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Welded plate girders are used in heavy steel construction, industrial buildings and bride construction. Residual stresses are present in all plate structures. They are mainly caused by welding. In addition, they influence the load bearing capacity of these welded components. However, Eurocode (EC) does not provide any specific residual stress patterns for consideration of residual stress impact on load capacity. Hence, the decision for a particular problem has to be made by the designer. Many codes, including EC 3, permit the use of non-linear finite element analysis (FEA) for the design of structures. For that purpose, the contribution gives an overview on recent results derived from welded I-girders made from mild steel S355 and high-strength steel S690QL. Weld residual stresses have been investigated by X-ray diffraction (XRD) on small-scale specimen. In addition, residual stresses of welded component-like I-girders have been studied using the sectioning technique. The results confirmed the beneficial effect of certain edge preparation of the plates by flame cutting prior to welding. High-strength steels like the S690 can contribute to both: increased load capacity and decreased influence of weld residual stresses.
Welded I-girders are used in many applications in steel construction, especially a tailored mixture of different plate thicknesses is difficult to manufacture by rolling. Residual stresses are mainly caused by
welding and it is in most cases impractical to anneal the structures. Eurocode 3 (EC 3) does not provide any
specific residual stress pattern. Hence,
the decision for a particular problem has to be taken by the designer. Stability failures are often decisive in the design of steel beam and column members. Many standards, including EC 3, permit the use of non-linear FEA for the design of structures. Load influencing imperfections are mainly geometric deviations from the
ideal shape and residual stresses(both due to assembly or weld manufacturing). Currently the residual stresses are considered by simplified “robust” procedures fixed in common standards(such as EC 3. Models mostly based on specimens from mild steel. Information about high-strength steels is less
available for realistic assessment of residual stresses in full-scale I-girders. Hence, the scope of this work is the measurement of residual welding stresses on component-like I-girders S355 and S690 by sectioning method and global structural welding simulation.
Welded plate girders are used in heavy steel construction, industrial buildings and bride construction. Residual stresses are present in all plate structures. They are mainly caused by welding. In addiiton, they influence the load bearing capacity of these welded components. However, Eurocode (EC) does not provide any specific residual stress patterns for consideration of residual stress impact on load capacity. Hence, the decision for a particular problem has to be made by the designer. Many codes, including EC 3, permit the use of non-linear finite element analysis (FEA) for the design of structures. Recent developments in the last years, enabled the use of computerized models instead of laboratory experiments. In this scope, the FE-model should include all relevant factors properly. This important if considering that weld residual stresses can be a critical assessment factor. In addition, measuring of residual stresses is difficult, time consuming and expensive, it is therefore common to use founded distribution functions (e.g. Swedish BSK 99). Welding simulation tools offer new possibilities for a realistic assessment of weld-induced stresses and deformations. However, the modeling and the computational effort for large structural components is still not in a practicable range and a simplified methodology is in needed. As a result, a new approach (suitable for capacity analysis) is presented and detailed in the present contribution.
This article presents the latest results of an ongoing national research project on improved models for the prediction of welding residual stresses of thick-plated welded I-girders. The experimental program is presented and the importance of different influencing factors on the residual stresses is discussed in detail. All results are compared for mild (S355J2+N) and high strength (S690QL) steel. Finally, conclusions for further works are drawn.
This article addresses the imperfections caused by the weld assembly in I-shape sections made of two structural steel grades. Load influencing imperfections are assumed as deviations from the ideal shape (e.g. bending distortion) and longitudinal residual stresses. The quality of a numerically aided design of components exposed to either compression and/or bending is significantly affected, depending on these parameters. The Eurocode (EC3) provides robust simplified models. As a result, the Ultimate Limit State (ULS) is approached on a conservative basis. The following investigations are aimed at providing further guidance on these values in component-like specimens. The long term goal is an improved understanding of the load-bearing capacity of such sections. As a first step in this process, the experimental and corresponding numerical studies are presented.
Measurement and numerical modeling of residual stresses in welded HSLA component-like I-girders
(2016)
The present contribution shows the residual stress results obtained from experiments with the sectioning method in comparison to global(structural) welding simulation models on component-like (i.e., large scale) I-girders made
of structural steel grades S355 and S690QL. Plates were welded by conventional gas metal arc welding using two different heat inputs. In addition, the base material was assumed to be stress-free. Based on these results, conclusions and recommendations for the design of welded I-girders are drawn.
The nonlinear analysis became a common tool to precisely assess the load-bearing behavior of steel beam and column members. The failure level is significantly influenced by different types of imperfections, among geometric also structural imperfections (residual stresses). Here are still gaps in the knowledge. Nowadays, 3-D welding simulation developed to a level where it could provide reliable estimation of weld-induced distortion and residual stresses. Nevertheless, modelling and computational effort are still in a less practicable range. In this study a simplified procedure to implement residual welding stresses in continuous large scale members is proposed and the influence on the ultimate limit state of slender members in compression is evaluated for two common structural steel grades. The results showed significant improvements in the utilization of load bearing capacity compared with simplified design methods. The comparatively general approach in this study offers
potential for future optimization.