Experimental Study On Seismic Behavior Of RC Eccentric Sandwich Beam-Column Joints

It is prevalent that concrete strength of column is stronger than concrete strength of beam in tall building frame structure. The conventional frame joint with the joints'concrete are the same strength as the columns'affect the project quality. Instead, the new construction methods (the joints'concrete are the same strength as the beams') brings many benefits, such as simplifying the construction process, shortening construction duration and improving construction quality. However, the will lead to joint lower than the column. Consequently, the so called sandwich joints are resulted in. A few researchers have carried out both static and cyclic loading experiments of such sandwich joints, has laid the foundation on application in pratical engineering of sandwich joint. However, there have not been tests for sandwich joints with eccentricity of beam and column.Six eccentric sandwich joints of two groups of different eccentricity were tested under quasi-static loading, integrated seismic performance of these eccentric specimens are studied, such as the crack development, displacement ductility, energy dissipation and their shear capacity and so on. Based on these analysis results,design method also be explored.The main conclusions and advices are followed:①The displacement ductility of the all eccentric sandwich joints is more than 3.5. The performance of eccentric sandwich joints is good under cyclic loading.②Failure pattern of eccentric sandwich joints with the joints'concrete are the same strength as the beam'is caused by beam-end failure; Failure pattern doesn't changed.③In the design process of story drift with traditional calculation method, due to the concrete strength of eccentric sandwich joints is less than the traditional joints, if value close to the limits, the stiffness of structure should be increased.④when the stirrup is too dense to construct and design, X bars could assumed calculational shear of the joints with the stirrup.⑤The performance of the second group is better than the first group's, such as displacement ductility and energy dissipation behavior. Experimental results showed that eccentric sandwich joints connecting spread-end beams can result in superior seismic performance.⑥In the design of eccentric sandwich joints, in order to satisfy the requirement of displacement ductility and energy dissipation behavior, diameter of beams'bars and shear compress ratio should be controlled.⑦To the seismic grade lower eccentric sandwich joints,due to the shear capacity is less than the conventional joints, shear capacity should be calculated.