Numerical methodology for analyses of tubular KK multiplanar steel joints

Abstract Herein is presented a numerical methodology for a static resistance analysis of symmetrically loaded multiplanar KK joints in circular hollow steel sections. This methodology addresses factors related to the simulation of KK joints such as the material properties, the boundary conditions, mesh generation and refinement, incremental load steps and failure criteria. An objective criterion is proposed to identify the two failure modes most often occurring in KK joints. Failure mode 1 is observed when two neighboring diagonal braces loaded in the same sense act as one brace penetrating the chord together. In the failure mode 2, excessive deformation is observed in the chord region between two neighboring braces, folding the chord wall. However, in some cases the failure mode is not easily identified or both failure types are present. The proposed criterion objectively identifies the failure mode. In order to compute the joint resistance, an important failure criterion often adopted in literature for uniplanar K joints is the one known as Lu's deformation. In this paper, a strategy is proposed, which is an extension of Lu's criterion for multiplanar KK joints.

摘要 本文提出了一种适用于对称荷载作用下圆形空心型钢截面（circular hollow steel sections）多平面KK节点（KK joints）静力抗力分析的数值方法。该方法覆盖了KK节点模拟所需考量的多项关键因素，涵盖材料属性、边界条件、网格生成与细化、增量荷载步以及失效准则。本文提出了一项客观准则，用于识别KK节点中最为常见的两类失效模式：当两个受荷方向一致的相邻斜腹杆协同作用，如同单根杆件穿透主管时，即触发失效模式1；而失效模式2则表现为相邻腹杆间的主管区域出现过度变形，致使主管管壁发生褶皱。但在部分情形下，失效模式难以直观判别，或两类失效模式同时出现，此时本文提出的准则可实现失效模式的客观甄别。为计算节点抗力，现有研究中常用于平面K节点的重要失效准则为吕氏变形准则（Lu's deformation）。本文提出了一种拓展策略，将该准则推广至多平面KK节点的分析场景中。