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High-strength steel (HSS) members with welded sections exhibit a notably lower residual compressive stress ratio compared with common mild steel (CMS) members. Despite this difference, current codes often generalize the findings from CMS members to HSS members, and the previous unified residual stress models are generally conservative. This study focuses on the membrane residual stress distribution in Q690 steel welded box sections. By leveraging experimental results, the influence of section sizes and welding parameters on membrane residual stress was delved into. A larger plate size correlates with a decrease in the residual compressive stress across the section, with a more pronounced reduction observed in adjacent plates. Additionally, augmenting the number of welding passes tends to diminish residual stresses across the section. Results showed that membrane residual stress adhered to the section's self-equilibrium, while the self-equilibrium in the plates was not a uniform pattern. A reliable residual stress simulation method for Q690 steel welded box sections was established using a three-dimensional thermal–elastic–plastic finite element model (3DTEFEM) grounded in experimental data. This method served as the cornerstone for parameter analysis in this study and set the stage for subsequent research. As a result, an accurate unified residual stress model for Q690 steel welded box sections was derived. [ABSTRACT FROM AUTHOR]

There is a lack of reliable research regarding the current engineering specifications considering the broad applications of high-strength steel (HSS) in civil engineering. Axial compression tests were performed on 12 HSS welded H-section stub columns using Q420–Q960 grade steels to study their local buckling behavior. In addition, we performed a parametric analysis using a finite-element model (FEM). Prior to the tests, the initial geometric imperfections and material properties of the specimens were measured to ensure that they satisfy the relevant engineering specifications. Twelve specimens exhibited typical local buckling. The axial deformation and axial strain were analyzed, and the utilization rate of the steel strength decreases with an increase in the yield strength and width–thickness ratio. Furthermore, a close relationship was observed between the occurrence of local buckling in the flange and the web. The results also indicate that the postbuckling strength of the axially compressed HSS welded H-section stub columns with slender sections cannot be ignored. The test results were used to verify the accuracy of the FEM, which considers the initial geometric imperfections and welding residual stress. For the Q420–Q960 steel welded H-section stub columns, parametric analysis was performed using the verified FEM to evaluate the limits of the width–thickness ratio and ultimate axially compressed bearing capacity. To apply current European, American, and Chinese codes, the modification factors for the width-thickness ratio limit and ultimate bearing capacity are given. [ABSTRACT FROM AUTHOR]

Predicting the shear strength of composite girders is critical in improving the efficiency of bridge engineering. To investigate the shear behavior of slender continuous steel–concrete composite girders commonly employed in bridge structures in hogging moment regions, experiments were conducted on three slender two-span continuous composite girders with the moment/shear ratio of the section at the interior support as the test parameter. The test results showed that all three continuous girders experienced web shear buckling and shear failure of the concrete slabs. As the moment/shear ratio increased from 0.59 to 0.89, the shear strength decreased by 12.5%. The shear strengths of the specimens were evaluated using the design methods in the existing AASHTO and Eurocode 4 codes, as well as the one proposed by Liang et al. They were 21%–38% and 33%–50% higher than those calculated by the existing AASHTO and EC4 codes, respectively, indicating that the two codes yielded very conservative results. A numerical study was conducted using the nonlinear finite element model validated by the test results. The results showed that the moment/shear ratio, concrete slab thickness, and web height-to-thickness ratio all significantly influence the shear strength; the codes will yield increasingly conservative predictions with the increase of concrete slab thickness or web height-to-thickness ratio. Both test and numerical results revealed that the design method proposed by Liang et al. can better predict the shear strength of continuous composite girders in hogging moment regions. [ABSTRACT FROM AUTHOR]

The residual compressive stress ratio of high-strength steel (HSS) members with welded sections is significantly lower than that of common mild steel (CMS) members. However, current codes apply the residual stress results of CMS members to HSS members without adjustment. This study investigated the membrane residual stress distribution of a Q690 HSS welded H-section. The membrane residual stresses of five specimens of different sizes were measured using the sectioning method, resulting in simplified membrane residual stress distribution models. The influences of the width-thickness ratio of the flange and web and the thickness of the flange and web were analyzed. The results indicated that while the welding membrane residual stress satisfied the self-equilibrium of the section, the self-equilibrium of the plates followed an inconsistent pattern. A three-dimensional thermal elastic–plastic finite element model (3DTEFEM) was established to simulate the specimen welding process, and the measured results were used to verify the 3DTEFEM. This model was then used to conduct parameter analysis on the plate width-thickness ratio of the H-section, leading to the development of a unified membrane residual stress pattern for the Q690 steel welded H-section member. [ABSTRACT FROM AUTHOR]