Long-term behavior of composite bridges considering construction sequence

Abstract

An analytical model to simulate the behaviors of composite girder bridges considering the construction sequence and the time-dependent effects of concrete is presented in this study. The effects of time-dependent deformation of concrete(creep and shrinkage), relaxation and losses of prestressing steel, the partial interaction, the slab deck casting sequence, and the continuity of spans are taken into consideration, and the related numerical implementations are described. Based on the equilibrium of forces and compatibility of strains with time, the prediction of stresses and strains in the constitutive materials at any time is achieved. To consider the different material properties across the sectional depth, the layer approach in which a section is divided into imaginary concrete and steel layers is adopted. The element stiffness matrix is constructed according to the assumed displacement field formulation, and the creep and shrinkage effects of concrete are considered in accordance with the first-order recursive algorithm based on the expansion of compliance function. A linear partial interaction theory is adopted in formulation of the partial interaction behavior, and a linear load-slip relation is assumed for the computational convenience. Correlation studies between analytical and experimental results are conducted with the objective of establishing the validity of the proposed model. The two representative types of the bridge are analyzed for the structural behaviors. One type is the casting-in-situ concrete deck and steel girder bridge, and the other is the casting-in-situ concrete deck and precast prestressed concrete girder bridge. Finally, based on the results, the crack control of the deck concrete that is important in concrete structures is described with applying ACI shrinkage model.