Search Results (150)

Steel moment-resisting frames are widely used in seismic regions, but conventional beam–column connections often suffer from concentrated damage and difficult post-earthquake repair. To address these issues, this study proposes a novel replaceable energy-dissipating slit beam–column joint for steel frames. To enhance structural energy dissipation efficiency, mitigate seismic damage, and enable rapid post-earthquake repair, the joint utilizes connectors as energy-dissipating elements such that plastic deformation is confined to these connectors while main beams and columns remain elastic throughout the loading history. A quasi-static test was conducted on the proposed joint. The test results indicate that the hysteresis loops are full and fusiform, demonstrating excellent energy dissipation capacity. The joint exhibits ductility coefficients of 6.30 and 5.27 under positive and negative loading, respectively, and the equivalent viscous damping coefficient remains above 0.30 after a rotation of 0.025 rad. Furthermore, plastic damage is primarily sustained by the connectors, with no evident yielding observed in other structural members. To further investigate the joint, it was applied to a three-story, four-bay, three-span steel frame for finite element analyses. Compared with a conventional rigid joint frame, the proposed joint frame under rare earthquakes reduces roof displacements by 20.97% (with the X-direction as the primary direction) and 16.23% (with the Y-direction as the primary direction), and maximum interstory drift ratios by 18.06% (with the X-direction as the primary direction) and 15.55% (with the Y-direction as the primary direction), while satisfying the code-specified limits of 1/250 for elastic and 1/50 for elastoplastic interstory drift ratios, thereby indicating its superior seismic performance. Full article

Inclined extended end-plate beam-to-beam connections are commonly used as kink joints in steel polygonal portal frames, yet their mechanical behaviour is not fully represented by the assumptions of the Eurocode 3 component method. This study investigates the influence of member inclination on stress redistribution within the end plate and the resulting bolt-row activation under bending. Predictions obtained using the Eurocode 3 component method are compared with nonlinear component-based finite-element analyses (CBFEM), and a parametric study is conducted to evaluate the effects of transverse bolt spacing and bolt-row arrangement on moment resistance and force distribution. The results show that member inclination induces a moment-dependent redistribution of tensile and compressive stresses within the end plate, enlarging the tensile region and activating additional bolt rows beyond those considered in the conventional component method. Consequently, tensile forces are redistributed among a greater number of bolt rows, leading to differences between analytical and numerical predictions of the resisting mechanism. The analyses also show that transverse bolt spacing influences not only local T-stub behaviour but also the global redistribution capacity of the end plate. Furthermore, conventional three-row layouts exhibit a distributed 2+2+1 resisting mechanism while maintaining bending resistance within approximately 4% of the reference configuration. These findings provide a mechanical interpretation of bolt-row activation in inclined joints and contribute to improving the understanding of the limitations of simplified analytical design approaches. Full article

Although the traditional approach in building engineering is to keep the main wind force resisting system elastic, doing so can inhibit capacity-based seismic design, and it is not always the most cost-effective approach. The purpose of this study is to determine the wind collapse capacity of a three-story building with ductile steel moment frames compared to nonductile moment frames for a range of design wind speeds. To incorporate the potential for inelasticity, the ductile steel moment frames are designed using reduced main wind force resisting system loads. The nonductile moment frames, which are not specifically detailed to be ductile, are designed using unreduced loads. Nonlinear pushover analysis of finite element models is used to determine static system overstrength and collapse mechanisms based on an open country terrain. Nonlinear incremental dynamic analysis is used to determine collapse safety. The results show that both ductile and nonductile steel moment frames have adequate wind collapse capacity, but the ductile moment frames have 42% higher system overstrength, on average, compared to nonductile steel moment frames for the same design loads, and greater collapse margin ratios compared to nonductile steel moment frames. The findings suggest that limited inelasticity in a ductile steel moment frame system may be acceptable if the frame meets drift requirements. Full article

