International Journal of Steel Structures最新文献

The in-plane buckling safety of network arch bridges is studied in seven bridges according to the procedures recommended in the European bridge design codes. The safety is assessed by second order analysis with equivalent geometric imperfection. The buckling mode shape and the imperfection amplitude are established according to two different methods and varied in a parametric and a sensitivity study. It is concluded that the most appropriate method for the buckling mode shape calculation of network arches uses a geometrically nonlinear load–displacement analysis with subsequent eigenvalue analysis. Furthermore, the imperfection amplitudes obtained from the two methods of the European design codes show large differences, while the geometric imperfections measured in real bridges are in between them. If most conservative amplitude recommendations are used, the in-plane buckling may become design controlling. The amplitude should be chosen as a reasonable value between the two design code recommendations and considering the characteristics of the actual bridge.

To address the fatigue issue of U-rib orthotropic steel bridge decks under vehicle loading, a novel J-type stiffening rib (J-rib) structure is introduced. The structure consists of a vertical straight section and a bottom semi-arc, with a deck thickness and height comparable to those of the U-rib. The moment of inertia about the transverse axis is similar; however, the opening design facilitates welding and can significantly enhance the fatigue strength. Due to the asymmetric open section of the J-ribs, existing design codes do not provide adequate design methods. This study investigates a bridge deck with thickness ranging from 14 to 20 mm and a crossbeam spacing between 1500 and 3000 mm. Using ANSYS software, axial load-bearing capacity analysis was conducted to investigate characteristics such as load-bearing capacity, deformation patterns, and plastic zone distribution. A bearing capacity calculation method is proposed based on the stability theory of compression members. Furthermore, the combined compressive and flexural analysis indicate that the influence of vertical loads on the structural bearing capacity is relatively minor. Fatigue life comparisons suggest that the J-rib is theoretically expected to exhibit infinite fatigue life.

This study evaluated the structural performance of four-bolted connections (2 by 2 array) of stainless steel and carbon steel, which are expected to undergo physical changes after a fire, using existing material test data under post-fire condition to perform finite element (FE) analysis. The FE analysis model was developed to investigate the structural behavior of stainless steel and carbon steel double-shear bolted connection in a cooled state after exposure to high temperatures. The validation of FE analysis procedures was verified through the comparison of test results in the literature and analysis predictions. To examine the structural behavior of bolted connections in a cooled state following heating to four specific target temperatures, parametric FE analysis was also performed. Material models incorporating the post-fire material properties of austenitic stainless steel (corresponds to EN 1.4404) and carbon steel (corresponds to ASTM A992) tested by the previous studies were input, and the analysis was conducted under monotonic loading conditions. The target temperatures were set at 20 °C, 400 °C, 700 °C, and 1000 °C, and the structural performances of the double-shear bolted connections with block shear fracture, considering the material properties of both steels cooled in air after reaching these temperatures were compared and the strength reduction ratio between high temperatures (400 °C, 700 °C, and 1000 °C for stainless steel and 400 °C and 700 °C for carbon steel) and ambient temperature (20 °C) was recommended.

GFRP tube concrete-encased steel member is a new form of composite member. The sudden impacts threaten structural safety and service life, it is important to research the impact behavior of the member. Therefore, to investigate the effect of glass fiber orientation on the impact resistance of GFRP tube concrete-encased steel composite members with fixed-simply supported boundary conditions, a total of 30 finite element (FE) models were developed. Based on the correct finite element analysis method, the working mechanisms were revealed by analyzing the full impact process, energy conversion, bending moment, and shear force distribution. The influence of the fiber orientation on the flexural capacity was discussed. The shear force distributions at typical cross-sections were analyzed. Furthermore, the influence of fiber orientation on impact resistance under different impact locations and slenderness ratios was investigated. The results demonstrate that the fiber orientation can significantly affect the flexural capacity, the impact resistance, and the damage of the members. It is apparent that the bending moment contributed by the GFRP tube and concrete can be improved by placing the fibers along the hoop direction. The members with the range of fiber orientation (75°~90°/±60°~±75°) can effectively enhance the impact resistance, and the effectiveness increases with the development of slenderness ratios. The impact resistance is worst and the damage is severe when the fiber orientation is wrapped only in longitudinal direction. This study can provide a reference for the impact resistance design of the GFRP tube concrete-encased steel composite member.

Corrosion will reduce the threshold for the expansion of existing cracks in steel structures. To establish the criterion for the propagation of existing cracks in corroded steel structures, it is necessary to study the microscopic mechanism of ductile fracture in the crack tip area of corroded steel plate. This paper aimed to investigate the void deformation characteristic in the crack tip region of corroded steel plates based on computational cubic cell models. By setting boundary constraint, the computational cell models considering the crack tip stress states with pit effects could be established. The pit did not change the evolution modes of the crack tip microscopic void, but the pit depth and shape had influence on the closing speed and degree of the micro-voids in the crack tip steel. The fracture initiation criterion of corroded cracked steel plates could be established based on the micro void evolution mechanism in the crack tip region considering pit effects.

