Story shear/story force not equal to response spectrum base reaction 1

[Raypeace]

Hey all,

The story shear and the response spectrum does not match. What should I consider in order to fix this? Aren't they supposed to be equal in the first place?

 

[Backcheckrage]

There are several topics on this forum regarding this.
How far are they off?
My understanding is that the response spectrum results of base reactions are an envelope and would be greater than the story shear...
... you should compare the base reaction shear versus a "cut" of the lateral force resisting members just above the base supports.

 

[Raypeace]

The story shear is around 20% greater that the RS Base reaction. Shouldn't it be the other way around?

 

[PicoStruc]

Well coded software outputs for reaction : the combination of reaction for all modes and for story shear : the combination of story shear for all modes.

So it's is two different values ! Similar to the combination of story drift for all modes is not equal to the drift based of the combined story displacement !

CQC or SRSS combination technique give probable response... Nothing is in equilibrium...

Yes, this is pain in the....