International Journal of Steel Structures最新文献

Open web steel beams are lightweight and economical flexural members designed for transverse as well as lateral loadings. Despite the fact that it is frequently utilised due to its multiple benefits, its behaviour remains unclear. This study focuses on the failure mechanism and the effect of different parameters on the capacity of an open web steel beam under non-uniform bending. Theoretical, experimental, and analytical studies were performed under a single point load applied at the centre of the span in order to study the behaviour of open web steel beams. A total of fifty nonlinear finite element (FE) models were analysed using the ABAQUS software package, and the behaviour of some models was verified experimentally. The local slenderness ratios distinguish different FE models. Results show similar types of failure patterns and load versus deflection graphs were obtained by analytical as well as experimental investigation, demonstrating a strong correlation between experimental and FE modelling. Along with the global behaviour, a different element of the member undergoing the local failure was noticed. The study examines the reasons for the various failure patterns and offers solutions based on observed behaviour patterns. Results conclude that an open web steel beam resolves one of the fundamental problems of lateral torsional buckling in slender flexural members.

The beam-to-column connections are the most vulnerable locations in steel Moment Resisting Frames (MRFs) subjected to seismic loading. The cyclic deterioration of these structural elements during the earthquakes may cause their failure under subsequent earthquakes. This paper evaluates the post-earthquake behavior of steel moment resisting frames with Welded Unreinforced Flange (WUF) connections modified by introducing Reduced Beam Section (RBS) to improve their seismic behavior. In this regard, investigations were carried out on the connection and structure scales. At the connection scale, a T-shaped beam-to-column connection was modeled numerically and analyzed under several two-phase consecutive cyclic loading in which the maximum displacement amplitude of the first loading phase was varying. Results of this part were used to investigate the effect of multiple loading on the behavior of conventional and modified moment connections and provide data on the range of ultimate rotation capacity for the studied connections. At the structural scale, steel MRFs with WUF and modified RBS connections were compared by performing Incremental Dynamic Analysis (IDA) and extracting fragility curves. Based on the results, it can be concluded that the seismic collapse capacity of the frame with modified connections subjected to consecutive earthquake is considerably higher than that of the conventional MRF.

The outer lanes and emergency lanes of the bridge deck of long-span bridges in which orthotropic steel deck is adopted were replaced with Ultra-High-Performance-Concrete (UHPC) composite deck to create a hybrid bridge deck system. A transverse connection detail was proposed to connect the two different bridge deck forms. Static bending tests and theoretical analysis were conducted on the transverse connection detail to obtain failure modes, ultimate load-carrying capacity, crack resistance, and the collaborative bending performance under positive and negative moments. A calculation method for the ultimate load-carrying capacity considering residual stresses in the UHPC after cracking was provided. The results show that the transverse connection detail has good plastic deformation capacity and collaboratively supports both sides of the bridge deck. The error in predicting the ultimate load-carrying capacity of specimens under positive bending moments using the proposed theoretical calculation method is 3.9%, and for specimens under negative bending moments, the load-carrying capacity is controlled by local buckling of the steel, with a 3.1% difference between theoretical and measured values.

Recently, the fully integral bridge system that integrates the entire superstructures and substructures together to form a monolithic rigid frame has been presented, since it is anticipated that this approach will lead to improvements in aesthetics, economic efficiency, and seismic performance of a bridge system. This study is related to a fully integral steel bridge with struts installed in-between the piers at the middle of the bridge span, which is called a strut-braced pier. Thus, it is expected that the strut-braced pier mainly prevents horizontal loads like earthquake load or vehicle braking load. In this study, the seismic performance of the fully integral steel bridge was evaluated in accordance with Caltrans Seismic Design Criteria which involves displacement criteria, displacement ductility capacity requirement, and member force criteria. The capacities of the member forces and the displacement were determined through nonlinear static pushover analysis using OpenSees. As a result, the fully integral steel bridge met the seismic performance criteria specified in Caltrans with a great margin. A parametric study was conducted to investigate the effect of strut stiffness on the seismic capacities and effects from the horizontal load of the fully integral steel bridge. The results show that the displacement capacity and displacement ductility capacity of the fully integral steel bridge have a slight change when the strut stiffness increases. The member force capacity is primarily affected by the strut-braced pier and increases significantly along with the strut stiffness. The lateral displacement and the sectional member forces are well controlled to a converging value by a proper application of the strut stiffness. Therefore, it was found that the minimum stiffness required for the struts can be defined to sufficiently resist design seismic loads, and thus, the sectional properties of all intermediate piers can be reasonably adjusted by varying only the stiffness of the struts connected to the braced piers. It has a great significance in that such results lead to the feasibility of various economical designs of bridge substructure including piers suitable for each situation.

Transfer columns are the essential elements in a building frame structure wherein some stories are constructed with steel-reinforced concrete (RC) columns and others with RC columns. The stories with transfer columns may suffer severe damage due to sudden changes in strength and stiffness along their heights. This study investigates the structural behavior of transfer columns subjected to axial compressive loading and bending about major/minor axes. Forty transfer columns are modeled in the finite element software ABAQUS to study their failure mechanism, lateral bearing capacity, and ductility ratios. The parameters investigated are the levels of embedment length of the structural steel, and the detailing of lateral ties and the base plate at the truncation zone in the column. It is concluded that hybrid columns have higher lateral strengths than the RC columns but exhibit limited ductility due to the sudden shear failure. The specimen with structural steel extended by 50–60% of clear column height exhibited improved ductility. The precipitous failure of the transfer column is alleviated with the provision of a base plate and anchor bolts at the end of the structural steel section.

