Search

Shear walls are widely used as lateral load-resisting systems in high-rise building structures. The design and nonlinear analysis of shear walls under seismic loads for recoverability are complicated and challenging, which demands nonlinear computer modeling procedures. This paper presents a novel finite element named Double Vertical Beam-column with Shell Element (DVBSE) for the nonlinear analysis of complex reinforced concrete shear walls with columns. The DVBSE is implemented in the open-source finite element program OpenSees. The theoretical formulations of DVBSE are described in detail. The accuracy of the developed DVBSE is established by comparing the finite element analysis results with existing experimental data on recoverable steel-GFRP composite bar reinforced concrete shear walls. The comparative study demonstrates that the proposed DVBSE is superior to the commonly used finite element model in simulating the responses of recoverable complex shear walls under seismic loads. These research findings contribute to further advancements in the development of new shear wall elements and lay a solid foundation for the nonlinear numerical simulation of innovative shear walls. • A new finite element DVBSE is developed for modeling shear walls under seismic loads. • The DVBSE incorporates vertical fiber-based beam-column elements and shell elements. • The DVBSE is implemented in the open-source finite element program OpenSees. • The accuracy of the DVBSE is verified by test results of recoverable complex shear walls. • The DVBSE offers an efficient approach to simulate the seismic behavior of shear walls. [ABSTRACT FROM AUTHOR]

This paper presents the application of a thick-shell nonlinear finite element analysis procedure to estimate the punching shear resisting performance of reinforced concrete slab-column connections under variable connection shear stress conditions. In the analyses performed, varied connection shear stress conditions stem from slabs being supported by columns with different cross-section aspect ratios, being subjected to different distributions of gravity loading, being constructed with different planar reinforcement ratios in orthogonal directions, as well as the application of unbalanced bending moments. Forty-eight isolated slab-column connection specimens presented in the literature were modelled and analyzed using a thick-shell finite analysis procedure. All numerical results were developed using a predefined set of material models and analysis parameters, a consistent meshing procedure, and are shown to provide meaningful agreement with experimental data without the need for case-specific model calibration or the adoption of specialised failure criteria. The results show that thick-shell modelling methods can be suitable for estimating the punching shear response of slabs subjected to non-uniform shear stress development in connection regions, and can provide similar levels of precision to that obtained for the analysis of idealised slab-column connections typically used for design procedure and model development. • Low-cost shell FEA for punching shear assessment of reinforced concrete flat plates. • Analysis of 45 non-idealised connection specimens representative of real-world construction. • Good agreement between FEA simulations and reported results without model calibration. • Result accuracy comparable to that obtained for more typical idealised connection specimens. [ABSTRACT FROM AUTHOR]

This paper presents a finite element (FE)-based reliability analysis of reinforced concrete masonry walls under eccentric axial loading, considering the slenderness effect. The main purpose is to (1) examine the importance of model error and (2) investigate the effect of different failure criteria on the reliability assessment of masonry walls. To achieve this goal, three representative walls with different slenderness ratios, designed in accordance with CSA S304–14 provisions, are selected for the reliability analysis. Finite element models of masonry walls are used to formulate the limit-state function for the reliability problems considered. A subset simulation algorithm in conjunction with Polynomial- Chaos-Kriging (PCK) surrogate models is used to address the computational cost involved in FE-based reliability analysis. It is found that the reliability assessment results are highly dependent on the model error. In addition, it is found that the local failure criteria are not always more conservative compared to global (wall) failure criteria due to stability failure, particularly for slender walls or walls designed with vertical loads at low eccentricities. Furthermore, it is found that other factors are found to influence the reliability assessment, including the slenderness ratio, load ratio, and eccentricity-to-thickness ratio, leading to reliability-inconsistent designs according to the current codes. • A macro finite element model is developed for the simulation of reinforced concrete masonry walls under eccentric axial loading considering slenderness effects. • Model error associated with the finite element model is quantified by compiling an experimental database. • Incorporation of model error is crucial for reliability analysis. • The influence of load eccentricity-to-thickness ratio, slenderness ratio, and load ratio on the reliability assessment is investigated. • The effects of different failure criteria (i.e., limit states) on the reliability assessment are studied. [ABSTRACT FROM AUTHOR]

This paper presents experimental and numerical investigations into the web crippling behaviour and load-carrying capacity of stainless steel built-up I-section members under End-Two-Flange (ETF) concentrated transverse loading. An experimental programme was conducted on 23 austenitic and duplex stainless steel built-up I-section specimens, with each consisting of two identical press-braked channel sections assembled back-to-back by means of self-tapping screws. Following the experimental programme, a numerical modelling programme was performed, where finite element models were firstly developed to replicate the tests and then used to conduct parametric studies. Based on the test and numerical data, the existing design rules for stainless steel built-up I-section members failing by web crippling, as set out in the current European, American and Australian/New Zealand design standards, were assessed. The comparisons indicated that the European and Australian/New Zealand design standards resulted in overly conservative and rather scattered failure load predictions, while the American design standard led to less scattered failure load predictions, but with many predictions on the unsafe side. Therefore, an improved design approach was proposed and shown to provide substantially improved failure load predictions for stainless steel built-up I-section members under End-Two-Flange loading. • The web crippling behaviour of stainless steel built-up I-sections under ETF loading was studied. • Tests were conducted on 23 stainless steel built-up I-section specimens. • FE models were developed and validated against test results and then used for parametric studies. • The existing codified design rules were assessed and a new design approach was proposed. [ABSTRACT FROM AUTHOR]

This paper presents an investigation into the free vibration and nonlinear dynamic analyses of new complex edge contour plate structures, known as single-variable-edge (SVE) plates. Cracks emerge at the center of the plate's surface, and the effects of edge crack orientation and depth on the dynamical characteristics of the laminated nanocomposite SVE plates have been considered in this study. The functionally graded graphene nanoplatelet reinforced composite (FG-GPLRC) material was utilized for the edge-cracked plate that rests on a Winker-Pasternak elastic foundation. The Halpin-Tsai micromechanical model is used to predict the material characteristics, which are presumptively temperature-dependent. The rule of mixtures is employed to determine Poisson's ratio, density mass, and thermal expansion. The governing equations are established based on the theory of elasticity, and Von Karman-Donnell geometric nonlinearity assumption. To confirm the reliability and accuracy of this approach, the acquired findings are validated with those produced using Finite Element Analysis (FEA). Furthermore, the geometrical and material parameters, fracture properties, and environmental (temperature and elastic foundation) factors are also investigated in the study. The research findings hold significant implications for applications in aerospace and aeronautical, civil, and mechanical engineering. • The crack orientation and depth have been built in laminated nanocomposite structure. • The dynamics of cracked complex plates have been scrutinized in two aspects: linear and nonlinear responses. • The periodic and chaotic status of the complex structure in critical points have been investigated. [ABSTRACT FROM AUTHOR]

This paper studies the novel vibration control of an inerter-enhanced mega sub-controlled structure system (MSCSS). The seismic response of MSCSS is investigated using a tuned viscous mass damper inerter (TVMDI) and compared with existing control methods. This novel strategy evaluates two kinds of TVMDIs on MSCSS, including the inter-story TVMDI, where the TVMDIs are installed inter-story, and the outrigger-based TVMDI, where the TVMDIs are vertically connected between the outrigger and the perimeter of the MSCSS's column to achieve significant energy dissipation. First, a finite element model of MSCSS is established and validated with the experimental model of MSCSS. The governing equation of the enhanced MSCSS is derived from the uncontrolled model. Subsequently, the MSCSS equipped with TVMDIs is thoroughly examined and compared to the existing methods. The effectiveness of the proposed strategy subject to ground motion records via the numerical analysis method is also demonstrated. Finally, the reliability analysis of the enhanced MSCSS based on the probability density function is presented. Results from the numerical investigation of the MSCSS enhanced strategies have revealed that the inter-story and outrigger TVMDI system generally improved the response effectiveness of MSCSS better than the viscous damper (VD) and middle story isolation (MSI) systems. However, the outrigger TVMDI enhanced mega frames control effectiveness more effectively than the story-based TVMDI, whereas the latter is more suitable for substructures. ● The novel vibration control of an inerter-based enhanced MSCSS is studied. ● An uncontrolled FEM of MSCS is presented and validated with the experimental model. ● The dynamic equation of MSCS equipped with TVMD is derived from uncontrolled model. ● The proposed strategies is examined and compared to the existing control methods. ● The reliability analysis of the TVMD-enhanced MSCSS based on the PDF is presented. [ABSTRACT FROM AUTHOR]

