CHAP. 16, DIV. I1607.4.2

1611.51997 UNIFORM BUILDING CODE

23

whenever this loading creates greater stresses than those causedby the uniform live load. The concentrated load shall be placed onthe member over a length of 21/2 feet (762 mm) along the span.The concentrated load need not be applied to more than one spansimultaneously.

4. Water accumulation as prescribed in Section 1611.7.

1607.4.3 Unbalanced loading. Unbalanced loads shall be usedwhere such loading will result in larger members or connections.Trusses and arches shall be designed to resist the stresses causedby unit live loads on one half of the span if such loading results inreverse stresses, or stresses greater in any portion than the stressesproduced by the required unit live load on the entire span. Forroofs whose structures are composed of a stressed shell, framed orsolid, wherein stresses caused by any point loading are distributedthroughout the area of the shell, the requirements for unbalancedunit live load design may be reduced 50 percent.

1607.4.4 Special roof loads. Roofs to be used for special pur-poses shall be designed for appropriate loads as approved by thebuilding official.

Greenhouse roof bars, purlins and rafters shall be designed tocarry a 100-pound-minimum (444.8 N) concentrated load, Lr, inaddition to the uniform live load.

1607.5 Reduction of Live Loads. The design live load deter-mined using the unit live loads as set forth in Table 16-A for floorsand Table 16-C, Method 2, for roofs may be reduced on any mem-ber supporting more than 150 square feet (13.94 m2), includingflat slabs, except for floors in places of public assembly and forlive loads greater than 100 psf (4.79 kN/m2), in accordance withthe following formula:

R = r (A 150) (7-1)For SI:

R = r (A 13.94)The reduction shall not exceed 40 percent for members receiv-

ing load from one level only, 60 percent for other members or R, asdetermined by the following formula:

R = 23.1 (1 + D/L) (7-2)WHERE:

A = area of floor or roof supported by the member, squarefeet (m2).

D = dead load per square foot (m2) of area supported by themember.

L = unit live load per square foot (m2) of area supported bythe member.

R = reduction in percentage.r = rate of reduction equal to 0.08 percent for floors. See

Table 16-C for roofs.For storage loads exceeding 100 psf (4.79 kN/m2), no reduction

shall be made, except that design live loads on columns may bereduced 20 percent.

The live load reduction shall not exceed 40 percent in garagesfor the storage of private pleasure cars having a capacity of notmore than nine passengers per vehicle.

1607.6 Alternate Floor Live Load Reduction. As an alternateto Formula (7-1), the unit live loads set forth in Table 16-A may bereduced in accordance with Formula (7-3) on any member, includ-ing flat slabs, having an influence area of 400 square feet (37.2 m2)or more.

L Lo0.25 15AI (7-3)

For SI:

L Lo 0.25 4.57 1AI

WHERE:AI = influence area, in square feet (m2). The influence area AI

is four times the tributary area for a column, two timesthe tributary area for a beam, equal to the panel area for atwo-way slab, and equal to the product of the span andthe full flange width for a precast T-beam.

L = reduced design live load per square foot (m2) of areasupported by the member.

Lo = unreduced design live load per square foot (m2) of areasupported by the member (Table 16-A).

The reduced live load shall not be less than 50 percent of the unitlive load Lo for members receiving load from one level only, norless than 40 percent of the unit live load Lo for other members.

SECTION 1608 SNOW LOADSSnow loads shall be determined in accordance with Chapter 16,Division II.

SECTION 1609 WIND LOADSWind loads shall be determined in accordance with Chapter 16,Division III.

SECTION 1610 EARTHQUAKE LOADSEarthquake loads shall be determined in accordance with Chapter16, Division IV.

SECTION 1611 OTHER MINIMUM LOADS1611.1 General. In addition to the other design loads specifiedin this chapter, structures shall be designed to resist the loads spe-cified in this section and the special loads set forth in Table 16-B.1611.2 Other Loads. Buildings and other structures and por-tions thereof shall be designed to resist all loads due to applicablefluid pressures, F, lateral soil pressures, H, ponding loads, P, andself-straining forces, T. See Section 1611.7 for ponding loads forroofs.1611.3 Impact Loads. Impact loads shall be included in thedesign of any structure where impact loads occur.1611.4 Anchorage of Concrete and Masonry Walls. Concreteand masonry walls shall be anchored as required by Section1605.2.3. Such anchorage shall be capable of resisting the loadcombinations of Section 1612.2 or 1612.3 using the greater of thewind or earthquake loads required by this chapter or a minimumhorizontal force of 280 pounds per linear foot (4.09 kN/m) of wall,substituted for E.1611.5 Interior Wall Loads. Interior walls, permanent partitionsand temporary partitions that exceed 6 feet (1829 mm) in heightshall be designed to resist all loads to which they are subjected butnot less than a load, L, of 5 psf (0.24 kN/m2) applied perpendicu-lar to the walls. The 5 psf (0.24 kN/m2) load need not be appliedsimultaneously with wind or seismic loads. The deflection of such