Lighting Pounds Per Square Foot

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aramg83

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Client has asked me to show load calculations for light fixtures being mounted to deck above. Each fixture weighs 40 lbs and is 48" Long and most of it's weight is concentrated in 8" of its width. The obvious answer is 40lbs /(4'x.66') = 15 lbs/sq ft.

Would the fact that it is pendant mounted affect the load where each pendant cord is fastened to the deck above? How would I go about calculating the load at each cord?

Thanks
 
iwire

iwire

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Location
Massachusetts
I would find the square footage of the area and the total weight of all the fixtures and parts then just do some dividing to find out what your square foot loading will be.

Only if they asked for point loading would I worry about what the forces is on each pendant.
 
Smart $

Smart $

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Location
Ohio
I don't think that's what your client is asking for (but with the way things seem to go nowadays, I very well could be wrong :roll:)

What I think your client is asking for is the dead load that the lighting will attribute to the decking's rated load. Calculating that is easy. Multiply the number of suspended fixtures times the weight per fixture, and divide that by the deck area from which the lighting will be supported (ft?), . Example:

(100 fixtures ? 40lbs/fixture) ? 10,000 ft? building = .4 lbs/ft?

This is assuming no fixtures are concentrated to an area. If the spacing varies by much, you may have to break the calculation down to smaller areas.
 
iwire

iwire

Moderator
Staff member
Location
Massachusetts
Smart $ said:
What I think your client is asking for is the dead load that the lighting will attribute to the decking's rated load. Calculating that is easy. Multiply the number of suspended fixtures times the weight per fixture, and divide that by the deck area from which the lighting will be supported (ft?), . Example:

(100 fixtures ? 40lbs/fixture) ? 10,000 ft? building = .4 lbs/ft?

This is assuming no fixtures are concentrated to an area. If the spacing varies by much, you may have to break the calculation down to smaller areas.
Click to expand...

Did we just agree?
 
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