Seismic-resistant Behaviors Analysis Of The L-shaped Reinforced Concrete Column Subjected To Biaxial Loading

In the fact seismic event, the responses of reinforced concrete structure always show apparent three-dimensional effect: complex coupling action can be detected in the biaxial bending subjected by R.C. frame columns. This coupling action usually is one of the main factors resulting in the failure or collapse of R.C. structure. The coupling action of biaxial bending subjected by L-shaped R.C. columns is more complex than by rectangle,十, T-shaped columns because of the characters of L-shaped section. Few quasi-static experiments of specially-shaped columns have been carried out because of the limitations in quasi-static experimented conditions, consequently few studies have been borrowed ideas from about seismic-resistant behaviors analysis of L-shaped R.C. column subjected to biaxial loading. Therefore it is necessary to carry out numerous simulations on seismic-resistant behaviors of L-shaped R.C. column subjected to biaxial loading in aspects of bearing capacity, ductility and hysteretic energy dissipation and so on, which will contribute to the estimation of seismic resistant behaviors of L-shaped R.C. columns, the establishment and perfection of national standards of specially-shaped columns structure. To reach the goal, this studies is carried out through the following steps: ①At the stage of elasticity, span ratio and crankle ratio are selected which influence the applicability of plane-section assumption and according to the error analysis of strain on the section level and displacement on the member level; In the inelasticity, the nonlinear comparison analysis between experiments and simulations by fiber beam-column element based on flexibility method of finite element, the range under the plane-section assumption in the elastic and inelastic analysis of L-shaped R.C. columns have been studied. The minimal span ratio for applicability of plane-section assumption in the elastic and inelastic analysis of L-shaped R.C. columns are presented, which contribute to the analysis of seismic-resistant behaviors of L-shaped R.C. column subjected to biaxial loading by fiber beam-column element. ②By fiber beam-column element based on flexibility method of finite element, the quasi-static test of R.C. columns under biaxial loading have been simulated, which shows the better simulated capacity of this element in inelastic analysis about biaxial coupling action of R.C. columns. ③By fiber beam-column element based on flexibility method of finite element which can calculate the coupling action between axial force and biaxial bending and degradation of stiffness at the same time, the seismic-resistant behaviors of L-shaped R.C. columns subjected to different load paths and axial compression ratio have been simulated numerically. The influence of load paths and axial compression ratio on the strength, ductility and cumulate hysteretic energy dissipation has been studied. The results show that the strong biaxial interaction exists in L-shaped R.C. columns subjected to biaxial loading, so that the ductility of L-shaped columns decrease obviously; the influence of load paths on the strength can not be taken into account in design of L-shaped R.C. columns according to the skeleton curve of the ultimate strength; but the influence of load paths on the ductility, the influence on of axial compression ratio on the strength and ductility must be taken into account; the strong relation exists between cumulate hysteretic energy dissipation and load paths.