Hi! I did an analysis dynamic response of a simple supported beam under moving load. And, i used mode superposition method in time domain. And now, i want to do an analysis that uses mode superposition method in frequency domain. I calculated DFT of Loading P(w) and Frequency Response Function H(w). And then, to obtain response according to modes I producted H(w).P(w) (i.e. X(w) = H(w).P(w)). And of cause, then, i do IFFT of X(w) to obtain response in time domain x(t). But, x(t) that i obtained when calculated through frequency domain is different with it calculated in time domain. Of Cause, my question is quite silly when you read it. But my purpose is "Can somebody who acknowledge on superposition method (in Freq domain) help me?". Why first value in second figure is not equal to zero like first figure? Thank you so much.
