
(e) The length of the stiffener shall be not less than the depth of the flexural  member  
minus  10 mm. 
(f) The bearing  width  shall  be not less than 40 mm. 
 
5.3.8.3  Shear  stiffeners  
Where shear stiffeners are required, the spacing shall be such  that the design shear force   
shall not exceed the design  shear capacity (φvVv) specified in Clause 5 .3.4, and the ratio    
a/d1 shall exceed neither [260/( d1/t)]2 nor 3.0. 
The actual second moment of area (Is,min.) of a pair of  attached  shear stiffeners,  or  of  a 
single shear stiffener, with reference to an axis in the plane of the web, shall  have  a  
minimum value as follows:  
 
                                                              . . . 5.3.8.3(1)  
The gross area of shear stiffeners (Ast) shall be not less than  
                                        . . . 5.3.8.3(2 )   
Where  
ks       =   shear stiffener coefficient  
DKS  2971 : 2022  
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                                                                                . . . 5.3.8.3(3 )   
 
                                                                           . . . 5.3.8.3( 4)   
  
 
kst     =   stiffener type coefficient  
=   1.0 for stiffeners in pairs  
=   1.8 for single -angle stiffeners  
=   2.4 for single -plate stiffeners  
kv      = shear buckling coefficent  
                                                            . . . 5.3.8.3(5 )   
 
                                                        . . . 5.3.8.3( 6)    
a     =   distance between transverse stiffeners  
 
5.3.8.4  Non-conforming  stiffeners  
The design capacities of members with transverse stiffenersthat do not comply with Clauses 5.3.8.1 or 
5.3.8.2,such as stamped or rolled -in reverse stiffeners, shall be determined by tests i n accordance with 
Section 8  
 DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  lxxxix  
  5.4 Concentrically loaded compression members  
5.4.1  General  
This Clause applies to members in which the resultant of  all loads acting on the  member  is an axial load 
passing through the centroid of the effective section calculated at the critical stress  (fn). The design  
compressive  axial  force  (N*) shall  satisfy  the following:  
 
(a)     N* ≤ φcNs  
(b)     N* ≤ φcNc  
 
where  
 
φc = capacity  reduction factor for members in compression (see Table 1.6)  
 
Ns = nominal  section capacity of the member in compression  
 
=Ae/fy                                                                                 ……5.4.1(1)  
 
Ae = effective area at yield stress (fy)  
 
Nc = nominal member capacity of the member in compression  
 
= Ae / fn                                                                                 . . . 5 .4.1(2)  
 
Ae = effective  area at the critical stress (fn). For sections with circular holes, Ae shall be determined in 
accordance with Clause 2.2.2.2. If the product of the number of holes in the effec tive length region and 
the hole diameter divided by the effective length does not exceed 0.015, Ae    can be  determined ignoring 
the holes  
 
fn   = critical   stress,  and   shall be determined from Equation 5 .4.1(3)   or  
Equation 5 .4.1(4), as appropriate  
 
 
                                                                                . . . 5.4.1( 3) 
 
                                                                             . . . 5.4.1(4 )  
 
Where  
 
λc       = non -dimensional slen derness used to determine  
 
                                                                                                                 . . . 5.4.1(5 ) 
 
foc     = least of the elastic flexural, torsional and flexural -torsional buckling stress determi ned in 
accordance with Clauses 5.4.2 to 5 .4.4, or a rational elastic buckling analysis  
 
Concentrically loaded angle sections shall be designed for an additional bending moment as  specified in 
the definition of M * specified in C lause 5 .5.1. 
 
NOTE: The slenderness ratio (le/r) of all compression members should not exceed 200, except  that only 
during construction le/r should not exceed 300.  
DKS  2971 : 2022  
xc © KEBS 2022  – All rights reserved  
 5.4.2  Sections not subject to torsional or flexural -torsional  buckling  
For doubly -symmetric sectio ns, closed cross -sections and any other sections that can be shown not to be 
subject to torsional or flexural -torsional buckling, the elastic flexural buckling  stress (foc) shall be 
determined as follows:  
 
                                                                                                             . . . 5.4.2(1 ) 
 
Where  
 
le    = effective length of member  
 
r   = radius of gyration of the full, unreduced cross -section  
  
For G550 steel to AS 1397 less than 0.9 mm in thickness, a reduced radius  of gyration γr  
shall be used in Equation 3.4.2(1) when the value of the effective length (le) is less than  
1.1lo,  
 
Where  
 
                                 . . . 5.4.2(2 ) 
fcr = plate elastic buckling stress  
 
                                                                                                            . . . 5.4.2(3)    
 
NOTES:  
1 In frames where lateral stability is provided by diagonal bracing, shear walls, attachment to an adjacent 
structure having adequate lateral stability, or floor slabs or roof decks secured horizontally by walls or bracing 
systems parallel to the plane of the frame, and in trusses, the effective length (le) for compression members 
that do not depend upon their own bending stiffness for lateral stability of the frame or t russ should be taken as 
equal to the unbraced length (l), unless analysis shows that a smaller value may be used.  
2 In a frame that depends upon its own bending stiffness for lateral stability, the effective length (le) of the 
compression members should be  determined by a rational method and should be not less than the actual 
unbraced length.  
 
 
5.4.3  Doubly - or singly symmetric  sections (see Figures 1.5(a) and (c)) subject to torsional or 
flexural -torsional  buckling  
 
For sections subject to torsional or flexural -torsional buckling, foc shall be taken as  the smaller  of 
foc calculated  using  Equation  3.4.2(1)  with r = ry and foxz calculated  as follows:  
 
                                      . . . 5.4.3(1 )    
 
where fox and foz are specifie d in Clause 5 .3.3.2.1(a).  
 
Alternatively, a conservative estimate of foxz can be obta ined from Equation 5 .4.3(2) as follows:  
DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  xci 
  
                                                   . . . 5.4.3(2 )    
where fox and foz are specified in Clause 5.3.3.2.1(a).  
 
                                                                                              . . . 5.4.3(3 )    
rol      =  polar radius of gyration of the cross -section about the shear centre  
 
   For singly symmetric  sections, the x -axis shall be assumed to be the axis of symmetry.  
 
For singly symmetric  sections,  the x-axis shall  be assumed  to be the axis of symmetry.  
For doubly -symmetric sections subject to torsional buckling, foc shall be taken  as the smaller  
of foc calculated in accordance  with Clause 5 .4.2 and foc = foz, where foz is  specified   in Clause  
5.3.3.2.1.  
For singly -symmetric unstiffened angle sections for which the effective area ( Ae) at  stress  ( fy) 
is equal to the full unreduced cross -sectional area ( A), foc shall be calculated using Equation 
5.4.2 where  r is the least  radius  of gyration.  
 
5.4.4  Point -symmetric sections (see Figure  1.5(b))  
For point -symmetric sections subject to flexural or torsional buckling, foc shall be taken  as the   
smaller  of  foc  calculated  in  accordance  with  Clause  5.4.2 and foz   specified   in Clause  
5.3.3.2(a).  
 
5.4.5  Non-symmetric sections (see Figure  1.5(d))  
For shapes whose cross -sections do not have any symmetry, either about an axis or about a 
point, foc shall be taken as the smallest value which  shall satisfy cub ic Equation 5 .4.5, as follows:  
 
                                     . . . 5.4.3(5)  
 
Alternatively, compression members composed of such shapes may be tested in 
accordance with Clause  6.2. 
 
5.4.6  Singly -symmetric sections (see Figure 1.5(c)) subject to distorti onal b u c k l i n g  
For monosymmetric sections subject to distortional buckling, such as lipped channels with additional rear 
flanges, the value of Nc in Equation 5.4.1(2) shall be the lesser of the following : 
 
(a) Ae fn calculate d in accordance with Equations 5 .4.1(3) and 5.4.1(4).  
(b)  
(c) 
                                                        . . . 5.4.6(1 ) 
                      . . . 5.4.6(2)  DKS  2971 : 2022  
xcii © KEBS 2022  – All rights reserved  
 fod shall be calculated using either the appropriate equations given in Appendix D  or  a  
rational  elastic  buckling  analysis.  A is the area of the full cross -section.  
 
5.4.7  Columns with one flange through -fastened to sheeting  
This Clause applies to channel - or Z-sections concentrically loaded along their longitudinal axis, with only one 
flange attached to sheeting by screw fasteners.  
The nominal member capacity (Nc) in axial compression of simple span or continuous channels  or Z-
sections  shall  be determined  from Equation  3.4.7  as follows:  
(a) For weak  axis: 
                    . . . 5.4.7  
s = fastener distance from the centre -line of the web divided by the  flange  
width for Z-sections;  or 
 
flange width minus the fastener distance from the centre -line of the web 
divided by the flange width for channel -sections  
t = thickness of the channel - or Z-section  
bf = flange width of the channel - or Z-section 
d = depth of the channel - or Z-section  
A = gross cross -sectional area of the channel - or Z-section  
NOTE: Units of t, bf and d in Equation 5 .4.7 are in millimetres, since Equation 5 .4.7 is 
not non -dimensional.  
Equation 5.4.7 shall be limited to roof and wall systems complying  with the following:  
(i) Channel - and Z-sections not exceeding 3.2 mm in thickness.  
(ii) Channel - and Z-sections with depths of 150 to 300 mm. 
(iii) Flanges are edge -stiffened compression  elements.  
(iv) 70 ≤ depth/thickness  ≤170.  
(v) 2.8 ≤ depth/flange  width <5. 
(vi) 16 ≤ flat width/thickness of flange  <50. 
(vii) Both flanges prevented from moving laterally at the supports.  
(viii) Roof or  wall panels with fasteners spaced 300 mm  on centre or  less and having  
a minimum rotational lateral stiffness of 10.3 kN/mm2 [faste ner at mid-flange width  
as determined  by the relevant  test procedure s. 
(ix) Minimum yield stress of 230 MPa.  
(x) Span lengths from 4.5 to 9 m. 
(b) For strong  axis The equations  given  in Clauses  5.5.1 and 5.5.2 shall  be used.  
 
 
 
 
 DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  xciii 
  5.5 Combined Axial Compressionor Tension, and Bending  
5.5.1  Combined axial compression and bending  
The design axial compression (N*), and the design bending moments (M * and M *) about the x -and y -axes of the 
effective section, respectively shall satisfy the following:  
                                                                           . . . 5.5.1(1)  
 
                                                                                           . . . 5.5.1(2)  
 
where  
Nc = nominal member capacity of the member in compression determined in 
accordance with Clause  5.4 
 
Cmx, Cmy = coefficients for unequal end moment whose value shall be taken as  follows : 
(i) For compression members in frames subject to joint translation 
(side -sway):  
Cm = 0.85  
(ii) For restrained compression members in frames braced against  
joint translation and not subject to transverse loading between their  
supports in the plane of bending:  
Cm = 0.6 − 0.4(M1/M2) . . . 5.5.1(4)  
M1/M2 is the ratio of the smaller to the larger moment at the 
ends of that portion of the member under consideration  which 
is unbraced in the plane of bending.  M1/M2 is positive  if the 
member is bent in reverse curvature and negative if it is bent 
in single  curvature.  
(iii) For compression members in frames braced against joint  
translation in the plane of loading and subject  to transve rse 
loading between their supports, the value of Cm may be  determined  
by rational analysis. However, in lieu  of such  analysis, the following 
values may be used:  
(A) For members whose ends are restrained  
Cm = 0.85  
(B) For members whose ends are unrestrained  
Cm = 1.0 
Mx My= design bending moment about the x - and y -axes of the effective 
section, respectively, determined for the design axial force alone for   
singly -symmetric   unstiffened   angle   sections   with   unreduced 
effective area, M * shall be permitted  to be taken as the design bending 
moment only. For other angle sections or singly symmetric  unstiffened 
angles for which the effective area (Ae) at stress (fy) is less than the full 
unreduced cross -sectional area (A), M *  shall be taken either as the  
design bending moment, or the required flexural moment plus N*l/1000, 
whichever results in a lower value of N c DKS  2971 : 2022  
xciv © KEBS 2022  – All rights reserved  
 Mbx, Mby     =   nominal member moment capacity about the x - and 
y-axes, respectively, determ ined in accordance with Clause 5 .3.3 
φb =     capacity r educ tion factor for bending  
= 0.95 and 0.90 for bending strength (see Table 1.6); or   
0.90 for laterally unbraced beam (see Table 1.6)  
φc = capacity reduction factor for members in compression  
= 0.85  
Ns = nominal section capacity of the member in compressi on determined 
in accordance with Cl ause 5 .4, with f n equal to f y 
αnx, αny        = moment amplification factors  
 
                                                  . . . 5.5.1(5 ) 
Ne     = elastic buckling load  
 
                                                          . . . 5.5.1(6 ) 
Ib = second moment of area of the full, unreduced cross -section  about  
the bending axis  
Leb = effective length in the plane of bending   
In addition, each individual ratio in Equations 5.5.1(1), 
5.5.1(2 ) and 5.5.1(3)  shall  not  exceed  unity.  
 
DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  xcv 
  5.5.2  Combined axial tension and  bending  
The design axial tension (N*), and the required bending moments (M *) and (M *) about the  x- and y -axes of the 
effective section, respectively, shall satisfy the following:  
 
                                                                                   . . . 5.5.2(1 ) 
 
                                                                                    . . . 5.5.2(2 ) 
 
Where  
 
Nt    = nominal section capacity of the member in ten sion determined  in accordance with Clause 5 .2 
 
Msxf, Msyf   = nominal section yield moment capacity of the full section about the  x-axis and y -axis, respectively  
 
= Z ft fy                                                                                                                                                                                                                               . . . 5.5.2(3 ) 
 
Zft     = section modulus of the full unreduced section for the extreme tension fibre about the approp riate axis  
 
 
 
 
5.6 Cylindrical Tubular Members  
5.6.1  General  
This Clause applies to cylindrical tubular members having a ratio  of outside  diameter  to wall  thickness (do/t) 
not greater than  0.441 E/fy. 
 
