Sustained live load

[Skicat]

What is the definition of sustained live load? Where in the code(s) can I find reference to it? Thank you.

 

[JAE]

Which code(s)? What is prompting the question?

 

[Lion06]

I'm guessing this is a question regarding how much LL to consider as sustained for a concrete beam deflection. We typically use about 1/3.

 

[Skicat]

What I am referring to is the amount of live load to consider when designing foundation elements such as piers and footings. Typicall a geotech will publish two different bearing capacities (one for full live load and one for sustained live load). I was asking about which code or codes I might be able to find a reference to sustained live load in. Thank you.

 

[JAE]

Usually geotechnical engineers will provide two different capacities for, as you say, D + Full LL and for D only (or sometimes for D + 1/2 LL.

None of this is in the code - it is simply a traditional way geotechs attempt to utilize short term vs. long term stresses in soils that fail with long term sustained loads. So there isn't a code definition here and the best bet would be to contact the geotechnical engineer and have them "go on record" as to what they mean by "sustained" loading - document it - and move on.

 

[Skicat]

Thanks for your help JAE. Now that you mention it, it does seem logical to ask the geotech what they deem "sustained" rather than try to guess. Thanks again.

 

[swivel63]

i've always used about a quarter of the live.