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This study examined the hysteretic behaviour of Square Hollow Section (SHS) T- and X-joints subjected to cyclic in-plane bending moments. A nonlinear finite element software, Abaqus, was used to investigate SHS T- and X-joint seismic performance. Prior to the parametric study, the numerical model was validated based on the available test results in the literature. A comprehensive parametric study employed validated finite element models to evaluate the influence of critical geometric parameters, including the brace-to-chord width ratio (β) and the chord width-to-thickness ratio (γ). The results of the finite element analyses regarding ductility, flexural strength, and energy dissipation behaviour of SHS T- and X-joints under quasi-static cyclic in-plane bending were evaluated. Based on the hysteretic curves, increasing β generally leaded to higher initial stiffness and moment capacity in SHS joints, considerably reducing joint rotation. Conversely, the joints with larger γ exhibited reduced initial stiffness and moment capacity. Besides, the Eurocode 3 EN1993-1-8 predictions for the ultimate flexural strength of the joints are found to be conservative compared to finite element results. The results also revealed that the SHS T- and X-joints showed satisfactory ductility levels under in-plane bending load. It was observed that the SHS T- and X-joints with high β and low γ are advantageous for absorbing energy under seismic loads. These findings offered valuable insights for the seismic-resistant design of structures incorporating SHS joints, aiding in selecting optimal configurations based on specific performance requirements. • This paper presents a numerical study of hysteretic behaviour of SHS T- and X-joints with IPBM. • An increase in β ratio generally corresponded to higher initial stiffness, moment capacity, ductility. • The joints with large γ ratio exhibited reduced initial stiffness, moment capacity and ductility. • Eurocode 3 predictions were conservative in estimating the ultimate flexural strength of the SHS T- and X-joints under IPBM. • SHS T- and X-joints with high β and low γ were advantageous for absorbing energy under seismic loads. [ABSTRACT FROM AUTHOR]

Composite shear walls are usually employed at the bottom of super high-rise structures to resist large axial forces, bending moments, and shear forces. A lot of investigations have been carried out on composite shear walls, but there are fewer comparative studies on composite shear walls with different steel layouts. In this paper, low cyclic horizontal loading tests were carried out on conventional reinforcement concrete shear walls and composite shear walls with different steel layouts (H-section steel in boundary members and the steel plate in the shear wall web, H-section steel in boundary members and the slotted steel plate in the shear wall web, evenly arranged H-shaped steel in the wall). Comparative analyses of load-carrying capacity, failure modes, and seismic performance were conducted. The effects of different steel layouts on the seismic performance of composite shear walls were investigated. Based on the tests, the finite element method is used to further analyze the influence of the shear span ratio of the shear wall and the opening rate of the built-in slotted steel plate. • Low cyclic horizontal loading tests were carried out on conventional reinforcement concrete shear walls and composite shear walls with different steel layouts. • The effects of different steel layouts on the seismic performance of composite shear walls were investigated. • The parametric analysis of the composite shear walls with different steel layouts was conducted based on numerical simulation. [ABSTRACT FROM AUTHOR]

In this study, a Finite Element (FE) model of locally strengthened high-strength stainless-steel tube subjected to lateral impact loads is established using LS-DYNA to investigate its dynamic behaviours. The accuracy of the FE results is verified by comparing with the test results. The impact force, bending moment, stress and strain responses as well as the internal energy dissipation histories of the strengthened tube are analysed during the entire impact process. The results indicate that the impact resistance of the strengthened tube is obviously enhanced as compared to hollow stainless-steel tube. Furthermore, parametric studies are conducted to reveal the influence of axial compressive force, impact position, impact velocity and material strength on the impact behaviour of the strengthened tube. The results show that the application of axial compressive force reduced the impact force and increased the deformations of the strengthened tube. The impact resistance of the strengthened tube performed an increasing trend when moving the impact position towards the support and increasing the material strength. In addition, the increase of impact velocity significantly reduced the impact duration. Finally, design recommendations and process were proposed to facilitate the application of locally strengthened tube. • The impact response of locally strengthened stainless-steel tube was numerically studied. • The impact force, bending moment, stress and strain response and energy dissipation were analysed. • Concrete was found to dissipate more impact energy than the other parts. • The effects of variant parameters on impact performances of the strengthened tubes were investigated. [ABSTRACT FROM AUTHOR]

The bending mechanical properties of FRP-confined square concrete-filled steel tubes (CFST) reinforced with internal latticed steel angles, including the failure modes, characteristic curves and characteristic mechanical parameters of tested specimens, were investigated through experiments in this paper. The bending mechanisms were also analyzed using an established finite element model, including the analysis of the bending moment borne by each component, the distributions of contact pressure between different components at the mid-span section, and the distributions of the neutral axis under the bending capacity. The key influential parameters, including the tensile strength and thickness of the FRP, were also examined. The results indicate that the FRP has almost no influence on bending stiffness, however, it enhances the yield bending moment and bending capacity to a certain extent. It was also found that the enhancement decreases as the width of steel tube increases, and the influence of FRP is more profound before reaching the peak load. The calculation formulas for the bending capacity were developed using the superposition method and numerical fitting method. Analysis of their accuracy shows that the formulation using the superposition method yields relatively accurate and safe prediction results, with the prediction errors of less than 20 %. • The bending behavior of FRP-confined square CFST reinforced with internal latticed steel angles is investigated through experiment; • A method for characterizing the yield bending moment and bending capacity of the tested specimens is proposed; • The bending mechanisms are analyzed using an established finite element model; • The calculation formulas for the bending capacity are proposed based on the superposition method and numerical fitting method. [ABSTRACT FROM AUTHOR]

The present paper reports results of a numerical investigation of the mechanical behavior of a column base plate connection subjected to an axial compression force and a bending moment. A three-dimensional nonlinear model was developed, using the Cast3M software, and validated against experimental data. In addition, the material nonlinearity as well as contact conditions between the different components of the connection were thoughtfully considered. Based on the validated model, an extensive parametric analysis was conducted to investigate the effect of stiffeners on the forces in the anchor rods. The results clearly indicate that the design approaches that consider only the tensile strength of anchor rods while neglecting the bending moments can lead to a poor estimation of the forces applied to these rods. They also suggest that adding stiffeners provides additional strength and reduces the anchor rod bending in one direction. However, it is important to note that the stiffeners also induce an additional moment in the opposite direction. This could make the anchor rod more susceptible to biaxial bending with tension. Furthermore, this study proposes a new specific shape of stiffener is suggested (c bp5). It was concluded that the proposed shape of stiffeners allows a more uniform distribution of forces and avoids excessive stress concentrations, effectively prevents the biaxial bending in the anchor rod. [Display omitted] • 3D FE model is developed to analyze column base plate connection behavior. • Eurocode 3 overestimated anchor rod strength by neglecting bending moment. • Stiffeners induced biaxial bending on anchor bolts in stiffened connections. • Proposed stiffener shape prevented biaxial bending of anchor rods. • Compression center position influenced by the stiffeners and their shapes. [ABSTRACT FROM AUTHOR]