5.6.2  Bending  
For flexural members, the design bending moment (M*) unco upled from axial load, shear   and local 
concentrated forces or reactions shall  satisfy  
M* ≤ φ bMb 
where Mb is the nominal member moment  capacity  and shall  be calculated  from Equations 
5.6.2(1) to 5.6.2(3), as appropriate.  
                                               …5.6.2(1 ) 
              …5.6.2(2 ) 
                                  …5.6.2(3 ) 
5.6.3  Compression  
This Clause applies to members in which the resultant of all design  loads  and  design  bending moments  
acting on the  member  is equivalent to a single force in the direction of  the member  axis passing  through  
the centroid  of the section.  
The design axial load ( N*) shall satisfy  
N* ≤ φ cNc 
DKS  2971 : 2022  
xcvi © KEBS 2022  – All rights reserved  
 where  
Nc   =   fn Ae . . . 5.6.3(1)  
fn = critical stress  and shall  be calculated  from Equation 3.6.3(2)  or 
Equation 5.6.3(3), as appropriate.  
 
                                                             . . . 5.6.3(2 ) 
                                                               . . . 5.6.3(3 ) 
λc       = slenderness factor  
                                                          . . . 5.6.3(4 ) 
foc     = elastic flexural buckling stress determined in accordance with  Clause 5 .4.1 
Ae = effective area at the critical stress (f n) 
=  A o + R(A – Ao)                                                                               .       . . 5.6.3(5 ) 
Ao = reduced area due to local buckling  
                        . . 5.6.3(6 ) 
R = reduction factor  
                                                                 . . 5.6.3(7 ) 
A = area of the full, unreduced cross -section  
 
5.6.4  Combined bending and compression  
Combined bending and compression shal l be in accordance with Clause 4 .5. 
 
 
 
 
 
 
 
 
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  5 S E C T I O N  4  – S T R U C T U R A L  A S S E M B L I E S    
6.1 Built -up Sections  
6.1.1  I-sections composed of two channels  
The maximum longitudinal spacing of welds or other connectors  (smax.)  joining  two channels  to form an I-
section  shall  be determined  as follows:  
(a) For compression  members  
                                                                                                        . . 6.1.1(1 ) 
where 
l      = unbraced length of the member in compression  
rcy     = radius of gyration of one channel about its centroidal axis p arallel to the web  
r1       = radius of gyration of the I -section about the axis perpendicular to the direction in which buckling 
occurs for the given conditions of end support and intermediate bracing  
(b) For flexural  members  
 
                                                                                                                    . . 6.1.1(2 ) 
                                                                                                                                
where 
l    = span of beam  
sg   = vertical distance between two rows of connections nearest to the top and bottom flanges  
N* = des ign tensile force of the connection  
q   = intensity of the design action on the beam  
m = distance from the shear centre of one ch annel to the mid -plane of its web  
(see Table E1 of Appendix E)  
The intensity of the design load (q) shall be obtained by dividi ng the magnitude  of the  design  
concentrated actions or reactions by the length of bearing. For beams designed for a uniformly 
distributed load, q shall be equal to three times the intensity of the uniformly distributed design 
action. If the length of beari ng of a concentrated action or reaction is less than the weld 
spacing ( sw), the design  tensile force of the welds or connections closest to the  load or 
reaction shall be determined as follows:  
                                                                                                            . . 6.1.1(3 ) 
Where R*b   is the design concentrated action or reaction.  
The maximum  spacing of connections (smax.) depends upon the intensity of the action  applied  
directly at the connection. Therefore, if uniform spacing of connections is used over the whole 
length of the beam, it shall be determined at the point of maximum local load i ntensity. In 
cases where this procedure may result in uneconomically  close spacing, either   of the 
following methods may be adopted:  
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 (i) The connection spacing may be varied along the beam in accordance  with the 
variation of the load intensity.  
(ii) The reinforcin g cover plates may be welded to the flanges at points  where  
concentrated loads occur. The design sheer  force of the connections  joining  these  
plates to the flanges shall then be used for N*, and sg shall be taken as the depth of the 
beam.  
 
6.1.2  Cover plates, sh eets or non-integral stiffeners in compression  
The spacing (s) in the line of stress  of welds , bolts or rivets connecting a cov er plate, sheet, or 
a non-integral  stiffener  in compression  to another  element  shall  not exceed  
(a)  that which is required to tr ansmit the shear between the connected parts on the basis of 
the design shear force per connection specified in this Clause;  
(b) 1.16t  (E /fc ), where t is the thickness of the cover plate or sheet, and fc is the stress  at 
unfactored load in the cover plate  or sheet; and  
(c)  three times the flat width (b) of the narrowest unstiffened compression element in that 
portion of the cove r plate or sheet that is tributary to the connections, but not less  than 
 if 
  or 
  if
  unless closer 
spacing is required by Ite m (a) or (b).  
In the case of intermittent fillet welds parallel to the direction of stress, the spacing shall be 
taken as the c lear distance between welds plus 12 mm. In all other cases, the spacing shall   
be taken as the centre -to-centre distance between  connections.  
This Clause does not apply to cover sheets that act only  as sheeting  material and  shall  not 
be considered as load-carrying  elements.  
 
6.2 Mixed Systems  
The design of members in mixed systems using cold-formed steel components  in conjunction  with other 
materials shall conform to this Standard and to the relevant material Standard.  
 
6.3 Lateral Restraints  
6.3.1  General  
Lateral restr aints required to restrain lateral bending or twisting of a loaded beam or column shall be in 
accordance with Clauses 6.3.2 and 6.3.3. Local buckling at the points  of attachment of the restraints shall 
be avoided.  
 
6.3.2  Symmetrical beams and columns  
6.3.2.1  General  
Restraints and restraining systems, including connections, shall be designed in accordance with strength 
and stiffness requirements.  
 
6.3.2.2  Restraint against lateral  deflection  
The lateral restraint at  any cross -section of  the member being restrained shall be  designed   to  
transfer a  force acting at  the critical flange equal to  0.025 times the maximum force in  the critical 
flanges of the adjacent segments or  sub-segments, except where  the  restraints  are more  closely  
spaced  than is required  to ensure  that M* = φbMb. 
If the restraints are more closely spaced, then the restraint may be  designed  for a  lesser  force. The 
actual arrangement of restraints shall be assumed to be equivalent to a set of restraints that will ensure 
that M* = φbMb. Each equivalent restraint  shall correspond to an appropriate group of actual restraints. 
This group shall then be designed as  a  whole  to transfer the force of 0.025  times the maximum  force 
in the critical flanges of the equivalent adjacent segments or sub-segments.  DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  xcix 
   
6.3.2.3  Restraint a gainst twist  rotation  
A torsional restraint at a cross -section of the member being restrained may be deemed to provide effective 
restraint against twist rotation if it is designed to transfer a force equal to 0.025 times the maximum force 
in the critical flange from any unrestrained flange to the lateral  restraint.  
 
6.3.2.4  Parallel restrained  members  
If a series of parallel members is restrained by a line of restraints, each restraining element shall be 
designed to transfer  a force  equal to the  sum of 0.025 times the flange force from  the connected 
member and 0.0125 times the sum of the flange forces in the connected members  beyond,  except  that 
no more  than seven  members  need  be considered.  
 
6.3.2.5  Restraint against lateral  rotation  
A rotational restraint at a cross -secti on of the member being restrained may be deemed to provide 
restraint against lateral rotation out of the plane of bending, provided its flexural stiffness in the plane of 
rotation is comparable with the corresponding stiffness of the restrained  member.  
 
6.3.3  Channel - and Z-section  beams  
6.3.3.1  General  
The requirements for bracing to restrain twisting of channel - and Z-sections used as beams and  loaded  
in the plane  of the web,  apply  only if— 
(a) the top flange is connected to the deck or sheeting material in  accordance  with 
Clauses 6 .3.3.2 and 6.3.3.3 so as to effectively restrain lateral deflection of the 
connected flange;  or 
(b) neither flange is connected . 
If both flanges are connected, further bracing is not required.  
6.3.3.2  One flange  connected  to sheeting  and subjected  to wind  uplift 
Channel - and Z -sections, used to support attached covering material and loaded in a plane parallel to the 
web, shall be designed taking into account the restraining effects of covering materials and fasteners. 
Provisions shall be made for the forces,  from each beam, that accumulate in the covering material. These 
forces shall be transferred from the covering material to a member or assembly of sufficient strength and 
stiffness to resist these forces.  
NOTE: This may be achieved by one of the following means:  
(a) A system of bridging or bracing members sufficiently strong to carry the forces to a 
stiff member.  
(b) Arranging equally loaded alternating members to oppose each  other.  
(c) A diaphragm with sufficient rigidity to transfer the forces to a stiff perimeter me mber, 
coupled  with devices  (e.g.,  cleats),  which  restrain  rotation  of the beams  at their 
supports.  
(d) Direct axial stress in the roof sheets. The forces in this case may be taken out at the 
roof where  equal and opposite forces  meet.  
(e) Other designs in which the forces might be transferred to stiff members at the eaves, 
such as the eaves struts in a shed  roof.  
 
For beam systems that satisfy the cleat and screw -fastening requirements of Clause 5 .3.3.4, Items (ix) to 
(xiv), the bracing does not need to be connected  to a stiff member but shall be capable of preventing 
torsional deformation of the beam at the point of attachment.  
 
6.3.3.3  Bracing for roof systems under gravity  load 
For channel - and Z-sections, designed in accordance with Clause 5.3.3 and having the sheeting DKS  2971 : 2022  
c © KEBS 2022  – All rights reserved  
 fastened directly to the top flanges in such a manner that  inhibits relative  movement  between the 
sheeting and the purlin flange, provisions shall be  made  to restrain the flanges so that the maximum 
top flange lateral displacements with respect to the purlin reaction points shall not exceed the span 
length divided by 360. If the top flanges of all purlins  face in the same direction, anchorage of the 
restraint  system  shall  comply  with Items (a) and (b) of this Clause. If the top flanges of adjacent lines of 
purlins face in  opposite directions, a restraint system shall be provided to resist  the downward  
component of  the total gravity  load.  
Anchored braces may be connected to only one line  of purlins in each purlin bay of each roof  slope, if 
provision is made to transmit forces from other purlin lines through  the sheeting  and its fastening 
system. Anchored braces shall be as close as  possible  to the flange that is connected to the sheeting. 
Anchored braces shall be provided for each purlin bay . 
For bracing arrang ements other than those specified in Items (a) and (b), tests in accordance with 
Section 6 shall be performed so that  the type and spacing of braces  selected are such that  the test 
capacity of the braced purlin assembly is greater than or equal to its nomi nal flexural capacity, instead 
of that required by Section 6.  
 
For roof systems using channel - and Z -sections, the following shall be considered:  
(a) Channel -sections for roof systems using channel -sections for purlins with all 
compression  flanges  facing  in the same  direction,  a system  possessing  the 
following the restraint force N*ib in addition to other loads, shall be provided.  
 
                                                                   .6.3.3.3 (1) 
where 
N ib= design  force to be resisted by intermed iate beam brace  
α        = coefficient  
          = +1   for purlin facing upward direction  
          =   -1   for purlin facing downward direction  
θ  = angle between the vertical and the plane of the web of the channel - section  
F *        = total vertical design load supported by all purlin lines being restraint.  Where 
more than one brace is used at a purlin,  N*ib shall be divided  equally between all 
braces  
 NOTE: A positive value for  N*ib means that restraint is required to prevent movement 
of the  purlin f langes in the upward roof slope direction, and a negative value means 
that restraint is  required to prevent movement of purlin flanges in the downward slope 
direction.  
 
(b) Z-sections for roof systems  with a  diaphragm  stiffness  of at least  350 kN/m, and 4  to 20 
Z-purlin lines with all top flanges facing in the direction of the upward roof slope,  and 
with restraint  braces  at the purlin  supports,  midspan  or one-third points, each brace 
shall be designed to resist a design force determined as follows;  
 
(i)      Si ngle-span system with restraint at the supports:  
                                                    .6.3.3.3( 2) 
 
(ii)     Single -span system with third -point restraints:  
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                                                    .6.3.3.3(3) 
 
(iii) Single -span system with midspan restraint:  
 
                                                                  .6.3.3.3( 4)  
(iv) Multiple -span system with restraints at the supports  
 
                                                       .6.3.3.3( 5) 
Ctr     = coefficient used to determine  N*ib for multiple -span system  with restraints at the 
supports  
= 0.63 for braces at end supports of multiple -span systems  
= 0.87 for braces at the first interior supports  
= 0.81 for all other braces  
(v) Multiple -span system  with third -point restraints:  
 
                                                      .6.3.3.3(6 ) 
Ctr     = coefficient used to determine N* ib for multiple -span system with restraints at the 
supports  
= 0.63  for braces at end supports of multiple -span syste ms 
= 0.87  for braces at the first interior supports  
 
(vi) Multiple -span system with third -point restraints:  
                                                  .6.3.3.3( 7) 
Cms = coefficient  used to determine  N*ib for multiple -span system  with midspan restr aints  
= 1.05 for braces in exterior spans  
= 0.90  for all other braces  
 
where  
  
bf       = flat  width of flange  
np      = number  of parallel purlin lines  
t      = thickness  of the section  
θ     = angle  between the vertical and the plane of the web of the Z -sectio n 
l      = length  of the member  
F *p   = total design load supported by the purlin   lines  between  adjacent   
supports  
 
 
The design force  N*ip is positive if restraint is requ ired to prevent movement of the purlin  
flanges in the upward roof slope directio n. 
 
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 For systems with less than four purlin lines, the brace force shall be determined by taking  
1.1 times the force calculated using Equations  6.3.3.3(2 ) to 6.3.3.3(7 ), with np  = 4.  For 
systems with more than 20  purlin lines, the brace force shall be determined us ing 
Equations 6.3.3.3(2) to 6.3.3.3(7) with np = 20 and F *  based on the total number of purlins.  
6.3.3.4  Neither flange connected to sheeting or connected to sheeting  with concealed fasteners  
Each intermediate brace, at the top and bottom flanges, shall be designed to resist a horizontal  design  
force  ( N*ib) determined as follows;  
 
(a)For uniformly distributed loads, *    = 1.5k  times the d esign load within a distance  
0.5l b each side of the brace, where l b is the distance between centre  - line of braces.  
 