Glass fiber-reinforced polymer (GFRP) is increasingly used in civil engineering because of its high strength-to-weight ratio, corrosion resistance, durability, and low maintenance requirements. However, its inherently brittle behavior and limited ductility restrict its application in seismic regions due to poor energy dissipation capacity. To address this limitation, this study proposes a novel hybrid system comprising pultruded GFRP profiles and a replaceable steel link with ductile pipe sections. The pipe element confines inelastic deformation to the steel components while keeping the GFRP members elastic. Numerical results demonstrate stable hysteretic behavior with no significant degradation in strength or stiffness, confirming the effectiveness of the proposed system. Also, increasing the ratio of the pipe thickness to the flange thickness of the steel link (β) ensures suitable performance provided that plastic hinge formation remains confined to the ductile pipe element and replaceable steel link. Adding the pipe element to the I-shaped steel link increases web stress when β ≤ 1.0 (leading to web yielding), while stresses in the flange, GFRP beam, and GFRP columns are reduced by 46–51%, 17–60%, and 15–40%, respectively. However, for β > 1.0, stresses in GFRP components are not reduced but slightly increase by 1–9% (negligible), making β > 1.0 not recommended. Also, by changing the $\beta =0.50$ to $0.75$, $1.00$, $1.25$, and $1.50$, the flexural capacity, stiffness, and energy dissipation are enhanced by 1.51 times to 2.46 times, 1.18 times to 1.38 times, and 1.35 times to 1.68 times, respectively. Finally, the necessary design equations for the proposed system are presented. Full article

This paper aims to systematically investigate the out-of-plane yield performance, structural reliability, and sensitivity boundaries of minor-axis joints under construction overloads. To achieve this objective, a high-fidelity three-dimensional non-linear finite element framework incorporates precise solid continuum elements, contact non-linearities, and multi-linear material models, which is successfully validated against referenced experimental curves. Utilizing efficient Latin Hypercube Sampling integrated with response surface surrogate methodologies, a comprehensive stochastic parametric scanning is conducted to map the multi-dimensional scatter profiles and probabilistic capacity responses at targeted elastic thresholds. Furthermore, based on the upper-bound theorem of plasticity, closed-form analytical formulations defining the competition between independent and global plastic mechanisms are established and rigorously validated against extensive numerical parametric matrices. The core mechanical insights demonstrate that the column web thickness t_w and column section depth b overwhelmingly dictate nearly 60% of the joint’s elastic-limit resistance by directly defining the out-of-plane bending span. While the divergence between the two competitive plastic mechanisms remains minute under severe flange constraints, the research uncovers a critical localized interaction: in connections with a relatively thick t_w, the extended endplate thickness t_ep and endplate flexibility trigger a dynamic migration of the rotation axis between the longitudinal boundaries L₀ and L_a, significantly shortening the effective internal lever arm. For practical design applications, calibrating these formulations with a partial safety factor γ_M = 1.25 successfully establishes a dependable lower-bound design strength, providing a verified safety red-line for temporary cantilevered scaffolding installations. Full article

Semi-rigid connections play a critical role in steel structures; however, most existing component-based approaches do not explicitly account for stiffness degradation and post-yield residual stiffness, which may reduce the accuracy of moment–rotation predictions. To address this limitation, direct numerical simulations (DNSs) of representative T-stub beam-to-column joints were conducted to investigate their nonlinear rotational behavior. Based on the observed joint response, a Joint Component Model (JCM) capable of representing sequential yielding, stiffness evolution, and residual rotational stiffness was developed. Constitutive relationships were derived, and a parameter identification procedure directly relating joint geometry and component mechanical properties to the model parameters was established. The proposed model was subsequently implemented in ANSYS and validated through analyses of T-stub joints and steel frames subjected to static and dynamic loading. The results showed good agreement between the JCM and DNS in terms of moment–rotation relationships, force–displacement responses, and dynamic time-history responses. Compared with DNS, the proposed model significantly reduced computational time while maintaining satisfactory prediction accuracy. The proposed JCM therefore provides an efficient and reliable component-based modeling framework for modeling semi-rigid steel connections and capturing stiffness evolution throughout the entire joint rotation process. Full article

