Displacement analysis(ES EN 1998:2015): If elastic analysis is performed the displacement induced by the design seismic action shall be calculated on the basis of the elastic deformation of the structural system by: dₛ=qd*dₑ (definition of terms can be seen from the above picture) What one should consider is the value of qd. Two things should be keept in mind about the value of qd: I. It can be assumed equal to q II. qd is larger than q if the fundamental period if the structure is less than Tc. Displacement analysis(ES EN 1998:2015) 2.If static and dynamic non-linear analysis is performed, the displacement obtained directly from the static analysis without further modification can be used. Related to displacement analysis, the design story drift in the calculation of the interstory drift sensitivity coefficient(θ) should follow the principles stated in ES EN 1998:2015, Art. 4.3.4( which is discussed above).