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Welded tubular joints are integral components in various engineering structures, subject to cyclic loading conditions throughout their operational lifespan. This paper investigates the evolution of welding residual stresses within the CHS X-joint and CHS double K-joint under cyclic loading, shedding light on their intricate behavior and potential implications for structural integrity. The advanced XRD experimental technique enables the characterization and monitoring of residual stress variations over multiple loading cycles. Assisted by the non-destructive XRD measurements, this study validates the optimization-improved thermal-mechanical simulation method for predicting not only the as-welded residual stresses in the tubular joints but also the residual stress evolutions during the cyclic loading tests. The most pronounced relaxation of peak residual stresses in the tubular joints occurs within the first cycle and then maintains a relatively stable magnitude in subsequent cycles. The findings of this research contribute to the enhancement of structural reliability and serve as a foundation for mitigating the adverse effects of welding residual stresses in welded tubular joints under cyclic loading scenarios. • This paper reports the experimentally measured residual stress during cyclic loads. • The residual stresses in both X and DK CHS joints relax significantly within 1st cycle. • Numerical analyses predict closely the evolution of residual stresses under cyclic actions. [ABSTRACT FROM AUTHOR]

Corrugated steel plates are widely used in engineering industries for their superior out-of-plane stiffness and buckling properties. The more complex corrugated configurations than plane steel plates lead to complicated and variable buckling behaviors of corrugated steel plates. The extremely high sensitivity of the plate buckling to geometric characteristics and initial imperfections further improves the difficulty of buckling analysis of corrugated steel plates. This paper presents a comprehensive study on the buckling behavior of corrugated steel plates under uniaxial compression based on 12 test specimens and 512 numerical models with multiple evaluation dimensions such as failure modes, buckling displacements, buckling loads, and buckling strengths. Parametric studies are carried out to reveal the influence mechanisms of critical parameters, including plate thickness, plate height, and number of corrugations. Furthermore, an analytical model developed based on the orthotropic plate theory is proposed for the buckling analysis of corrugated steel plates under uniaxial compression, and a semi-analytical solution for the assessment of the buckling strength is presented with satisfactory accuracy and universality of application. Relevant theoretical results are able to realize the efficient estimation of the buckling strength more than the correlation level of 0.99. The research results can serve as references for subsequent studies and provide valuable support for the engineering structural design of corrugated steel plates. • Buckling of corrugated steel plates under uniaxial compression tested; • Influence of the corrugation configuration on plate buckling revealed; • Efficient semi-analytical model for the buckling strength proposed. [ABSTRACT FROM AUTHOR]

This paper investigated the compression behaviors of square steel tube (SST) columns used in cold-region engineering structures. Twenty-eight SST columns were tested at low temperatures of 20, −30, −60, and − 80 °C. The studied parameters were low temperature (T) and slenderness ratio (λ) of SSTs. Under low-temperature compression, stub columns (λ = 5) failed in local buckling whilst slender columns (λ = 15 and 25) failed in global buckling. Low temperatures exhibited marginal effects on failure modes, and slightly improved (less than 12 %) the ultimate compressive resistance (P u) of SSTs. Decreasing T and λ values increased the compressive resistance of SSTs. Finite element (FE) models were established to simulate compression behaviors of SSTs at low temperatures, with accuracy confirmed by 28 test results. The FE parametric studies indicated that decreasing the width-to-thickness ratio of SSTs generally improved their compression capacity and ductility. Moreover, different code prediction formulae in GB50017, AISC 360–16, and Eurocode 3 for SSTs were checked to predict the P u. Finally, prediction equations were developed to predict the compression resistance of SSTs at low temperatures. The prediction equations provided reasonable estimations on P u with an average discrepancy of 4 %. • Low temperatures increases the strength and stiffness of square steel tubes (SSTs). • Increasing the slenderness ratio of SSTs reduces their low-temperature compression capacity. • Reducing the width-to-thickness ratio improves compression capacity and ductility of SSTs. • Prediction equations predict well the low-temperature compression resistance of SSTs. • Developed FEM simulates well the low-temperature compression behavior of SSTs. [ABSTRACT FROM AUTHOR]

Real-time hybrid simulation can be used to test physical models of a structural element or a sub-assembly with actuators applying loading and realistic boundary conditions in real time, considering interaction with the rest of the structure. When applied to structural fire engineering, this approach enables cost-effective fire experiments as compared to full-scale structural fire tests. This paper describes the application of a control strategy for real-time hybrid fire simulation that decouples the physical substructure response from the control design. The mathematical formulation of the proposed strategy is presented as an example of a steel moment frame with one column under fire. The steel column first experiences slow thermal expansion under elevated temperatures, followed by dynamic buckling at failure. The proposed real-time hybrid fire simulation strategy is tested using a shear-slip mechanism where a bolt serves as a locking element within a sliding shaft to emulate the considered steel column. At the start of the test, the bolt takes the force applied by an actuator that moves slowly to mimic thermal expansion. The bolt eventually shears, and the sliding mechanism displaces quickly to mimic buckling. A servo-hydraulic actuator, tuned to replicate the behaviour of the surrounding frame, communicates the interfacing boundary condition. The test is able to capture slow thermal expansion and the dynamic behaviour at the time of buckling, for which the obtained result is also applicable to progressive collapse applications in general. • A novel control strategy is presented for real-time hybrid simulation for structural fire testing. • The method is applied for testing dynamic buckling of steel columns. • Two real-time hybrid simulation tests are conducted. • Test 1 emulates slow thermal expansion under elevated temperatures. • Test 2 simulates dynamic buckling at failure as expected under fire hazards. [ABSTRACT FROM AUTHOR]

This paper has conducted shaking table tests and numerical simulations to analyse and evaluate the seismic behavior of cable-stiffened single-layer cylindrical latticed shells (SLCLSs) under seismic loads. A novel most unfavorable imperfection method based on the proportion of bending strain energy is proposed, which provides a most unfavorable initial geometric imperfection for the cable-stiffened SLCLS models compared with the consistent imperfection method. Shaking table tests on the cable-stiffened SLCLS model are also carried out, and the accuracy of the proposed numerical simulation and imperfection methods is validated through comparison with experimental results. Through numerical analysis, three typical failure modes of the cable-stiffened SLCLS model under seismic loads are identified: instability failure mode, strength failure mode, and instability-strength coupled failure mode. Finally, the impact of various parameters, including length-to-width ratio, rise-to-span ratio, support conditions, cable initial prestress, and roof loads, on the failure modes and dynamic responses of the cable-stiffened SLCLS models under seismic loads is evaluated. Recommendations are provided for the design and application of cable-stiffened SLCLS structures in actual engineering projects. • Novel method predicts initial geometric imperfections in SLCLSs, enhancing safety and seismic analysis accuracy. • Shaking table tests validate numerical simulation and imperfection methods for reliable seismic analysis. • Three failure modes identified for SLCLS structures under seismic loads: instability, strength, and coupled failure. • Impact of key parameters on failure modes and dynamic responses of SLCLSs under seismic conditions. [ABSTRACT FROM AUTHOR]

