Spatial Stress of the Pier–Girder Rigid Region of a Continuous Rigid-Frame Bridge with V-Shaped Piers in Two Directions

The pier–girder rigid region of continuous rigid-frame bridges with V-shaped piers has a complex spatial stress state because of its special structure and complex boundary condition. However, using the beam–column element model for mechanical analysis in design induces large errors. Therefore, this study analyzes the spatial stress and structural optimization of the pier–girder rigid region of a continuous rigid-frame bridge with V-shaped piers. A solid model of the pier–girder rigid region is established by photoelastic stress experiment and numerical analysis. The stress distribution characteristics of the pier–girder rigid region in the longest cantilevered stage and operational stage are revealed in view of tri-directional normal stress and boundary tangential normal stress, and the stress distribution curve of slice boundary at key positions is drawn. Results show that (1) the experimental values are consistent with the finite-element analysis values, and the compressive stress is dominant in the main girder structure, which meets the design requirements of fully prestressed concrete structures; (2) the tensile stress concentration appears around the hole of the diaphragm in the bridge transverse direction, whereas the compressive stress concentration appears at the joints between the top and bottom plates of the box girder and the diaphragm in the bridge longitudinal direction; (3) the consolidation zone between the V-shaped bracing and the vertical pier is the most dangerous area of the structure, where the structural measurements of increasing the reinforcement or using steel fiber–reinforced concrete are proposed. An optimization measure for increasing the height of the vertical pier is introduced to present the property of a flexible pier and optimize the mechanical characteristics of the bridge. As the height of the pier increases, the stress gradient of each section of the V-shaped bracing decreases, and the distribution of cross-section stress becomes uniform. When the height of the pier is greater than five times of the girder height at the pier top, the stress gradient of each section of the V-shaped pier is less than 0.6. Herein, the force is reasonable with large safety reserve, which can adapt to the longitudinal displacement of the main girder caused by concrete shrinkage, creep, and temperature change in the later stage.