Collector elements (ASCE7)

[VijayandVijay]

Iam working in PEB industry, when we are designing the a building with Seismic load resistance system.

As per ASCE7 (sec 12.10.2) specify the over strength factor is applicable for collector elements (spices, connections, [highlight #FCE94F]Bracings[/highlight] etc.,)

We are using the Metal building software(MBS), in which it exclude the Roof bracing for above stated seismic provision.
They justified that wall bracing will be max seismic effect when compare to roof bracing, hence it was ignored.

Please anyone comment on above stated.

 

[briancpotter]

Lateral elements resist seismic forces through inelastic (ductile behavior) - thus, your lateral elements will be pushed past the yield point in a seismic event. However, some elements aren't capable of safely resisting seismic loads in an inelastic manner. From the commentary on chapter 12:

Some elements of properly detailed structures are not capable of safely resisting ground-shaking demands through inelastic behavior. To ensure safety, these elements must be designed with sufficient strength to remain elastic.

The overstrength factor is used to ensure an element remains elastic. My interpretation is that this requirement doesn't disappear if the wall bracing reaches it's maximum load first, so the roof braces should be designed for overstrength.

Brian C Potter, PE
Simple Supports - The history and practice of structural engineering.
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[VijayandVijay]

Thanks for you response