Thank you all for your answers. My site was class D. I followed the code because it was my first time doing this kind of analysis but now i know that next time i'll use the site values right away.
Because in this case using the site spectrum accelerations results in a higher value of the static base shear. So I had to redo my analysis using that higher value..
Thanks again!
Thank you very much for your answer WillisV. Now, 11.4.7 allows me to use it. But do I have to? I am being required to do so and I do not see where it says it is mandatory.
I am performing a Modal Response Spectrum Analysis using a design spectra developed for the site. ASCE 7 Section 12.9 requires that the value of the base shear not be less than 85% of the base shear obtained using the procedures of Section 12.8. If I follow section 12.8, I end up calculating a...