Fe-Mn damping steel is a promising structural material that exhibits excellent damping capacity, high ductility, and stable strength characteristics, making it suitable for seismic and vibration-sensitive structures. This study presents an integrated experimental and numerical investigation on welded I-section beam-columns made of Fe-Mn damping steel under combined axial compression and minor-axis bending. A total of seven specimens, including one Q235 carbon steel reference, were tested under eccentric axial loading, with measurements focusing on initial global and local geometric imperfections as well as load-lateral deflection responses and failure modes. Additionally, acoustic tests were conducted on both damping steel and Q235 specimens to quantify their noise attenuation characteristics under mechanical excitation. The finite element models were calibrated using the results from the present eccentric compression tests and a prior axial loading study. Following validation, the models were used to conduct a parametric study covering a wide range of cross-sectional geometries, member slenderness levels, and loading scenarios. The resulting numerical data were employed to assess the resistance predictions provided by existing design standards, including EN 1993-1-1, ANSI/AISC 360-22, and GB 50017-2017. The comparison indicated that EN 1993-1-1 yields generally acceptable yet scattered predictions, while the ANSI/AISC 360-22 method tends to produce non-conservative estimates with substantial variability when applied to damping steel members. In comparison, GB 50017-2017 offers overall conservative results but with relatively high dispersion. To improve predictive accuracy, a modified design framework was proposed by concurrently refining the buckling curve and recalibrating the interaction factors. Reliability analysis conducted in accordance with EN 1990 confirmed the effectiveness of the proposed method, with a derived partial safety factor of 1.140.
Steel joints play a crucial role in the overall behavior of structures. As a result, both researchers and practitioners have made significant efforts to improve joint design and develop reliable calculation methods. One widely adopted solution for assembling joints with hollow column sections is the use of long bolts, typically consisting of threaded rods with nuts, this approach also enhances both stiffness and resistance. However, long bolts have not been extensively studied in cases where the column is an open section, nor are there established formulations for their structural analysis in such configurations. Therefore, this paper proposes a mechanical model to calculate the stiffness of the tension zone of the column when the joint is assembled using long bolts. The mechanical model is applicable to symmetrically loaded double-sided joints in which the column is an open H or I section, connected using long bolts. It consists of three components: the column flange in bending, the column web in tension, and the long bolts in tension. The proposed formulation is supported by an experimental campaign of six specimens, as well as a parametric study using calibrated finite element models. The numerical models were calibrated against experimental results, specifically force-displacement and force-deformation curves.
Fe-Mn damping steel exhibits excellent damping characteristics and mechanical properties, providing an innovative material solution for vibration and noise reduction in modern building structures. This study systematically investigates the flexural behaviour and acoustic performance of composite slabs incorporating closed Fe-Mn damping steel profiled sheets through four-point bending tests on four damping steel specimens and one Q355 conventional mild (CM) steel control specimen. Based on the experimental results, the typical failure modes were revealed and the effects of rib height, rib pitch, and concrete thickness on the flexural behaviour were examined. The test results were further compared with design methods in accordance with the current Chinese (JGJ 138-2016) and European (EN 1994-1-1) standards, demonstrating that the design provisions are conservatively safe and can be directly applied to the design of such damping steel composite slabs. In addition, acoustic measurements confirmed the superior noise reduction performance of the damping steel compared with CM steel. This research provides valuable reference for the engineering application of structural components that integrate load-bearing capacity with vibration and noise reduction functions.
Stainless steel angle sections are widely used in building structures due to their structural simplicity, efficiency in carrying axial forces, and excellent corrosion resistance. This study presents a comprehensive numerical study on the block shear behaviour and design of bolted stainless steel angle connections. An advanced FE simulation framework incorporating full-range constitutive model, fracture criterion, and material anisotropy was developed and validated against existing experimental results. Parametric analyses were then conducted considering different combinations of stainless steel grades (austenitic S304 and duplex S2205), bolt hole diameter, end and edge distances, bolt gauge and pitch distances, plate thickness, and the number of bolt lines and rows. The results showed that increasing the number of bolt rows, end distance, and pitch distance enhanced the ultimate tensile resistance by enlarging the effective shear area, while more bolt lines, larger gauge and edge distances improved the resistance through the increase of effective tensile area. In contrast, the outstanding leg width, bolt hole diameter and plate thickness had a limited influence on the normalised ultimate resistance. A consistent block shear failure mechanism was observed for all connections. Austenitic stainless steel specimens exhibited two failure modes, including tensile necking with shear cracking and tensile necking with shear yielding, whereas duplex stainless steel specimens showed only the tensile necking with shear yielding mode. Comparisons with existing international design standards revealed notable discrepancies. Therefore, a modified design approach was proposed to improve the accuracy of block shear resistance predictions for bolted stainless angle connections.
