Search Results (45)

To enhance the seismic performance of existing reinforced concrete (RC) buildings during retrofitting, the study introduces a new type of joint connected by a T-shaped steel plate. Compared with previous similar strengthening methods, this novel structure incorporating a post-installed beam not only effectively improves the mechanical properties of RC columns, but the connectors also further enhance the integrity of the post-installed beam. Low-cycle reversed loading tests on one cast-in-place specimen (RC) and three T-shaped steel plate connection specimens (TRC1–TRC3) were conducted to evaluate failure modes, hysteresis and skeleton curves, and energy dissipation. Results show that the novel joint failure concentrates at beam-end–column steel jacket weld seams and column-side steel plate cracking, while the core-zone concrete remains intact. Compared with RC, the novel joints TRC1–TRC3 exhibit bearing capacity variations of −1.03%~+15.80% and significantly enhanced energy dissipation. The thickness of the beam’s wrapped steel improves the carrying capacity and energy dissipation, whereas the T-shaped connector thickness has limited influence on bearing capacity. ABAQUS parametric analysis indicates that bolt quantity, concrete strength, and connector thickness have limited influence and serve as secondary design factors. These findings provide a theoretical basis for retrofitting existing buildings. Full article

A critical research gap persists in modular steel construction regarding the seismic behavior of inter-module connections between square steel tubular columns and H-shaped steel beams. While numerous connection systems have been proposed, two fundamental challenges remain unresolved: the inherent conflict between construction efficiency and mechanical performance, and the insufficiency of restoring force models that systematically describe hysteretic characteristics and stiffness degradation under cyclic loading. To address these issues, a novel box-type modular connection between square steel tubular columns and H-shaped steel beams is proposed. A finite element model was established using ABAQUS, and the modeling methodology was validated against experimental results from the literature. The seismic behavior was systematically investigated, and a restoring force model with theoretical saturation and linear degradation was developed. Results show that the novel joint is a semi-rigid connection that satisfies the “strong column–weak beam” design principle. The outer ring plate shifts the plastic hinge away from the vulnerable beam end region, preventing failure at the beam–column connection. Among the detrimental factors identified, the insert-to-column gap has the most severe impact, causing up to a 49.5% reduction in energy dissipation and a 6.5% reduction in initial stiffness; the outer ring plate thickness below the beam flange thickness causes a 44.6% drop in energy dissipation. The proposed restoring force model, validated against nine calibration specimens and one independent specimen, predicts peak load with a deviation of only 1.14% and the equivalent viscous damping coefficient with a relative error of 14.7%, confirming its reliability in capturing the cyclic behavior of the joint. This study provides both design recommendations for engineering practice and a theoretical foundation for elasto-plastic analysis of modular frames with this connection type. Full article

To investigate the feasibility and effectiveness of seismic repair for prefabricated single-beam column joints in modern Chinese traditional-style buildings (MCTBs), low-cycle reversed loading tests were conducted on two original joints with different T-stub web thicknesses and one repaired joint. A repair strategy was proposed in which damaged T-stub connectors were removed and replaced with welded end-plate connections. The seismic behavior of the joints, including failure mode, hysteretic response, skeleton curve, stiffness degradation, ductility, energy dissipation capacity, and seismic performance comparison between the original and repaired joints, was systematically evaluated. In addition, a refined finite element model was established using ABAQUS and validated against the experimental results to investigate the stress distribution, deformation characteristics, and load-transfer mechanism of the joints. The results indicate that damage in the original joints was mainly concentrated in the T-stub connection region, while the beam and column members remained essentially intact, demonstrating an effective damage-control mechanism. Increasing the T-stub web thickness improved the load-carrying capacity, stiffness, and ductility of the joints. After repair, the load-transfer mechanism changed from a blind-bolted T-stub connection to a welded end-plate connection, resulting in a different damage evolution pattern and failure mode. Nevertheless, the repaired joint exhibited stable hysteretic behavior, satisfactory deformation capacity, and favorable energy dissipation performance. Compared with the original joint, the repaired specimen achieved a moment capacity comparison ratio of approximately 116%, stiffness comparison ratios exceeding 120%, and an energy dissipation comparison ratio of approximately 148%. The finite element results agreed well with the experimental observations and further revealed the evolution of stress concentration regions and load-transfer paths before and after repair. The present experimental results demonstrate the feasibility of the proposed repair method for rehabilitating damaged joints while maintaining satisfactory seismic performance without replacing the primary beam and column members. The proposed repair strategy therefore provides a practical and efficient solution for the post-earthquake rehabilitation of prefabricated joints in MCTBs. Full article

