Reducing Weld Sizes in Circular Hollow Section Connections

***在加拿大，钢材制造劳动力（用于连接）的成本可占钢结构成本的60%。这一比例还在继续上升。因此，对于工程师来说，减少连接所需的劳动力，以保持加拿大钢铁业的竞争力，变得越来越重要。对于焊接管状结构，由于缺乏圆形空心截面（CHS）焊接的设计指南，这是一个目前的挑战。这是因为在这种接头中，焊缝在偏心加载和非均匀加载下的行为还没有得到很好的理解。代替指导，设计师“放大”焊缝以防止失效。这通常是一种安全的方法，但它会导致大量不必要的劳动，用于接头准备和焊接。这项研究计划的长期目标是开发一种更好（更经济，但仍然安全）的焊接设计方法。******首先，本研究将确定偏心载荷对两种类型焊缝强度的影响：角焊缝和部分接合渗透（PJP）坡口焊缝。实验室将对单侧焊缝的焊接临界偏心拉力载荷十字形连接（etlcc）进行测试（以模拟CHS连接的情况）。确定焊缝类型、根部熔透、偏心（大小和方向）以及板-单元厚度对焊缝强度的影响。然后，破裂后测试（例如维氏硬度）将用于表征焊缝附近etlcc的局部材料特性（即填充金属、母材和热影响区的特性）。这些特性随后将用于etlcc的有限元（FE）模型，以研究模拟焊缝断裂的方法。将开发一种标准化的方法来扩展大型临界裂缝连接试验结果（使用有限元方法）。最后，利用这种新方法，将建立CHS连接（含焊缝断裂）的有限元模型，以确定非均匀加载和偏心加载对焊缝强度的综合影响。同时，将进行大规模的裂缝关键实验室测试，以验证这些模型。******这项研究将产生新的知识和急需的设计指导，焊接到CHS，将帮助工程师减少焊接尺寸和相关的劳动力成本。支持培养博士2人，硕士3人，本科2人。*****

***In Canada, the cost of steel fabrication labour (for connections) can account for 60% of the cost of a steel structure. This % continues to rise. It is therefore increasingly important for engineers to reduce labour required to make connections to keep Canada's steel industry competitive. For welded tubular structures, this is a present challenge due to a lack of design guidance on welding to circular hollow sections (CHS). This is because the behaviour of welds in such joints, with respect to eccentric loading and non-uniform loading, is not well-understood. In lieu of guidance, designers “oversize” welds to prevent failure. This is usually a safe approach, but it leads to a lot of unnecessary labour for joint preparation and welding. The long-term objective of this research program is to develop a better (more economical, yet still safe) design approach for welds in CHS connections.******First, this research will identify the effect of eccentric loading on the strength of two types of welds: fillet welds and partial joint penetration (PJP) groove welds. Lab tests will be conducted on weld-critical eccentrically tension-loaded cruciform connections (ETLCCs) with one-sided welds (to mimic the situation in CHS connections). The effect of weld type, root penetration, eccentricity (magnitude and direction), and plate-element thickness on weld strength will be identified. Then, post-rupture tests (e.g. Vickers hardness) will be used to characterize the local material properties of the ETLCCs near the welds (i.e. the properties of the filler metal, base metal, and heat-affected zone). These properties will subsequently be used in finite element (FE) models of the ETLCCs to study approaches to simulating weld fracture. A standardized approach for extending large-scale fracture-critical connection test results (using FE methods) will be developed. Lastly, with this new approach, FE models of CHS connections (with weld fracture) will be developed to determine the combined effect of non-uniform loading and eccentric loading on the weld strength. Large-scale, fracture-critical lab tests will be conducted, in parallel, to verify these models. ******This research will generate new knowledge and much-needed design guidance on welding to CHS that will help engineers reduce weld sizes and associated labour costs. It will also support the training of 2 doctoral, 3 master's and 2 undergraduate highly qualified personnel.*****