This fundamental study investigates possible causes of crack initiation observed at the ends of hangers in a through-type steel arch bridge located in Nagasaki, Japan. Through analysis of long-term measurement data and eigenvalue analysis, it was determined that the primary factor in crack initiation was not the vibration of the hangers themselves but rather the wind-induced buffeting response of the entire bridge structure. The vibration modes responsible for fatigue crack development were estimated using response spectrum analysis and forced displacement analysis. Additionally, by examining the actual damage locations and structural responses, hangers that may be susceptible to future fatigue damage were identified. This comprehensive approach provides valuable insights into the mechanisms of hanger end crack initiation in through-type steel arch bridges and offers guidance for preventive maintenance strategies by focusing on the critical vibration modes identified by global analysis.
This study systematically investigated the corrosion damage evolution and mechanical property degradation mechanisms of Q345 steel, 316L austenitic stainless steel, and 2205 duplex stainless steel. A 2000-hour copper-accelerated salt spray test was conducted. The results reveal distinct differences in corrosion morphology and degradation mechanisms among the three steels. Q345 steel undergoes uniform corrosion, leading to a continuous degradation pattern. In contrast, both stainless steels are characterized by localized pitting corrosion, with 2205 duplex stainless steel exhibiting the highest pitting resistance owing to its duplex microstructure and greater alloy content. Mechanical tests demonstrate a decline in both strength and ductility with prolonged exposure. Q345 steel suffers the most severe degradation in mechanical properties, while 2205 duplex stainless steel maintains the best mechanical stability. Based on the experimental data, a corrosion damage variable is introduced into classical constitutive models, leading to the development of a time-dependent dual-hardening model and a Ramberg-Osgood model. Validation analysis indicates that the piecewise-function-based dual-hardening model characterizes the mechanical response of corroded materials during both the hardening and necking stages more accurately than the Ramberg-Osgood model, with an average prediction error only one-quarter of the latter. The established corrosion constitutive relationship provides a critical theoretical and modeling basis for assessing the durability and performing numerical simulations of steel structures in corrosive environments.
Multiple cracks frequently observed in welded connection of orthotropic steel bridge decks, highlighting the need for a systematic understanding of their co-evolution mechanisms. This study investigates the interaction of coexisting surface and embedded cracks using the numerical simulations viaAbaqus-FRANC3D. The stress fields of both crack types are analyzed under coplanar and non-coplanar conditions. Furthermore, the effects of crack spacing, embedded crack aspect ratio, and depth on stress intensity factors, crack propagates rates, and fatigue life are systematically evaluated. Results indicate that the relative positioning of cracks significantly affects fatigue behavior: coplanar configurations accelerate crack propagation, while non-coplanar configurations shield it. Key parameters, including initial crack spacing, embedded crack depth, and aspect ratio of the embedded crack all affect the fatigue life of welded joints. It is worth noting that under coplanar conditions, increased crack spacing accelerates propagation and significantly shortens fatigue life. In contrast, under non-coplanar conditions, greater spacing enhances the shielding of the embedded crack, leading to earlier crack arrest. These findings offer valuable insights into the interaction mechanisms of multiple cracks and contribute to the improved lifecycle management of welded structures.
Significant interface slip may occur between the slab and steel beam in steel-concrete composite beams under prestressing. Owing to their lower stiffness, GFRP-concrete slabs may induce larger interface slip and higher shear demands on connectors than conventional concrete slabs. This study presents a refined analytical method for predicting the slip behavior of prestressed GFRP-concrete-steel composite beams. Extending conventional sectional analysis, the proposed model explicitly incorporates the influence of the GFRP plate, shear connector stiffness, and shear connector arrangement. To verify the accuracy of the theoretical method, two GFRP-concrete-steel composite beam specimens were fabricated and tested. In parallel, a series of numerical models were developed to further validate the analytical method. Comparisons among experimental, theoretical, and numerical results confirmed the reliability and accuracy of the proposed analytical model. Furthermore, parametric studies are conducted to investigate the effects of key design parameters on slip between composite slabs and steel beams. The results demonstrate that incorporating GFRP plates increases the interface slip, whereas densifying shear connectors near the prestressing load zone effectively reduces slip in the composite beams. The proposed analytical approach provides a practical and accurate tool for analyzing and optimizing the shear connector arrangements of GFRP-concrete-steel composite beams under prestressing loads.
