ASCE horizontal seismic component 1

[ramihabchi]

Hi.
In ASCE are the overstrength facrors that applies to horizontal component of seismic load are not required when using modal response spectrum anslysis?

 

[HTURKAK]

Overstrength factor is used for some special elements or connections ( covered in section 12.4.3 ) for the following cases;

- The elements supporting discontinuous frames and walls be designed using load factors that include the overstrength factor Ω o when a Type 4 vertical irregularity exists ( look 12.3.3.3 )

- The foundation and other elements contributing to the overturning resistance of cantilever column structures shall be designed with the overstrength factor ( Section 12.2.5.2)

- The collector elements, their splices, and their connections to resisting elements (Section 12.10.2.1 )

- AISC 341 and ACI 318 Chapter 21 which trigger the use of the overstrength factor in load combinations (e.g. steel piles, grade beams ..etc)

When the overstrength is applied to all elements and connections in the structure and considered in standard load combinations , ( in Section 12.4.2 ), Redundancy , which is penalty for less redundant structures.