The development of a bonded glass-steel element that is capable to i) transfer out-of-plane loads due to wind loads in transverse direction, ii) in-plane shear loads, due to wind in longitudinal direction and iii) in-plane compression due to self-weight implies that the structural continuous adhesive glass-metal connection becomes an integral part of the entire bonded glass-steel unit. The frame members are restrained by the joint-glass system due to the glass bonded to the steel frame. To assess the capability of continuous adhesive glass-steel connections to transfer the abovementioned loads, research is indispensable. The available knowledge on the capacity of glass panes used as structural bracing element in steel frames is limited. This paper reports about the structural performance of welded steel corners, both not bonded and bonded with glass panes, to assess the in-plane load-bearing capacity of these connections. In a first experimental phase tests on welded steel corners with different configurations are conducted, whilst during the second phase specimens bonded with glass panes on both sides are tested. Numerical models are developed and validated based on the experimental results, which are then used for parametric studies. As such, the rotational stiffness of semi-rigid welded steel corner configurations and the additional stiffness obtained by bonded glass panes can be determined. The results demonstrated that the specimens with adhesively bonded glass panes on both sides using the structural silicones Sikasil® SG-500 and DowSil™ 993, and the hybrid polymer adhesive Soudaseal 2 K, significantly increased the initial rotational stiffness of the welded steel corners. Specimens bonded with the hybrid polymer adhesive behave significantly stiffer than specimens bonded with the structural silicones. Parametric studies on validated finite element models reveal that the effect of the glass thickness is important for low values of the adhesive thickness. The width-to-thickness ratio of the adhesive layer largely influences the value of the rotational stiffness of the connection. The generated data by the numerical models can now be implemented in analytical models for the calculation of steel structures with semi-rigid joints. • Continuous adhesive glass-metal connections using three adhesives are investigated. • The rotational in-plane stiffness is experimentally determined for (un)bonded specimens. • Analytical analyses allowed the validation of the experimental results. • Finite element models were validated and used for parametric studies. • The results can be used for the calculation of (bonded) steel structures with semi-rigid joints. [ABSTRACT FROM AUTHOR]

Headed stud shear connectors are commonly implemented in steel-concrete composite floors for connecting the concrete slab to the steel beam and providing composite action between those two elements. The orientation of profiled sheeting is usually transverse or parallel to the supporting beam, and for those cases, design codes provide specific detailing requests and relations for obtaining headed stud resistance. Nevertheless, design codes do not recognise specific configurations when the angle between profiled sheeting ribs and the beam is in the range between 0° and 90°, which is characteristic of irregular-shaped floor structures. Due to the lack of design recommendations for headed stud resistance in these cases, investigations of the effect of the rib-to-beam angle on headed stud shear performance were conducted and presented in this paper. Experimental work included push-out tests conducted on specimens with rib-to-beam angles of 45° and 60°, as well as control specimens with ribs transverse to the beam. The influence of varied rib-to-beam angles on shear connector properties such as shear resistance, stiffness, ductility, and failure mode was discussed. According to experimental research, finite element models of push-out tests were created and verified. The parametric numerical analysis covered key parameters such as concrete class, headed stud height and diameter, and rib-to-beam angle. According to the results, an analytical relation for obtaining headed stud resistance in profiled steel sheeting with a rib-to-beam angle between 30° and 90° was proposed. • Rib-to-beam angles between 0° and 90° in steel-concrete composite beams. • Experimental push-out tests on headed studs with rib-to-beam angles of 45° and 60°. • Development of finite element numerical models. • Parametric study for different rib-to-beam angles, concrete classes and stud geometry. • Analytical relation for stud resistance for varied rib-to-beam angles. [ABSTRACT FROM AUTHOR]

Despite the extensive investigations on the shear strengthening of reinforced concrete (RC) beams using externally bonded fiber-reinforced polymer (EB-FRP) composites, the critical problem of how the skew angle (angle between FRP and crack opening direction) influences the bond capacity of FRP has drawn little concern and remains unsolved. This paper presents the first three-dimensional (3D) finite element (FE) model for studying the failure of skew FRP-bonded concrete joints. The concrete was simulated using the concrete damaged plasticity model, and the FRP was modeled as an orthotropic material equipped with the LARC05 model as the damage criterion. The FRP-to-concrete interface was described using a linear elastic cohesive law. The 3D FE model, which provided a relatively large convergent mesh size of 2.5 mm, was calibrated and validated using the bond tests of aligned and skew FRPs. Both the tests and FE results revealed a notable decrease in the bond capacity of FRP at the skew angle of 45°. The parametric analysis demonstrated that the adverse skew effect was reduced when the FRP width increased or FRP thickness decreased, by delaying the onset of the stable peeling-off of concrete along the FRP fiber axis. Compared with FRP, steel plate suffered less from the skew effect, due to its isotropic nature. This study can provide valuable implications for more effective shear-strengthening methods of RC beams and facilitate novel insights for the development of more robust design models. The 3D FE framework can also serve as a versatile tool for analyzing the complicated failure modes of various FRP-strengthened concrete systems. • A three-dimensional FE model was developed for skew FRP-bonded concrete joints. • Non-zero skew angles could reduce notably the peak axial load of FRP during pullout. • The FRP bond width and FRP thickness have a significant impact on the skew effect. • Steel plates suffered less from the adverse skew effect due to its isotropic nature. • Regularized compressive stress-strain law is vital in CDPM for tension-shear failure. [ABSTRACT FROM AUTHOR]

This paper presents the experimental and numerical results of an ongoing research project on the use of thermal break systems (TBSs) in internally insulated reinforced concrete (RC) structures. A new TBS, which combines steel profiles and U-shaped steel bars, is introduced and tested under monotonic loading to determine its horizontal and vertical shear capacities. The test results confirmed the appropriateness of SLABE-TBS for use in exterior wall–slab joints that demand high ductility or energy absorption despite the failure mode by concrete punching. The tested joints exhibited load-carrying capacities of 190.2 and 120.5 kN/m under horizontal and vertical loading, respectively. On the other hand, the finite element analysis performed using LS-DYNA software confirmed the significance of the U-shaped steel bars of the SLABE-TBS in improving the joint's shear capacity. However, incorporating the steel bars in the SLABE unit can reduce the equivalent stresses in the adjacent steel profiles by 33 %. • A new thermal break system (SLABE-ZN) for exterior wall–slab joints was proposed. • The tested exterior joints equipped with SLABE-ZN exhibited stable behavior under horizontal and vertical loading. • Incorporating steel bars in the SLABE unit can reduce the equivalent stresses in adjacent steel profiles by 33 %. • The contribution of the U-steel bars was approximately 30 % and 21 % under horizontal and vertical loading, respectively. • Decreasing the insulation thickness by 10 mm accounts for a 7 % increase in the load-carrying capacity of the SLABE system. [ABSTRACT FROM AUTHOR]

This paper studied the axial compression behavior of the steel tube reinforced concrete (STRC) column, which consisted of inner CFST and outer RC components. Ten specimens, including seven STRC columns, two RC columns, and one CFST column were tested. The test parameters included the CFST area ratio (inner CFST to the whole section), longitudinal rebar ratio and stirrup space. The test results showed that the compressive behavior of STRC column with a CFST area ratio of 0.04 was close to that of the RC column, and the compressive behavior of the STRC column with a CFST area ratio of 0.13 was between that of the RC column and CFST column. The finite element (FE) models were developed and verified by test results to investigate the effects of longitudinal rebar ratio and stirrup space on the axial compression behavior of STRC column with various CFST area ratios. The load distribution between inner CFST and outer RC components was analyzed. The FE results showed that the effects of the longitudinal rebar ratio on the ultimate load of STRC column were related to the CFST area ratio. The accuracy and applicability of the five methods suggested by codes for predicting the ultimate load of STRC column were discussed based on the test and FE results. • The compression test of steel tube reinforced concrete (STRC) column with low CFST area ratio was firstly carried out. • The influences of both CFST area ratio and longitudinal rebar ratio on ultimate strength of STRC column were discussed. • The refined finite element model of STRC column for parameter analysis is established. • The five methods of codes for ultimate strength of STRC column was calculated and discussed. [ABSTRACT FROM AUTHOR]

This paper presents a study on the axial compression performance of trussed concrete-filled steel tubular (CFST) hybrid structures. A total of 26 specimens were tested, including 15 circular and 11 square cross-sectional specimens. The effects of cross-sectional types, yield strength of steel of CFST chord, web types, number of chords, and equivalent slenderness ratio were investigated to clarify the mechanical behavior of trussed structure. The analyses of the full-range response, the typical failure mode, and the distribution of the transverse deflection and strain of the structures were carried out. A finite element analysis (FEA) modelling of trussed CFST structure was established and validated against the experimental results. Through the numerical simulation, the analysis of the internal force and stress was conducted, and the hybrid effect between the web and CFST chord was revealed. Based on parameter analysis, the design calculation was proposed, and the trussed CFST hybrid structure was equivalent to a single CFST to calculate its load-bearing capacity by introducing equivalent slenderness ratio proposed. ● A total of 26 specimens were tested, including 15 circular and 11 square cross-sectional specimens. ● The influences of critical factors of trussed CFST hybrid structure were investigated. ● A FEA modelling for trussed CFST hybrid structure subjected to axial compression was established and validated. ● Design calculation for trussed CFST hybrid structure were proposed and carefully verified. [ABSTRACT FROM AUTHOR]