With the revision of seismic design standards, there is a growing need to focus on seismic retrofitting of existing reinforced concrete structures. In particular, for reinforced concrete columns that do not incorporate seismic reinforcement detailing, there is a high risk of brittle shear failure during an earthquake. Moreover, when observing the most severely damaged buildings after actual earthquakes, it is often found that the majority of these buildings did not have seismic design provisions. In this study, four full-scale RC columns were constructed using aramid FRP. After reinforcing the bending and shear regions of I-shaped RC columns, cycle loading experiments were conducted. The experimental results closely matched the expected design strength. The study confirmed the effectiveness of aramid FRP in enhancing the strength and ductility of the columns. It is anticipated that aramid FRP reinforcement will be highly effective for elements with inadequate seismic design or those in need of repair and reinforcement.
Helicopter rotor blades made of composite materials operate in a highly dynamic and unsteady aerodynamic environment, sometimes resulting in delamination and cracking of the blade skin. In this study, the in-plane tensile and flexural properties of [(0/+/- 45/90)2]f and [(+/- 45)8]f woven carbon and glass fiber-epoxy matrix composites, which are commonly used as blade skin materials, were investigated experimentally under tension and bending loads using ASTM standards. A skinny anti-adhesion PTFE tape was placed in the neutral plane of the samples while laying to artificially generate delamination. The results revealed that carbon woven fiber epoxy laminates are preferable owing to their rigidity, strength, and low density. However, with a significantly more brittle structure, carbon fiber epoxy laminates are more sensitive to delamination; therefore, tighter control measures are necessary during both manufacturing and operation.
Epoxy joints exhibit shorter curing times and simpler construction compared to wet joints, significantly improving the construction efficiency of prefabricated steel-concrete composite (PSCC) beams. To assess the applicability of PSCC beams with epoxy joints in the negative bending moment regions, a single-point bending test was performed on one PSCC beam with epoxy joints and one ordinary steel-concrete composite (SCC) beam without joints, followed by a comparative analysis of their mechanical behavior. Furthermore, parametric analyses were carried out using a finite element simulation method validated by the tests, focusing on the shape, location, and number of epoxy joints. The results show that the yield and ultimate loads of PSCC beams decreased by 12.1% and 10.4%, respectively, compared to SCC beams. Under prestress, however, the cracking load and ductility increased by 33% and 17.6%, respectively, while sectional rotation performance was enhanced. Moreover, keyed and stepped joints demonstrated better ultimate load capacity and ductility in comparison to linear joints. As the joint location shifted closer to the mid-span and the number ofjoints increased, both ultimate load capacity and ductility gradually decreased. Design recommendations were provided to offer valuable references for the intelligent construction of PSCC beam bridges with epoxy joints.
The presented work concerns the analytical formulation of a shear deformation theory for beams. First, a review of recent studies on various shear deformation theories used in modelling beams, plates, and shells is provided. The principal objective is to develop an effective and simple individual shear deformation theory of beams derived from the classical shear stress formula. Unlike many existing approaches, the solution is obtained analytically in closed form without predefining specific shear deformation functions. The formulation enables the analysis of sandwich beams with constant or variable width and stiffness, including non-homogeneous materials. Parametric functions are introduced to describe these variations, allowing a broad range of beam geometries and stiffness profiles to be examined. The analytical results exhibit very good quantitative agreement with finite element analyses, with peak relative differences of 0.714 % in maximum deflection and 0.223 % in maximum shear stress. Applications include the standard I200 beam and non-homogeneous sandwich beams.
In this study, the vibration of a nanowire supported with elastic springs is analyzed under size effect. Classical strain gradient theory is used to account for the impact of small size, while the vertical displacement function is represented by two constant coefficients at the boundaries and a Fourier sine series within the domain. The effects of perforation and short fibers are considered in the geometry and material, respectively. Stokes' transformation is applied to force the springs at the boundaries to the desired supporting condition. High-order force boundary conditions are used for this purpose. Unlike the natural boundary conditions typically found in most previous studies, the results obtained in this study have a physical meaning since force conditions are used. Thanks to the coefficients matrix obtained, the differential equation does not need to be solved again for each change in boundary conditions. The solutions for elastic boundary conditions are compared with those in the literature, showing a perfect match. The unique aspect of this paper is the presentation of a method that can solve both rigid and deformable boundary conditions of perforated and short-fiber-reinforced nanowires for lateral vibration based on the classical strain gradient theory.
