Search Results (489)

Extended stiffened end-plate bolted connections represent one of the most utilised steel connection types in seismic-prone regions, and several studies have been dedicated to the improvement of their performance. Recently, a new stiffened joint configuration, with a non-symmetric octagonal bolt arrangement, was proposed, highlighting its excellent performance in seismic scenarios. Therefore, two new design procedures according to both the European and North American codes were developed. Within this framework, the present work aims to investigate the performance of this innovative joint under column loss scenarios. A total of sixteen beam-to-column steel assemblies, defined by varying the beam depth and the design procedure, were numerically investigated using advanced FE models validated against experimental results. The numerical results show that the innovative joints exhibit a ductile behaviour, even better than traditional joints designed according to the current versions of EU and US codes. Indeed, the new bolt arrangement allows us to reduce the damage in the connection thanks to a better stress distribution among the bolts. Full article

Bolted connections are critical in deep-sea engineering, yet classical theories (such as VDI 2230) implicitly assume atmospheric pressure conditions, neglecting the volume contraction of components due to hydrostatic pressure. This fundamental flaw hinders accurate prediction of preload retention—especially when bolts and clamped components exhibit differential compressibility (a common scenario in practical applications). To bridge this scientific gap, this paper establishes the first analytical model for bolt preload under pressure-induced volumetric contraction based on deformation coordination relations. The derived closed-form expressions explicitly quantify residual preload as a function of deep-sea ambient pressure, component bulk modulus, and geometric parameters. Model predictions closely match finite element calculations, showing that stainless steel bolts clamping aluminum alloys under 110 MPa pressure can experience up to a 40% preload reduction. This theoretical framework extends classical bolt connection mechanics to high-pressure environments, providing a scientific basis for optimizing deep-sea connection designs through material matching and dimensional control to effectively mitigate pressure-induced preload loss. Full article

In order to comply with the principle of sustainable development in product design, in addition to the mechanical properties of products, recycling properties should also be taken into account at the early stages of design. This paper explores the interplay between mechanical and recycling properties in product design in order to achieve a compromise between these design aspects. The research included typical metrics used to evaluate a product for its mechanical and recycling properties. The tests were carried out on a lap connection made in four variants: as a two-bolt, three-bolt, two-rivet and three-rivet connection. It was demonstrated that the stiffness of bolted connections is significantly lower compared to equivalent riveted connections. On the other hand, using three rivets instead of two in a connection yields better results in terms of load-bearing capacity compared to a similar increase in the number of fasteners in a bolted connection. The results demonstrate the impact of material structure of components and dismantling operations on the financial performance of the recycling process in relation to the assessment of recycling aspects in product design. Full article

This study investigates the finite element analysis (FEA) of beam-to-column bolted extended end-plate moment connections, with a focus on accurately reproducing plastic rotational stiffness. Existing FEA results for six experimentally tested connections from the literature show substantial discrepancies in the plastic range, despite acceptable elastic stiffness. These discrepancies are traced to conventional material modelling practices, where only yield and ultimate stresses are specified, engineering stress–strain data are used directly, and the minimum elongation is taken as the strain at ultimate stress. To address these limitations, the connections are re-modelled in ABAQUS using (i) a multi-linear approximation for the plastic stress–strain behaviour of mild steel plates, and (ii) a proposed bi-linear approximation that requires only measured yield and ultimate strengths but preserves the area under the reference curve. In both cases, true stress–strain values are supplied to the software for plastic analysis. These strategies reduce the average error in plastic rotational stiffness from 46–48% in the existing FEA to about 18% across all specimens, while maintaining good agreement in the elastic range. The results demonstrate that carefully constructed stress–strain approximations, combined with appropriate data formatting in ABAQUS, enable reliable validation of extended end-plate moment connection models and provide a practical basis for future parametric and design studies. Full article

