基于钢管K型节点刚度的应力集中系数计算方法

采用通用软件MSC.MARC建立三维实体有限元模型，进行钢管K型节点应力集中系数参数分析。基于现有钢管K型节点试验与有限元分析结果，说明现有规范中钢管K型节点应力集中系数计算公式的不足。采用理论推导和回归分析相结合的方法提出基于节点刚度的钢管K型节点应力集中系数计算方法，并验证该计算方法的准确性和适用性。研究结果表明：有限元分析与试验得到的钢管K型节点最大位移和最大热点应力偏差分别不超过5.11%和6.83%，验证了有限元分析结果具有较好的精度；对比有限元分析结果发现，由于钢管K型节点几何参数之间存在交叉关系，即变化其中一个几何参数会造成其他几何参数的变化，使得几何参数对钢管K型节点应力集中系数存在相互耦合作用；现有钢管K型节点应力集中系数计算方法是通过单一参数回归得到，无法考虑几何参数对钢管K型节点应力集中系数的相互耦合作用，且安全度相对较低，不适用于桥梁结构中钢管K型节点应力集中系数的计算；本文中提出的基于节点刚度的钢管K型节点应力集中系数计算方法不仅能够考虑节点不同几何参数对钢管K型节点应力集中系数的相互耦合作用，而且能够提高评估和计算桥梁结构中钢管K型节点应力集中系数安全度和精度。

Stress concentration factor calculating method based on circular hollow section K-joint stiffness

A three-dimensional solid finite element model was established to carry out parametric analysis on the stress concentration factor of circular hollow section (CHS) K-joints by the general software of MSC.MARC. Based on the existing results of tests and finite element analysis of CHS K-joints, deficiency of the formula adopted by the current codes to calculate the stress concentration factor of CHS K-joints was revealed. A method for calculating the stress concentration factor based on CHS K-joint stiffness was proposed by combining the theoretical derivation and regression analysis, and the accuracy and feasibility of the calculating method was validated. It is found that the differences between the test results and the finite element analysis results in terms of the maximum displacement and maximum hot spot stress of CHS K-joints are less than 5.11% and 6.83%, respectively, demonstrating that the finite element model has high accuracy. By comparing with the results of finite element analysis, it is found that there is a coupling effect among the geometric parameters of CHS K-joins in its stress concentration factor, as the variation of one parameter generally leads to the variation of other parameters. Because the current stress concentration factor calculating method of CHS K-joints is based on regression analysis according to single geometric parameter, it ignores the coupling effect caused by geometric parameters of the joints. Therefore, it has a small safety margin and is not suitable to calculate the stress concentration factor of CHS K-joints used in bridge structures. The proposed stress concentration factor calculating method based on CHS K-joint stiffness can not only consider the coupling effect caused by the geometric parameters of the joints, but also improve the safety margin and accuracy of evaluating and calculating the stress concentration factor of CHS K-joints used in bridge structures.