Ductile crack initiation and propagation simulation is of great importance in metal structures, which is one of main failure modes. Research objects of common fracture mechanics are solids with existing cracks. However, ductile fracture of uncracked solids is also one of the main concerns in structural engineering, especially for strong seismic loading. There is a great difficulty in simulating both crack initiation and propagation of uncracked solids using conventional fracture mechanics. A simple unified method to simulate the two stages with acceptable accuracy is thus required. For ductile crack initiation, a number of models based on the void growth concept have been proposed. However, research on ductile crack propagation is still limited, and there is still a lack of simple approaches to simulate both ductile crack initiation and propagation of uncracked solids. This paper aims to investigate ductile crack initiation and propagation of high strength steel under high stress triaxiality by combination of the void growth model for ductile crack initiation and an energy balance approach for ductile crack propagation. In this paper, a straightforward approach to obtain the ductile fracture energy only using smooth tension coupon tests is proposed. Two series of single edge notched specimens with different notch depths and notch configurations are manufactured. Both experimental and numerical studies under monotonic tension are conducted. The ductile crack initiation and propagation processes of notched high strength steel specimens are simulated with acceptable accuracy using the proposed approach. [ABSTRACT FROM AUTHOR]

The present paper focuses on a new, alternative design philosophy: the Overall Interaction Concept (O.I.C.). This concept, based on the well-established resistance-instability interaction and the definition of a generalised relative slenderness, was thought and built to i) improve actual design practice, ii) increase accuracy, iii) advance simplicity and consistency, and iv) provide a sound framework for computer-assisted resistance predictions. This paper first details the bases and features of the O.I.C. approach, and provides mechanical interpretations of its application steps. Comprehensive sets of results at the cross-sectional level are then presented, for both H-shaped and hollow sections. Ayrton-Perry-based χ - λ design relationships for hollow structural shapes are proposed and shown to lead to more accurate, consistent and safe resistances when compared to Eurocode 3 rules, in addition to being significantly simpler in application. As for the behaviour and response of members, numerous F.E. results are reported, demonstrating the potential of a χ - λ approach to successfully apply to members under combined load cases. Also, the challenging case of coupled instabilities is investigated, and the O.I.C. approach is showed to be very efficient and appropriate. Further developments towards the derivation of full O.I.C. procedures to steel members are currently under way. [ABSTRACT FROM AUTHOR]

Concrete-filled double skin steel tubular columns with large hollow ratio (LHR-CFDST) have been commonly used in recent years. With the increasing size of the engineering structures, one efficient way to decrease the consumption of steel is to increase the diameter-to-thickness ratio. Few studies have been conducted to report on thin-walled LHR-CFDST columns. At the same time, local buckling may occur in these structures in the absence of stiffening measures. Based on this, an experimental and numerical analysis was carried out for the stiffened thin-walled LHR-CFDST columns under axial compression in this paper. Five thin-walled LHR-CFDST columns with different stiffening measures (ribs, studs) were tested. The failure modes, load versus shortening curves, local buckling behaviours and ductility were investigated. The test results indicates that the stiffened measures effectively delayed the appearance of local buckling and increased the peak load. Besides, the finite element models validated by the test results were applied to the subsequent mechanical mechanism analysis of the stiffened thin-walled LHR-CFDST. It can be seen that the stiffened measures enhance the confinement of the inner and outer steel tubes on the concrete and greatly improve the ultimate strength of the concrete. Finally, the predicted peak load formulae in the existing design specifications were modified by combining the characteristics of the specimens in this paper. The peak load values obtained by the improved formulae agreed well with the test results. • Five thin-walled CFDST columns with different stiffening forms (ribs, studs) were tested under axial compression. • The effects of stiffeners on the local buckling and peak load of specimens were revealed. • The validated finite element model was developed to further analyze the structural mechanisms. • The interaction between steel tubes and concrete were investigated. • The predicted peak load formulae in the existing design specifications were modified. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the microstructure and mechanical properties of S31603 + Q355B stainless-clad (SC) bimetallic steel welded connections with different welding configurations. A comprehensive research approach was employed, including microstructure analysis, static tensile test, impact test, bending test, Vickers hardness distribution measurement, and analysis of welding economy and efficiency. Four types of welded connections were examined to understand their performance variations arising from different welding configurations. Based on the findings, a recommended welding configuration suitable for structural engineering applications was proposed. Research outcomes showed that the decarburization and carbon accumulation zones were observed at the fusion interface during the welding of dissimilar metals. It should be noted that martensite was formed in the substrate, or the base metal, due to diffusion of alloying elements, with a more pronounced effect observed with higher welding heat inputs. In order to minimize the fusion area of dissimilar metals, it is advisable to avoid using a single welding consumable made of stainless steel as the mechanical properties of the welded connection were not significantly influenced by the use of stainless steel welding consumables with higher Nickle (Ni) and Chromium (Cr) alloying content in the transition region. Consequently, the same welding consumable should be employed in the transition region to simplify the welding procedure and to enhance the welding efficiency. • Micro-macro tests on stainless-clad bimetallic steel welded connections were done. • Effects of various welding configurations were clarified. • The unique behaviour of transition weld zones were described. • The advantages and disadvantages of each welding configuration were discussed. • The recommended welding configuration was proposed. [ABSTRACT FROM AUTHOR]

This is the second of two papers that describe a study conducted to develop system resistance factors for Direct Design Method (DDM) of steel frames by advanced analysis in accordance with Appendix 1 of the AISC Specification and similar design requirements. A companion paper [1] presents a framework for determining system resistance factors accounting for inherent uncertainties in the ultimate strength of a frame. In this paper, system resistance factors are developed for low- to mid-rise braced and moment resisting frames with regular and irregular configurations for various loading conditions and different target reliability levels. Recommendations are made for the appropriate target reliabilities and associated system resistance factors for use in designing steel frames at the system level by advanced analysis. [ABSTRACT FROM AUTHOR]

