考虑真实焊缝的空间KT型圆管承载力分析

Bearing capacity analysis of space KT circular pipe considering real weld

空间KT型圆管节点是由三根支管相贯于同一根主管表面而构成的空间结构,在相贯区域通过焊接直接形成。但通常对空间KT节点受力性能分析时,所建立的有限元模型很少涉及到焊缝几何的建立,忽略了细小焊缝形体对整体结构承载性能的影响,可能使分析结果存在误差。为此,通过UG二次开发对模型相贯区域进行B样条曲面模拟渐变焊缝形体,焊剂充分溶入钢管母材,两者分别赋予材料属性,对模拟了真实焊缝几何和未考虑焊缝的空间KT节点进行极限承载力对比分析,基于空间KT节点极限承载力经验公式进行模型验证,研究细小焊缝形体对节点极限承载力的影响。结果表明:仿真结果均低于经验公式计算值,但模拟了真实焊缝几何后的模型仿真结果与经验公式结果更为吻合,偏差仅3.125%,未考虑焊缝的模型仿真结果偏小,可能会低估节点的承载力,利用该焊缝建模技术建立的空间KT节点能更逼近实际焊接结构,可准确预判出该模型的极限承载力。

The KT type circular pipe joint is a spatial structure composed of three branches intersecting at the same chord member surface, which is directly formed by welding in the intersecting area. However, the finite element model established in the analysis of the mechanical performance of KT-joints in space rarely involves the establishment of weld geometry and neglects the influence of small weld shape on the overall structure bearing performance, which may lead to errors in the analysis results. By using UG secondary development, in the model area B-spline surface is simulated to form the gradient weld and make the flux fused fully into steel pipe parent metal. Both are independently given material properties to simulate the real weld geometry and do not consider the space of weld KT-joints for ultimate bearing capacity analysis. This paper studies the effect of small weld form on the ultimate bearing capacity based on the ultimate bearing capacity empirical formula for KT-joints model validation. Results show that the simulation results are lower than empirical formula calculated value, but after the real weld geometry simulation, the result of empirical formula is more consistent with that of the model, with the deviation of only 3.125%. Not considering the small result of the model simulation of weld slants, we may underestimate the bearing capacity of the joint. The space established based on the weld modeling KT-joints can be closer to the actual welding structure, which can accurately predict the ultimate bearing capacity of the model.