Occupancy Load and Live Loads

Question

Occupancy Load and Live Loads

JKJohn (Structural)

(OP)

28 Sep 12 09:55

What are the bases that the IBC/ASCE uses to determine the live load on structures?

For example, the live load for an Assembly area with movable seats is 100 psf. The IBC requires the Occupant Load to not exceed one occupant per 5 square feet. Assuming the average person weight to be 250 lbs and each chair to be around 10 lbs, this makes 260 lbs per occupant. Divide that over 5 square feet and you will get 52 psf. Shouldn't this be the live load? Obviously the IBC has a different criteria/formula. Does anyone know the basis for the IBC to get the 100 psf?

woodman88 (Structural) · Answer 1 · 2012-09-28 11:06:53

IMHO The Occupant Load is the maximum number of people that are allowed in an area by code. The 5 sq. ft. is not a square area. If they are lined up, you may have them in a 1 ft apart by 2' wide area. So that if located over a joist you will have a 200 plf loading with 2' o.c. joists or 100 psf.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

frv (Structural) · Answer 2 · 2012-09-28 11:49:27

Live Loads, generally speaking, also account for extreme events. The extreme event is not people attending the stadium for an event. It is, for example, people packed tightly into a stadium to escape a natural disaster.

I believe there was a survey was conducted early last century in some American cities to come up with an average for offices. However, the Live Loads are not rigorously derived. They are agreed upon by experienced engineers as a safe, minimum level of loading that will account for the vast majority of conditions.

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Occupancy Load and Live Loads