N E P A L  N A T I O N A L  B U I L D I N G  C O D E NBC 109 : 1994 MASONRY : UNREINFORCED Government of Nepal Ministry of Physical Planning and Works Department of Urban Development and Building Construction Babar Mahal, Kathmandu, NEPAL Reprinted : 2064 N E P A L  N A T I O N A L  B U I L D I N G  C O D E NBC 109 : 1994 MASONRY : UNREINFORCED This publication represents a standard of good practice and therefore takes the form of recommendations. Compliance with it does not confer immunity from relevant legal requirements, including bylaws तत्कलिन श्री X को सरकार (मन्त्रिपरिषद्) को मिति २०६०४१२ को निर्णयानुसार स्वीकृत Government of Nepal Ministry of Physical Planning and Works Department of Urban Development and Building Construction Babar Mahal, Kathmandu, NEPAL Reprinted : 2064
Preface
This Nepal Standard was prepared during 1993 as part of a project to prepare a  National Building Code for Nepal. In 1988 the Ministry of Housing and Physical Planning (MHPP), conscious of the growing needs of Nepal's urban and shelter sectors, requested technical assistance from the United Nations Development Programme and their executing agency, United Nations Centre for Human Settlements (UNCHS). A programme of Policy and Technical Support was set up within the Ministry (UNDP Project NEP/88/054) and a number of activities have been undertaken within this framework. The 1988 earthquake in Nepal, and the resulting deaths and damage to both housing and schools, again drew attention to the need for changes and improvement in current building construction and design methods. Until now, Nepal has not had any regulations or documents of its own setting out either requirements or good practice for achieving satisfactory strength in buildings. In late 1991 the MHPP and UNCHS requested proposals for the development of such regulations and documents from international organisations in response to terms of reference prepared by a panel of experts. This document has been prepared by the subcontractor's team working within the Department of Building, the team including members of the Department and the MHPP.  As part of the proposed management and implementation strategy, it has been prepared so as to conform with the general presentation requirements of the Nepal Bureau of Standards and Metrology. The subproject has been undertaken under the aegis of an Advisory Panel to the MHPP. The Advisory Panel consisted of :
Member Representative, Society of Nepalese Architects (SONA) Deputy Director General, Department of Building, (Mr. JP Pradhan) Member-Secretary The Subcontractor was BECA WORLEY INTERNATIONAL CONSULTANTS LTD. of New Zealand in conjunction with subconsultants who included : Golder Associates Ltd., Canada SILT Consultants P. Ltd., Nepal TAEC Consult (P.) Ltd., Nepal Urban Regional Research, USA Principal inputs to this standard came from : Mr. AM Tuladhar, DoB, HMGN Dr. AS Arya, Professor Emeritus, University of Roorkee, India Dr. RD Sharpe, BECA (Team Leader) Revisions and Updated to this code came from : Mr. Purna P. Kadariya, DG, DUDBC Mr. Kishore Thapa, DDG, DUDBC Mr. Mani Ratna Tuladhar, Sr. DIV. Engineer, DUDBC Mr. Jyoti Prasad Pradhan, Ex.DG, DOB Mr. Bhubaneswor Lal Shrestha, Ex. DDG, DOB Mr. Uttam Shrestha, Architect, Architects' Module Pvt. Ltd. Mr. Manohar Lal Rajbhandhari, Sr. Structural Engineer, Mr Associates Mr. Amrit Man Tuladhar, Civil Engineer, DUDBC
4.6 4.7
S General Requirements
6 7 8 Openings in Walls .
v 0.
Foreword
0.1
Design Aspect Covered
This Code of Practice covers the structural design aspect of unreinforced masonry elements in the buildings.  It also deals with some aspect of earthquake-resistant design of buildings. References to seismic zoning, seismic coefficients, important factors, structural performance factors and performance coefficient are as per NBC 105-94 Seismic Design of Buildings in Nepal.
0.2
Related Codes
This Code should be read in conjunction with the Indian Standard IS:1905-1987 Code of Practice for Structural Use of Unreinforced Masonry (Third Revision).
1
1.1
Coverage
This is a Code of Practice for the Structural Design Aspects of Unreinforced Masonry Buildings in Nepal.
1.2
Limitation
The recommendations of this Code of Practice do not cover walls constructed in mud mortar and should not be used for such case.