To investigate the impact resistance of steel beams with different web openings, falling-hammer impact trials and numerical models analyses were performed, focusing on the impact energy, inter-opening space, and opening diameter. The impact resistance of steel beams with different web openings was analyzed, and damage-assessment curves for web-opening steel beams (WOSBs) under impact loads were established. The results showed that web-hexagonal-opening steel beams (WHOSBs) yielded greater damage-related deformation than web-circular-opening steel beams (WCOSBs) for the same impact energy. The average maximum mid-span displacement of the WCOSBs under the falling-hammer was 86.49% that of the WHOSBs, whereas the average energy absorption rate was 6.07% higher. The WCOSBs were more resistant to impacts than the WHOSBs. The impact velocity and mass were the key damage-assessment parameters, and velocity–mass damage-assessment curves and determination equations were established according to on the WOSBs’ maximum mid-span displacement under hinge-supported restraints at both ends. Thus, this study will serve as a reference for assessing the damages of WOSBs subjected to impacts.

This paper presents a numerical study to investigate the effects of axial misalignment for the fillet welded cruciform joints using the traction stress method. A parametric study, involving 100 finite element (FE) models, was conducted with plate thickness and misalignments treated as independent parameters. In the parametric study, different fillet weld leg sizes were chosen based on the minimum criteria specified in the New Zealand standard (NZS 3404.1). Normalized shear traction stresses were calculated for each plate thickness and misalignments at different cut planes through the fillet weld. In each model, the maximum normalized shear stress occurred at an angle of 15° to the loading plate, which represents the critical angle for weld failure. Finally, based on the results of the parametric study, an equation for the multiplication factor was proposed for the cruciform joint to obtain the maximum normalized shear traction stress for different misalignments and weld size. The multiplication factor obtained from the FEA matched well with the multiplication factor predicted by the proposed equation, and reliability analysis was conducted to confirm the accuracy of the proposed equation.

At present, the seismic structure of recoverable functional bridges based on seismic resilience is one of the hotspots in bridge seismic engineering research. Therefore, a new type of hybrid piers is designed in this paper, which mainly relies on replaceable components to achieve repairable structural performance after earthquakes. At the same time, four-level seismic fortification objectives based on seismic resilience is proposed, and the follow-up stiffness phenomenon is found on this basis. The finite element software OPENSEES was used to perform IDA analysis on a hybrid pier and an ordinary reinforced concrete (RC) pier. The fragility curves and seismic resilience curves of two piers were compared, and the seismic resilience performance and the follow-up stiffness phenomenon of the hybrid pier were studied. The results show that under the action of different seismic waves, the top displacement angle of the pier of the hybrid pier is slightly larger than that of the ordinary RC pier, but the overall difference is not large. The fragility curve of the hybrid pier is slightly larger than that of the ordinary RC pier. However, with the damage to the hybrid pier, the follow-up stiffness phenomenon impacts the seismic performance, which reduces the seismic force acting on the structure and improves the seismic resilience of the structure. The post-earthquake recovery time of two piers under different damage states was determined. Combined with the fragility curves, the seismic resilience curves of two piers were presented. The resilient index of the hybrid pier was always maintained at 0.9–1, and the seismic resilience performance was excellent.

Due to its superior strength and ductility, the utilisation of concrete-filled steel tube (CFST) columns has grown over the last few years. However, due to unequal lateral inflation properties, infill concrete and steel tube slip against one another during early loading phases. This paper presented a novel type of CFST section, a diagonally stiffened CFST column as a solution to this problem. It consists of a circular steel tube with stiffening bars installed inside the outer steel tube from one top end to the diagonally opposite bottom end. The suggested section is presented using various stiffening strategies, including binary, tertiary, and quaternary arrangements. The effectiveness of the suggested column section under an axial load is examined using finite element (FE) modelling, and the validation of the FE model was established using experimental testing carried out by previous researchers on unstiffened and stiffened CFST columns. Analysis was done on specimens of diagonally stiffened CFST columns to evaluate the load-carrying capacity, load vs deformation behaviour, stress distribution, and failure pattern. According to the findings of this study, CFST sections with diagonal stiffeners have higher ultimate load capacity than unstiffened CFST columns. Stiffening bars increase the ductility of brittle infill concrete and eliminate localised steel tube buckling. It was recommended that the number of stiffeners be altered to even numbers since odd numbers of stiffeners can cause asymmetry in the section, which can increase the concentration of stress.

To investigate the bond behavior of the concrete filled steel tubular (CFST) using the molybdenum tailing as the fine aggregate, 24 test specimens of the CFST are designed in consideration of molybdenum tailing replacement ratio, concrete strength, ratio of the filling height to the outer diameter and ratio of the outer diameter to the wall thickness. A series of push-out tests are conducted to analyze the working mechanism, failure mode, and bond stress-slip relation of the test specimens. The results show that the usage of the molybdenum tailing as the fine aggregate has no obvious effect on the working mechanism and failure mode of the CFST regardless of the test parameters, even though a slight difference is observed in the failure processes. The increase in the molybdenum tailing replacement ratio remarkably decreases the ultimate bond strength, but increase the ultimate failure slip of the test specimens whilst the ultimate failure slip shows no distinct change under the same ratio of the filling height to the outer diameter and ratio of the outer diameter to the wall thickness. The CFST test specimens with the molybdenum tailing shows slightly worse bond behavior than those without the molybdenum tailing. The proposed formula for the ultimate bond strength of the CFST with the molybdenum tailing fits well with the test results. Since, the limitations regarding the ultimate bond strengths of the CFST in the existing relevant specifications show the enough safety reserve, the proposed formula can be directly used for the design of the CFST with the molybdenum tailing.