Do we need to amplify interstorey drift in ETABS with behavior factor? (Eurocode)

[ITsSB]

As stated on (Eurocode 4.3.4) seismic displacements from linear analysis should be multiplied with displacement amplification factor equal to q (behaviour factor). So my question is, do we need to manually amplify the storey drift reported by etabs with the behaviour factor or is it automatically amplified.

 

[hardbutmild]

I do not know how ETABS works but you could see what you get if you make a test load case that is not labeled as "earthquake" that produces the same shears in structure. If that is the same (or close to) value as the one that "earthquake" gives then it is elastic, if the difference is q, then it is already taken into account by the software.

Keep in mind that you check displacements for 95 year return period and that storey drifts matter, not the total value.

 

[milkshakelake]

Manually.

You can test this out yourself. Do a simple cantilever column with a mass on top. Use a formula to calculate the drift by hand (deflection of cantilever beam with a concentrated load at the end), and compare it to the seismic drift you get in ETABS. You might have to fugde a diaphragm to get this to work, but it should work as long as all members are pinned and you only have one fixed column.

Another way to test it is to vary the amplification factor. You'll see that no matter what you do, the drift will be the same.

If anyone knows why ETABS asks for an amplification factor, I'd love to know. I don't see it doing anything, anywhere.

 

[HTURKAK]

Your question implies Response spectrum analysis.
The answer is at your design spectrum data. If you defined the spectrum data with applying q (behaviour factor), you need to amplify the storey drift with multiplying with q (behaviour factor) reported by etabs.

This could be done manually ( export displacements to excell and multiply with q ) as expressed by milkshakelake (Structural) OR , run the program with spectrum with q=1.0

Use it up, wear it out;
Make it do, or do without.

NEW ENGLAND MAXIM