New research enhances understanding of welded joint integrity
Steel structures are the backbone of modern infrastructure, but even minor imperfections in welded joints can dramatically impact their performance.
HERA’s recent rangahau (research) has uncovered how seemingly small misalignments in welded joints could lead to major vulnerabilities, especially in earthquake-prone regions. PhD candidate Bikram Paul’s innovative analysis using finite element models sheds new light on the critical role fabrication tolerances play in ensuring structural integrity.
Background understanding
Steel structures are designed to NZS 3404 and fabricated to the requirements of the construction category (CC) of AS/NZS 5131 specified for the structure.
It includes essential and functional tolerances defined as permitted deviations including straightness, misalignment, length, width and similar. Some of the geometrical tolerances can have a significant impact on the performance of the welded connections in-service.
Recent rangahau, conducted as part of our seismic research program, has shed new light on improving the resilience of welded structures in engineering applications. Bikram Paul, a PhD student from Te Whare Wānanga o Waikato (the University of Waikato), has explored how axial misalignments in welded joints can affect structural integrity under static loading. His findings provide important insights that will inform the future revisions of the standards including AS/NZS 5131. These results were published in the International Journal of Steel Structures in March 2024.
Figure 1: Testing cruciform welded joints after measuring misalignments.
Welded joints, such as fillet welded cruciform joints, are widely used in steel structures, especially in critical areas that must withstand seismic forces. However, misalignments during fabrication are common and can significantly impact the performance of these joints. Bikram’s study focuses on the effects of such misalignments, particularly how they influence stress concentrations that can lead to joint failure.
What was found?
By leveraging Finite Element Analysis (FEA), Bikram analysed over 100 models with varying plate thicknesses, weld sizes, and degrees of misalignment. His rangahau identified that even small misalignments can dramatically increase stress at specific points, making joints more susceptible to failure. These findings are particularly relevant for structures located in earthquake-prone areas, where reliable joint performance is critical for safety.
A key outcome of this rangahau is the development of a predictive equation that enables engineers to assess the effects of misalignment on stress distribution around the welds, leading to improved design of welded joints. This rangahau also highlights the importance of complying with fabrication tolerances of AS/NZS 5131. The reliability of this model needs to be confirmed through extensive testing as the next step, emphasising its potential to enhance the safety of structures.
This rangahau represents a step forward in addressing the challenges faced by engineers when working with welded joints. By providing practical solutions and expanding our understanding of how misalignments affect joint integrity, Bikram’s mahi (work) has the potential to shape future guidelines and standards for the construction industry.
The study is a testament to the ongoing efforts within the engineering community to enhance safety and performance in structural design, especially in rohe (regions) subject to seismic risks. It also highlights the importance of continuous rangahau and innovation in addressing the evolving needs of modern infrastructure.
For more information, you can access the journal paper through the link below:
