You are viewing an archived code
Permitted reduction in live loads shall comply with the provisions of subsections (a), (b) and (c) of this section.
(a) Permitted Reductions in Floor Construction. Beams, girders and trusses shall be designed to carry not less than the following percentage of the live floor loads established in Section 13-52-090 or based on the tributary floor area and influence area carried by the members.
1. For live loads of 100 pounds per square foot or less:
Tributary Area In Square Feet | Influence Area | Percentage of Live Load |
less than 200 | 400 | 100 |
300 | 600 | 86 |
400 | 800 | 78 |
600 | 1,200 | 68 |
800 | 1,600 | 63 |
greater than 800 | greater than 1,600 | 60 |
2. Linear interpolation between tabulated percentage of live loads is permitted.
3. For live loads that exceed 100 pounds per square foot no reduction is permitted.
4. No reduction is allowed for areas to be occupied as places of public assembly, garages or parking facilities, one way slabs or joists.
(b) Permitted reductions in bearing walls, columns, piers and other members supporting more than one floor shall be based on the tributary area and influence area carried by the member.
1. For live loads of 100 pounds per square foot or less:
Tributary Area In Square Feet | Influence Area | Percentage of Live Load |
less than 200 | 800 | 100 |
300 | 1,200 | 68 |
400 | 1,600 | 63 |
600 | 2,400 | 56 |
800 | 3,200 | 52 |
900 and greater | 3,600 and greater | 50 |
2. Linear interpolation between tabulated percentage of live loads is permitted.
3. No reduction is allowed for areas to be occupied as places of public assembly or for roofs. For garages and parking facilities see (4).
4. For live loads that exceed 100 pounds per square foot, and in garages and parking facilities for passenger vehicles only, members supporting more than one floor may be designed to carry not less than 80 percent of the live loads established in Section 13-52-090.
(c) Tributary Area/Influence Area. The influence area is defined as that floor area over which the influence surface for structural effects is significantly different from zero. For columns this is four times the traditional tributary area, while for flexural members it is two times. For an interior column, for instance, the influence area is the total area of the four surrounding bays, while for an interior girder it is the total area of the two contributing bays. Edge columns and girders have half the influence area of the respective interior members (two days for columns, one for girders), while a corner column has an influence area of one bay. For unusual plan configurations, the concept of significant influence effect should be applied. For multiple floors, areas for members supporting more than one floor are summed.
(Prior code § 68-2.14; Added Coun. J. 11-29-89, p. 8387)