Collapse Modalities of Composite Girders Prestressed by External Tendons

Abstract

This chapter analyzes the nonlinear behavior of composite concrete–steel beams prestressed by external tendons that are free to slip along their path defined by a finite number of saddle points with zero friction to examine the failure modalities for the most common static schemes and for the most common constructive sequences. The formulation presented is based on a Kirchhoff model for the beam. The compatibility condition between beam and slipping external tendons is developed in the range of the infinitesimal deformation theory for generic tendon paths. The balance condition is obtained by means of the virtual work principle for materials with nonlinear constitutive laws and the formulation is sufficiently general to permit the analysis of different construction sequences. The solution is performed by means of the Ritz method and the numerical problem is solved by using the Newton–Raphson procedure. The numerical applications developed by the authors show some effects of the most important design parameters, such as section geometry and prestressing force, deformations, ultimate load capacities, cable force increments, and collapse modalities.