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Long integral bridges experience an enhanced cyclic soil structure interaction with their granular backfills, especially due to seasonal thermal loading. For numerical modelling of this interaction behaviour under cyclic loading, it is important to employ a suitable constitutive model and calibrate it thoroughly. However, up to the present, experimental data and calibrated soil models for this purpose with focus on typical well-graded coarse-grained bridge backfill materials are rarely available in the literature. Therefore, one aim of this paper is to present results of a comprehensive cyclic laboratory testing programme on highly compacted gravel backfill material. Based on this, a hypoplastic constitutive model with intergranular strain extension for small strain and cyclic behaviour is calibrated and evaluated against the experimental test data. The soil model's abilities and limitations are discussed at element test level. In addition, cyclic FE analyses of an integral bridge are conducted with several hypoplastic parameter sets from the literature and compared to the calibrated gravel backfill material. The investigation highlights that poorly-graded sands show significantly smaller cyclic earth pressures compared to well-graded gravels intended for the backfilling of a bridge. The soil structure interaction behaviour is clearly governed by the general soil model stiffness, including the small strain stiffness. [ABSTRACT FROM AUTHOR]

In this paper, an anisotropic non-associative constitutive model, based on the well-established critical state soil mechanics framework, is developed for the natural and reconstituted clays subjected to monotonic and cyclic loadings. A robust non-elliptical yield surface is implemented in the model which enables it to capture a wide variety of yield stress points. In addition to a realistic soil stiffness simulation, the employed flexible plastic potential surface equips the proposed model to predict a more accurate coefficient of earth pressure at rest. The model uses a combination of conventional volumetric and comprehensive rotational hardening rules to control the evolution of the yield surface caused by plastic strain increments. The adopted rotational hardening rule uses the concept of governing plastic strain increment which not only ensures the existence of the equilibrium state of anisotropy but also takes the effect of plastic strains at different constant stress ratios into account more sensibly. The proposed model is enhanced with a novel double-image stress point bounding surface plasticity type theory to capture nonlinear behaviour inside the yield surface, and also to simulate the cyclic responses. The detailed model formulation is discussed in both triaxial stress space and the e - ln p plane, and the important features of the model are elaborately explored. The capabilities of the model are also demonstrated by an extensive sensitivity analysis. In the end, the model is used to carry out simulations of monotonic and cyclic element tests on different clays and the results are compared with the available experimental data. [ABSTRACT FROM AUTHOR]

The behaviour of seismically damaged steel joints with reduced beam section (RBS) at elevated temperatures has not been widely investigated yet. Therefore, the study summarized in this article aimed to (i) analyse the response of RBS joints at high temperatures and (ii) investigate the influence of plastic damage, due to cyclic loading, on the fire performance of the joints. A set of RBS joints with rib stiffeners on the both lower and upper beam flanges was designed according to European standards and the following parameters were considered: (i) location of the joint (i.e., internal or external joint) and (ii) reduction in the beam flexural resistance (i.e., 65% or 80% of the beam plastic moment). The mechanical response of these joints was simulated by means of finite element models (FEM). The accuracy and effectiveness of the adopted modelling assumptions to mimic the seismic response of the joints were validated against experimental results available from the existing literature. The numerical results highlight that under cyclic loading, all investigated joints exhibit ductile behaviour, allowing the concentration of the plastic deformation within the reduced segment of the beam. The designed reduction in the beam flexural resistance influences the joint fire performance, being impaired in the cases with lower flexural resistance. In contrast, the imposed cyclic pre-damage does not appreciably affect the fire resistance of the investigated joints. [ABSTRACT FROM AUTHOR]

