Investigation on mechanical performance of prestressed concrete box‐girder bridge strengthened using composite trusses with different shapes

Abstract In this study, a finite element (FE) model of an existing prestressed concrete box‐girder (PCB) bridge is developed using Abaqus/Explicit (2022), and a series of FE simulations are conducted to examine the results of composite trusses (CTs) in strengthening PCB bridges with different shapes. A concrete damage plastic model of concrete is used to predict the nonlinear behavior of concrete. Field tests and theoretical calculations are performed to verify the rationality of the model. Three CTs of different shapes, that is, a K‐shaped composite truss (KCT), an X‐shaped composite truss (XCT), and a triangle‐shaped composite truss (TCT), are used to strengthen the PCB bridge models. The deflection, load distribution, distortion, and surface connection forces under two types of lane loads (European code [EU] and Chinese code [CC]) are discussed. The results show that the CT can reduce the deflection and distortion of the PCB bridge and improve the load distribution. However, the different CT shapes offer other strengthening effects. Among them, the XCT reduces deflection the most significantly, that is, by 8.9% and 17.1% under the two load modes, separately. In addition, the XCT improves the load distribution of the PCB bridge the most significantly. The KCT reduces the distortion of the PCB bridge the most significantly and decreases the stress ratio by 75.36%. Moreover, the deflection of the PCB bridge under the EC is more significant, indicating that the lane load defined by the EC is larger than that by the CC. The maximum surface connection forces are different under the same load mode for the different CTs. However, in all the models, the bending moment at surface‐2 is insignificant. Based on the analysis results, five assumptions are introduced. Using the KCT as an example, the plane model of the reinforced section is simplified, and a canonical equation is established to calculate the load distribution factor. The 324 coefficients and 18 free terms in this canonical equation are deduced, which provides a theoretical basis for strengthening PCB bridges using CTs.