Ductility Seismic Analysis Of RC Frame Structures Under Different Failure Modes

Under the action of earthquake, the ductile deformability of frame structure is closely related to its failure modes.The earthquake damage survey on May 12th, found that the end-column damage form for many in-situ reinforced concrete (RC) frame structure is more severe than the end-beam, showing a failure mode "strong beam-weak column". According to the code of seismic design of buildings, the expected failure modes of "strong column-weak beam" fail to realize in the RC frame. From the damage as you can see, the frame ductility of "strong beam-weak column" is poorer than the "strong column-weak beam" on the same failure mode. In line with the design of Chinese building seismic code, lower coefficient R of elastic-plastic earthquake seismic intensity of the security role in the decision to lower the overall structure of the yield of standard size and structure of the ductility demand. In China, the specification of different ductility is all taking the same R value, namely R=2.86. On the basis of R-μ-T relation that makes some "strong beam-weak column" under the framework of ductility, which cannot meet the expectedly standard ductility demand, leading to the unsafe design of the for RC frame structure based on the existing specifications. In this paper, the core work to this problem is completed as follows:(1) This study found that the "strong beam-weak column" phenomenon leading to poor ductility framework is related to the low reliability of RC frame columns.In order to demonstrate the reasons for this phenomenon, this paper analyses the reliable indexes of seismic bearing for RC large eccentric columns in the 2010 and 2001 version of seismic code with the random eccentricity. The results show that the low reliable index is an important factor affecting the structure ductility according to the 2001 version of the seismic code design.(2) In SAP2000, the framework establishment of cast-in-situ floor or not is respectively used to simulate two different failure modes, such as "strong beam-weak column" and "strong column-weak beam" under the action of rare earthquakes. According to Pushover analysis on the structure of the base shear-top displacement, capacity spectrum and demand spectrum curve and the development process of structure plastic hinge, it makes an analysis on R-μ, relation comparing with the change rule of ductility factor under two different failure modes, thus revealing that if the "strong column-weak beam" failure mode is hard to get, it is insufficient to adopt the fixed value R=2.86 of Chinese seismic design code.