1.3
Provisions for Historical Buildings
The provisions of this Code of Practice shall be construed as advisory when being applied to the repair, alternations or additions necessary for the conservation, preservation, restoration, rehabilitation, reconstruction or continued use of buildings of historical, architectural, cultural or archaeological significance. 2
Interpretation
2.1
General
In this Code of Practice the word "shall" indicates a requirement that is to be adopted in order to comply with the Code of Practice, while the word "should" indicates recommended practice.
2.2
Terminology
BEDDED AREA means the area of surface of a masonry unit which is in contact with mortar in the plane of joint. CORBEL means one or more courses of brick projecting from a wall (such as a cornice), generally to form a support for wall plates, etc.  A brick should not project more than one quarter of its length beyond the next lower course. DEFINITIONS : The terminoloty given in Indian Standard IS:1905-1987 in clauses 2.1 to 2.21.3 will apply, except as stated here below. DIMENSION means the measured dimension of a designed item and, if used to describe masonry units, means the nominal dimension. INFILL PANEL means a wall framed on four sides by columns and beams and contributing to shear resistance in the plane of the frame, but which is not designed to resist vertical loads other than its own weight. 1 LATERAL SUPPORT means a masonry structure support which enables a masonry element to resist lateral load and/or restrains the deflection of the masonry element at the point of support. MASONRY means an arrangement of masonry units which may be brick, rectangularised stone, ashlar or cement blocks laid to a bond and joined together with mortar. MASONRY UNIT means an individual unit which is bonded to similar units with the help of mortar to form a masonry element such as a wall, column, pier, buttress, etc., and conforming to the Nepal Standard Brick Masonry NS: 1/2035. PANEL WALL means an exterior non load-bearing wall in framed construction wholly supported by beams and columns. PARTITION WALL means an interior non load-bearing wall which is separated so as not to be part of the seismic resisting structure. PARTY WALL means a wall built on land belonging to two adjoining owners, it being the joint property of both the owners. SLENDERNESS RATIO means the ratio of effective height or effective length to the effective thickness which ever is less. SR = Slenderness Ratio =

2.3
Symbols
The following letters, symbols and abbreviation are used for the purposes of this section and other symbols are specified at their respective places. A Area of section b Breadth of masonry unit or shorter dimension of a rectangular column DL Dead load E Modulus of elasticity e Eccentricity Jo Basic compressive stress Je Permissible compressive stress fd Compressive stress due to dead load Js Permissible shear stress K Stiffness of member ka Area factor kp Shape modification factor ks Stress reduction factor LL Live load l Axial load on a compression member leg Effective length or span m Modular ratio W Total load WL Wind load w Uniform distributed load Wp Breadth of crosswall, piers, or buttresses Z Modulus of section
3
Materials
3.1
Permissible Material
The materials used in masonry construction shall be in accordance with NBC 101-94 Marerial Specifications unless otherwise specified.
3.2
Masonry Unit
The specification and properties of the masonry shall conform to the Nepal Standard Brick Masonry NS: 1/2035. Its size is given below :

Table  3.1 :  Dimensions of a Nepal Standard Birck
Note : Length of Birck = 2 x Width of Birck + 1 Vertical Mortar Joint
3.3
Tolerances
Tolerance for First and Second Class bricks are as in given Tables 3.2. and 3.3
Table 3.2 :
Table 3.3 : Individual Brick Size and Length of 20 Bricks (Class B)
3.4
Classification of Bricks and Brickwork
3.4.1
First Class Brickwork
All the bricks used for masonry construction shall be thoroughly burnt, deep cherry red or copper in colour, regular in standard shape and size, free from cracks, emit a clear ringing sound on tapping with a steel trowel and have a crushing strength as per the Nepal Standard Brick Masonry NS: 1/2035.  A brick shall not absorb more water than 15 % of its weight after 24 hours of soaking in water at normal temperatures.  However, hand-made bricks with keys may have water absorption up to 25 % of their weight.  For first class brickwork, the corresponding mortar types should be H1 and H2.
3.4.2
Limitation
Masonry units that have been previously used should not be re-used in brick work or brickwork construction unless they have been thoroughly cleaned and shown to conform to the Nepal Standard Brick Masonry NS: 1/2035.
