Issue 29

W. Guodong, Frattura ed Integrità Strutturale, 29 (2014) 376-384; DOI: 10.3221/IGF-ESIS.29.33 383 (a) The displacement course of main span at X direction. (b) The axial force response of back span unit at Z direction. (c) The axial force response of main span unit at Z direction. (d) The axial force response of main span unit at Z direction. Figure 4 : T he comparison diagram of axial force response C ONCLUSIONS ompared with traditional pseudo excitation method, the new pseudo excitation method directly obtained through the absolute displacement based on statistical linearization could sufficiently consider structural nonlinearity and make its seismic analysis results be more close to actual situation; secondly, absolute displacement needs not to be discomposed into quasi static displacement and dynamic relative displacement during calculation, and quasi static modal matrix needs not to be calculated when constructing virtual stimuli for harmonic response analysis, it could be directly applied in general finite element analysis software and convenient for the application of pseudo excitation method in actual engineering. After system linearization, the node response power spectral density obtained through calculating with absolute displacement method and random vibration method is basically the same, and it demonstrates the correctness of the absolute displacement method, and the accuracy of response power spectral density outputted in calculation depends on the type of input excitation. Compared with dynamic time history method and the absolute displacement after linearization method, spectrum analysis does not take into account the nonlinear structure, the value of node displacement response and the unit axial force response are too small, it demonstrates that nonlinearity has great influence on seismic performance of structure, and seismic analysis of bridge structure must be taken into account. The response value of node displacement and the unit axial force calculated through the absolute displacement method and dynamic time history method after linearization are basically the same. It demonstrates that the pseudo-excitation method directly solved through absolute displacement based on statistical linearization is equivalent to the dynamic time history method, as they can effectively analyze and study the seismic behavior of the nonlinear system. One point needs to distinguish is that performing harmonic response analysis with absolute displacement method is the required stimuli when taking frequency as interval input, while the dynamic time history method is the seismic wave data established by taking time as interval, but their essence is the same. C