In this study, the buckling behavior of cold-formed beam-column members with sigma and lipped channel sections under the combined effect of axial load and biaxial bending moment (P-M x -M y) was compared. A total of 30 specimens (15 with sigma sections and 15 with lipped channel sections), each measuring 1500 mm in length, were tested under monotonic loading. The performances of the specimens under eccentric loading such as strength and energy absorption capacity were investigated experimentally and numerically. The local, distortional and global buckling modes that determine the bearing capacity of the section and the length of the sigma and lipped channel member where all these buckling modes can be seen were determined. Finite element analysis (FEA) was performed with Abaqus software, and the numerical results were verified against experimental results. Using the validated finite element model, a comprehensive parametric study was carried out by performing 2894 FEA on sigma and lipped channel section members with various cross-sectional dimensions and lengths. Experimental results show that there are significant differences in load bearing capacity, energy absorption capacity and buckling modes of sigma and lipped channel section members. In the FEA/ AISI-S100 code comparison made at the end of the parametric study, it was determined that differences occurred according to the lengths, cross-sectional properties and loading points of the members. It was determined that the error rate was safer when the lips were subjected to tensile stresses than when they were subjected to compressive stresses. Finally, it was determined that the FEA/AISI-S100 error rate decreased as the length of the sigma-section members increased. • The experimental behavior of sigma and lipped channel sections was investigated under the combined actions of axial load and biaxial bending. • The buckling behavior of sections was determined through a comprehensive parametric study. • The experimental and numerical results were discussed. • Results were compared with AISI-S100 standard. [ABSTRACT FROM AUTHOR]

Reported studies on T-head Square-neck One-side Bolts (TSOBs) bolted I-beam to Hollow Section Square Column (HSSC) connections demonstrated the potential of TSOB applications in terms of mechanical properties, installation construction, and cost savings [11–14]. However, existing research was limited to the connection tests and lack a systematic and complete design approach. In this paper, the method for predicting the bending moment capacities and failure modes of the connections was proposed based on the existing test researches. Besides, the Finite Element Model (FEM) of the connections was established and validated by the reported test results. A sensitive analysis on the geometric parameters of the plastic hinge line pattern for calculating the bending moment capacity of the HSSC connecting face was carried out by the validated FEM. The proposed method was compared with the numerical simulation method in terms of the predicted results of the connection structural behavior. The results show that the prediction method proposed in this paper for the connection bending moment capacities and failure modes is accurate and reliable. Moreover, the mixed patterns of Type-H bolt holes and Type-V bolt holes are recommended for the TSOBC design because of the higher bending moment capacity than the unitary bolt hole patterns. • Method for predicting the bending moment capacity of TSOBC was proposed. • Failure mode of TSOBC was predicted based on design information. • Mixed patterns of Type-H and Type-V bolt holes are recommended for TSOBC. [ABSTRACT FROM AUTHOR]

Based on the zig-zag theoretical model of corrugated steel web beam (CSW), the governing equations in the form of state equations are derived and their analytical solutions are obtained for different loads, variable cross-sections and boundary conditions. Through numerical examples, it is verified that the bending moment, deflection and stresses predicted by the present analytical method have a good agreement with the results of the three-dimensional finite element model. The applicability of the present method for non-prismatic continuous beams with CSWs under different loads is also demonstrated. Meanwhile, it is found that the quasi-plane assumption is still valid in non-prismatic continuous beams with CSWs. Through quantitative analysis of the flexural stresses in the top and bottom slabs, it is confirmed that the zig-zag theory in this study can well reflect the accordion effect of CSWs. Because of the inclined bottom slabs in the non-prismatic beams with CSWs, the Resal effect on the shear stresses in the CSWs and bottom slabs, which is caused by the vertical component of the axial force in the bottom slab, is discussed. A refined shear formulation is developed for more accurate shear stresses in the CSWs and bottom slabs, which provides fundamental theoretical support for the strength prediction of the non-prismatic beam with CSWs. • The zig-zag theory is developed for the non-prismatic beams with CSWs based on the state space method. • The quasi-plane assumption is still valid in non-prismatic continuous beams with CSWs. • The refined shear formula considering Resal effects is derived for the CSW beam with inclined bottom slab. [ABSTRACT FROM AUTHOR]

This paper presented a series of tests to investigate the behaviour of the extended end-plate connection utilizing high strength Q960 steel. A total of 8 specimens were tested, including two under ambient temperature and three under high temperature. The results of the tests indicated that increasing the end-plate thickness from 8 mm to 12 mm significantly enhances the flexural capacity and initial rotational stiffness of the connections but reduces the critical temperature and ultimate rotation. In addition, a higher beam bending moment ratio was found to increase the ultimate rotation of the connections while having minimal impact on the critical temperature. Then, the finite element model of the connections was established to investigate the parametric effect, including column axial pressure ratio, beam bending moment ratio, and end-plate thickness on fire resistance. The numerical analysis indicated that increased column axial pressure ratio and end-plate thickness decreased fire endurance, critical temperature, and ultimate rotation of the connections. On the other hand, increasing the beam-bending moment ratio enhanced the ultimate rotation of the connections. Lastly, a rotation-temperature relationship model was proposed to accurately predict the temperature-rotation curve of high-strength steel Q960 end-plate connections, which was validated with experimental data. • Fire tests on response of high strength Q960 steel connections were carried out. • Numerical models were developed to simulate the behaviour of Q960 teel connections at elevated temperatures. • Parametric studies were performed to investigate the effect of key factors on fire resistance of the connections. • A rotation-temperature relationship model was proposed to predict the fire behaviour of Q960 steel connections. [ABSTRACT FROM AUTHOR]

In this paper, a pinned scaffolding node is proposed and studied with Q355 steel and sorbite stainless steel. Twelve sets of forward and reverse bending tests were designed to study the bi-directional bending performance at temperatures of +20 °C, −20 °C, and − 40 °C. The test results show that as the temperature decreases, the initial rotational stiffness and bearing capacity of the QSJ and the SSSJ both increase. Under the same temperature conditions, the yield bearing capacity and maximum bearing capacity of the SSSJ are greater than those of the QSJ. However, the SSSJ is susceptible to cracking in the weak zone of the C-shaped member subjected to forward bending moments in low-temperature environments, which requires attention in design and use. A finite element model can accurately simulate the bi-directional bending performance of the joint. The results show that increasing the thickness of the U-shaped members by 1–1.5 mm significantly increases the maximum load capacity of the joint. The wall thickness of the pipe has no influence on the bending properties of the joint, but the initial stiffness of the joint can be increased by the depth of wedging, a wall thickness of 6 mm is recommended for C-members. The form of damage to the SSSJ can be improved by increasing the curvature of the upper edge of the C-member at the wedge. The results of this paper can provide methods and references for the engineering design of scaffolding as well as for testing in low-temperature environments. • This paper adopts the separated low temperature loading device, which is convenient for the installation and disassembly. • This study presents a low-temperature loading test device and method. It can provide a test environment of −70 °C ∼ 150 °C. • It's innovative to study the material properties of cable body stainless steel and Q355 at −40 °C, −20 °C and room temperature. • The mechanical properties of the pin-type scaffolding nodes using sorbite stainless steel and Q355 at low temperature were investigated. [ABSTRACT FROM AUTHOR]

This paper investigates experimentally and numerically the behaviour of a balcony-to-slab connection made by an H-profile embedded in the concrete slab. A large-scale test was performed on a specimen of the connection system in order to determine the moment-bearing capacity, the deformation behaviour, the cracking patterns, the distribution of the bending moment along the axis of the embedded steel H-profile as well as the failure mode of the connection system. The test results showed that the failure mode was governed by the concrete shear of the slab. In addition, a 3D finite element model of the experimental test was also carried out and successfully validated against the experimental results. For a practical design of the connection system, a model based on Timoshenko beam on elastic foundation (BEF) was investigated and verified against the results obtained from the validated FE model. The Winkler modulus of the BEF model was determined by considering the local deformation of the concrete based on a strut-and-tie model. The results demonstrate that the BEF model with this value of the Winkler modulus provides a conservative estimation of the shear and bending forces applied to both the embedded H-profile and the concrete cross-sections. This method is a first tentative design basis using linear elastic theory for such a system. • Experimental and numerical investigation on the behaviour of embedded H-profile balcony-to-slab connection • A BEF model is proposed to determine the distribution of shear and bending forces on embedded steel profile and concrete. • Winkler modulus is determined by considering the local deformation of the concrete based on a strut-and-tie model. [ABSTRACT FROM AUTHOR]