3.5
Mortar
Mortar used in masonry construction shall, unless otherwise specified, conform to the specification listed in NBC 101 – Material Specifications. Some of the commonly-used mortars in Nepal and their mix proportions, along with their strengths, are listed in Table 3.4.
* 1 N/mm² = 1 MPa = 10.2 kg/cm² Table 3.4 : Mix Proportions and Strength of Commonly- Used Mortars for Masonry Notes : i) The strength of mortar may vary appreciably depending on the angularity, grading and fineness of the sand.  The quantity of sand in the mix may, therefore, be decreased where found necessary to attain the desired strength. ii) A, B and C denote eminently hydraulic lime, semi-hydraulic lime and fat lime respectively. iii) When using plain cement sand mortars [S. No. 2(a), 3(a), 4(a), and 5(a)], it is desirable to include a plasticizer in the mix to improve workability. iv) For mortar to S. No. 6, if lime C is used, part of the sand should be replaced by some pozzolanic materials (eg., burnt clay or fly ash), in order to obtain the required compressive stress. v) In this table, the classification of mortars as types H1, H2, M1, M2, L1 or L2 has been given for convenience of reference in design calculations, the letter H standing for high strength, M for medium strength and L for low strength. vi) For mortar types H2, M1, and M2, although the compressive strength of composite mortars (that is, cement and lime mortars) is somewhat less than that of cement mortars, the masonry strength may not be significantly affected.
4
General Construction and Design Requirements
4.1
General
The porvisions in clause 4.1 to 4.7 of the Indian Standard IS:1905-1987 shall be applicable for designing masonry structures. In addition, the following clauses will also be equally applicable :
4.2
Selection of Mortar
The requirements of a good mortar for masonry structure are workability, strength, water retentively and low drying shrinkage.  Mortar strength in general should not be greater than that of the masonry unit.  For commonly-used mortars conforming to Table 3.4 , the optimum mortar mixes from a brick strength consideration are given in Table 4.1.
Optimum  Mortar  Mixes  For  Maximum  Masonry  Strength  with Table 4.1 : Masonry Units of Various Strengths
4.3
Thickness of Walls
The thickness of a load-bearing wall shall be sufficient at all points to ensure a) that stresses due to the worst condition of loading for which the wall is designed are within the safe limit.  The thickness of non load-bearing walls shall be sufficient to meet considerations of stability and strength against lateral forces. b) The thickness used for design calculation shall be the actual thickness of the masonry, not the nominal thickness.  The actual thickness shall be computed as the sum of the average dimensions of the masonry units as specified in the Nepal Standard Brick Masonry NS:1/2035 , together with the specified joint thickness. In masonry with raked joints, the thickness shall be reduced by the depth of raking.  However, if joints are raked to provide a key for subsequent plastering and the mix of mortar for plastering is not weaker than the masonry mortar, raking may be ignored.  Also, if the  raking of joints is to be followed by flush-pointing using a mortar of the same or better strength,  the raking may be ignored. c) The thickness of a wall determined from strength considerations may not be always sufficient to satisfy requirements with regard to other properties of the wall such as resistance to fire, thermal insulation, sound insulation or resistance to rain penetration.
4.4
Stability Requirements
4.4.1
Lateral Support
Lateral support for a masonry element such as a wall or column is required: a) to resist horizontal components of the forces so as to ensure stability of the structure against over-turning; and b) to limit the slenderness of masonry elements in order to prevent failure by buckling.
4.4.2
Adequate Lateral Support
A wall or column may be considered to be provided with adequate lateral support if the construction providing the support is capable of resisting the greater of the following lateral forces : a) The simple static reactions at the point of lateral support to the total applied horizontal forces ; or 2.5 percent of the total vertical load that the wall or column is designed to carry at the point of lateral support. Lateral support may be provided in either the vertical or horizontal direction. Horizontal lateral support could consist of the floor/roof acting as a horizontal girder capable of transmitting without excessive stresses the horizontal forces to cross-walls acting as stiffening walls. Vertical support could consist of cross-walls/piers/buttresses capable of transmitting without excessive stresses the horizontal forces to the foundation.