This review synthesizes findings from more than 100 journal articles, reports, and design standards on the design, simulation, and testing of steel beam-to-column connections, with emphasis on semi-rigid bolted extended end-plate (EEP) joints. The core objective of this study is to highlight the critical importance of accurately capturing this semi-rigid behavior, given the significant implications of improper modeling for the global response, safety, and design reliability of steel frames. While connections are often idealized as fully rigid or pinned, EEP connections typically exhibit a semi-rigid response governed by nonlinear moment–rotation (M–θ) behavior. The reviewed literature is organized around: (i) mechanical response and key failure mechanisms (end-plate yielding, bolt fracture, and prying action); (ii) analytical and numerical prediction methods, including component-based models and finite-element approaches capable of representing contact, bolt pretension, and cyclic degradation; and (iii) system-level implications for steel frames. Approaches used in major standards (AISC and Eurocode 3) for classifying connection stiffness and strength are compared, and experimental programs are summarized to identify the dominant parameters controlling resistance, ductility, and failure mode. Translating these component-level findings to the structural-system level, the review highlights how appropriately detailed semi-rigid EEP connections can enable moment redistribution, reduce member demands, and support stable inelastic deformation under seismic actions. Key research gaps include three-dimensional and multiaxial loading, impact and other high-rate actions, and the performance of alternative materials such as stainless steel. Full article

This study proposes a design method for a novel bolted endplate rigid connection between circular concrete-filled steel tube (CCFT) columns and wide-flange (WF) steel beams, with particular emphasis on the parametric behavior governing joint performance. Based on the preliminary quasi-static tests, finite element simulations are conducted to evaluate the flexural behavior and failure mechanisms under beam-end maximum moment, followed by an extensive parametric study examining the effects of square tube dimensions, high-strength grout, and column axial load. The numerical results show that the wall thickness of the square steel tube significantly affects grout indentation. A 60% reduction in wall thickness led to a 503% increase in indentation. In contrast, variations in tube dimensions, grout strength, and column axial load within the studied range caused less than a 16% change and did not influence the flexural performance. These results indicate that the constraints on tube dimensions and axial load may be relaxed. The proposed connection effectively overcomes the limitations of conventional CCFT-to-beam joints, including unfavorable stress transfer, complex detailing, and construction inefficiency, by modifying the load-transfer mechanism and reducing the demand on tensile-critical welds, thereby enhancing ductility. Based on the parametric findings, a design method is established, and theoretical analysis confirms that the proposed connection satisfies the stiffness requirements for fully rigid connections. Future quasi-static tests with different member sizes are recommended to validate these findings. Full article

In the modular construction of liquefied natural gas (LNG) plants and receiving terminals, transport beams are critical components that enable modular mobility. However, these beams are susceptible to large deformations due to complex loads during land and sea transportation. Traditional monitoring methods (i.e., strain gauge and deflection meters) often suffer from low efficiency and poor accuracy and may disrupt operational continuity in real-time monitoring systems. This paper presents a non-contact, real-time deformation detection system for LNG modular transport beams based on digital image technology, which integrates a high-resolution camera with a real-time software framework to remotely monitor structural integrity. An experiment was conducted on a full-scale support column-transport beam frame with specialized connection joints designed for rapid assembly. Five digital image correlation (DIC) detection regions (5 cm × 5 cm) were established on box-shaped beam sleeves, column sleeves, and the end plates of the beam–column joints. In addition, displacement gauges were installed at the same DIC locations. The experimental results demonstrate that the DIC measurements show good agreement with traditional measurement methods, verifying the applicability of the proposed system for large-scale LNG engineering structures. Full article

