ETABS Response Spectrum analysis reaction.

[Hanchai]

Hi, all.

Recently I'm working with etabs and have two question about it.

I modeled 20-story concrete building. I completed modeling and analysis was completed successfully.

To check my modeling I examined reaction - base reaction and joint reaction. I summed joint reaction and compared it with base reaction.

I expected that the result is same, but it was different. Only force in Z direction matched.

Though it was only result for gravity load, the base reaction yields reaction force in X and Y direction and moment in X, Y and Z.

But the summation was joint reaction yields only force in Z direction.

What is meaning of base reaction and why do they yield different result?


After I found that problem, I skipped that problem and decided to take only summation of joint. But there arise another problem

I did spectrum analysis and equivalent static analysis for seismic force. I defined the spectrum and applied it in load case and the static seismic load in load pattern.

But Etabs only yields reaction for static seismic load so I cann't apply scale factor of dynamic analysis.

I'll really appreciate if some of you solve my question. Thanks.

 

[Hanchai]

At least, Please let me know how can I find exact reaction(Base Shear) for the response spectrum analysis.

 

[JasonMcKee71]

You can check the Story Shears table for STORY1, using the Display->Show Tables menu item.

Jason McKee
proud R&D Manager of
Cross Section Analysis & Design
Software for the structural design of cross sections
Moment Curvature Analysis
Interaction Diagrams
Reifnorcement Design etc.

 

[Hanchai]

To JasonMckee71

Yes. I've already read the method in other sources. But in my etabs(nonlinear ver.15.2), I cann't find the story shear in the Table menu.

The only category I can find in my table menu is reaction(base reaction, joint reaction, design reaction) and structure results which contains Centers of Mass and Rigidity, Story Forces, Story stiffness and

Tributary Area and LLRF.

The sources what I saw is written in older version of etabs so, I thought I can find the story shear in other category like base reaction or story force.

I cann't sure that whether the problem comes from problem of my etabs or my etabs model.

 

[cyrus0812]

to Hancahi

You can find it on story response plot and change the case/combo to your spectrum response case and then change the display type into story shear. You can also view the story shear in table format.