In this paper, a composite column using carbon fibre reinforced plastics and polyvinyl chloride composite tube (CFRP-PVC) to constrain coral aggregate seawater sea-sand concrete (CSSC) was proposed, and CFRP was pasted on the inner and outer walls of the PVC tube. To investigate the effects of the number of CFRP layers and void defects on the axial compression performance of PVC tubes, six specimens were made for axial compression loading tests and finite element parameter analysis. The results indicate that due to PVC improving the integrity of CFRP, PVC tube provide a stress transfer path for CFRP, placing CSSC in a triaxial compression state. When both the inner and outer walls of the tube are pasted with CFRP, brittle failure of CFRP-PVC tube can be effectively avoided and have relatively superior mechanical properties. In the same situation, when one layer of CFRP is pasted on the inner wall of the tube, it has better ductility and bearing capacity. When two layers of CFRP are pasted on the outer wall of the tube, the coefficient of constraint stress increase is as high as 121.5%, and the void defect only has a significant impact on ductility. A finite element model of CFRP-PVC confined CSSC columns considering Hashin damage criterion was established based on ABAQUS, accurately predicting the failure process and CFRP damage morphology of test columns under axial load. Parameter analysis shows that when the confinement coefficient of CFRP-PVC confined CSSC columns is less than 0.3 and the height-diameter ratio is greater than 15, the load-displacement curve will lose the strengthening stage, and increasing the number of outer CFRP layers will slightly increase the stiffness of the strengthening stage. A bearing capacity calculation method suitable for CFRP-PVC confined CSSC was proposed based on the model of steel tube confined concrete, with an error of 1.2%. ● CFRP-PVC tube confined coral aggregate seawater sea-sand concrete (CSSC) column was proposed. ● The axial compression test was conducted to explore the mechanical properties of CFRP-PVC confined CSSC columns. ● The finite element models of the CFRP-PVC confined CSSC column were established to conduct parametric investigation. ● The axial strength calculation method of CFRP-PVC confined CSSC columns was proposed considering the CFRP-PVC tube restraint efficiency. [ABSTRACT FROM AUTHOR]

This paper presents a stochastic methodology to perform time-dependent seismic fragility analysis for reinforced concrete (RC) columns subjected to chloride attacks. Numerical modelling methods considering the increasing variability of reinforcement mechanical properties were proposed based on the stochastic constitutive model for corroded steel bars. Depending on the finite element model validated by test data for uncorroded and corroded RC columns, two novel stochastic cases and a traditional deterministic case were introduced and then applied to pushover analysis, incremental dynamic analysis and seismic fragility analysis. The results of damage limit states (DLSs) determined by stochastic pushover curves indicated that the seismic capacity/DLSs for columns along the service life were time-dependent and followed lognormal distributions. The incremental dynamic analysis curves and seismic fragility curves implied that chloride-induced corrosion typically led to a substantial increase in the failure probability of columns. In comparison with the correlated stochastic method, considerable underestimations of component level fragility across different damage limit states were obtained using the deterministic approach, which highlighted the importance of accounting for the variability of mechanical properties of corroded steel bars in the time-dependent seismic fragility analysis. • The increasing variability of reinforcement mechanical properties was considered. • The distributions of time-dependent damage limit state were developed. • Stochastic methods were presented in time-dependent seismic fragility analysis. [ABSTRACT FROM AUTHOR]

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

The cable-strut structures have the features of low stiffness and weak damping, resulting in large vibration response under dynamic excitation. The vibration response of the cable-strut structures can be reduced by active control methods. However, many traditional active control methods need to build a state-space model (SSM) based on finite element model (FEM), and solving the active control force for the high-dimensional SSM is time-consuming. In this paper, the dynamic mode decomposition with control (DMDc) method is proposed to achieve a data-driven reduced-order SSM for active vibration control of cable-strut structures. This proposed method only uses the data of structural response and control force input to build reduced-order SSM and does not rely on the FEM. Linear quadratic regulator (LQR) design using the DMDc-based reduced-order SSM (DMDc-LQR) is more computationally efficient than that using the FEM-based SSM (FEM-LQR). The relationship between the design parameters of the DMDc-LQR controller and the FEM-LQR controller is established, which ensures that the control performance indexes of the DMDc-LQR controller and the FEM-LQR controller are equal. The effectiveness of the proposed DMDc-LQR method is validated using numerical Kiewitt cable dome and tensegrity grid under wind and seismic loads. The results show that the DMDc-LQR controller maintains similar control effect to that of the FEM-LQR controller and has advantage of high computing efficiency as well. In addition, the influence of critical parameters (i.e., data noise and model order) on vibration control effect is comprehensively explored. It is found that increasing the model order is effective to mitigate the noise influence on the DMDc-based reduced-order SSM and ensures the effectiveness of the DMDc-LQR controller. • A data-driven reduced-order state-space model (SSM) method is proposed. • The linear quadratic regulator (LQR) is designed based on reduced-order SSM. • The control effect and design efficiency of two LQR controllers are discussed. • The influence of noise and model order on the vibration control effect is explored. [ABSTRACT FROM AUTHOR]

This paper presents experimental and numerical investigations into the post-fire cross-section compressive behaviour and resistances of circular recycled aggregate concrete-filled stainless steel tube (RACFSST) stub columns. Twelve stub column specimens, fabricated from concretes with three recycled coarse aggregate replacement ratios (0%, 35% and 70%), were tested after exposure to the ISO-834 standard fire for 0 min (i.e. at ambient temperature), 15 min, 30 min and 45 min. The experimental investigation included heating and cooling of specimens, cylinder tests and post-fire tensile coupon tests and stub column tests. The test results, including load–end shortening curves, failure loads and failure modes, were fully reported and the initial compressive stiffnesses and confinement effect were discussed. The numerical investigation was subsequently conducted, where thermal and mechanical finite element models were developed and validated against the test results and then used to perform parametric studies to generate further numerical data. Given the absence of design codes for stainless steel–recycled aggregate concrete composite structures after exposure to fire, the relevant design rules for circular natural aggregate concrete-filled carbon steel tube stub columns at ambient temperature, as set out in the European code, Australia/New Zealand standard and American specification, were assessed, using post-fire material properties, for their applicability to circular RACFSST stub columns after exposure to fire, based on the test and numerical data. The assessment results generally revealed that the European code and the Australian/New Zealand standard led to an acceptable level of design accuracy and consistency, while the American specification resulted in rather conservative and scattered post-fire cross-section compression resistance predictions. • The compressive behaviour of circular RACFSST stub columns after exposure to fire is investigated. • Post-fire compression tests on twelve circular RACFSST stub column specimens are conducted. • The influences of heating durations and RCA replacement ratios are analysed. • Thermal and mechanical FE models are validated against test results and then used to conduct parametric studies. • The relevant design codes are assessed against the test and FE data. [ABSTRACT FROM AUTHOR]

The use of cold-formed steel (CFS) built-up sections in engineering practice is widely gaining popularity due to their ability to provide sustainable solutions and optimised section design opportunities. This paper presents an experimental and numerical investigation conducted on CFS built-up stiffened box section columns under axial compression. A total of 13 new experimental tests were conducted with specimens having an overall web depth up to 550 mm. Detailed nonlinear elasto-plastic finite element (FE) models were then developed and verified against the test results. Upon verification, a parametric study involving 144 FE models was carried out to investigate the effects of section thickness, column length, and screw spacing on the buckling resistance of CFS built-up stiffened box sections. The test and finite element analysis (FEA) results were compared with the buckling resistances determined by the American Iron and Steel Institute (AISI S100) and Australian and New Zealand Standards (AS/NZS 4600). It was found that the buckling resistances determined by the AISI S100 and AS/NZS 4600 for CFS built-up stiffened box sections were conservative by 9.3% on average, compared to experimental and FEA results. Modified Direct Strength Method (DSM) design equations for predicting the buckling resistances of CFS built-up stiffened box sections were then proposed, and a reliability analysis was conducted to assess the feasibility of the proposed equations. • Buckling resistance of axially loaded CFS built-up stiffened box sections was studied experimentally and numerically. • A nonlinear finite element model was developed and validated against the test results. • A parametric study was conducted to investigate the effects of different parameters. • Assessment of the current design guidelines was conducted. • New design equations for predicting the buckling resistance were proposed. [ABSTRACT FROM AUTHOR]

