Experimental Study On Earthquake-resistant Behaviors Of Underpinning Joints Of Frame Column

Some buildings that still have subsequent value or historical and cultural significance have to be demolished in the process of urbanization construction and old city reconstruction. The overall shift technology as a new technology has been applied in projects,which can not only let the valuable buildings can be used as usual, but also have no effect on the new town planning.Underpinning technology that is the key to overall shift technology has been widely used in the underpinning of framework building in our country at present. In recent years, our team attained a series of theoretical research achievements on underpinning joints under static vertical load. Few systematic research on earthquake-resistant behaviors had been made besides our team conducted the preliminary study before. The article mainly studied the seismic-resistant behaviors of underpinning joints by the pseudo-static test under low reversed cyclic loading.This test set up seven beam-column joints, with two kinds of axial compression ratio,0.2 or 0.1. And the height of beam is 200mm or 300mm. Besides a joint as a control without any inserted reinforcement, others are with different quantity of inserted reinforcement at combining surface. The paper mainly study on the influence of the earthquake-resistant behaviors of joints by combining surface height, number of inserted reinforcement, and axial compression ratio.Through test, we got the rule of crack propagation and distribution, the displacement and strain curve and the main strain component. According to the test result, we got the failure mechanism of the structure, the hysteresis curve, the percussive skeleton curves, the stiffness degradation curve, the yield load and ultimate load, the displacement ductility coefficient and energy dissipation performance. Through the analysis of these contents, the following conclusions were gotten; The hysteresis curve is like a spindle and the spindle slightly flat with middle slightly pinching. The equivalent viscous damping coefficients of nodes were 0.115,0.124,0.132,0.236,0.182,0.207 and such joints have good performance of energy dissipation. The ductility coefficient of joints were 3.650,3.650,3.871,3.420,3.052,3.467 and all of them can satisfy the requirements of the current specification of basic seismic. These nodes can be used in the engineering. With higher joint surface and more inserted reinforcement,it turns to be damaged by bending. Opposite the height of joint surface is smaller and the quantity of inserted reinforcement is less, it turns to be the node failure. Under certain conditions, the higher the surface height is, the larger the bearing capacity is. The larger the axial compression ratio is, the larger the bearing capacity is. The Inserted reinforced have little effect on bearing capacity.Finally, I summarized the article and gave some advices about this test.