Mechanical Properties Of Concrete Filled Steel Tube Truss Composite Beams And Columns

With the help of the heat island effect and the fresh air system,green prefabricated ecological buildings make full usage of some natural resources such as geothermal energy and solar energy to regulate indoor temperature and air.Such kind of buildings feature the advantages of warm winter & cool summer,low carbon emission,energy saving and heat preservation,which is in line with the requirements by the Ministry of Urban and Rural Housing in China to advocate green and low-carbon buildings as well as prefabricated buildings.Considering the demand of building space,the frame-shear wall structures are commonly adopted when constructing green ecological buildings whose columns are often designed to be hollow in order to meet the requirement of ventilation.Some achievements have already been made by domestic and foreign scholars on the mechanical behavior,seismic behavior and related design methods of ordinary reinforced concrete beams and steel reinforced concrete beams used in green ecological houses.However,there is little research on the performance of composite beams and columns with inner steel tube trusses(a new type of steel reinforced concrete composite system with an inner welded steel pipe-steel bar truss and outer concrete).In this paper,the bending behavior of such kind of composite beams and the seismic behavior of such composite columns are analyzed by means of tests,numerical simulation and theoretical analysis.Furthermore,some theoretical design methods of such concrete composite beams with built-in steel tube trusses are presented.The main works and results are as follows:(1)The flexural behavior tests of two control RC beams and six concrete composite beams with inner steel tube trusses on taking beam height and web reinforcement truss arrangement an variables are completed.The results show that the ultimate bearing capacity of the members can be increased by increasing the beam heights,and that the bearing capacity,stiffness and ductility of different built-in systems are mechanically different.In these tests,only the RC300 beams are designed to be over reinforced and feature brittle failure while the other beams all feature plastic failure.Also,it is verified that the experimental concrete composite beams with inner steel tube trusses meet the requirement of deformation limits under normal service scenarios and the requirement of the ultimate bearing capacity.(2)The ABAQUS finite element analysis software is used to simulate the concrete composite beams with inner steel tube trusses.The validity of the simulated model is verified by comparison of both the experimental and simulated results.Moreover,some theoretical design methods of this kind of composite beams are put forward based on the stress distributions of steel pipes and steel bars provided by the FE model.(3)The design and quasi-static tests of two concrete composite hollow columns with inner steel tube trusses are completed.Some mechanical properties of the columns,such as the hysteretic curves,stiffness and its degradation,strength degradation,energy dissipation capacity and ductility,etc.,under different axial compression ratios are investigated in this paper.The test results show that the design meets the seismic requirements.