The paper is focused on the numerical analysis of the efficiency of strengthening solutions dedicated to masonry arch bridges. An overview of common strengthening methods is described covering the most frequent techniques and their influence on the bridge's structural behaviour. The numerical study concentrates on the longitudinal behaviour of the arch of single-span bridges. The applied methods are related to the addition of specific structural components on both sides of the arch – extrados and intrados. Two basic solutions are studied based on a rigid or flexible layer corresponding to the most common techniques being applied to these bridges around the world. A comparison of the selected strengthening techniques is given considering their impact on the bridge's structural behaviour under incremental static loadings. Structural details of the solutions are given as well as their efficiency is evaluated through analytical and numerical analyses. Advanced nonlinear Finite Element models using a meso-modelling technique are presented and selected results showing the mechanical performance of the structure before and after strengthening are provided. The interpretation of the bridge model response parameters, representing the increment of resistance given by the addition of each reinforcement solution, is based on the analysis of the evolution of the structural failure modes up to the maximum load capacity of the bridges, namely in terms of the interaction of internal resistant forces M-N in representative arch cross-sections determined also analytically. Conclusions are formulated to identify optimal reinforcement solutions through the ratios of the maximum load capacity of strengthened and unstrengthened bridge cases, and the ratios between the areas of the M-N interaction diagrams of strengthened and unstrengthened solutions. • A methodology and a measure for strengthening efficiency evaluation of masonry arch bridges is proposed. • Advanced finite element model of strengthened masonry arch bridges is elaborated and calibrated. • The analytical approach is based on the interaction diagrams of normalised quantities μ and ν of the generalized forces. • The proposed strengthening evaluation utilises an original procedure combining advanced numerical and analytical solutions. • The procedure provides simultaneous consideration of all arch sections on the whole strengthened system global behaviour. [ABSTRACT FROM AUTHOR]

This paper presents a three-dimensional (3D) finite-element analysis of a light-frame wood panelized gable roof. The study developed equivalent macro elements representing the major roof components, such as the roof panel and support wall, in the finite-element model (FEM) by utilizing analytical models of the diaphragm and shear wall of CSA 086–19. The most critical load response of the panelized roof structure was obtained by considering the governing load cases, including the partial load case for snow load. The load path analysis revealed that the panelized roof had a two-way load distribution due to the deep beam action of the support wall. The gable ends of the roof carry approximately one-third of the load. In the gravity load case, the in-plane shear governed the connection design at the eave and support wall lines. Self-tapping screws were very effective in resisting wind uplift forces due to their high withdrawal capacity. Furthermore, the deflection pattern of the ceiling joist revealed the effect of panelized construction on the load path. • A holistic design enables the light-frame wood gable roof components to be fabricated using the existing production line. • A three-dimensional (3D) finite-element analysis of a light-frame wood panelized gable roof is presented. • Developed equivalent macro elements representing the major roof components. • The panelized gable roof had a two-way load distribution due to the deep beam action of the support wall. • The deflection pattern of the ceiling joist revealed the effect of panelized construction on the load path. [ABSTRACT FROM AUTHOR]

This paper proposes a new configuration of PRCFST (prefabricated reinforced strength concrete-filled steel tubular) column-column connection with transfer sleeves. First of all, five PRCFST column-column connections were conducted by monotonic loading tests. The failure modes, plastic deformation, and flexural capacity of column-column connections were discussed in detail. Secondly, the finite element analysis (FEA) model was validated in main indices and failure modes. Finally, the flexural performance of PRCFST column-column connections was investigated by parameter analysis. The parameters included width-thickness ratio (D / t), column cross-sectional size (D), anchorage length (l 0), and the number of steel bars (n), steel bars strength (f y,r), concrete (f c), and shear-span radio (L/D). The size effect is one of the main parameters to affect the flexural capacity of the PRCFST column-column connections. The flexural capacity of the PRCFST column-column connection increased with the l 0 , n and f y,r , while decreased with D / t. But the f c and shear-span ratio L / D play a little effect on the flexural capacity of the new PRCFST column-column connections. • Flexural behavior of RCFST column-column connections with transfer sleeves under monotonic loading was investigated. • The damages of RCFST column-column connections were concentrated on the concrete in the steel bars anchorage on the web side and the flange side of the upper column. • The reliability of the developed finite element models for RCFST column-column connections was verified. • 21 additional FEA models were developed to perform the parametric analysis of 7 different variables. [ABSTRACT FROM AUTHOR]

Thick rubber bearings (TRBs) are used for the mitigation of subway-induced vibrations in over-track buildings. TRBs might be loaded in tension in tall buildings, thus their tensile behavior needs to be explored. This paper performs numerical and analytical investigations on the tensile properties of TRBs. First, constitutive laws describing the rubber material under tension beyond cavitation were developed via a two-phase softening model, using the UHYPER user subroutine in ABAQUS. Then, parametric FE analyses were carried out to explore the effects of the shape factors, the thickness of the steel shims and the offset displacement on the tensile properties of TRBs. The numerical results showed that decreasing the first and second shape factors reduced the tensile stiffness of bearings, although the influence of the first shape factor seems marginal, when it is larger than 10. The code specified steel shim thickness (2 mm) seemed adequate, while reducing it to 0.5 mm or 0.2 mm could lead to local buckling of the shims, especially for bearings of lower first shape factors. The reduction of the tensile stiffness and yield force due to shear displacement was quantified. Finally, an analytical model that captures the tensile behavior of the bearings under cyclic loading was proposed and validated on published experimental tests. • Finite element models of bearings considering cavitation softening of rubber were built. • A parametric study was performed to study the influence factors on their tensile properties. • A new analytical model was proposed to predict their hysteretic behavior in tension. [ABSTRACT FROM AUTHOR]

Cutting-type structures, because of their desirable mechanical characteristics, high energy absorption capabilities and excellent guiding performance, has been extensively employed in high-speed trains. Its lightweight design and optimization problems are also the hotspot of research directions in present. This paper designed a new-type structure, i.e., magnesium alloy cutting-type energy-absorbing structure (CTEAS), taking into account its excellent properties of high lightweight level and ease of processing demonstrated through AZ31B magnesium alloy tensile mechanical test. Subsequently, experimental study on magnesium alloy CTEAS are conducted by trolley impact tests of train considering different cutting depths and different velocity levels. The results confirmed the outstanding advantages, including high lightweight level and higher absorbed energy properties, and lower demands of knives, compared with the structures with Q345 steel. In addition, the mechanism of knives cracking and melting phenomenon found in the experiment is explored by finite element analytical method. The results show that the temperature difference between the high-temperature surface and the interior during the cutting Q345 steel process is maybe the key influencing factor leading to knives damage. This research provides an effective tool for the design and analysis of excellent performance energy absorbing structure of high-speed trains. • AZ31B magnesium alloy can be used to cutting-type energy-absorbing structures. • Magnesium alloy structure has outstanding advantages in lightweight and higher SEA. • Temperature of the tools during the cutting process of Q345 steel is more than 900 °C. • Temperature of the tools is less than 800 °C when AZ31B magnesium alloy is cut. [ABSTRACT FROM AUTHOR]

Surface ruptures resulting from seismic faulting have the potential to inflict substantial damage to bridges straddling fault lines; hence, it is imperative to investigate the impact of ground motions documented on either side of fault rupture planes—termed as across-fault ground motion—on the seismic resilience of bridges. In this paper, the object of study is a three-span, simply supported beam bridge traversing a strike-slip fault. Utilizing the LS-DYNA finite element software platform, a sophisticated three-dimensional finite element model of the selected bridge is constructed, meticulously accounting for material damage nonlinearity and structural collision contact nonlinearity. A synthetic across-fault ground motion serves as the excitation for the seismic analysis of the bridge, systematically examining the influence of the fault-crossing angle (FCA), fault sliding rise time, and ground surface permanent rupture displacement on the dynamic response and seismic damage incurred by the simply supported beam bridge. The findings demonstrate that a diminutive fault-crossing angle (FCA) corresponds to an elevated risk of longitudinal beam collapse when a simply supported beam bridge does not intersect a fault vertically. The impact of the fault sliding rise time on the magnitude of seismic response and damage sustained by the simply supported beam bridge is relatively minuscule and can be neglected. Conversely, the ground surface permanent rupture displacement profoundly influences the dynamic response and seismic damage of the bridge. The emergence of fling-step pulses from the development of ground surface permanent rupture displacement amidst seismic activity induces a shift in failure mode-from the designer-intended bending failure to an unforeseen shear failure. • A FE model of a simply-supported beam bridge is established with consideration of material and contact nonlinearity. • The systematic parameter analysis of the simply-supported beam bridge is conducted. • The failure mode and damage process of the simply-supported beam bridge are revealed. • Recommendations for the seismic design of simply-supported beam bridges subjected to strike-slip faulting are drawn. [ABSTRACT FROM AUTHOR]

