Scaling up Dynamic Base Shear from ETABS

[KenStructural]

I'm currently using ETABS for the analysis of a 10 storey building and I'm about to scale up the dynamic base shear, it's just that i didn't know on how to extract the correct static base shear and its corresponding dynamic base shear from ETABS. If i understand it correctly for X-Direction Scale factor using UBC1997 EQX (static base shear) and Response Spectrum Base Reaction SPEC1 F1=(Mode=All) from Show Tables options to extract the proper base shears from ETABS. Please let me know if my understanding is correct.

 

[PicoStruc]

There is different phylosophies about scaling dynamic response.

Case 1) Some engineers scale the 3D Base shear vector Resultant.

Case 2) Other engineers scale the 3D Base shear Direction Component

Case 3) In my case, I lock the 3d Model into 2D state (remove z-rotation and perpendicilar direction translation), redo my response spectrum combination, and scale the studied direction response. Use the scale factor calculated in unlocked (full 3D) model. Redo for all direction.

In my opinion :

Case 1 make no vectorial logic (torsion related)
Case 2 is too much conservative (safe)
Case 3 is more logical for me (comparing in 2D world because equivalent procedure is 2D !)

This discussion is relevent when response softening due to torsion behiavor is important (excentric SFRS) !

 

[KenStructural]

PicoStruc,

What it if I'm arriving with a scale factor of say 90, coz some of my jobs I'm arriving with 10 or below scale factor. Is it acceptable it the scale factor is around 90 or greater?

 

[PicoStruc]

Dynamic shear / Static shear value are usually around 0.75 to 1.5

What to do with that value should be defined in your local building code.