This paper presents an evaluation of the design rules for the bending moment–shear force (M − V) interaction of cold- and hot-formed square, and rectangular hollow steel sections (SHS & RHS). More specifically, the design rules, as provided by EN1993-1-1 regarding RHS and SHS of section class 1 and 2 are covered for the steel grades S235 up to and including S460. A 4-point bending test was simulated by means of a finite element model, which was validated on the basis of experimental tests from existing literature. A parametric study was performed and numerical M − V interaction results were compared to the provisions in EN1993-1-1. This comparison indicates that the current design rules in EN1993-1-1 regarding M − V interaction are conservative and overestimate the reduction of the bending resistance due to the presence of shear. Alternative design rules for the shear area and M − V interaction of RHS and SHS are proposed and evaluated by means of a statistical assessment procedure based on existing literature and EN1990-1-1. Both newly developed design rules are shown to ensure an adequate reliability level when a partial safety factor equal to 1 is used. • Evaluation of the design rules for the M − V interaction of RHS and SHS. • An alternative design rule is proposed. • The proposed shear area matches the numerical results for all tested sections. [ABSTRACT FROM AUTHOR]

The assembling rivet-fastened rectangular hollow flange beam (ARHFB) is a new type of cold-formed steel beam. The ARHFB section has two rectangular hollow flanges formed by U-shaped and C-shaped components that connected by self-locking rivets. A finite element model is developed to simulate 16 four-point bending experiments. Details of the modeling including finite element meshing, loading and boundary conditions, contact and analysis methods are presented. The accuracy of the developed finite element model is verified by comparing the ultimate moment capacity, applied load versus deflection curves, bending moment versus deflection curves, strain versus deflection curves and failure modes obtained from the tests and the finite element analysis. Based on the validated finite element model, a parametric analysis is carried out to discuss the effects of rivet spacing, section depth, flange thickness, and web thickness on the bending performance of ARHFB. The moment capacities of these sections obtained from the parametric study are compared with predictions from Australia and New Zealand, Chinese design standards for cold-rolled sections and the DSM (Direct Strength Method). It is found that GB50018 can conservatively predict the bearing capacity of ARHFB with a large error, while AS / NZS 4600 and DSM (Direct Strength Method) cannot provide reliable prediction results. • A novel assembling rivet-fastened rectangular hollow flange beam (ARHFB) is analyzed in finite element model. • An extensive parametric investigation using a verified finite element model is conducted. • The feasibility of current design codes for ARHFBs is evaluated and judged. [ABSTRACT FROM AUTHOR]

This study presents experimental and numerical research on the dynamic behaviors and resistances of square concrete-filled steel tubular members internally strengthened by I-shaped CFRP profile (SCFST-CFRP) with fixed boundary conditions subjected to lateral impact loads. Dynamic impact tests were conducted on five SCFST-CFRP specimens and a traditional concrete-filled steel tubular (SCFST) specimen, examining their dynamic responses with respect to deformation modes, impact force, displacement, and strain distribution at different levels of impact energies and impact momentums. The test results indicated that the deformation of the specimens was concentrated in the impact region, approximately 0.38 L above the base, due to the transient localized characteristics of the lateral impact load. In terms of displacement and impact force, the SCFST-CFRP member exhibited better impact resistance compared to the SCFST member. Finite element models of the SCFST-CFRP members were created using LS-DYNA and validated against the impact tests. These validated models were then utilized to explore the damage patterns, dynamic bending moment, and load transfer mechanism of the SCFST-CFRP member under lateral impact loading. Additionally, a parametric study was conducted to evaluate the effects of load and structural parameters, including CFRP profile, impact energy, and impact momentum, on the impact resistance and dynamic flexural capacity of the SCFST-CFRP member. The results demonstrate that the enhancement in impact resistance caused by the inner CFRP profile was more significant under higher impact energy. Based on the parametric analysis results, empirical equations were proposed to predict the dynamic flexural capacity of lateral impact-loaded SCFST-CFRP members. • Impact tests of CFST member strengthened with CFRP profile under fixed boundaries. • Evolutions and distributions of deformation and internal force were summarized. • Impact load transfer mechanisms of the composite member were revealed. • Effects of load and structural parameters on the impact resistance were evaluated. • An equation for the dynamic flexural capacity of the composite member was proposed. [ABSTRACT FROM AUTHOR]

Over the past decade, the previous hysteretic recognition of the fire threat to bridges has provoked significant progress in understanding the fire performance of bridges. However, despite the growing maritime shipment of combustibles, scarce studies have contributed to evaluating the safety of steel cable-stayed bridges subjected to under-girder ship fires. Limited existing knowledge is still based upon the less precise temperature curve method and flame geometry modeling. This study developed an advanced numerical method to more accurately evaluate the response of steel cable-stayed bridges subjected to ship fires. First, the computational fluid dynamics (CFD) approach was used to reproduce realistic fire conditions. An efficient thermal boundary, adiabatic surface temperature, was then transferred to the thermal finite element model of affected girder segments for calculating the temperature propagation. Lastly, this paper used the multiscale structural finite element method to incorporate the local performance variation of exposed girders into the response of the entire bridge. The proposed method was validated by predicting a thermomechanical response of the steel beam exposed to realistic underneath fires, agreeing well with the data from two large-scale structural fire experiments by NIST. Based on the method, the response of a typical steel cable-stayed bridge subjected to ship fires was simulated. Results show that fires can introduce local damage to the girder segments above the fire and alter the internal force distribution of the entire bridge. The bending moment of the girder sections over the fire significantly increases, and the flexural characteristic of pylons is also altered. Both thermal convection and radiation contribute to the temperature increment, and the latter dominates at the locations above fires. Adopting temperature curves can overestimate or underestimate the fire impact, introducing uncertainties to the safety of steel cable-stayed bridges in ship fires and can cause unrealistic stress concentration on the border of heated and unheated domains of exposed floors. The developed advanced method is more competent in capturing the inhomogeneous temperature and stress distribution. • CFD fire models were coupled with FEM for steel cable-stayed bridges in ship fires. • Thermal radiation governs the heat absorbed by the girder floor exposed to ship fires. • Temperatures of the girder floor propagate from the central region to the periphery. • Ship fires bring local damage to the girder and alter the entire structural behavior. • CFD-FEM method is more competent than traditional temperature-curve methods. [ABSTRACT FROM AUTHOR]

Plate-reinforced composite (PRC) coupling beams are manufactured by embedding a vertical steel plate into conventionally reinforced concrete coupling beams to enhance their strength and ductility. This study presents a series of quasi-static tests conducted to examine the seismic behavior of PRC coupling beams and provide a scientific basis for the analysis of the shear bearing capacity of PRC coupling beams. The experimental results of seven PRC coupling beam specimens with low span-to-depth ratio tested under reversed cyclic loading are discussed. Particle image velocimetry technology is used to accurately measure the deformation performance of PRC coupling beams. The influence of span-to-depth ratio, sectional steel plate ratio, and the slab on the seismic behaviors of specimens were investigated. The experimental results indicate that, compared with PRC coupling beams without slab, PRC coupling beams with slab can increase horizontal cracking displacement and significantly improve the shear capacity and energy dissipation capacity of PRC coupling beams without slab. Embedded steel plates can improve the limited values of the shear compression ratio of coupling beams. Nonlinear finite element analysis was also carried out to model the PRC coupling beams. The numerical results indicate that the tension-softening property of concrete was more accurately simulated by the stress-crack width relationship of concrete. The internal force distribution of concrete stress, steel plate shear force, bending moment, and axial force of PRC coupling beams with low span-to-depth ratios were further analyzed. This study will benefit engineers designing PRC coupling beams. • The limited values of the shear compression ratio of coupling beams were significantly improved. • Particle image velocimetry technology is used to accurately measure the deformation performance of PRC coupling beams. • The PRC coupling beam with slab has a greater energy dissipation capacity. • The steel plate along the beam span was under tension, and the distribution of the tension is in M-mode. [ABSTRACT FROM AUTHOR]