Finite element model updating (FEMU) is a frequent method for minimizing the differences between actual and predicted bridge structural behavior. However, static model updating for long-span bridges usually requires load tests to obtain the response under known static loads, which is costly due to long traffic interruptions. To offset this disadvantage, a static FEMU method based on long-term monitoring data is proposed to update the model in real-time by taking stochastic traffic loads with certain statistical characteristics as known static loads. First, the theoretical relationship between stochastic traffic flow statistical characteristics, static response statistical characteristics, and structural stiffness parameters is established. An objective function based on the probability characteristics of the long-term vehicle-induced response is constructed. Then, the FEMU process based on monitoring data is introduced, including the acquisition of the finite element model vehicle-induced response, the extraction of the actual vehicle-induced response based on the monitoring data, the selection of model updating parameters, and the application of the global-local parameter updating optimization method. Finally, the effectiveness of the proposed method is verified by applying numerical examples and real bridge examples to a long-span suspension bridge. It can be concluded that the proposed method can achieve FEMU based on long-term monitoring data, avoiding the inconvenience and large cost caused by load tests. The accuracy and efficiency of the model updating can meet the engineering requirements well through comparison with the result of the traditional load test method. • This paper presents a static finite element model updating method based on the statistical characteristics of long-term monitoring data during normal operation, avoiding the inconvenience and large cost caused by the previous model updating method based on the load test. • The proposed method takes stochastic traffic load with known probability characteristics as known static load, and can realize model updating well by reducing the error of the actual response probability characteristics and finite element model prediction response probability characteristics. • The probabilistic characteristics of long-term vehicle-induced static response are related to structural stiffness parameters and probabilistic characteristics of stochastic traffic flow. When the probabilistic characteristics of stochastic traffic flow are the same, the static response probabilistic characteristics are related to only the structural stiffness parameters. [ABSTRACT FROM AUTHOR]

This paper reports experimental and numerical investigations into the structural behaviour and resistances of high strength concrete-filled stainless steel tube (HCFSST) beam-columns under combined compression and bending. An experimental investigation was conducted on sixteen HCFSST beam-columns specimens fabricated from stainless steel tubes with two cross-section sizes and high strength concretes with four material grades, and included concrete cylinder tests, tensile coupon tests, initial global geometric imperfection measurements and eccentric compression tests. The test setups and procedures were fully reported and the experimental observations were discussed and analysed in detail. It was found that the plane cross-section assumption was valid for eccentrically loaded HCFSST sections and the lateral deflection distribution patterns for HCFSST beam-columns were approximately half-sine wave shapes. The test results were used in a subsequent numerical investigation for the validation of finite element models, which were then employed to conduct parametric studies to generate additional numerical data over a wide range of cross-section dimensions, member lengths and loading combinations. Based on the experimental and numerical results, the relevant design rules, as set out in the European code, American specification and Australian/New Zealand standard, were evaluated for their applicability to HCFSST beam-columns. The evaluation results revealed that the European code provided accurate but scattered failure load predictions when used for HCFSST beam-columns, while the American specification and Australian/New Zealand standard resulted in conservative and scattered failure load predictions. • The behaviour of high strength concrete-filled stainless steel tube (HCFSST) beam-columns is investigated. • Eccentric compression tests on sixteen HCFSST beam-column specimens are conducted. • The ductility, strength, longitudinal strain development and lateral deflection distribution are analysed. • FE models are developed to validate against the test results and then used to conduct parametric studies. • The applicability of relevant design codes is assessed against test and FE data. [ABSTRACT FROM AUTHOR]

An improved plate deep energy method without penalty terms is introduced to study the bending, free vibration and buckling problems of irregular Kirchhoff plates. The finite difference produced by convolution operation is employed for a faster calculation of derivatives and enforcement of boundary conditions. Most deep learning based neural network methods adopt the penalty method to impose boundary constraints, which may cause convergence issues especially when dealing with complex solution domain or mixed boundary conditions. In this paper, the R-function is utilized to build the distance function multiplied by the neural network output to meet the Dirichlet boundary constraints, while the boundary constraints expressed by derivative functions are applied by introducing virtual nodes. With such treatments, the boundary losses of a plate system can be avoided. To validate the proposed method, numerical examples considering plates with irregular shapes and mixed boundary conditions are studied, and the results are compared to those provided by the theoretical solutions, finite element method (FEM), and literature. • An improved plate deep energy method is proposed for the mechanical analysis of Kirchhoff plates. • The method is applicable to irregular solution domains by introducing coordinate transformation and R-function theory. • The training efficiency and enforcement of derivative boundary conditions are improved by using finite difference theory. [ABSTRACT FROM AUTHOR]

To promote the reuse of precast concrete pavement units, an innovative demountable stainless steel bar connection system is proposed in this paper. Monotonic load tests were conducted to investigate the effects of the width of the stainless steel bar connection, the width and the end distance of the stainless steel plate on the mechanical behaviour of the proposed connection system. As localised concrete crushing was observed after tests, the stainless steel bar connection system was updated with an expanded contact area between concrete and steel. Test results revealed that specimens with the updated connection system exhibited high initial stiffness with low concrete compressive stress concentration. Finite element analysis (FEA) was then carried out to further investigate the parameters that affected the structural performance of the updated connection system. According to the deformations of the stainless steel bar connection and high-strength bolts, an analytical approach was developed to predict the design load of the proposed connection system. Design recommendations were finally summarised based on the obtained test and parametric analysis results to guide the demountable connection design. • The demountable connection system can achieve reusability of precast pavements. • Stainless steel bar connection can be reused in precast concrete pavements. • Demountable connection system performs high initial stiffness and ultimate load with low compressive stress concentration. • Analytical solution to predict the design load of the demountable connection system is derived. • Design recommendations on the demountable connection system are proposed. [ABSTRACT FROM AUTHOR]

Metamaterial structures that exhibit negative stiffness (MSNS) behavior have shown the potential to be used as energy dissipation systems in different applications. Negative stiffness honeycomb structures consist of multiple pre-buckled beams that snapping through from one pre-buckled mode to another buckled mode, when subjected to transverse loads, displaying negative stiffness, and dissipating a significant portion of the input energy. This paper presents finite element models (FEMs) developed to investigate the performance of negative stiffness pre-buckled beams and honeycombs. The FEMs were validated using experimental results of single pre-buckled beams and honeycomb structures. The experimental testing of the pre-buckled beams was presented in the current study while the results of the honeycomb were available in the literature. The FEMs have the ability to capture the transition of the elements from one mode of buckling to another mode as well as the force thresholds, energy dissipation values, and residual displacements. The FEMs were extended to investigate the effect of different parameters such as boundary condition, apex height-to-beam thickness ratio, and constraining the second mode of buckling on the behavior of negative stiffness honeycombs. • Metamaterial structures that exhibit negative stiffness (MSNS) have potential for use in energy dissipation systems. • Finite element models (FEMs) are presented to study the performance of MSNS beams and honeycombs. • FEMs are validated using experimental results from single pre-buckled beams and honeycomb structures. • FEMs can accurately predict transitions between different modes of buckling, force thresholds, and energy dissipation. [ABSTRACT FROM AUTHOR]

The use of advanced analysis techniques harnessing the capabilities of the currently available computational resources can lead to considerably more accurate fire design of steel structures relative to the currently adopted simple fire design methods in practice. In this paper, a structural steel fire design method by Geometrically and Materially Nonlinear Analysis with Imperfections (GMNIA) and using strain limits is put forward for the fire design of steel beams and beam–columns. In the proposed fire design method, the GMNIA of a steel member or structure is performed using computationally efficient beam finite elements and strain limits are adopted to account for the detrimental effects of local buckling on the ultimate capacities. To verify the accuracy of the proposed method, extensive numerical parametric studies are conducted through shell finite element modelling. The results indicate that the proposed approach provides accurate and safe ultimate resistance and limit temperature estimations for steel beams and beam–columns in fire, with a considerably higher level of accuracy and reliability relative to the provisions of the European structural steel fire design standard EN 1993-1-2. • A structural steel fire design approach by GMNIA with strain limits is proposed for steel beams and beam–columns. • The deleterious factors influencing structural resistance in fire are fully considered in the proposed design approach. • The failure modes of steel members can be explicitly taken into consideration in the application of the proposed method. • Safety and accuracy of the proposed method are thoroughly verified. • The proposed approach results in significantly higher accuracy and reliability in comparison to simple calculation models of Eurocode 3 Part 1.2. [ABSTRACT FROM AUTHOR]

This paper investigated both experimentally and numerically the flexural performance of two–span beams after being strengthened with polyparaphenylene benzobisoxazole (PBO) fiber–reinforced cementitious matrix (FRCM) systems at different hogging–to–sagging (H/S) strengthening ratios. The test results revealed that the enhancement in the flexural response of the strengthened beams was highly dependent on the strengthening configuration and the number of layers used in both the hogging and sagging sections. The H/S ratio had a notable effect on the failure modes of the hogging sections only whereas the sagging sections showed similar failure modes regardless of the H/S used. Strengthening the sagging sections governed the ductility of the tested beams with a slight effect of the H/S ratio on their ductility. Despite strengthening, the hogging sections were capable to redistribute up to 37% of their moments to the sagging sections, which represented 93% of the redistribution capacity of the unstrengthened sections. This finding suggests the revision of the CSA and ACI formulations that prohibit any moment redistribution in the design of externally–bonded strengthened elements. The developed finite element model accurately predicted the experimental results in terms of the failure modes, the load–carrying capacity, the ductility, and the moment redistribution ratios between the critical sections. • Using different H/S strengthening ratios change the failure modes of the hogging sections rather than the sagging sections. • Strengthening the sagging sections governed the ductility of the beams rather than the hogging strengthening. • Strengthened beams can redistribute between 23% and 37% of the moments between their critical sections. • It is important to consider the continuity of the FRCM–strengthened structures in the design equations of ACI 549.4 R (2020). • The numerical model reasonably predicted the moment redistribution ratios of the beams. [ABSTRACT FROM AUTHOR]

