X形方圆汇交钢管节点的焊缝轴拉性能试验研究与承载力计算

Experimental research and strength prediction of axial tensile behavior of welds for X-joints with CHS braces to SHS chord

为了研究X形方圆交汇钢管节点(主管为方形截面钢管、支管为圆形截面钢管)的焊缝轴拉承载力,对5个非刚性连接和3个刚性连接试件进行静力加载试验。采用硅橡胶印模技术对焊缝几何特性进行精细化测量,考察焊缝全周的应变分布、破坏模式和承载力。试验结果表明:刚性连接试件在轴拉荷载作用下的焊缝全周应变分布均匀,而非刚性连接试件的焊缝全周应变分布则呈现明显的不均匀性;非刚性连接的焊缝承载力相对于刚性连接的焊缝承载力有较大程度的降低,主要原因是焊缝应力的不均匀分布以及热影响区材料的脆性破坏无法与非刚性连接主管管壁的塑性变形协调,从而先于熔敷金属发生断裂。采用有限元分析方法对焊缝的受力性能进行分析,得到不同节点参数下的焊缝有效长度,通过试验和有限元参数分析,提出了基于焊缝有效长度,且满足规范可靠度要求的非刚性连接焊缝轴拉承载力计算式。

Experimental research was done to study the strength of welds for tubular X-joints with CHS braces to SHS chord. Five non-rigid and three rigid welded connections were tested under monotonic loading. The weld properties were specially measured by use of negative mold and the strain distribution around the weld,the failure modes and the strength of welds were studied. The test results indicate the uneven strain distribution in non-rigid connections,in contrast to the even strain distribution in rigid connections. The strength of welds for non-rigid connections shows a significant reduction compared with rigid connections. It could be explained by the uneven stress distribution of welds and the brittleness of the material in heat affected zone( HAZ). The material in HAZ fractures before the weld metal since it could hardly follow the plastic defamation of the wall of the chord for non-rigid connections. FE analysis was used to study the mechanical behavior of welds and effective length of welds was derived for joints with different parameters. The prediction formula for axial tensile strength of welds is proposed according to the method of effective length based on experimental research and FE analysis,which meets the reliability requirements in specifications.