To evaluate the slip resistance of high-strength bolted friction-type connections subjected to different corrosion-protection treatments, calibration tests were performed on six representative faying-surface conditions: sand-blasted (uncoated), epoxy zinc-rich primer, waterborne inorganic zinc-rich coating, alcohol-soluble inorganic anti-corrosion anti-slip primer, a complete multi-layer protective coating system, and cold galvanizing. Fifteen test groups comprising 45 tensile specimens were examined to determine slip factors, which were then compared with values recommended in domestic and international design standards. The results show that sand-blasted surfaces (W type) exhibit stable slip factors of μ = 0.43–0.45; alcohol-soluble inorganic primer surfaces (S type) provide the highest slip resistance with μ = 0.49–0.51, representing an increase of approximately 13%–18% compared with sand-blasted surfaces; and cold-galvanized surfaces (D type) achieve favourable performance with μ ≈ 0.44. Waterborne inorganic zinc-rich surfaces (A type) yield μ ≈ 0.33, corresponding to a reduction of about 25%, and are suitable for non-slip-critical connections. In contrast, epoxy zinc-rich primers (C type) and complete multi-layer coating systems (X type) present lower slip factors of μ = 0.26–0.28 and μ ≈ 0.23, corresponding to reductions of approximately 35%–45% and about 50%, respectively, indicating that the X-type treatment is unsuitable for slip-critical applications. The influence of bolt diameter is limited, with slip-factor variations within 5%–8% under the same surface condition, and no statistically significant effect confirmed by two-way ANOVA. These findings provide a quantitative experimental basis for the design, classification, and future standardization of friction-type bolted connections with coated faying surfaces. Full article

ANSYS software was used to analyze the moment-rotation relationship of semi-rigid steel structure joints with bolted connection. A parametric study was conducted to examine the influence of eight key variables—including bolt number, bolt grade, angle steel grade, bolt diameter, angle steel thickness, angle steel width, preload magnitude, and friction coefficient—on the bending behavior of semi-rigid joints with bolted connection. Parametric analysis reveals that the initial rotational stiffness is most significantly influenced by the bolt diameter, the width and thickness of the angle steel, the bolt preload, the coefficient of friction, and the bolt number. The stiffness exhibited an average increase of 50.6% for every 4 mm increment in bolt diameter from 12 mm to 24 mm. Expanding the angle steel width from 50 mm to 75 mm resulted in a substantial 88.5% average increase in stiffness, while a further width increase from 75 mm to 110 mm led to a smaller average increase of 17.4% per 17.5 mm. Similarly, the stiffness rose by an average of 33.8% for every 2 mm increase in the thickness of the angle steel within the 4 mm to 10 mm range. A 25% increase in bolt preload correlated with a modest average stiffness gain of 2.7%. The rate of stiffness improvement diminished with increasing friction coefficient. In contrast, the initial rotational stiffness exhibited a relationship that is approximately linear with respect to the quantity of bolts. Regarding the ultimate bending moment, the key influencing factors were identified as bolt diameter, preload, coefficient of friction, and number of bolts. The ultimate moment demonstrated a non-monotonic relationship with bolt diameter, characterized by an initial increase, followed by a decrease, and then a sharp subsequent rise. Linear enhancements in the ultimate moment were observed with increases in both bolt preload and coefficient of friction. Furthermore, the ultimate bending moment showed a gradual increase with the number of bolts. Based on the results, a bending moment-rotation curve model of joints with bolted connection is established, and the expression of each parameter in the model is calculated. This model can be applied to simulation of the bending performance of semi-rigid joints with bolted connection. Full article

