Time-dependent analysis of concrete bridges with creep, shrinkage and cable relaxation

Abstract

This paper describes a single-step method to predict the time-dependent behaviour of concrete structures due to concrete creep, concrete shrinkage and cable relaxation. Firstly, a new relaxation model for steel tendons based on the equivalent relaxation function is proposed to enable the accurate estimation of the losses of cable forces. Based on this new model, a relaxation-adjusted elasticity modulus is developed to enable the prestress loss to be analyzed using a single step. Then a general method is established for single-step finite element analysis for time-dependent deformations of concrete bridges under the effects of concrete creep, concrete shrinkage and cable relaxation, using the age-adjusted elasticity modulus, shrinkage-adjusted elasticity modulus and relaxation-adjusted elasticity modulus respectively. In this proposed method, concrete members are modelled using beam elements, while tendons are modelled as truss elements with nodes connected to the beam axis by perpendicular rigid arms. Numerical examples are analyzed using both the time integration method and the proposed single-step method. The good agreement of results demonstrates the accuracy and efficiency of the proposed method. © Civil-Comp Press, 2009.