Final Behavior of Structures Suffered by Big Earthquake.

社会对大跨度结构的需求正在增加，例如附着在高层建筑或棒球场屋顶上的中庭。这种结构包括使用钢筋混凝土和充气膜结构的壳结构，但钢桁架是最常见的。在日本这样一个地震活跃的国家，保证钢桁架结构和一般建筑的抗震安全是非常重要的。在一般建筑物的抗震设计中，为了吸收大的地震输入能量，对某些构件允许塑性变形。然而，在钢桁架结构中，由于受压构件的脆性屈曲行为，允许构件塑性变形进行抗震设计是相当困难的。如果钢桁架结构能承受稳定塑性变形，则可以采用更合理的抗震设计方法。本文主要完成了以下几个方面的研究；对双层圆柱桁架结构进行了弹塑性响应分析，并对大跨度桁架结构的破坏行为进行了研究。该分析方法考虑了构件轴向力与轴向变形之间的屈曲关系。为了防止桁架结构的倒塌，对3种6格网静定平面桁架结构进行了试验；普通桁架结构、上弦中央安装1个无屈曲构件的桁架结构和上弦全部安装5个无屈曲构件的桁架结构。非屈曲构件是插入内管的鸭管构件。结果表明，该桁架结构可获得稳定的塑性变形。对非屈曲构件双层圆柱桁架结构进行了弹塑性响应分析，结果表明，在大地震作用下，双层圆柱桁架结构可以考虑塑性变形。

The social needs for large span structures, such as atria attached to tall building or baseball stadium roofs, are increasing. Such structures include shell structures using reinforced concrete and air-inflated membrane structures, but steel trusses are the most common. In japan, a seismically active land, it is very important to ensure safety against earthquakes for steel truss structures as well as for general buildings.In the seismic design of general buildings, plastic deformations are permitted for some structural members in order to absorb the large earthquake input energy. However, in steel truss structures, it is quite difficult to perform seismic design by allowing plastic deformation of members because of the brittle buckling behavior of compressive members. If stable plastic deformation could be allowed for steel truss structures, a more rational seismic design method could be used.In this paper, the following studies area accomplished;1.Elasto-plastic response analysis is carried out for double-layer cylindrical truss structures and the collapse behavior of the large-span truss structure is investigated. The analysis method takes into account buckling in the relationship between the member's axial force and axial deformation.2. To prevent truss structure from the collapse, experiments are performed on three types of 6 grids statically determinate plane truss structures;normal truss structure, truss structure with one non-buckling member installed in the central upper chord and truss structure with five non-buckling members installed in all upper chords. Non-buckling member is duckling pipe member inserted an inner pipe. As a result, the stable plastic deformation can be obtained for the truss structure.3. Elasto-plastic response analysis is carried out for double-layer cylindrical truss structures with non-buckling members and it is shown that plastic deformation can be allowed for large earthquake.