When to use over strength?

[js41645]

The ASCE chapter 12 provides formulas for calculating over strength values but gives no information on when over strength is required. Anyone know when and when not to calculate over strength?

 

[JLNJ]

There are special load combinations for certain elements which require overstrength. Look for those which use Omega.

 

[TDIengineer]

Overstrength typically is applied to those members that we want to remain within the elastic zone, even during a seismic event.

For structures in Seismic Design Cat "D", all drags and their connections are design for overstrength, for example.

Review your steel seismic provisions, several elements that are part of the SLRS require omega design (AISC 341-05)

Your question is extremely broad in nature and isn't one typically asked by a practicing engineer...btw.

 

[CELinOttawa]

Ask your supervisor.

 

[wannabeSE]

Load combinations with overstrength are used when the code specifically requires its use. For instance, look at the section on collectors in chapter 12 of ASCE 7. With steel design, AISC 341 uses the term "amplified seismic load" instead of overstrength.