The design of steel frames by advanced analysis (second-order inelastic analysis with imperfections) of overall system behaviour is permitted in the American steel specification AISC360-10 and the Australian Standard AS4100. In both specifications, the strength of a structural frame can be determined by a rigorous system nonlinear analysis in lieu of checking member resistances to the specific provisions of the Specification, provided that the limit states covered by the Specification equations are detected by the inelastic analysis, and a comparable or higher level of structural reliability is achieved by the inelastic analysis than by member-based design. This system-based, design-by-advanced analysis approach is termed “Direct Design Method” (DDM). In DDM, a system resistance factor is applied to the frame strength. The system factor in AISC360-10 was adopted without considering its impact on frame reliability. This paper describes the framework for developing reliability-based system resistance factors suitable for use with DDM. A simple frame is used to demonstrate the procedures. Appropriate system resistance factors for various load cases and design recommendations are presented in a companion paper [1] based on the system reliability analyses of a series of steel frames. [ABSTRACT FROM AUTHOR]

Asymmetrically supported and loaded sandwich panels with a polyurethane soft core and isotropic or orthotropic steel faces were analyzed in laboratory tests and numerical simulations. The influence of the steel face microprofilation on the mechanical and kinematical responses of the sandwich panel is considered in the paper. The real experiments were conducted for two supporting systems. For each supporting system isotropic and orthotropic sandwich faces were taken into account. The numerical simulations, in which 2D composite shell elements were used, correspond to the real experiments. The laboratory tests showed that introducing the orthotropic face layer significantly increases the load capacity of the sandwich panel. In the case of asymmetrically supported systems effective flexural rigidity increases too. The paper demonstrates that a relatively simple FE model can be successfully used to assess the global behavior of sandwich panels in complex boundary conditions. Satisfactory consistency of the numerical and real results in the linear range of structural behavior was obtained. Further improvement of the model is possible by introducing a definition of the failure criteria. [ABSTRACT FROM AUTHOR]

This paper presents the development, implementation, and validation of a macro-element suitable for the linear analysis of innovative 3D plug-and-play joints between tubular columns and lightweight steel truss-girders. The macro-element is based on the component method, accounts for the three-dimensional interaction between the tube faces, and its components have a clear physical meaning. Simplified procedures are developed for the closed-form computation of the stiffness matrix of the macro-element based on the geometric and mechanical properties of the nodal zone. This facilitates practical application in everyday design scenarios. Furthermore, the macro-element's architecture is implemented in the framework of OpenSees as a standalone beam-to-column joint finite element. Validation of the conceptual design is accomplished through parametric studies, comparing its performance with models generated in higher-order finite element commercial software, Abaqus. This research offers a valuable resource for the linear analysis and design of innovative 3D plug-and-play joint connections in structural engineering, enhancing efficiency and reliability in construction practices. • Created a macro-element for linear analysis of innovative plug-and-play steel joints. • Accounted for 3D tube face interactions in component-based macro-element design. • Implemented the macro-element as a stand-alone beam-to-column joint FE in a software. • Validated the beam-to-column joint FE against higher-order FE models. [ABSTRACT FROM AUTHOR]

Previous studies have established a variety of cumulative damage models (CDMs) for either structural materials or members to perform an exquisite evaluation on plastic-induced deterioration of structural engineering under severe seismic actions. Nevertheless, the existing CDMs consider different influencing factors and hence tend to produce significantly different simulation performance. On the other hand, the influencing variables of CDMs are likely affected by the description on the cyclic stress-strain relation. Thus, the quantification of seismic damage is affected by the selection of both CDM and constitutive model. Existing relative studies mainly focus on the development and refinement of theoretical models. However, the understanding on simulation performance difference induced by the selection of models is still limited. This paper is aiming to clarify the influence of different constitutive models and CDMs on the cumulative damage behaviors simulated. Firstly, three types of cyclic constitutive models and nine CDMs are reviewed and their material parameters are summarized. The CDMs selected include the deformation-type models, the energy-type models and the combined-type models. Based upon different CDMs, the low-cycle fatigue (LCF) curves of mild structural steel are generated and compared to the corresponding Coffin-Manson relations. Subsequently, the damage evolutionary curves of different CDMs are simulated based upon several representative cyclic loading protocols. The influence of constitutive models and CDMs on the LCF curves and damage evolutionary curves are thoroughly studied. Besides, the sensitivity of CDMs on strain ratios and the influence of cyclic loading protocols on damage evolutionary curves are simultaneously clarified. The research findings can lay a solid foundation for the selection and combination of the relative analytical models with regards to different circumstances. • Cumulative damage models are reviewed. • Low-cycle fatigue lives are calculated through cumulative damage models. • Damage evolutionary laws are simulated through cumulative damage models. • The performance of constitutive models and cumulative models are compared. [ABSTRACT FROM AUTHOR]

Abstract: Cold-formed structural sections are manufactured at ambient temperature and hence undergo plastic deformations, which result in an increase in yield stress and a reduction in ductility. This paper begins with a comparative study of existing models to predict this strength increase. Modifications to the existing models are then made, and an improved model is presented and statistically verified. Tensile coupon data from existing testing programmes have been gathered to supplement those generated in the companion paper [1] and used to assess the predictive models. A series of structural section types, both cold-rolled and press-braked, and a range of structural materials, including various grades of stainless steel and carbon steel, have been considered. The proposed model is shown to offer improved mean predictions of measured strength enhancements over existing approaches, is simple to use in structural calculations and is applicable to any metallic structural sections. It is envisaged that the proposed model will be incorporated in future revisions of Eurocode 3 [2,3]. [Copyright &y& Elsevier]

Abstract: This paper presents the main results of the form finding analysis, model testing and on-site investigation on a mixed structure consisting on a system of steel tubular trusses coupled with a spatial cable net. Firstly, the combining method of force density and finite element is proposed for the form finding analysis of the mixed structure. Then, experimental tests are carried out on a scaled model in order to assess the different levels of pretension to be introduced in the cable system. Finally, the result of the on-site assessment activity carried out to monitor the real force level acting on different cables is presented and the comparison between the inspection results and the design target is made. The construction of the mixed structure has been successfully carried out and completed on the basis of the work presented in this paper. [Copyright &y& Elsevier]

