Nonlinear behavior of externally prestressed composite beams: Analytical model

The analysis and design of composite beams prestressed by external tendons involves difficulties mainly related to the cable slip at the saddle points and to the construction sequences. The paper presents a model for analyzing such structural systems under general conditions. Generic nonlinear constitutive laws are considered. No restrictions are assumed for tendon profiles and static scheme. Usual construction sequences can be considered. Kinematics and the compatibility equations refer to a beam model preserving the cross section planarity, and the tendon is free to slip at the saddle points. The characteristics of the problem make it convenient to obtain the balance condition from the virtual work principle. The numerical solution was performed by variational approximating methods and the nonlinear equations were solved by the Newton-Raphson procedure. The paper presents a tool for the analysis of externally prestressed composite beams up to failure in order to investigate the influence of typical design parameters on the ultimate capacity. The effectiveness of the presented model is shown in a numerical example.