The seismic performance of a proposed bolted angle connector beam-to-column joint with a stiffener (hereinafter referred to as a BACS joint) was investigated utilizing quasi-static tests on six specimens with H-shaped steel members. The failure modes, hysteretic curves, skeleton curves, stiffness degradation, and energy dissipation capacity were analyzed. The test results indicated that the BACS joint exhibited a 28.1% higher moment resistance and a 12.6% greater equivalent viscous damping coefficient compared to a welded connection with the same specifications. Furthermore, when compared to a short-beam spliced connection with comparable steel consumption, the BACS joint demonstrated advantages in both the load-bearing capacity and the energy dissipation. The numerical analysis results based on ABAQUS software demonstrated that increasing the stiffener height could not only enhance the bending capacity and stiffness of the connection, but also promote the relocation of the plastic hinge towards the beam end, thereby improving the failure mode. The increase in the stiffener thickness led to a minor improvement in the bending capacity of the connection, yet the influence of the stiffener thickness on the connection stiffness was limited. Furthermore, the use of steel with a higher strength grade could substantially increase the bending capacity of the BACS joint, while the enhancement in stiffness was relatively modest. Therefore, economic considerations should be integrated into the engineering design process. Full article

Titanium alloy TC4 countersunk head bolts (CHB) are widely used in spacecraft structures, but the research on CHB does not receive enough attention at present. There are still some more opportunities worthy of in-depth research, such as insufficient research on CHB of high-strength fasteners for aerospace applications, an insufficient combination of CHB simulation tests with real working conditions, and inspection and testing methods. In this study, through the combination of finite element simulation and experiments, the working conditions of the CHB connection structure bearing tensile load and CHB screwing were analyzed, and the requirements of the CHB connection structure and installation of CHB were optimized. Based on the single-bolt tensile simulation, the working conditions of multi-bolt connection structures under eccentric load and single-bolt composite laminate connection structures under tensile load were analyzed. Meanwhile, the structure of CHB was further optimized, and the simulation analysis model of the CHB tightening process was established. The research shows that the larger fixing bolt countersunk angle θ₁ and the smaller countersunk fillet radius r, the better the ultimate bearing capacity of the connection structure will be. When the countersunk bevel angle of pressure plate θ₂ was greater than or less than 100°, the clamping force–angle slope will decrease, while when θ₂ was smaller, it will have a greater influence on the slope. The coaxiality Φ had little influence on the slope around the allowable tolerance range (0.3 mm), but the influence on the slope becomes greater when it exceeds the tolerance range. The research results provide a reference and basis for the layout of CHB and the use of composite materials in aerospace connection structures. Full article

A novel hydraulically actuated uniform clamping flange connection mechanism is proposed to address the long-standing challenges in high-pressure natural gas flowmeter calibration, including cumbersome bolt-by-bolt assembly/disassembly, high leakage risk, and severe non-uniform gasket contact pressure associated with conventional multi-bolt flanges. Unlike traditional discrete bolt loading, the proposed mechanism generates a continuous and actively adjustable circumferential clamping force via an integrated hydraulic annular piston, ensuring excellent sealing uniformity and rapid installation within minutes. A high-fidelity transient finite element model of the hydraulic clamping flange assembly is established, incorporating the nonlinear compression/rebound behavior of flexible graphite–stainless steel spiral-wound gaskets and one-way fluid–structure interaction under water hammer loading. Parametric studies reveal that reducing the effective clamping area to below 80% of the original design significantly intensifies stress concentration and compromises sealing integrity, while clamping force below 80% or above 120% of the nominal value leads to leakage or component overstress, respectively. Under steady 10 MPa pressurization, the flange exhibits a maximum stress of 150.57 MPa, a minimum gasket contact stress exceeding 30 MPa, and a rotation angle below 1°, demonstrating robust sealing performance. During a severe water hammer event induced by rapid valve closure, the peak flange stress remains acceptable at 140.41 MPa, while the minimum gasket contact stress stays above the critical sealing threshold (38.051 MPa). However, repeated water hammer cycles increase the risk of long-term gasket fatigue. This study introduces, for the first time, a hydraulic uniform-clamping flange solution that dramatically improves sealing reliability, installation efficiency, and operational safety in high-pressure flowmeter calibration and similar temporary high-integrity piping connections, providing crucial technical guidance for field applications. Full article