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

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

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

This study uses the finite element (FE) software ABAQUS V 6.14to develop detailed, comprehensive numerical models of the behaviour of restrained structural subassemblies of corrugated web steel beams (SBCW) connected to concrete-filled tubular columns (CFTC) via reverse channel connection. Four different types of web corrugation profiles—trapezoidal (Trap), rectangular (Rec), sinusoidal (Sin), and triangular (Tria)—are numerically modelled and analyzed to evaluate the significance of their influence on structural behaviour. In addition, the effects of flange stiffeners at the point load and web slenderness are examined. Moreover, this study investigates the effects of using four different joint types of reverse channel connection: extended endplate, flush endplate, flexible endplate, and hybrid extended/flexible endplate on the behaviour of SBCW. It is concluded that, by means of corrugated webs for enhancing beam deformation capacity and strength, it is feasible for the beams to achieve a higher load-carrying capacity. The ultimate load of the beams with Trap and Rec corrugated web was higher than that for the flat web beam by about 22% and 18%, respectively, and with the same increase of 10.5% for Tria and Sin corrugation profiles. However, providing the corrugated web beams with flange stiffeners at the point load had a limited effect (+0.7% to +5.1% depending on profile). Moreover, increasing the web thickness to reduce the slenderness ratio (hw/tw) from 250 to 200 can be an effective solution to prolong their load-carrying capacity. In addition, using an extended or flush endplate gave the best behaviour of SBCW connected to concrete-filled tubular columns (CFTC) with an increase of (5.3–31.7%) and (25–30.9%) for flush endplate and extended endplate, respectively, compared to flexible endplate, depending on the web corrugation profile. Full article

To investigate the initial rotational stiffness and ultimate moment of fully bolted connections in panelized steel modular structures, a finite element analysis was carried out on 20 joint models. High-fidelity models were developed using ABAQUS, and their accuracy was confirmed through comparison with experimental tests. A parametric study was performed to systematically evaluate the effects of the column wall thickness in the core zone, internal diaphragm configurations, angle steel thickness, and stiffener layouts on the joint stiffness and ultimate strength, leading to practical optimization suggestions. Additionally, a mechanical model and a corresponding formula for predicting the initial rotational stiffness of the joints were proposed based on the component method in Eurocode EC3. The model was validated against the finite element results, showing good reliability. Three failure modes were identified as follows: buckling deformation of the beam flange, buckling deformation of the column flange, and deformation of the joint panel zone. In joints with a weak core zone, both the use of internal diaphragms and increased column wall thickness effectively improved the initial rotational stiffness and ultimate bearing capacity. For joints with weak angle steel connections, adding stiffeners or increasing the limb thickness significantly enhanced both the stiffness and capacity. The diameter of bolts in the endplate-to-column flange connection was found to have a considerable effect on the initial rotational stiffness, but minimal impact on the ultimate strength. This study offers a theoretical foundation for the engineering application of panelized steel modular structural joints. Full article

Sixteen beam–column joints with different column types and connection configurations were designed and tested to identify suitable joints for low-rise prefabricated square steel tube (SST) columns and H-beams. The columns included hollow square steel tube (HSST) and concrete-filled square steel tube (CFSST) types, while the joints consisted of welded, end plate, flange-connected, and angle connector plate configurations. Cyclic loading tests were conducted to examine failure modes, hysteresis and skeleton curves, stiffness degradation, and cumulative energy dissipation. The results showed that joints with angle connector plates outperformed welded, end-plate, and flange-connected joints. The height of the triangular stiffener was found to be a critical factor, with a 144 mm stiffener increasing the ultimate bending moment by 78.65% for CFSST and 79.3% for HSST columns, along with notable improvements in stiffness and energy dissipation. Based on Eurocode 3, angle connector plate joints with high stiffeners were classified as semi-rigid and full-strength. A combined assessment of mechanical behavior and economic efficiency indicated that this joint type provides the highest cost-effectiveness and significant application potential. Full article

