Numerical Prediction of Long-Term Deformation for Prestressed Concrete Bridges under Random Heavy Traffic Loads

Many prestressed concrete bridges exhibit increasing long-term deflections under heavy traffic loads. Cyclic creep from increasing heavy traffic has received gradually increasing attention in recent years, but the creep strain is usually treated as an empirical and nonrandom expression. In this paper, a multifactor coupled creep model for concrete is established, in which the material degradation and irrecoverable deformation under cyclic loads are redefined. Based on weigh-in-motion (WIM) and video data, a random vehicle model is presented and stress amplitudes from vehicle loads are obtained, through which fatigue damage and creep strain at every Gaussian integration point are calculated. Based on the concrete creep and random vehicle model, a three-dimensional (3D) probabilistic finite-element (FE) analysis is conducted on a prestressed continuous girder bridge subjected to heavy trucks and verified by 10-year measured data. Results show that the influence of concrete static creep and prestress loss is significant. Fatigue creep from heavy trucks plays a significant role, leading to continuous deflection and cracking of box girders. The range of deflection from random heavy trucks is about 18 mm after 10 years. The sources of different types of cracks are also distinguished. This study reveals the reasons for excessive deflection of bridges under heavy trucks via a new concrete creep model and accurate modeling of the random traffic loads.