• Structural performance of hollow section concrete-filled GFRP columns under monotonic loads and cyclic loads experimentally assessed. • The influence of concrete strength and FRP tube thickness on the seismic performance of HS-CFGT columns is not independent of each other. • HS-CFGT columns made of high-strength concrete demonstrate commendable ductility. • Design approach for the initial flexural stiffness of the HS-CFGT columns was proposed. The experimental investigation and analytical reporting in this paper focus on the behavior of HS-CFGT members, specifically their response to both monotonic loads and cyclic loads. A total of 8 specimens, divided into two groups, each group with 2 kinds in loading type, including 6 columns under cyclic horizontal loads and 2 columns under monotonic lateral loads, were tested. The details of the experimental setups, procedures, significant observations encompassing failure modes, maximum bearing capacities, displacement corresponding to the peak load, load-displacement hysteretic curves, skeleton curves, stiffness degradation curves, and energy dissipation curves and were truthfully reported. The inspection of the experimental data has yielded several important conclusions regarding the effect of column parameters on the behavior of HS-CFGT columns. The most significant finding is that the influence of concrete strength and FRP tube thickness on the seismic performance of HS-CFGT columns is not independent of each other. Furthermore, the findings additionally suggest that HS-CFGT columns made of high-strength concrete demonstrate commendable ductility. The initial flexural stiffness for the preliminary design of HS-CFGT columns is also provided to facilitate the implementation of this innovative technology. [ABSTRACT FROM AUTHOR]

This work aims to present the first experimental tests investigating the cyclic behaviour of aluminium alloy beams. Box-shaped aluminium members were tested under non-uniform bending. Specifically, four square hollow sections made of 6060 aluminium alloy were subjected to cyclic bending loading. The manuscript presents key experimental results, including load-displacement curves, the number of cycles to failure, failure modes, and ductility properties. Additionally, a finite element model was developed using the ABAQUS software. A combined hardening law was implemented to model the non-linear behaviour of the aluminium material, and the element deletion technique was used to predict the actual fracture of the specimens. Finally, the accuracy of the FE model was assessed by comparing the numerical results with the experimental data. • Experimental tests on box-shaped aluminium beams under cyclic tests. • Material properties, failure modes, resistances, rotations and strain response of specimens have been provided. • Evaluation of local buckling effects on the cyclic behaviour of aluminium beams. • Definition of Finite element model by means of ABAQUS software. • Evaluation of the accuracy of FE model by comparing the experimental and numerical results. [ABSTRACT FROM AUTHOR]

This study presents the influence of phase change materials (PCMs) on the cyclic behaviour of mortars. A multi-scale analysis comprising mechanical and thermal tests was used to explain the phenomena involved. Mechanical and thermal cyclic tests were performed on four configurations of mortars containing 0%, 5%, 8%, and 10% of PCMs. It was revealed that mechanical cyclic loading did not significantly affect the resistance of mortars contrary to thermal solicitations. Indeed, it was shown that the incorporation of PCMs improved the thermal capacity of the mortars. However, severe degradation of the heat capacity and enthalpy was noticed after the temperature cycles. The physicochemical characterisation tests confirmed a moderate structural degradation, which primarily occurred in the initial cycles. Regarding the thermal cycles, scanning electron microscopy (SEM) and calorimetry characterisations corroborated the leakage of PCMs into the cement matrix, which was responsible for the degradation of latent heat. Finally, it was observed that the PCM–mortars resisted mechanical cyclic solicitations, at least up to 1000 cycles; however, they were still sensitive to repeated variations in temperature. [ABSTRACT FROM AUTHOR]

This paper presents a constitutive model enabled to simulate monotonic and cyclic behaviour of clay and sand in a unified framework. The bounding surface concept has been utilized to predict a smooth transition from elastic to plastic state of the soil. A new dilatancy relation is proposed to capture the volumetric behaviour of sand and clay in a unified manner. Moreover, closed hysteresis loops and accumulation of the plastic strain during cyclic loading have been regarded appropriately by transmitting the similarity centre of the loading and bounding surfaces in the stress space through a kinematic hardening rule. Furthermore, in order to improve the accuracy and convergence property of the model, an implicit integration scheme is introduced. Finally, the accuracy and performance of the model are verified using several experimental data from the literature. Both drained and undrained behaviours under monotonic and cyclic loading for sand and clay are considered, and the characteristic features of the behaviour are captured. [ABSTRACT FROM AUTHOR]

