Code of Massachusetts Regulations › 780 CMR - STATE BOARD OF BUILDING REGULATIONS AND STANDARDS › Chapter 16 - Structural Design › Section 1604 - GENERAL DESIGN REQUIREMENTS › Subsection 1604.3 - Serviceability

Current through Register 1525, July 5, 2024
Structural systems and members thereof shall be designed to
				  have adequate stiffness to limit deflections and lateral drift. See Section
				  12.12.1 of ASCE 7 for drift limits applicable to earthquake loading.
TABLE 1604.3 DEFLECTION LIMITSa, b, c, h,
				  i
CONSTRUCTION
L
S
or
W
f
D
+
L
d,
							 g
Roof members:e
Supporting plaster ceiling
l
/360
l
/360
l
/240
Supporting nonplaster ceiling
l
/240
l
/240
l
/180
Not supporting ceiling
l
/180
l
/180
l
/120
Floor members
l
/360
-
l
/240
Exterior walls and interior partitions:
With brittle finishes
-
l
/240
-
With flexible finishes
-
l
/120
-
Farm buildings
-
-
l
/180
Greenhouses
-
-
l
/120
For SI: 1 foot = 304.8 mm.
a. For structural roofing and siding made of formed
								metal sheets, the total load deflection shall not exceed
l
/60.
								For secondary roof structural members supporting formed metal roofing, the live
								load deflection shall not exceed
l
/150. For secondary wall
								members supporting formed metal siding, the design wind load deflection shall
								not exceed
l
/90. For roofs, this exception only applies when
								the metal sheets have no roof covering.
b. Interior partitions not exceeding 6 feet in
								height and flexible, folding and portable partitions are not governed by the
								provisions of this section. The deflection criterion for interior partitions is
								based on the horizontal load defined in Section 1607.13.
c. See Section 2403 for glass supports.
d. For wood structural members having a moisture
								content of less than 16 percent at time of installation and used under dry
								conditions, the deflection resulting from
L
+
								0.5
D
is permitted to be substituted for the deflection
								resulting from
L
+
D
.
e. The above deflections do not ensure against
								ponding. Roofs that do not have sufficient slope or camber to assure adequate
								drainage shall be investigated for ponding. See Section 1611 for rain and
								ponding requirements and Section 1503.4 for roof drainage requirements.
f. The wind load is permitted to be taken as 0.7
								times the "component and cladding" loads for the purpose of determining
								deflection limits herein.
g. For steel structural members, the dead load
								shall be taken as zero.
h. For aluminum structural members or aluminum
								panels used in skylights and sloped glazing framing, roofs or walls of sunroom
								additions or patio covers, not supporting edge of glass or aluminum sandwich
								panels, the total load deflection shall not exceed
l
/60. For
								continuous aluminum structural members supporting edge of glass, the total load
								deflection shall not exceed
l
/175 for each glass lite or
l
/60 for the entire length of the member, whichever is more
								stringent. For aluminum sandwich panels used in roofs or walls of sunroom
								additions or patio covers, the total load deflection shall not exceed
l
/120.
i. For cantilever members,
l
shall be taken as twice the length of the cantilever.
1604.3.1
Deflections.
The deflections of structural members shall not exceed the
				more restrictive of the limitations of Sections 1604.3.2 through 1604.3.5 or
				that permitted by Table 1604.3.
1604.3.2
Reinforced concrete.
The deflection of reinforced concrete structural members shall not exceed that
				permitted by ACI 318.
1604.3.3
Steel.
The deflection of steel structural members shall not
				exceed that permitted by AISC 360, AISI S100, ASCE 3, ASCE 8, SJI CJ-1.0, SJI
				JG-1.1, SJI K-1.1 or SJI LH/DLH-1.1, as applicable.
1604.3.4
Masonry.
The deflection
				of masonry structural members shall not exceed that permitted by TMS 402/ACI
				530/ASCE 5.
1604.3.5
Aluminum.
The deflection of aluminum structural members shall not exceed
				that permitted by AA ADM1.
1604.3.6
Limits.
Deflection of structural members over span,
l
, shall not exceed that permitted by Table 1604.3.