To address the challenges associated with post-earthquake repair of connections between double-steel-plate composite shear walls and H-shaped steel beams, a replaceable joint is proposed that integrates a dual energy dissipation mechanism combining friction and ductility. Two-stage energy dissipation is achieved through slip friction at slotted holes in the web of U-shaped connectors and plastic deformation of their flanges, thereby confining plastic damage effectively to the replaceable unit. This design fulfills the seismic objective of a "strong main structure-weak joint" concept, facilitating rapid post-earthquake replacement and repair. A detailed ABAQUS finite element model of a composite shear wall joint incorporating U-shaped energy dissipation devices has been established based on the dimensions of wall-beam joints commonly used in engineering practice. The effects of the web thickness, flange thickness, discontinuity length of the U-shaped connector, and bolt pre-tightening force on the seismic performance of the joint are investigated. Parametric analyses reveal that increases in the web and flange thicknesses of the U-shaped connectors, reductions in the discontinuity length, and increases in the bolt pre-tightening force enhance the load-bearing capacity. However, excessive web thickness reduces ductility, and an increase in flange thickness tends to cause plastic damage to shift to the web. Moreover, when the preload exceeds 100 ken, frictional energy dissipation within the joint is suppressed. Finally, based on the parametric analysis results, a semi-empirical formula is proposed for predicting the load-bearing capacity as a function of geometric dimensions and bolt pre-tightening force, exhibiting a maximum error within 10%.
This paper presents the results of tests dealing with steel joints made using reinforced resin injection bolts set in oversized bolt holes. Joints of this type may be applied in the cases where increased assembly tolerances are required. A RenGel SW404 + HY2404 epoxy resin was used to inject the holes. The results have been compared against joints with standard size bolt holes. Obtained results have been supplemented with material tests performed on unreinforced resin. Two alternative options for reinforcing joints were considered in the cases where nonstandard oversized circular holes were applied. An addition of silicon carbide varying in granularity was proposed as the first option using two application modes. Reinforcement with steel bars was proposed as the second option. The tests performed have shown, that that the standard joints and the joints with oversized holes reinforced with steel bars behave satisfactorily when subjected to both short and long term loads. Manufacturing defects and substantial dispersion of results were observed in joints with oversized bolt holes injected with unreinforced resin. Values of basic strength and material parameters are given for both reinforcement options. Manufacturing issues pertaining to execution of joints with reinforced resin are discussed as well.
The beam-column connection approach significantly impacts the seismic performance of frame structures. This report proposes a novel resilient prefabricated hinged beam-column joint equipped with rotation control and energy-dissipating load-bearing capabilities (RCEL-RPHJ). The design facilitates off-site prefabrication and on-site assembly, encompassing a prefabricated column with cantilevered section, a prefabricated beam, and a hinged core area with rotation control. Initially, the paper details the configuration, assembly process, and working mechanism of the RCEL-RPHJ. Subsequently, a numerical simulation analysis of the RCEL-RPHJ is conducted following the validation of the finite element modeling strategy. And taking into account 10 different factors, a parametric analysis was performed on a total of 18 finite element models of the RCEL-RPHJ. Findings reveal that the secondary peak load of the RCEL-RPHJ exceeds initial peak load by 7%. After loading, plastic deformation is concentrated in the cover plates, lateral plates, and limiting bolts of the hinged core area, with no significant inelastic deformation in other main components. For optimal rotational control and energy dissipation, the specification of limiting bolts should be M20 or larger, and in configurations with a cantilever, the distance between the hinge core and the column end should be less than 545 mm.
