when do I use the ASCE7 Special seimic load?
when do I use the ASCE7 Special seimic load?
(OP)
Reference the ASCE7-02 equations 9.5.2.7.1-1 and 2 The omega factor is a killer me, but ah ha it says to use this load "Where specifically indicated in the standard". Where is it used? Do I have to worry about it when designing a 4 story hotel?






RE: when do I use the ASCE7 Special seimic load?
RE: when do I use the ASCE7 Special seimic load?
RE: when do I use the ASCE7 Special seimic load?
1620.1.6 is an example of a "specifically required" condition....collector elements, their splices, their connections etc.
A simple element of the structure is not required to use the load combinations of 1605.4 unless 1605.4 is specifically referenced for that element.
RE: when do I use the ASCE7 Special seimic load?
RE: when do I use the ASCE7 Special seimic load?
The idea (and I know my good friends in California here will step in if I step in it).... the idea is that you are trying to create a structure where the connections, brittle elements, and key brace elements are detailed to force a more ductile or energy-absorbing type of failure.
One good analogy is to remember how bars of steel are tested in a lab (remember your materials classes?) where the bar is large at each end and tapered down in the middle to avoid failures where the machine grips the bar. The larger ends avoid brittle, non-ductile failures and allow the test to proceed through the plastic zone of the material to get a good stress-strain diagram.
A brace is then similar, you don't want the welds, the bolts, or the gussets to fail in brittle fashion, so they are upsized to make the brace itself be the weak link in the chain of limit states along the load path.
So as you are designing for seismic, keep an eye out for those rigid, brittle areas along your lateral force resisting system and consider using the Omega load combo for them.