Fatigue Life of Composite Truss Used to Strengthen the Prestressed Concrete Box Girder Bridge: A Case Study

Abstract

The study assesses the fatigue life of a composite truss (CT) employed in strengthening the Xiuzhen River Bridge. Initially, weigh-in-motion data of the bridge undergo analysis, focusing on parameters such as traffic volume, vehicle model and position, velocity, vehicle distance, and gross vehicle weight. These parameters characterize actual vehicle flow loads, evaluated for goodness of fit using the Kolmogorov–Smirnov test. A stochastic traffic model is then generated via a combined Monte Carlo (MC) method and intelligent driver model (IDM). The MC method establishes a macroscopic traffic flow, while the IDM simulates microscopic driver behavior. Subsequently, a finite element model for the Xiuzhen River Bridge is established, and experiments and simulations are conducted. Results from field load and modal experiments validate the finite element analysis, confirming the reasonable margin of error and thereby ensuring the precise prediction of the fatigue behavior of the bridge. Subsequently, a stochastic traffic model is implemented on the bridge through an ABAQUS subroutine. The stress-time curves of the crucial nodes and components of the CT are obtained and converted to fatigue stress spectra using the rain-flow counting method. Finally, the Miner fatigue damage cumulative rule and min-unzipping method assess the life of the CT, unveiling a computed fatigue life of 92.39 years. The results of this study indicate that the fatigue life of the composite truss used to strengthen prestressed box girder bridges is approximately 92.39 years. Therefore, it is necessary to repair the composite truss before reaching this service life. In addition, the study introduces a numerical analysis method for evaluating the fatigue life of bridge subcomponents based on weigh-in-motion systems. This method involves analyzing the distribution of traffic loads on the bridge deck, combined with the Monte Carlo method and intelligent drive model, to generate random traffic flows using MATLAB. Subsequently, these random traffic flows are applied to a validated finite element model, and the fatigue life of subcomponents is determined using the Miner fatigue damage accumulation rule and the min-unzipping method. This approach provides engineers with a reliable reference for assessing the fatigue life of bridge subcomponents.