Impact experiment of a set of steel/RC composite beams was conducted. To consider the influence of local impact residual deformation, transient response was investigated using elastic-plastic contact law. Experiments show that the main failure mode is related to the value of potential energy of impacter and energy dissipation capacity of sand cushion. Each theoretical analysis result is slightly less than its corresponding experimental value. Experimental values and elastic-plastic contact analysis results present that the maximum displacement and the maximum steel strain on the lower layer at midspan increase with the thickness of sand cushion and the height of impacter.

The mathematical algorithm of zero order optimization is a general function approach optimization method. Based on this method, many sets of analytical procedures are developed using ANSYS to study the design of 600m scale concrete arch bridge and the optimal arch axis coefficient, change mode and cross section sizes are obtained and verified. Results show: the mathematical algorithm of zero order optimization can effectively study the design of 600m arch bridge. The rich conclusions about design parameters can be a significant reference for design and further research of 600 m scale concrete arch bridge.

The steel-concrete composite beam with steel box and precast deck is a new bridge structure. However, studies on the mechanism of a steel box and precast concrete slab connected by a shear key remain scarce. To explore the mutual coupling relationship between the steel box girder and the prefabricated bridge deck slab under a shear key, an experimental model of shear connection between steel box and precast concrete slab was proposed in this work. Finite element analysis and experimental methods were used to develop a push-out test analysis model with 12 symmetrical Ushaped shear keys in three rows and two columns along the longitudinal direction of a precast slab. Using the plastic damage model, the mechanical response characteristics of the shear connection structure, including its force transmission mechanism, stress state, and strain distribution, were analyzed and the accuracy of the calculation results was verified. Results indicate that as the amount of load increases, the compressive stress of the concrete slab expands from the root of the shear key in an arched manner and eventually forms an elliptical table. The load on a single shear key is inversely proportional to its distance from the loading point. The crack load of the concrete slab is 0.47 Pu, and the yield load of the shear key is 0.7 Pu. This study offers a certain reference value for optimizing the design of bridges with a steelconcrete composite girder.

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