Abstract The local cross-section behaviour of stainless steel channel sections under the combined actions of axial compression and minor axis bending moment is investigated in the present paper and its companion paper, based on a comprehensive experimental and numerical study. Two channel section sizes were considered in the experimental programme, with the test specimens laser-welded at the two flange-to-web junctions from hot-rolled EN 1.4307 and EN 1.4404 austenitic stainless steel plates. The experiments involved initial local geometric imperfection measurements and 15 eccentrically loaded stub column (combined loading) tests. The loading eccentricity was varied to achieve a range of ratios of axial compression to minor axis bending moment; both orientations of bending (web in compression and web in tension) were considered. The test setup and procedures, together with the key experimental observations, including the load-carrying and deformation capacities, load-end rotation histories and failure modes, are fully reported. A finite element simulation study is then presented, in which the models were first validated against the obtained test results and then employed, in the companion paper, for parametric investigations and the assessment of design provisions. Highlights • Laser-welded stainless steel channel sections under combined compression and minor axis bending moment has been studied. • An experimental programme including 15 combined loading tests has been carried out. • Finite element models have been developed and validated against experimental results. [ABSTRACT FROM AUTHOR]

Abstract Following the experimental study and finite element (FE) model validation described in the companion paper, numerical parametric studies and the evaluation of design provisions for stainless steel channel sections under combined axial compressive load and minor axis bending moment are presented herein. The parametric studies were carried out to generate additional structural performance data over a wider range of cross-section aspect ratios and slendernesses, loading combinations and bending orientations. The test data and numerical results have been carefully analysed to develop a comprehensive understanding of the structural performance of stainless steel channel sections under combined compression and minor axis bending moment, and to assess the accuracy of the existing design provisions in Europe and North America. Comparisons of ultimate loads from the tests and FE simulations with the codified resistance predictions revealed that the current design standards typically under-estimate the capacity of stainless steel channel sections under combined compression and minor axis bending moment; this is attributed primarily to the neglect of material strain hardening and the employment of conservative interaction formulae. Improved design rules featuring more efficient interaction curves, anchored to more precise end points (i.e. cross-section resistances under pure compression and bending moment), are then proposed and presented. The new design proposals are shown to yield both more accurate and more consistent resistance predictions over the existing design provisions. Finally, statistical analyses are presented to confirm the reliability of the new design proposals according to EN 1990. Highlights • Parametric studies were carried out to generate further structural performance data. • Design provisions in EC3 and AISC were assessed against test and FE data. • New proposals were made, leading to substantial improvement in resistance prediction. • The reliability of the new proposals was confirmed according to EN 1990. [ABSTRACT FROM AUTHOR]

This paper aims to experimentally and numerically investigate the structural performance of speed-lock joints with split bolts in steel storage racks. There are no bolts in the typical speed-lock joint for its ease of installation, and the joint transmits and bears force through interactions of the tabs and upright beam holes. However, the joint under seismic loading shows large looseness and slippage with low stiffness. Also, the energy dissipation capacity is insufficient and the failure of tabs in the joints might lead to brittle behavior. In this study, new detail of the speed-lock joint with bolts is proposed by adding a pair of split bolts in the beam end plate while still preserving its merit of ease of installation. A double-cantilever beam test was designed to test this speed-lock joint with split bolts along with the typical speed-lock joint. Low cyclic loading tests were performed on both types of joints: with split bolts and without split bolts. The results revealed the benefits that the split bolts could bring to significantly enhance the performance of the joint in terms of the maximum bending moment, the initial stiffness, the displacement ductility coefficient, the equivalent viscous damping coefficient, and the energy consumption. In addition, a two-step analysis method was proposed for the high-fidelity finite element model of the joints to overcome the complex contact nonlinearity. The numerical model was then validated with the tests for further numerical studies on the performance of speed lock joints with/without bolts. • Experimental tests were designed and conducted on the typical speed-lock joint and proposed joint with added split bolts. • With split bolts, the joint has less slippage and looseness and effectively eliminates the brittle tab failure. • Speed-lock joints with split bolts possess an additional load bearing mechanism that improves the seismic performance. • Atwo-step analysis method was proposed for the finite element model of the joints to overcome the complex contact nonlinearity. • Stress distributions from experimental and numerical results reveal the joint's improved bearing mechanism. [ABSTRACT FROM AUTHOR]

Bending is one of the most common forms of deformation that may cause failure of a structural member, such as a column, especially when the member is exposed to fire. Fire resistance design is therefore an important factor that must be considered in the design process of modern building structures. Based on the authors' previous work on the unified formulation of axially loaded CFST hollow and solid columns with circular and polygonal sections, a unified formula for calculating the ultimate bending moment of solid and hollow CFST columns at room temperature is proposed first in this paper. The formula is then extended to include elevated temperature using the average temperature method. Finally, a unified formula for both room and elevated temperature are presented. Validations are carried out through comparisons with the results from experimental tests and finite element simulations. [ABSTRACT FROM AUTHOR]

The article presents the seismic evaluation and retrofit of a 10-storey steel building located in Vancouver, British Columbia, designed following the provisions of the 1980 NBCC and the CSA-S16.1-M78 steel design standard. Lateral resistance is achieved by tension-only X-bracing with back-to-back double angle members. Seismic evaluation is first performed in accordance with the recommendations of the User's Guide to NBCC 2010 using response spectrum analysis. A Tier 3 systematic evaluation according to ASCE 41-13 is then carried out using both linear and nonlinear dynamic analysis procedures. The performance objectives are set same as those implied in NBCC 2010. The ASCE 41 approach results in much less corrections to the structure. Using the mean results from 10 ground motions is also less stringent than using the maximum of three records. For this structure, nonlinear dynamic analysis permitted to identify the concentration of inelastic deformations demands on the braces along the frame height. This behaviour induced considerable bending moment demands on the columns not captured by linear dynamic analysis. Finite element analysis of the structure columns showed that columns of braced steel frames can exhibit higher ductility compared to acceptance criteria specified in ASCE 41. [ABSTRACT FROM AUTHOR]

The moment gradient factor is an important parameter to be considered in the design of beams subjected to failure by Lateral-torsional Buckling. The analytical formulation to obtain the critical moment for the LTB is based on the assumption of applying a constant bending moment along the free span of the structural element. This loading situation is not usual in engineering projects, so it is necessary to correct the value of the critical moment according to the different loading situations that can be found in practical cases. Thus, many design codes worldwide assign values to perform this correction. The moment gradient factor, Cb, is determined by comparing the elastic critical moment of a beam subject to varying moment condition with that subject to a constant moment condition. When considering beams with web openings, there are currently no recommendations or proposals for calculating the moment gradient factor, considering loads applied outside the shear center. There are also no explicit recommendations in standards regarding the design of this type of structure. Recent research deals with the influence of cellular beam parameters on the moment gradient factor; however, they do not present explicit proposals for its calculation in structures of this nature. The research scenario in the literature becomes even more scarce when considering beams with sinusoidal web openings. Thus, the paper investigates this for a wide range of I-beams with openings, with the goal of analyzing the influence of the openings on the C b , as well as proposing formulae for usual design situations. The proposals were obtained through prediction models derived from an extensive parametric study using the ABAQUS finite element software, in which 34,020 models were developed. • A massive parametric study based on 34,020 finite element models is presented. • The influence of the geometric parameters of beams with sinusoidal web openings in the moment gradient factor was explored. • A new proposal for determining the moment gradient factor in steel I-beams with sinusoidal openings was developed. • The methodology presented is considerably more efficient than the proposals of design codes. [ABSTRACT FROM AUTHOR]