4.5
Parapets and Compound Walls
4.5.1
General
Since, in the case of a free-standing wall such as a compound wall or parapet wall, there is no lateral support at its top and no cross-walls to brace the same, stability shall be achieved by designing the wall as a gravity structure such that the factor of safety against overturning is at least 1.5.  As straight walls designed on this basis tend to be heavy, the stability of free-standing walls greater than 0.9 m in height should be achieved by staggering or by the provision of piers or buttresses.  Even though a straight free-standing wall may be stable with the stipulated factor of safety (1.5), it will have some tension, because a condition of zero tension corresponds to a factor of safety of 3 against overturning.  Mortar used in masonry of a straight, free-standing wall should not normally be weaker than type M1 indicated in Table 4.1 unless walls are thick enough in relation to their height so as to be free from any tension.
4.5.2
Free-Standing Walls
A free-standing wall must be designed to be safe as a vertical cantilever.  All partition walls inside a building must be held on their sides as well as at their tops.
4.5.3
Load Bearing Masonry Elements
In the case of an unreinforced load-bearing wall using ordinary Portland cement, the slenderness ratio shall not exceed 17.
4.5.4
Slenderness Ratio
The slenderness ratio for a load-bearing column shall not exceed 12.
4.5.5
Curtain Walls
Curtain walls shall be designed as panel walls to resist lateral forces caused by wind or earthquakes in addition to their own weight.  The junction details at the lateral supports shall be such that any vertical deformations or rotations of the structural members providing the lateral support are not transferred to the curtain wall.  Similarly, there shall be freedom for the curtain wall to have deformation in the vertical direction.
4.6
Structural Design
The specificaton laid down in clauses 5.1 to 5.5.5 of Indian Standard IS:1905-1987 shall apply to the structural design of masonry. The additional clauses as given here under shall also apply.
4.7
Design Method
The structural design of non-reinforced masonry shall be as per the design procedures given below :
4.7.1
Design Procedures
The building as a whole shall be analysed by accepted principle of mechanics to ensure the safe and proper functioning in service of its component parts relative to the whole building.  All component parts of the structure shall be capable of sustaining the most adverse combinations of loads to which the building may be reasonably expected to be subjected during or after erection.
4.7.2
Design Loads
Loads to be taken into consideration for designing masonry components of a structure are : a) dead load of walls, column, floors and roofs; b) live load on floors and roof; c) wind load on walls and roof; and d) seismic forces.
4.7.3
Design of Wall Footings
4.7.3.1   Depth of Footing
The net safe bearing capacity of the soil and the depth of foundation in the soil are best determined by modern soil investigation methods.  In the absence of such an investigation report, a conservative minimum depth of footing may be determined using  the following formula : P 2 D = W where : D = minimum depth of footing in metres. P = net safe bearing capacity of soil (kPa). W = unit weight of soil (kN/m 3 ). λ = angle of repose of soil in degrees. Note : The above formula is not valid if the soil condition is  Soft or Weak as categorised in Table 7.1. In all cases, the footing  should be founded below seasonal moisture variation and to consistent bearing
4.7.3.2   Width of Footing
The minimum width of the footing, B, shall be obtained by dividing the total load (including dead loads), live  and wind load) by the allowable bearing capacity of the soil : T
P where : B = width of footing in metres. T = total load per metre. P = safe bearing capacity. Note : The above formula is not valid if the soil condition is Soft or Weak as categorised in Table 7.1.
4.7.4
Permissible Compressive Stresses
The permissible compressive stresses shall be in accordance with the Indian Standard IS : 1905-1987  in which the design value of permissible compressive stress, f c , depends on a combination of the following factors : 1) basic compressive stress based on type and strength of the masonry units and mix of mortar, fb 2) factor for slenderness ratio and eccentricity of masonry elements, kse 3) factor for shape and size of the masonry unit, k p 4) factor for cross-sectional area of masonry, k a and 5) factor for load type, kı so that : fc= fb kse kp ka kp The values of the basic compressive stresses and the various factors are given in IS : 1905-1987, clause 5 and its subclauses.
S
General Requirements
5.1
Deforming and Cracking
Special provisions shall be made to control or isolate thermal and other movements so that damage to the fabric of the building is avoided and its structural sufficiency is preserved.  The design and installation of joints shall be done in accordance with accepted practice.
5.2
Cutting and Chasing
As far as possible, service (Electrical, Plumbing, etc.) should be planned with the help of vertical chases.  Horizontal chases should be avoided. For load-bearing walls, the depth of vertical chases and horizontal chases shall not exceed one-third and one-sixth of the thickness of the masonry, respectively. No chase shall be permitted in a half-brick load-bearing wall.
