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Abstract This research study presents an investigation of the structural behaviour and local web buckling resistance of single-coped beam connections with slender web. Single-coped beams with slender web (SBSWs) can be used in long-span structures where the top flange of the beam is removed to provide clearance to connect the beam to the main girder. Eleven (11) full-scale tests of single-coped beam connections with slender web were carried out. In general, all the test specimens failed by local web buckling. It was observed that the ultimate connection resistance was decreased with increasing web slenderness ratio, cope length and cope depth. However, the slender web with significant cope length and cope depth could promote evident post-buckling strength for the connection. Finite element (FE) analyses were subsequently conducted to provide further understandings of the test results. The FE analysis results matched the test data reasonably, and the influences of the test parameters on the performance and ultimate resistance of the test connections were carefully studied. The FE results indicated that the ultimate resistances of the models with high web slenderness were insensitive to initial imperfection amplitude, and such trend was more pronounced for cases with large cope length and depth. Based on the test results, the current design methods for predicting the local web buckling resistance of single-coped beam connections were revisited. In general, overly conservative estimates were obtained using the available design guidelines for quantifying the ultimate connection resistance of the test connections with slender web. Highlights • Structural behaviour of single-coped beam connections with slender web is examined. • Eleven full-scale tests are conducted. • The cascading effect between the slender web and the cope detail is evident. • The adequacy of the current design equations is evaluated. [ABSTRACT FROM AUTHOR]

This paper reported an experimental and numerical study of a novel brace-type hybrid damper composed of steel slit plates enhanced by the friction mechanism. A test programme including six proof-of-concept specimens was carried out. The test results showed that the specimens exhibited multiple yielding stages, and the hysteretic response curves of the specimens were dependent on geometric configurations of the steel slit plates and the clamping force of bolts. The expected energy dissipation sequence accompanied by excellent ductility of the novel hybrid damper specimens was confirmed. The ploughing effect phenomenon between the friction interfaces as evidenced by the wear of the steel plates and increasing friction force was confirmed, which contributed to enhanced friction energy dissipation of the dampers under cyclic loadings. Then, a numerical investigation was conducted to take insights into the resisting mechanism of the specimens. The adequacy of the finite element modelling techniques was justified by a good correlation between test responses and numerical simulations. The test and numerical studies demonstrated that the energy dissipation sequence as a result of the hybrid energy dissipation mechanism contributed to improving the energy dissipation capacity and ductility of the steel slit plates. To facilitate the practical design of the novel hybrid dampers, a theoretical prediction model enabling quantification of critical mechanical quantities of the novel hybrid damper was developed, and the sufficiency of the design model was justified by comparison among the test responses, numerical results, and design predictions. • A novel brace-type hybrid damper composed of steel slit plates enhanced by the friction mechanism was proposed. • Six damper specimens were designed and physically tested. • Proposed hybrid damper can achieve excellent energy-dissipation capacity and ductility. • The resisting mechanism of the hybrid damper was comprehensively numerical studied. • A theoretical prediction model of the novel hybrid damper was developed. [ABSTRACT FROM AUTHOR]

This paper examined the hysteretic performance of a novel hybrid self-centring beam-to-beam connection equipped with shape memory alloy (SMA) plates and SMA Belleville washers. An experimental programme employing three proof-of-concept test specimens with varied SMA plate geometries and connection configurations was conducted. The test connections showed recentring performance with controllable residual deformations. The encouraging energy dissipation capacity of the test connections accompanied by excellent ductility was also confirmed. Subsequently, a numerical study was carried out to help interpret the test results and to further examine the connection's load carrying mechanism. In the numerical work, a hybrid finite element (FE) modelling technique enabling reproducing the residual strain development of SMA plates under hysteretic loading was developed and verified. The test and numerical study showed that the self-centring ability of the connection was appreciably affected by the hysteretic behaviour of SMA plates. The FE results also confirmed that the connection behaviour was sensitive to the connection configuration, and a minor gap between the beam segments could initiate intense buckling of the SMA plates. Nevertheless, the lateral deflection of the SMA plates can be suppressed by effective buckling restraints. To facilitate practical application, a theoretical prediction model enabling the quantification of a bilinear skeleton response of the connection was proposed, and the adequacy of the prediction model was evidenced by the correlation among the results of the tests, FE simulations and design predictions. • Beam-to-beam connections equipped with SMA plates and washers were tested. • The connections showed recentring performance. • A hybrid finite element modelling technique was developed. • A bilinear model for quantifying the nonlinear behaviour was proposed. [ABSTRACT FROM AUTHOR]