A new type of inner and outer double-ringed (IODR) flange was introduced in this paper, which can make full use of the inside and outside space of circular tube and reduce the dimensions of connecting bolt and flange plate. Five groups of down-scaled IODR flanges with different flange plate dimensions were designed and tested under bending moment to study the failure mode and force-transferring mechanism. The finite element model was built to further investigate the influence of connection dimensions on the bending performance from different aspects, such as bearing capacity, location of rotation axis and bolt tension ratio. It reveals that the failure of IODR flanges occurred due to the necking of bolt. The bolt tension ratio has an insignificant change when the applied load is smaller than about 80% of bending capacity, then it tends to increase until approaching 1.0. A theoretical method for rotation axis position and bolt force was proposed considering flange geometry parameters and bolt arrangement. It was found that the obtained rotation axis positions are about 0.7 r , which is smaller than 0.8 r recommended in DL/T 5629–2021, meaning that the existing design method is unsafe. Based on the theoretical analyses, the design methods of flange plate, stiffener and bolt were proposed and a corresponding design process was also established. • A new kind of inner and outer double-ringed (IODR) flange was introduced. • Bending experiments of IODR flange were performed. • The FE model was built to investigate the bending performance of IODR flange. • A theoretical method for rotation axis position and bolt force was proposed. [ABSTRACT FROM AUTHOR]

In order to explore the ultimate biaxial bending performance of H-section steel members under different loading conditions, we conduct a comprehensive parametric study on H-section members with different axial force ratios, web and flange width-to-thickness ratios, and loading angles. Material and geometric nonlinearity are considered, and previous laboratory test results validate the finite element models. A criterion for determining the ultimate state of biaxial bending members is proposed based on the elastic–plastic stability theory. The ultimate biaxial capacity of the members subjected to monotonic biaxial bending and axial force is analyzed, and biaxial moment ultimate interaction curves are obtained by least square fitting. Furthermore, the influences of four different hysteretic protocols on the hysteretic behavior of the members are investigated, and the applicability of the monotonic biaxial moment limit interaction curve to the cyclic loading model is verified. A design equation for predicting the ultimate capacity of the members is proposed, considering the hardening effect of the material and the interaction effect of the plate. The proposed approach can predict the ultimate capacity of H-section biaxial bending members. The method is not limited by section classification and loading protocol and has universal applicability. • A criterion for determining the ultimate state of H-shaped steel members subjected to biaxial bending. • The ultimate state development process of H-shaped steel members under monotonic loading. • Four complex cyclic loading systems, including the BL, REC, ROM, CRU, were selected to conduct the ultimate state analysis. • The similarities and differences of ultimate state between monotonic loading and cyclic loading. • Biaxial ultimate interaction curves accurately predict ultimate bidirectional bending moment of members. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive experimental and numerical investigation into the local buckling behaviour of laser-welded stainless steel slender I-sections under combined compression and bending moment. A testing programme was firstly carried out, including initial local geometric imperfection measurements and eccentric compression tests on ten laser-welded stainless steel slender I-section stub column specimens. Following the testing programme, a numerical modelling programme was conducted. Finite element models were developed and validated against the test results, and then adopted to perform parametric studies to generate additional numerical data. The obtained test and numerical data were used to evaluate the applicability of the interaction curves in the European and American codes and the continuous strength method to laser-welded stainless steel slender I-sections under combined loading. The evaluation results generally show that the three sets of considered interaction curves offer adequate design accuracy for laser-welded stainless steel slender I-sections under combined compression and major-axis bending moment, but they yield unduly conservative and scattered resistance predictions for laser-welded stainless steel slender I-sections under minor-axis combined loading, owing principally to the conservative minor-axis bending end points. Finally, an improved design interaction curve for the minor-axis combined loading case was developed and shown to yield substantially more accurate and consistent resistance predictions for laser-welded stainless steel slender I-sections under minor-axis combined loading than the three considered design methods. The reliability of the new design interaction curve was confirmed based on a reliability study. • Local stability of laser-welded stainless steel slender I-sections under combined loading was studied. • Eccentric compression tests on ten laser-welded stainless steel slender I-sections were conducted. • FE models were developed and validated against the test results, and then used to perform parametric studies. • The European, American and CSM interaction curves were evaluated, based on the test and FE results. • New interaction curve was proposed and shown to offer improved design accuracy and consistency. [ABSTRACT FROM AUTHOR]

In this study, a novel three-dimensional semi-rigid steel joint with a channel steel component is proposed, in which the channel steel component is connected to the column flange through a hybrid connection of bolts and welds along the minor axis. The design of the minor axis connection in this study had no weakening effect on the column web, and it was more convenient and easier to attach the additional channel steel component than the additional plates to the column flanges by welding. In order to investigate the static behaviour and seismic performance of the proposed novel three-dimensional semi-rigid steel joint with a channel steel component and to evaluate the interaction between both axes, numerical analyses were conducted systematically. The finite element (FE) models are firstly calibrated against the experimental results in order to get accurate results, and then the rotating characteristics, joint moment capacity, joint stiffness, ductility and energy dissipation capacity of the proposed novel semi-rigid steel joints were analysed under ten loading cases along the major and minor axes. The results indicate that the proposed novel semi-rigid steel joint has good energy dissipation capacity and deformation performance. Loading in the major-axis direction has almost no influence on the ultimate joint moment capacity but has some influence on the initial stiffness, ductility, stiffness degradation and energy dissipation ability of the proposed novel semi-rigid steel joint along the minor axis. In addition, the modified moment-rotation (M - θ) hysteretic model for the proposed novel semi-rigid steel joint is capable of effectively characterising its hysteretic behaviours, which can provide a reference for practical applications. • A novel 3D semi-rigid steel joint with channel steel component is proposed. • It is simpler and easier to attach channel steel component in minor-axis direction. • The novel joint has a good energy dissipation capacity and deformation performance. • Loading in major axis has some influence on the mechanical behaviours in minor axis. • The modified M - θ hysteretic model for the proposed novel joint is proposed. [ABSTRACT FROM AUTHOR]

Steel transmission poles are widely used for their strength, ease of construction, small footprint, and aesthetic appearance. These poles can be either directly embedded into their foundations or supported on based plates which are connected to the reinforced concrete footings via group of anchor bolts. There are few available published methods for the analysis and design of this type of base plate connection. These methods are not widely used in the industry as they are either complex, lack solid theoretical background, or yield results that are not consistent with manufacturer's time-tested proprietary design methods. Therefore, there is a need for an accurate method suitable for technical or design office for designing these connections when subjected to axial loads, bending moments or the combined effect of both. This paper presents a numerical study performed on the base plates of polygonal steel poles that are supported directly on anchor bolts with levelling nuts and subjected to bending moment and axial load. The Finite Element (FE) analysis part of the work is carried out using ADINA software and the results obtained from the analyses are compared with published experimental results from which it is concluded that the finite element model can accurately predict the behaviour of these connections. Parametric investigation is then conducted to gain more insight into the behaviour of these base plate connections and to use the obtained data the validation of the proposed design method. The parametric investigation covered the behaviour of these connections under pure axial load and pure bending moment while the varying parameters considered included number of shaft sides, base plate thickness, number of anchor bolts and anchor bolt diameter. Design formulae based on the yield line theory are then proposed and a comparison between the yield loads calculated using the proposed expressions and finite element results is presented. The yield loads resulting from using the proposed design method agreed with the finite element results with a maximum calculated difference of 13%. [ABSTRACT FROM AUTHOR]

