基于数值子结构方法的结构弹塑性分析

结合震害调研及数值分析可知,结构最终失效可能仅由部分关键构件破坏引起,大部分构件仍处于弹性或小变形状态。因此为提高计算效率,在结构全过程分析中一致采用非线性单元建模并非必要,同时为准确考虑关键构件的非线性响应,本文提出一种新的数值子结构建模策略。进入弹塑性状态后,针对一般钢构件或钢筋混凝土构件采用动态替换子结构方法在单元或截面层次将其替换成非线性单元或非线性截面,并基于OpenSees平台开发了两类新单元予以实现;针对可能发生严重损伤的关键构件,采用隔离子结构方法将其隔离并建立精细化分析模型,考虑主、子结构间不同尺度边界耦合,并推导了切线刚度的传递关系,采用Client/Server技术在OpenSees平台开发了一类新的接口单元予以实现主、子结构之间的信息传递。为验证新开发单元的合理性,分别以钢及钢筋混凝土平面框架结构为例,采用纤维单元、动态替换子结构方法以及隔离子结构方法建模进行静、动力分析。计算结果表明,采用本文提出的动态替换子结构方法与常规建模方法的计算结果完全吻合并且可大幅缩短计算耗时,随着荷载水平的增大,结构中受到动态替换的构件比例急剧增大,计算效率提高程度略有降低,但仍远高于常规模型;采用本文提出的接口单元可准确传递主、子结构间的界面信息,为隔离数值子结构方法在结构弹塑性分析中的应用提供了基础。

Numerical substructure method for structural nonlinear analysis

According to seismic damage analysis of structures,the whole structure might fail due to the serious damages of some key structural members.In spite of this,it was observed that most structural members might keep elastic and experience small deformation during the process.Thus it is unnecessary to use nonlinear models for the whole structures during the entire process of seismic analysis.A novel modeling methodology,named numerical substructure method,was presented considering the demands of computational efficiency and accuracy,including dynamic replacement substructure method and isolation substructure method.In the first method,once the elastic structural members (e.g.steel members and reinforced concrete members) yielded,they were replaced in the element and section levels by nonlinear models.In the isolation substructure method,the key members were isolated from the master structure,and refined FE models for the members were built in other platforms.The data transfer (e.g.displacement,force and tangent stiffness) between master structure and substructure was achieved by using CS technique.The above numerical substructure methods were implemented into a general finite element framework,OpenSees.To verify the newly developed numerical substructure method,two steel frames and a RC frame subjected to both static and dynamic loading conditions were taken as application examples.The analysis results using dynamic replacement elements model agree well with that using normal fiber elements model,while the computational time greatly reduced,although this advantages become less remarkable with increasing number of members yielded and replaced; the data transfer between master structure and substructures are efficient and accurate,enabling isolation substructure method to be potentially used in large scale structural elastic-plastic analysis.