A rational and efficient seismic design requires a detailed characterization of the members and joints behaviour. The prediction of moment‐rotation response of steel beam‐to‐column joints under cyclic loading is not fully addressed in EN 1993‐1‐8 nor EN 1998‐1. Additionally, EN 1998‐1, requires experimental evidence for the use of dissipative steel beam‐to‐column joints. Therefore, new design tools are required to predict the cyclic behaviour of beam‐to‐column joints. In the scope of the European projects "EQUALJOINTS – European preQUALified steel JOINTS" and "EQUALJOINTS+ ‐ Valorisation of knowledge for European prequalified steel joints" a software that provides analytical predictions of cyclic and monotonic response of prequalified steel beam‐to‐column joints was developed. This software embodies the cyclic component method (CCM), which is an extension for cyclic loading of the component method, coded in EN 1993‐1‐8. The cyclic behaviour of the components, required to feed the CCM, can be gathered from experimental tests using specimens similar to the component to be characterized, e.g. T‐stubs. With this objective an experimental campaign on 14 T‐stubs was conducted at University of Coimbra. Results from tests and assessment of available models are presented in this paper. [ABSTRACT FROM AUTHOR]

• Cyclic tests on T-joints with CHS chord and passing-through plate are presented. • A FE model of the connection is built and validated against the experiments. • Parametric studies examining a wide range of geometrical properties are performed. • A GA tool is used to fit the simulated data with a phenomenological model. • A model predicting cyclic response from connection geometry is validated. This paper focuses on modelling the cyclic response of welded T-joints between Circular-Hollow-Section (CHS) chords and passing-through plates. Recent works have highlighted that, in practical applications, this specific joint typology can be regarded either as a standalone connection or as a component representing one of the main sources of deformability and energy dissipation capacity in more complex beam-to-column joints with CHS columns and passing-through I-beams. Currently, research efforts have primarily focused on predicting the strength and stiffness of this type of connection. However, there is a knowledge gap regarding the characterization of the cyclic response of joints with passing-through members, a crucial aspect for modelling steel structures with these connection types in seismic areas. In light of this, the paper aims to characterize the cyclic response of T-joints with CHS members and passing-through plates using a comprehensive approach that incorporates experimental, numerical, and analytical methods. Initially, the results of an experimental study examining the cyclic behaviour of T-joint specimens with passing-through plates are presented. Subsequently, models of the tested joints are implemented in Finite Element software and validated against the experimental outcomes. The validated models are used to conduct a parametric study, considering 44 different configurations to obtain their force-displacement cyclic responses. These responses are mathematically modelled using the hysteretic uniaxial material from the OpenSees library and a Genetic Algorithm based tool previously developed by the authors (MultiCal). Finally, regression analyses are performed to develop formulations for predicting the mathematical parameters of the hysteretic uniaxial material model starting directly from the geometrical and mechanical properties of the connection. This approach enables designers to model the cyclic response in structural analysis with a straightforward approach, without the need for new calibrations or tests, if the modelled joints fall within the proposed range of calibration. From the point of view of the component modelling, the approach presented aligns with the larger research strand devoted to the extension of the component method codified in Eurocode 3 part 1.8 to cyclic loading conditions. [ABSTRACT FROM AUTHOR]