This paper studied the progressive collapse resistance of 10 beam-column joints with post-high-temperature through static tests. The size of the ten specimens is the same, and the connection form is bolt-welded connection. Among them, one specimen was at room temperature, and the other nine specimens were treated at 400 °C, 600 °C, and 800 °C and held at the temperature for 30, 60, and 90 min, respectively. The load-displacement curve, deflection curves, and strain development of the critical section of the specimen were studied, and the axial force, bending moment, bending resistance, and catenary mechanism of the specimen were calculated according to the test results. Before and after high temperatures, the failure of specimens is beam-end damage. Temperature only affects the initial position of failure of beam-column joints. The duration time has no noticeable effect on the properties of the steel. Based on the test results, it is found that at the same duration time and different high temperatures, the higher the temperature, the smaller the maximum vertical load and joint rotation angle at failure, and their axial force and bending moment are also weaker. However, there is no difference between the plastic limit rotation angles of the specimens. At the same temperature and different duration, the load-displacement curves of the specimens are very similar. It can be seen that at the same temperature, the duration time has little effect on the mechanical properties of the specimen. At the same time, although the mechanical properties of the specimens were weakened after high temperatures, they still maintained an excellent ability to resist progressive collapse. Even the beam angle of the member with the smallest failure angle was 0.15 rad, more significant than 0.06 rad. The finite element model established by ABAQUS is mutually verified with the test results to prove the accuracy and effectiveness of the finite element model. Based on this model, the expanded parametric analysis is carried out to analyze the influence of hole spacing and hole diameter on the progressive collapse resistance of the specimen after high temperature. • Progressive collapse performance of joint after high temperature was studied. • Study parameters included high temperature and duration. • Simulated results obtained by finite element method correlated well with the experimental results. • The joints after high temperature still exhibit superior anti-collapse performance. [ABSTRACT FROM AUTHOR]

This study proposes a novel buckling-restrained brace (BRB) using multiple round steel core bars to increase the feasible strength of BRBs utilizing steel bars with roll-threaded screw ends. The buckling restraining members of the proposed BRB consists of multiple primary tubes and a secondary tube. The primary tube directly restrains the buckling of each core bar, and the secondary tube restrains the buckling of the primary tube through spacers. This paper first describes the configuration of the proposed BRB and the design method of buckling restrainers, in which the spacer spacing is assumed to be the buckling length of the primary tube. Subsequently, cyclic loading tests of three specimens with different spacer spacing are presented to demonstrate the mechanical behavior of the proposed BRB, such as the hysteresis behavior, axial force, and bending moment of the primary tubes. The test results indicated that fulfilling the requirement of spacer spacing is essential for achieving stable behavior of the primary tubes and steel core bars. Finally, finite element analyses of buckling-restrained units of the proposed BRB with different combinations of primary tubes and spacer spacing are presented to verify the design method. The results of the parametric analyses indicated that the proposed design formula can provide a conservative evaluation of the stability of the primary tube. • A buckling-restrained brace using multiple round steel core bars was proposed. • The buckling restrainer consists of primary and secondary tubes. • Cyclic loading tests validated the performance of the proposed BRB. • FEA of buckling-restrained units verified the design of primary tubes. [ABSTRACT FROM AUTHOR]

This paper focuses on the investigation into global stability design of grid cylindrical-lattice shell (GCLS) under combined axial compression and moments. This study is an extension of previous researches carried out by the authours in the elastic buckling and axially load-bearing capacity of GCLSs (Zhu et al., 2021, 2022). Accordingly the elastic buckling load and global compression stability coefficient of GCLS loaded axially are employed. The finite element model adopted in this study has been validated by previous researches (Zhu et al., 2021, 2022; Guo et al., 2017). First the elastic buckling behaviours of GCLS under pure bending moments is explored by using eigenvalue buckling analysis. The obtained results demonstrate the effects of the bending moment direction, the beam-column stiffness ratio, the diameter-height ratio of GCLS, the number of columns, and the number of storeys of GCLS on the elastic buckling load of GCLS. Subsequently, the ultimate stability capacity of GCLS under pure bending moment are investigated numerically by using a large number of numerical examples in the common range of engineering applications. Accordingly, a design formula is established based on a relationship between the bending stability coefficient φ M and the compression normalized slenderness ratio λ N , namely the φ M - λ N curve for predicting pure bending-bearing stability capacity. Finally, the interaction design formula for predicting the stability capacity of GCLS under combined axial compression and moment is proposed conservatively by introducing axial compression stability coefficient and bending moment stability coefficient. This interaction design formula is further validated by employing a large number of the numerical examples and provides fundamentals for designing GCLSs in practice. [Display omitted] • Elastic buckling behavior of Grid Cylindrical-Lattice Shells (GCLSs) under combined axial compression and bending moment is investigated. • Stability curve φ M - λ N of GCLSs under bending moment is obtained by using numerical examples. • Stability capacity design of GCLS under combined axial compression and bending moment is proposed according to an interactive formula of N/N u ∼ M/M u. [ABSTRACT FROM AUTHOR]

Analytical formulations for the evaluation of the critical bending moment for lateral-torsional buckling of a beam taking into account warping restraints at supports are proposed in this paper. A theoretically exact solution is firstly derived from differential equilibrium equations using infinite power series for the twist rotation. Next, the deflected shape is approximated using a single or several base functions for the displacement and rotation fields. The energy method is then used to derive approximate expressions of the critical bending moment of beams subjected to various loading conditions: constant/linear bending moment distributions, mid-span pointwise transverse force or uniformly distributed load. The warping coefficient k w does not depend on the bending moment diagram. The equivalent uniform moment factor C 1 can be conveniently expressed as a product of two coefficients, one related to the bending moment distribution and the other to the warping restraints stiffness. Finite Element analyses of beams with warping restraints at supports have been performed considering a shell elements model created in ANSYS and a beam elements model developed in LTBeamN. • Theoretical exact solution for lateral-torsional buckling with warping restraints • Approximate analytical expressions of M cr in Eurocode 3 format • A single expression of the warping factor k w. • Warping stiffness limit characterizing semi-rigid joints [ABSTRACT FROM AUTHOR]

In current design provisions, the plastic moment and rotation capacity of plastic hinges for beams must not be decrease due to compressive and/or shear forces. For the majority of moment-resisting frames, the influence of shear and axial forces on the bending moment and rotational capacity of plastic hinges can be ignored, because the shear and axial forces typically observed are low relative to the shear and axial capacities. However, in some cases, the lateral force-resisting systems are composed of closely spaced columns rigidly connected by short steel beams. Each of these beams is long enough to allow the development of plastic moment hinges at the ends, but also short enough to develop significant shear forces that can influence the bending moment and rotational capacity of the beam. This report presents a parametric study conducted using an experimentally calibrated numerical model, performed at the CEMSIG Research Centre ( http://www.ct.upt.ro/en/centre/cemsig ) at the Politehnica University of Timisoara. The study observes and characterizes the plastic mechanism of short steel beams with reduced beam sections (RBS) applied in moment-resisting frames. A simplified and reliable alternative allowing the use of beam finite element analysis (FEA) for bending–shear interactions is proposed. [ABSTRACT FROM AUTHOR]

