Live Load Reduction on Podium Slabs

[jbuchanan15]

When designing a concrete podium slab supporting 4 stories of wood framed construction, can the live load portion of the line loads produced by the load bearing wood stud walls be reduced? If so, what influence area is used for this reduction calculation.

 

[mijowe]

I do reduce the live loads to podium slabs. I use a Kll of 1 for the two way slab, and use a At of the span x strip width x 4 floors. I reduce the podium level distributed live loads by this factor and the 3 floors of wood above. I do not reduce the roof load (which in my case is snow governing).

If I have various spans I try to pick a reasonable reduction that allows me to use one reduction factor as opposed to different ones for each span.

 

[DST148]

@jbuchanan15: There are quite a few threads on this topic. Try one of the recent ones: thread507-314132

 

[jbuchanan15]

I am specifically looking for a code reference that allows you to reduce line loads from stud walls when designing one way or two way slabs. The live load for the studwall design is not reduced because of the reduced influence area (16" o.c.), therefore why is the subsequent live load able to be reduced.

 

[msquared48]

Because the reinforcing strip in the podium slab supports a specific area that is able to be reduced. Remember that LLR is only applied to "members" as ASCE7 states it. This limits it to beams and columns.

PS Reinforcing strips are "beams" in my interpretation. However, bearing walls are not beams, and as you stated, the columns in the bearing wall are at 16" centers, not giving much area for reduction.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[mijowe]

because the tributary area of the slab includes all of the floor area from above, an area of size where reduction is possible. the point of live load reduction is because of the low probability of all areas being fully loaded.