(b)For concentrated loads , Nib = 1.0k  times each  design  concentrated load within a distance 0.3lb    
each   side   of   the   brace, plus   1.4k(1  m/lb)  times each   design  concentrated load located farther 
than 0.3a but not farther than 1.0a from the brace, where  m is the dis tance from the concentrated load 
to the brace and a is the distance between centre -lines of braces.  
 
For channel -sections:  
 
                                                                                                                              ..6.3.3. 4(1) 
For Z -sections:    
 
                                                                               ...6.3.3.4(2) 
 
where  
k       = coefficient  used to determine  ib   where neither flange is connected to the  sheeting  or connect ed to 
the sheeting with concealed fasteners  
 
Lx*y*       = product  of second moment of area of the full section about its major and  
minor principal axes parallel and perpendicular to the web  
 
I x          = second moment of   area  of  the  cross -section  a bout  its  centroidal  axis  perpendicular to the 
web 
Braces shall be designed to avoid local buckling at the points of attachment to th e member.  
 
Braces shall be attached in such a manner as to prevent lateral deflection of either flange in 
either directio n at intermediate braces. If one-third or more of the total design load on the 
beam is concentrated over a length of one-twelfth or less of the span of the beam, an  
additional  brace  shall  be placed  at or near the centre  of this loaded  length.  
Other braces are not required if all loads and reactions on a beam are transmitted through 
members that frame into the section in such a manner as to effectively restrain the section against 
rotation and lateral displacement.  
 
6.4 Wall studs & wall stud assemblies  
The design capacity of a stud may be calculated in accordance with Section 3 (neglecting sheeting and using 
steel only) or on the basis that sheeting (attached to one or both  sides of the  stud) produces lateral and 
rotational support to the stud in the plane of   the  wall,  provided  that the stud,  sheeting,  and attachments  
comply  with the following:  
(a) Both ends of the stud shall be braced  to restrain rotation about the longitudinal stud axis  
and horizontal displacement perpendicular to the stud axis. However, the ends may or 
may not be free to rotate about both axes perpendicular to the stud axis. The sheeting DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  ciii 
  shall be connected to the top and bottom members of the wall assembly to enhance  the 
restraint  provided  to the stud and stabilize  the overall  assembly.  
If intermediate braces such as noggings (dwangs) are used for stability at points along 
the wall stud for systems either with or without  sheeting, they shall  be connected  to  the 
stud so as to resist lateral and torsional deformation of the stud at the points of 
connection.  
(b) If sheeting is used for stability of the wall studs, the sheeting shall retain its capacity and  
stiffness for t he expected service life of the wall and additional bracing shall be provided 
for the required structural integrity during constructio n and in the completed structure.  DKS  2971 : 2022  
civ © KEBS 2022  – All rights reserved  
 5 S E C T I O N  5  - C O N N E C T I O N S    
7.1 General  
Any suitable fastening system, such as welding, bolti ng, screwing, riveting, clinching, nailing , structural 
adhesive or other mechanical means, may be used  to join component  parts.  
Connec tion elements consist of members, connection components (cleats, gusset plates, brackets, connecting 
plates) and conn ectors (welds, bolts, screws, rivets, clinches, nails, adhesives). The connections in a structure 
shall be proportioned so as to be consist ent with the assumptions made in the analysis of the structure and to 
comply with this Section. Connections shall be capable of transmitting the design action effects [design action] 
calculated from this  analysis.  
Design capacities of specific connections may be obtained by prototype  testing  in accordance  with Section  8. 
 
7.2 Welded Connections  
7.2.1  General  
This Clause applie s to welded connections for cold-formed steel structural members  in which  the weld  is 
produced  by the arc welding  or resistance  welding  process es. 
 
Arc-welded connections, where at least one of the connected parts is less that 3mm thick, or  less than 
2.5mm thick for fillet welds, shall be in accordance with AS/NZS 1554.7. The arc weld design  capacities  
shall be determined in accordance with Claus es 7.2.2 to 7.2.6, as appropriate.  
 
Arc-welded connections, where each connected part is greater than or equal  to 3 mm thick , or greater than 
or equal to 2.5 mm thick for fillet welds, shall be   in  accordance  with AS/NZS 1554.1 or AS/NZS 1554.2, 
as appro priate. The arc weld design capacities shall be determined  in accordance  with AS 4100  or NZS 
3404,  as appro priate.  
 
Resistance welds shall be in accordance with AWS C1.1 or AWS C1.3, as appropriate. The resistance weld 
design capacities shall be determined  in accordance with Clause 7.2.7. 
NOTES:  
1 For high-strength  cold-rolled  steel,  reference  should  be made  to Clause  1.5.1.4  for design 
strength reduction near welds.  
2 AS/NZS  1554.1  requires  designers  to specify  the required  weld  category,  these  being  
either GP (general purpose) or SP (structural purpose), and any associated non -
destructive examination  requirements.  
 
7.2.2  Butt welds  
7.2.2.1  Tension or compression  
The design tensile or compressive force  (N*w) normal to the area of   a  butt  weld  shall  satisfy  
 
                                                                                                                     ...7.2.2.1 
 
where 
φ     = capacity reduction factor of a butt   weld  in  tension  or  compression  (see  Table 1.6)  
 
The nominal tensile or compressive capacity of a butt weld, welded from one or both sides, shall be 
determined as follows :  
 
                                                                                                                                         ...7.2.2. 2 
where  
 
lw       =  length of the full size of the weld  
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  tt         = design  throat thickness of a butt weld as defined in AS/NZS 1554.1 
 
fy       = yield  stress used in design for the lower strength base steel  
 
7.2.2.2  Shear  
The design shear force (V w * ) on a butt weld shall satisfy — 
 
                                                                                                          ...7.2.2.2 (1) 
where 
φ     = capacity  reduction factor of a butt weld in shear (see Table 1.6)  
Vw    = nominal  shear capacity of a butt weld  
 
The design shear capacity (φVw) of a butt weld shall be the lesser of the following:  
 
(a) 
                                                                                                 ...7.2.2.2( 2) 
    (b) 
                                                                                                          ...7.2.2.2( 3) 
 
where f uw is the nominal tensile strength of the weld metal.  
 
7.2.3  Fillet  welds  
7.2.3.1  General  
A fillet weld subject to a design shear force (V * ) shall satisfy — 
                                                           ...7.2.2. 3.1 
where 
φ     =  capacity redu ction factor of a fillet weld (s ee Table 1.6)  
Vw    =  nominal shear capacity of a fillet weld  
The design   shear  capacity  (φVw) of  a  fillet  weld  shall  satisfy  Clauses 7.2.3.2,  7.2.3.3 and 7.2.3.4  
 
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 7.2.3.2  Longitudinal Loading  
For lon gitudinal loading, φVw shall be determined as follows from the lesser of Items  (a)(i)  
and (b)(i), or the lesser of Items (a)(ii) and (b)(ii), as applicable, as follows:  
  
(a) (i)For  
                                                                              ...7.2. 3.2. (1) 
(ii)  
                                                                            ...7.2.3.2. ( 2) 
(b)   (i)  For  
                                                                                     ...7.2.3.2. ( 3) 
(ii) 
                                                                                        ...7.2.3.2. ( 4) 
 
For Grade  G450   steel  specified  in  AS 1397,  the  capacity  factor  of  0.55  shall  b e  used 
throughout Clause 7.2.3.2.  
 
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  7.2.3.3  Transverse  loading  
For transverse loading, φVw shall be determined as follows:  
φ  = 0.60  
Vw = t1lw fu1; or                                                                                                  . . .7.2.3.3(1)  
= t2lw fu2                                                                                                             . . .7.2.3.3( 2) 
 
where 
t1, t2  = thickness  of the two connecting plates of the tensile strengths f u1 and fu2, respectively (see 
Figures 5 .2.3(a) and (b))  
 
lw  = length  of fillet weld  
 
fu1, fu2    = tensile strength used in   the  design  of  the  two  connecting  plates  of  the thi cknesses 
t1 and t 2, respectively  
 
 
 
 
 
 
 
7.2.3.4  Longitudinal and transverse  loading  
For longitudinal and transverse lo ading, or both, φ Vw shall be determined as follows : 
For t ≥ 2.5 mm  
φ     = 0.60  
Vw    = 0.75t t lw fuw                                                                                                                  . . . 7.2.3.4(1)  
where 
tt                 = design  throat thickness of the weld (see Figure 5.2.3)  
             = 0.707t w1 or 0.707t w2, whichever is the smaller                                                      . . . 7.2.3.4(2)  
tw1, tw2    = leg lengths of fillet weld  
lw          = length  of fillet weld  
fuw         = nominal  tensile strength of weld  metal  
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 A larger design throat thickness than those calculated using Equation 7.2.3.4(2) shall be permitted if 
measurement shows that the welding procedure used consistently  yields the larger value. Arc spot welds 
(puddle  welds)  
7.2.3.5  General  
Arc spot welds (see Figure 5.2.4(A)) apply to welding sheet steel to thicker supporting members in  the  
flat position or  sheet to  sheet in the flat position. Arc spot welds shall not  be made on  steel where the 
thinnest connected part is  greater than 3 mm  thick, nor  through  a combination  of steel  sheets  having  
a total thickness  greater  than 3 mm. 
Weld w ashers (see Figures 5.2.4(B)) shall be used if the thickness of the sheet is less th an 
0.7 mm. Weld washers sha ll have a thickness between 1.3 and 2.0 mm with a minimum 
prepunched hole of 10 mm diameter.  
Sheet to sheet welds do not require weld washers.  
Arc spot welds shall be specified by the minimum effective diameter of the fused area (de) 
(see Figure  5.2.4(A)).  The minimum  effective  diameter  shall  be 10 mm. 
 
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 7.2.3.6  Shear  
The design shear force (V w*) on an arc spot weld shall sa tisfy— 
                                                                                                         . . . 7.2. 4.2(1) 
where 
φ     = capacity  reduction factor of an arc spot weld in shear (see Table 1.6)  
Vw    = nominal  shear capacity of an arc spot weld  
 
The design shear capacity   (φVw) of  each  arc  spot  weld  between  sheet  or  sheets,  and 
supporti ng  member  shall   be  the  lesser   of  Item (a)  and  whichever  is  appl icable   of Items 
(b)(i), (ii) and (iii), as follows:  
 
(a) φ = 0.60  
                                                                                               . . . 7.2.4.2( 2) 
 
(b) (i)   
                                                                            . . . 7.2.4.2( 3) 
 
(ii) 
                                                   . . . 7.2.4.2( 4) 
(ii) 
                                                                          . . . 7.2.4.2( 5) 
 
where 
 
de   = effective  diameter of fused area (see Figures 5.2.4(A))  
=  (0.7dw − 1.5tc) ≤ 0.55dw                                                                       . . . 7.2.4.2(6)  
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  dw     = visible  diameter of outer surface of arc spot weld  
E = Young’s  modulus of elasticity (200  × 103 MPa)  
da   = average  diameter of an arc spot weld at mid-thickness of  tc (see Figure 5.2.4(A)  
 
=  (d w − tc)    for a single sheet                                                                    . . . 7.2.4.2(7)  
=  (dw − 2tc)  for multiple sheets                                                                 . . . 7.2.4.2(8)  
(Not more than four lapped sheets over a supporting member)  
 
tc    = total  combined base steel thickness of sheets (exclusive of coatings) involved in 
 shear   transfer   above   the   plane   of   maximum   shear   tr ansfer   (see Figure 
5.2.4(B)(b)  
 
NOTE: If it can be shown by measurement that a given weld procedure will consistently 
give a larger effective diameter (de) or average diameter (da), as applicable, this larger 
diameter may be used provided the particular welding procedure used for making those 
welds is followed.  
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 7.2.4  Tear  out 
A connected part shall have a spacing between arc spot welds and an edge distance (e) from an 
arc spot weld such that the design shear force (V w* ) transmitted by the weld satisfies — 
 
                                                                                                    . . . 7.2.4. 3(1) 
where 
 
φ     = capacity  reduction factor of the connected part of an arc spot weld in shear  (see Table 1.6)  
 
 
 
Vw    = nominal  shear force transmitted by the weld  
=  tefu                                                                                                                     . . . 7.2.4.3(2)  
t      = thickness  of the thinnest connected sheet  
e     = edge  distance measured in the line of the force fro m centre -line of an arc spot weld to the 
nearest edge of an adjacent weld or to the end of the connecte d part toward which the force is 
directed (see Figures 5.2.4(C)(a) and (b))  
 
 
 
 
FIGURE   5.2.4(C)    EDGE DISTANCE FOR  ARC SPOT  WELDS  DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  cxiii 
  In addition, the edge d istance (e) from the centre -line of any weld to the end or boundary of the 
connected member sha ll be not less than 1.5dw. In no case shall the clear distance of welds and 
the end of member be less than 1.0dw.  
 
7.2.4.1  Tension  
The design tensile force (N w*) on an arc spot weld shall satisfy — 
                                                                                               . . . 7.2.4. 4(1) 
The design tensile capacity ( φNw) of each   arc  spot  weld  between  sheet  and  supporting 
member shall be determined as follows:  
φ     = 0.65  
Nw    = nominal  tensile capacity of an arc spot weld  
 
= 0.7tdafu                                                                                                          . . . 7.2.4.4(2)  
The following additional limitations for use in Equation 7.2.4.3 shall apply:  
e      ≥  d w 
fuw    ≥ 410  MPa 
fu       ≤ 410  MPa 
t  ≤ 0.7  mm 
NOTE: If it can be shown by measurement that a given weld procedure wil l consistently give a  
larger average diameter (da), this larger diameter may be used provided the particular welding 
procedure used for making those welds i s followed.  
 
