Scaling Response Spectrum

[slickdeals]

Folks,
I am analyzing a building using a Response spectrum method. I have conducted my ELF analysis and have my static base shear. I have very little shear in the Y direction in the X direction quake and very little X shear in the Y quake.

However, in my RS analysis I have quite a bit of shear in both directions even though the spectrumis only defined having force in one direction.

How will I go about scaling my dynamic base shear? Should I not consider the shear in the direction orthogonal to direction of applied load?

Thanks

 

[prsconsultant]

Dynamic analysis captures the torsional behavior of the building. If a building is poorly laid out, the shear in Y for X-direction spectral analysis could be as high as 90%.
YOU MUST INCLUDE BOTH X & Y COMPONENTS.

Follow thread 487-204481 for scaling info.

LET ME KNOW IF YOU NEED MORE INFO.

 

[slickdeals]

@PRS:
Do you mean to say that when I scale my X response, I should scale it such that it matches the X static and do the same process for the Y response as well?

Or is the process different?

 

[edwin17th17]

i also had the same problem before when i was doing equipment steel structure..
i was told to reconfigure the structural framing to achieve almost zero dynamic base shear for Y dir if doing X response dir, vice versa..
but i never actually able to reduce it.. =)

 

[slickdeals]

@edwin,
Even if you have a very regular structure, as long as your global response spectrum direction does not match your structure's global orientation, you will get shears in both directions.
and like prsconsultant says, it captures torsional behavior

 

[prsconsultant]

Slikdeals

You will have different scaling factor for X & Y directions. I usually scale the spectra so that the dynamic effect would be scaled in all aspects. I will post a sample calculation regarding this.