Driven by the demand of producing novel seismic resilient structures, this study focused on steel moment resisting frames equipped with superelastic shape memory alloy (SMA) connections in the self-centring energy dissipation bays, and the emphasis was given to a direct-iterative design method for performance-based-plastic-design of the system under earthquake motions. Utilising the equivalent single-degree-of-freedom (SDF) oscillator which may reasonably quantify the dynamic responses of a multi-storey structure, an inelastic structural seismic demand model motivated by nonlinear spectral analyses was developed, and the statistic features were accounted. As the theoretical basis of the design philosophy, the seismic energy equilibrium equation of the structure was correlated with structural arrangement and earthquake motion characteristics. Then, a stepwise plastic design methodology enabling practising engineers to search for a feasible design strategy was proposed. Three prototype structures were developed following the proposed method, and finite element models of the systems were developed. The adequacy of the modelling techniques was verified by the test database, and the sufficiency of the hysteretic model of the structure was also justified. The seismic responses of the prototype structures were estimated by nonlinear static and dynamic analyses. The analysis data pool confirmed that the prototype structures were able to achieve the damage-control objective by limiting the maximum interstorey drifts below the prescribed deformation threshold, and inelastic actions were concentrated in the self-centring energy dissipation bays. [Display omitted] • Probabilistic energy factor demand spectra for self-centring system under near-field earthquake motions was developed. • A performance-based-plastic-design methodology was developed from a statistic perspective. • The sufficiency of the proposed design methodology was confirmed. [ABSTRACT FROM AUTHOR]

A full-scale test programme for reinforced single-coped beams with slender web (RSCBSW) connections is reported in this paper. The test matrix included reinforcement types and coping details. The adequacy of the two reinforcement strategies was confirmed by the test results, and it was found that all specimens failed by buckling of the plate girder section away from the coped region. The test results also showed that for the reinforcement strategy with double full-depth transverse stiffeners, the decrease in the strength of the specimen in the post-ultimate stage was comparatively less significant compared with the specimens strengthened by a single full-depth transverse stiffener, and this phenomenon was more apparent in the case of a deep cope. Subsequently, finite element (FE) models of test specimens were developed to replicate the behaviour of the RSCBSW connections, based on which a parametric study covering a wider range of factors was conducted. The numerical results further confirmed the effectiveness of the reinforcement strategy, and no models experienced local web buckling in the vicinity of the cope. The available design equations to quantify the buckling resistance of the plate girders were applied to the test specimens and the numerical database. It was found that for cases with double full-depth transverse stiffeners, the design predictions were generally conservative. In contrast, unsafe predictions were obtained for several cases with a deep cope which was enhanced by a single full-depth transverse stiffener. [Display omitted] • Reinforcement strategies for enhancing single-coped beam with slender web connections were experimentally examined. • A parametric study covering a wider range of factors was conducted. • The effect of the longitudinal stiffener was confirmed. • The design equations for quantifying the resistance of the specimens were revisited. [ABSTRACT FROM AUTHOR]

This study presents an experimental and numerical investigation of block shear strength of high strength steel (HSS) bolted connections under double shear. A total of 16 HSS (grades Q690 and Q960) and eight mild steel (MS) (grade Q345) bolted connection specimens with various geometric configurations were tested and failed in block shear failure mode. The test and finite element (FE) analysis results confirmed that the block shear failure is a combination of fracture of the net tension plane and yielding of the effective shear plane, which is located between the net and gross shear planes. The effects of material properties (such as ductility and tensile-to-yield strengths ratio (f u / f y)) of steel materials on the block shear strength were comprehensively investigated based on the validated FE models. It was found that the tensile stress across the net tension plane could be fully developed irrespective of the steel grade due to effective stress redistribution along the net tension plane and the beneficial effect of the biaxial tensile stress state. However, the shear stress magnitude along the shear plane is influenced by the ductility and f u / f y ratio of steel materials and the length of the shear plane. The low ductility and f u / f y ratio of HSS materials did not allow for effective stress redistribution along the long shear plane and the shear yielding could only partially develop along the shear plane at the ultimate state. For the HSS specimens with short shear planes, the shear stress could develop up to the shear yield strength in general. Finally, the accuracy of the existing design equations in various design codes (i.e., prEN 1993–1–8: 2021, ANSI/AISC 360–16, and CSA S16–19) and relevant literature for predicting the block shear strength of bolted connections was evaluated and design recommendations were provided. • The block shear strength of high strength steel bolted connections was studied. • 16 high strength steel and eight mild steel bolted connections were tested. • The effects of steel grades and connection configuration were investigated. • Test observations were further illustrated by finite element analysis. • The accuracy and consistency of the existing design methods were evaluated. [ABSTRACT FROM AUTHOR]

