International Journal of Steel Structures最新文献

This paper presents a numerical study on the yield resistance and ultimate resistance of steel beam with random corrosion damage. The corrosion is considered by introducing random cylindrical pits to the intact steel beam, in which the thickness of the beam, both at the section and along the length of the beam is reduced. Altogether 240 corroded beams are numerically studied, wherein the effects of corrosion ratio, corrosion diameter, corrosion depth and corrosion location on the yield resistance and ultimate resistance of steel beam are considered. It is found that for global corrosion scenario, when the corrosion ratio is 4.76%, 9.26%, 13.37%, 18.25%, 22.36%, and 25.76%, due to the random nature of corrosion, the reduction factors of ultimate resistance of steel beam range from 0.9–0.92, 0.81–0.86, 0.77–0.8, 0.71–0.76, 0.64–0.67, and 0.58–0.64, respectively. Moreover, when corrosion distributes only at the bottom flange or top flange of steel beam, the adverse effects of bottom flange corrosion and top flange corrosion on the resistance of steel beam are the same. The corrosion diameter and corrosion depth have limited effects on the resistance of steel beam. The relationship between the reduction factors for the yield resistance and ultimate resistance with the corrosion ratio of the beam is proposed. It is found that for the global corrosion case, the reduction factors of the yield resistance and ultimate resistance of the beam are linearly and negatively correlated with the corrosion ratio. For each 10% increase in the corrosion ratio, the reduction factor of yield resistance and ultimate resistance decrease by 18.9% and 15.1%, respectively. The resistances of the corroded beam with random corrosion pits and uniform corrosion are also compared. The results suggest that by using uniform corrosion model, the resistance of the corroded steel beam will be significantly overestimated. When the corrosion ratio is about 14%, the overestimation on the ultimate resistance of steel beam by using uniform corrosion model is more than 10%.

The detection of the static strain aging extent of steel structures holds paramount significance in the safety assessment system. Tensile tests were performed on Q345 steel specimens subjected to static strain aging treatment, while simultaneously employing complementary in-situ detection techniques: acoustic emission, infrared thermography, and digital image correlation for real-time monitoring. The physical effect mechanism is initially confirmed through an analysis of the mechanical response of strain aging Q345 steel. The acoustic emission signals from the cluster 3 exhibiting high frequency and low amplitude are linked to the microplastic yield phenomenon. These signals, detected through acoustic emission technology, are considered representative of the dislocation activity in Q345 steel after strain aging. Illustrating via specimen S16-150, it is evident that as strain aging advances, there is a notable decrease of 63.02% in information entropy, 22.4% in partial power, and 55.04% in the wavelet coefficient of typical acoustic emission signals. Subsequently, digital image correlation was utilized to examine the local strain variation associated with microplastic deformation, and it was observed that Lüders bands did not form in specimens S12-150 and S16-150 due to strain aging. Finally, infrared technology was employed to monitor the instantaneous temperature of strain aging Q345 steel, facilitating the examination of its thermal energy conversion efficiency. Specimen S16-200 exhibited a fracture instantaneous temperature that was 21% higher compared to specimen S0-25. These findings establish a solid foundation for the integrity assessment of steel structures.

Single layered domes are susceptible to large deflections and their post-buckling behavior is influenced by the connection system used. Numerous investigations have been carried out on the stiffness characteristics and of hollow spherical joints and their effect on the post-buckling behaviour of domes. However, research on the behavior of circular plated joints and their effect on the dome post-buckling are limited. Factors such as the combination of forces transferred to the joint, thickness of the circular joint plates and location of the joint in the dome have been found to influence the behaviour of the joint and the deformation of the connections reduce the limit point of the dome. Therefore, this study highlights the influence of the deformability of the circular plated joints on the elastic post-buckling behaviour of single layer domes. The deformation of the circular plated joints are investigated by geometric nonlinear finite element analysis in ABAQUS. It is found that the deformations increase with increase in ratio of minor to major force and the variation in stiffness of the plates along these directions are greater for thicker plates. Provision of shear connector i.e., a plate element between the webs of members along the direction of principal tension is effective in limiting the connection deformations. The deformability of the joints under various loading conditions are presented based on the results of the numerical investigations. The effect of the circular plate deformations on the stability of the dome are analysed using the corotated-Updated Lagrangian formulation where, the stiffnesses of the circular plates obtained from the ABAQUS analysis are included as linear springs in series with the members of the dome. Reduction in the limit point of the domes is observed, particularly with thinner circular plates.

Accidents of vehicles hitting columns have happened frequently in recent years. Hence, it becomes important to evaluate the performance of columns under vehicle impact. This paper presents a residual deformation-based method for the vehicular impact performance evaluation of concrete-filled steel tubular (CFST) columns. Before that, a finite-element (FE) model was developed to simulate the responses of CFST columns under vehicle impact and post-impact axial compression and validated by reported tests. Based on the FE model, five performance levels of CFST columns under vehicle impact were divided according to numerical damage states and corresponding residual axial capacity ratios. In the presented performance evaluation method, a residual deformation, i.e., the ratio of the residual deflection at the mid-height to the corresponding height, which is related to the residual axial capacity ratio, was selected as the evaluation index. For the residual axial capacity ratio of 0.85–1.00, 0.60–0.85, 0.40–0.60, 0.20–0.40, and 0–0.20, the residual deformation ranges 0–1.5 × 10^–2, 1.5 × 10^–2–7.5 × 10^–2, 7.5 × 10^–2–1.4 × 10^–1, 1.4 × 10^–1–2.5 × 10^–1, and > 2.5 × 10^–1, respectively. In addition, an analytical model for the residual deformation was proposed. Comparisons show that analytical performance levels by the presented method are completely consistent with numerical results. Due to being residual deformation-based, the presented method can be used for both the performance prediction of CFST columns before vehicle impact and the performance assessment of CFST columns after vehicle impact.

