International Journal of Steel Structures最新文献

This study investigates the influence of microstructural characteristics on the hydrogen embrittlement of SUS304 austenitic stainless steel. The investigation utilized SUS304 sheets with a thickness of 1.5 mm, which were processed by punching with an 8 mm diameter to make specimens. Severe plastic deformation was localized near the punching edge, with the extent of deformation determined by the punching speed. Slower punching speeds induced more pronounced plastic strain, which was closely associated with work hardening and strain-induced martensitic (SIM) transformation. The SIM phase was predominantly observed within a depth of approximately 0.1 mm from the punched edge when processed at a punching speed of 0.25 mm/s, corresponding to roughly 10% of the cross-sectional area of the sample. These microstructural changes led to a significant reduction in tensile and fatigue strength, thereby exacerbating susceptibility to severe hydrogen embrittlement, despite the limited extent of microstructural alteration. Based on these findings, a modified Goodman diagram for SUS304 austenitic stainless steel, incorporating mechanical properties and hydrogen embrittlement behavior, was proposed.

Creep behaviors of high strength structural steels (HSSSs) may lead to progressive collapse of high-rise buildings that widely use HSSSs as material of load-bearing components in incident fires. However, their high-temperature creep mechanisms and damage modes remain unclear, and predictive models of creep life are lacking. This study analyzes the creep rupture data of Q550, Q690, Q890 and Q960 HSSS (including Q690 in both quenching and tempering (QT) and thermal–mechanical control process (TMCP) followed by quenching and tempering (TMCP-QT)) to investigate their creep mechanisms, fracture modes and prediction of creep life. The results show that the creep mechanism of HSSS below 600 °C is power law breakdown creep, whereas a transition in creep mechanism occurs as the temperature above 600 °C. In QT HSSS, creep damage is dominated by power-law and diffusion creep, necking, and microstructural degradation, leading to cavity growth. In TMCP-QT HSSS, damage is associated with reduced dislocation density, precipitate formation, and subgrain coarsening. The Larson-Miller (LM) and Orr-Sherby-Dorn (OSD) methods predict QT HSSS creep life with with about 20% error. For TMCP-QT, LM has a 20% error, while OSD’s error is around 40%, likely due to inaccurate activation energy. Both Monkman–Grant (MGR) and modified Monkman–Grant (MMGR) models are applicable. The four QT steels follow the same MMGR model, whereas the TMCP-QT steel follows a different model. However, MGR parameters are influenced by strength grade, temperature, and delivery condition, and corresponding values are provided.

The impact of lateral supporting stiffness on the column effective length factor and the critical lateral supporting stiffness value at which a column can be treated as sidesway inhibited in modular building systems is unclear due to the release of flexural stiffness at each column end. According to elastic buckling analysis results of 34,650 columns models of which each end is flexural released to a series of levels, and joints are restrained by a series of values of lateral supporting stiffness and a series of values of restraining beam stiffness, the length factor calculation method which considers the impact of lateral supporting stiffness for this type column is proposed. Critical lateral supporting stiffness values at which the column can be treated as sidesway inhibited are found. Furthermore, the safety checking process for this type of column is illustrated through a case study to guide the design of columns in steel modular buildings.

Accurate condition assessment of ageing railway bridges is critical for ensuring structural safety and optimising maintenance decisions. Traditional visual inspection methods, such as the IRICEN (Bridge inspection and maintenance, 2014) 5-point rating system, rely heavily on inspector judgement and often lead to overly conservative evaluations due to their deterministic and worst-case-driven nature. To address these limitations, this study proposes a fuzzy logic-based framework for bridge condition rating, incorporating a 10-point scale and component-wise importance weighting. The approach employs triangular fuzzy membership functions to model condition uncertainty, and aggregates ratings using the Fuzzy Weighted Geometric Mean technique. A Python-based expert system “Fuzzy Bridge Rating System (FBRS)” is developed to implement the methodology. The proposed system was applied to multiple railway bridges, with results from three representative cases presented in this paper. Comparative analysis demonstrates that the FBRS offers more nuanced, realistic, and structurally consistent ratings than the traditional method, thereby improving maintenance prioritisation and resource allocation. The framework is designed for integration into bridge management systems and is especially applicable in contexts where visual inspection remains the primary evaluation tool.

