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 01)
► Image | Edit Parameters of Edition https://www.dlubal.com/en/img/033442
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 factors 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 02)
► Image | Create Seismic Load Case https://www.dlubal.com/en/img/033443
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 03)
► Image | Overstrength Design Situations https://www.dlubal.com/en/img/033444
4) In the Load Combinations tab, verify that the correct factor(s) has/have been applied. Factors are also shown in the Result Combinations tab, if applicable. Click OK to exit (Image 04)
► Image | Verify the Overstrength Factor https://www.dlubal.com/en/img/033445
5) The final step is to assign the applicable limit state type to the overstrength design situation. For members without assigned seismic configuration, select the "Strength limit state" (LRFD or ASD) as the Limit State Type.
For members with assigned seismic configuration, use “Earthquake limit state – overstrength” (LRFD or ASD) (Image 05)
► Image | Overstrength Limit State Type https://www.dlubal.com/en/img/033446