| Summary: | 碩士 === 國立交通大學 === 土木工程系所 === 106 === During the Chi-Chi earthquake in Taiwan, it was observed that the near-fault ground motions with pulse-like signals caused some serious damages to bridge structures. This study proposes revised engineering design parameters including strength reduction factor, R, yielding strength factor, Cy, displacement amplification factor, Rd, which could provide suitable design solutions to minimize damages to bridge structures during near-fault earthquake motions. The analysis involved collection of related seismic records, focusing on the aforementioned factors. Using the commercial software, Bispec, we were able to conduct a dynamic time history analysis. This study also provided four criteria including: (1) signal processing method, (2) orientation of the records, (3) hysteretic model, and (4) numbers of records, in order to compare with the current code.
Ultimately, the study would find the final standards necessary to revise the current formula based on analysis results. Based on analysis results, this study applied to the data from the Pacific Earthquake Engineering Research Center (PEER Center) and chose the 7 sample size. It also selected the maximum velocity orientation and MC model. In addition, except for the conditions mentioned above, for typical structures, the period was within 3 sec, and was around 3 to 5. Thus, the revised formula used these ranges as a factor for consideration. For R, this study adjusted the demarcation of the period and the segments for equivalent energy and equivalent displacement to approximate the analysis results. For Cy, this study found that the relationship between Cy and S_aM/F_uM could acquire the suitable curve to fit the analysis results. For Rd, the analysis results indicated that it could not fill the requirements of using the current formula to adjust. Therefore, this study used the nonlinear regression analysis to propose the formula. To sum up, the engineering design parameters were all revised according to the analysis results. In addition, except for Rd, this study used the original pattern of the code to revise the formula and expected to make good use of the simple curve in the application of seismic engineering. The present study definitely has its limitations. In order to obtain more reliable and objective data, research on far-field ground motions including analysis should be conducted in the future.
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