Research On Axial Behavior Of RC Beam-circular Tubed Reinforced Columns Joints

In recent years, tubed concrete get developed and widespread use because of its advantage including great compressive capacity and shear capacity, good interlaminar deformability and fire resistance performance and so on.However, the strength of joints will be weak relatively because tube is uncontinuous in beam-tubed concrete reinforced column joints. So, effective improvtion of the strength of joints has a great significance on the use and popularization of tubed concrete. Two types of RC beam-circular tubed reinforced concrete (CTRC) column joints were proposed in this thesis: continuous tube in joint zone and beams with horizontal haunches.Experimental research and finite element analysis hve been carried out for the two types of joints under axial compression:(1) Five RC beam-CTRC column joints with continuous tube in joint zone and two tubed reinforced concrete stub column with the same cross section under axial compression were tested. The parameters of specimens are the types of joint-beams (corner joints,exterior joints and interior joints) and the ways of strengthening tube in joint zone. The failure modes and load-bearing capacity were analysed. Load-strain of specimen curves and load-stress of tube curves were obtained. The results showed that the RC beam-CTRC column joints with continuous tube in joint zone under axial compression occurred shear failure through joint zone or crush failure in columns. The load-bearing capacity of joints under axial compression is4%~11%higher than stub columns,and the ductility is better than stub columns.(2) Three RC beam-CTRC column joints with horizontal haunches under axial compression were tested. The parameters of specimens are the types of joint-beams. The failure modes and load-bearing capacity were analysed. Load-strain of specimen curves and load-stress of concrete curves were obtained. The results indicated that joints with horizontal haunches under axial compression occurred crush failure in columns. The load-bearing capacity of joints under axial compression is7%~15%higher than stub columns, and the ductility is better than stub columns too. (3) The finite element method (FEM) model for RC beam-CTRC column joints under axial compression was established by software ABAQUS. The FEM results were generally good agreement with test results.Based on FEM model, influence of parameters including concrete strength,steel yield strength, steel ratio and height of hole of tube in joint zone on the axial behavior of joints were analysed.