This study numerically investigates the impact resistance of circular steel tubes coated with polyurea elastomer under low-velocity drop-weight impact. A total of 144 finite element (FE) models of composite tubes and 24 uncoated steel tubes were established to systematically analyze the effects of polyurea thickness, spray position, length-to-diameter ratio (alpha), diameter-to-thickness ratio (gamma), and impact energy (Ek). The failure modes are classified into three types: local denting (L), global bending (G), and coupled deformation. The latter refers to a combination of L and G, further distinguished as "L+G" (local denting dominant) or "G+L" (global bending dominant) based on which component contributes more to the total displacement. This method was developed using a modified equalarea axis method combined with bottom bending angles. Results demonstrate that double-sided polyurea coatings (4 mm thickness) most effectively suppress radial bulging and enhance energy absorption, particularly under highenergy impacts (Ek <= 11.2 kJ). The Discussion section validates failure modes in bare steel tubes using the P0/lambda Pc ratio and proposes a new dimensionless criterion incorporating coating parameters to accurately predict failure modes in composite tubes. The parametric analysis provides fundamental insights for optimizing polyurea reinforcement strategies in industrial pipelines susceptible to accidental impact.
This paper proposes an effective procedure for evaluating the influence of uncertain input parameters on the dynamic responses of the steel structures. Uncertainty in material properties, geometrical characteristics, and the mass density of steel structure involved with each member considered the individual random field in the entire frame structure under different seismic loads. The Monte Carlo simulation (MCs) is effectively integrated with the advanced nonlinear inelastic dynamic analysis program to thoroughly account for second-order effects. The Hilber-Hughes-Taylor method associated with the Newton-Raphson balance iterative algorithm is used to solve the nonlinear equations of motion. The results indicate that uncertain input parameters significantly affect the dynamic response of steel structures, with variations in geometrical dimensions being the most critical. A numerical example demonstrates the effectiveness of stochastic steel frame analysis under dynamic loads, revealing a notable difference in vibration modes of 30-44% compared to deterministic analysis, thereby providing valuable insights into the uncertainty in advanced structural analysis.
The seismic risk and vulnerability of multistorey reinforced concrete (RC) structures built in different eras for various functions vary significantly. However, seismic risk analysis of regional RC building portfolios considering age and diverse functional requirements has rarely been conducted. This paper innovatively considers aging and structural-functional requirements, updating the traditional probabilistic earthquake risk and hazard model. Using the Chinese macroseismic intensity standards and seismic hazard model developed here, a novel monitoring seismic intensity bundle with time histories and spectral curves considering 270,000 acceleration values was generated (nine real stations of the Luding earthquake in Sichuan Province, China, on September 5, 2022 were used). This paper innovatively uses monitoring intensity as an auxiliary scale and Chinese macrointensity as the main quantitative scale to estimate the vulnerability level of 622 RC buildings surveyed after the Wenchuan earthquake in Sichuan, China, on May 12, 2008. A structural seismic vulnerability statistical model considering age and functional requirements is established. The damage to low-height reinforced concrete (LRC) and medium-height reinforced concrete (MRC) building clusters with different ages and functional requirements varies according to the intensity zones. Using mathematical statistics and failure mode analysis methods, a comparison of structural seismic vulnerability considering functional and age effects was generated. In particular, a structural seismic vulnerability plane model considering age and functional requirements was generated via cumulative damage probability (CDP) and two-dimensional plane density estimation. An updated seismic vulnerability index (USVI) function was also proposed, and USVI stripe zones and curves considering structural failure datasets were developed.
The seismic performance of rack storage structures is mainly governed by the beam-to-upright connections, which are highly flexible and show considerable stiffness and strength degradation, along with pinching behavior. To address these vulnerabilities, a steel hysteretic damper is proposed which can be installed at these joints to improve seismic performance and energy dissipation. The damper consists of an L-shaped steel plate with a tapered section which acts as a fuse, yielding under rotational deformation at the joint. The mechanical behavior of the damper is theoretically formulated for the design purpose and it incorporates the derivation of slope-deflection equations for tapered members. The accuracy of the formulation is verified by comparing its prediction with a detailed finite element model in Ansys and OpenSees. The effects of geometric imperfections and buckling is also investigated using a probabilistic approach and finite element simulations. To further investigate the effectiveness of the proposed device, an experimental test on a beam-to-upright connection from a rack subassembly subjected to cyclic loading is simulated and validated in OpenSees. The damper's model is then applied to the validated system, and the cyclic behavior before and after retrofit is compared in terms of hysteretic response and energy dissipation. Results show that the proposed energy dissipation device can enhance stiffness, capacity and energy dissipation capability of the joints. The theoretical formulation, analysis modeling approach and simulations presented in this study provide a detailed insight into seismic behavior of steel rack storage structures.
