Nonlinear dynamic analysis of fiber reinforced ultra-long span cable stayed bridges

摘要

The central span which is the most critical part of a cable-stayed bridge has almost reached the technical limit for traditional materials, construction technology and bridge system capability. The idea of Ultra-long Span Cable Stayed Bridge (USCSB) is proposed in this paper by introducing a hybrid type cable stayed bridge as a competent system. The new system leads to huge reduction in deck weight and critical stresses in the pylon zones by using a hybrid advanced composite deck. A multi-scale modeling technique is adapted which represent material design at the micro/macro-level, and accurate homogenization of the advanced composite components properties and evaluation of the resulting anisotropic characteristics. Besides, the dynamic performance under wind and seismic excitations, and the potential deficiency of such a bridge system is investigated via state-of-the-art computer simulations and large-scale dual shaking table experiments. The investigation result demonstrated that adopting a fiber reinforced polymer deck system can efficiently reduce internal deck stresses due to the high strength of FRP materials and the tubular type of lay-up structural system, increase its load carrying capacity of cable stayed bridges and hence, having a great potential extent the span length of stay cable supported bridge system. At the same time, due to the relatively low Young's modulus and shear modulus of fibrous materials, deflection at full loading and torsional resistance should be carefully controlled by using a convex initial configuration with sufficient internal bracing. Moreover, investigation result also suggested that wind induced coupling excitation is likely to occur in such a light-weighted system with low shear and torsional stiffness.