5.2.1
Stretches of Masonry
When narrow stretches of masonry (or short lengths of wall), such as between doors and windows, cannot be avoided, they should not be pierced with openings for soil pipes or waste pipes or timber joists, etc.  Where there is a possibility of load concentration, such narrow lengths of walls shall be checked for stresses and high-strength bricks/mortar or concrete walls provided, if required.
5.2.2
Horizontal Chases
Horizontal chases, when unavoidable, shall be located in the upper or lower thirds of a storey and not more than three chases should be permitted in any stretch of a wall.  No continuous horizontal chase shall exceed one metre in length.
5.2.3
Vertical Chases
Vertical chases shall not be closer than two metres in any stretch of a wall. These shall be kept away from the bearing of beams and lintels.  If unavoidable, stresses in the affected area should be checked and kept within permissible limits.
5.2.4
Masonry Directly Above A Recess
Masonry directly above a recess, if wider than 30 cm (horizontal dimension), should be supported on lintel.  Holes in masonry up to 30 cm width x 30 cm high may be provided without a lintel.  In the case of circular holes in masonry, a lintel should be provided only if arch action can not be achieved.
5.3
Workmanship
The quality of workmanship has considerable effect on the strength of masonry and bad workmanship may reduce the strength of brick masonry to as low as half the intended strength.  The basic compressive stress values for masonry given in IS : 1905-1987, Table 8 are appropriate for commercially-obtainable standards of workmanship with a reasonable degree of supervision.  If the work is going to be inadequately supervised, design strengths should be reduced to three-quarters of these values.
5.3.1
Bedding of Masonry Units
Masonry units shall be laid on a full bed of mortar with the frog, if any, upward and so that cross-joints and bed-joints are completely filled with mortar. Masonry units which are moved after their initial placement shall be re-laid in fresh mortar.  Old or disturbed mortar shall be discarded.
5.3.2
Bond
The cross-joints in any course of one brick thick masonry walls shall be not less than one quarter of a masonry unit in horizontal measurement from the cross-joints in the course below.  In masonry walls more than one brick in thickness, bonding through the thickness of the wall shall be provided by either header units or by other equivalent means.
6
Special Considerations for Earthquake Resistance
6.1
Siting
The site should be free from landslide and rock fall areas and liquefaction potential (loose, saturated sand up to about six metres depth below the ground surface).  See NBC 108-94 Site Considerations for more details.
6.2
General Concepts
6.2.1
Categories of Buildings
For categorizing buildings for the purpose of achieving seismic resistance at economical cost, three parameters turn out to be significant : Seismic Intensity Zoning where the building is located, a) b) Important of the building and Stiffness of the foundation soil. c) A combination of these parameters will determine the extent of appropriate seismic strengthening of the building.
6.2.2
Seismic Zoning
The variation in seismic hazard with location in Nepal is defined for design purposes in Figure 8.2 of NBC105-94 Seismic Design of Buildings in Nepal . For the purpose of the design of unreinforced masonry, a simplified zonation based on this figure shall be used. Three zones A, B and C are defined in Table 6.1 and are shown in Figure 6.1 below.

Table 6.1 :
Seismic Zones for Unreinforced Masonry
6.2.3
Importance of Building
The importance of the building should be a factor in grading it for strengthening purposes.  Importance depends upon its occupancy, use and need before and after a disaster as given in Table 6.2.
The buildings under the Important category have been subdivided into two groups from a constructions point of view.  These are : A. Buildings in accessible areas where modern materials such as cement and reinforcing bars can be easily transported B. Buildings in remote inaccessible areas to where modern materials can not easily be transported.
7
Site Considerations
General
7.1
This section sets out some of the requirements to be considered during site selection for the construction of buildings in order to minimise the risks to buildings from both primary geological hazards and secondary seismic hazards such as fault rupture, landslide and liquefaction.  Since this is the first such effort to introduce the importance of geotechnical conditions and the nature of foundation soil in the stability of Nepalese building, the requirements set out here have deliberately been kept low to encourage effective implementation.