In the traditional steel beam-column connection, the beam flanges were welded to the column face, while the beam web was bolted to the column face by shear tab. During seismic events, this connection often suffers from brittle failure. This paper presents a novel self-centering steel connection with dual energy dissipation mechanism. The connection utilizes the sliding of friction elements and the plastic deformation of T-stub at different stages to dissipate energy. As a result, the proposed connection not only enhances energy dissipation capacity but also increases the safety redundancy of the structure. The main focus of this study is to investigate the structural behavior of this new type of connection by refined finite element analysis models. These models are constructed using ANSYS and validated against experimental results. Furthermore, parametric analysis is conducted to investigate the influence of various factors on the seismic performance of the connection. These factors include the initial post-tensioning force of prestressed steel strands, the shape form of T-stub flange, the flange thickness of T-stub, the coefficient of friction between friction plates and web of T-stub, and the pre-tension force of high-strength bolts. The results demonstrate that increasing the initial post-tensioning force of the steel strands reduces the residual deformation and enhances the self-centering ability of the connection, and the dual energy dissipation behavior is more obvious. Meanwhile, the occurrence of both sliding and plastic deformation of T-stub is postponed. The influence of the thickness of the T-stub flange is minimal during the friction-based energy dissipation stage but significant during the energy dissipation stage of the plastic deformation of T-stub. Moreover, increasing either the coefficient of friction between friction plates and T-stub webs or the initial post-tensioning force of high-strength bolts significantly improves the bending strength of the connection and reduces residual deformation. Meanwhile, these factors mostly affect the friction sliding stage to delay the starting point of sliding, but their influence on the plastic deformation is minimal. Finally, a theoretical hysteretic model is proposed based on the dual energy dissipation mechanism. The model is compared and analyzed against experimental results, demonstrating good agreement. This provides theoretical foundation for the design of similar structural connection. • The behavior of self-centering connection with dual energy dissipation mechanism was studied. • Effects of various factors were comprehensively assessed. • Hysteretic model was established. [ABSTRACT FROM AUTHOR]

The flexural buckling behaviour and resistances of press-braked stainless steel Z-section columns are investigated in this paper, based on experiments and numerical modelling. An experimental investigation was conducted on two press-braked stainless steel Z-sections and included material testing, initial geometric imperfection measurements and twelve fixed-ended column tests. Minor-axis flexural buckling was observed for all press-braked stainless steel Z-section column specimens upon testing. The key obtained fixed-ended column test results, including failure loads, load–deformation histories and failure modes, were fully reported. Following the experimental investigation, a numerical investigation was performed, with finite element models developed to validate against the fixed-ended column test results and then used to conduct parametric studies to generate additional numerical data. On the basis of the test and numerical data, the relevant buckling curves, as specified in the European code, American specification and Australian/New Zealand standard, were evaluated and shown to provide accurate and consistent flexural buckling resistance predictions for press-braked stainless steel Z-section columns. • The flexural buckling behaviour of press-braked stainless steel Z-section columns was studied. • Twelve fixed-ended column tests were conducted. • FE models were developed to validate against the test results and then used to perform parametric studies. • The codified buckling curves were assessed, showing good design accuracy and consistency. [ABSTRACT FROM AUTHOR]

In predicting the capacity of screw anchors under static tensile loading, the Concrete Capacity (CC) method is the state-of-the-art prediction model which covers concrete cone capacities in uncracked and cracked concrete up to 0.3 mm crack width. However, in seismic applications, anchors may be subjected to large crack widths of up to 0.8 mm. With large crack width, the behaviour of small-sized (typically 6 mm) screw anchors has not been studied. In this study, experimental investigations were conducted for a total of 29 anchors in uncracked and cracked concrete with large crack widths up to 0.8 mm. The experimental results showed that the load-carrying capacity of screw anchors significantly dropped resulting in a reduction factor of 0.13–0.47 for cracked concrete with 0.8 mm crack width (significantly lower than 0.7 assumed by the CC method for a crack width of up to 0.3 mm). This paper focused on developing modelling technique for predicting the performance of screw anchors in cracked concrete with a crack width of up to 0.8 mm since screw anchor in cracked concrete has not been studied using finite element analysis. Three-dimensional finite element models were developed for screw anchors in uncracked and cracked concrete and validated by the experimental results. Further, parametric analysis showed that dilation angle and shape factor are the two most influencing parameters among other of the concrete damage plasticity model. • Behaviour of 6 mm screw anchors in cracked concrete of large crack width up to 0.8 mm. • Finite element analysis of screw anchors in cracked concrete with large crack width. • Parametric analysis of concrete parameters of concrete damaged plasticity (CDP) model. [ABSTRACT FROM AUTHOR]

• Continuum damage and brick-to-brick modeling techniques are compared. • A masonry wall strengthened with bed joint reinforced repointing is considered. • For un-strengthened case, all models provide accurate predictions of crack pattern. • For strengthened case, the simplified brick-to-brick model provides the best results. • Modelling of pre-damage should be considered with care. Bed joint reinforced repointing is a retrofitting technique for unreinforced masonry structures that is commonly applied in the Netherlands to repair settlement-induced damage. Using this technique, the bed joints of masonry walls are reinforced with steel rebars that are embedded in a high strength repair mortar. Due to the increase of induced seismic events in the northern part of the Netherlands, an experimental study was carried out at Delft University of Technology to investigate the performance of this retrofitting technique for combined settlement and seismic loading. This paper aims to simulate the experimental results, with a focus on the comparison of different finite element modelling approaches for studying both un-strengthened and strengthened full-scale tested walls. To that end, three different models are investigated – comprising both macro (continuum) and simplified and detailed micro (brick-to-brick) modelling approaches. The bricks and mortar joints are modelled as one homogenous continuum in the macro model, whereas in the two brick-to-brick models these structural components are modelled separately, with the detailed model including interface elements to simulate the brick–mortar bonds. Nonlinear pushover analyses are subsequently carried out using all three modelling approaches, for both monotonic and cyclic loading cases. Based on these analyses, the detailed brick-to-brick model was found unsuitable to simulate the strengthened wall because cracks in the model mainly occur in the form of opening of the brick–mortar bond interfaces, while smeared cracking in the plane stress elements of the mortar joints is very limited. Similarly, the continuum damage model was found to be inaccurate when pre-existing damage in the experiment needed to be taken into account. The continuum damage model also showed lower axial stresses in the rebars, compared with the simplified brick-to-brick model, as the former does not allow for the direct assignment of material properties for the high strength repair mortar in the strengthened joints. [ABSTRACT FROM AUTHOR]

• New computer-aided optimization design and additive manufacturing paradigm for steel joints in spatial grid structures is proposed. • Parametric topology optimization design method and numerical model for optimized joints are developed. • The structural performance of the optimized joints is investigated and compared with traditional joints. • A case study on double-layer spatial grid structure with hundreds of joints is presented to illustrate the applicability of the proposed paradigm. • Representative optimized joint is additively manufactured by selective laser melting using 316L stainless steel. This paper presents a complete computer-aided workflow for the parametric topology optimization (TO) design, numerical analysis and additive manufacturing (AM) of steel joints in spatial grid structures. A fully parametric TO design framework for steel joints in spatial grid structure was developed based on the Grasshopper platform. The joint models were parametrically established based on subdivision surface technology and further topology optimized through the bi-directional evolutionary structural optimization (BESO) algorithm with the support of cloud computing server. The structural performance of the optimized joints was thoroughly investigated via the parametric finite element analysis. Variables of loading conditions and TO parameters (target volume and filter radius) that affect the compliance, maximum displacement, maximum stress and stress distribution were taken into account. Analysis showed that the target volume governed the joint structural behaviour while the filter radius affected the geometric details of optimized joint. The practicability of proposed workflow was demonstrated through a parametric optimization design framework of a double-layer spatial grid structure with hundreds of steel joints. A typical optimized joint made of 316L stainless steel was additively manufactured using selective laser melting. This workflow is highly automatic and featured by high design flexibility and integration degree as well as good transplanted ability. [ABSTRACT FROM AUTHOR]

