Comparative Analysis On Control Methods Of Earthquake-induced Failure Patterns Of RC Frame Structures In China And USA

The structural damages observed in the2008Wenchuan Earthquake indicated thatthe code preferred failure patterns of structures were rarely realized, which has attracteda great deal of attention of the researchers and engineers. Theoretical and experimentalresearch has been carried out ever since then to investigate the effectiveness of the codeprovisions for the control of structural failure patterns. In addition, researchers have alsoturned their eyes on countries that are advanced and experienced in seismic design andconstruction such as Japan, USA and New Zealand. The philosophy and methodology ofthe seismic design codes of these countries were examined and compared with theChinese seismic code in order to find the disadvantages of the Chinese code and theimprovement that can be made.Based on the comparison of the seismic design philosophy and methods in Chinaand USA, archetype RC frame structures were designed conforming to the codes ofChina and USA respectively and corresponding to Chinese seismic fortification level8with a peak ground acceleration of0.2g. The influence of the amount of transversereinforcement on the seismic behavior of the RC frames was considered. The designedarchetype structures were analyzed under various earthquake records and intensity tocompare their nonlinear dynamic responses. The structural failure pattern controlmethods of the two countries were compared in terms of the distribution of plastic hingelocations, development sequence of plastic hinges and severity of the failure. Theeffectiveness of the China seismic design code provisions was then evaluated accordingto the results.The main conclusions can be drawn based on the above-mentioned work:①In USA, the seismic force is resisted by the so-called lateral force resistingsystem. As for the moment frame structures, the perimeter frames that are arranged onthe edges of the structural plan are used as the lateral force resisting system, while theinterior frames only carry the gravity loads. Compared with the space moment framesdesigned by Chinese code, the perimeter moment frames designed by American codehas larger column sizes while smaller longitudinal steel ratios for bottom columns. Thelongitudinal steel ratios for columns at other stories of the frames designed by codes ofthe two countries are very close to each other. However, the American code imposesmuch stringent requirements on the confinement of beam ends and column ends, resulting in a higher stirrup ratio than Chinese code. Judging from the overall designprocedure, the American code adopts the design philosophy of low strength while highductility. The seismic force by American code may be lower than that by Chinese codewhile the seismic measures are much stricter than Chinese code.②According to the results of the elasto-plastic time history analysis ofcomprehensive frame models, the lateral deformation of the frames designed byChinese code is mainly in shear shape while the lateral deformation of the framesdesigned by American code is mainly in flexural shape.③For both plane moment frame and comprehensive frames that represent threedimensional structures, the failure of the models are all featured by a mixed beam andcolumn hinge pattern. However, in the frame models designed by China code, theplastic hinges are distributed on every story. For the frame models designed byAmerican code, the plastic hinges mainly concentrated at the bottoms of the first storycolumns, which is due to the fact that in American code the bottoms of the first storycolumns are allowed to develop plastic hinges for energy dissipation.