Concrete-filled thin-walled galvanized corrugated steel tube (CFCST) is a novel composite member with competitive mechanical behaviour, durability and construction convenience. Several preliminary experimental and numerical works have been conducted on the compressive, flexural, shear, and monotonic torsional performances. However, the unique geometric characteristics of the helical corrugated steel tube (CST) may lead to significant torsional direction-dependent behaviour and complex cyclic torsional working mechanisms, which have not been investigated. This paper therefore presents an experimental investigation of the CFCST under cyclic torsional loads, encompassing the main test variables of member types, diameter-to-thickness ratios, axial compression ratios, and core concrete strengths. The failure modes, hysteretic curves, ductility, energy dissipation capacity, and stiffness degradation are carefully addressed. The cyclic torsional working mechanism of CFCST is discussed through the cyclic test results and strain analysis. The cumulative damage caused by the cyclic torsional loading case is also analysed via the comparisons between the monotonic and cyclic experimental results. The applicability of the existing design methods for the torsional bearing capacity is examined, with specific design suggestions proposed. • Nine specimens tested under cyclic torsional loads. • Torsional hysteretic behaviour addressed carefully and comparatively. • Cyclic torsional working mechanism discussed carefully. • Existing design methods for the cyclic torsional bearing capacity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Direct cyclic analysis combined with a phenomenological crystal plasticity model is used to simulate the cyclic behaviour of L-PBF 316L SS and to predict its shakedown limit. • Direct cyclic analysis accurately and efficiently computes the stable cyclic response of the material. • The critical combination of a defect and an unfavourable surrounding grain orientation can significantly reduce the shakedown limit. • Various local heterogeneous responses around a defect in the material L-PBF 316L SS were observed by simulation and it is suggested that they may be correlated with the scatter of the fatigue strength. The fatigue performance of Laser Powder Bed Fusion manufactured 316L stainless steel is critical for cyclic loading applications. Additive manufacturing of 316L produces a characteristic microstructure consisting of grains with a fine cellular structure within. This microstructure shows a comparatively high fatigue strength combined with a high defect tolerance. The purpose of this paper is to numerically analyse the local response of this microstructure to cyclic loading and, in particular, the joint action between lack of fusion defects and the surrounding grain structure. The traditional incremental analysis method for polycrystalline alloys is computationally expensive. Therefore, a direct cyclic analysis combined with a phenomenological crystal plasticity model is used in this work to predict the stable cyclic response of the material, resulting in a much lower computational cost. Three statistically equivalent representative volume elements are generated. The considered crystal plasticity parameters are calibrated using experimental tensile stress–strain curves. The comparison with incremental analysis demonstrates the accuracy and efficiency of the proposed method. The shakedown limit, based on the maximum load that allows the convergent cyclic response, significantly depends on the local grain orientation around lack of fusion defects, revealing a reason for the large scatter in the fatigue strength. [ABSTRACT FROM AUTHOR]

This study proposed a novel replaceable ductile Split-T (RDST) component located at the bottom beam flange to enhance the ductility and energy dissipation capacity of steel structures. The proposed RDST aims to effectively control damage and enable rapid recovery of structural functions in the aftermath of earthquakes. A series of cyclic loading tests under large deformation amplitude was conducted to investigate the plastic deformation capacity of this new type of structural component. The influence of shear span ratio on the specimens' hysteretic behaviours was studied experimentally. Meanwhile, experimental phenomena such as the pinching effect and snap-through buckling which compose the complicated deformation behaviour were evaluated quantitatively. Consequently, methods for quantitatively evaluating the mechanical properties of this new type of structural component were established based on the experimental results and previous discussions on T-stub-type structural components. Moreover, a hysteretic model was developed to precisely describe the specimens' complicated hysteretic behaviour. It is expected to be the key element for further research on the structures with this new type of beam-to-column connection. • Proposed a novel replaceable ductile Split-T (RDST) located at the bottom beam flange of steel frames. • Cyclic loading tests under large deformation amplitude were conducted. • The elasto-plastic behavior of RDST components under monotonic loading was precisely evaluated. • A hysteretic model precisely describing the complicated hysteretic behaviour of the specimens was developed. [ABSTRACT FROM AUTHOR]