7.2
General Considerations
As a good practice during the construction of a building, it is necessary to examine all existing local knowledge and the performance histories of existing building. The designer should thus be able to identify any dangers from an inherent natural susceptibility of the land to the processes of sliding, erosion, land subsidence and liquefaction during past earthquakes, or from any other natural/geological process likely to threaten the integrity of the building. The local practice of managing such hazards, if any, should be judged against the required level of acceptable risk.
7.3
Site Investigation Requirements
For load-bearing masonry buildings and reinforced concrete (RC) frame buildings with masonry infills, site exploration should be carried out by digging test pits, two as a minimum, and more if the subsurface soil conditions show a variation in soil types. Generally the depth of exploration for the buildings should be a minimum of two metres.  In hilly areas, exploration up to the depth of sound bed rock, if it lies shallower than two metres, should suffice. No exploration shall be required if the site is located on rock or on fluvial terraces (Tar) with boulder beds. The soils encountered in the test pits should be classified as per Table 7.1.
7.4
Allowable Bearing Pressure
The allowable bearing pressure could be calculated using the Table 7.1. in conjunction with the visual classification of the subsurface soil type.

Classification of Foundaton Soil And Safe Bearing Capacity
Table 7.1 :
Buildings can be constructed on hard, medium and soft soils but it will be dangerous to build them on weak soils.  Hence, appropriate soil investigation should be carried out to establish the allowable bearing capacity and nature of soils.  Weak soils must be avoided or compacted to improve them so that they qualify as at least Medium or Soft soils.
7.5
Combination of Parameters
For determining the categories of building for seismic strengthening purposes four categories (I to IV) are defined in Table 7.2 in which category I will require maximum strengthening and category IV the least.  The general planning and designing principles are, however, equally applicable to all categories.
Notes : i) Seismic Zones A, B and C are as per Figure 6.1 ii) Weak soils liable to compaction and liquefaction under earthquake conditions are not covered here. Note:
ii)
<0.5 L 1 for one storey, <0.42 L 1 for two-storeyed, <0.33 L 1 for three-storeyed <0.5 L 1 for one storey, <0.42 L 1 for two-storeyed, <0.33 L 1 for three-storeyed
>0.5 h, but not less than 600 mm
Figure 7.1 : Recommendations Regarding Opeinings in Bearing Walls ALTERNATIVE - 1 SECTIONAL PLAN AT Y - Y 1st COURSE 2nd COURSE Ø  -- Diameter, W -- Window, V --- Vertical Reinforcing  bar, t -- Thickness of wall ( minimu    l brick length) , t1 -- Minimum  thickness 75 mm., L -- Length of brick unit. Figure 7.2 : Strengthening of Masonry Around Openings
8
Openings in Walls
a) b) c) d) e) f) g) h) i) j) Openings shall be located away from the inside corner by a clear distance equal to at least one-quarter of the height of openings, but not less than 600 mm. The total length of openings shall not exceed 50 % of the length of the wall between consecutive cross-walls in single-storey construction, 42 % in two-storey construction and 33 % in three-storey buildings. The horizontal distance (pier width) between two openings shall not be less than one- half of the height of the shorter opening (Figure 7.1), but not less than 600 mm. The vertical distance from an opening to an opening directly above it shall not be less than 600 mm, nor less than one-half of the width of the smaller opening (Figure 7.1) When openings do not comply with requirements (a) to (b), they should be boxed in reinforced jambs through the masonry (Figure 7.2) Tops of openings in a storey should preferably be at the same level, so that a continuous band which includes the lintels throughout the building can be provided. If a window or ventilator is to be projected out, the projection shall be in reinforced masonry or concrete and well-anchored. If an opening is tall enough with respect to the full height of wall so as to divide effectively the wall into two portions, these portions shall be reinforced with at least 6 mm diameter horizontal bars at not more than 600 mm intervals on both the inner and outer faces. This steel at jambs and  at corners or junctions of walls. The use of arches to span over the openings is a source of weakness and shall be avoided unless steel ties are provided. All the walls must be effectively tied together to avoid separation at vertical joints due to ground-shaking during an earthquake.