In fire conditions the provision of connection ductility is key to the prevention of brittle failure and progressive collapse of steel and steel-concrete composite framed structures. This paper describes the development and testing of a novel connection concept intended to provide appropriate ductility enhancement compared to that of conventional connection types. The connection consists of two connection pieces, each of which takes the form of a web cleat which includes a semi-cylindrical section. This section allows the beam-end to move towards or away from the column-face by deforming plastically. A simplified analytical model has been developed to simulate the mechanical behaviour of the proposed connection, and this model will eventually enable the incorporation of this new connection type into global frame analysis to be used in performance-based structural fire engineering design. The model has been tested against FEA simulations and against model-scale experiment results, indicating that it can predict the behaviour of the connection with satisfactory accuracy. Preliminary sub-frame analysis results indicate that the proposed connection behaves similarly to an idealized pinned connection under ambient-temperature conditions, but provide significantly larger ductility, and resistance to disproportionate collapse, compared to conventional connection types. • A novel connection which allows large deformation of connected beam is proposed. • Analytical models have been developed to simulate mechanical behaviour of connection. • Analytical models have been validated against FEA simulations and experiment results. • Simple sub-frame model has been created to study the performance of novel connection. • The novel connection can provide larger ductility compared to conventional types. [ABSTRACT FROM AUTHOR]

Abstract This paper aims to study crowd-induced vibration control of long-span steel footbridges with different dynamic characteristics by combining methods of site measurement and numerical simulation. Four kinds of footbridge models with sensitive vertical natural frequencies of easily generating human-bridge resonance under pedestrian loading are designed based on an actual steel footbridge. The numerical models are firstly validated by comparative investigation between the site measurement and the simulation. Detailed study on dynamic responses of the four footbridges with and without controlling systems of tuned mass damper (TMD) and multiple tuned mass damper (MTMD) is then conducted under 13 cases of crowd random excitations, rhythmic running and jumping excitations. Results show that the numerical simulation agrees well with the site measurement data. TMD system is found to be highly efficient in reducing vibration responses only when the excitation frequency is basically consistent with the structural natural frequency, which obviously limits the application of TMD system in footbridges as wider excitation frequency bandwidth is caused by human activities. MTMD system are demonstrated to be with higher vibration absorption robustness appearing predominant and stable capacity of reducing structural vibrations under all the crowd random and rhythmic excitations for the four footbridges. Highlights • Vertical vibration control of long-span footbridges with different dynamic characteristics is investigated by site measurement and numerical simulation. • Crowd excitations, such as random crowd, rhythmic running and jumping crowd, are discussed to show dynamic responses and controlling effectiveness of TMDs. • TMD system is found to be highly efficient in reducing vibration responses only when the excitation frequency is basically consistent with the structural natural frequency. • MTMD system are demonstrated to be with higher vibration absorption robustness appearing predominant and stable capacity of reducing structural vibrations under the crowd random and rhythmic excitations. [ABSTRACT FROM AUTHOR]

Abstract Passive control using metallic energy dissipation system has been proved to be a reliable means of seismic upgrading for building structures. Furthermore, configuration of the metallic energy dissipation system within a structure may have significant influence on the overall seismic performance. This paper presents a systematic approach for optimal configuration of the metallic energy dissipation system in shear-type building structures subject to seismic excitation consistent with the design code, where the mechanical parameters of the metallic energy dissipation component in each story level are taken as the optimization variables. Two objective functions as well as two optimization levels are proposed. An improved real-coded genetic algorithm is employed as the optimizer. The framework of the optimal configuration design process is given and demonstrated in an application example. Based on the results of the application example, the influence of different algorithms, optimization levels and objective functions are further analyzed. Moreover, a simplified fine level optimization approach is proposed based on the parameter sensitivity, which can yield satisfying results with less time. Highlights • The mechanical parameters of the MED component in each story level are taken as the optimization variables. • An improved real-coded genetic algorithm is proposed for solving the optimization problem. • The spectrally-adjusted earthquake ground motion is employed to conduct the nonlinear time history analysis. • A simplified fine level optimization approach is proposed based on the parameter sensitivity for better efficiency • A systematic design framework is proposed to properly configure the supplemental metallic energy dissipation system. [ABSTRACT FROM AUTHOR]

Abstract A general forming method for super-long span mega-latticed structures has been developed, based on the key parameters for five types of structure, together with a finite element model. The method combines the molding idea for universal spherical mega-latticed structures and the geometric topological relations of the improved traditional single-layer reticulated shell. The static and economic indexes of six kinds of 800 m span mega-latticed structures, with the same geometry, control parameters and loads, were calculated, and the force law for these structures under static load identified. Then structures suitable for spans of 1000 m and 1200 m were considered. The static performance and economic indexes showed that the mechanical and economic performance of the Geodesic type mega-latticed structure and the Three-dimensional grid type mega-latticed structure were excellent. In order to promote the engineering application of these structures, the influence of four key parameters on the performance of 1000 m structures was studied, and a reasonable range of indicative parameters obtained. Highlights • It is proved that the modeling method is universal for spherical mega-latticed structures. • The paper can better explain the static properties and the stability of super-long mega-latticed structures. • It is proved that the structure types selected have good mechanical properties and economic performance. • It is proved that through the method of parameter analysis, economic and reasonable structures can be obtained. [ABSTRACT FROM AUTHOR]

Abstract Over the last few decades, progressive collapse disasters have drawn the attention of codified bodies around the globe; as a consequence, there has been a renewed research interest. Structural engineering systems are prone to progressive collapse when subjected to abnormal loads beyond the ultimate capacity of critical structural members. Sudden loss of critical structural member(s) triggers failure mechanisms which may result in a total or partial collapse of the structure proportionate or disproportionate to the triggering event. Currently, researchers adopt different modelling techniques to simulate the loss of critical load bearing members for progressive collapse assessment. GSA guidelines recommend a column removal time less than a tenth of the period of the structure in the vertical vibration mode. Consequently, this recommendation allows a wide range of column removal time which produces inconsistent results satisfying GSA recommendation. A choice of a load time history function assumed for gravity and the internal column force interaction affects the response of the structure. This paper compares different alternative numerical approaches to simulate the sudden column removal in frame buildings and to investigate the effect of rising time on the structural response. [ABSTRACT FROM AUTHOR]

Abstract: Elliptical structural steel hollow sections represent a recent addition to the range of steel sections available to structural engineers. However, despite the extensive interest in their use on the basis of both architectural attraction and structural efficiency, a complete absence of fire resistance design guidance is restraining applications. This paper presents the first study ever conducted to investigate the fire resistance of steel columns with Elliptical Hollow Sections (EHS). Six columns of two slenderness and were tested under three loading levels ( and 0.6) and subjected to a hydrocarbon fire curve. The paper provides the recorded data of axial displacements and temperature profiles of the EHS steel columns, while highlighting the unique local and overall buckling failure modes of the Elliptical Hollow Section. [Copyright &y& Elsevier]