The effects of any eccentric loading on an arc spot weld subject to uplift tension load , e.g., an  arc  
spot  weld  on  the  perimeter  of  a  roof  or  floor  system,  shall  be  evaluated  and considered 
within the design of the weld.  
7.2.5  Arc seam  welds  
7.2.5.1  General  
Arc seam welds (see Figure 5 .2.5.1) apply only to the following connections:  
(a) Sheet  to thicker  supporting  member  welded  in the flat position.  
(b) Sheet  to sheet  welded  in the horizontal  or flat position.  
 DKS  2971 : 2022  
cxiv © KEBS 2022  – All rights reserved  
 7.2.5.2  Shear  
The desi gn shear force (V w * ) on an arc seam weld shall satisfy — 
                                                                                                                                          . . . 7.2. 5.2(1) 
where 
φ  =  capacity reduction factor of an arc seam weld in shear (see Table 1.6)  
Vn = nominal  shear capacity of an arc seam weld  
The design shear capacity (φVn) of an arc seam weld shall be the lesser of the following:  
(a)   
φ = 0.60  
 
 
(b) 
 
where 
de   = effective  width of an arc seam weld at fused surfaces  
= 0.7d w − 1.5 t                                                                                              . . . 7.2.5.2(4)  
dw = width  of an arc seam weld  
lw   = length of the full size of the  weld  not  including  the  circular  ends.  For calculation purposes, 
lw shall not exceed 3 dw 
t    = thickness  of the thinnest connected part  
da   = average  width of arc seam weld  
=  d w − t     (for single sheet)                                                                    . . . 7.2.5.2(5)  
=  dw − 2t   (for double sheet)                                                                   . . . 7.2.5.2(6)  
 
7.2.5.3  Tearout  
The design tearout capacity (φ Vw) of the connected part based on the edge distance ( e) (see Figure 5.2. 5.3) 
shall be determined as for the arc spot weld specified in Clause 7.2.4.3.  DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  cxv 
  
 
 
7.2.6  Flare  welds  
7.2.6.1  General  
Flare welds (see Figure 5.2.6(a), (b) and (c)) apply only to the following  connections welded in any 
position:  
(a) Sheet to sheet for flare V-welds.  
(b) Sheet to sheet for flare-bevel  welds.  
(c) Sheet to thicker steel member for flare-bevel  welds.  
7.2.6.2  Shear  
The design shear force (V w *) on a flare weld shall satisfy — 
                                                                                                        . . .7.2.5.2( 1) 
where 
φ = capacity  reduction factor of flare welds subject to transverse and longitudinal loading (see 
Table 1.6)  
Vw = nominal  shear capacity of a flare weld  
 
The design  shear capacity (φVw  ) of a flare weld shall be the least of the followi ng values:  
(a)     For flare -bevel welds, subject to transverse loading (see Figure 5.2.6(a)):  
 φ     = 0.55  
 Vw    =  0.833tlw fu                                                                                                . . . 7.2.6.2(2)  
(b)     For flare welds, subject to longitudinal loading ( see Figure 5.2.6(b), (c), (d), (e), (f)  and (g)):  
 (i)      For t ≤ tw < 2t or if the lip height is less than lw:  
 φ     = 0.55  
 Vw    =  0.75tl w fu                                                                                                  . . . 7.2.6.2(3)  
 (ii)     For tw ≥ 2t and the lip height is greater than or equal to lw:  
 φ     = 0.55  
 Vw    = 1.5tlw fu                                                                                                . . . 7.2.6.2(4)  DKS  2971 : 2022  
cxvi © KEBS 2022  – All rights reserved  
 (c) For longitudinal and transverse loading: For t ≥ 2.5 mm:  
 For t ≥ 2.5 mm:  
 φ     = 0.60   
 Vw    = 0.75tw lw fuw                                                                                           . . . 7.2.6.2(5)  
where 
tw   = design  throat thickness of the weld [see Figure 5.2.6(d), (e), (f) and (g)]  
= (5/16) R                  for flare bevel weld filled flush to the surface                                   . . . 7.2.6.2( 6) 
= (1/2) R or (3/ 8) R   if R > 12.0 mm for flare V -weld fille d flush to the surface; or           . . . 7.2.6.2( 7)  
= effective  throat thickness of flare weld not filled flush  to surfac e 
= 0.707 w1 or 0.707 w2, whichever is smaller  
R  =  radius of outside bend surface  
 
 
7.2.7  Resistance  welds  
The design shear force (V w*) on a resistance weld shall satisfy — 
                                                                                                . . . 7.2. 7(1) 
   where 
    φ = capacity  reduction factor of the resistance weld (see Table 1.6)  
    Vw = nominal  shea r capac ity of the resistance weld  
  The design shear capacity (φVw) shall be determined as follows:  
(a) For spot welds, the design shear capacity (φVw) shall be as follows:  
φ = 0.65 
Vw = 5.51t1.47 (kN)      for 0.25 mm ≤ t < 3.56 mm                                                             . . . 7.2.7( 2) 
7.6t + 8.5 7 (kN) for  3.56 mm ≤ t < 4.57 mm                                                                    . . . 7.2.7( 3) 
t    = thickness  of thinnest outside sheet, in millimetres  DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  cxvii 
  
 DKS  2971 : 2022  
cxviii  © KEBS 2022  – All rights reserved  
  
 
 
7.3 Bolted Connections  
7.3.1  Gener al 
This Clause applies to bolted connections for cold-formed steel structural members  in which the thickness 
of a connected part is less than 3 mm. For bolted connections in which  the thickness of a connected part is 
greater than or equal to 3 mm, EN 1993 -1-1, as appropriate, shall be used.  
Bolts shall be installed and tightened to achieve  the required  performance  of the connections involved 
under service  conditions.  
Standard holes for bolts shall not exceed the sizes given in Table 5.3.1, except that large r holes may be 
used in column base details or structural systems connected to concrete  provided  special  plate  washers  as 
specified  in EN 1993 -1-1 are used.  
Oversized and slotted holes given in Table  5.3.1 may be used , provided all bolts are loaded in  shear  and 
bolt holes comply  with the following:  
(a) Slotted holes The length of slotted  holes  shall  be normal  to the direction  of the shear  
force.  
(b) Purlins and girts for Australia In situations where lapping or nesting of sections is 
required, such as purlin and gir t applications, it is permissible to have oversized short -
slotted holes provided integral washers are used with the bolt head and nut, all bolts are 
loaded in shear and the length of  slotted holes are normal to the direction of  the shear  
force.  The dimen sion of such  oversized -slotted  holes  shall  be— 
(df + 6.0)mm by ( df + 10.0)mm  
(c) Z-section purlins and girts for New Zealand In situations where lapping or nesting is 
required, such as purlin and girt applications, it is permissible to  have short -slotted 
holes provided all bolts are loaded in  shear, washers or  backup plates  are  installed  
and bolts tightened to achieve the required performance of the connection. The 
dimension of such short -slotted holes shall  be— 
(df + 2.0)mm by ( df + 10.0)mm  
Washers and b ackup plates shall be installed over oversized or short -slotted holes, or long - slotted holes in an 
outer ply, unless suitable performance is demonstrated by load tests in accordance with Section 8.  
 
 DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  cxix 
  
 
When holes are staggered, the area to be deducted shall be the greater of —  
(i)      the deduction for non -staggered holes; or  
(ii)     the sum of the areas of all holes in any zig -zag line extending progressively across  the member or part of 
the member, less    for each gauge space i n the chain of  holes.  
 
where 
 
sp   = staggered pitch, the distance  measured parallel to the direction of   the design  action  in  the  member,  
centre -to-centre  of  holes  in  consecutive lines (see Figure 5.3.1(A))  
 
t    = thickness  of the holed material  
sg   = gauge , the distance measured at right angles to the direction of the design act ion in the member, centre -
to-centre of holes in consecutive lines (see Figure 5.3.1(A))  
 
For sections such as angles with holes in both legs, the gauge shall be taken as  the sum of the back marks to 
each hole, less the leg thickness (see Figure 5.3.1(B))  
 
 
 
DKS  2971 : 2022  
cxx © KEBS 2022  – All rights reserved  
 
 
 
 
 
 
 DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  cxxi 
  7.3.2  Tearout  
A connected part shall have a spacing between bolts and an edge distance from a bolt such tha t the 
design shear force (V w*) of the connected part satisfies — 
 
                                                                                                                     . . . 7. 3.2(1) 
where  
φ  =  capacity reduction factor of bolted connection subject to tearout (see Table  1.6) 
 
 
 
 
Vf  =  nominal shear capacity of the connected part along two parallel lines in the direction of the applied 
force  
 
=  t efu                                                                                                                                     . . . 7.3.2(2)  
t    = thickness  of the connected part  
e   =  distance measured in the line of force from the centre of a standard ho le to the nearest edge of an 
adjacent hole or to the end of the connected part  
 
In addition, the minimum distanc e between centres of bolt holes shall provide clearance for bolt heads, 
nuts, washers and the wrench but shall be not less than 3 times the nomina l bolt  diameter (df). Also, the 
distance from the centre of an−y standard hole to the end or other boundary of  the connecting member 
shall be not less than 1.5df.  
 
For oversized and slotted holes, the distance between edges of two adjacent holes and the dista nce 
measured from the edge of the hole to the end or other boundary of the connecting  
member in the line o f force shall be not less than [e  (dh/2)], in which e is the distance  
used in Equation 5.3.2(2), and dh  is the diameter of a hole given in Table 5.3.1.  The clear  
distance between edges of two adjacent holes shall be not less than 2df  and the distance be tween the 
edge of the hole and the end of the member shall be not less than df.  
 
7.3.3  Net section  tension  
The design tensile force    (N * f ) on  the  net  section  of  the  connected  part  shall  satisfy Clause 3.2 
and— 
 
                                                                                                                   . . . 7.3. 3(1) 
where 
φ = capacity  reduction factor of  bolted connection   subject  to net section  tension (see Table 1.6)  
Nf = nominal  tensile capacity of the net section of the connected part  
 
The design tensile capacity (φNf) of the connected part shall be determined as follo ws: 
(a) Where washers are provided under both the bolt head and the nut — 
φ = 0.65 ( for double shear connection)  
φ = 0.55 ( for single shear connection)  DKS  2971 : 2022  
cxxii © KEBS 2022  – All rights reserved  
 
  for a single bolt, or a single row of bolts perpendicular  to the force.   . . 7.3.3( 2) 
                   for multiple bolts in the line  parallel to the force                                             . . 7.3.3( 3) 
    
(b) Where either washers are not provided  under the   bolt  head  and  nut,  or  only  one washer is 
provided under either the bolt head or nut — 
φ = 0.65 
 
 for a single bolt, or a single row  of  bolts  perpendicular to the force  . . 7.3.3( 4) 
  for multiple bolts in the line pa rallel to the force                                                                 . . 7.3.3( 5) 
  
where 
sf    = spacing  of bolts perpendicular to the line of the force; or  width of sheet, in the case of a single 
bolt 
An = net  area of the connected part  
 
7.3.4  Bearing  
7.3.4.1  General  
The design bearing capacity  (φVb) of bolted connections shall be determined in accordance with 
Clauses 7.3.4.2 and 7.3.4.3. For conditions not specified in this Standard, φ Vb of bolted connections 
shall be determined by tests.  
 
7.3.4.2  Bearing capacity without considering bolt hole  deformat ion 
When deformation around the bolt holes is not a design consideration, the nominal bearing capacity 
(Vb) of the connected sheet for each loaded bolt shall be determined as follows:  
 
                                                                                         . . 7.3.4.2 
where 
 
φ = 0.60  
α   = modification  factor for type of bearing connection given in Table 5.3.4.2(A)  
C = bearing  factor given in Table 5.3.4.2(B)  
df   = nominal  bolt diameter  
t    = base  metal thickness  
fu   = tensile  strength of sheet  
 
 
DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  cxxiii  
  
 
 
7.3.4.3  Bearing  capacity  at a bolt hole deformation  of 6 mm 
When deform ation around a bolt hole is a design consideration, the  nominal  bearing  capacity (Vb) 
shall be determined as follows:  
 
                                                                                         . . 7.3. 4.3 
7.3.5  Bolts  
7.3.5.1   Bolt in  shear  
The design shear force (V *fv) on a bolt shall satisfy  
 
where 
 
φ = capacity  reduction factor of a bolt subject to shea r (see Table 1.6)  
Vfv = nominal  shear capacity of a bolt  
 
                                                                                      . . 7.3. 5.1 
fuf = minimum ten sile strength of a bolt  
=   400 MPa    Grade 4.6 bolts)  
=   830 MPa     Grade 8.8 bolts)  
nn = number of shear planes with threads intercepting the shear plane  
Ac = minor diameter area of a bolt AS 1275  
nx = number of shear planes without threads interceptin g the shear plane  
Ao = plain shank area of a bolt 
DKS  2971 : 2022  
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7.3.5.2  Bolt in  tension  
The design tensile force (N *ft ) on a bolt shall satisfy — 
                                                                                                        . . 7.3.5. 2(1) 
 
where 
 
φ = capacity  reduction factor of a bolt subject to tension (see Table 1.6)  
Nft = nominal  tensile capac ity of a bolt  
=  As fuf                                                                                                              . . . 7.3.5.2(2)  
As =  tensile stress area of a bolt, as specified in AS 1275  
The pull -over (pull -through) capacity of the connect ed sheet at the bolt head, nut or washer shall 
be considered where bolt tension is involved.  
7.3.5.3  Bolt subject to combined shea r and tension  
A bolt required to resist simultaneously a design shear force (V *fv) and a design tensile force  
(N*ft) shall satisfy — 
 
                                                                               . . . 7.3.5. 3 
Where V*fv,φVfv,and  φN ft  shall  be  determined  in  accordance  with  Clauses 7.3.5.1  
and 7.3.5.2, respectively.  
7.4 Scre wed Connections  
7.4.1  General  
This Clause applies to connections for cold -formed steel structural members using self - tapping screws of 
nominal diameter (df) where 3.0 mm ≤ df ≤ 7.0 mm. The screws shall be thread -forming or thread -cutting, with 
or without a self -drilling point.  
7.4.2  Screwed connections in shear  
7.4.2.1  Minimum spacing and edge  distance  
The distance between centres of  screws shall provide clearance for screw washers but shall   be not 
less than three  times  the nominal  screw  diameter  (df). 
The distance from the centre of a screw to the  edge of  any part shall be  not  less than 1.5df. If the 
end distance is parallel to the force on the fastener, the nominal shear capacity  (Vfy) shall  be limited  
to that calculated  using  Equation  7.4.2.4(2).  
DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  cxxv 
  7.4.2.2  Tension in the connected  part 
The design tensile force  (N*t ) on  the  net  section  of  the  connected  part  shall  satisfy  
Clause 5.2 and — 
]                                                                                                   . . . 7. 4.2.2(1) 
where 
φ    = capacity reduction factor of   screwed  connection  subject  to  tension  (see  
Table 1.6)  
Nt     = nominal  tensile capacity o f the net section of the connected part  
 
