Reducing Weld Sizes in Circular Hollow Section Connections

* 在加拿大，钢结构制造劳动力（用于连接）的成本可占钢结构成本的60%。这一百分比继续上升。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行业的竞争力越来越重要。对于焊接管状结构，这是一个目前的挑战，由于缺乏焊接到圆形空心截面（CHS）的设计指导。这是因为在偏心荷载和非均匀荷载作用下，这种接头中焊缝的性能还没有得到很好的理解。代替指导，设计师“超大”焊缝，以防止故障。这通常是一种安全的方法，但它会导致大量不必要的接头准备和焊接劳动。本研究计划的长期目标是为CHS连接中的焊缝开发更好（更经济，但仍然安全）的设计方法。首先，本研究将确定偏心载荷对两种类型焊缝强度的影响：角焊缝和部分接头熔透（PJP）坡口焊缝。实验室试验将在焊接临界偏心拉伸加载十字形连接（ETLCC）上进行，单侧焊接（模拟CHS连接的情况）。将确定焊缝类型、根部熔深、偏心率（大小和方向）和板元件厚度对焊缝强度的影响。然后，断裂后试验（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、基底金属和热影响区的特性）。这些属性随后将被用于有限元（FE）模型的ETLCC研究方法来模拟焊接断裂。将开发一种标准化方法，用于扩展大规模临界连接试验结果（使用FE方法）。最后，用这种新的方法，有限元模型的CHS连接（焊缝断裂）将被开发，以确定非均匀载荷和偏心载荷对焊缝强度的综合影响。将同时进行大规模的关键实验室测试，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，这将有助于工程师减少焊接尺寸和相关的劳动力成本。它还将支持培养2名博士、3名硕士和2名本科高素质人员。

***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.*****