In the heart of bridge engineering, a novel approach to optimizing the structural integrity of steel-concrete composite girder bridges is making waves. Researchers, led by WANG Yafeng from the School of Civil and Environmental Engineering at Changsha University of Science & Technology, have developed a method to significantly reduce the compressive stress on the steel bottom plate of these bridges, particularly in the negative bending moment zone at the pier top.
The study, published in *Zhongwai Gonglu*, which translates to *China Foreign Highway*, focuses on a common yet often overlooked issue in bridge construction: the pressure borne by steel girders. “Existing research mainly proposes improvement measures for the tension of concrete bridge decks, while paying little attention to the common phenomenon of steel girders bearing pressure,” WANG explains. This oversight can lead to structural inefficiencies and potential long-term issues.
The research team tackled this problem by proposing a solution that involves partially filling the interior of the box girder in the pier-top negative bending moment zone with cast-in-place concrete during the construction phase. This method aims to reduce the compressive stress on the steel bottom plate, which bears the highest compressive stress of the entire bridge.
To achieve this, the team first established an Ansys finite element model of the composite girder bridge for stress analysis. They then used an improved generalized regression neural network (IGRNN) for dimensional optimization, taking the length and vertical thickness of the infill concrete along the longitudinal bridge direction as variable parameters. The optimization objective was to minimize the peak compressive stress in the steel girder bottom plate.
The results were impressive. The optimized compressive stress in the steel bottom plate was reduced by 74.9% compared to the original structure. “Filling a certain amount of concrete into the box girder in the pier-top negative bending moment zone can significantly reduce the compressive stress in the steel bottom plate,” WANG notes. The predictions made by the IGRNN were also highly accurate, with the compressive stress corresponding to the predicted optimal dimensions within 5% of the value calculated by the finite element model.
This research has significant implications for the bridge engineering sector. By optimizing the dimensions of infill concrete, engineers can enhance the structural performance of steel-concrete composite girder bridges, leading to longer-lasting and more efficient structures. The use of IGRNN for dimensional optimization also offers a faster and more efficient alternative to traditional methods, potentially reducing construction time and costs.
As the demand for robust and efficient infrastructure continues to grow, innovations like this are crucial. The findings and methods from this study can provide a valuable reference for reducing the compressive stress in the steel girder bottom plate at the pier top and related issues for similar bridges. This could pave the way for more advanced and reliable bridge designs in the future, benefiting both the construction industry and the communities that rely on these vital structures.