Experimental and Simulation Studies on Strengthening the Sanli Bridge in China with Steel Diaphragms: A Case Study

Abstract This study proposes a method to address the issue of inadequate transverse connection in the Sanli Bridge by adding steel diaphragms. A detailed construction process for this strengthening method is provided. The proposed method was verified through field load and modal experiments, confirming its effectiveness. Additionally, parameter studies were conducted using finite-element analysis. Research findings showed that the addition of steel diaphragms improved the load distribution, thereby reducing strain and deflection in the Sanli Bridge, especially under eccentric loading conditions. Modal test results demonstrated an improvement in the damping parameters of the Sanli Bridge after the strengthening, which effectively reduced the risk of resonance. Parameter analysis indicated that increasing the quantity and width of the steel diaphragms enhanced the transverse connection strength. However, it may also increase the weight and deflection of the bridge. Therefore, the appropriate quantity and width should be determined for the Sanli Bridge (in this case, the quantity was three, and the width was 2 cm). Furthermore, minor initial damage had minimal impact on the strengthening effect. However, the influence of significant initial damage exceeding 10% on the effectiveness of the strengthening measures should be considered.