Experimental Research On Bond Deterioration Of Beam Bar Of The Interior Joint In Earthquake-resistant Frames

Based on the reversed cyclic loading tests of the interior joints of framework with rectangular column, which are designed according to Code for Design of Concrete Structures (GB50010-2002) and in which four are with high bond condition and one is with large axial load ratio and large shear-compression ratio, the seismic performance of the assemblages were studied that is influenced by large axial load ratio, large shear-compression ratio, high bond condition and high-strength of bars. With the reversed cyclic loading tests of 16 nearly full-size interior joints in reinforced concrete plane frames which have been completed by our study group, the law of bond deterioration of beam bars crossing the joint is analyzed. The propositional formula of the relative length of beam bars crossing joint h(?)/d, which is influenced by axial load ratio % shear-compression ratio, reinforced bar strength and concrete strength, is presented. The specific work and main conclusions we concerned are as following:â‘ One plane frame joint specimen with rectangular column, which is with large axial load ratio and large shear-compression ratio and in which the hoop radio is little lower than that defined in the code has been completed, and the displacement ductility of the specimen is 4.1 in shear failure. Then, it is thought that the seismic performance of joints can be accepted.â‘¡According to the analysis of tests data, in the same condition, the penetrating length is longer, the damage of joint is slighter, the speed of bond deterioration of beam bars crossing the joint is slower, the slip is litter, the viscous damping coefficient viscous damping reflecting hysteretic dissipated energy within single circle is larger and the amplitude of rigidity degrade is litter.â‘¢Because the yield strength of high-strength bars specimens is limited, the differences of seismic performance of the assemblage with 400HRB and 335HRB are not obvious.â‘£With the tests of 21 interior joints which have been completed by our study group, the law of bond deterioration of beam bars crossing the joints, which is influenced by axial load ratio, shear-compression ratio, reinforced bar strength, concrete strength and the relative length of beam bars crossing the joint, is tested and analyzed. By the nonlinear fitting method, the formula of the bond stress Ï„ between steel crossing interior joints and concrete under different loading step is obtained according to the...