Laminated bamboo (LB) has shown enough exceptional performance to be used in constructions, but the performance of the bolted connections remains to be explored. To meet the criteria of low-carbon construction and fill the research gap in LB dowel embedment performance, this study examined the longitudinal dowel embedment behavior of LB. Failure modes, load–displacement curves, embedment strength, and elastic foundation parameters were examined after four sets of half-hole specimens with dowel diameters (6, 8, 10, and 12 mm) were tested in accordance with ISO 10984-2. The majority of the data was confirmed to follow a normal distribution by the Kolmogorov–Smirnov test. Interlaminar shear failure (dominant in 10 and 12 mm groups) and local crushing (dominant in 6 and 8 mm groups) were the primary failure modes. There were clear linear and nonlinear phases in the load–displacement curves (excellent ductility). The average elastic foundation modulus was 3565.55 MPa (0.39 times the compressive modulus); meanwhile, the average proportional limit, yield, and ultimate strengths were 35.48, 63.08, and 74.44 MPa (0.59, 1.06, and 1.25 times the parallel-to-grain compressive strength). The ultimate strength varied from 72.64 MPa to 76.71 MPa as the diameter rose; however, the elastic foundation beam coefficient dropped significantly. A novel calculation based on LB’s parallel-to-grain compressive strength accorded well with test results, while the existing code formulae (GB 50005, NDS, and CSA O86) overestimated LB embedment strength. The design of LB bolted connections is guided by this study, which also explains LB embedment criteria and offers design parameters and a prediction method. Full article

In order to ensure the structural safety and serviceability of existing reinforced concrete (RC) structures, there is a compelling need to develop efficient techniques for the rapid replacement of damaged RC beams within strong-column–weak-beam structural systems. This study introduces a novel prefabricated RC beam with welded cover-plate steel sleeve and bolted splice designed to facilitate accelerated replacement and enhance construction efficiency. The proposed beam is connected to cast-in-place RC columns, forming a prefabricated novel prefabricated RC joint with a welded cover-plate steel sleeve and a bolted splice; this configuration contrasts with conventional monolithic RC joints, which are formed by integrally casting beams and columns. The assembly speed of the prefabricated system markedly surpasses that of its cast-in-place counterpart, and the resulting beam–column system is fully demountable. Finite element simulations of the novel prefabricated RC joint with welded cover-plate steel sleeve and bolted splice, performed using ABAQUS, identified the thickness of the welded end-plate as a pivotal parameter influencing the joint’s mechanical behavior. Accordingly, quasi-static tests were carried out on three novel prefabricated RC joints with welded cover-plate steel sleeves and bolted splices and one cast-in-place RC joint, with the welded end-plate thickness serving as the primary test variable. The failure patterns, hysteretic responses, energy dissipation capacity, ductility, and stiffness degradation were systematically analyzed. Experimental findings indicate that increasing the end-plate thickness effectively improves both the peak load-bearing capacity and the ductility of the joint. All prefabricated specimens exhibited fully developed spindle-shaped hysteresis loops, with ductility coefficients ranging from 3.47 to 3.64 and equivalent viscous damping ratios exceeding 0.13. All critical seismic performance metrics either met or exceeded those of the reference cast-in-place RC joint, affirming the reliability and superior behavior of the proposed novel prefabricated RC joints with welded cover-plate steel sleeves. Full article