9
Masonry Bond
9.1
Vertical Joints between Perpendicular Walls
A sloped or stepped joint should be made in order to obtain full bond by making the corners first to a height of 600 mm and then building the wall in between them. Alternatively, a toothed joint should be made in each wall alternately in lifts of about 450 mm, as shown in Figure 9.1. All dimensions are in mm a, b, c Toothed joint in walls A, B and C ( Alternating toothed joint in walls at corner and T-junctions ) Figure 9.1: A Typical Detail of Jointing in Masonry
10
Horizontal Reinforcement in Walls
Horizontal reinforcing of walls is required to give to them horizontal bending strength against plate-action for out-of-plane inertia loads, and for tying orthogonal walls together.
10.1
Horizontal Bands or Ring Beams
a)
Plinth Band
A plinth band should be provided in all cases where the soil is soft or uneven in its properties.
b)
Lintel Band
The lintel band  shall incorporate all door and window lintels, the reinforcement of which should be extra to the lintel band steel.  It must be provided in all storeys in all walls of the buildings as per Table 11.1.
c)
Roof Band
A roof band  shall be provided at the eave-level of trussed roofs (Figure 4), and also below or in the level of such floors that  consist of joists and covering elements so as to properly integrate them at their ends and fix them into the walls.
d)
Gable Band
Masonry gable-ends must have the triangular portion of masonry enclosed in a band, the horizontal part of which will be continuous with the eave-level band on longitudinal walls (Figure 10.1). Note: i) As an alternative to the gable masonry, a truss or open gable may be used and the openings covered with a light material such as sheeting, matting etc. ii) If the wall-height up to eave-level is less than or equal to 2.5 m , the linteHevel band may be ommitted and the lintel integrated with the eave-level band as shown in Detail 2 Figure 10.1 :  Gable Band and Roof Band in Barrack-Type Buildings
11
Section of Bands or Ring Beams
A band consists of two (or four) longitudinal steel bars with stirrups embedded in 75 mm (or 150m mm) thick concrete (Figure 11.1 and 11.2). The thickness of the band may be made equal to, or a multiple of, a masonry unit, and its width shall equal the thickness of the wall. The steel bars shall be located close to the wall faces with 25 mm cover, and full continuity shall be provided at corners and junctions. o a)  CROSS SECTION OF R.C. BAND FOR TWO BARS AND FOUR BARS OF DIA. ' b) R. C. BAND REINFORCEMENT DETAILS AT CORNER AND T-JUCTION b, b1, b2 = Wall thiskness 1 : 2 : 4 or 15 N mm dibe strength Note: de overlaps for sicing bars outside the corner length of overlap to dev velop full band say 50 d. Figure 11.1 :  Reinforced Concrete Band and Details
a) CROSSECTIONOFRCC BANDFORTWOBARSANDFOURBARS
b) R.C.BANDREINFORCEMENTDETALSATCORNERANDT-JUCTION
b, b1, b2 = Vill tridness Conste   1:2:4or15Nnm Atestergh Ncte Proideostas for slorg bas outsidethe comerlang thorovetap
to design ful band says ou Figure 112:  Reinforcement in Reinforced Concrete Bard
* T = High strength bar having an f, of 415 N/mm² (Fe 415 Grade) K = High strength bar having an f, of 550 N/mm² (Fe 550 Grade) Table 11.1 : Recommendation for Steel in RC Bands Notes : i) Width of the RC band is assumed to be the same as the thickness of wall. Wall thickness shall be 230 mm minimum.  A cover of 25 mm from face of wall shall be maintained. ii) The vertical thickness of a RC band may be kept to a minimum of 75 mm where two longitudinal bars are specified and 150 mm where four longitudinal bars are specified. iii) Concrete mix to be 1:2:4 by volume or to have an M15 Grade cube crushing strength at 28 days. iv) The longitudinal bars shall be held in position by steel stirrups 6 mm in diameter spaced no more than 150 mm apart.
Dowels at Corners and Junctions
Steel dowel bars shall be used at corners and T-junctions to integrate the box action of walls. Dowels (Figures 12.1, 12.2, 12.3 and 12.4) are to be taken into the walls to a sufficient length so as to provide their full bond strength. 1 2 = Cross links = Thick joints to receive dowels Figure 12.1 :  Corner-Strengthening by Dowel Reinforcement Placed in One Joint
12
t 1, t 2 = Wall thisness = Oross links 1 2 = Thick joints to receive dovels Figure 121 :  Corner-Strengthening by Dowel Reinforcement Placed in Two Consecutive Joint Figure 12.3 :  T-Junction Strengthening by Dowel Reinforcement
13
Vertical Reinforcement in Walls
Steel bars shall be installed at the critical sections (i.e. the corners of walls and jambs of doors right from the foundation concrete) and covered with cement concrete in cavities made around them during masonry construction (Figure 13.1) .  This concrete mix should be 1:2:4 by volume or stronger. The vertical steel at an opening may be stopped by bending it into the lintel band but the vertical steel at corners and junctions of walls must be taken into the floor slab, roof slab, or roof band.