Duplex stainless steel (DSS) is an emerging construction material for structural engineering, which is featured with high mechanical strength and superior corrosion resistance. Compared with considerable research on DSS structural members, available research is relatively limited for structural joints/connections between these members. In line with this concern, this paper presents a comprehensive experimental and numerical study of duplex stainless steel bolted connections (DSSBCs), focusing on the behaviour and design related to block shear failure. Eleven specimens are tested to investigate the effect of different bolt arrangements on the block shear behaviour. Furthermore, a detailed numerical study was performed as a supplement to the experimental tests, where the anisotropic mechanical properties of DSS are considered in the finite element modelling. Based on the test and analysis results, it is found that the block shear failure mode of DSSBCs resembles that of carbon steel bolted connections, which can be characterised as necking of the tensile section and yielding of the shear sections. Using the experimental and numerical data obtained in this and previous studies, the applicability of various block shear design methods to stainless steel bolted connections is assessed. An updated design method is proposed for predicting the block shear capacity of duplex and austenitic stainless steel bolted connections. A proper partial safety factor/resistance factor is suggested for the proposed method based on the results of reliability analyses. • Block shear of duplex stainless steel bolted connections (DSSBCs) are studied. • DSSBCs exhibit similar block shear mode to carbon steel bolted connections. • Existing design methods are evaluated for stainless steel bolted connections. • A modified method is proposed for stainless steel bolted connections. • A reliability analysis is performed to provide suggestion of partial factor. [ABSTRACT FROM AUTHOR]

This work presents an energy-based plastic design method for steel staggered truss framing (SSTF) structures with multiple Vierendeel panels. The effectiveness of the method was investigated and the improved seismic performance of plastically designed SSTF structures was verified. First, parameter analysis based on a refined finite element analysis model of steel trusses with multiple Vierendeel panels was conducted. The plastic bending resistance ratio of the chord member to the intermediate vertical member was recommended based on evaluating the failure modes. Then, the energy-based plastic design procedure for the SSTF structure with multiple Vierendeel panels were described step by step. Finally, three SSTF structures were comparatively analyzed by pushover analysis and nonlinear time-history analysis, including a force-based designed SSTF structure with single Vierendeel panels, a plastically designed SSTF structure with single Vierendeel panels, and a plastically designed SSTF structure with multiple Vierendeel panels. Compared with the forced-based designed structure, the plastically designed structures showed slightly lower load-carrying capacities, but much higher ductility. The force-based designed structure had obvious soft stories, while the two plastically designed structures showed more uniform story drift distributions and formed a controllable failure mode. Compared with the structures with single Vierendeel panels, the rotation demand on the chord members of SSTF structures with multiple Vierendeel panels was significantly reduced. • The plastic bending resistance ratio of the chord member to the intermediate vertical member was recommended. • An energy-based plastic design method for SSTFs with multiple Vierendeel panels was proposed. • Seismic behaviors of SSTFs with multiple Vierendeel panels were elaborated. [ABSTRACT FROM AUTHOR]

• Block shear failure of austenitic stainless steel bolted connections is studied. • The results of 15 connection tests are reported. • An extensive finite element analysis is performed to examine the block shear behaviour. • Austentic stainless steel bolted connections exhibited three distinctive block shear mechanisms. • Existing design methods are evaluated and a modified method is proposed. Austenitic stainless steel possesses very high ductility and ultimate-to-yield strength ratio, which could possibly affect the block shear failure mechanism and the corresponding ultimate capacity of bolted connections made of this material. In response to this concern, a comprehensive experimental and numerical study on the block shear behaviour of austenitic stainless steel bolted connections (ASSBCs) is conducted and reported in this paper. Based on the results of 15 experimental tests, it is found that the governing block shear mechanism of ASSBCs (for 14 out of the 15 tests) at the ultimate load corresponds to cracking of the shear sections prior to fracture of the tensile sections. This differs significantly from the conventionally accepted block shear mechanism of mild steel bolted connections, which is net section fracture of the tension area and yielding of the shear area. This observation was further confirmed by a numerical study based on validated finite element models, where three block shear mechanisms were identified for ASSBCs. A thorough parametric study was then carried out to clarify the effects of key design parameters on the block shear behaviour of ASSBCs. Finally, the experimental and numerical results are used to evaluate the applicability of existing design equations to predicting the block shear capacity of ASSBCs. An improved block shear equation is subsequently proposed based on the available data. [ABSTRACT FROM AUTHOR]

