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

本研究项目的主要目的是开发造价较低、耐久性较高的新型斜拉桥体系，国外多采用斜拉式2-I组合梁桥，因为其造价较低。然而，它们的耐用性还没有得到检验。本研究首先利用斜拉桥主构件应力计算的简化方法，从静力的角度探讨了跨度达500米的斜拉桥主梁体系的可行性，并对其可行性进行了分析。为了检验该体系的耐久性，建立了考虑拉索局部振动的三维动力有限元分析模型。在车辆荷载作用下，与常规系统相比，该系统没有表现出特殊的动力行为。在此基础上，提出了设置粘滞阻尼器的有效性及其设计方法。其次，研究了一座2-I组合梁的结构性能。对斜拉桥组合梁进行了有限元分析，得到了组合梁的应力，提出了混凝土板剪力滞效应的计算方法。文中还进行了徐变和收缩分析，并提出了徐变和收缩现象的重要性。通过有限元分析，研究了横向加劲体系对2-I梁桥三维结构特性的影响。通过计算，得出了简支横向加劲体系的可能性。

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.