International Journal of Steel Structures最新文献

Based on the current plans for Urban Air Mobility (UAM) in various nations, there is an increasing need for vertiport infrastructure in urban areas. Offshore floating vertiports have potential as they address the space constraints of land-based vertiports and can integrate with maritime transport. However, their susceptibility to environmental factors such as waves has limited their prior development. This study conducted a conceptual design to establish the physical properties and geometry of a floating vertiport. The design process focuses on ensuring stability against mooring breakage and securing UAM vertical take-off and landing stability, with quantitative target performance criteria. The dimensions of the floater were determined by referencing the vertiport design guideline established by Federal Aviation Administration. The response to wave loads was evaluated through hydrodynamic analysis, and the appropriate mooring system was selected. The selected designs, which meet the target performance criteria, were examined through ({T}_{p}-{H}_{s}) diagrams, confirming that appropriately designed floating vertiports could operate stably under significant wave height of up to 2 m.

Raised access floor systems are used in facilities with underfloor air distribution or heavy equipment, such as telecommunication systems. However, the seismic performance of these systems must be evaluated to ensure the safety of occupants. Thus, this study evaluates the seismic performances of R-type access floor systems in general offices. To this end, shaking table tests were performed on three R-type access floor systems (Korean Standard, KS F 4760) according to the ICC-ES AC156 standard, with floor acceleration applied horizontally in one direction. Three systems were designed in which the specimens were connected to the floor using adhesives, anchor bolts, and a new connecting system. This study aimed to analyze the dynamic behavior of the three R-type access floor systems as a function of the connection method between the access floor and the slab. Moreover, the damage limit state was defined based on the performance level. Results revealed that the specimen RT (adhesive connection between the R-type access floor and slab) achieved a life safety level at spectral acceleration, whereas RT-PA (adhesive and partially anchor bolts connection between the R-type access floor and slab) and RT-F (rail-supported system connection between the R-type access floor and slab) secured an operational level.

In high-rise buildings, large member sections are often required, particularly for columns in their lower stories. It is difficult sometime to find adequate member sections provided by steel manufacturers for such members. The use of high strength steel could tackle such difficulties. The aim of this study is to simulate the cyclic behavior of welded unreinforced flange-welded web (WUF-W) connections comprising of high strength steel columns and mild steel beams using numerical analyses. The (WUF-W) connection is a prequalified connection for steel special moment frames (SMFs). Nonlinear three-dimensional finite element (FE) models are constructed for the WUF-W connections. Combining hardening models are also constructed to simulate the low cycle fatigue (LCF) behavior of high strength and mild steel materials based on measured material test data, which are implemented in the FE model. The accuracy of the FE model is verified by comparing measured and calculated cyclic curves of the WUF-W connections.

This paper compares the performance of fin plate joints designed with and without seismic considerations under gravity loading and fire conditions. The non-seismic design, following British detailing provisions, has a thicker fin plate located higher on the beam web and it positions the beam web closer to the column face compared to the seismic design detail based on New Zealand provisions. Finite elements in ABAQUS are used to model the subassembly, which is subjected to the ISO 834 fire with and without a cooling phase. The analyses indicate the same failure mode in both subassemblies, with yielding at the beam web top bolt hole in bearing and fracture of the top bolt in shear. However, under the same fire regime, peak compressive and moment demands of the seismic detail were approximately 25% less than those for the non-seismic detail. When subjected to heating only, time to runaway failure was similar for the seismic and non-seismic detail, occurring at 15.0 and 14.8 min into the analyses respectively. When a cooling phase was included, beginning 10 min after initial fire exposure, both subassemblies recovered without failure. A parametric study showed a larger gap between the beam end and column face decreased compression in the beam but did not significantly affect the failure characteristics of the joint. Use of thicker fin plates was also found to increase the time to failure. The results show that the seismic detailing provides limited improvement over the non-seismic detail for the analysed fin plates.

Recently, some researchers have reported that the friction coefficient is influenced by the contact surface pressure, and the Coulomb and Amontons’ law of friction undergoes breakdown. To develop and apply the bolt that introduces a higher bolt tension to the slip critical bolted joint with the inorganic zinc-rich paint, it is necessary to appropriately evaluate the dependence of the friction coefficient on the contact pressure. This study conducted the friction test, which has various contact surface pressures and application times of contact force, to explore the relationship between friction coefficient and contact surface pressure. The target of faying surface treatment is the inorganic zinc-rich paint coating and blast-cleaned surface, used in slip critical bolted joints of bridges. From obtained results, as the surface pressure increased, the friction coefficient of the inorganic zinc-rich paint case decreased. On the other hand, when the surface pressure varied, the friction coefficient of the blast-cleaned surface case was stable. Considering these slip properties of inorganic zinc-rich paint surfaces, a novel relationship between the friction coefficient and contact surface pressure was proposed. In addition, the theoretical slip strength of bolted joints was calculated using the friction coefficient formulas and the actual contact pressure distribution of the joints. In comparison with the theoretical and experimental slip strength, it was found that the theoretical slip strength calculated based on the proposed friction coefficient formulas depending on contact pressure was closer to the experimental value than that based on the constant friction coefficient and could estimate the tendency of the experimental results.

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.

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.

Previous studies have rarely investigated stochastic robustness of flexible cable dome structures under impact loads. In this study, the dynamic responses and failure modes of a Geiger cable dome structure were analysed under impact loads. The number of components damaged by impact and the loss of internal force in components were used to establish a structural damage index and an equation of failure mode control. Following this, by establishing the impact resistance failure limit state equation and combining the probabilistic and statistical characteristics of each design parameter of the structure, the probability of disproportionate failure of the structure undergoing disproportional damage under the impact load was calculated. Then, the stochastic robustness index ({I}_{text{rob}}) based on the probability of structural failure was proposed, and the key factors affecting the structural robustness were analysed through parameter analysis. The research results indicated the following. First, cable dome structures exhibited three types of failure modes under impact loads. Second, the stochastic robustness index fully reflected the probability of a cable dome structure sustaining disproportional damage under impact loads. Increasing the mass or speed of the impactor both increased the probability of the structure sustaining disproportional damage. An impact occurred closer to the centre of the structure, both the probability of overall structural failure and structural robustness performance increase, but the probability of the structure sustaining disproportional damage decreases. Third, increasing the prestress and cross-sectional area of the components might increase their impact resistance and structural robustness performance.

This paper presents the results of a study comparing the initial corrosion characteristics of thermal spray coatings on Zn, Zn-Al, and Al–Mg thermal spray coatings after one year atmospheric exposure tests at two atmospheric environment sites. The thermal spray coatings were obtained by electroric arc spraying of various metals onto a carbon steel substrate. Atmospheric exposure tests were also conducted for outdoor accelerated exposure tests in which test specimens were applied with artificial seawater. The corrosion properties of these spray coatings were evaluated by surface analysis, film thickness measurements, cross-sectional analysis and anodic/cathodic polarization measurement. After one year of atmospheric exposure testing, white, granular corrosion products were observed on the surface of the Zn and Zn-Al thermal spray coatings, while no significant changes were observed in the Al–Mg thermal spray coating. Similar results were obtained for the surfaces of test specimens in atmospheric exposure tests with artificial seawater. The thickness of the thermal spray coating increased for the Zn thermal spray coating, while no significant change was observed for the other thermal spray coatings. Thus, differences in corrosion behavior were observed due to the composition of the thermal spray coatings. The initial corrosion behavior of the thermal spray coatings was also investigated based on the results of coating morphology and cross-sectional elemental distribution of the coatings.