Journal of Constructional Steel Research最新文献

In this paper, a strengthened T-shaped concrete-filled steel tubular (CFST) column-steel beam joint is proposed. The joint is strengthened in the core region of the column wall as well as the beam, to avoid buckling of the column wall and outward displacement of the plastic hinge at the beam end. To study the damage modes and seismic performance of the joint, low-cycle loading experiments on two full-scale specimens of the joint were carried out. The results show that each specimen was damaged by plastic hinging of the steel beam flanges, the column walls did not buckle, and all had a good seismic performance. In addition, Abaqus finite element software was utilized to optimize the joints by analyzing the effects of changing the dimensions of the strengthened column and modifying the structure of the beam-column connection. Simulation results show that increasing the thickness and height of the strengthened column wall enhances the joint's load capacity, stiffness, and energy dissipation. it is recommended that the width-to-thickness ratio of the strengthened columns should be at most 0.08 and the beam-to-column height ratio should be kept at least 1.3. Additionally, two optimization methods, reducing the wall thickness of the steel corbel and weakening the steel beam flange, can effectively reduce weld tearing at the beam-to-column connections, while guaranteeing a good seismic performance. It is suggested that the slope of the steel corbel is not less than 1:6.25, and the weakening ratio of the steel beam flange is not greater than 0.267.

Throughout the utilization of assembled emergency steel bridge piers, there is a significant discrepancy in the load carried between different columns, which can lead to premature failure of individual columns and potentially trigger the collapse of the entire structure. Currently, there is no mature method for calculating and implementing load distribution. Based on an improved Fourier series and energy principle, this paper proposes a universal calculation method for the load distribution of columns in assembled emergency steel piers. A specific assembled emergency steel pier is selected as the research subject to conduct model tests and simulation experiments. Through mutual verification of theory, experiments, and simulations, this study analyzes the key factors affecting the load distribution of columns, examines the mechanisms and patterns of their impacts, and explores general principles for the even distribution of loads. The research shows: As the column height or diameter-to-thickness ratio increases, the proportion of load borne by the corner columns and transverse edge columns increases, while the central and longitudinal edge columns see a reduction in their load proportions. A pier-beam linear stiffness ratio based on an overall consideration is proposed. As the height of the columns or the diameter-to-thickness ratio increases, the pier-beam linear stiffness ratio tends to decrease. Using the coefficient of variation of column loads as the standard for evaluating the pier-beam linear stiffness ratio, the recommended threshold for the application of the pier-beam linear stiffness ratio in engineering should be between 3 and 3.86.

This article presents a detailed numerical model of speed-lock (boltless) beam-to-upright connections in steel storage pallet rack systems. The model is capable of predicting initial stiffness and characterising the reaction forces of connector-to-upright interactions. The study examines nine configurations, combining three types of uprights and three types of beams with a common connector. Initially, experimental tests were conducted using the monotonic cantilever test method according to EN 15512 standard, with initial stiffness calculated using a standardised version of the initial stiffness method. Subsequently, a numerical analysis was developed through a finite element model based on the experimental setup. The model introduces new geometric details, evaluating each impact on behaviour, particularly on initial stiffness. Results show that numerical accuracy improves with detailed components such as inclined tabs, more detailed perforations, and 3D weld modelling. The contribution of reaction forces of connector-to-upright interactions to initial stiffness was analysed, considering the impact of the rotation centre’s position. It was found that a lower rotation centre position reduces the connector-to-upright lateral contact contribution while increasing tab-to-slot interaction contributions. The impact of beam height and beam weld position on initial stiffness was also analysed, with results showing that increasing these variables consistently led to increased initial stiffness. Finally, the rotation centre’s position was shown to evolve throughout the test, redefining the contribution of interactions. It clarified that connector-to-upright lateral interaction and tab1-to-slot1 and tab2-to-slot2 interactions have the highest contributions. This information is valuable for rack manufacturers to improve, optimise, and ensure the safety of their designs.

