The Study On Torsional Behaviors And Design Method Of Reinforced Concrete Combined Force

With the development of high-rise building, the normal strength concrete and high-strength concrete are applied more and more extensively. It is necessary to study much more behaviors of combined-force member under gone bend, axial press, shear and torsion. By experiment and analysis of 35 specimens, the torsion behavior and seismic performance of reinforced concrete frame column subjected to combined forces are discussed.By tests of 9 specimens subjected to biaxial eccentric compression, shear and reversed torque, the failure modes and the varying laws of cracking torque, original stiffness, ultimate torsion strength and ductility are discussed, with the change of axial stress level and relative eccentricity. Then, the cracking bearing capacity, the ultimate capacity and the deformability of the specimens are obtained.By model experimentation of 14 high-strength concrete frame columns subjected to axial eccentric compression, shear and humdrum torque, of 9 high-strength concrete and 3 high-performance concrete frame columns subjected to biaxial eccentric compression, shear and reversed torque, the behavior of high-strength concrete frame column in warped section are studied the first time, and the mechanism of torsion bearing capacity of high-strength concrete frame column are discussed. Also the failure modes and the cracking torque, original stiffness, ultimate torsion strength and ductility are discussed in this case. The factors affected torsion bearing capacity of high-strength concrete frame column is analyzed too.The seismic performances of normal-strength and high-strength concrete frame column subjected to biaxial eccentric compression, shear and reversed torque are studied. Based on the model experiment of 9 normal-strength concrete specimens and 12 high-strength concrete specimens in this case, the hysteretic property and seismic performance of normal-strength and high-strength concrete frame column are analyzed, and factors that affect the seismic performance of combined torsion member are also studied.In this paper, seismic performances of reinforced concrete members are discussed. Problems of hysteretic property and hysteretic model subjected to biaxial eccentric compression, shear and reversed torque are analyzed. Two important facets of seismic performance, ductility and energy-dissipation property, are analyzed too. Factors that affect ductility and energy-dissipation are discussed in different conditions. The method of establishing hysteretic curve in restoring force model of members subjected to biaxial eccentric compression, shear and reversed torque is obtained. Restoring force model of combined torsion members is established too.In this paper, nonlinear behavior of reinforcement concrete combined torsion members subjected to axial compression, bending moment, shear and torsion is analyzed and researched with nonlinear finite element method. Concrete has been modeled using eight-node hexahedral isoperimetric element andreinforcement element are divided into two cases. Longitudinal reinforcement has been modeled with discrete element and stirrup has been modeled with smeared element. Smeared element, stirrup has been modeled using membrane element in or on concrete isoperimetric element. The constitutive relationship and failure criterion for concrete is the inter-facial model. The function of this model is more powerful, so the model can be used in three-dimensional stress state. Using damage concept to reflect the phenomenon of continuous stiffness degeneracy and nonlinear behavior for concrete, combined material parameters with physical phenomenon of concrete makes the results with the model in three-dimensional stress state for concrete consist with experiment and settles the difficulty of calculate. So this model can simulate all kinds of properties of concrete after loading, such as nonlinear stress-strain relationship for concrete, stiffness phenomenon under cycle load, phenomenon compression and expansion for concrete with shearing, strain soften phenomenon while...