Nonlinear Finite Element Analysis And Parametric Evaluation Of Prestressed Concrete Beams

Prestressed concrete beam has been widely used in the civil engineering and is one of the most fundamental members in the frame structures. It is a very practical job to develop a reasonable numerical analysis model for prestressed concrete beams, which is used to simulate the flexural behavior, judge the failure pattern, evaluate the working performance and optimize the structural design of the beams. With the nonlinear stress-strain relationships for concrete, prestressing steel and nonprestressed steel, the section tangent stiff matrix is derived by the fiber integration method by which the computational efficiency is greatly improved due to less segments divided as compared with the conventional strip method. On the basis of these, the nonlinear plane beam element theory is utilized to derive the element tangent stiffness matrix that can be divided into three submatrices reflecting three different nonlinear effects: material nonlinearity, coupling of material and geometrical nonlinearities, and secondary moment due to axial force, respectively. The incremental-iterative method is used to solve the nonlinear equations. The proposed model is capable of predicting the nonlinear full-range response of prestressed concrete beams from initial prestressing up to failure loads. The model accounts for both material and geometrical nonlinearities, and the tension stiffening effects. The model is verified by comparing the analytical predictions with the experimental results. Some important parameters are analytically investigated by the proposed analysis, including the ratios of nonprestressed and prestressing steel, span-to-depth ratio, effective prestress, yield strength of nonprestressed steel and load type, to evaluate their influence on the flexural strength and structural behavior of prestressed concrete beams. The analytical results provide a reference for the optimal design of prestressed concrete structures.