With the aim of reusing assembled steel structures at the end of their service life or after experiencing earthquake damage, a novel demountable and reusable steel beam-to-column joint with bolted-pinned connection has been proposed herein. Its configuration is quite beneficial to the installation and disassembly due to its use of high-strength bolts and pins. The energy-dissipating connection plate (EDCP) is strategically placed in the predetermined energy dissipation area, of which the yield section is wrapped by an external restraining plate, allowing for concentrated damage and deformation of the main structural members within the elastic range under earthquake actions. The EDCP is fabricated from a low-yield-point (LYP) steel material that has excellent ductility and high energy dissipation capacity. To clarify the joint's static and seismic performance, ten joint specimens were designed and prepared, and both monotonic and cyclic loading tests were conducted. The failure mode, load versus displacement response, ductility, and energy dissipation capacity were obtained and analyzed experimentally. Furthermore, the cyclic behaviour of the same tested joints after disassembly and re-assembly were investigated to verify their reusability. The test results indicated that welding stiffening ribs in the unrestrained section of the EDCP can significantly enhance the joint's static loading capacity and seismic performance. Additionally, the damage of all the joints was localized within the EDCP, and no failure was observed in the beam, column components and column seat, which remained within the elastic range based on strain data analysis. It was found that the joint specimens could be disassembled effortlessly and efficiently with nearly no damage to the friction surface and bolt holes within the connection zone. Furthermore, the seismic performance of the re-assembled specimens was essentially identical to that of the original specimens, demonstrating the ability of reuse. • A new demountable and reusable beam-to-column joint is proposed. • Ten steel beam-to-column joints are tested monotonically and cyclically. • Failure modes, static and cyclic behaviour as well as capacities are clarified. • Demountability and reusability performance are evaluated. [ABSTRACT FROM AUTHOR]

The present experimental work is concerned with the application of geogrid as partial transverse reinforcement in reinforced concrete beams and exterior beamcolumn joints. The composite advantages of steel fibre with minimum percentage and geogrid in resisting the shear force of beam and beam-column joint specimens with increased stirrup spacing under static and reverse cyclic loading are studied in detail. The loaddeflection curve, hysteretic loop, post-elastic strength and stiffness degradation, energy dissipation, failure pattern and damage tolerance capacity are the parameters used in this study to evaluate the performance of adopted new confinement technique. The improved shear carrying capacity with better inelastic response represents the advantages of the geogrid in RC structural elements. Also the enhanced energy dissipation and better damage tolerance of composite action provided by geogrid and steel fibre authenticate the use of synergetic effect in resisting the shear force in RC beams and beam-column joints. [ABSTRACT FROM AUTHOR]

Part 1 [1] of this two-part paper presented an experimental study of the cyclic behaviour of a novel beam-to-column sleeve connection system for pultruded glass fibre reinforced polymer (GFRP) tubular profiles, and the numerical simulation of such behaviour. This Part 2 presents an experimental and numerical study on the sway behaviour of full-scale GFRP plane frames comprising the same tubular profiles and the aforementioned connection system. The GFRP frames were tested under quasi-static monotonic and cyclic loading, with and without infill walls, materialized by composite sandwich panels. The results of the tests show that high-load carrying capacity infill walls have a remarkable effect on the frames' structural behaviour, significantly increasing their stiffness and load carrying capacity, as well as their cyclic performance, namely regarding energy dissipation. On the other hand, such improvement involved extensive damage in the frame elements, particularly in the beams, which at some point compromised their structural integrity. The numerical study included the simulation of the cyclic tests of the unfilled walls, by means of relatively simple finite element (FE) models, comprising frame elements and spring joints simulating the behaviour of the connections, in which the Pivot hysteresis model calibrated in Part 1 [1] was used. The comparison between experimental and numerical results shows that these simple and design-oriented FE models can provide an effective (and conservative) tool for the simulation of pultruded GFRP frames under horizontal cyclic loads. [ABSTRACT FROM AUTHOR]