Abstract: This paper intends to draw attention to the consideration of load sequence effects on the structures’ installation and upgrading/reinforcement practice. The paper first summarises four types of load sequence effects encountered in structural engineering practice. In order to investigate the ultimate strength performance of structures with the variation of support conditions and member stiffness (due to the installation of reinforcement on members) during the structures’ life time, a practical engineering evaluation procedure is presented. The load sequence effects, which are often ignored in the daily engineering practice, are studied through the modelling of a typical offshore module frame structure subjected to a large number of load cases. From the study it is concluded that the changes of the support conditions and the added stiffness from the reinforcements may slightly change the global stiffness of the structure, while they do influence the local stiffness and reaction forces on reinforced members or members close to the supports and the reinforced members, and may therefore be unconservative. A general proposal for a simplified analysis by taking the effects aforementioned into account is presented. Furthermore, methods for capacity check and practical recommendations for increasing the efficiency of the reinforcement are also given. Finally, suggestions for further studies are also given. [ABSTRACT FROM AUTHOR]

Abstract: Existing design procedures for steel frames have been modified during the last three decades to incorporate the semi-rigid behavior of the connections into the frame design advancement. Knowledge in initial rotational stiffness of a connection is important for the global elastic analysis of frame structures. This paper presents the results of several parametric analyses on the Initial Rotational Stiffness (IRS or ) of Bolted Flush End-plate Beam (BFEB) splice connections using Finite Element Modeling (FEM). The FEMs have taken into account material behavior, geometrical discontinuities and large displacements. The analyses have been calibrated to experimental results that are also briefly reviewed in this paper. These models clearly support the numerical results and show accurate correlation between FEM and experimental results of the connections behavior. Due to the multitude of influencing parameters, an analytical description of the BFEB connections behavior has been delivered. This is based on component method, which is proposed by the Eurocode 3 as the equivalent T-stub. Also comparisons between numerical and analytical data for initial slop of moment–rotation curves are accomplished. The method for accuracy in predicting values regarding the of BFEB connection is also discussed. [Copyright &y& Elsevier]

Abstract: This paper deals with the behaviour of composite beams with particular focus on the effective slab width, which is required for simplified structural analysis and design. Current design codes propose values for the effective width which are mostly a function of the beam span ignoring in this way the influence of other important parameters. Several 3D numerical simulations are conducted in this paper in order to illustrate these parameters and accordingly a new methodology is suggested for evaluating the effective width. The proposed approach is easier to apply in comparison with other existing methods based on stress integration, and provides effective width values which result in a more reliable representation of the actual beam state when simplified analysis is carried out. The application of the new method indicates that the effective width is mostly related to the actual slab width and, in many cases, the values obtained can significantly differ from those proposed in design codes. Validation of the new approach is carried out through comparison of simplified 2D models with the results obtained from a recent experimental investigation as well as from more complex 3D numerical simulations. [Copyright &y& Elsevier]

Accurate detection of bolt body axial stress (σ b) is a significant means for bolt loosening judgment and bolt fatigue analysis in engineering structures. Strain gauges are widely used in the stress detection of engineering structures and process equipment because of their easy installation, compact structure, and applicability. This paper proposes a method to detect σ b using strain gauges based on the nut axial stress. Through theoretical analysis and finite element simulation, it is found that there is a linear relationship between σ b and nut surface axial stress (σ nx), which is verified by experimental investigations. The results show that the relationship is linearly distributed under static load. However, under dynamic load, the relationship is a flat closed curve due to the relative hysteresis effect of the bolt and nut. The closed curve is less related to the excitation frequency. However, the slope of the curve tangent decreases with the increase of dynamic load, and the decrease gradually slows down. This method is applied to the discharge valve bolt (40CrMoNiA, 10.9) of a compressor in a chemical plant. The detection results show that there is a better linear relationship between σ b and σ nx. Numerical analysis to suggest nut stress detection positions based on stress signals and dispersion. In summary, the proposed method provides a new way to monitor the bolt connection status, detect bolt loosening, and overcome the short board that the bolt body is inside the machine and cannot directly realize stress measurement. • A measurement method of indirect bolt body axial stress based on the nut surface axial stress was proposed. • Based on the theoretical method, the relationship between bolt body axial stress and nut surface axial stress was found. • The experimental setup was built to complete the verification. • The measurement method was successfully applied to the discharge valve bolt of a compressor. [ABSTRACT FROM AUTHOR]

This paper summarises findings of a study that investigated the effect of joint geometry on the load capacity of hybrid joints, which are a promising method for increasing the load capacity of joints in steel structures. The results showed that all geometries resulted in higher joint capacity for hybrid joints than for bonded joints, with an impressive increase of 43% to 142%. Furthermore, the study identified the specific effects of joint width, overlap length and distance of the bolts to the end of the overlap on joint capacity. Widening the joint led to an almost linear increase in load capacity for both hybrid and untightened bonded joints. Increasing overlap length also contributed to increasing load capacities, but not as efficiently as joint width. Despite numerical simulation and observations of fracture surfaces indicating that shortening the edge distance would increase joint capacity by applying higher compression to the overlap end, edge distance did not have a significant effect on the load capacity of hybrid joints. These findings are a significant step towards establishing a comprehensive design procedure for hybrid joints and provide important insights into their underlying principles. However, further investigation is necessary to fully understand the mechanisms responsible for the observed effects. Ultimately, developing accurate predictive models for joint strength will greatly benefit the field of structural engineering. • Bonded bolted hybrid joints can increase load capacity of joints in steel structures. • Capacity for hybrid joints resulted in 43% to 142% higher than those of bonded joints. • Widening the joint increased hybrid joints' load capacity almost linearly. • Increasing overlap length also contributed but not as efficiently as joint width. • Despite an expectation from numerical simulation edge distance did not have a significant effect. [ABSTRACT FROM AUTHOR]

This paper conducted a demolition test of a double-layer space truss (DLST) to investigate more efficient, safe and environmentally friendly demolition methods of truss systems. The high-speed 3D displacements of representative joints and the global dynamic strain response of the structure were well collected. The internal force redistribution and load-carrying mechanisms of DLST structures during demolition were explored. The results indicate that new equilibrium states were sought in the DLST through local and global internal force redistribution. When the main force transmission members were removed, the load-carrying mechanism of the DLST underwent sudden changed, which resulted in a snap-through in the structural load-carrying capacity. The test DLST exhibited three load-carrying mechanisms in time sequence during the proposed demolition: arch action, catenary action, and beam action. The theoretical vertical load-carrying capacity provided by each load-carrying mechanism was investigated separately. Finally, a progressive collapse demolition method was presented for the engineering DLST structures subjected to certain demolition external loads. [Display omitted] • A double-layer space truss (DLST) was tested under self-weight. • Non-contact videogrammetric technique was adopted in the displacement measurement. • Internal force redistributions of the tested DLST were explored. • Load-carrying mechanisms of the tested DLST were identified. • A progressive collapse demolition method for DLSTs was presented. [ABSTRACT FROM AUTHOR]

