Which Spectral Shape Really Matter to Predict Nonlinear Structural Response: Application to Steel Frames

In this paper, several vector-valued ground motion inte nsity measures based on a parameter to characterize the spectral shape named N p are analyzed. The parameter N p is commonly used to repres ent the spectral acceleration response spectra in a range of periods, and in the present study this parameters was used to discuss which spectral shape is more related with a specific perfor mance parameter corresponding to maximu m and energy demands. For this aim, vector-valued ground motion intensity measures based on N p through different type of response spectra such as: pseudo-acceleration, pseudo-velocity and i nput energy are analyzed. The efficiency of the vectors to predict the nonlinear response of several steel frames subjected to narrow-band motions from the soft soil of Mexico City is compared. Finally, an approach to predict the nonlinear respons e of structures dominated by higher mode s of vibrations is proposed.