Wire arc additive manufacturing (WAAM) is an efficient and cost-effective method of metal 3D printing that is well suited to structural engineering applications. Fundamental test data on the mechanical properties of WAAM materials, especially under cyclic loading, are however lacking. To address this, an experimental study into the cyclic behaviour of WAAM steel plates has been undertaken and is reported herein. Following geometric and quasi-static mechanical characterisation, a total of 40 as-built and machined coupons were tested under different cyclic loading protocols. Key results from the tests, including the full hysteresis curves, are presented and discussed. A cyclic constitutive model allowing for a yield plateau and the degradation of elastic modulus is proposed and validated against the test data. It is shown that the examined WAAM steel exhibited cyclic hardening behaviour dependent on the strain amplitude and strain history. The elastic modulus of the WAAM material was found to decrease in the first few cycles and then remain stable with increasing accumulated plastic strain. Good energy dissipation performance was also observed, indicating the potential of WAAM steels for seismic applications. • Forty WAAM coupons were tested under various cyclic loading protocols. • Geometric and quasi-static mechanical properties of specimens were characterised. • Good energy dissipation performance was observed for examined WAAM steel. • A cyclic constitutive model was proposed and calibrated against test results. [ABSTRACT FROM AUTHOR]

The reliable estimation of the cyclic behaviour of steel beam-to-column joints is essential for the safe design of steel structures under seismic loading. The T-stub is an essential component in steel beam-to-column joints. This paper presents the framework and implementation of a decoupled component model for the T-stub under cyclic loading. This decoupled model splits the single hysteretic spring representation of the T-stub into two separate hysteretic springs, one representing the quadrant where tensile forces are present and the other the quadrant with compressive forces. The results indicate that because of the degradation of the response of the T-stub with multiple loading cycles, the equivalence between the single spring model, and the decoupled double spring model is not trivial. Exact equivalence rules are proposed for the definition of the properties of the decoupled model. The accuracy of the model is validated by comparison with experimental test results. The decoupled model overcomes the problem of using a single spring to represent the T-stub in a steel joint that is not able to lead to correct results because it is unable to mobilize compressive forces in the T-stub as it occurs. • Development of a decoupled component model for T-stub under cyclic loading. • Demonstration of the error of using a coupled T-stub model. • The shape of the hysteretic curve is analysed qualitatively. • Decoupling the tension-compression cyclic behaviour is feasible. [ABSTRACT FROM AUTHOR]

This paper presents the experimental and numerical investigations on the seismic behaviour of steel-jacket retrofitted reinforced concrete (SJRRC) columns with recycled aggregate concrete (RAC). An unstrengthened reinforced concrete (RC) column and nine SJRRC columns tested under lateral cyclic loading are reported. The experimental results manifest that by using the steel-jacket retrofitting approach with RAC, the initial stiffness, ultimate strength, deformation ductility and energy dissipation ability of the columns are improved significantly. The peak strengths of the SJRRC columns are about 1.86–3.44 times of the counterpart of the original RC column. The retrofitted columns also show ductile post-peak load behaviour with the ductility coefficients ranging between 4.05 and 7.93. As the applied axial compressive loads increase, the failure mode of the SJRRC specimens is transited gradually from tension-controlled failure to compression-controlled failure. The specimens failed in compression-controlled mode exhibit plumper hysteresis curves, better energy dissipation ability, and higher secant stiffness than those failed in tension-controlled mode. The specimen having 100% recycled coarse aggregate replacement ratio has slightly lower lateral strength and secant stiffness than the specimens with 0% or 50% recycled coarse aggregate replacement ratio, and shows more serious pinching effect on its hysteresis curve. The effects of the preload and pre-damage of original column could be unfavourable on the cyclic performance of retrofitted column. The finite element analyses are also performed to further investigate the lateral behaviour of SJRRC columns. The proposed finite element model is validated by a comparison with the experimental results. By using the developed finite element model, parameter studies are undertaken and indicate that the applied axial compressive load and the thickness of steel jacket are the dominant factors affecting the lateral performance of SJRRC column. [ABSTRACT FROM AUTHOR]

