“Strong Column Weak Beam” Measures of 7 Earthquake Intensity RC Frame Structures Under Bi-directional Horizontal Seismic Excitations
Yang Hong1, 2, Ren Xiaojun3, Bai Shaoliang1, 2
1. School of Civil Engineering, Chongqing University, Chongqing 400045, China;
2. Key Laboratory of New Technology for Construction of Cities in Mountain Area(Chongqing University), Ministry of Education, Chongqing 400045, China;
3. Chongqing Research & Design Institute of Sino-Coal International Engineering Group, Chongqing 400016, China
Based on the damage characteristic of Wenchuan earthquake that plastic hinges of reinforced concrete frame structures developed prevalently at column ends, the influences of “strong column weak beam” measures and super intensity earthquake on seismic performance of structures are analyzed. Regular spatial frames of 7 earthquake intensity 0.1g region and 0.15g region were designed according to the specifications of the 3rd class seismic measure in Chinese code, respectively. By increasing “strong column and weak beam” measures gradually, five examples of each kind of 7 earthquake intensity frames were obtained. Based on the OpenSees framework, nonlinear responses of every frame under bi-directional horizontal earthquake excitations were calculated. The results showed that when the “strong column and weak beam” measures of code GB50011-2001 is adopted, for 7 earthquake intensity 0.1g region frame, the quantity of plastic hinges is few, almost all of the plastic hinges developed at the column end under rare earthquake, while for 0.15g region frame, quantity of plastic hinges is larger, plastic hinges rarely appear at beam ends. When the value of the moment amplification factor of column end of the 3rd class seismic measure is improved according to the seismic code GB50011-2010, almost no improvement of plastic hinges distribution can be found. The characteristic of plastic hinges distribution of 7 earthquake intensity frames designed by the “strong column and weak beam” measures of code GB50011-2001 under super intensity earthquake is plastic hinges developed prevalently at column ends, which is consistent with damage phenomenons of Wenchuan earthquake. For the frames of 7 earthquake intensity, this dangerous plastic hinges distribution characteristic is result from the comprehensive effect of smaller combination moment of beam ends, bigger influence of reinforcement of site casting slab, too weak “strong column and weak beam” measures and super intensity earthquake.
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