The quest for seismic resiliency requires designing for performance objectives beyond life safety. Functional recovery is an emerging objective often defined as the time required to restore a building’s basic functionality to the pre-event level. Nevertheless, quantifying functional recovery is a complex, computationally intensive process that is challenging to integrate into a standard design workflow. This study develops a machine learning (ML) model to map design and geometric features of steel special moment-resisting frames (SMRFs) to their functional recovery under two hazard levels: design-basis (DBE) and maximum considered (MCE) earthquakes. First, functional recovery time was quantified for an inventory of 100 steel SMRFs with varying heights by integrating FEMA P-58 loss-based methodology with the ATC-138 framework. The building information and calculated recovery times were then used in a standard ML pipeline including feature selection, hyperparameter tuning, cross-validation, model evaluation, and model explainability. The results suggest that the ML model can accurately estimate functional recovery using design and geometric features, achieving R² values of 89% and 93% on the test set for DBE and MCE levels, respectively. In addition, for the studied regular SMRF buildings, the results indicate that building weight and the average strong-column weak-beam ratio are influential design parameters that govern functional recovery time, suggesting that a recovery-oriented design of steel SMRFs may benefit from minimizing building weight and avoiding overt column upsizing. 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 develops collapse fragility curves for a representative steel moment-resisting frame building exposed to idealized tsunami-loading scenarios, explicitly incorporating shoreline distance as an organizing spatial variable. Nonlinear static analyses are performed in SeismoStruct for braced and unbraced configurations, using the maximum interstory drift ratio as the engineering demand parameter. Drift-based damage states are defined according to ASCE 41-23 and FEMA 356 to interpret damage progression, while the probabilistic formulation focuses on the collapse limit state using a lognormal model with total dispersion based on FEMA P695. Triangular and rectangular tsunami-load distributions are considered to assess the influence of load-pattern assumptions. The braced model remains below global collapse within the analyzed intensity range and is retained as a comparative case, whereas the unbraced model reaches global instability and provides the collapse-response information used to construct the fragility curves. The median collapse inundation depth is approximately 14.1 m for the triangular distribution and 11.7 m for the rectangular distribution, corresponding to shoreline distances of approximately 97.5 m and 157.5 m, respectively. The results suggest that shoreline distance can support a spatial interpretation of collapse vulnerability for preliminary coastal-risk assessment, provided that the idealized and site-dependent nature of the adopted distance–depth–velocity scenarios is properly recognized. Full article

Steel moment-resisting frames exhibiting vertical geometric irregularities, particularly those with setback configurations, experience increased seismic demands due to stiffness discontinuities and complex dynamic interactions. These conditions present significant challenges for conventional vibration control strategies. This study introduces a performance-based optimization framework that utilizes the Circle-Inspired Optimization Algorithm (CIOA) to enhance the design of tuned liquid dampers (TLDs) in irregular steel structures. Structural responses are simulated in OpenSees, with a rheological model based on the Housner method employed to accurately capture fluid–structure interaction. Seismic performance is evaluated using a suite of real subduction-type ground motions, selected to represent the seismic hazard level of Armenia, Colombia, in accordance with the Conditional Scenario Spectra (CSS) methodology and the National Seismic Risk Model for Colombia. The optimization process considers the mean response across multiple ground-motion records to ensure robustness against seismic variability. Multiple time-domain objective functions are examined, including peak interstory drift, maximum displacement, and peak acceleration. The results indicate that objective functions related to interstory drift and displacement provide the most effective, stable, and consistent reductions in seismic demand across all scenarios, while acceleration-based objectives display greater sensitivity to record-to-record variability. These outcomes underscore the importance of objective function selection in determining both optimization stability and control effectiveness. The CIOA demonstrates rapid convergence, numerical robustness, and reliable performance, confirming its suitability as a computationally efficient and resilient optimization tool for the design of passive control systems in irregular steel structures exposed to high seismic hazard. Full article

This article investigates the response of an unprotected three-storey steel moment-resisting frame subjected to a suite of horizontally traveling fire scenarios. A series of multi-step finite-element simulations was conducted to analyze the impact of traveling fires on both the global and local responses of a low-rise building frame. The research considers a range of fire types, both uniform and spatially varying, as well as different locations, and sizes to capture a diverse array of fire scenarios. Non-uniform compartment fires are modeled using the improved traveling fire method (iTFM), while uniform fires are simulated using the Eurocode parametric (EC) fire model. Four traveling fire scenarios with floor area coverage ranging from 5% to 48% are examined. The resulting deformation patterns, along with bending moment and axial force distributions in critical beam and column sections within the fire compartments, are thoroughly evaluated. The findings reveal that, within the case study frame and the range of parametric analyses, a uniform compartment fire does not necessarily yield the worst-case scenario commonly assumed in design codes. Instead, global and local structural responses are primarily influenced by traveling fire scenarios. Full article

