Shear Capacity Of Connections Of Post-Casted Beams Connected On Existing Reinforced Concrete Columns

Post-casted beam connected on existing reinforced concrete column is a method of strengthening and rebuilding, it casts the beam onto the side of column through the technique of inserting reinforced bars, it is hoped that the joint of beam-column will be rigid. In order to transfer the shear of beam efficiently, different kinds of connections can be used in the joint of beam-column. But the joint of beam-column is always the weakest part of the structure, so the connections of beam-column will impact the seismic behavior, monolithic and stability of the whole structure.At present, the researches on the connections of beam-column, mechanics characteristic and the methods of shear calculation are few, so the theories for engineering design are scarce. Therefore, a total of 9 tests were conducted on three kinds of full scale beam-column connections, including tooth-grooved connection, sticking steel plate welded angle iron connection and roughened interface with inserting bent-up bars connection. Studied the mechanics behavior and deformation characteristic of the three kinds of connections at different shear-span ratios, compared the behavior of different connections at the same shear-span ratio, and the behavior of the same connection at different shear-span ratios.For the tooth-grooved connection, when the shear-span ratioλ< 0.5, it happens shear failure of the tooth-groove, the section of tooth-groove is the dominance section; when the shear-span ratioλ≥0.5, it happens shear-flexural failure of the post-casted beam, the section of tooth-groove is not only the dominating factor, it also depends on the strength of post-casted beam. For the sticking steel plate welded angle iron connection, when the shear-span ratioλ≥0.5, it happens shear-flexural failure of the post-casted beam, there is no shear slippage between steel plate and column, the shear capacity of connection lies on the strength of post-casted beam.For the roughened interface with inserting bent-up bars connection, when the shear-span ratioλ≥0.5, the monolithic beam shows shear-flexural failure, and the post-casted beam shows shear-flexural behavior. The section of connection can not mainly determine its shear capacity.The test results indicates that the roughened interface with inserting bent-up bars connection has higher shear capacity, and it shows better monolithic and higher rigidity, so this kind of connection has the same behavior as the monolithic joint.According to the test results, the formula used to calculate the shear capacity of connections are proposed in this paper, it is shown that the theoretical values are in good agreement with that of the test one, and it can be used as reference in engineering practice.