Experimental Study Of Calculating Width Of Equivalent Beam And Interior Column Joints For Slab-column Structures Subjected To Horizontal Forces

The advantages of the reinforced concrete slab-column structures are having a good effected on architecture, reducing floor height, and convenient construction. But it's seismic behavior is not well and some problems must be improved. In this paper, the calculating width of equivalent beam ,it's seismic behavior and the judgment method for failure modes of interior slab-column joints are studied. The main contents are as follows.1,When the equivalent frame model is modeled for slab-column structures subjected to horizontal loads, the mistake on the calculating width of the equivalent beam in the famous works《Design of Concrete Structure》by A. H. Nilson is pointed out. The equivalent beam is a differ-sectional beam, and the width of equivalent beam of slab intersected width column is really smaller than that of mid-span slab. Simultaneity, for convenient application, the calculating method about the width equal-sectional equivalent beam is presented in accordance with the principle that the stiffness of equivalent beam equals to the stiffness of slab.2,A new viewpoint is given that the main factor of effecting on the equivalent width coefficientαis not the geometry dimension of the slab and the column suggested by some researchers, but the ratio of torsional stiffness of torsional member to the flexure stiffness of slab K t / Ks. The coefficientαwill increase with K t / Ks. By means of the elastic finite element analysis, the calculating formulas on equivalent width coefficientαfor the interior frame of flat plate structure are given out.3,Tests on three specimens of interior slab-column joint subjected to the horizontal reversed low-cyclic loads are carried. The test results show that the main failure modes of interior joints are flexural failure and punching failure. By the study of the hysteretic behaviors, ductility, and energy dissipation of the interior slab-column joints ,a viewpoint is presented that the poor seismic behavior of the slab-column is due to not only its weak lateral stiffness but also the weak ductility of the joints.4,The limited moments of the joints are obtained respectively by the method of《code for design of concrete structures》(GB50010-2002)and the plastic limit state method, when the punching failure mode and the flexural failure mode occurred. By means of this ,the method of judging the failure modes of interior joints is given out.