The Correlation Analysis Of Ground Motion Intensity Index And The Nonlinear Response Of Reinforced Concrete Frame

The selection of earthquake wave is an essential task for nonlinear dynamic time history analysis, and the reference index in the choice of earthquake wave should be able to reflect the effects of ground motion on the structural nonlinear response. Based on the correlation analysis between earthquake intensity index and structural response, the capacity of these indexes to reflect the effects of ground motion on the structural nonlinear response is studied. The main works in this paper are as follows:â‘ In the 3D response spectrum, the sub-maximum response of SDOF structure not found in the conventional response spectrum is added to consider the duration of ground motion, and 3D spectral intensity is obtained from the volume integral of the 3D response spectrum under the range of 0 ~ 6s cycle. In this paper, the 3D spectral intensity is improved through adjusting the integral range to T~3T, in which T is the initial period of the structure.â‘¡By definition, making peak at special range of 0.1 ~ 0.5s in the response spectrum 2.5 times smaller, the effective peak acceleration (EPA) is obtained. Furthermore, the effective peak acceleration is improved through adjusting the cycle range of T ~ 3T, where T is the initial period of the structure.â‘¢Characteristics peak is the intensity index of ground motion that proposed to consider the concentration of seismic energy on time and frequency. Through the L-P rapid wavelet transform method, the maximum peak of signals namely characteristics peak is obtained by reconstruction on a few wavelet components which have the largest impact on the structural response. Considering using low-frequency wavelet components near the cycle of structure to reconstruction or adjust their weight value, the characteristics peak is adjusted. In order to check whether the maximum structural response very closed to characteristics peak, reconstructed signals and the structural response are compared and analyzed along the time axis in the process to investigate whether the maximum structural response caused by the characteristic peak.â‘£Four models of RC plane frames are chosen to be researched, which are designed with the idea of economic and reasonable and whose cycle range is 0.73 ~ 2.38s. Establish these frameworks model with Opensees, select 60 actual earthquake records according to certain principle, then carry on dynamic nonlinear response analysis and take the maximum lateral displacement as the index of structural response. It found that the correlation between improved 3D spectrum intensity, EPA and structural response is significantly increased after correlation analysis between earthquake intensity index and structural response. The correlation between adjusted characteristics peak and structural response is equivalent to (even better than) the improved 3D spectrum intensity and EPA, which exactly reflects the influence of earthquake ground motion on the nonlinear response of structure. From the subsequent analysis, it show that the maximum response is not near the characteristic peak in a few cases, or the peak value in the corresponding position on the maximum response is equivalent to the improved characteristic peak, or there is little difference between structural response in the corresponding position on characteristic peak and the maximum response. Therefore it can be concluded that the maximum structural response is indeed caused by the characteristic peak. As with the selected framework, 60 ground excitation records and other 30 for validating, most of the structural response can be explained by the characteristic peak. So, improved 3D spectral intensity, effective peak acceleration and the characteristic peak, all can serve as the reference indexes in the choice of earthquake wave.