塑性域の拡がりを考慮したASI-Gauss法の開発と木材はりの弾塑性解析への適用
Abstract
わが国では近年，既存木造建築に対する強度評価や設計時の詳細な挙動予測の需要が高まっており，木造建築の弾塑性挙動を高精度で解析可能な手法が求められている．筆者らにより開発された ASI-Gauss法は，建築物などの骨組構造の弾塑性解析を高精度かつ低計算コストで実施可能とするが，本手法による弾塑性解析ではこれまで塑性ヒンジ法が用いられており，部材の降伏判定と同時に要素の剛性を急激に低下させていた．一方，木材は主に圧縮側でのみ塑性化し靭性を示すという特徴を有するため，曲げ変形時の剛性低下は比較的緩やかに進行する．したがって，ASI-Gauss 法を木造建築の弾塑性解析に適用するにあたり，部材中の塑性域の拡がりの考慮が重要と考えられる．そこで本研究では， 塑性域の拡がりを考慮した要素剛性更新アルゴリズムを開発し，ASI-Gauss法に導入した．そしてソリッド要素による有限要素解析との比較を行い，妥当性や有用性を検証した．
Recent significant damages on timber structures during disasters and advancements in their design process have called for accurate evaluation methods for the elasto-plastic behavior of timber structures. Among them, the ASI-Gauss technique is thought to be promising because of its computational efficiency and accuracy. However, the method has relied on a plastic hinge model, which does not consider the expansion of a plastic region and cannot precisely predict the elasto-plastic behavior of a timber beam under a bending load. Therefore, this study presents a novel ASI-Gauss technique with an algorithm that can address the issue. The algorithm identifies stress and strain distributions in a section of an element from the sectional forces, updating the element stiffness as the plastic region expands. This study also conducts a comparison between the proposed method, the conventional ASI-Gauss technique, and the finite element method (FEM) using solid elements, and it is determined that the proposed method successfully captures the gradual decrease in an element stiffness with an accuracy close to that of the FEM using solid elements.