Complete Analysis Of Slender Steel-Concrete Composite Columns By Numerical Simulation

Steel-concrete composite structures have advantages compared with steel structures and reinforced concrete structures in many aspects,such as higher load capacity,better fire and earthquake resisting behavior and more convenience for construction. The steel-concrete composite column is one of the main load-carrying members in the steel-concrete structure. In general cases,such a column is subject to biaxially eccentric loading with its cross sections in various kinds of shape. In this paper,complete load-deformation behavior from initial loading to final failure of slender steel-concrete composite columns with arbitrary cross sections applied to biaxial loading is studied.The deformation process of the composite column from initial loading to final failure is complex and nonlinear. In the previous studies this complete process was often determined by experimental method. The objective of this paper is to predict this complete process using numerical simulation techniques. In this paper,slender columns with the two ends hinged are considered. An iterative computer analysis procedure taking into account the second-order effect of the axial load is proposed to predict this complete load-deformation process. In the procedure,the column is first divided into a finite number of small segments in equal length. The deflection-curvature relation of each segment is determined using the finite-difference method. The final nonlinear algebraic equations are then obtained by means of the equilibrium condition for each segment. The curvature increment method is used for the solution of the nonlinear algebraic equations. For each curvature incremental step,a deformed curve in the corresponding state can be determined for the column. Through the iteration for all incremental steps until the solution is convergent,the complete load-deformation relation can then be obtained. During the above iteration,the stress resultants of the concrete in the cross section are evaluated by integrating the concrete stress-strain curve over the compression zone,while those of the structural steel and the steel reinforcement (if any) are obtained using the fiber element method.In order to implement the proposed numerical procedure,a two-module computer program is developed with the computational module in Visual Fortran code and the input-output module in Visual Basic code. Using the program the initial data can be interactively entered and the results can be graphically obtained.As numerical examples,a slender composite column of rectangular cross section with embedded H-shape structural steel is first considered. The complete load-deflection curve is obtained and compared with the corresponding experimental results. The comparison demonstrates the validity and accuracy of the proposed method. The complete deformation process of a T-shaped column is then analyzed. The load-carrying and deformation behaviors and the main factors affecting thesebehaviors of such a column are studied in detail.