This paper investigates the optimization of stiffness distribution in semi-rigid joints within both the plan and height dimensions of steel space frames. To achieve this, advanced structural analysis and optimization techniques, specifically the Practical Advanced Analysis (PAA) method and the Slime Mould Algorithm (SMA), are employed. The PAA method are utilized to effectively capture material inelasticity and second-order structural effects. The structural model incorporates a zero-length element consisting of three rotational springs and three translational springs, with rotational spring stiffness values derived from the Kishi-Chen Power Model. This model is instrumental in predicting the nonlinearity exhibited by semi-rigid connections. SMA, a global optimization algorithm, is then applied to determine the optimal solution. This method has performed very well in optimization problems; therefore, it is being utilized for the first time in this type of problem. In this study, the optimization variables extend beyond the cross-sectional properties of beam and column members to include various types of semi-rigid connections. The results, obtained from analyzing two distinct three-dimensional steel frames—a four-story and an eight-story structure—reveal that connection stiffness is distributed more prominently within the structure’s inside plane compared to its edges and corners. Furthermore, the distribution of joint stiffness within the structure’s height either remains constant or increases. Additionally, a reverse relationship is observed between joint stiffness and column stiffness.

‌The behavior of double diagonal corrugated plate-reinforced flat steel shear walls (SSWs) has been studied in this study. Corrugated double plates were used in this research with 5 angles of 90°, 60°, 45°, 30°, and 0° to the vertical axis. Also, three corrugation angles were used for the trapezoidal corrugated plate, including 30°, 45°, and 60°. The reinforcement corrugated plate was used in three thicknesses of 2, 4, and 6 mm. According to the study’s findings, reinforcing a flat wall using corrugated plates of varying thicknesses and angles improved the wall’s maximum strength by 6.1–40.5%. Also, the initial stiffness of hardened SSWs has increased by a minimum of 1% and a maximum of 47.7% compared to the control sample. The results also showed that the increase in the thickness of the reinforced corrugated plate directly led to an increase in the lateral bearing capacity and initial stiffness. Furthermore, due to the reinforcement of the flat plate, energy absorption has increased between 4.9 and 40%. Also, findings indicate that stiffened materials have a higher equivalent viscous damping than unstiffened samples.

The purpose of the present study is to develop an assessment approach of impact load that can consider the effect of ship bows types and impact angle. The impact procedures between various types of ships and bridge are simulated by using FE ((finite element) analysis. The influence of bridge pier stiffness, bow shapes and impact angle on the impact force are discussed. The numerical results of impact load are compared with that of the existing specifications. The various impact responses of peak force, deformation of vessel bow and impact duration are compared with that of the existing specifications. The impact force of ship having the same displacement tonnage bows are very different for various types bows. The empirical formulae for predicting vessel impact forces with considering the influence of impact angle and vessel types are developed.

Cables are vital load-bearing components in cable-stayed bridges, significantly influencing structural performance. Monitoring natural frequencies is a widely used method for assessing cable conditions. This study examines changes in the natural frequency values of cables on the Phu My Cable-Stayed Bridge over time, focusing on comparisons within strands, between opposing strands, on the same pylon, and across different measurement periods. The analysis highlights variations in tension distribution and the influence of factors such as position, length, and measurement time on cable vibrations. These findings offer critical insights for effective monitoring and maintenance, ensuring the safety and longevity of cable-stayed bridges.

The rib-to-deck weld root crack is located inside the U-rib and is commonly treated using rewelding from the deck surface. Due to the challenge of real-time crack state detection post-repair, ensuring the repair effectiveness is crucial. By conducting rewelding tests, the local strain, fatigue crack size, fatigue life, and the crack propagation behavior of the specimens were analyzed. The impact of welding parameters such as welding length, number of welding passes, as well as processes like inter-pass grinding and impact treatment after rewelding, on the repair effectiveness was discussed. The results indicate that the untreated crack exceeding 150 mm and secondary cracks after rewelding exceeding 50 mm require immediate intervention to mitigate further propagation and structural compromise. The local stiffness of the specimen will decrease, and the specimen cannot be restored to its original stress performance after rewelding. The crack growth rate and crack size after secondary cracking are greater than those in the unwelded state. Increasing the welding length will enlarge the length for rapid crack propagation, reducing the fatigue life of the specimen. A combined approach using multi-pass welding, inter-pass grinding, and impact treatment will achieve a better repair outcome, which is recommended in real bridges.