Numerical calculation of welds in structures from high-strength steel
Authors:   , Ghimire Abhishek 
Published: April 2024

High-strength steels (HSS) have become more prevalent in the steel market in recent years, bringing environmental benefits in sustainable construction. These steel grades have better tensile strength, toughness, and weldability than traditional steel grades. Steel yield strength continues to increase due to new production processes, which is critical for structural integrity in industries that use welding as a primary technique. The strength of welded joints can be determined by classical or finite element analysis (FEA) based on design guidelines. Numerical modeling is a reliable tool for designing the system and its components, and recently developed welding modeling techniques can save time and effort in fatigue design. However, there is a need for established methods to determine the resistance of welds in structural steels using numerical design models. The prEN 1993-1-14:2021 standard provides two methods for finite element analysis-based design: numerical design calculation (NDC) and numerical simulation (NS). The objective of this study is to develop a numerical design model to evaluate the strength of fillet welds made of high-strength structural steels for use in steel structures. The model uses NDC to calculate the weld strength of HSS transverse fillet lap welds. It is tested and validated using experimental, analytical, and finite element results. The study also determines the strain limit for HSS transverse and longitudinal fillet lap welds, the deformation capacity of transverse fillet lap welds, and provides benchmark examples for NDC. This study focuses on the NDC method, which uses the Regular Inclined Shell Element Model (RISEM) in the Finite Element Method (FEM) to evaluate weld strength. NDC follows standardized procedures and uses shell elements to provide reliable and economical results with minimal computational requirements. However, it does not account for residual stresses and weld shrinkage. The inclined shell element in RISEM represents the geometry and stiffness of welds and controls their stresses in the plane. The study recommends the use of a common inclined shell element with rigid members to accurately represent the geometry and stiffness of fillet welds. A new strength criterion is proposed based on the stresses on the inclined shell element, using the uniform equivalent stress as an indicator. The validity of the method is confirmed by comparing RISEM and test results using finite element (FE) simulation. The proposed design model helps engineers to accurately and efficiently determine the strength of HSS welded joints in combination with FEM. The deformation capacity of HSS transverse fillet lap welds is always less than 1 mm, as measured by Digital Image Correlation (DIC). The fracture surface area more accurately represents the weld strength than the effective theoretical area. The predicted strength based on EC3 and AISC is more conservative than the test strength. However, the expected weld strength calculated using AISC provides a better prediction value. The NDC uses a RISEM to determine weld strength by limiting ultimate stresses.