This research quantifies the severe degradation of initial bending stiffness in ring plate-wedge joint caused by connecting plate socket hole defects at 0 to 2 mm depth. Experimental bending tests revealed that defect-free joint exhibited high stiffness at 52.29 kN m/rad, significantly exceeding the code recommended threshold of 20 kN m/rad. Crucially, stiffness declined dramatically with increasing defect depth: joint with 1 mm defect showed reduced stiffness of 23.19 kN m/rad, merely approaching the code limit, while those with 2 mm defects suffered a critical loss, plummeting to 12.83 kN m/rad and failing to meet the standard. Finite element simulations confirmed this detrimental trend, yielding values of 56.33, 26.33 and 13.73 kN m/rad for defect-free, 1 mm defect, and 2 mm defect joints, respectively. This establishes a clear 1 mm defect depth threshold for joint integrity and code compliance, components exceeding this defect level require immediate replacement. Based on practical engineering case research, joint stiffness directly influences structural load-bearing capacity. Alongside, a series of parametric analyses were conducted, and multi-parameter optimization incorporating these findings enhanced structural stability: When initial imperfections are considered, the critical load factor increases by 53.89%, while without considering imperfections, it increases by 50.11%, with material savings of 17.7 tons corresponding to 12.16% optimization efficiency.

Cable cranes are increasingly utilized for the accelerated construction of large-span bridges due to their high lifting and spanning capacities, precise positioning capabilities, and adaptability to challenging terrains. However, the complex cable-pulley interaction between the saddle and main cable poses significant challenges for finite element analysis using traditional methods or programs. To address this, the study proposes a simplified method for the finite element analysis of cable cranes to capture the mechanical behavior accurately, accounting for cable-pulley interaction. In this paper, the predominate analytical methods for the cable crane calculation, including the parabolic method and catenary method, are derived and compared through parametric analysis. Subsequently, a simplified analysis method is proposed for facilitating the calculation of the cable crane, based on the principles of equal cable tensions on both sides of the saddle and the constant unstressed length of the main cable. Finally, the proposed method is validated through analytical solutions and field experiments of the cable crane. This research offers an efficient numerical approach and valuable experimental data for the design and optimization of cable cranes in bridge engineering.

This study investigated the effect of corrosion damage on the load-bearing capacity of steel girder ends under varying support conditions. A detailed finite element analysis was conducted using ABAQUS to simulate corrosion at the girder ends, considering different combinations of thickness reductions in the web and vertical stiffeners based on actual damage patterns observed in bridges. Two support conditions, i.e. healthy (rotationally free) and unhealthy (rotation constrained due to deterioration), were modeled to reflect realistic bridge aging scenarios. Corrosion was assumed to occur below the crossbeam near the sole plate, and 72 different corrosion cases were analyzed. Additionally, it was assumed that when corrosion occurs, the result is uniform thinning of the affected members and that corrosion at the support is spread over the sole plate surface. The results indicated that under healthy support conditions, the load is evenly distributed among components, and the capacity is proportional to the remaining effective cross-sectional area of the web and vertical stiffener. In contrast, under unhealthy support conditions, the load is concentrated on the web on the span side, making the location of corrosion critical. The findings emphasize the importance of considering both the extent of corrosion and the support conditions when evaluating the structural performance of aging steel girder bridges.

This work discusses experimental and numerical findings about the behavior of tapered steel girders. The experimental program included the fabrication and testing of six simply supported tapered zigzag and flat web steel girders tested under central load. The tapered girders were classified into two types: zigzag and flat steel web with three web heights: 400 mm, 600 mm, and 800 mm. The total span of each specimen was 1800 mm, and the clear span between supports was 1600 mm. The main variables in the present experimental tests were the shape and height of the steel web girders. The experimental results for tapered flat web girders show that increasing the web height from 400 to 600 mm and 800 mm significantly improves the ultimate load capacity of the girders by 60% and 30%, respectively. Moreover, the zigzag web girders' ultimate capacity increased by (72%, 44%, and 18%) compared to the corresponding flat web girders. The maximum vertical middle of the span deflections of the tapered zigzag web girders were greater than that of the flat web girders (25%, 22%, and 39%). It was seen that the increase in web heights of tapered girders led to an increase in the ultimate vertical middle of the span displacements.

Column removal in structures can rapidly result in progressive collapse. While the progressive collapse response of regular structures has received much attention in the current literature, relatively, rare studies has been performed on the response of setback irregular structures under column removal scenarios. In this vein, this study analyzes 60 setback steel moment resisting frames, considering ductility levels, design earthquake level, and number of stories. First, structures are subjected to gravity loading and column removal scenarios leading to damage percentage calculation and categorization into different groups from almost fully progressive collapse resistant to highly vulnerable. Results indicate a significant impact of the ductility level and design earthquake level on the probability of progressive collapse. The results also indicate that an increase in the irregularity of the structures will reduce progressive collapse resistance. Yet, the irregular structures with low setback irregularity perform better than regular structures. As well, the results indicate that column removal scenarios in upper stories can increase the risk of progressive collapse due to weak design regulations. To mitigate the risk of progressive collapse in setback irregular structures, it is then suggested that the design parameters such as minimum beam dimensions, minimum base shear, the ductility level and design earthquake level should be changed as per the damage percentage.