This paper presents a detailed investigation of the lateral characteristics of cold-formed steel truss structures used in electric power substations. Five full-scale specimens were tested, and their responses were recorded under monotonic and cyclic loading regimes. Of particular interest were the specimens' maximum lateral load capacities and deformation behaviours. A rational estimation of the seismic response modification factor, R, of the truss structures is also provided. In addition, different types of stiffened sections were employed in order to examine the impact of the presence of stiffeners and lips on seismic behaviour, as well as on the lateral resistance of the structure. Detailed comparisons between relevant code methods, finite element modelling and an experimental study were then conducted to suggest an appropriate value for the R factor. A financial evaluation was also performed, to highlight the advantages of employing cold-formed steel trusses in the electric power substation industry. The results show that the cold-formed steel structural system is a reasonable alternative to the currently used hot-rolled steel structures, and that its use decreases the cost of the structures by almost 50%. [ABSTRACT FROM AUTHOR]

This paper presents the results of theoretical and experimental investigations on the statistical size effect (SSE) of flexural members in steel. The chain of bundle model is developed, which is based on a stochastic material model by Weibull and lognormal distribution. Furthermore, this model is embedded into the finite element method (FEM) software for the analysis of a complicated structure with a stress gradient. In order to determine the stochastic material model parameters, uniaxial tensile tests were carried out based on specimens using the same steel with different sizes. By comparing the experimental and simulation results, the material parameters could be analyzed based on the relationship between the specimen sizes and strength. Moreover, the 3-point and 4-point bending tests were performed and simulated with the developed model. The experimental and simulation results demonstrate that the SSE also exists in the flexural member, and the equivalent yield stress is closely related to the stress distribution and volume of the structure component. [ABSTRACT FROM AUTHOR]

This paper presents the analytical behaviour of concrete-encased concrete filled steel tubular members (concrete-encased CFST members for short) under the combined effects of compression and torsion, which is a typical loading condition for structural members such as bridge piers under earthquake. A finite element model (FEM) is established to account for the complex material nonlinearity and interaction, accuracy of which is verified by a set of test data. Full range analysis of the composite members under combined compression and torsion is then presented. Typical failure modes are investigated, whilst the behaviour of RC and CFST components in the composite members are compared with those of individual RC members and CFST members under the same loading condition. Parametric analysis is carried out as well to evaluate the influence of significant factors, including the material strengths, arrangement of rebars, steel ratio of inner CFST component and CFST ratio. Torsion-compression relations of concrete-encased CFST are investigated. A simplified calculation method is validated using the simulation results in order to predict the torsional capacity of axially loaded concrete-encased CFST. [ABSTRACT FROM AUTHOR]

This paper presents a novel structural form of demountable beam-to-column composite bolted joints that can be dismantled at the end of its service life. An experimental programme was conducted to investigate the static and hysteretic behaviour of the demountable composite joints. The initial stiffness, moment capacity and failure modes of the demountable beam-to-column joints were evaluated through experimental results. The demountability of the joints was verified by dismantling the specimens during testing. Finite element models were developed, which incorporated the nonlinear contact interaction, ductile damage and plastic damage. The accuracy of the numerical models was validated with the relevant experimental outcomes. A parametric analysis was thereafter conducted to evaluate the effect of the end-plate thickness, width-to-thickness ratio of the column, bolt diameter and number of bolts on the moment-rotation response. A comparison between the test results and Eurocode was conducted to assess the applicability of the existing design guidance. It is found that the specimens designed with bent reinforcing bars exhibit satisfactory performance, and possess a higher level of hogging moment resistance compared to those with straight reinforcing bars. The designed joints are able to be dismantled readily and all steel components remain elastic when they are loaded up to 40% of the ultimate capacity which is equivalent to the typical service load. The end-plate thickness, width-to-thickness ratio of the column and bolt diameter impose the significant effect on the performance of the bolted joints. Two bolt-rows in tension can improve the moment-rotation response for the joints with extended end-plates. The current design standards are not capable of predicting the behaviour of the demountable beam-to-column joints accurately. [ABSTRACT FROM AUTHOR]

Popularity of Cold-Formed Steel (CFS) structures has recently increased considerably in the last years as a consequence of discovered advantages such as lightness of the material, significant energy absorption capacity providing seismic performance against lateral loading, time efficiency and cost effectiveness. CFS structures are composed of shear panels which involve cold-formed steel bare frames coated with different kind of sheathings such as gypsum wallboard (GWB), oriented strand board (OSB), plywood or some infill materials which are connected to the frame. Combination of CFS bare frames and sheathing boards provides the shear panels with lateral load resistance against seismic actions. There are several factors which have a direct influence on the behavior of CFS shear panels such as type of sheathing board, thickness of cold-formed steel, spacing of the screws binding the sheathing board to the bare frame and magnitude of the axial loads. On behalf of observing the impact of these outlined factors upon the behavior of CFS shear panels as well as to attain some experimental data to be utilized in the new Turkish Earthquake Code 2016, a considerable amount of laboratory tests was conducted in Structures Laboratory of Bogazici University on different configurations of CFS shear panels. Posterior to the acquisition of these experimental data, studies upon developing analytical models representing the actual experimental behavior of one of the shear panels have been conducted, thus providing possibilities for 3-D seismic performance assessment of a representative one-story cold-formed steel structure for the final part of this paper. [ABSTRACT FROM AUTHOR]

The paper presents an experimental investigation on the shear strength of self-piercing rivet connections used in thin-walled steel structures. The test program included specimen variations in the number of rivets in each connection, rivet spacing, end distance, and steel sheet thickness. According to the experimental results, the curve of load-slip, peak load, and failure mechanism for all specimens were analyzed. Parameters of riveting in terms of end distance, spacing, arrangement, length, and thickness difference between connection components were studied on their effects for shearing performances of self-piercing rivet connections. A design method based on the model of transmission dynamics of infectious diseases was proposed for calculating the shear strength of the rivet connections. The strength reduction due to the effect of group rivets was considered in the new method. [ABSTRACT FROM AUTHOR]