= (2.5df  Sf )A nfu ≤ A nfu for  a  single  screw, or a single row of screws perpendicular to the forc e                  .  . . 7.4.2.2(2)  
=  A n fu                                           for  multiple  screws  in  t he  line parallel to the force                                 .  . . 7.4.2.2( 3) 
     df   = nominal  screw diameter  
Sf   = spacing  of screws perpendicular to the line of the force; or  width of sheet, in the case of a  
single screw  
An = net  area of the conne cted part  
 
7.4.2.3  Tilting and hole  bearing  
The design bearing force (V b*) on a screw shall satisfy — 
                                                                                                           .  . . 7.4.2. 3(1) 
where  
φ = capacity  reduction factor of a screw, subject to tilting and hole bearing (see  
Table 1.6)  
Vb = nominal  bearing capacity of the connected part  
Where the screw is in a single shear connection and where the two connected sheets are in contact at 
the point  of fastening — 
(a) for t2/t1 ≤ 1.0, Vb shall be taken as the smallest of the following:  
                                                                                        ….7.4.2.3(2)  
                                                                                                 ….7.4.2.3( 3) 
                                                                                                  ….7.4.2.3( 4) 
where  
t2    = thickness  of the sheet not in contact with the screw head  
 
t1    = thickness  of the sheet  in contact with the screw head  
 
df   = nominal  screw diameter  
 
fu2 = tensile  strength of the sheet not in contact with the screw head  
 
fu1 = tensile  strength of the sheet in contact with the screw head  
 
C =  bearing factor (see Table 5.4.2.3)  
 
     (b)     for t 2/t1 ≥ 2.5, V b shall be taken as the smaller of the following:  
 
                                                                            ….7.4.2.3( 5) 
DKS  2971 : 2022  
cxxvi  © KEBS 2022  – All rights reserved  
 
                                                                      ….7.4.2.3( 6) 
(c)  for 1. 0 < t2/t1 < 2.5, Vb    shall  be  determined  by  linear  interpolation  b etween  the minimum 
values obtained from Equations 7.4.2.3(2) to 7.4.2.3(4) and the minimum values obtained from Equations 
7.4.2.3(5) and 7.4.2.3(6).  
 
For cases where the material is not in contact at the point of fastening, the screw capacity  
[strength] sha ll be determined by testing in accordance with Section 8  
 
 
 
 
7.4.2.4  Connection  shear  as limited  by end distance  
The design shear force (V * fv) as limited by end distance shall satisfy — 
                                                                                            ….7.4.2. 4(1) 
If fu/fy ≥ 1.08, φ = 0.7  
If fu/fy < 1.08, φ = 0.6  
When the distance to an end of the connected part is parallel to the line of the applied force, the 
nominal shear force shall be calculated as follows:  
                                                                                            ….7.4.2.4( 2) 
where 
t    =  thickness of the part in which the end distance is measured  
e   =  distance measu red in the line of force from the centre of a standard hole to the nearest end 
of the connected part  
7.4.2.5  Screws in  shear  
The nominal shear capacity of the screw shall be determined by testing in accordance with Section 8 and 
shall be not less than 1.25 Vb, where Vb shall be calculated in accordance with Clause 7.4.2.3. 
7.4.3  Screwed connections in tension  
7.4.3.1  Minimum edge  distance  
The distance from the centre of the screw in tension to the edge of any part shall not be less than 3df. 
7.4.3.2  Pull-out and pull -over (pull-through)  
This Clause applies only to screwed connections in  tension if  the  two  sheets are in  contact at the 
point of fastening. For other cases, such as crest fixed connections, the design tensile capacity  shall  
be established  by prototype  testing  in accordance  with Section  8. 
The design tensile force (N *t) on a screw shall satisfy — 
                                                                                                 ….7.4. 3.2(1) DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  cxxvii  
  where  
φ  =  0.5  
Nt  =  nominal capacity of the connection in tension  
The no minal capacity (N t) shall be the lesser of the following:  
(a) The nominal pull -out capacity (N ou) calculated as follows:  
Nou = 0.85t 2df fu2   for t2 > 0.9 mm                                                            . . . 7.4.3.2(2)  
(b) The nominal pull -over (pul l-through) capacity (N ov) calculated as follows:  
Nov = 1.5t 1dw fu1     for 0.5 < t 1 > 1.5 mm                                                  . . . 7.4.3.2(3)  
where d w  is the greater of the screw head diameter and the washer diameter, but not greater t han 
12.5 mm.  
 
For screws subject to tensile fo rces, the head of the screw or washer  shall have a  
diameter (dw) not less than 8 mm. Washers  shall  have  a minimum  thickness  of 1.27 
mm. 
 
7.4.3.3  Screws in  tension  
The nominal tensile capacity of the screw shall be determ ined by testing in accordance with Section  8 
and shall be not less than 1.25Nt, where Nt shall be calculated in accordance with Clause  5.4.3.1.  
For screws  not covered by  AS 3566, the tensile capacity of  the screw shall be determined   by 
testing.  
 
7.5 Blind  Riveted Connections  
7.5.1  General  
This Clause applies to connections for cold-formed steel structural members using  blind rivets of nominal 
diameter ( df), where 3.0 mm ≤ df ≤ 7.0 mm. 
 
7.5.2  Riveted connections in shear  
7.5.2.1  Minimum spacing and edge  distance  
The distance between centres of rivet holes shall be not less than 3 times the nominal blind rivet 
diameter  (df). 
The distance from the centre of a rivet to the edge of any part shall be not less than 1.5df. If the end 
distance is parallel to the force on the fastener,  the nominal shear capacity  (Vfv) shall  be limited  to 
that calculated  using  Equation  5.5.2.4(2).  
The distance from the centre of a rivet to the edge of any part sha ll be not less than  3df. 
7.5.2.2  Tension in the connected  part 
The design tensile force ( N*t ) on  the  net  section  of  the  conn ected  part  shall  satisfy  
Clause 3.2 and — 
 
                                                                                            . . . 7. 5.2.2(1) 
where  
φ  =  capacity reduction factor of b lind rivet connection subject to net section tension  
(see Table 1.6)  
Nt  =  nominal tensile capacity of the net section of the connected part  
 
 
  for a single rivet, or a single row of rivet perpendicular to the force           . . . 7. 5.2.2(2) 
       for multiple rivets in the line parallel to the force                                    . . . 7.5.2.2( 3) 
 df   = nominal  rivet diame ter 
DKS  2971 : 2022  
cxxviii  © KEBS 2022  – All rights reserved  
  sf    = spacing  of rivets perpendicular to the line of the force; or  width of width of sheet, in the case of a single rivet  
 An =  net area of the connected part  
 
7.5.2.3  Tilting and hole  bearing  
The design bearing force (V * ) on a rivet shall satisfy — 
                                                                                            . . . 7.5.2. 3(1) 
where  
φ  =  capacity re duction factor of a blind rivet subject to tilting and hole bearing (see  
Table 1.6)  
Vb =  nominal bearing capacity of the connected part  
Where the rivet is in a single shear connection and where the two connected sheets are in contact 
at the point of faste ning— 
(a) for t 2/t1 ≤ 1.0, V b shall be taken as the smallest of the following:  
        
                                                           . . . 7.5.2.3( 2) 
                                                             . . . 7.5.2.3( 3) 
                                                              . . . 7.5.2.3( 4) 
where  
t1    = thickness  of the sheet in contact with the rivet head  
t2    = thickness  of the sheet not in contact with the rivet head  
df   = nominal  rivet diameter  
fu1 = tensile  strength of the sheet in contac t with the rivet head  
fu2 = tensile  strength of the sh eet not in contact with the rivet head  
 
(b) for t 2/t1 ≥ 2.5, V b shall be taken as the smaller of the following:  
                                                            . . . 7.5.2.3( 5) 
                                                         . . . 7.5.2.3( 6) 
(c)  for 1.0  < t2/t1 < 2.5,  V b   shall  be  determined  by  linear  interpolation  between  the minimum 
value  obtained  from  Equations 7.5.2.3(2)  to 7.5.2.3(4)  and  the  minimum value obtained from 
Equations 7.5.2.3(5) and 7.5.2.3(6).  
 
For cases where the material is not in contact at the point  of fastening, the rivet capacity  shall  be 
determined  by testing  in accordance  with Section  8. DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  cxxix  
  7.5.2.4  Connection shear as limited by tearout   
The design shear force (V *fv) as limited by end distance shall satisfy — 
 
                                                                                            . . . 7.5.2. 4(1) 
When the distance to an end of the conne cted part is parallel to the line of the applied force, the 
nominal shear force shall be calculated as follows:  
                                                                                               . . . 7.5.2.4( 2) 
where 
φ =  capacity   reduction   factor   of   riveted   connection   subject   to   tension   (see  
Table 1.6)  
t    = thickness  of the part in which the end distance is measured  
e   = distance  measured in the line of force from the centre of a standard hole to the nearest end 
of the connected part  
 
7.5.2.5  Rivets in shear  
The nominal shear capacity of the rivet shall be determined by testing and shall be not less  than 
1.25Vb, where  Vb shall  be calculated  in accordance  with Clause  7.5.2.3.  
NOTE: The design tensile capaci ty of riveted connection s may be established by prototype 
testing in accordance with Section 8.  
 
7.6 Rapture  
7.6.1  Shear rupture  
At beam -end connections, where one or more flanges are coped and failure may occur a long a plane 
through the fasteners, the design shear force (V *n) shall satisfy — 
                                                                                                                         . . . 7. 6.1(1) 
where  
φ = capacity  reduction factor of beam -end connections subject to shear rupture (see  
Table 1.6)  
Vn = nominal  shear capacity of the beam -end connection  
                                                                                                                  . . . 7.6.1( 2) 
Awn  =  net area of the web  
                                                                                                                . . . 7.6.1( 3) 
dwc   = coped  depth of the web  
nh      = number  of holes in the critical plane  
dh      = diameter  of the hole  
t      = thickness  of the coped web  
7.6.2  Tension  rupture  
The nominal  tension rupture strength along a path in affected elements of connected  members  shall  be 
determined  by Equation  5.2.1(2)  with kt equal  to 1.0. 
 
7.6.3  Block shear  rupture  
At beam -end or tension connections with possible shear and tension rupture plane s, the  design action 
effect (S*) shall  satisfy — DKS  2971 : 2022  
cxxx © KEBS 2022  – All rights reserved  
 
                                                                                                          . . . 7.6. 3(1) 
where  
φ = capacity  reduction factor for bl ock shear rupture of the beam -end or tension member connection  
=      0.65 for bolted connections  
Rn = nominal  capacity for block shear rupture of the beam -end or tension member connection  
 
The nominal  capacity for   block  shear  rupture  of  the  beam -end  or  tension  member connection (R n) 
shall be de termined as follows:  
                                             . . . 7.6.3( 2) 
                                             . . . 7.6.3( 3) 
where 
Ant    = net  area subject to tension in block shear rupture  
Anv   = net  area subject to shear in block shear rupture  
Agv   = gross  area subject to shear in block shear rupture  
Agt    =  gross area subj ect to tension in block shear rupture  
 
7.7 Other Conne ctions using any type of Fasteners  
The design capacity for a specific connection using any type of fasteners  may be determined  by prototype 
testing in accordance with Section  8. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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  SECTION 8 – FATIGUE  
8.1 General   
8.1.1  Requirements  
This Sec tion applies to the design of cold-formed steel members and connections subject to cyclic loading 
within the elastic range stresses of frequency and magnitude sufficient to initiate cracking and progressive 
failure  (fatigue).  
The provisions of this Section  apply to stresses calculated on the basis of unfactored loads.  The maximu m 
permitted  tensile  stress  due to unfactored  loads  is 0.6fy. 
Stress range is defined as the magnitude of change in stress due to the   application  or  removal of the 
unfactored live load. In the case of a stress reversal, the stress range shall be compute d as the sum of the 
absolute values of maximum repeated tensile and compressive stresses or the sum of the absolute values 
of maximum shearing   stresses  of  opposite direction at the point of probable crack  initiation.  
The occurrence of full design wind or earthquake loads is too infrequent to warrant consideration of fatigue 
design in buildings. The fatigue design of cladding, fixing s and its immediate support shall be in 
accordance  with AS/NZS 1562.1. Wind -induced oscillations can  cause fatigue cracks to occur in 
structures such as masts, lighting poles, traffic sign supports and chimneys, and, therefore, shall be 
considered.  
Evalua tion of fatigue resistance to this Section is not r equired if the number of cycles of application of live load 
is less than  20 000.  
The cyclic load resistance determined by the provisions of this Section is applicable to - 
(a) structures with suitable corrosion  protection or subject only to non-aggressive atmos pheres;  
and 
(b) structures subject to temperatures not exceeding 150°C. The contract document shall provide  
either — 
(i) complete details including weld sizes;  or 
(ii) specify the planned cycle life and the maximum rang e of moments, shears  
and  reactions for the  connec tions.  
8.1.2  Definitions  
For the purpose of this Section, the definitions belo w apply.  
8.1.2.1  Constant stress range fatigue  limit 
The highest constant stress range for each detail category at which fatigue cracks are n ot expected to 
propagate (see Figure 6.3).  
8.1.2.2  Cut-off limit 
For each detail category, the highest variable stress range that does  not require  consideration  
when  carrying  out cumulative  damage  calculations  (see Figure  6.3).  
8.1.2.3  Design  life 
The period over which a structure or structural element is required to perf orm its function without repair.  
8.1.2.4  Design  spectrum  
The sum of the stres s spectra from all of the nominal loading events expected during the design  life. DKS  2971 : 2022  
cxxxii  © KEBS 2022  – All rights reserved  
  
 
8.1.2.5  Detail  category  
A designation given to a particu lar detail to  indicate which of  the  S-N curves is  to  be  used in the 
fatigue  assessment.  
NOTES:  
1 The detail category ta kes into consideration the local stress concentration at the 
detail, the   size and shape of the maximum acceptable discontinuity, the loading 
condition, metallurgical  effects, residual st resses, the welding process and any 
post weld improvement.  
2 The detai l category number is defined by the fatigue strength at 2 × 106 cycles on 
the S-N curve (see Figure  6.3). 
 
