Response spectrum vs. automated lateral EQ force for UBC97

[arboi]

Hey
In order to compare analyzing response spectrum vs. automated lateral EQ force for UBC97 standard , I modeled a plane RC frame with sap2000 v14
The parameters needed were taken to be the default in the program
The lateral max. deflection was about 13 times bigger in the response spectrum analysis then in the static case.
Is this reasonable?
If not where was I wrong?
The SDB file is attached
10x

 

[stressed]

Under Define>Mass source you specified DEAD load in addition to element weight. That selection double counted selfweight for mass. Select the 2nd option "from loads" for mass using your DEAD case. Also, RS results are scaled to match static equivalent base shears per code. You used a full G in your RS analysis

 

[arboi]

Thanks a lot stressed
I think I got what was wrong
I set the seismic coeffitions Ca and Cv to 0.4 for both methods.
But I missed another factor called overstrength factor R in the static method.
this factor relates to the ductility of the structure and playing with this factor can change the results of the static method.
Thanks again for your usefull comment about the mass source

 

[IJR]

Arboi

whenever you have time, it is best to make rough estimate before you start automatic eq analysis. Some things you define in your model may always be a great source of error. One of the worst culprit, is the degree of freedom. Because a few people really care about this when modelling in sap2000.

respects
ijr