Tapered concrete-filled double-skin steel tubular columns with large hollow ratio (LHR-CFDST) have a good application potential in wind turbine towers, where they are commonly subjected to the combined action of compression, bending, shearing and torsion. Up to now, research work on the behaviour of tapered LHR-CFDST columns under combined loads is seldom reported and relevant experimental data are limited. This paper presents an experimental and numerical study on the tapered LHR-CFDST column under combined compression-bending-shear-torsion loads. Seven specimens with different parameters including the tapered angle, the hollow ratio, the torsion-to-bending ratio, the axial compression ratio and the height-to-diameter ratio were tested. The experimental results in terms of failure modes, load versus deformation relations and strain responses were discussed. Reliable finite element models were established to conduct numerical analysis in an extended parameter range. The mechanism of columns and the effects of torsion-to-bending ratios, axial compression ratios, height-to-diameter ratios, tapered angles, hollow ratios, diameter-to-thickness ratios of steel tubes and the material strength were revealed. The suitability of the existing ultimate capacity prediction method was evaluated for tapered LHR-CFDST columns. It is found that the failure mode of columns under compression-bending-shear-torsion loads is related to the torsion-to-bending ratio. The columns behave in a ductile manner under moderate axial compression. Tapered angle has a slight effect on the bending capacity of the column, whereas the capacity declines with the increase of hollow ratio and torsion-to-bending ratio. The existing method gives a conservative prediction for the ultimate capacity of tapered LHR-CFDST columns. • Tests on tapered LHR-CFDST columns under combined compression-bending-shear-torsion loads are reported. • Behaviour and mechanism of tapered LHR-CFDST columns under combined loads are discussed. • Numerical analyses are conducted and effects of important parameters are revealed. • Suitability of the existing ultimate capacity prediction method is evaluated. [ABSTRACT FROM AUTHOR]

• 33 high strength steel and 15 mild steel staggered bolted connections were tested. • The effects of steel grades and connection configuration were investigated. • Test observations were further illustrated by finite element analysis. • The accuracy of the s 2/4 g rule was re-examined. • Current design equation in EN 1993–1-12 was re-evaluated by statistical evaluation. This paper investigates the structural behaviour and ultimate strength of high strength steel (HSS) staggered bolted connections under tension. A total of 33 HSS (Q690 and Q960) and 15 Q345 staggered bolted connection specimens were tested. All specimens failed in net section fracture through the staggered path. The predicted net section resistance based on the s 2/4 g rule was achieved by most of the HSS specimens. For the specimens with a small bolt pitch to gauge (s/g) ratio, the connection efficiency (i.e., the ratio between the test ultimate load and the calculated net section resistance) exceeded 1.0 and decreased gradually with an increasing s/g ratio. Compared with the mild steel (MS) specimens, in general the HSS specimens have lower connection efficiency and overall deformation capability. Subsequently, the structural behaviour of the test specimens was investigated using finite element (FE) analysis to further interpret the test observations. The results of the test and the FE analysis indicated that for the HSS specimens, effective stress redistribution along the staggered net section was observed although the ductility and the ratio of tensile strength to yield strength (f u /f y) of HSS material are relatively lower than those of the MS material. In addition, it was also observed that the biaxial state of stress that existed in the plate area between the staggered bolt holes was influenced by the s/g ratio, which would affect the ultimate strength of the test specimens. A reliability analysis of the HSS specimens test results was carried out to re-evaluate the partial factor adopted in the design equation of the net section resistance of HSS (up to S700) in EN 1993-1-12. The analysis results of the limited test data showed that the net section resistance of HSS staggered bolted connections was predicted conservatively by the current design equation with a partial factor of 1.25. [ABSTRACT FROM AUTHOR]

In this paper, the seismic performance of cold-formed thin-walled steel walls with diagonal braces is studied by means of experiments and finite element analysis. In total, horizontal hysteretic loading tests were carried out on six full-scale cold-formed thin-walled steel walls. The influence of diagonal bracing, the screw spacing, wall panels and vertical loads on the seismic performance of the walls was investigated from the aspects of hysteretic curves, skeleton curves, the lateral stiffness degradation and the energy dissipation capacity. It was found that diagonal bracing could significantly improve the load-bearing capacity, stiffness, and energy dissipation capacity of the walls. However, the lateral resistance increased slightly because of premature buckling of the transverse braces at the connection between the diagonal and transverse braces. In addition, finite element models of the wall specimens were established by ABAQUS software and validated against the experimental data. A preliminary parametric study was also conducted to further examine the influence of essential parameters on the behavior of cold-formed steel walls with diagonal braces. • The hysteretic behavior of cold-formed thin-walled steel walls with diagonal braces were investigated. • Six full-scale specimens were tested under cyclic load. • Comparison between the specimens with and without diagonal braces are illustrated. • The parametric analyses were conducted by the numerical simulation. [ABSTRACT FROM AUTHOR]