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 1531, September 27, 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 Wf | D + Ld, 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 + 0.5D 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.