Steel concentrically braced frames (CBFs) are frequently used as efficient lateral load resisting systems to resist earthquake and wind loads. This paper focuses on high seismic applications where the brace members in CBFs dissipate energy through repeated cycles of buckling and yielding. Widely-used seismic provisions have somewhat different approaches for the seismic design of CBFs. The present study evaluates in detail the similarities and differences between the design philosophies and provisions used in the United States and Europe for these systems. The requirements of both provisions applied during a full design procedure are summarized and compared. Furthermore, X-braced, split X-Braced, and V-braced archetypes are designed accordingly and the differences in the design outcomes are investigated regarding section sizes and the weight of steel used in each design. Finally, inelastic structural models of the designed archetypes are developed and subjected to a large set of ground motions to study their seismic behaviors. The results of a total of 880 nonlinear time history analyses are then synthesized to investigate the way in which the requirements of these provisions affect the seismic behavior of the designed CBF. Notable differences are observed between the performances of the CBFs designed using American and European provisions. The similarities and differences as well as drawbacks of the provisions are thoroughly discussed. Recommendations and future research needs are suggested to enhance the seismic performance of steel CBFs designed according to these provisions. [ABSTRACT FROM AUTHOR]

The use of advanced analytical and numerical modelling in structural engineering has increased rapidly in recent years. A key feature of these models is an accurate description of the material stress-strain behaviour. Development of standardised constitutive equations for the full engineering stress-strain response of hot-rolled carbon steels is the subject of the present paper. The proposed models, which offer different options for the representation of the strain hardening region, feature an elastic response up to the yield point, followed by a yield plateau and strain hardening up to the ultimate tensile stress. The Young's modulus E , the yield stress f y and the ultimate stress f u are generally readily available to the engineer, but other key parameters, including the strains at the onset of strain hardening and at the ultimate stress, are not, and hence require predictive expressions. These expressions have been developed herein and calibrated against material stress-strain data collected from the literature. Unlike the widely used ECCS model, which has a constant strain hardening slope, the proposed models, reflecting the collected test data, have a yield plateau length and strain hardening characteristics which vary with the ratio of yield to ultimate stress (i.e. with material grade). The proposed models require three basic input parameters ( E , f y and f u ), are simple to implement in analytical or numerical models, and are shown herein to be more accurate than the widely employed ECCS model. The proposed models are based on and hence representative of modern hot-rolled steels from around the world. [ABSTRACT FROM AUTHOR]

This paper is Part 2 of a two-part investigation of the structural fire resistance of a partially composite, one-way spanning steel floor beam assembly with partial translational and rotational end restraint provided by shear tab connections to a supporting frame. A preceding paper (Part 1) described a pair of experimental tests on structurally identical composite floor specimens (one protected and the other unprotected) that are subjected to fire via a large modular furnace. In this paper, those experimental results are used to validate numerical models that conservatively capture the thermo-mechanical response of the specimen assemblies to fire. Models are developed to maximize simplicity toward implementing performance-based design of these assemblies in practice. Thermal analysis of the steel is performed using a multiple lumped mass approach, which can be implemented via spreadsheet or a simple, non-iterative programmed solution. Thermal analysis of the slab via a simple one-dimensional heat flow model is compared against a more detailed computational solution. Two types of structural finite element analyses were performed: one composed of shell elements (more complex) and another composed of fiber-beam elements (simpler). The results of all models show conservative agreement with the experimental data. These models are used to analyze the tested assemblies for variations in applied load and fire protection thickness to demonstrate the utility of the ASTM E119 standard fire test as a validation baseline for performance-based structural fire engineering evaluation. • 2 structurally identical composite floor beams are modeled for fire exposure. • Passive fire protection was applied to one specimen, and the other was unprotected. • Simple calculations conservatively predicted experimental temperature measurements. • Complex & simple predictions of structural behavior are validated with test results. • Models are used to examine variations in flexural loading and protection thickness. [ABSTRACT FROM AUTHOR]

By leveraging the merits of structural steel and concrete materials, concrete-filled steel tubular (CFST) structures have been increasingly used in the composite construction of bridges and high-rise buildings. However, their design equations are more complicated than those of steel and reinforced concrete (RC) structures, especially for circular columns under eccentric loading. Therefore, the use of emerging data-driven approaches will help structural engineers ease the design process. This paper explores the use of data-driven design methods as alternatives to conventional mechanics-based design models. Five boosting algorithms, including adaptive boosting (AdaBoost), gradient boosting machine (GBR), extreme gradient boosting (XGBoost), light gradient boosting machine (LightGBM), and categorical gradient boosting (CatBoost), are employed to develop predictive models for four different types of CFST columns (i.e., circular columns, rectangular columns, circular beam–columns, and rectangular beam–columns). These predictive models are trained using the most up-to-date and comprehensive database collected from over 3,200 test specimens. Reliability analysis is conducted to calibrate the resistance reduction factors for three different design frameworks (i.e., the US, Eurocode, and Australian frameworks) to ensure that the newly developed predictive models meet the target reliability indices required by different design frameworks. A web-based design tool is also developed to promote the practical use of data-driven methods for the design of CFST columns. • ML models for predicting the resistance of CFST columns and beam–columns were created. • The models were based on five boosting algorithms and a 3,208-test database. • The models outperformed the design provisions of AISC 360, EC 4, and AS/NZS 2327. • Resistance factors were determined from reliability analyses for three design frameworks. • A web application based on the ML models was created and deployed to the cloud. [ABSTRACT FROM AUTHOR]

The most common wind tower structure, a tapered tubular steel monopole, is currently limited to heights of ~ 80 m due to transportation constraints which arise because tower sections are manufactured at centralized plants and transported to site for assembly. The need to transport the sections imposes a limit on their size, whereby maximum tower diameters are dictated by bridge clearances rather than by structural efficiency. New manufacturing innovations, based on automated spiral welding, may enable on-site production of wind towers, thereby precluding transportation limits and permitting the manufacture of taller towers, which can harvest the steadier, stronger winds at higher elevations. Taller towers, however, are expected to have cross-sections with slenderness that is uncommon in structural engineering (i.e., diameter-to-thickness ratios up to ~ 500) and much larger than those of conventionally manufactured towers (i.e., diameter-to-thickness ratios up to ~ 300). Tubular structures with highly slender cross-sections are imperfection-sensitive, and the welding process is known to influence imperfections. To account for this sensitivity, slender tubes are usually designed based on empirical knockdown factors, however there are few experiments of tubes in flexure with slenderness as high as what is expected for spirally welded wind towers, and there are no experiments on tubes within this slenderness range and manufactured with spiral welding. This paper reviews the state-of-the-art for designing spirally welded tubes as wind towers and identifies deficiencies. Relevant experimental and analytical research is summarized and research needs to efficiently design tapered spirally welded steel tubes as wind towers are identified. [ABSTRACT FROM AUTHOR]

