www.sefindia.org

[hemalmistry]

(1) Drift limit for working wind load combination is given as H/500 which shall be hi/500.

(2) There is drastic change in drift limit compared to draft code. Drift limit for wind and seismic load are different. Drift limit for seismic case is now more or less similar to ASCE 7 considering factored seismic load and deflection amplification factor of 5. However according to ASCE, deflection amplification factor is different for different structural system. So in our case drift limit shall be different for different structural system as our drift is elastic drift and we can only change limit.

According to JGJ 3_2010, drift for wind and seismic load for buildings upto 150 m height are different for different structural system. For buildings above 250 m (code exceeding building in our case) is same (hi/550) for all structural system and for buildings between 150 to 250 m height linear interpolation is suggested.

ASCE 7 also have same drift limit for wind and seismic loads.

(3) Designing a building in any software with different drift limit and different stiffness modifiers for structural element for wind and seismic load in single model will be difficult or not possible. We need to have two separate model for wind and seismic case and design shall be based on combination forces extracted from both model.

Regards
Hemal Mistry
Surat