• Developed a new type of fiber-reinforced seismic isolator with low cost and high-performance features. • Tensile and bending performance tests were conducted on the fiber-reinforced plastic plates. • Evaluated FRP seismic isolators' mechanical properties, including the vertical compressive performance, horizontal shear performance, ultimate performance, shear strain correlation, compressive stress correlation and loading frequency correlation by mechanical properties tests. • Studied the distributions of horizontal normal stress, vertical normal stress and interfacial shear stress in the isolator by numerical analysis. • Studied the effects of changing the plane size of the FRP seismic isolator and the plate/rubber thickness ratio on the isolator's performance. Seismic isolators are widely used in the field of seismic mitigation. But the disadvantage of the high cost limits the promotion of seismic isolators in underdeveloped areas. Therefore, the development of a new type of low-cost seismic isolator will facilitate the application of seismic isolation technology. This paper proposes a fiber-reinforced plastic (FRP) seismic isolator with cost-effective and stable mechanical performance features, which uses a synthetic material of alkali-free fabrics and vinyl resin instead of the steel plate in the traditional laminated isolator. The design and manufacturing process of the bearing makes it have higher stability and integrity than the traditional bearing. A series of mechanical properties tests were conducted to investigate the mechanical behavior of the FRP seismic isolator and to determine the boundary properties of the FRP seismic isolator. The stress distributions inside the FRP seismic isolator are analyzed detailly by the finite element model. The effects of changing the plane size of the FRP seismic isolator and the plate/rubber thickness ratio (P/RTR) on the isolator performance were studied to provide technical support for the subsequent design and manufacture of FRP seismic isolators. The experimental and numerical analyses show that the FRP seismic isolators developed in this paper have good performance and are beneficial for application in low-rise building structures. [ABSTRACT FROM AUTHOR]

• A refined finite element model for screw connections is proposed. • The pull-out strength and the thread pitch are negatively correlated. • The failure modes are divided into screw hole extrusion and thread shear failure. • The evaluation results reveal that current design formulas are conservative. • The trend of values predicted by a reference is consistent with theoretical line. Screw connections have been extensively used in cold-formed steel constructions due to convenient construction and high capacity. However, little attention has been paid to the pull-out performance and parametric effects of screw connections. In this paper, the pull-out performance of screw connections is experimentally and numerically investigated. The objective of this study is to develop a refined finite element (FE) model that can be used to parametrically analyze the pull-out performance of screw connections. Eight sets of experimental results are selected for comparison with the FE results to validate the accuracy of the FE model. Based on the validated FE model, parametric analyses of the main variables in screw connections are conducted to discuss the effects of the tensile strength, the steel plate thickness, screw diameter and the ratio of thread pitch to plate thickness on the pull-out performance of screw connections. The results indicate that the failure modes of specimens are mainly classified into screw hole extrusion and thread shear failure. It is also found that the tensile strength, the steel plate thickness, screw diameter and the ratio of thread pitch to plate thickness have significant effects on the pull-out resistance of screw connections. Particularly, the numerically obtained pull-out resistance are used to assess the accuracy of the codified design rules for screw connections, as given in the Chinese Code, North American Specification, British Standard and European Norm. The evaluation results reveal that the current design formulas are relatively conservative. The formula proposed by one referenced paper is insecure, while the distribution trend is basically consistent with the straight line of P S / P FEM = 1.0 (the ratio of the calculated values to the FE values is equal to1.0), therefore, it can be used as a good reference for calculating the pull-out resistance of screw connections. Besides, the modified design formula in this study has good applicability. [ABSTRACT FROM AUTHOR]

• The mechanical performance of pre-hole isolation pile is studied by tests and FEM. • The dissipation capacity of piles is increased by the pre-hole isolation system. • The influence of damping material type and pre-hole size is investigated. • P-y curves for predicting the pre-hole isolation pile response are proposed. Under seismic actions, reinforced concrete (RC) piles are considered the most vulnerable components of integral abutment bridges (IABs). This paper investigates the mechanical behavior of the pile with pre-hole seismic isolation system through pseudo-static low cycle tests and numerical analyses on scaled specimens with various filling materials. The ultimate goal of this technical solution is to improve the seismic performance of IABs. The experimental results proved that the pile specimens with pre-hole seismic isolation system exhibit higher energy dissipation than those without pre-hole. The equivalent viscous damping is 17.1 ∼ 49.3 % higher when the filling is rubber and 3 ∼ 12 % higher using foam. The influence of the pre-hole diameter and soil deformation is also significant. When the pre-hole diameter is large enough, the horizontal displacement of the pile specimen is entirely absorbed by the rubber particles. Nevertheless, the pre-hole seismic isolation system does not significantly influence the failure mode, skeleton curve, yield load and bearing capacity. Finite element models (FEMs) were implemented in ABAQUS and calibrated using the experimental results. The FEMs allowed extrapolating the experimental outcomes under different geometrical and mechanical configurations, considering the sand-pile interaction with various filling materials (rubber particles and foam), and pre-hole sizes. The numerical results showed that the subgrade modulus and the ultimate soil resistance decrease when the pile has a pre-hole seismic isolation system. Therefore, the lateral deformation of a pile with pre-hole seismic isolation system can be estimated by multiplying the subgrade modulus used for the pile by a specific reduction factor dependent on the pre-hole geometry and the mechanical parameters of the filling material. The paper proposes and discusses a novel definition of the p - y curves for predicting the response of the pile with pre-hole seismic isolation system modified from classical p - y curves. [ABSTRACT FROM AUTHOR]

• A reliable and efficient anomaly detection approach for pile thermal integrity test is proposed. • A 1D finite element analysis accounted for cement heat of hydration, concrete mix and soil properties is developed. • A linear relationship between maximum temperature and effective pile radius is established through the FE model. • "The effective pile radius" can be reliably used to reconstruct as-built 3D shape and locate defective regions. • The method can identify anomalies inside or outside the pile reinforcement cage and provide quantitively evaluation. A review of the literature shows that pile integrity is a significant concern in pile construction; in particular, determining the location and nature of anomalies along the depth of the piles using thermal integrity testing data. This paper proposes a new anomaly detection approach which combines early-age temperature monitoring data and finite element back-analyses. A case study on a continuous flight auger (CFA) test pile with engineered inclusions was conducted using this new approach. Through 1D finite element analysis, a linear relationship between maximum temperature and effective pile radius is established. A crucial indicator – 'the effective pile radius' could be used to reconstruct as-built pile 3D shape and identify anomalous regions inside or outside the pile reinforcement cage. The data interpretation results of the field case study show that thermal integrity testing provides reliable information to identify anomalous regions within the pile. Compared to the conventional cross-hole sonic logging, thermal integrity testing used in combination with the new approach presented in this paper, can provide more reliable information in the pile integrity assessment process. [ABSTRACT FROM AUTHOR]

• Bayesian FE model updating of miter gate structural system is performed. • Two global surrogate models of the miter gate FE model are constructed using polynomial chaos. • Expansion and Gaussian process regression techniques. • A comparative study on model updating when relying on direct FE vs surrogate evaluations is performed. • Loss of accuracy in the model updating results and gain in computational time (including the training. Bayesian finite element (FE) model updating using direct model evaluations of large-scale high-fidelity FE models is extremely computationally expensive. Surrogate models can be used as fast emulators of FE models to accelerate the model calibration process. The physics/mechanics-based FE models are still the underpinning behind the surrogate models. This paper evaluates the loss in accuracy and the gain in computational time while performing Bayesian model updating by using surrogate model evaluations compared to using direct FE model evaluations. This evaluation is crucial before entirely relying on surrogate models in model updating for structural health monitoring (SHM) and damage prognosis (DP) purposes. This paper also demonstrates Bayesian updating and surrogate model construction of large-scale high-fidelity FE models of infrastructure systems. In this regard, the miter gate structural system is considered as the testbed structure. Three predominant damage modes (loss of contact between gate and wall, loss of thickness due to corrosion, and loss of tension in the diagonal rods) are considered for model updating purposes. Bayesian model updating is performed using direct FE evaluations by leveraging parallel computing. Two types of surrogates, namely polynomial chaos expansion (PCE) and Gaussian process regression (GPR), are developed for the miter gate. Model updating is performed again using the trained surrogate models, and the updating results are compared with their counterparts obtained using the direct FE evaluation results. The posterior distribution of the FE model parameters obtained using the trained surrogates are sufficiently accurate with respect to the posterior obtained utilizing the direct FE evaluations. In addition, an approximate 4-fold decrease in the computational time was observed when using surrogate model evaluations instead of direct FE evaluations for model updating. [ABSTRACT FROM AUTHOR]

Crowd induced dynamic loading in large structures, such as gymnasiums or stadiums, is usually modelled as a series of harmonic loads which are defined in terms of their Fourier coefficients. Different values of these Fourier coefficients that were obtained from full scale measurements can be found in codes. Recently, an alternative has been proposed, based on random generation of load time histories that take into account phase lags among individuals inside the crowd. This paper presents the results of some studies carried out in order to compare the existing load models used to simulate periodic jumpings and develop a new load model. Generally the testing is performed on platforms or structures that can be considered rigid because their natural frequencies are higher than the excitation frequencies associated with crowd loading. But in this paper, to validate these load models test have been performed on a structure designed to be a gymnasium, which has natural frequencies within that range. Test results have been compared with predictions based on the load modelling alternatives with quite good agreement. A calibrated finite element model of the structure has been used for this purpose. The new model provides a clear improvement in the energy contained within higher frequencies. [ABSTRACT FROM AUTHOR]