In order to improve the seismic performance of traditional precast lightweight walls, a new precast concrete wall with beam connection and embedded steel support is proposed in this study. Six 2/3-scale specimens were designed for a quasi-static cyclic loading test, and a numerical study was carried out. Key variables include shear span ratio (0.8–1.6), wall thickness (120–200 mm), concrete strength (C25–C40), and concealed column configuration. The experimental results reveal three distinct failure modes, specifically, brace buckling, weld fracture at the lower joints, and bolt shear failure. The system shows excellent ductility (displacement ductility coefficient μ = 3.2–4.1) and energy dissipation capacity (equivalent viscous damping ratio ξ = 0.28–0.35), and its performance is 30–40% higher than that of traditional reinforced concrete walls and close to that of steel plate shear walls. The shear span ratio is reduced by 50%, the shear bearing capacity is increased by 16%, but the peak displacement is halved, and the peak load of concealed column is increased by 57%. The finite element analysis verified the experimental trends and emphasized that the shear capacity can be increased by 12–18% by widening the steel brace (relative to thickening) under the condition of constant steel volume. The results demonstrate that BIM-driven design is very important for solving connection conflicts and ensuring constructability. Parameter research shows that when the concrete strength is greater than C30, the yield load increases by 15–20%, but the influence on the ultimate bearing capacity is minimal. These findings provide an operational guide for the implementation of high-performance prefabricated walls in earthquake-resistant steel structures, and balance the details of constructability through support, connection, and BIM. Full article

Steel angles connected by bolts have been commonly used in transmission towers. Due to the limited length of steel angles, double-shear splice connections are generally adopted to connect steel angles in main members. The stability of this type of members remains unclear as a result of the presence of discontinuity and is difficult to evaluate using existing design methods. This study presents numerical simulations of steel angles with double-shear splice connections under axial compression. Numerical models are established for discontinuous steel angles and validated against published experimental results. Parameters including splice steel ratio, discontinuity location, slenderness ratio, and width-to-thickness ratio on the axial compression load capacity of steel angles are evaluated. A design equation is proposed based on numerical results to quantify the axial load capacity of discontinuous steel angles. Comparisons with experimental data and values calculated using Chinese design code demonstrate that the proposed equation can predict the ultimate load capacity of discontinuity steel angles with better accuracy than the design method in the Chinese code. Finally, a design equation is further simplified by eliminating the effect of parameters with limited influence on ultimate load under axial compression. Full article

This article presents a novel procedure for detecting, locating, and quantifying damage caused by a loose bolted joint in a modular plate structure. The primary aims of this work are to locate the loose joint with a minimum number of measurement points and to quantify the damage based on acquired modal data. The proposed method is based on the direct correlation of patterns of modal property changes using simulated and measured data. These patterns combine the relative shifts in natural frequencies and the norms of relative changes in mode shapes, derived from a pre-computed database of finite element method (FEM) simulations for various potential damage scenarios. The experimental validation demonstrates that the procedure can effectively and accurately locate the position of a loose joint using only five accelerometers. A foundational study on damage quantification is presented through a sensitivity analysis using FEM model data on a single connection plate of the test structure. The results demonstrate the nonlinear relationship between the damage state and natural frequency change, based on the mode shape, mode number, and the location of the damage. Full article

The seismic design of aluminum alloy structures requires specific attention due to the material’s distinct mechanical properties compared to steel, which renders direct application of steel joint design methods inappropriate. This study investigates the seismic behavior of T-shaped aluminum alloy beam–column bolted connections, which consist of 6061-T6 aluminum alloy beams and columns connected by S304 stainless steel connectors via high-strength bolts. A finite element model, incorporating a mixed hardening constitutive model for accurate cyclic response, is established and validated against low-cycle cyclic loading tests. Parametric analyses evaluated the influence of L-shaped connector dimensions on hysteresis response, skeleton curves, stiffness degradation, energy dissipation, and ductility. Results demonstrate that increasing the thickness of the short leg of the L-shaped connector between the beam flange and column flange significantly enhances the ultimate bending moment, with an increase of up to 36.7% per 2 mm increment, alongside improved energy dissipation and ductility. Stiffness degradation follows a natural exponential decay, with residual stiffness between 23.85% and 32.57% at ultimate deformation. An efficiency analysis identifies the most cost-effective measures for seismic design. The primary novelty of this work lies in the successful application and validation of a mixed hardening model for simulating the complex cyclic behavior of T-shaped aluminum alloy connections, coupled with a systematic efficiency-oriented parametric study. The findings offer practical, quantitative guidelines for designing aluminum alloy bolted connections in seismic-prone regions. Full article