Abstract:To enhance the traffic capacity and structural safety of existing cast-in-place box girder bridges on urban ring expressways, the key technologies for transverse widening design are systematically studied. The applicability of schemes such as single-side widening, cantilevered widening and composite beam widening is compared and analyzed. Combined with the mechanical characteristics and applicable scenes of rigid connection, hinge connection, semi-rigid connection and other splicing methods, the material performance tests are analyzed, and the low-shrinkage fiber-reinforced concrete is optimized as the wet joint material. Based on the grillage theory and transverse frame analysis method, the finite element numerical simulation is utilized to reveal the collaborative force mechanism of the old and the new structures, and to verify the effectiveness of adjusting the hinge point position in optimizing the force on the cantilever. Taking a ring expressway ramp bridge in Shanghai as an example, the hinge connection scheme combined with the anti-overturning construction measures is adopted to solve the problems of changing the force state of the old bridge and ensuring the traffic flow during the widening process. The research result shows that the reasonable layout of hinge connection points can reduce the tensile stress at the cantilever bottoms of the old bridge by 20%~30%. The low-shrinkage concrete wet joint can effectively control the crack width below 0.2 mm. The research results provide a design method that takes into account both structural safety and construction feasibility for urban elevated road widening projects.