8.1.2.6  Discontinuity  
An absence o f material, causing a stress concentration.  
NOTE: Typic al discontinuities include cracks, scratches, corrosion pits, lack o f penetration, slag 
inclusions, cold laps, porosity and undercut.  
8.1.2.7  Fatigue  
Damage caused by repeated fluctuations of stress leading t o gradual cracking of a structural element.  
8.1.2.8  Fatigue  loading 
A set of nominal loading events described by the distribution of the loads, their magnitudes and the 
numbers  of applications  of each  nominal  loading  event.  
 
8.1.2.9  Fatigue  strength  
The stress range defi ned in Clause 6.3 for each detail category varying with t he number of stress cycles 
(see Figure 6.3).  
 
8.1.2.10  Miner’s  summation  
The cumulative damage calculation based on the Palmgren –Miner summation or equivalent.  
 
8.1.2.11  Nominal loading  event  
The loading sequence for the structure or structural element.  
NOTE: One nominal loading event may produce one or more stress cycles depending on 
the  type of load and the point in the structure under consideration.  
 
8.1.2.12  S-N curve  
A curve defining the limiting relationship between the number of stress cycles and stress range  for a 
detail  category.  
 
8.1.2.13  Stress  cycle  
One cycle of stress defined by stress cycle counting.2  
 
8.1.2.14  Stress cycle counting  method  
Any rational method used to identify individual stress cycles from the stress history.  DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  cxxxiii  
   
8.1.2.15  Stress range  
The algebraic difference between two extremes of stress.  
 
8.1.2.16  Stress  spectrum  
A histogram of the stress cycles produce d by a nominal loading event . DKS  2971 : 2022  
cxxxiv  © KEBS 2022  – All rights reserved  
  
 
8.1.3  Notation  
For the purpose of this Section, the following applies:  
fc        = fatigue  strength corrected for thickness of material  
ff        = uncorrected  fatigue strength  
frn      = detail  category reference fatigue strength at nr -normal stress  
frnc    = corrected  detail category reference fatigue strength for normal stress  
frs       = detail  category reference fatigue strength at nr -shear stress  
frsc     = cor rected  detail category reference fatigue strength for shear stress  
fy        = yield  stress  
f3        = detail  category fatigue strength at constant amplitude fatigue limit (5 × 106 cycles)  
f3c      = corrected  detail category fatigue strength at constant amplitude fatigue limit  
f5        = detail  category fatigue strength at cut off limit ( 108 cycles ) 
f5c      = corrected  detail category reference fatigue strength at cut off limit  
f *       = design  stress range  
fi       = design  stress range for loading e vent i  
l      = length  of member  
ni       = number  of cycles of nominal loading event i, producing fi  
nr       = reference  number of stress cycles (2 × 106 cycles)  
nsc     = number  of stress cycles  
tp        = plate  thickness  
αs       = inverse  of the slop e of the S -N curve  
βtf      = thickness  correction factor  
φ     = capacity  factor  
 
8.1.4  Method  
For the reference design c ondition, the capacity factor (φ) shall be taken as 1.0.  The  reference design 
condition implies the following:  
(a) The detail is located on a redundant load path, in a position where failure at that point 
alone  will not lead to overall  collapse  of the structu re. 
(b) The stress history is estimated by conventional  methods.  
(c) The load cycles are not highly  irregular.  
(d) The detail is access ible for, and sub ject to, regular inspection.  
The capacity factor (φ) shall be reduced when any of the above conditions do not apply . For 
non-redundant load paths, the capacity factor (φ) shall be less than or equal to 0.70.  
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  8.1.5  Thickness  effect  
The thickness correction factor (β tf) shall be taken as — 
βtf = 1.0  
except for a transverse fillet or butt-welded connection involving a plate thickness   (tp)  
greater  than 25 mm, where  βtf shall  be calculated  as follows:  
                                                                                                          . . . 8.1.5(1) 
The uncorrected fatigue strength (ff) shall be reduced to a corrected fatigue strength (fc)  
using — 
                                                                                                               . . . 8.1.5( 2) 
The uncorrected detail category reference fatigue strength for normal stress (f rn) shall be  
reduced to   a  corrected  detail  category  reference  fatigue  strength  for  normal stress  (f rnc) 
using — 
                                                                                                               . . . 8.1.5( 3) 
The uncorrected detail category fatigue s trength at constant amplitude fatigue limit (f 3) shall  
be reduced to a corrected detail category fatigue strength at co nstant amplitude fatigue limit  
(f3c) using — 
                                                                                                             . . . 8.1.5(3)  
The uncorrected detail category fatigue strength at constant  amplitude fatigu e limit (f3) shall  
be reduced to a corrected detail category fatigue strength at constant amplitude fatigue limit  
(f3c) using — 
 
                                                                                                               . . . 8.1.5(3)  
The uncorrected detail category fatigue strength at cut -off limit (f5) shall be reduced to a  
corrected detail categ ory reference fatigue strength at cut -off limit (f5c) using — 
                                                                                                                . . . 8.1.5(3)  
   
8.2 Calculation of Maximum Stresses & Stress range  
Calculated stresses shall be based on elas tic analysis. Stresses shall not be   amplified  by stress concentration 
factors for geometrical  discontinuities.  
For bolts and threaded rods subject to axial tension, the calculated stresses shall include the effects of prying 
action, if applicable.  
In th e case of axial stress combined with bending, the maximum stresses, of each kind, shall  be those 
determined for concurrent arrangements of applied  load.  
For members having symmetric cross -sections, the fasteners and welds shall be arranged symmetrically ab out the 
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 axis of the member, or the total stresses including those due to eccentricity s hall be includ ed in the calculation of 
the stress range.  
For axially stressed angle members, where the centre of gravity of the connecting welds lies between the line of  the 
centre of gravity of the angle cross -section and the centre of the connected leg, the effects of  eccentricity shall be 
ignored. If the centre of gravity of the connecting welds lies outside this zone, the total stresses, including those 
due to joint e ccentricity, shall be included in the calculation of stress range.  
 
 
8.3 Detail Categories for Classified  Details  
For cold-formed sections, the detail categories to be used for the various  constructional details are given in 
Table  6.3(A).  
In the classificatio n method, the detail category is a  designation given to  a  particular detail  to indicate which 
of the S -N curves shown in Figure 6.3 shall be used in fatigue assessment. The detail category shall be the 
nominal stress range corresponding to 2 × 106 cycles on a fatigue strength curve of a given construction  detail.  
The fatigue strength cur ves for the di fferent detail categories are defined by — 
(a) log(nsc) = log(a) − 3log( ff), for nsc ≤ 5 ×  106 
(b) log(nsc) = log(a) − 5log( ff), for 5 × 106 < nsc ≤ 108 
where  
nsc = number of stress cycles  
log(a) = constant which depends on the related part of the slope (see Table 6.3(B))  
ff = uncorrected fatigue  strength  
The values of the constant (log( a)) for the different parts of  the fatigue strength S -N curves,  as  well as  the 
constant stress range fatigue limit and cut-off limit for each detail category    are given in Table  6.3(B).  
The welds in the welded details given in Table 6.3 (A) for Detail Categories 118 and below shall conform with 
Category SP as specified in AS/NZS 1 554.1.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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TABLE   6.3(A)  
DETAIL CATEGORY CLASSIFICATION FOR  
COLD -FORMED ST EEL MEMBERS AND CONNECTIONS  
 
Stress 
category  Detail 
category  Construction details  
Illustration  Description  
I 174  
 
 
 
  
  
Detail Category  I Non-welded products:  
As-received base metal 
and components with as - 
rolled surfaces,  
including sheared edges 
and cold-formed  corners  
II 118  
 
  
 
 
 
  
Detail Category II  Members connected by 
continuous longitudinal 
welds:  
As-received base metal 
and we ld metal in 
members connected by 
continuous longitudinal 
welds loaded in shear  
III 81  
 
 
 
 
 
  
  
  
 
 
 
 
 
 
  
 
 
  
 
 
Detail Category III  Welded attachments and 
bolt or  screw  
connections:  
(a) and (b ) Welded 
attachments to a plate or a 
beam, transverse fillet 
welds and continuous 
fillet welds loaded in 
shear less than or equal to 
50 mm  
(c) Bolt and  screw 
connections and spot 
welds  
IV 55  
 
 
 
  
  
 
 
  
 
 
  
Detail Category IV Longitudinal fillet - 
welded attachments:  
Longitudinal fillet - 
welded attachments 
greater than 50 mm 
parallel to the direction 
of the applied stress,  and 
intermittent welds 
parallel to the direction 
of the applied  force  
where  
DKS  2971 : 2022  
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 stress  category  I: non-welded products  
stress  category  II: members connected by continuous 
longitudinal welds str ess category  II: welded attachments and 
bolt or screw connection s stress  category  II: longitudinal 
fillet-welded  attachments  
 
 
 
TABLE   6.3(B)  
VALUES FOR DEFINING FA TIGUE STRENGTH CURVES FOR 
DIFFERENT DETAIL CATEGORIES  
 
 
Detail 
category  Log( a) for 
nsc ≤ 5 × 106 
(αs = 3) Log( a) for 
5 × 106 ≤ nsc ≤ 108 
(αs = 5) Constant stress range 
fatigue limit, f3 
MPa  Cut-off limit,  
f5 
MPa  
174 13.0197  17.2335  128 70 
118 12.5146  16.3916  87 48 
81 12.0197  15.5668  59 33 
55 11.5146  14.7249  40 22 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
FIGURE 6.3 FATIGUE STRENGTH CURVES FOR DIFFERENT DETAIL CATEGORIES  
 
DKS 2971 : 2022  
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  8.4 Fatigue Assement  
8.4.1  Constant stress  range  
The design stress range (f *), at any point in the structure subject  only  to  constant stress range cycles, 
shall  satisfy — 
 
                                                                                                                          ….8.4.1 
 
8.4.2  Variable  stress  range  
The design stress range (f *), at any point in the structure at which the stress range varies, shall satisfy 
the following:  
 
(a) Normal stresses  
                                            ….8.4. 2(1) 
 
(b) Shear stresses  
 
                                                                                     ….8.4. 2(2) 
where — 
 
(i)      the summation Σi is for i design stress ranges (fi ) for which φf3c < fi   ;  
(ii)     the summation Σj is for j design stress  ranges (fi ) for which φf sc ≤ fi <φf3c   
; and  
(iii)    the summation Σi is for i design stress ranges (fi) for shear stre sses φf3c < f *k    
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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cxl © KEBS 2022  – All rights reserved  
 ⎝ ⎠ SECTIO N 9 – DIRECT STRENGTH  METHOD  
9.1 General  
This Section applies to the determination of the nominal  axial compression ( N) and bending( M) capacities of cold -
formed steel members.  
Clauses 9.2.1 and 9.2.2 provide a method applicable to all cold-formed steel compres sion members and 
members subject to bending. Those members meeting the geometric and material  limitations of Clause 9.1.1 for 
compression members and Clause 9.1.2 for members subje ct to bending have been pre-qualified for use, and 
the calibrated φ factors given in Clauses 9.2.1 and 9.2.2 apply. Other compression members and members 
subject to bending shall use the provisions of Clauses 9.2.1 and 9.2.2 but the φ factors for   rationa l  analysis 
given in Clause 1.6.3(c) shall  apply.  
The direct stren gth method does not provide explicit provisions for members in shear, combined bending and shear, 
web crippling, combined bending and web crippling, or combined axial load and bending (beam -column). Further, no 
provisions are given for structural assemblie s or connections and joints. The provisions of Sections 2, 3 and 4, when 
applicable, shall be used for all cases.  
For members or situations that are not applicable to Sections 2, 3 and 4, extensions to the  direct strength 
method may exist. Extensions to the direct strength method are subject to the same provisions as any other 
rational analysis procedure specified in Clause 1.6.3(c). The applicable provisions of Sections 2, 3 and 4 shall be 
met when they exist and the reduced φ factors  shall  be used  for the design  capacity  when  rational  analysis  is 
conducted.  
 
9.1.1  Pre-qualified compression  members  
Unperforated compression members that fall within the geometric limitations given in Table  7.1.1 have been 
pre-qualified and shall be permitted to be designed using the   φ  factors given in Clause  7.2.1.1.  
 
9.1.2  Pre-qualified members subject to bending  
Unperforated members subject to bending that fall within the geometric limitations given in Table 7.1.2  have 
been pre-qualified and shall be permitted to be designed using the φ factors  given in Clause  7.2.2.1 . 
 
9.1.3  Elastic  buckling  
Analysis is required for determining the elastic buckling loads or moments, or both, used in this Section. For 
compression mem bers, this includes the local and distortional and overall buckling loads s pecified in Clause 
7.2.1. For members subject to bending, this includes the local and distortional and overall buckling moments 
specified in Clause 9.2.2. For a given compression me mber or members subject to bending, all three modes 
may not exist. In this case , the non -existent mode shall be ignored in the calculations of Clauses 9.2.1 and 
9.2.2. 
 
