Optimum Combination of Bridge and Deck Systems for Superspan Cable-Stayed Bridges

The huge axial force in the main girder challenges the design of superspan cable-stayed bridges. To reduce the self-weight of the girder, the conventional orthotropic steel deck (OSD) system is widely adopted due to its high strength-to-weight ratio, which may generate fatigue problems. In this paper, the optimum combination of different bridge and deck systems was studied by designing a cable-stayed bridge with main span of 1,480 m. Two different bridge systems were investigated: the conventional cable-stayed bridge system and a partial ground-anchored cable-stayed bridge system with crossing stay cables (the new bridge system). Additionally, in each bridge system, three different deck systems were studied: the OSD system, a composite deck system composed of the OSD system and an ultrahigh-performance concrete (UHPC) layer, and an UHPC waffle deck panel system. Finite-element (FE) models of the six plans were developed and analyzed. The static, dynamic, and economic performances of the six plans were compared. Model tests of the composite and UHPC waffle panel systems were performed to ensure the feasibility of the design. Compared to the conventional bridge system, the new bridge system has a much smaller axial force in the main girder, greater longitudinal stiffness, and economic advantages. Under the traffic load, a much lower stress amplitude is developed in the girder with the UHPC waffle deck panel system than in girders with the other two deck systems. Compared to the OSD system, the composite and UHPC waffle panel systems are advantageous in terms of lifecycle cost. Therefore, the combination of the new bridge system and the UHPC waffle deck panel system is recommended as the optimal design plan.