International Journal of Steel Structures最新文献

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.

To study the effect of surface morphology on the corrosion resistance of weld after de-rusting, corrosion de-rusting tests, metallographic tests, and electrochemical tests were carried out. The relationship between surface morphology after de-rusting and the corrosion resistance at the weld was discussed. Based on the microstructure of the welding surface obtained by metallographic testing, a finite element model of weld corrosion was established to study the effect of the welding surface morphology on the galvanic corrosion process after de-rusting. The results show that the welding surface roughness significantly affects its corrosion resistance. The rougher the welding surface, the smaller the potential difference between it and the surrounding base metal, enhancing its corrosion resistance. Galvanic corrosion at the weld can make the surrounding base metal more susceptible to corrosion. However, this effect diminishes as the welding surface roughness increases. Consequently, during welding de-rusting, a moderate rise in welding surface roughness can effectively reduce its corrosive impact on the surrounding base metal.

Two types of steel–concrete composite track beams with a girder width of 1250 mm are proposed for new straddle-type monorail system in this paper. One is the steel–concrete composite track beam with a flat steel web and the other is the steel–concrete composite track beam with a corrugated steel web. The mechanical properties of the proposed track beams were numerical analyzed via validated simulated method. There were five parameters, including strength grade of concrete, strength grade of steel, steel box girder upper flange thickness, steel box girder web thickness,and steel box girder bottom flange thickness considered in the analyses. The results shown that the bending capacity of the corrugated steel web steel-composite track beams was found to be greatly affected by the concrete with a strength greater than C50, and the thickness of the bottom plate of the steel box girder was an important parameter affecting the ultimate bearing capacity of the steel-composite track beams.

For mountain wind power towers, the foundation adopts rock anchor foundation, which can fully utilize the bearing capacity of the bedrock and achieve the goal of shortening the construction period and saving investment. However, there is still few studies on the mechanical properties of prestressed wedge-grouted rock bolts (PWRBs). The research on rock bolts under prestressed conditions is also limited to scale experiments and steel casing experiments, lacking accurate and reliable on-site full-scale prestressed rock bolt pull-out test results and analysis. Therefore, field pull-out tests in weathered rock formations for prestressed grouted rock bolts (PGRBs) and PWRBs with lengths of 8.0 m, 10.5 m, and 13.0 m, respectively, were conducted to investigate the pull-out behavior and prestress loss of these two types of rock bolts. The test results show that the prestress loss ratio of two types of rock bolts is generally around 15%, and the maximum prestress loss ratio can reach 25%. Besides, the failure mode of two types of rock bolts was that the the steel bars fractured in the free section and were not pulled out. The pull-out bearing capacity of PWRBs is higher than that of PGRBs. Using the prestressed rock bolts with 8.0 m bolt length (6.0 m anchored length) to construct wind turbine tower foundation in strongly weathered rocks can meet the design requirements.

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.

To study the slip performance of main member bar connections in transmission towers, 77 groups of bolted main member bar connections were analyzed, and the influence of eight factors, that is, the number of bolts, bolt grade, angle grade, bolt diameter, angle thickness, angle width, preload, and friction factor, on the slip performance of the main member bar connections was studied. Moreover, a slip curve model was established. The results showed that the load-slip curve presented four stages. The pre-slip and post-slip stiffness first increased and then decreased with an increase in the bolt diameter and number. The slip load increased approximately linearly with increases in the bolt pre-tightening force, friction factor, and number of bolts. The ultimate load of the bolted joint was limited by the weaker bearing capacities of the angle steel and bolt group. These findings can serve as a reference for the design of such structures.

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.

The stability of key compression components in space truss structures has a significant impact on the ultimate bearing capacity of the overall structure. To address the instability issue of compression components and improve their axial deformation, this paper proposes a self-tapping cable-sleeve circular steel tube compression component. This innovative component is designed to effectively address the instability issue, providing a reliable solution. To verify the mechanical performance of the proposed specimen, two sets of six full-scale specimens were fabricated based on the lengths of conventional truss structures. The first set consisted of three full-scale self-tapping cable-sleeve specimens, while the second set consisted of three specimens with the same diameter and wall thickness as the inner tube of the self-tapping cable-sleeve. The self-tapping cable-sleeve circular steel tube compression component comprises an inner steel tube, an outer sleeve, end plates, steel-stranded wire, and steel-stranded wire connectors. Experimental results indicate that the self-tapping cable-sleeve component, due to the constraint provided by the outer sleeve, enhances the stability-bearing capacity of the inner tube. Under the same external load, the axial deformation of the self-tapping cable-sleeve component is five times that of the unconstrained inner tube. Additionally, there were sudden stress drops in the steel-stranded wire during the experiment. Based on the experimental results, this paper discusses methods to eliminate this sudden stress drop.

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.