Load Carrying Capacity Assessment of Prestressed Concrete Beam Bridge from Structural Forced Vibration Response

The aging of thousands of prestressed concrete (PC) bridges in Chinese highway system calls for fast condition evaluation methods to assess the load carrying capacity of this type of bridges. This paper proposes such a procedure for the PC simply supported beam bridges eccentrically prestressed with straight tendons using structural forced vibration response. The forward mapping from structural prestress force to forced vibration responses is analytically derived firstly in time domain. Special focus is put on derivation of the geometrical stiffness matrix for an eccentrically prestressed PC beam. The inverse mapping technique to identify the prestress force from structural forced vibration response is then presented by solving a sensitivity based optimization problem. According to the identified prestress force, the crack resistant load carrying capacity of the PC bridges can be assessed. A numerical study on a typical PC highway bridge, the Qinglong-River Bridge on Beijing-Qinghuangdao Highway, is conducted. Structure forced vibration responses under impulse, harmonic and white noise random excitations are simulated for the load carrying capacity assessment purpose. The results verified the effectiveness and accuracy of the proposed method.