This study evaluated the effect of surface conditions on the hydrogen embrittlement (HE) characteristics of SUS304 austenitic stainless steel, as SUS304 is one of the candidate structural materials for hydrogen energy systems. Various machining processes, including milling (ML), shot peening (SP), and cold rolling (CR), were employed to modify the surface roughness, internal strain, and microstructural characteristics of the test sample. Namely, this approach was conducted as the surface-absorbed hydrogen is related to effective hydrogen: a high internal strain was obtained in the entire CR area along with a rough surface, while SP and ML samples displayed high strain levels near the surface. The strain value was reflected in the hardness level due to their work hardening and strain-induced martensite formation. Concerning this, the hardness values of CR and SP samples were higher than 6 and 2 times the as-received samples. The hydrogen content charged to the samples was contingent upon the strain level: higher strain corresponded to elevated hydrogen content, particularly in CR samples. Despite the notable high hydrogen content in CR samples, HE was not detected in the tensile test. Conversely, even with a low hydrogen content, severe HE was observed in all samples during the fatigue test. The susceptibility of stainless steel to HE proved sensitive to cyclic loading, wherein surface-absorbed hydrogen migrated to the crack tip during cyclic loading. Detailed discussions on the reasons for these observations are provided based on the experimental results.

Steel plate girders substitute conventional hot rolled I-shaped beams in case of high applied loads where it becomes uneconomic to use hot rolled beams. It is more economic to employ tapered sections following shape of bending moment distribution throughout the plate girder. Most of the bridges are designed as simple spans as it is cost-effective which results in pure shear stresses in the tapered end web panels. However, specific design guidelines for tapered plate girders under shear are not available. Initial geometrical imperfections (IGIs) are usually random and depend mainly on the fabrication, shipping and construction processes. As the amplitude of initial imperfection increases, through-thickness bending stresses are enlarged, resulting in a reduction in the ultimate shear strength of the plate girder. As such, this study aims at the investigation of the ultimate shear strength of tapered imperfect end web panels in steel plate girders. The effect of initial geometric imperfections (IGIs) on the ultimate and post-buckling shear strengths of these plate girders is studied using a validated numerical model. Around two hundred finite element models representing plate girders are constructed and analyzed to cover a wide range of geometric parameters including: aspect ratio of end web panel, depth–to-thickness ratio of end web plate, inertia of intermediate stiffeners, and angle of tapering. Moreover, effect of imperfection is considered. Results are used to conclude design guidelines for evaluating the ultimate shear strength of tapered imperfect end web panels.

The use of rolled steel sections is typical in offshore topside, while recent developments are focused on coped sections to accommodate service lines and fire hydrants. Coped beams are better alternatives without compromising the load-bearing capacity and shear strength. On the topside, the use of coped beams is helpful in creating a more orderly, safe, and undisturbed workspace for laying service mains and fire hydrants; otherwise, they pose a general threat to the topside functional safety. Coped beam replaces the stack of service mains without compromising on the strength requirements of the web. Enhanced safety and improved aesthetics of the topside design are additional advantages. The present study investigates a coped beam with functionally graded material (FGM) to accommodate the services mains in a safer mode without losing its strength; corrosion resistance is also investigated as an additional requirement for any leak occurring from the mains. A coped beam of FGM and X52 steel is investigated under conventional loads and compared for their strength and serviceability requirements. Parameters such as cope length and depth are varied as per the design requirements. FGM coped beams showed higher load-carrying capacity even under the larger coped sections. Under deeper web sections, the cope depth and length have a significant impact on the buckling and load-carrying capacity. For all the chosen coped sections, FGM beams registered a significant reduction in buckling stress compared to X52 steel beams in the coped region, indicating the former is a better candidate for such applications.

A lateral-torsional buckling (LTB) experimental study has been firstly investigated for an externally pre-stressed (PS) steel beam with/without un-bonded central deviator. Analytical and numerical studies related to elastic LTB of the PS beam are abundant. However, an experimental study focusing on LTB behaviors of the PS steel beam is newly presented in this study. Six full-scale experimental specimens consisting of two usual steel beams without tendon bar, two PS steel beams under vertical loadings and two PS steel beams under increasing tendon force were tested. Load–strain/displacement behaviors of the specimens were obtained by measuring stains, lateral and vertical displacements. The numerical study of the geometric and material nonlinear behaviors of PS steel beams was evaluated based on the Riks method using ABAQUS. Finally, numerical and experimental results of load–strain/displacement behaviors of the usual and PS beams were investigated. The experimental and numerical results indicated that the LTB strength of steel beams could be greatly improved by prestressing system.

Steel Circular Hollow Section (CHS) joints have been extensively utilized in construction. Current research mainly focuses on joints reinforced in unloaded states, reinforcement under load less commonly addressed. This study examines the mechanical behavior of CHS T-joints through an experimental analysis of six specimens, each featuring varying brace-to-chord diameter ratios (β), welded under different load factors. Identified primary failure modes of the joints are local buckling and out-of-plane inclination. Furthermore, a thermo-mechanical coupling finite element model, considering the material addition during the welding process, was developed to investigate the influence of the welding under load. The results indicate that welding under axial load has little effect on the ultimate loading capacity of the CHS T-joints. Notably, welding-induced residual deformation on the chord surpasses that on the brace, particularly when welding passes are proximal to the brace-chord intersection. Residual stress in welds is not significantly affected by the stress in the tubular; only the stiffeners near the welds are affected. Despite some joints exhibiting out-of-plane inclination, the enhancement in ultimate bearing capacity exceeds 24%.