Question:
How do I include the overstrength factor(s), Ω-o in the ASCE 7 load combinations?
Answer:
1) Open the Load Cases & Combinations dialog box. Under the Base tab, select the Edit Parameters of Edition option. The default values are set to 2.0 (Image 1)
Case A: To apply the same factor in the X and Y directions, use the generic (no direction) overstrength factor, Ω-o.
Case B: To apply different factors in each direction, use the overstrength factor X and Y, Ω-o,x and Ω-o,y. The generic factor, Ω-o in the first row is not used.
2) Under the Load Cases tab, create a seismic load case with Qe as the Action Category. Next, select the Additional Settings tab and pick the direction (Image 2)
Note: When neither or both directions are activated under the same load case, the generic overstrength factor, Ωo is used. Create a separate load case to apply the individual factors, Ω-o,x and Ω-o,y.
3) Under the Design Situations tab, select the applicable overstrength Design Situation Type. Both LRFD and ASD methods are available (Image 3)
4) In the Load Combinations tab, verify that the correct factor(s) has been applied. Factors are also shown in the Result Combinations tab, if applicable. Click OK to exit (Image 4)
5)The final step is to assign the “Earthquake limit state – overstrength” (LRFD or ASD) as the Limit State Type to the overstrength design situation (Image 5)