Single-web angle connections bolted to the beam web and the column flange are studied to investigate the effect of the thickness, length, and material properties of the angles, number of bolts, and gage distances of the fasteners on their moment–rotation behavior. ABAQUS software is used to analyze the nonlinear behavior of a single-web angle connection. Identical geometric and material properties with Lipson's test are utilized to verify the finite element models. A simpler and more accurate equation for the initial stiffness is suggested, and good agreement between the proposed model and Lipson's test data is demonstrated. The type of collapse mechanisms for single-web connection is established. The ultimate moment capacity modified from Kishi and Chen's equation is also proposed, and it agrees well with Lipson's test data. [ABSTRACT FROM AUTHOR]

The ConXL connection is a standardized and cost-efficient biaxial moment frame connection. It could provide higher construction efficiency if the filled concrete in a steel box column could be eliminated. To determine the seismic behaviours of this connection economically, this study developed a complex nonlinear finite element model (FEM) using the ABAQUS software. After verifying the FEM, four different representative FEMs of joint configurations without concrete filling in the column, including a 2D interior, a 3D interior, a 3D exterior, and a 3D corner joint, were established and loaded with unidirectional and bidirectional cyclic loads. The hysteresis behaviour under different axial load levels in the column was analysed. In addition, to compare the seismic performance of different joint forms more intuitively, the vertical load–displacement relationships at beam ends were equivalently expressed as the storey shear force versus the storey drift of one column according to the energy equivalence principle. The results show that various ConXL connection joint configurations without concrete filling in the column show beam hinge mechanism failure mode when the axial load level in the column is not too high (~ 0.4). However, the failure mode becomes beam–column hinge hybrid failure mechanism or even column hinge mechanism with an increase in the axial load level. The seismic behaviours are acceptable according to AISC 341, and the panel zone does not show yielding, making it suitable for application as a beam–column connection in steel moment frame structures. [ABSTRACT FROM AUTHOR]

Open cross sections are used in structural applications to resist bending moments. The buckling length specified in the current standards and specifications was firstly defined by Nethercot [13] and covered only doubly symmetric I-sections. In this research, a theoretical program was performed to study the elastic and inelastic behavior of overhanging C-section beams bent about the major axis. A finite element model, correlated well with experimental results, was used in this study to perform a parametric study. Nonlinear geometrical and material analyses were incorporated in the model. Four types of lateral supports at the tip of the overhanging beams were studied. The effect of different boundary conditions at the root (intermediate support) of the overhanging beams was studied. Only concentrated load at the tip was considered. Three different loading positions, with respect to cross-section height, were studied. Based on the parametric study, proposed design model, taking into consideration the effect of different parameters on the ultimate moment capacity of such beams, was presented. Modified effective buckling lengths of such beams were compared to those suggested by SSRC Guide [8], which were incorporated in most current standards and specifications. This comparison showed that the ultimate moment capacities of such beams computed according to AISC Specification [1], BS5950 [3], Eurocode3 [7] and ECP [5] varied from overconservative up to 85% to unconservative up to 15%, depending on the overhanging length, back span length, boundary conditions and the load location along the beam depth. [ABSTRACT FROM AUTHOR]

In this paper, a suitable technique, based on experimental results, for including the interaction between the compressive axial force and bending moment in the space structure jointing system is proposed. In this technique, the hardening behaviour of the connection is simulated by a mathematical model and the softening behaviour is estimated from the limit surface of the axial force and bending moment diagrams. The interaction between the axial force and bending moment was taken into account in the finite element code. Also, effects of compressive axial force–bending moment interaction on the load–displacement behaviour of a toggle frame are studied. It was found that, although the compressive force increases the connection stiffness initially, it has no significant effect on the behaviour of the toggle. Also, significant change occurs after the limit point. This indicates that the released kinetic energy after post-buckling behaviour increases, that is, the axial force causes the release of more kinetic energy after post-buckling and consequently sudden failure of the structure. [ABSTRACT FROM AUTHOR]

This study explored the impact of irregular dynamic loads on castellated steel beams (CSBs) by conducting drop weight impact tests and establishing a numerical model using the nonlinear finite element method. The numerical simulation results were compared with the test results of the impact to verify its validity and analyze the buckling process and stress development of the CSB under impact load. Results showed that during the impact process, the maximum shear force was achieved first, followed by maximum bending moment and maximum deflection, respectively. It was observed that the increase in impact velocity and impact mass were unfavorable to the deflection of the CSBs, and resulted in an increase in the time required to dissipate impact energy. Furthermore, the ratio of spacing between openings to beam height exhibited a minor impact on the deflection in the range of 1.083–1.75. The ratio of opening height to beam height mainly affected the deflection near the midspan of the CSBs in the range of 0.5–0.7. The impact location significantly influenced the shape of the deflection curve. The larger the span-height ratio was, the more unfavorable it was for the CSBs to resist the impact. In addition, while the clamped support boundary condition reduced CSB deflection, it resulted in a rather substantial bending moment at the CSB ends. Based on the support rotation value as the damage evaluation index, a damage assessment curve with impact velocity and impact mass as the main control parameters was established. • The impact of irregular dynamic loads on castellated steel beams (CSBs) was explored by FE method. • The proposed numerical model could simulate the dynamic response of CSBs under the impact load. • A parameter analysis was determined the influential factors of the CSBs under impact load. [ABSTRACT FROM AUTHOR]

The performance of concrete-encased CFST column under combined compression and bending is studied in this paper. A finite element analysis (FEA) model is developed to analyse the behaviour of the composite column, and generally good agreement is achieved between the measured and predicted results in terms of the failure mode, the load-deformation relation and the ultimate load. Typical failure modes, full-range response of load-lateral deflection relation, loading distributions of the inner CFST and the outer RC components, the contact stress between the steel tube and the concrete of the composite columns are analysed. The influence of slenderness ratio and loading paths on the composite columns are also investigated. Influence of parameters, such as the strength of concrete and steel, steel ratio of CFST, longitudinal bar ratio and diameter of CFST on the sectional capacity of the concrete-encased CSFT columns is analysed based on the FEA model. A simplified model is proposed to calculate the sectional capacity of concrete-encased CFST columns under combined compression and bending. [ABSTRACT FROM AUTHOR]

Hollow structural sections (HSS) provide an alternative to typical wide flange sections in low-rise seismic moment resisting frames. Their beneficial strength-to-weight ratio as well as bending, compression, and torsional resistance increases the versatility of moment frames and potentially improves performance under earthquake loads. With an understanding of current design requirements for seismic moment connections and static HSS-to-HSS connections, 39 fully welded unreinforced HSS-to-HSS connections are explored through finite element analyses. However, performance is limited due to column face plastification and inability to develop the plastic moment capacity of the beam. To rectify this problem, 24 through plate and 24 external diaphragm plate HSS-to-HSS moment connections are analyzed. Several important geometric parameters, such as the beam width-column width ratio, beam thickness-column thickness ratio, plate length, and plate thickness are considered to understand their effect on the connection moment capacity and sources of inelastic rotation. The through plate and external diaphragm reinforcement greatly improve the connection behavior moving yielding away from the column face and into the beam member. The results from the reinforced connections are used in combination with current seismic design provisions to develop a design procedure that optimizes the performance of these connections. The reinforced connections can be detailed to develop plastic hinging in the HSS beam member while minimizing the likelihood of a non-ductile weld failure. [ABSTRACT FROM AUTHOR]

