A STUDY FOR WAVE RESPONSE OF HORIZONTAL-ARCH BRIDGES WITH SEMI-SUBMERSIBLE FLOATING FOUNDATIONS

本文研究的是“半潜式浮基水平拱桥”，将浮桥基础改为半潜式浮基。本文重点研究了浮基的波浪响应特性，分析了基础形状对抗浪设计的影响，并利用轴对称有限元程序对每个浮基进行了绕射和辐射波浪力计算。该程序采用无限单元来满足无穷远处的辐射条件。将桥梁结构建模为弹性梁，利用通用有限元程序NASTRAN对整个结构体系进行了有限元分析。利用该程序成功地对流弹结构体系进行了分析，在基础沉没位移恒定的情况下，考察了浮动基础的作用效果。算例表明，半潜式浮桥具有较好的动力特性。此外，以大阪市政府正在筹建的前岛-鱼岛航道浮桥为研究对象，在考虑护栏非线性和桥梁系统弹性变形的情况下，对浮桥进行了时程响应分析。

This research has studied "Horizontal-arch bridges with semi-submersible floating foundations, " which the floating pontoon foundations are replaced by the semi-submersible floating foundations. In this study, the attention has been paid on the wave response characteristics, and the effect of the foundation shapes are examined to improve the wave-resistant design.The diffraction and radiation wave forces have been calculated by using axi-symmetric Finite Element Program for each floating foundation. The program enploys infinite elements for satisfying radiation condition at infinity. The bridge structure is modeled as a elastic beam, and the whole structural system has been analyzed by NASTRAN,general purpose F.E.M.program. The fluid-elastic structure system has successfully been analyzed by the procedure.The effect of the floating foundations have been examined on the condition that the immersed displacement of the foundation has the constant value. Numerical examples have shown that the semi-submersible type floating bridge has an improved characteristics. Moreover, the floating bridge that the Osaka municipal office is now planning at Maishima-Yumeshima channel is studied, and the transient response analysis in the time-domain considering nonlinearity of the fender and the elastic deformation of the bridge system has also been made.