The P91 steel is widely used in high temperature components of power plants, and it is a candidate material for Gen-IV reactors. The P91 steel has relatively attractive mechanical and physical properties combined with resistance to stress corrosion cracking in water–steam environments. This study aimed to explore the combined cyclic, creep and relaxation behaviour of P91 material. Uniaxial specimens were subjected to cyclic loadings with periodic forward creep or relaxation at peak stress. The results indicate that prior creep or intermediate relaxation periods up to 72 h will influence the subsequent cyclic softening of P91, but do not significantly reduce the cyclic life. In contrast, prior cycling has a detrimental effect on the subsequent creep life. A simplified creep-fatigue model is shown to predict life better than usual code-based approaches. Improved verification of all models would benefit from the availability of more extensive long-term data on P91 steel. [ABSTRACT FROM AUTHOR]

This research aims to investigate the cyclic behaviour of composite joints consisting of concrete-filled steel tubular (CFST) columns, steel beams, and through-bolt connections. A total of 10 specimens, including 5 specimens with square CFST columns and 5 specimens with circular CFST columns, were tested under lateral cyclic loading with horizontal displacements imposed at the top of the column. The main experimental parameters were the cross-sectional type of the column, the axial load level in the column and the cross-sectional configuration of the beam. The experimental results are analysed in this paper to evaluate the performance of the through-bolt connections. Based on numerical analysis, the performance of the bolted joint is further compared with that of the counterpart with external diaphragm. In general, the initial stiffness of the bolted end-plate CFST connections investigated is greater than 8 EI b / L b , so a fixed connection can be assumed in modelling non-sway frames. However, the connection rotation in unbraced frames may need to be considered to minimise the modelling error since the initial connection stiffness is usually smaller than 25 EI b / L b . [ABSTRACT FROM AUTHOR]

This paper addresses the characterization of the behaviour of the column web panel components in bolted end-plate steel joints subject to cyclic loading. Based on experimental test results, a calibrated parametric FE model of a double extended beam-to-column end-plate steel joint is implemented, that allows characterizing the behaviour of the joints both globally and in terms of the dissipative components. The numerical models have been developed using the ABAQUS FE package considering a detailed representation of the various joints components and taking into account the different sources of geometrical and material nonlinearities. Finally, based on the integration of the stress and displacement fields in predefined paths along the column web, a detailed extraction procedure for the cyclic force-deformation behaviour of the column web panel components is proposed, however extensible to other components. These relationships are needed for implementation in a components based approach that accounts for cyclic loading conditions. [ABSTRACT FROM AUTHOR]

The possibility of using high performance fiber reinforced concrete (HPFRC) jacketing for strengthening and repairing sound or corroded column, was experimentally investigated by some of the authors in previous studies. Once assessed the feasibility and the effectiveness of this technique, in the present paper, a numerical three-dimensional model is developed, with the FEM software Diana, in order to simulate the cyclic behaviour of RC columns reinforced with the HPFRC jacket. All phenomena governing the structural response are suitably simulated, and the effect of the external jacket on the local and global behaviour is highlighted and discussed. Finally, two case studies available in literature, related to both cases of sound and corroded existing columns, are analysed in order to clarify and validate the procedure and to suggest some improvements of the HPFRC jacket technique. [ABSTRACT FROM AUTHOR]