Traditional shear panel dampers (SPDs) can be vertically installed in eccentrically braced composite frames (EBCFs) to effectively increase the stiffness and strength of such frames. Moreover, SPDs can dissipate the input energy in such frames through their plastic deformation in seismic conditions. However, vertically installed dampers may impose an additional bending moment on the middle segment of the primary beam in the composite frame, resulting in significant damage to the concrete slab. To overcome this limitation, a novel type of SPDs with bent web panels (BSPDs) is developed, in which the end plate of the BSPD is connected to the web of the composite beam. In this configuration, the bending moment resulting from the SPDs can be minimized, thereby reducing the damage to the concrete slab. In this study, the characteristics of BSPDs and their configuration in EBCFs were examined. Subsequently, the key design parameters of the EBCFs with BSPDs, which could help alleviate the damage to the concrete slab, were identified. Moreover, different BSPDs were experimentally and numerically investigated to verify their seismic performance. The results indicated that BSPDs exhibit ductile behaviour after yielding and excellent energy dissipation capacities. Low-yield-point steel and link flanges can be used to increase the deformation capacity and energy dissipation efficiency of such dampers. Results of the experimental and numerical investigations were considered to specify design recommendations for the application of BSPDs. A novel type of SPDs with bent web panels (BSPDs) is developed, in which the end plate of the BSPD is connected to the web of the composite beam. In this configuration, the bending moment resulting from the SPDs can be minimized, thereby reducing the damage to the concrete slab. In this study, the characteristics of BSPDs and their configuration in EBCFs were examined. Subsequently, the key design parameters of the EBCFs with BSPDs, which could help alleviate the damage to the concrete slab, were identified. Moreover, different BSPDs were experimentally investigated to verify their seismic performance. The results indicated that BSPDs exhibit ductile behaviour after yielding and excellent energy dissipation capacities. Low-yield-point steel and link flanges can be used to increase the deformation capacity and energy dissipation efficiency of such dampers. Results of the experimental and numerical investigations were considered to specify design recommendations for the application of BSPDs. [Display omitted] • A novel type of Shear Panel Dampers with bent web (BSPDs) for Eccentrically Braced Composite Frames (EBCFs) are proposed to alleviate the damage of the concrete slab. • Structural mechanics analysis is conducted to determine factors to the BSPDs. • The seismic performance of the BSPDs are verified with experiments. • Key parameters on the BSPDs performance are analyzed based on the experiment results. • Finite element models are established to simulate the complex mechanical properties of the BSPDs. • Design recommendations for the application of the BSPDs are provided. [ABSTRACT FROM AUTHOR]

This paper presents the stability behaviours and capacity design of the grid cylindrical-lattice shell (GCLS) which consists mainly of the multi-columns located circumferentially and the multi-story ring-beams uniformly distributed along the height. The GCLS under axial compression is investigated in the stability capacity by using a finite element model that has been validated by an experimental investigation carried previously out by the authors. A large number of numerical examples of GCLSs covering a common design range of engineering applications are analyzed numerically by employing the validated finite element (FE) model to investigate the ultimate load-carrying capacity, and accordingly a stability capacity design method regarding the compression stability coefficient φ N and the normalized slenderness ratio λ N is established. Based on a design criterion that the failure of the ring beams does not precede the multi-column instability, the strength design formula of the ring beam is proposed accordingly and validated by using FE numerical results. In summary, this paper supplies a complete design method for predicting the stability capacity of the GCLSs as well as strength check of the ring beams in the GCLSs under axial compression. This study lays a preliminary research foundation for subsequent research on the stability capacity design of GCLSs under a combined action of axial compression and bending moment. [Display omitted] • Load-carrying capacity of GCLSs under axial compression are investigated theoretically and numerically. • Stability curve φ N - λ N obtained by using numerical examples can be directly used in the design of the GCLSs. • The strength design formula of the ring beam is established based on the theoretical and numerical investigation. [ABSTRACT FROM AUTHOR]

This paper presents experimental results of twelve eccentrically loaded short composite columns made by filling circular steel tubes with ultra-high performance concrete (UHPC) cured under room temperature. Using these test data as benchmarks, finite element models are developed and used to perform parametric studies to determine how the capacities of these columns are affected by load eccentricity and tube diameter-to-thickness ratio. In addition, a relationship between the balanced eccentricity ratio and the confinement coefficient is established. The results of the present study have shown that: (1) failure of these columns is characterized by yielding of the steel tubes, followed immediately by failure of the core concrete; (2) a decrease in diameter-to-thickness ratio increases the peak load and improves the column's post-peak behavior; (3) an increase in the load eccentricity ratio results in a reduction of the load capacity, ductility and stiffness of the column; (4) the compressive strain in the steel tube develops more rapidly due to second-order effect, and the assumption that plane sections remain plane no longer applies when the applied load reaches 80% of the peak load. By comparing the axial force – Bending moment (N u - M u) interaction diagrams generated in the present study with existing codes, it is found that the code equations are mostly conservative. A set of trilinear N u - M u interaction equations that can produce more accurate results is therefore proposed • Twelve short composite columns subjected to eccentric loads were tested. • Ultra-high performance concrete cured under room temperature was used. • Finite element models were developed to conduct parametric studies. • Axial load-bending moment interaction diagrams were generated. • A new set of triaxial interaction equations was proposed. [ABSTRACT FROM AUTHOR]

During the last decade, simple solutions of thermal breaks have been developed for steel structures that consist in inserting an intermediate insulating layer (composed of PVC, plywood, elastomer, FRP...) between a bolted end-plate and a steel/concrete support. Experimental tests highlighted that failure modes under bending moment are similar to that of conventional bolted connections particularly in the tensile area, whereas the ultimate resistance decreases. For standard bolted connections loaded by a bending moment, the T-stub concept is used to model the tensile area. This model, extensively used in Eurocode 3, assumes that the end-plate is in contact with a rigid foundation or concrete/grout. T-stub can potentially be used to model the tensile area of bolted connections in presence of intermediate insulating layer. However the current model cannot be directly applied as the end-plate rests on a flexible support. In the present paper, a mechanical model is proposed to firstly model the elastic behaviour of T-stubs in contact with a flexible intermediate layer. The model relies on the Timoshenko beam theory in contact with a Winkler foundation modelling respectively the end-plate and the intermediate layer. The contact pressure distribution being almost linear, simplifications are proposed in this sense. It is demonstrated that simplifications can be considered for standard material used as intermediate layer such as PVC or FRP. An analytical model is also given to calculate the ultimate resistance of T-stubs considering yielding of the intermediate layer. These results are validated by comparison to finite element analysis results performed with ANSYS code using solid and contact elements. This FE analysis highlights a clear distinction between the elastic and elasto-plastic behaviors of these T-stubs particularly concerning prying effects. • Elastic and ultimate models for T-stub in contact with an intermediate layer • Linear contact pressure distribution for the elastic range of behaviour • Significant modification of prying effect for flexible layer after yielding [ABSTRACT FROM AUTHOR]

Abstract: This work deals with the evaluation of the ultimate bending moment of a severely corroded box girder subjected to uniform vertical bending moment through a series of nonlinear finite element analysis. Two models of corrosion degradation have been adopted, one is an average general corrosion thickness reduction, and the other is the real thickness of the corroded plates. New stress–strain relations have been developed to account for the effect of corrosion on the flexural rigidity. To validate the new developed stress–strain relationships, a comparison between the finite element analysis results using the existing stress–strain models, the newly developed ones and the experimental test results of a severely corroded box girder have been conducted. The comparison showed a good agreement and supported the choice of the newly developed stress–strain relationships of corroded structures. [Copyright &y& Elsevier]