To reduce the weight of prefabricated cap beams, a new type of hybrid pier with a steel cap beam and single concrete column with an innovative flange–rebar–ultra-high-performance concrete (UHPC) connection structure is proposed in this paper. Focusing on the static performance of hybrid piers, a specimen with a geometric similarity ratio of 1:4 was fabricated for testing. The results showed that the ultimate load-bearing capacity reached 960 kN, and the failure mode was characterized by an obvious overall vertical displacement of 70.2 mm at the cantilever end, accompanied by local buckling in the webs between transversal diaphragms and ribs. Due to the varying-thickness design, longitudinal strains were comparable between the middle section (thin plates) and the root section (thick plates) of the cantilever beam, showing a trend of an initial increase followed by a decrease from the end of the cantilever beam to the road centerline. Meanwhile, the cross-sections of the connection joint and concrete column transformed from overall compression to eccentric compression during the test. At the ultimate state, their steel structures remained elastic, with no obvious damage in the concrete or UHPC, verifying good load-bearing capacity. Furthermore, the finite element analysis showed the new connection joint and construction method of hinged-to-rigid could reduce the column top concrete compressive stress by 18–54%, tensile stress by 11–68%, and steel cap beam Mises stress by 10%. Finally, based on the experimental and numerical studies, the safety reserve coefficient of the new hybrid pier was over 2.7. Full article

The design of steel connections presents considerable complexity due to their inherently nonlinear behavior, cost constraints, and the necessity to comply with structural design codes. These factors highlight the need for advanced computational algorithms to identify optimal solutions. In this study, a comprehensive computational framework is presented in which the finite element method (FEM) is integrated with a genetic algorithm (GA) to optimize material usage in bolted steel end-plate joints, while structural safety is ensured based on multiple performance criteria. By incorporating both material and geometric nonlinearities, the mechanical response of the connections is accurately captured. The proposed approach is applied to a representative beam-to-column assembly, with numerical results verified against experimental data. By employing the framework, an optimized layout is obtained, yielding a $10.4\%$ improvement in the overall performance objective compared to the best-performing validated model and a $39.3\%$ reduction in material volume relative to the most efficient feasible alternative. Furthermore, a $53.6\%$ decrease in equivalent plastic strain is achieved compared to the configuration exhibiting the highest level of inelastic deformation. These findings demonstrate that the developed method is capable of enhancing design efficiency and precision, underscoring the potential of advanced computational tools in structural engineering applications. Full article

A novel endplate bolted rigid joint is proposed in this study for connecting circular concrete-filled steel tube (CCFT) columns to wide-flange (WF) steel beams. The seismic performance and potential failure mechanisms of the proposed joint were investigated through quasi-static cyclic tests and finite element (FE) simulations. This study aims to address several engineering challenges commonly observed in existing joint configurations, including an irrational force-resisting mechanism, complicated detailing and installation, on-site construction difficulties, constraints on beam size, and limited repairability. By optimizing the force transfer path, the new joint effectively reduces the number of critical tension welds, thereby enhancing the ductility and reliability. The experimental results indicate that the joint exhibits adequate flexural strength, stiffness, and ductility, with stable moment–rotation hysteresis loops under cyclic loading. Moreover, full restoration of the joint can be achieved by replacing only the steel beam and endplate, facilitating post-earthquake repair. FE analysis reveals that, under the ultimate bending moment at the beam end, multiple through cracks develop in the high-strength grout—which serves as a key load-transferring component—and significant debonding occurs between the grout and the surrounding steel members. However, due to confinement from adjacent components, these internal cracks do not compromise the overall strength and stiffness of the joint. This research provides an efficient and practical connection solution, along with valuable experimental insights, for the application of CCFT columns in moment-resisting frames located in high seismic zones. Full article