Concrete-filled steel tubular (CFT) columns are widely used as columns in many structural systems and a common failure mode of such tubular columns is inelastic outward local buckling near a column end. The use of fibre-reinforced polymer (FRP) jackets/wraps for the suppression of such local buckling has recently been proposed and has been proven to possess excellent potential in both retrofit/strengthening and new construction. This paper presents the results of an experimental study into the behaviour of large-scale FRP-confined CFT (CCFT) columns under combined axial compression and lateral loading. The test parameters included the stiffness of the FRP jacket and the loading scenario. The test results showed that the FRP jacket can effectively delay or even prevent outward local buckling at the end of a cantilevered CFT column, leading to significantly improved structural performance under combined constant axial compression and cyclic lateral loading. Compared to monotonic lateral loading, cyclic lateral loading was found to introduce more severe localized deformation near the column end and may lead to earlier FRP rupture within that region. [ABSTRACT FROM AUTHOR]

This paper investigates the structural behaviour of Steel-Concrete-Steel (SCS) sandwich wall which consists of two external steel plates infilled with ultra-lightweight cementitious composite material. A series of compression tests consists of a wide range of parameters have been carried out on the SCS sandwich walls of different heights forming short and slender wall. The test results show that the SCS sandwich walls with J-hook connectors exhibit comparable behaviour in compressive resistance and post-peak unloading behaviour to the ones with the overlapped headed studs. The interlocking J-hook connectors play an important role in providing composite action between the steel plates and the cementitious core, and preventing or delaying the local buckling of the external steel plates. The test results are compared against the predictions by Eurocode 4 and AISC 360 methods for composite columns. It is found that the Eurocode 4 and AISC 360 methods could over-predict the compressive resistance of sandwich wall subjected to compression. A modified method is then proposed, which takes into account the effect of interlocking J-hook connectors in providing lateral restraints to the external steel plates. The predictions show a reasonable correlation with the test results. Nonlinear finite element model has been established to predict the load-displacement curves, maximum resistance and failure modes of the sandwich walls. Both the experimental and finite element results confirm that the proposed analytical formulae are conservative for design of SCS sandwich composite walls with J-hook connectors. [ABSTRACT FROM AUTHOR]

High-strength steel (HSS) is gaining widespread acceptance in contemporary engineering structures, with grades of up to 690 MPa being included in many design standards. However, although strength grades well in excess of 690 MPa are possible with modern metallurgical processes, these are not compliant with most design codes of practice. HSS is advantageous when strength, rather than stiffness, predominates the structural response. When this is the case, HSS is very useful in reducing the self-weight of the structure, as many be needed in structural modification, or in contriving a design that minimises the carbon footprint of the structure. Research on the flexural-torsional buckling of steel structures is extremely abundant in the literature, and guidance in codes is very comprehensive. It is known that the resistance to flexural-torsional buckling depends on the interaction of (i) elastic buckling; (ii) yielding and post-yielding and (iii) residual stresses. Current design curves are based on the elastic buckling resistance, which is modified to account for the yield and post-yield response of structural steel and the residual stresses in the cross-section. However, HSS with yield stresses exceeding 690 MPa have somewhat different yield and post-yield characteristics and significantly different patterns of residual stresses when compared with structural steel. This paper uses ABAQUS software to investigate the flexural-torsional buckling strength of HSS I-section beams, by incorporating the stress-strain curves and residual stresses measured experimentally and reported in the literature. With a similar methodology to structural steel members, the interaction of elastic buckling at the member level with the material characteristics at the cross-sectional level is investigated and a strength design formulation is proposed. [ABSTRACT FROM AUTHOR]

High strength steels (HSSs) are increasingly applied in structural engineering due to their benefits in terms of mechanical performance and economy. Compared with normal strength steel (NSS) axial compression members, HSS members possess more critical local buckling behavior since its component plates may be designed as being more slender, and different mechanical properties of HSS, in terms of increased yield strength and reduced ductility, may result in different local buckling behaviors. In this paper, finite element (FE) analysis is performed to investigate the local buckling behavior of welded box section and I-section stub columns under axial compression with both NSS and HSS being incorporated, where initial geometric imperfections and welding-induced residual stresses are accurately simulated. Through this work, variation rules of post-buckling ultimate stress and local buckling stress of the axial compression members with steel yield strength and width-to-thickness ratio are clarified. By comparing the FE analysis results and existing test results with the corresponding design methods in ANSI/AISC 360-10, Eurocode 3 and GB 50017-2003, it is confirmed that the design methods for the local buckling behavior of welded box section and I-section stub columns under axial compression need to be modified. New design formulas are proposed to take the influence of the steel strength into consideration. [ABSTRACT FROM AUTHOR]

Circular hollow sections (CHS) are widely used in a range of structural engineering applications. Their design is covered by all major design codes, which currently use elastic, perfectly-plastic material models and cross-section classification to determine cross-secti\on compressive and flexural resistances. Experimental data for stocky sections show that this can result in overly conservative estimates of cross-section capacity. The continuous strength method (CSM) has been developed to reflect better the observed behaviour of structural sections of different metallic materials. The method is deformation based and allows for the rational exploitation of strain hardening. In this paper, the CSM is extended to cover the design of non-slender and slender structural steel, stainless steel and aluminium CHS, underpinned by and validated against 342 stub column and bending test results. Comparisons with the test results show that, overall, the CSM on average offers more accurate and less scattered predictions of axial and flexural capacities than existing design methods. [ABSTRACT FROM AUTHOR]

In recent years, researchers study alternative connection designs for steel seismic-resistant frames by reducing the beam section in different ways including that of creating an opening in its web (RWS connections). A similar design is applied in the fabrication of perforated (i.e. cellular and castellated) beams mostly used to support the service integration, as well as the significant mass reduction in steel frames. This paper presents a comprehensive finite element (FE) analysis of extended end-plate beam-to-column connections, with both single and multiple circular web openings introduced along the length of the beam while subjected to the cyclic loading proposed by the SAC protocol from FEMA 350 (2000). The three-dimensional (3D) FE solid model was validated against FE and experimental results and the chosen configuration was capable of representing the structural behaviour of a partially restrained connection, without the necessity to be idealised as fully fixed. The study focuses in the interaction of such connections and the mobilisation of stresses from the column to the perforated beam. The parameters introduced were the distance from the face of the column, S, and the web opening spacing, S o , with closely and widely spaced web openings. It is found that RWS connections with cellular beams behave in a satisfactory manner and provide enhanced performance in terms of the stress distribution when subjected to cyclic loading. The design of partially restrained RWS connections should be primarily based on the distance of the first opening from the face of the column. [ABSTRACT FROM AUTHOR]