Long-term behavior of composite girder bridges

This paper deals with the development of an analytical model to predict the long-term behavior of composite girder bridges. The proposed model accounts for the effects of creep, the shrinkage of concrete, and the cracking of concrete slabs in the negative moment regions. 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 algorithm based on the expansion of compliance function. Correlation studies between analytical and experimental results are conducted with the objective to establish the validity of the proposed model. Besides, many composite girder bridges made of more than one type of concrete or of concrete and structural steel are adopted and analyzed to investigate the effects of creep and shrinkage of concrete slabs on structural behavior.