In a Seismic analysis, we design a structure at Design Basis Earthquake (DBE) level considering the fact that the structure dissipates energy in inelastic deformation. Generally we perform a 1st order analysis. Response Spectrum is also a 1st order analysis. When we think for stroey drift at the inelastic state, the deformation in the structure are quite higher than that we arrive from the analysis. In a Response Spectrum analysis, we provide a direction factor which is equal to (Z/2)x(I/R). The factor 2 is to bring Maximum Considered Earthquake (MCE) to DBE level and again reducing the forces considering that the structure undergos inelastic deformation. But, in the analysis we are not in a position to capture that deformation as it will be higher than the deformation / displacement computed during the analysis. Thus, we need to increase the deformation / displacement by multiplying the R, response reduction factor.
CHECK STOREY DRIFT 5
Or,
CHECK STOREY DRIFT 3
Command instructs the program to increase the displacement value by multiplying the Response Reduction factor which is 5 or 3.
The responses computed form a Response Spectrum analysis are absolute maximum quantities. There is no meaning of relative storey displacement computation with these values. Thus, the program is restricting users from computing storey drift from a Response Spectrum load case or a load combination where it is considered to be a part of it.
CHECK STOREY DRIFT 5
Or,
CHECK STOREY DRIFT 3
Command instructs the program to increase the displacement value by multiplying the Response Reduction factor which is 5 or 3.
The responses computed form a Response Spectrum analysis are absolute maximum quantities. There is no meaning of relative storey displacement computation with these values. Thus, the program is restricting users from computing storey drift from a Response Spectrum load case or a load combination where it is considered to be a part of it.