The ultimate strength of hollowcore slabs is greatly affected by their post-cracking behaviour. The composite action between the concrete topping and the hollowcore slab adds another level of nonlinearity. This paper presents a comprehensive finite element study to evaluate the nonlinear properties of the interface between a hollowcore slab and its concrete topping. The presented finite element modeling procedure was validated using data from a previous comprehensive experimental study by the authors. The nonlinear material behaviour of the concrete and the prestressing strands were also accounted for. The paper presents a modeling method that realistically simulates the staged construction technique of composite hollowcore slabs. Finite element results allowed understanding changes to the interface properties due to the confining effect of the applied load as well as the interaction between the shear and peel stresses. [ABSTRACT FROM AUTHOR]

The mechanical response of a wire strand is inherently complex because the helical wires undergo evolving stress and contact conditions as the strand is loaded. Further complications are added to the strand behavior if one or more of the wires break due to strand degradation over time. Although a detailed investigation on strand behavior is critically important for predicting the capacity of a broken strand as well as developing new monitoring approaches for wire break detection, there is little study available in the literature on wire breakage in a stressed strand. This paper provides an extensive investigation on stressing and post-breakage dynamic behavior of a prestressing strand. A finite element model is generally useful to study the global strand response, along with many localized phenomena that have strong influence on its performance, but are difficult to capture either experimentally or through closed-form analytical models. Investigations on certain behaviors, such as wire breaks, however, require a relatively large or even a full-scale model to adequately develop contact and frictional conditions. Moreover, such a sizeable model can account for any deviation points and may avoid edge effects. Consequently, several finite element parameters, such as the load ramp profile and duration, effects of damping and interwire friction, become critical for an accurate and efficient model. This paper first presents the use of a parametrized model to study strand behavior and evaluates the effects of these modeling parameters on strand response; load distribution and redistribution among the wires at the onset of interwire motion are also considered. The model is then used to simulate wire breakage in a prestressing strand, so that various aspects of post-breakage response can be examined. Numerical results show that a linear load ramp or stressing too quickly may lead to an inaccurate axial tension developed in the strand, whereas the inclusion of nominal mass-based damping has been found effective in achieving a quasi-static solution at a reasonable computational cost. In addition, the wire break simulation results indicate that breakage of an outer wire results in greater prestress loss than breakage of the center wire, which might have important implications for non-destructive wire breakage detection. [ABSTRACT FROM AUTHOR]

This paper deals with elastic shear buckling behavior of infill panels in sinusoidally corrugated steel plate shear walls, and fitting equations predicting the shear buckling loads are presented. Firstly by using finite element analyses (FEA), the previous formulae for bending rigidities of sinusoidally corrugated plates are revised, then pure shearing model are established to study the effects of key parameters on elastic shear buckling of sinusoidally corrugated infill panels, such as the aspect ratio, corrugation ratio, corrugation depth to plate thickness ratio and corrugation repeating number. Based on extensive FEA numerical results, fitting equations with good accuracy are proposed to estimate elastic shear buckling loads of sinusoidally corrugated panels, which are improved much compared with the solutions in previous studies. It is found that, the formulae for bending rigidities of corrugated plates revised in this paper are accurate compared with the previous ones. For sinusoidal corrugated infill panels, only global buckling and local buckling can be observed in the lowest buckling mode of eigenbuckling analysis, while interaction buckling is not obvious. The parameter of corrugation repeating number has a significant influence on elastic shear buckling loads, whereas it was neglected in previous studies. [ABSTRACT FROM AUTHOR]

This paper presents a dynamic explicit finite element (FE) simulation method to predict the highly nonlinear response of axially and rotationally restrained reinforced concrete (RC) beams at ambient temperature and in fire condition. Catenary action, developed during the large deflection behaviour of RC beams, is an important mechanism of resisting progressive collapse. This paper explains the numerical simulation challenges, including temporary instabilities, local failure of materials, non-convergence and long simulation time, and proposes methods to resolve these challenges. The effectiveness of the proposed simulation model is checked by comparison of the simulation results against relevant test results of restrained RC beams at ambient temperature and in fire. It has been found that using the explicit simulation method can follow the whole range behaviour of restrained RC beams until complete structural failure. Either load factoring or mass scaling may be used to speed up the simulation process. Damping can be applied to minimise significant dynamic effects following beam bending failure. This paper will give guidance on how to select the appropriate load factoring, mass scaling and damping values. [ABSTRACT FROM AUTHOR]

This paper develops a three-dimensional damage plasticity based finite element model (FEM) to study the ultimate strength of the steel–concrete–steel (SCS) sandwich shell structure under patch loading. The FEM considers complex geometric nonlinearities of hundreds of stud connectors in the structure, complex interaction between the connectors and concrete, and material nonlinearities of steel and concrete used in the structure. In the developed FEM, the concrete core material adopts the concrete damage plasticity model to predict the post-peak softening and residual strength; the stud connectors and steel shells adopt a continuum damage model to phenomenologically describe the damage evolution in the steel material. The reasonable agreement between FE analysis and the quasi-static tests on the SCS sandwich shell structure confirms the accuracy of the FEM in predicting the ultimate shear resistance, load–deflection relationship, cracks in the concrete core, and punching shear failure of the top steel shell. A subsequence parametric study based on the validated FEM investigates the influence of the curvature on the first peak resistance of the SCS sandwich structure. Finally, the paper validates accuracy of an analytical model on the punching shear resistance of the concrete core of the SCS sandwich shell. [ABSTRACT FROM AUTHOR]

This paper examines the effects of thermal restraint, caused by non-uniform temperature distribution in different members, on the failure temperatures of critical members of steel tubular trusses. Non-uniform temperature distribution develops in trusses exposed to localised fire attack. The truss member nearest to the fire source experiences the highest temperature, with reduced temperatures in the nearby members. The number of the nearby truss members being heated and their temperatures will affect the failure temperature of the critical truss member which has the highest temperature. The aim of this paper is to develop a simplified method to account for the effects of different numbers of members being simultaneously heated to different temperatures on the development of compression force and failure temperature of the critical member. Finite Element (FE) simulations were carried out for Circular Hollow Section (CHS) trusses using the commercial Finite Element software ABAQUS v6.10-1 which has previously been validated by the authors. The simulation trusses were subjected to constant mechanical loads and then increasing temperatures until failure. The elevated temperature stress-strain curves were based on EN-1993-1-2 [1]. Initial geometrical imperfections were included, based on the lowest buckling mode from eigenvalue analysis. The numerical study examined the effects of truss type, critical member slenderness, applied load ratio and axial restraint stiffness ratio on the failure temperatures of the critical truss members. The numerical simulation results were used to check the accuracy of a proposed simplified calculation method, combining linear elastic static truss analysis at ambient temperature and analytical equations to calculated the failure temperatures of thermally restrained truss members based on the regression equations of Wang et al. [2]. The calculation method was shown to be sufficiently accurate for fire resistant design purpose. [ABSTRACT FROM AUTHOR]

The paper deals with non-linear analysis of a telecommunication tower with circular flange-bolted connections (CFBCs). They are composed of two flanges, welded to the structural tubes, and then connected together with pre-tensioned bolts. A rigorous FEM analysis is performed for finding the connection stiffness in two cases. One deals with all bolts undamaged and the second one with one or more bolts broken. The analysis, which includes contact and friction forces, shows that when joints are under tension, the bolts are not only subjected to axial forces, but also to bending moments due the prying effect. The value of stresses caused by bending depends strongly on the bolt pre-tension and flange thickness. Removing one of the six connection bolts significantly increases stresses in the remaining bolts. Knowing the behaviour of the connection, it is possible to study the behaviour of the whole structure. This is achieved by applying the multilevel substructuring approach. The first levels is related to the flanges and bolts, whereby the connection model is simplified, and compared with the rigorous one, the second level is related to the assembly of the whole tower. The paper is illustrated with several examples of connections of different thicknesses, and different bolt pre-tensions. The considered tower comes from a real design. [ABSTRACT FROM AUTHOR]

This paper presents a systematic experimental and analytical study on the stability behavior of steel tube–coupler scaffolds (STCSs), wherein upper horizontal tubes transfer construction loads. Four specimens with common geometric sizes were constructed and tested statically in the lab to obtain the strength and failure modes. Advanced nonlinear finite element analysis, which considers the initial member imperfection and semi-rigid behavior of right-angle couplers, was conducted on the specimen models by using ANSYS to obtain the stress distribution, strength, and failure modes of the STCS. Analysis results were compared with the experimental results. The following can be concluded from the experimental and analytical results. (1) The main failure mode of the STCSs is the local instability of a vertical steel tube if the upper layer joints have sufficient anti-slipping capacity. Otherwise, the main failure mode is the slipping and fracture of right-angle couplers. (2) The strength of STCSs is sensitive to upper joint type. The load capacity of ST2 with the strengthened joint is 1.30 times that of ST1 with a common joint, and the load capacity of ST4 with a common joint is 1.16 times that of ST3 with a weak joint. (3) The numerical simulation method presented in this paper is generally consistent with the full-scale test results and has a maximum difference of 11.08%. [ABSTRACT FROM AUTHOR]