Steel-ultrahigh performance concrete (UHPC) lightweight composite deck (LWCD) is a new countermeasure against fatigue issues for orthotropic steel decks (OSDs). While fatigue response of the steel deck plate in LWCDs is complex: except for normal stress ranges developed in steel deck plate, shear stress ranges are generated in headed stud shear connectors, so the steel deck plate at stud root position is under a complex coupled fatigue response. This paper aims to reveal the coupled fatigue behavior of the steel deck plate in LWCDs. First, three OSD-UHPC composite beam specimens were tested under cyclic flexural loads and the steel deck plates were acted by both normal and shear stress ranges. The tests indicate that although the equivalent fatigue stress ranges in the steel deck plate exceeded the fatigue strengths specified in the Chinese design code for steel-concrete composite bridges, the steel deck plate at stud root position did not develop fatigue failures, indicating that the coupled fatigue strength specified in the design code is applicable for LWCDs. Next, an FE analysis was performed to reveal the coupled fatigue response of the steel deck plate in the LWCD. The distribution of the index values reflecting the coupled fatigue effect was obtained, and the maximum value of the coupled effect was S_max = 0.85, which is lower than the limit value (S_lim = 1.3), implying that the steel deck plate at stud root position should be safe under coupled fatigue actions. Further, a parametric analysis was accomplished to reveal the influence of primary parameters on the coupled fatigue effect.

This paper introduces a core plate replaceable double-stage yield buckling-restrained brace (RDYB). All components of the RDYB are assembled through bolt connections, allowing for the replacement of the core plate without the need to remove the buckling-restraining cover plate, which can significantly simplify the repairing process. Firstly, the configuration and working principle of the RDYB are presented. Secondly, a core plate repairable single-stage yield buckling-restrained brace (RSYB) was designed to demonstrate the effectiveness of the repairing method, and an RDYB was designed to further illustrate the double-stage yield performance of the proposed RDYB. Thirdly, cyclic loading was conducted to investigate the hysteretic performance, failure modes, and cumulative plastic deformation capabilities of the specimens. The test results show that the repairable buckling-restrained brace (RBRB) specimens exhibit stable hysteretic performance and good cumulative plastic deformation capabilities. Moreover, the hysteretic performance of the RBRB specimens remains consistent before and after the replacement of core plates. The outcomes of this study are expected to provide useful references for the development of more repairable and resilient braced structures.

A parametric numerical analysis was conducted to investigate the response of steel wide-flange sections (or I section) to combined axial and lateral far-field detonations upon their weak axis. Two steel sections, W150X24 and W200X71, were selected for this investigation. Utilizing ANSYS LS-DYNA as the Finite Element (FE) tool with a plastic kinematic material model, 30 simulations were carried out. These simulations involved varying the Axial Load Ratio (ALR) at 0 % (representing no axial load), 20 %, 40 %, 60 %, and 80 % under various blast impulses. The chosen material model accounted for strain rate effects and failure criterion. The numerical methodology was validated with two experimental cases, and their displacement plots were closely matched. The top of the column experienced a gradual linear axial load followed by a constant axial load, with a blast pressure applied. The study focused on parameters of maximum and residual axial load capacity, and maximum and residual displacement. The residual axial capacity assessment was performed by applying a slow linear axial loading rate to columns rested in their plastic deformed state. The significance of ALR was notable for the chosen quantities of interest. It was found from the simulations the noteworthy impact of ALR on the section's response to identical blast profiles, leading to scenarios of elastic behavior, plastic deformation, or failure. The Damage Index (DI) was calculated based on the residual to maximum axial capacity ratio, indicating the damage level of the column. Graphical representations between ALR and DI offer insights for building occupancy decisions and retrofitting options, crucial for preserving structural integrity.

The use of corrugated web beams in civil buildings is gradually increasing. Therefore, the effects of web openings on the collapse resistance of corrugated web beam–column structures must be investigated. This study conducts static loading tests on standard corrugated web (SCW) and open corrugated web (OCW) specimens with a failed middle column. The web openings have minimal effect on the preliminary bearing capacity of the OCW specimen compared to that of the SCW specimen. The specimens show similar internal force development trends, deformation zones in the webs at 45° to the flange, and tensile flange ruptures near the failed column. The deformation of the web openings delays the formation of the deformation zone in the connection area. The maximum load-bearing capacity and failure displacement of the OCW specimen are 46.5% and 32% larger than those of the SCW specimen, respectively, which indicates that openings in the corrugated web can improve the collapse resistance of the substructure. A finite element model is used to analyze the effects of various opening parameters, such as the diameter-to-height ratio, margin, and opening eccentricity on the collapse resistance of the structure. The reasonableness of the numerical model is verified by comparing the results of numerical simulations and practical experiments. The diameter-to-height ratio is positively correlated with the collapse resistance of the substructure. To optimize the shear capacity of the beam, the diameter-to-height ratio should be <0.5. When the margin is <1.8 times the height of the beam, the collapse resistance of the structure increases with the increase of the distance between the opening edges. Therefore, a suitable margin is 1.3–1.8 times the beam height. Openings in the pressure zone negatively affect the collapse performance of the substructure. Therefore, openings should be eccentricity-free or located in the tensile zones. The results of this study can be used as a reference for future projects.