9.1.4  Deflection  calculation  
The bending deflection at any moment (M) due to nominal loads,  shall be permitted to be determined by 
reducing the gross second moment of area (Ig) to an effective second moment  of area (Ieff) for deflection,  
using the following equation : 
 
 
                                                                                                           …...9.1.4  
 
 
where  
Mn = nominal flexural capacit y specified in Clause 9.2.2, but with My replaced by  
M in all equations of Clause  9.2.2 
M = moment due to nominal loads on member to be considered ≤ My 
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9.2 Members  
9.2.1  Design of compression  members  
9.2.1.1  General  
The nominal member capacity of a  member in  compression (Nc) shall be  the minimum of  the nomin al 
member capacity of a member in compression (Nce) for flexural, torsional or flexural -torsional buckling , 
the nominal member capacity of a member in compression (Ncl) for local buckling and the nominal 
member capac ity of a member in compression (Ncd) for distortional buckling as specified in Clauses 
9.2.1.2, 9.2.1.3 and 9.2.1.4. For compression members meeti ng the geometric requirements of Table 
7.1.1, φc shall be  taken as  0.85. For all other  compression  members,  φc specified  in Clause  1.6.3(c)(i)  
appli es. 
9.2.1.2  Flexural, torsional or flexural -torsional  buckling  
The nominal member capacity of a member in compression ( Nce) for flexural, torsional or flexural -torsional 
buckling shall be calculated as follows:  
                                                                                      …...9. 2.1.2 (1) 
                                                                                    …...9.2.1.2 ( 2) 
where  
λc   = non -dimensional slenderness used to determine N ce 
                                                                                               …...9.2.1.2 ( 3) 
Noc   = least   of  the  elastic  compression  member  buckli ng  load  in  flexural, torsional and flexural -
torsional buckling  
                                                                                                                                …...9.2.1.2 ( 4) 
Ny = nominal  yield capacity of the member in compression  
                                                                                                                                …...9.2.1.2 ( 5) 
 
 
9.2.1.3  Local  buckling  
The nominal member capacity of a me mber in compression (Ncl) for local buckling shall be calculated as 
follows:  
                                                                                                …...9.2.1. 3(1) 
 
                                    …...9.2.1.3( 2) 
where 
λl       =   non -dimensional slenderness used to determine N cl 
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                                                                                           …...9.2.1.3( 3)  
Nol    =   elastic local buckling load  
                                                                                                                          …...9.2.1.3( 4) 
  
 
9.2.1.4  Distortional  buckling  
The nomin al member capacity of a member in comp ression ( Ncd) for distortional buckling 
shall be calculated as follows:  
                                                                          …...9.2.1. 4(1) 
               …...9.2.1.4( 2) 
where  
λd      =   non -dimensional slenderness used to determine N cd 
                                                                                                      …...9.2.1.4( 3)  
Nod   =   elastic distortional compression member buckling load  
                                                                                                                  …...9.2.1.4( 4) 
 
9.2.2  Design of members subject to  bending  
9.2.2.1  General  
The nominal member moment capacity (Mb) shall be the minimum of the nominal member moment 
capacit y (Mbe) for lateral -torsional buckling , the nominal member moment capacity (Mbl) for local 
buckling and the nominal member moment capacity (Mbd) for distortional buckling as specified in Clauses 
9.2.2.2, 9.2.2.3 and 9.2.2.4. For members  subject  to  bending , meeting the geometric requirements of 
Clause 9.1.2, φb shall be taken as  0.90. For all other  members  subject  to bending,  φb specified  in 
Clause  1.6.3(c)(i)  applies.  
9.2.2.2  Lateral-torsional  buckling  
The nominal member moment capacity (Mbe) for lateral -torsiona l buckling shall  be  calculated as 
follows:  
 
                                                        …...9.2. 2.2(1) 
 
                              …...9.2.2.2( 2) 
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                                                          …...9.2.2.2( 3)  
where  
Mo    =  elastic lateral -torsional buckling moment as defined in Clause 5.3.3.2  
                                                                                                       …...9.2.2.2( 4) 
where  
Zf       = full  section modulus  of the extreme fibre at first yield  
 
9.2.2.3  Local  buckling  
The nominal member moment capacity (Mbl) for local buckling shall be calculated   as  follows:  
For λ l ≤  0.776:   Mbl = Mbe ................................ ................................ ................  9.2.2.3(1)  
              …...9.2.2. 3(2) 
where 
λl       =   non -dimensional slenderness used to determine M bl 
                                                                               …...9.2.2.3( 3) 
Mol   =   elastic local buckling moment  
                                                                                       …...9.2.2.3( 4) 
 
9.2.2.4  Distortional  buckling  
The nominal member moment capacit y (Mbd) for distortional buckling shall be calculated as follows : 
                                                                    …...9.2.2. 4(1) 
                  …...9.2.2.4( 2) 
where  
λd       =  non - dimensional slenderness used to determine Mbd  
                                                                                                        …...9.2.2.4( 3) 
Mod  =  elastic distortional buckling moment  
                                                                                                                    …...9.2.2.4( 4) 
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  TABLE   7.1.1  
LIMITS FOR PRE -QUALIFIED COMPRESSION MEMBERS  
 
Sectio n Geometric limitation  
Lipped channel  d/t < 472 
b1/t < 159 
4 < d1/t < 33 
0.7 < d/bf < 5.0 
0.05 < d1/b1 < 0.41 
θ = 90° 
E/fy > 340 ( fy < 593 MPa)  
Lipped channel with we b stiffener(s)  d/t < 489 
b1/t < 160 
6 < d1/t < 33 
1.3 < d/b1 < 2.7 
0.05 < d1/b1 < 0.41 
One or two intermediate stiffeners  
E/fy > 340 ( fy < 593 MPa)  
Z-section  d/t < 137 
b1/t < 56 
0 < d1/t < 36 
1.5 < d/b1 < 2.7 
0.00 < d1/b1 < 0.73 
θ = 50°  
E/fy > 590 ( fy < 345 MPa)  
Rack upright  d/t < 51 
b1/t < 22 
5 < d1/t < 8 
2.1 < d/b1 < 2.9 
1.6 < b2/d1 < 2.0 (b2 = small outstand parallel to b1) 
d2/d = 0.3 ( d2 = second lip parallel to d1) 
E/fy = 340 ( fy < 593 MPa)  
Hat 
 
 
 
 d/t < 50 
b1/t < 20 
4 < d1/t < 6 
1.0 < d/b1 < 1.2 
d1/b1 = 0.13  
E/fy > 428 ( fy < 476 MPa)  
r/t < 10, where r is the centre -line radius  
 
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TABLE   7.1.2  
LIMITS FOR PRE -QUALIFIED MEMBERS SUBJECT TO BENDING  
 
Section  Geome tric limitation  
Channels  d/t < 321 
b1/t < 75 
0 < d1/t < 34 
1.5 < d/bf < 17.0 
0.0 < d1/b1 < 0.70 
44° < θ < 90° 
E/fy > 421 ( fy < 483 MPa)  
Lipped channels with web stiffener  d/t < 358 
b1/t < 58 
14 < d1/t < 17 
5.5 < d/b1 < 11.7 
0.27 < d1/b1 < 0.56 
θ = 90°  
E/fy > 578 ( fy < 352 MPa)  
Z-section  d/t < 183 
 
 b1/t < 71 
 
 10 < d1/t < 16 
2.5 < d/b1 < 4.1 
 0.15 < d1/b1 < 0.34 
 36° < θ < 90° 
 E/fy > 400 ( fy < 462 MPa)  
Hats (decks) with stiffened flange in 
compression  d/t < 97 
b1/t < 467 
 0 < d1/t < 26 
 0.14 < d/b1 < 0.87 
 0.44 < b1/2d1 < 2.0 
 0 < n ≤ 4 
 
 E/fy = 492 ( fy < 414 MPa)  
Trapezoids (decks) with  stiffened flange in 
compression  d/t < 203 
b1/t < 231 
 
 42 < (d/sinθ)/b1 < 1.91 
 0.55 < d/2d1 < 1.69 
 0 < nc ≤ 2 (nc = number of compression flange 
stiffeners)  
              0 < nw ≤ 2 (nw = number o f web stiffeners/folds)  
 0 < nt ≤ 2 (nt = number o f tension flange stiffeners)  
 52° < θ < 84° 
 E/fy > 310 ( fy < 655 MPa)  DKS  2971 : 2022  
cxlvi © KEBS 2022  – All rights reserved  
 r/t < 10, where r is the centre -line radius  DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  cxlvii  
  SECTION 10 – T E S T I N G  
10.1 Testing for determining Material Properties  
10.1.1  Testing of unform ed steel  
Where the steels specified in Clause 1.5.1 .2 are used or the  yield stress of steel is required  for the 
purpose of Clause 6.1.3, unformed steel properties shall be determined by tests in accordance with AS 
1391.  
Test specimens shall be taken longi tudinally (long dimension of specimens in direction  of rolling) from 
positions located one quarter of the coil width from either edge near the outer end of the coil. 
10.1.2  Compression  testing  
Stub -column tests shall be made on flat-end specimens whose length is not less than three times the 
largest dimension of the section but no more than 20 times  the least radius of gyration. If tests of 
ultimate compressive strength are used to determine yield stress for  quality control purposes, the 
length of the section sha ll be not less than 15 times the least radius of gyration.  
In  making compression tests,  the specimen in  the testing machine shall be  centred so that  the load is 
applied  concentrically  with respect  to the centroidal  axis of the section.  
10.1.3  Testing of full sections  
This Clause applies only to the determinati on of the mechanical properties of a fully formed section for 
the purposes specified in Clause 1.5.1.3. It shall not be interpreted as forbidding  the use of test 
procedures  instead  of the usual  design  calculations.  
The procedure shall be as follows:  
(a) Deter mine  the tensile  yield  stress  (fy) in accordance  with AS 1391.  
(b) Determine the compressive yield stress ( fy) by means  of compression  tests  as 
specified in Clause  8.1.2.  
(c) Where the principal effect of the loading to which the member will be subjected in 
servic e is to produce bending stresses, determine the yield stress for the flanges. 
In determining the yield stress, carry out tests on specimens cut from the section. 
Each such specimen shall consist of one complete flange plus a portion of the web 
of such  flat width ratio so that the section is fully effective.  
(d) For acceptance and control purposes, make two full section  tests  from  formed  
material lots. Material lots shall be considered as parcels or heats as defined in the 
relevant Standard’s material speci fication in the Clauses on  selection  and 
preparation  of test samples for mechanical  testing.  
(e) Use either tension or compression tests for routine acceptance and control purposes, 
provided it is demonstrat ed that such tests reliably indicate the yield  stress  of  the 
section  when  subjected  to the kind of stress  under  which  the member  is to be 
used.  
 
 
10.1.4  Testing of flat coupons of formed  members  
10.1.4.1  Assessment of strength  increase  
Tests for determining material pr operties of flat coupons of formed members and  mate rial properties of 
unformed steel for  the purpose of assessing strength increase resulting from cold -forming, as specified in 
Clause 1.5.1.3, shall be made as follows:  
(a) The yield stress of flats (fyf) shall  be established by  means of  a  weighted aver age of  
the yield stresses of standard tensile coupons taken longitudinally from the major 
flat portions of a cold-formed member. The weighted average shall be the sum of 
the products of the average yield stres s for each major flat portion times  its  cross- DKS  2971 : 2022  
cxlviii  © KEBS 2022  – All rights reserved  
 k 2 + k 2 f m sectional  area,  divided  by the total area of the major  flats in the cross -section.  
(b) If the actual yield stress of the unformed steel exceeds the specified minimum yield 
stress, the yield stress of the  flats (fyf) shall be adjusted by multiplying the test 
values  by the ratio of the specified minimum yield stress to the actual yield stress of 
the unformed  steel.  
10.1.4.2  Design  properties  
Tests for determining material properties of flat coupons of formed  members  for  the purpose  of  
establishing  design  prope rties  of  the  formed  members,  as  spec ified  in Clause 1.5.1.2, shall be 
made as follows:  
(a) The test specimens shall be taken longitudinally from a major flat portion of  the 
section, midway between corners (excluding the corners) or midway between a 
corner and a free edge (excluding the corner) . 
(b) The test specimen shall be taken from the flat portion with the least strength increase 
from cold-forming.  
(c) The minimum yield stress ( fy) and the minimum tensile stren gth ( fu) used in design  
shall be determined in accordance with AS  1391.  
10.1.5  Testing for determining section  properties  
Flexural section properties, e.g., second moment of area of the cross -section and section modulus, may be 
determined by tests.  
Test specimen s prone to lateral displacement shall be suita bly braced.  The loading  apparatus and 
bracing shall not impose unintentional restraints on  the  specimen.  The  loading devices shall be 
accurately  calibrated.  
The specimens shall be tested in bending with simply supported spans.  
The cross -sectional dimen sions  of test specimens shall be as close as practicable to nominal dimensions, 
which are the basis for calculated properties. Where a discrepancy exists, the se ction properties from tests 
shall be adjusted by the ratios of nominal to actual dimensions.  
The true deflections shall be separated from other  causes  of  specimen  movement  under load,  such  as 
specimen  settlement  at support,  and movement  of test frame.  
10.1.6  Testing of single -point fastener  connections  
The testing of single -point fastener connections shall be in accordance with Appendix F.  
 
10.2 Testing for Assessment or Verification  
10.2.1  General  
This Clause applies to prototype units of complete structures, parts of s tructures, individual  members or 
connections for design verification.  
The methods of test shall  be in accordance with AS/NZS1170.0, as an alternative to calculation.  
The methods do not apply to the testing of structural models nor to the establishment of g eneral design  
criteria.  
10.2.2  Coefficient of variation of structural  characteristics  
The coefficient of variation of structural characteristi cs (Vsc) refers to the variability of the  total population 
of the production units. This includes the total population v ariation due to fabrication  (kf) and material  (km). 
It can be approximated  as follows:  
Vsc  = . . . 8.2.2  
10.2.3  Design capacity of specific products and assemblies  
The design capacity (Rd) of a specific product or a specific assembly may be established by proto type DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  cxlix 
  testing of that specific product or assembly. The design capacity ( Rd)  shall  satisfy — 
 
 
wher e Rmin. is the minimum value of the  test results and kt is as given in Table 8.2.3.  
Testing  of  sheet  roof and wall cladding  systems  shall  be   in  accord ance   with   
AS/NZS  1562.1.  
 
