Experimental Study And Analysis On Seismic Performance Of RC Box Columns

RC (Reinforced Concrete) box columns, with the characteristic of closed section, have excellent spatial mechanical behavior. Therefore, RC box columns are widely used. However, Because of the randomness and multidimensional of earthquake, the only study of the seismic performance of RC box columns under unilateral loading is often not enough. For this reason, to compare and study the seismic performance differences of RC box columns under bilateral horizontal loads and unilateral loading are very meaningful. Based on the study both experimental and analytical by some researchers at home and abroad, combined with physical prototype columns of Jingyue Yangtze River Bridge, six RC box columns which primary parameters are stirrup ratio and reversed horizontal loading angle are designed and produced, then pseudo-static tests are carried out for them. In this paper, such seismic performance as ductility, hyseresis curve, skeleton curve, dissipating energy capacity, etc. of RC box columns is studied. The dissertation involves mainly the following investigations and corresponding results:(1) The backgroud of the subject selected is introduced by summarizing the progress and conclusions of previous studies on seismic performance of RC box columns at home and abroad, and thus purpose of this paper is brought up.(2) In the experiment, the specimen's entire process from the first crack to destroy is observed. The cracking load, yield load and ultimate load of specimen is recorded. The crack development, longitudinal reinforcement strain, hoop strain at the various stages are depicted and measured respectively.(3) Influence of stirrup ratio and horizontal loading angle on the seismic performance of RC box columns is studied. The characteristics of the hysteresis curve, skeleton curve, load degradation curve, stiffness degradation curve and moment-curvature curve of column bottom are analyzed, and displlacement ductility factor and dissipative coefficient are acquired. It is proved that RC box columns shows good seismic performance, both stirrup ratio and horizontal loading angle have impressive effect on seismic performance of RC box columns.(4) Based on the experimenal study on the seismic performance of RC box columns, constitutive relations of confined concrete and the section layer method, are adopted for non-linear analysis program, by which horizontal load displacement relation of column top are drawn. The correctness of the program is verified by comparing the results of both calculation and experiment.(5) Parameters of axial compression ratio, longitudinal reinforcement ratio, transverse reinforcement ratio and horizontal loading angle of RC box columns are analyzed with non-linear analysis program which is verified by experimental results. The influence of all these parameters on the seismic performance of RC box columns is discussed...