Coupled Effects of Concrete Shrinkage, Creep, and Cracking on the Performance of Postconnected Prestressed Steel-Concrete Composite Girders

Prestressed steel-concrete composite girders constructed by postconnection have gained increasing attention in bridge engineering in recent years. By prestressing the concrete slabs before connecting them with the steel girders in the hogging regions subject to negative moments, this new construction method for steel-concrete composite girders is capable of mitigating the risk of concrete cracking in continuous girders to improve the safety and serviceability of bridges. To study the complex stress and strain distributions in the prestressed composite section as well as their nonlinear evolution with time, a three-dimensional (3D) viscoelastoplastic damage constitutive model is presented in this investigation. In this model, the instantaneous responses of concrete are described by an elastoplastic damage model, and the time-dependent concrete creep and shrinkage are approximated based on an improved rate-type formulation. Compared with the one-dimensional (1D) elastic analysis widely used in current practice, the proposed model provides detailed and realistic information of the stress and strain distributions within the entire composite section during construction and in service. In a case study of a real continuous girder, the coupled effects of concrete shrinkage, creep, and cracking on the long-term behavior of the composite section are estimated based on the proposed model. Furthermore, a parametric study on the curing duration shows that this new construction method can be further improved by controlling the concrete shrinkage.