 
 
TABLE   8.2.3  
FACTORS ( kt) TO ALLOW FOR VARIABILITY OF STRUCTUR AL UN ITS 
 
No. of 
units to be 
tested  Coef ficient of variation of structural 
characteristics ( Vsc) 
5% 10%  15%  20%  25%  30%  
1 1.20 1.46 1.79 2.21 2.75 3.45 
2 1.17 1.38 1.64 1.96 2.36 2.86 
3 1.15 1.33 1.56 1.83 2.16 2.56 
4 1.15 1.30 1.50 1.74 2.03 2.37 
5 1.13 1.28 1.46 1.67 1.93 2.23 
10 1.10 1.21 1.34 1.49 1.66 1.85 
100 1.00 1.00 1.00 1.00 1.00 1.00 DKS  2971 : 2022  
cl © KEBS 2022  – All rights reserved  
  
APPENDIX A 
FLEXURAL MEMBERS SUBJECTED TO POSITIVE AND NEGATIVE BENDING  
(Informative)  
A1   GENERAL  
If the geometrical properties of flexural members are based on the effective design width accounting  for  flange  
curling  and  such  a  member is  subjected  to  positive  and  negative bending moments (e.g., in the case of a 
continuous beam or a rigid f rame), Paragraphs B2 and B3 may apply, subject to the limita tions specified in Paragraph 
B4. 
A2   LOAD -CARRYING CAPACITY  
The  bending  moments and  the  support  reactions  may  be  determined  assuming  constant section beams or 
frames, provided that th e ratio of section moduli for positive and negative bending  m oments does  not  exceed  the  
values  specified  in  Paragraph B4. The  maximum design  bending  moments  (M )  so  determined  should  not  
exceed  the  nominal  member moment capacity (Mb) ti mes φb.  
A3   DEFLECTIONS  
Deflections may be determined assuming constant section beams or frames, and are based on a mean second 
moment of area, provided that the ratio of second moments of area for positive and negative bending moment does 
not exceed th e value specified in Paragraph B4.  
A4   LIMITATIONS  
For the purpose of Paragraphs B2 and B3, the ratios of geometrical properties of a member for positive and negative 
bending moments, determined in accordance with this Standard, should not exceed the fo llowing: 
(a)     Section moduli:  
(i)      Continuous beams .................................................................................... 1.35.  
(ii)     Rigid frames..................................................................................... ........ 1.25.  
(b)Second moment of area:  
(i)      Continuous beams .................................................................................... 1.20.  
(ii)     Rigid frames............................................................................... .............. 1.16.  
For the purpose of this Paragraph, the section property with the greater value should be taken as the numerator of the 
ratio.  
For members with ratios outside the limits specified in Paragraph A4, a rational analysis approach may be deve loped 
based on testing.  
 
 
 
 
 
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© KEBS 2022 – All rights reserved  cli 
   
APPE NDIX  B 
PROTECTION  
(Informative)  
 
B1 SCO PE 
This Appendix applies to the protection of cold-formed structural members, including decking, cladding and 
structures.  
 
B2 PROTECTION AGAINST CORROSION  
B2.1 Members to be protect ed 
A member should be adequately protected against corrosive attacks, with due regard to environmental  
conditions.  
B2.2    Protective  coating  
The protective coating may be applied to steel sheet or strip, either before or  after  the forming of the 
members . The type of coating should be specified, after proper account has been taken of the use of the 
structure, climatic or other local conditions, maintenance provisions,  and the effect  of the formin g process  
on previously  applied  coatings.  
B2.3 Members made from uncoated steel  
A member made from uncoated steel should be protected b y a rust-inhibitive coating immediately after 
processing. The coating should possess a permanent adhesion to the steel. S ubsequent coatings, before 
or after assembly, should adequat ely adhere to, and be compatible with, the first coating. The type and 
quality of coatings and their application should comply with the recommendations of the appropriate 
sections of AS/NZS 2312. Coatings destroyed by welding, assembly, or by handling shou ld be restored as 
specified in Para graph  B4. 
B2.4 Members made from coated steel  
For a member made from coated steel, the coatings applied before forming should have adequate mechanical 
properties  and adhesion to the steel sufficient to withstand the formi ng process without damage or peelin g. 
NOTE: Recommendations  for corrosion protection  may  be  found  in  AS/NZS 2311  and AS/NZS 2312.  
 
B3 PROTECTION DURING TRANSPORT, HANDLING AND STORAGE  
B3.1 G eneral  
Structural members that have been distorted, and subse quently corrected, may be weakened   to  the extent 
that their structural integrity may be  impaired or  lost. Such members should   not be  used.  
B3.2 Transport and handling  
Structural members should be adequately protected during handling and transport to prevent damage. 
Units that are transported in nested bundles should be separable without damage to the units or their 
coatings. Care should be taken when handling long units or bundles. Consider ation should be given to the 
use of lifting beams with appropr iately spaced lifting points  and slings  or to lifting  with properly  space d 
forklift  tines.  DKS  2971 : 2022  
clii © KEBS 2022  – All rights reserved  
 B3.3 Storage  
Structural members should be protected from the weather. They should be stacked  clear of  the ground and 
protected by a waterproof covering. Ventilation  adequate to avoid condensati on should be ensured. If 
bundles become wet, the members should be separated, wiped  and placed  so that air circulation  
completes  the drying.  
 
B4 REPAIRS TO COATI NGS  
Coatings that have been damaged by welding or other causes sho uld be restored before the structure is put 
into service. The damaged  area should be dry and clean, free from dirt, g rease , loose or heavy scale or rust 
before the protective coating is applied. When preparing welded assemblies for painting, care should be  
taken that the area at and near welds is thoroughly cleaned down to base metal. The protective coating 
should be applied as soon as practicable and before noticeable oxidation of the clean surface occurs. 
Damaged zinc coating  should  be restored  with a suitable  zinc paint.  DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  cliii 
  APPEN DIX C 
DISTORTIONAL BUCKLING STRESSES OF GENERAL CHANNELS, LIPPED 
CHANNELS AND Z-SECTIONS IN COMPRESSION AND  BENDING  
(Normative)  
C1   GENERAL CHANNELS IN  COMPRESSION  
The elastic distortional buckling stress ( fod)  of  general  channe ls  in  c ompression  (see  Figure D1(a)) shall be 
determined as follows:  
                                                                                         C1(1)   
where  
 
                                                                                                       C1(2) 
 
                                                                                                                              C1(3)   
 
                                                                                                                          C1(4)  
                                                                                                                                    C1(5) 
                                                                                                                               C1(6) 
                                                                                                                                        C1(7) 
                                                                                                     C1(8) 
                                                                                                                                    C1(9) 
                                                                                                                                                       C1(10) 
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cliv © KEBS 2022  – All rights reserved  
 
                                                                                             C1(11) 
fod is obtained from Equation D1( 1) with — 
                                                                                                                                 C1(12) 
The values of A, Ix, Iy, Ixy, Iw are for the compression flange and lip alone.  
 
D2   SIMPLE LIPPED CHANNELS  IN COMPRESSION  
The elastic distortional buckling stress (f od) of simple lipped channels in compression (see  Figure D1(b)) shall be 
determined as f ollows:  
                                                                                               C2(1) 
where  
                                                                                                           C2(2) 
                                                                                                                                 C2(3) 
                                                                                                                        C2(4) 
                                                                                                                                      C2(5) 
                                                                                              C2(6) 
                                                                                                                                                         C2(7) 
 
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© KEBS 2022 – All rights reserved  clv 
  
                                                                                 C2(8) 
fod is obtained from Equation D2(1) with — 
                                                                                                                   C2(9) 
The values of  A, x, y, J, Ix , I y and I xy for  a  compression  flange  with  a  simple lip  are  as  follows:  
                                                                                                                                       C2(10) 
                                                                                                                                      C2(11) 
 
                                                                                                                               C2(12) 
                                                                                                                                      C2(13) 
                                                                                       C2(14) 
                                                                                    C2(15) 
                                                                                  C2(16) 
C3   SIMPLE   LIPPED   CHANNELS OR Z -SECTIONS IN BENDING ABOUT THE  AXIS PERPENDICULAR TO 
THE WEB  
The elastic distortional buckling   stress  (f od) of  simple  lipped  channels  or  Z -sections  in bending about the axis 
perpendicular to the we b (see Figure D1 (c)) shall be determined in accordance with Paragraph D2, except that — 
                                                                                                                             C3(1) 
                                                 C3(2) 
DKS  2971 : 2022  
clvi © KEBS 2022  – All rights reserved  
 fod is obtained from Equation C2(1) with — 
                                                                                                                        C3(3) 
If kφ is negative, kφ shall be calculated with   f’ud = 0 
If the bracing interval that fully restrains rotation of the flange and lip in the distortional mode  is  located  at  an  
interval  less  than  λ  obtained  from  Equation C3(1),  the  bracing interval shall be used in place of λ.  DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  clvii 
  
 
 
 
 
 DKS  2971 : 2022  
clviii © KEBS 2022  – All rights reserved  
 APPENDIX  D 
SECT ION PROPERTIES  
(Normative)  
E1   SHEAR CENTRE   DIST ANCE  (m), TORSION  CONSTANT  (J) AND WARPING CONSTANT (Iw)  
Values of m, J and Iw for certain sections are shown in Figure E1.  
For Iw  of sections other than those given in Figure E1, Iw  shall be taken as z ero for box sections.  
E2   MONOSYMMETRY SECTION CONSTANTS  
Monosymmetry section constants are calculated as follows:  
                                                                                                          D2(1) 
                                                                                                           D2(2) 
where the x -axis is the axis of symmetry (see Table E1) — 
                                                                                                                                                       D2(3) 
                                                                                                                    D2(4) 
NOTES:  
1    For doubly symmetric sections, βx  = 0 and βy  = 0.  
2 In the calculation of βy  using the value  of xo, determined from Table E1, xo and  x   are to be taken as negative.  
Where the y -axis is the axis of symmetry, interchange x and y in the equations fo r the x -axis of symmetry and Table 
E1. 
 
 
 
 
 
 DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  clix 
  
 DKS  2971 : 2022  
clx © KEBS 2022  – All rights reserved  
 NOTES TO FIGURE E1:  
1    For all open section:  J = ∑  bt3  .  
2    For members cold -formed from a single steel sheet of uniform thickness:   
width of the flat sheet.  =  wf t 3   , where wf   is the feed  
3    For the box and rectangle sections, Iw is negligibly small in comparison to J.  
 
 
 
 
 
 
 
 
 
 DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  clxi 
  APPEND IX  E 
STANDARD TESTS FOR SINGLE -POINT FA STENER CONNECTIONS  
(Normative)  
E1   SCOPE  
 
This Appe ndix sets out test methods to evaluate the structural performance of sin gle-point fastener  connections  and  
clinching.  The following   tests  shall  be  made  for  single -point fastener connections:  
(a)     Shear test (see Paragraph F3).  
(b)     Cross -tension tests (see Paragraph F4).  
E2   MATERIAL  
A specimen of the steel sh eet shall be tested in accordance with AS 1391 to determine its physical properties.  
E3   SHEAR TEST F3.1   General  
A specimen consisting of two strips of steel sheet, connected by a single fastener through overlapped ends, shall be 
evaluated for its capac ity to resist a tensile force.  
E3.2   Apparatus  
The following apparatus shall be used:  
(a)  Grips   Any device th at is capable of holding the ends of the test specimen in such a way as to ensure uniform 
loading. In addition, for test specimens where the th ickness at each end exceeds 2.0 mm, packing shims or adjustable 
grips shall be used to ensure central loading acr oss the lap joint.  
(b)  Loading device   Any suitable device that is capable of loading the grips uniaxially at a controlled rate.  
(c)  Instrum entation   Capable  of  measuring  a  force  applied  to  the  test  specimen  to  a minimum accuracy of ±1%, 
and displacement across the joint to a minimum accuracy of 0.02 mm.  
E3.3   Test specimen  
The test specimen shall consist of two strips of flat ste el joined by lapping the ends and fastening through the centre of 
the lapped area (see Figure F1). The strips shall be joined together flat and shall be free of any residue. The fastener 
shall be installed within 3.0 mm of its specified location and in acc ordance with the manufacturer’s recommendations or 
the actual site practice, as applicable.  
E3.4   Procedure  
The procedure for the shear test shall be as follows: (a)     Align the test specimen in the grips and clamp. (b)     Monitor  
load and displacement . 
(c)     Load the specimen at a controlled rate to ensure the test is completed within a 30 s to  240 s time  frame.  
(d)  Stop  the  test  once  the  maximum  load  has  been  reached  and  the  load  has  either dropped off, or the joint  has  
undergone a displacement  of 6.0 mm or the fastener diameter, whichever is greater.  
(e)     Record the maximum load and  mode of failure.  
E4   CROSS -TENSION TEST F4.1   General  
Specimens consisting of two strips of steel sheet, connected by a single fastener to form a cross, shall be evaluated for 
their capacity to resist a tensile force applied perpendicular to the plane of the specimen.  
E4.2   Apparatus  
The following apparatus shall be used:  
(a)     Holding jig   the jig for holding the cross -tension specimen is shown  in Figure F2.  
The attachment of the jig to the loading device shall allow for self -alignment.  
(b) Loading device    Any  suitable  device  that  is  capable  of  loading  the  halves  of  the  holding jig uniaxially at a 
controlled rate.  
 
 
 DKS  2971 : 2022  
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F4.3   Test s pecimen  
The test specimen consists of two strips of flat steel crossed and joined through the centr e with a fastener (see Figure 
G3). The strips shall be joined together flat and shall be free of any residue. The fastener shall be installed within 3 mm 
of its specified location  and in accordance  with  the  manufacturer’s  recommendations  or  the  act ual  site  practice,  
as applicable.  
F4.4   Procedure  
The procedure for the cross -tension test shall be as follows: (a)     Align the test specimen in the ho lding jig and clamp.  
(b)     Load the specimen at a controlled rate to ensure the test is complet ed within a 30 s to  
240 s time frame.  
(c)     Stop the test once the maximum load has been reached and the load has dropped off. (d)     Record the maximum 
load and mode of failure.  
F5   REPORT  
The following shall be reported:  
(a)     Number of this Au stralian/New Zealand Standard, i.e., AS/NZS 4600. (b)     Testing laboratory.  
(c)     Type of test, i.e., shear or cross -tension test.  DKS 2971 : 2022  
© KEBS 2022 – All rights reserved  clxiii 
  (d)     Type and properties of the fastener and method of installation. (e)     Type and properties of the sheet materia l. 
(f)      Duration of test.  
 (g)     Maximum load.  
(h)     Load -displacement curve.  
 (i)      Mode of failure.  DKS 2972: 2022    
 
© KEBS 2022 – All rights reserved   
 
 DKS  2971 : 2022  
ii © KEBS 2022  – All rights reserved