Development of new cable-stayd systems with economy and high durability

本研究项目的主要目的是开发具有较低施工成本和较高耐久性的新型斜拉桥体系。在国外，斜拉2-I组合梁桥因其造价较低而被广泛采用。然而，它们的耐久性尚未得到检验。这是目前为止日本没有采用这种经济制度的主要原因。本文首先利用简化法求出斜拉桥主构件的应力结果，从静力学的角度探讨了跨度达500米的斜拉桥体系存在的可能性，并给出了其存在的可能性。为了检验系统的耐久性，开发了包含索局部振动的三维动力有限元分析。在车辆荷载作用下，已知该系统与常规系统相比没有表现出特殊的动态行为。此外，还介绍了安装粘滞阻尼装置的有效性及其设计方法，以应对缆索的非预期振动。其次，对2-I型组合梁的结构性能进行了研究。采用有限元法对斜拉桥组合梁的受力进行了分析，提出了混凝土板剪力滞的计算方法。本文还进行了蠕变和收缩分析，并指出了研究蠕变和收缩现象的重要性。通过有限元分析，研究了横向加筋体系对2-I梁桥三维结构特性的影响。通过计算，得到了简单横向加筋系统的可能性。

The main aim of this research project is to develop new cable-stayd bridge systems with lower construction cost and higher durability.In foreign countries, cable-stayd 2-I composite girder bridges are used becase of their lower construction cost. However, their durability has not been examined. This is the main reason why this economical system has not been used in Japan so far.In this study, first, utilizing the simplified method for obtaining the stress resultants of main members in cable-stayd bridges, the possibility of such system with a span up to 500 meteres is investigated from statical viewpoints, then the possibilities of them are presented. To examine the durability of the system, a 3D dynamic FEM analysisis developed which includes cable local vibration. Under vehicle loading, it is known that this system does not show peculiar behavior compared with dynamic behavior seen inconventional systems. Further, to cope with unexpected cable vibration, the effectivenessof the installation of viscous damping device and its design methos are presented.Secondly, the structural behavior of a 2-I composite girder is studied. A FEM analysis is developed to obtain the stress in the composite girder in cable-stayd bridge, then the method to obtain the shear-lag in concrete slab is proposed. Creep and shrinkage analysis is also carried out and the impotrance of their phenomena is suggested. From FEM analysis, the effect of transvese-stiffening system on the 3-D structural characteris-tics of the 2-I girder bridge is investigated. From the calculation, the possibility of the simple transverse-stiffening system is obtained.