International Journal of Steel Structures最新文献

This research presents a comprehensive stability analysis of bidirectional porous functionally graded material (BPFGM) skew plates with varying porosity distributions, employing Higher Order Shear Deformation Theory (HSDT) and a meshfree approach. To model the complex behavior of the BPFGM skew plates, the material properties are graded in both the thickness and length directions according to a modified power-law distribution, incorporating four distinct porosity distributions. The governing differential equations are derived using the energy principle, incorporating the effects of porosity into the material gradation. These equations are solved using a multiquadric radial basis function (MQ-RBF) based meshfree method, ensuring high accuracy and computational efficiency. The analysis examines the influence of key parameters such as porosity fraction, grading index, skew angle, span-to-thickness ratio, aspect ratio on the stability of the plates. The results highlight the significant impact of porosity on the critical buckling load and mode shapes, providing new insights into the design and optimization of BPFGM skew plates in engineering applications.

The column plate of steel storage rack is a plane truss system which is connected by two columns and diagonal braces. The connection joint of braces and columns (brace-column connection joint) is often the weak part of the column plate and even the whole steel shelf. In practical engineering, the strengthening measures are mainly to change the cross-section form of braces and weld the thick plate. This paper mainly studies the influence of spot welding thick plate on the mechanical properties of brace-column joints. Firstly, 24 kinds of brace-column connection joints are designed according to the number of welding spot, the distance between welding spot and the thickness of thick plate. The axial tensile tests are carried out on the 24 kinds of connection joints and 72 test-pieces, and the test phenomena, load–displacement curve, load-strain curve and parameter influence of each group of specimens are detailed comparative analysis. Secondly, the three-dimensional finite element model of each test piece is established. According to the finite element results and test results, the bearing capacity, load–displacement curve, stress distribution and the influence of welding spot strength are compared and analyzed. Finally, the parametric analysis of brace-column joints is carried out, and the influence of the number of welding spot, the distance between the welding points and the thickness of the thick plate on the mechanical properties of the joint is studied. The design formula of the spot welding connection is obtained by modifying the design formula of the fillet weld strength in the code, which provides a reference for the application of this type of joint in the practical engineering.

Graphical Abstract

The web-tapered beams have advantages above the conventional rolled I-sections. They combine economy, efficiency, and aesthetics, especially with flange lateral restraint. In this paper, the effect of tension flange restraint on the lateral-torsional buckling (LTB) moment capacity is investigated numerically using finite element analysis. ABAQUS software is used to construct a finite element model (FEM) which is verified against available experimental results in the literature. A parametric study is carried out using different parameters: tapering ratio, beam length, moment gradient, and cross-section properties. FEM results are compared to the latest AISC Design Guide No.25. The restraint at the tension flange enhances the moment capacity, especially for beams with narrow flanges and long spans. One restraint at the mid-span is found to be adequate. The gain in capacity is more noticeable for gradient moment rather than uniform moment. A design procedure is proposed by considering a factor to the available rules to account for the advantage of tension flange restraint. The proposed equation of the enhancement factor is found to be accurate compared to the FEM.

Surface roughness is an important characteristic of blast-cleaned structural steel plates. This is because the adhesion of the coating and the frictional grip of the bolted connections are related to surface roughness. Surface roughness is usually measured using a surface roughness meter. Because the roughness of blast-cleaned surfaces is not uniform, it varies from position to position. The surface roughness test results obtained from a broad area are more valuable than those obtained from a narrow area. Because the measured values contain deviations, they are measured multiple times and averaged to reduce the influence of deviations. However, to evaluate roughness, it is necessary to clarify the measurement conditions to obtain accurate results. Consider combining these sentences as follows: In this study, the surface roughness of the blast-cleaned structural steel sample was measured at multiple locations to obtain its distribution characteristics. During each sample measurement, the detection sensor of the surface roughness meter was lifted and placed on the steel sample to determine deviations from the actual results. The surface roughness distributions of five blast-cleaned samples were the same under the identical measurement conditions. This indicates that accurate results can be obtained by measuring representative samples, without the need for measuring all samples; actually, 17 measurements were adequate to obtain a mean surface roughness value with a 95% confidence level and a 5% acceptable error rate.

The fracture of randomly corroded steel members is one of the most key issues except the residual strength. Randomly corroded steel member fractures have historically been studied through experimentation. However, experimental results have often been limited in concluding the probabilistic distribution mode of ductility due to corrosion’s randomness. Thus, a corresponding numerical algorithm is necessary to predict the ductility of corroded steel members. The work is conducted based on this background. A numerical algorithm suitable for analyzing fractures is proposed. The reliability of the proposed algorithm is validated by comparison with experimental results and Ls-Dyna code. The influence of element size on ductility is revealed. The factors influencing accuracy of ductility of proposed algorithm are systematically investigated. The fracture of randomly corroded steel bars is analyzed. The results indicated that both E_size and f_s influence ductility. Adjusting the f_s can weaken the influence of E_size. The probabilistic distribution model of maximum strain corresponding to different levels of corrosion severity varies. The work in this paper can provide a novel way for fracture analysis of randomly corroded steel members.