This paper takes the deep high-stress fractured soft-rock roadway of Jinfeng Gold Deposit as the research object, analyzes the stress state and deformation failure reasons of the roadway via on-site surveys and physical and mechanical test of the surrounding rock, and reveals the main control difficulties of roadway. The axial compression performance tests of circular and square concrete-filled steel tubular (CFST) columns were carried out. A unified strength-bearing ring mechanical model was established, and the bearing ring strengthening composite support mechanism was clarified. The results show that the bearing capacity of circular CFST column is 1.20 to 1.43 times that of square CFST column when the steel content, concrete strength, and wall thickness of the steel tube were identical. When the intermediate principal stress influence coefficient b = 0, the roadway stability criterion of the unified strength-bearing ring and the bearing ring was consistent, indicating the correctness of the unified strength-bearing ring theory. Engineering practice has shown that, based on the support scheme of circular CFST support, the deformation of the two sides and roof decreased by 82.35 % and 73.12 % respectively, effectively controlling the deformation of the roadway surrounding rock, which is an important guiding significance for the roadway support under similar conditions.

This paper aims to investigate the collaborative working mechanism of the concrete-filled steel tube (CFST) column and steel-shear-links for the composite energy dissipation pier by applying a spring-fiber beam hybrid numerical modeling method, and clarify the influences of different dimensions and design parameters on the seismic performance of the composite pier. The numerical results indicated that the increasing number of steel-shear-links could significantly improve the bearing capacity and lateral stiffness of the composite pier and limit the bending capacity of the tension-bending column base, while it had little effect on the bending capacity of the compression-bending column base and the shear force of the shear link under the specific pier top displacement. The factors including the height and length of the shear link had little effect on the lateral load resistance of the pier. Although the pier height had no obvious effect on the bending capacity of the column base, the lower pier height was beneficial for increasing the bearing capacity and stiffness of the pier. Axial compressive load had no significant effect on the total bending capacity of the two column bases and the shear force of the shear link, but the influence of the second-order effect of axial compressive load would limit the overall lateral resistance of the pier. In addition, a theoretical model was proposed to reflect the force mechanism of the composite energy dissipation pier at different loading stages, and the simplified load-displacement theoretical model was proved to accurately predict the behaviors of the composite pier under the earthquake.

Deformation of buildings during strong earthquakes can be mitigated by energy dissipation of structural members. Generally speaking, buildings are designed to have Strong Column – Weak Beam (SC-WB) action. Therefore, plasticized beam behavior is important. To realize the designed energy dissipation of the beam, buckling must be prevented up to the designed story drift. Beam stability is dictated by geometric and material nonlinearities. Geometric nonlinearity is ascertained from the evaluation equations that incorporate consideration of the beam section, length, and initial imperfections. The Young's modulus and yield stress obtained from tensile test results reflect the material properties of steel. Therefore, the evaluation rarely reflects the influence of material characteristics in the plastic region under cyclic stress. Faced with this concern, this study first applies cyclic material tests to various steel grades and loading protocols. The hardening parameters of Voce–Chaboche model are computed from data based on material test data. Then an investigation at the material level is conducted at the member level through cyclic loading tests of I-shaped beams having different steel specifications. Finite element analysis (FEA) results revealed differences in material behaviors. Finally, a parametric study of the steel plastic behavior is conducted using the experimentally validated FEA model. Based on data obtained from this study, a modification factor for the existing evaluation index is proposed to improve the accuracy of structural capacity evaluations.