Structural Damage Mechanism Reflected in the Time-Frequency Response Spectra

Abstract eng:
Response spectrum relies on the intensity and the frequencies of ground motions to determine the seismic force in structural design. However, the absence of time makes it unable to track the damage development with time and further analyze the damage mechanism. So, 3D “time-frequency response spectrum (TFRS)” was proposed by some scholars as a complement to the response spectrum or a new method for structural analysis. Based on their studies, this paper took 3 typical historical earthquake records as examples to construct the 3D TFRS mesh and contour plots, and used them to analyze the characteristics of the TFRSs of these ground motions and predict the structural seismic behaviors. Then, time history analyses were conducted on a five-story building to validate the conclusions made by the TFRSs. Matlab / simulink was the analysis software used in this study, in which nonlinearity was considered by updating the state space matrix using a simplified nonlinear procedure. Results were illustrated by the number of crossings to different damage standards, response profiles, and hysteretic energy, etc. Results showed that, TFRS could clearly display the time and frequency characteristics of ground motions, with advantages outreached the traditional response spectra; TFRS could explain and predict different structural damage characteristics well in that it could tell what kinds of TFRS would cause what degree of damages, on structural, as well as non-structural components, etc. Thus TFRS is also a useful tool for researchers to choose proper ground motions in structural analysis and design.

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