ASCE 7-05 table 12.12-1 story drift

[cg3375]

ASCE 7-05 table 12.12-1 is for allowable story drift.

In an occupancy II wood wall structure, this is saying that I am allowed .025 x wall height for drift (no odd torsional design or high seismic). This means an 18 foot tall wall can have 5.4 inches of drift at the top? Hopefully no glass in that wall or nobody tries to force the upper limits of that design allowance.

Assume all the components meet the l/xxx requirements. Sum the four up (cord, sheathing Gt, nail, and anchor), bring in the amplification factor of 4 for wood walls, and this table seems a bit non-restrictive with tall wood walls. Any thoughts or am I missing something?

Thanks.

 

[JoshPlumSE]

Keep in mind that this is a strength level deflection, not a service level.

This also includes the Cd factor to account for inelastic drift effects of the earthquake.

If you wanted to convert this down to service level deflections akin to wind load deflections, then you'd multiple by 0.7 (to convert to service level) and divide by 4.0 (Cd for a wood shear wall system).

That drops the drift down from 5.4 to 0.95 inches.

Is that more along the levels you were expecting?