Weathering steel is a high-strength low alloy steel with a dense rust layer formed by alloying elements and corrosion resistance to prevent corrosion from spreading. In recent years, China has developed a new type of Q345 weathering steel (Q345WS). This study experimentally investigates the post-fire characteristics of Q345WS steel at temperatures ranging from 20 to 1000 ℃. The research analyzes the effects of air cooling and water cooling conditions on the steel, particularly focusing on residual strength post-fire. The study also compares the residual mechanical properties of Q345WS steel with those of other structural steels. When exposed to temperatures up to 600 ℃, the loss of mechanical properties could be negligible. The residual mechanical properties of Q345WS steel are significantly influenced by the high temperature and cooling method when the temperature exceeds 600 ℃. The variations in mechanical characteristics between Q345WS steel and construction steel under high temperatures should be highlighted, and comparable with findings from previous literature on various steel types. A series of polynomial prediction equations have been suggested to forecast the alterations in the mechanical attributes of Q345WS following exposure to fire, offering a methodical and conceptual foundation for assessing steel structures and carrying out post-fire retrofitting.

In civil engineering and architecture, truss structures are commonly used in constructing offshore platform structures, bridges, and high-rise buildings. These structures typically use circular hollow sections (CHS) and square hollow sections (SHS), joined by welding. Recently, the use of T-shaped welded joints with different tube shapes has become more diverse, incorporating combinations like CHS-CHS, SHS-SHS, and CHS-SHS. Traditionally, fatigue studies have been conducted separately on these CHS-CHS, SHS-SHS, and CHS-SHS types of connections. However, this study compared the fatigue life of three different welded T-shaped structures. The T-shaped joints with three different types of connections are analyzed through the fatigue finite element method (FEM). First, welding simulations of three different T-shaped connections were performed using the 3D non-steady heat conduction method to obtain heat histories. Then, a 3D thermo-elastic analysis method was employed to calculate residual stress and welding deformation based on the thermal history. In the subsequent fatigue analysis, the fatigue life and initial crack locations of the three different T-shaped structures were determined using the FE fatigue analysis method, which incorporates residual stress and welding deformation. The fatigue FE method is based on the cyclic hysteresis constitutive equation obtained through repeated load experiments and the fatigue damage theory. Finally, the fatigue life of the three types of structures is compared using the S–N curve.

This research investigates the compressive and flexural strengths of cold-formed steel (CFS) members with channel and Z-profiles. The study includes a comprehensive analysis of 500 CFS members. Finite-element (FE) models in ABAQUS, validated by experimental results, assess the influence of various parameters on the capacities of these CFS members. The parameters analyzed include the member length-to-depth ratio, section depth-to-width ratio, plate slenderness ratio, lip-to-flange width ratio, and material yield stress. Results from FE models were compared with those from the Effective Width Method (EWM) and the Direct Strength Method (DSM). A graphical user interface (GUI) was developed to streamline EWM and DSM calculations, enhancing efficiency and accuracy. This study provides valuable insights into the performance of innovative CFS channels and Z-profiles, facilitating a deeper understanding of their structural capacities and offering a foundation for potential applications in modern engineering design and construction practices.

This study proposes a design method for calculating the nominal flexural strength of pre-stressed (PS) mono-symmetric thin-walled steel beam/girders. How to evaluate the flexural strength of conventional steel beam/girders without cables is first summarized, referring to AISC specification. A closed-form solution for LTB of PS girders with deviators under end moments is next mentioned, and a new method to calculate the yield, elastoplastic, and plastic moments of the PS girders is presented. Then, a procedure for determining the nominal strength of the PS steel beam/girders having discretely installed intermediate deviators depending on the laterally unsupported length is presented. Finally, an extensive study is conducted to explore the nominal strength of the PS system by varying the eccentricity, width, and initial pre-stressing force. The results demonstrate that the pre-stressing technique can result in a stiffer and more economical steel girder.

In this study, to analyze the corrosive vulnerable members of an offshore bridge, the corrosive environments and corrosion rate were evaluated according to the installation location. The steel box deck bridge was selected as the target bridge for analyzing corrosive vulnerable members, and the corrosive environment and corrosion rate of the stiffened sections were compared. Based on the assessment results of the corrosive environment, varying corrosion rates were observed depending on the installation location of the sections, with the sections located at the bottom of the pylon showing a faster corrosion rate. Furthermore, it was established that structural members with accumulated surface chloride of 50 mg/m² or more could experience accelerated corrosion, as evidenced by the correlation between the corrosive environment and corrosion rate. The side parts of the sections positioned at the bottom of the pylon received a C4 rating, signifying a higher susceptibility to corrosion than the bottom parts. From these monitoring results, it was confirmed that the relative difference in the corrosion rate of stiffened members, and considering the relative corrosive environments. Considering these differences in the corrosive environments, it is necessary to the maintenance for steel members in offshore bridges.