| Nanjing Dashengguan Yangtse River Bridge is a steel truss girder (arch) bridge with six spans, three-truss, six railway lines on the high-speed railway from Beijing to Shanghai. The span arrangement is (108+192+336+336+192+108) m. It takes the form of multiple transversal girder system with the orthotropic steel ballast monolithic deck. The mechanical behavior of this new type bridge is very complicated. Two model tests were performed. One is truss segment model test, the other is arch segment model test. The mechanical behaviors of three-truss monolithic deck structure were systematically investigated in this paper. The main work has been done as follows:1. Two 1:6 six-segment models were designed. One is from the span (108+192) m to simulate the mechanical behaviors of truss girder span; the other is from the span 336m to simulate the the arch span.2. "Combined loading" method that deck loading combined node loading was proposed. Node loading compensates the "first system" stress to ensure that the segment model can perform as the real bridge.3. In truss segment model, both positive moment zone and negative moment zone near support of steel truss girder span were simulated using different support modes. Seven load cases were completed to simulate the mechanical behaviors of the steel truss girder span under various loads, and to study the mechanical behaviors of three-truss monolithic deck structure.4. In arch segment model, steel model test and steel-concrete model test were performed. Seven load cases were completed to simulate the mechanical behaviors of the arch span under various loads, and to study the mechanical behaviors of three-arch monolithic deck structure.5. The results of steel model test and steel-concrete model test were researched comparatively. The influence of concrete deck on mechanical behavior of the bridge was studied. The results showed that: considering the concrete ballast slab, the integral stiffness of the floor system increases, the stress of the tie beam, the stringer and the members of non-floor system decreases, and the stress of the transversal girder in the joint increases.6. The results of segment model test and FEM for real bridge were researched comparatively. The correctness of FEM was investigated .The results showed that: the stress level between the model test and the real bridge is close, the FEM result is correct, and the simulation method that segment model simulates the real bridge is correct.The production of this paper can provide the basis for the design and the construction of Nanjing Dashengguan Yangtse River Bridge and provide references for other model test. |