Table 13.1 :
Recommendation for Vertical Steel at Critical Sections
Notes : i) The above vertical reinforcement in walls is valid for up to three- storeyed buildings ii) Four-storeyed and above load-bearing wall construction may not be used for categories I and II buildings. CORNER JUNCTION DETAILS FOR ONE AND HALF BRICK WALL FOR PROVIDING VERTICAL STEEL. T- JUNCTION DETAILS FOR ONE AND HALF BRICK WALL FOR PROVIDING VERTICAL STEEL. %. ½. and 1 indicates:  ¼ Brick wide,  ½ Brick wide, 1 Brick long etc.,
V  - Vertical Bar Figure  13.1 :  Vertical Reinforcement in Walls
14
Reinforcement Details for Hollow Block Masonry
14.1
Horizontal Band
U-shaped blocks should be used for the construction of horizontal bands at various levels of the storey as per seismic requirements as shown in Figure 4.1. The amount of horizontal reinforcement shall be taken as 25 % more than that given in Table 11.1 and provided by using four bars and 6 mm diameter stirrups. 1  -  Lintel Band 2  -  Roof Band ( only for pitched roofs and under roofs and floor ) 3  -  Vertical steel. Figure 14.1 :  Overall Arrangement of Reinforcing Masonry Buildings
15
Vertical Reinforcement
The vertical bars specified in Table 13.1 can be conveniently located inside the cavities of the hollow blocks - one bar in one cavity.  Where more than one bar is planned, these can be located in two or three consecutive cavities as shown in Figures 15.1 and 15.2.
15.1
Infill Panels and Non-Structural Walls
a) In-fill panel walls in a building shall be designed to ensure that they act together with the frame in  full composite action. b) The seismic load at each level shall be distributed to the individual wall in proportion to the product of each  wall's thickness and length. This product is representative of the diagonal strut area and thus of the wall's shear stiffness. c) Any frame is to be designed to resist all the gravity loads without any assistance from the infill walls as these walls may either fail or be very severely damaged in a large earthquake. d) The centre of rigidity of the infill walls (except face wall) shall be as near as possible to the centre of rigidity of the complete system of walls. e) An infill wall shall be so designed that it sustains minimum damage during any deflection of the supporting structure during an earthquake and shall be designed to resist all action resulting from in-plane and face loads. f) The minimum thickness of an infilled wall shall be the same as that of partition walls, and its openings should be as small as possible and cover not more than 10 % of the panel area. The preferable location of an opening in a wall is outside the central two-thirds of the sides and away from the corners. If the opening must be  near the centre of the wall, it shall be bounded by a reinforced concrete beam 75 mm thick, the other dimension to be equal to thickness of wall and reinforced with two 10 mm diameter Fe 415 grade bars longitudinally and 5 mm diameter Fe 550 grade bar link ties . g) Partition walls shall have a minimum thickness shall have horizontal reinforcement (one  6 mm  diameter bar in each face) in every sixth course of blockwork. h) If the infill wall is constructed in a Category I or II building, the thickness of infill wall shall not be less than 230 mm. (b)
16
Wall Thickness and Spacing

The minimun thicknesses and maximum spacings of masonry walls shall be as dexcribed in Tables 16.1 and 16.2. * Provision should be made for expansion/contraction joints. Table 16.1 : Buildings Thickness of Walls for Public Buildings, Warehouse and Incustrial Notes : (i) An additional thickness of one-half a brick at the base will usually be sufficient where vibrating machinery is used. (ii) The base thickness is reduced towards the top; for 5 m from the top of wall, the thickness should be 1.5 bricks, but where the wall does not exceed 9 m in height, the wall for 3.5 m from the top may be one brick thick if the wall is in a cement mortar.
Table 16.2 :     Thickness and Spacing of Stiffening Walls