包含节点建模的空间结构弹塑性破坏机理精细化研究

Traditionally, structure calculation model adopts beam element with hinged or rigid connection and ignores joints exiting, separate joint research has the difficulty of deciding boundary condition. In this project, shell or solid element will be chosen to simulate steel tubes and joints, and then, the refined FEM structure model including joints created. A reasonable relationship of 'refined model - multi scale model -traditional beam model' is about to be established. Elasto-plastic failure mechanism of spatial structure will be researched in detail from macroscopic to microscopic. We call this method 'research structure considering joints, research joint from structure'. Four types of widely used spatial structures, space truss, plane and triangle truss, single layer latticed dome, single layer cylindrical reticulated shell, are chosen to be study objects. nonlinear analysis considering geometrical nonlinear and material elasto -plasticity will be carried out. Refined plastic stress-strain distribution and deforming state in members, joints and welds will be investigated carefully. By tracking the develop process of plastic (or called damage) in members or joints, Elasto-plastic mechanism of strength failure or stability failure will be revealed. The influence of welding defects and manufacture defects can be determined by detailed analysis. The hysteretic and energy dissipation behavior of whole structure with joints will be studied. By the above studies, design suggestions on structure, member, joint and weld are reasonably put forward from the angle of refined failure mechanism, which will control structure collapse forms actively. Based on correct design details presented from this results, the consistency of traditional beam element model and refined model can be guaranteed, so this project will offer theory basis for spatial structure design and construction.

为克服传统一维梁单元整体计算模型不能考虑节点影响、单独节点模型难以准确截取边界条件二者的缺陷，本项目拟采用壳单元或实体单元建立包含节点的整体结构精细化模型，建立完全精细化模型-多尺度模型-传统梁单元模型的有机联系，从宏观到微观精细化地研究空间结构弹塑性破坏机理，"带节点研究结构、研究结构中的节点"。选取最常见的双层网架、平面和立体管桁架、单层球面网壳、单层柱面网壳为研究对象，考虑几何和材料双非线性，精细地观察结构构件、节点、连接各细部的应力状态和变形形式，跟踪结构各个部位塑性发展（或称损伤）过程，揭示空间结构强度或稳定破坏的弹塑性受力机理，探明焊接和施工缺陷等因素的影响程度，考察结构的滞回性能和动力特性。从精细化非线性分析的角度，提出结构整体、杆件、节点、连接的设计建议，主动控制结构的破坏形态，归纳正确的设计构造措施，使传统梁单元模型和精细化分析具有一致性，为设计和施工提供理论依据。

为克服传统一维梁单元整体计算模型不能考虑节点影响、单独节点模型难以准确截取边界条件二者的缺陷，本项目采用壳单元或实体单元建立包含节点的整体结构精细化模型，建立完全精细化模型-多尺度模型-传统梁单元模型的有机联系，从宏观到微观精细化地对空间结构弹塑性破坏机理进行了研究，"带节点研究结构、研究结构中的节点"。选取最常见的双层网架、平面和立体管桁架、单层球面网壳、单层柱面网壳为研究对象，考虑几何和材料双非线性，精细地观察结构构件、节点、连接各细部的应力状态和变形形式，跟踪结构各个部位塑性发展（或称损伤）过程，揭示空间结构强度或稳定破坏的弹塑性受力机理，探明焊接和施工缺陷等因素的影响程度，考察结构的滞回性能和动力特性。从精细化非线性分析的角度，提出结构整体、杆件、节点、连接的设计建议，主动控制结构的破坏形态，归纳了正确的设计构造措施，使传统梁单元模型和精细化分析具有一致性，为设计和施工提供了理论依据。本课题成果主要分为三个方面：第一方面主要研究对象为平面管桁架、立体管桁架精细化极限荷载分析和破坏机理研究；第二方面主要研究内容为螺栓球节点精细化研究、网架结构极限承载力精细化分析和破坏机理、单层球面网壳结构精细化分析和破坏机理、以及焊接空心球节点参数分析；第三方面主要是考虑焊接影响的空间结构承载力精细化有限元分析、焊接球节点单层球面网壳动力极限承载力的精细化分析、和考虑杆件失稳的单层网壳稳定性精细化分析和试验研究。