力学的骨格に着目した連続トラス橋梁の危機耐性構造計画手法の提案

Abstract

構造物の建設時，計画段階で危機耐性を考慮すべきとされているが，危機耐性を組み込んだ構造計画手法は確立されていない．本研究では，連続トラス橋梁を例に危機耐性構造計画手法の提案を行う．提案手法では，まず構造における最重要要素をロバストネスインデックスにより特定する．次に，その最重要要素が欠落した構造に対して，耐荷メカニズムへの影響が大きい部材の集合である「力学的骨格」を図式力学により選定する．そして，力学的骨格の構成部材に発生する応力と許容応力度とを比較し，許容応力度を超過する部材があれば，力学的骨格の全構成部材の応力が許容応力度の範囲内に収まるよう対策する．この手法により，設計基準外事象下における連続トラス橋梁の耐荷性能が明示化され，危機耐性構造計画が実施可能となる．

When constructing civil structures, it is said that anti-catastrophe performance should be taken into account at the stage of structural planning. However, a structural planning for anti-catastrophe performance has not been established. Therefore, in this paper, we propose an anti-catastrophe performance structural planning for a continuous truss bridge. In the proposed method, firstly, we identify the most important elements of the bridge structure by the robustness index. Secondly, the mechanical skeleton, which is a set of components that have a large impact on the load-bearing mechanism, is selected for the structure lacking the identified most important elements by using graphic statics. Thirdly, the load-bearing capacity of the structure is then verified by comparing the stresses in the components of the key structure with the allowable stresses. If any member exceeds the allowable stress, we take measures in order to keep the stresses of all the members of the key structure within the allowable stress. This method clarifies the load carrying capacity of a continuous truss bridge under non-standard design situations and enables the structural planning for anti-catastrophe performance.