Code of Massachusetts Regulations › 780 CMR - STATE BOARD OF BUILDING REGULATIONS AND STANDARDS › Chapter 16 - Structural Design › Section 1607 - LIVE LOADS › Subsection 1607.9 - Reduction in live loads

Current through Register 1525, July 5, 2024
Except for uniform live loads at roofs, all other minimum
				  uniformly distributed live loads,
L
o,
				  in Table 1607.1 are permitted to be reduced in accordance with Section 1607.9.1
				  or 1607.9.2. Roof uniform live loads, other than special purpose roofs of
				  Section 1607.11.2.2, are permitted to be reduced in accordance with Section
				  1607.11.2. Roof uniform live loads of special purpose roofs are permitted to be
				  reduced in accordance with Section 1607.9.1 or 1607.9.2.
1607.9.1
General.
Subject to the
				limitations of Sections 1607.9.1.1 through 1607.9.1.4, members for which a
				value of
K
LL
A
Tis
				400 square feet (37.16 m2) or more are permitted to
				be designed for a reduced live load in accordance with the following equation:
Click to view
							 image
(Equation 16-22)
For SI:
Click to view
							 image
where:
L
=
Reduced design live load per square foot (square
							 meter) of area supported by the member.
L
o
=
Unreduced design live load per square foot (square
							 meter) of area supported by the member (see Table 1607.1).
K
LL
=
Live load element factor (see Table 1607.9.1).
A
T
=
Tributary area, in square feet (square meters).
L
shall not be less than
							 0.50
L
o for members supporting one
							 floor and
L
shall not be less than 0.40
L
o for members supporting two or more
							 floors.
TABLE 1607.9.1 LIVE LOAD ELEMENT FACTOR,
K
LL
ELEMENT
K
LL
Interior columns
Exterior
							 columns without cantilever slabs
4 4
Edge columns with cantilever slabs
3
Corner columns with cantilever
							 slabs
Edge beams without cantilever slabs
Interior
							 beams
2 2 2
All other members not identified above
							 including:
1
Edge beams with cantilever slabs
Cantilever beams
One-way slabs
Two-way
							 slabs
Members without provisions for continuous shear
transfer normal to their span
1607.9.1.1
One-way slabs.
The tributary area,
A
T, for use in Equation 16-22 for
				one-way slabs shall not exceed an area defined by the slab span times a width
				normal to the span of 1.5 times the slab span.
1607.9.1.2
Heavy live loads.
Live loads that exceed 100 psf (4.79 kN/m2) shall
				not be reduced.
Exceptions:
1. The live loads for members supporting two
				or more floors are permitted to be reduced by a maximum of 20 percent, but the
				live load shall not be less than
L
as calculated in Section
				1607.9.1.
2. For uses other than
				storage, where
approved
, additional live load reductions shall
				be permitted where shown by the
registered design professional
that a rational approach has been used and that such reductions are
				warranted.
1607.9.1.3
Passenger vehicle garages.
The live loads shall not be reduced in
				passenger vehicle garages.
Exception:
The live loads for members supporting
				  two or more floors are permitted to be reduced by a maximum of 20 percent, but
				  the live load shall not be less than
L
as calculated in
				  Section 1607.9.1.
1607.9.1.4
Group A occupancies.
Live loads of 100 psf (4.79 kN/m2) and at
				areas where fixed seats are located shall not be reduced in Group A
				occupancies.
1607.9.1.5
Roof
				members.
Live loads of 100 psf (4.79 kN/m2)
				or less shall not be reduced for roof members except as specified in Section
				1607.11.2.