This study investigates the influence of out-of-plane beam skew on the cyclic performance of column-tree steel moment connections. Utilizing validated finite element (FE) models against experimental data, the cyclic responses of various configurations were evaluated under the AISC cyclic loading protocol up to a story drift ratio of 0.05 rad. Skew angles of 0°, 10°, 20°, and 30° were examined across three representative beam depths. The results demonstrate that all configurations satisfy the AISC 341 acceptance criteria for Special Moment Frames (SMFs), maintaining at least 80% of the plastic moment capacity (0.8 M_p) up to a 0.04 rad story drift ratio. However, the introduction of beam skew resulted in a gradual reduction in energy dissipation capacity, with the total dissipated energy decreasing by 2.9–8.9% at a 30° skew. Notably, the inelastic energy component was more sensitive to the skew than the frictional components, exhibiting a maximum reduction of 15.4%. While out-of-plane skew disrupted the symmetry of stress triaxiality and plastic strain at the beam-to-column interface, the overall fracture susceptibility was not significantly exacerbated up to 30°. Furthermore, column twisting remained within a negligible range (below 0.5°), and its impact on global stability was limited. Despite the general stability, a premature bolted splice failure was observed in deep beam configurations at a 30° skew during the 0.05 rad drift cycles. Based on these findings, it is concluded that column-tree connections with an out-of-plane skew up to 30° are viable; however, a design limit of 20° is recommended for deep beam configurations to ensure structural integrity under extreme cyclic demands. Full article

Beam-to-column connections govern both seismic performance and post-earthquake repairability of steel moment-resisting frames. Yet direct, apples-to-apples comparisons among welded, bolted, and repair-oriented replaceable-fuse moment connections are still scarce, which hinders rational selection for resilient construction. This study conducts a unified finite-element comparison of three representative joint archetypes—W-RBS, Bolted, and Prefab-web-fuse—under monotonic and cyclic loading. Consistent moment-rotation definitions are adopted, and normalized indices are introduced to compare hysteresis shape, degradation, and energy dissipation across joint concepts with different strength scales. Component-wise plastic dissipation is also extracted to quantify damage localization and assess main-frame protection and replaceability. Results reveal clear trade-offs: W-RBS provides the highest strength and dissipation but degrades most in stiffness; the bolted joint shows pinching due to interface compliance; and the web-fuse concept concentrates inelastic demand in a replaceable segment, supporting repairability-oriented design. The proposed framework offers mechanism-based guidance for selecting steel moment connections toward resilient and repairable frames. Full article

The use of a corrugated steel plate shear wall (CSPSW) lateral load-bearing system in a steel moment frame (SMF) significantly increases the system’s energy absorption and stiffness. However, the design of CSPSWs involves many parameters and details that greatly increase the complexity of the structure’s response. This study aims to evaluate the effectiveness of the geometric parameters of this system using modern optimization algorithms and an alternative mathematical technique, Response Surface Methodology (RSM). Five geometric parameters, namely crest width (a), diagonal section width (b), corrugation depth (c), sheet thickness (t), and aspect ratio of plate dimension (d), were analyzed to improve the performance of CSPSWs. Design of experiments (DOE) was performed using Design-Expert software, and the required response surface methodology models were designed based on the dimensions of the five variables. Structure weight per meter reduction was set as the optimization goal of the problem. The problem constraints were also defined based on an increase in load-bearing capacity and a reduction in the equivalent plastic strain (PEEQ) percentage in three safety levels 80%, 85% and 90%. Subsequently, the alternative equations developed by RSM to define the objective function and nonlinear constraints were also optimized using modern algorithms in MATLAB 2015. Results revealed a coefficient of determination (R²) of 0.9995 between the experimental and numerical findings and a 1% error between the values obtained from the optimization and reanalysis of the finite elements. Also, they showed an increase in the frame’s lateral load-bearing capacity with the CSPSW, along with a reduction in weight. Full article

Top-and-seat angle connections (TSACs) exhibit inherently asymmetric and nonlinear moment–rotation behavior, which can significantly influence the global response of steel frames subjected to combined gravity and lateral loading. In this study, a three-dimensional finite element model of an unstiffened TSAC is developed and validated against experimental moment–rotation data from the literature under monotonic loading conditions. The validated model is then used to investigate the influence of key geometric parameters, including top angle thickness, bolt diameter, and beam depth, on the connection’s moment–rotation response in both positive and negative bending directions. Subsequently, the monotonic connection behavior is incorporated into nonlinear static analyses of steel portal frames to examine the effects of asymmetric connection response and moment reversal on frame-level stiffness degradation and capacity. A practical SAP2000 modeling workflow is proposed in which the finite element-derived monotonic moment–rotation curves are implemented using zero-length rotational link elements, allowing combined consideration of material, geometric, and connection nonlinearities at the structural level. The comparisons between Abaqus and SAP2000 results demonstrate consistent frame-level responses when identical monotonic connection characteristics are employed, highlighting the ability of the proposed workflow to reproduce detailed finite element predictions at the structural analysis level. The results indicate that increasing top angle thickness, bolt diameter, and beam depth enhances the lateral stiffness and base shear resistance of steel frames. Positive and negative bending directions are defined consistently with the applied gravity-plus-lateral loading sequence. Full article