dynamic analysis

[CHAKKOUR]

Hi,

When i run a dynamic analysis, should i erase the combinations that include the static earthquakes loads after scaling the base shear and leave only the combinations including Spec X and Spec Y ??

And why when i import the loads towards safe, i dont have the possibility to run the loads coming from Spec X and Spec Y while my structure was checked based based on the spectrum ??

Thanks for the help

 

[saeedHR]

you don,t need to delete the static load combinations. as long as you don't include them in the design combinations they don't affect your design.

Dynamic analysis results are always positive while the reactions on the foundation due to earthquake can be either positive or negative. therefore you should be aware of this while you export your results to safe. some engineers design the foundation acccording to the results of static analysis only.

 

[CHAKKOUR]

Thanks for the reply. Even if u want to design ur foundation as per the dynamic forces, u can not on Etabs because u can import only the static forces due to the earthquake.

if u're in high seismic zone, do u design ur foundation to remain elastic by multiplying the forces due to the quake by Omega the overstrength factor ?? Thank u