Soils in the field conditions, such as in cut slopes or under embankments, often sustains an initial static shear stress prior to the cyclic loadings. Current knowledge on the undrained cyclic behaviour with the presence of initial shear stress has been mainly built on sands. Experimental studies for loess that contains adequate information in this respect is lacking. To fill this gap, this paper presents results from a series of undrained cyclic triaxial tests on the reconsititued and intact loess samples, subjected to different initial static shear stresses. It was found that the existence of initial static shear stress has a significant impact on the failure modes of loess. Three failure modes were observed in the loess samples, including the flow failure, the cyclic mobility and the plastic strain accumulation, among which the flow failure in the reconsitituted loess sample was more destructive because of its sudden nature. On the basis of the experiments, we propose a chart to facilitate the identification of the failure modes of loess by taking into account the influence of initial stress state and the excess pore water pressure (Δu). Specifically, the changes of Δu in the first two cycles are used to distinguish the flow failure and other failure modes. The proposed metod is further validated using the literature data, showing a satifactory predictive peformance. The outcome of this study provides a guideline that is useful not only for evaluating undrained cyclic behaviour of loess, but also for predicting the failure modes without the need to load samples to failure. • Three failure modes were observed in loess under the cyclic loads. • The existence of initial static shear stress has a significant impact on the failure modes of loess. • A chart method was proposed to facilitate the identification of the failure modes of loess. [ABSTRACT FROM AUTHOR]

The behaviour and modelling of concrete columns confined with FRP composites under monotonic compression has been extensively studied, but far fewer studies of the cyclic behaviour of FRP-confined circular and rectangular columns have been carried out. A reliable model indicating the cyclic stress-strain behaviour of FRP-confined columns is of great importance, especially for seismic retrofits and the design of these columns. In this paper, based on the results from a series of cyclic compressive loading tests on FRP-confined specimens, a unified cyclic stress-strain model is proposed for circular, square and rectangular columns confined with FRP composites. The model contains different parts of the cyclic stress-strain curve, including plastic strain, maximum strain in unloading path and corresponding stress, stress deterioration, effect of loading history, partial unloading and partial reloading. New expressions are also proposed for predicting unloading and reloading paths. The proposed model agrees well with the test results. [ABSTRACT FROM AUTHOR]

This paper presents an experimental investigation on the cyclic behaviour of short steel tubes filled with rubberized concrete (RuC), a composite material that mixes concrete with rubber particles. A brief literature review on the cyclic behaviour of CFST columns, the mechanical properties of RuC and recent research on RuC-filled steel tubes (RuCFSTs) is presented. Then, the tested specimens are characterized, comprising three cross-section shapes (square, rectangular, circular), three steel grades (S235, S275, S355), three concrete mixes (0%, 5%, 15% of rubber particles content) and two axial load levels (10%, 20% of axial plastic load). After that, the loading protocol, test rig and experimental procedure are described in detail. The experimental results are extensively discussed, focusing on the columns’ cyclic strength, failure modes, hysteretic and envelope curves, as well as on the energy-based ductility factors. Finally, conclusions are drawn regarding all these parameters. The most relevant achievement is that a concrete mix with a low content (5%) of rubber particles leads simultaneously to the lowest decrease (5%) in the cyclic strength and the highest increase (52%) in the ductility of RuCFST columns, thus being the most suitable mix to use in seismic areas, where ductility and energy dissipation requirements are mandatory. [ABSTRACT FROM AUTHOR]

The accurate reproduction of the hysteretic behaviour exhibited by soils under cyclic loading is a crucial aspect of dynamic finite element analyses and is typically described using the concept of damping ratio. In this paper, a general algorithm is presented for assessing the damping ratio simulated by any constitutive model based on the registered behaviour in three-dimensional stress–strain space. A cyclic nonlinear elastic model capable of accurately reproducing a wide range of features of soil behaviour, including the variation of damping ratio with deformation level, is chosen to illustrate the capabilities of the proposed algorithm. The constitutive model is described and subsequently employed in two sets of finite element analyses, one involving the dynamic response of a sand deposit subjected to different types of motion and another focussing on the simulation of a footing subjected to cyclic vertical loading. The application of the presented algorithm provides insight into the processes through which energy is dissipated through hysteresis. [ABSTRACT FROM AUTHOR]

This study deals with the performance of the upgrading schemes for the existing gravity load designed (GLD) reinforced concrete (RC) beam–column sub-assemblages using near-surface mounted (NSM) fibre-reinforced polymer (FRP) bars. In this study, exterior beam–column sub-assemblage of a general RC-framed structure has been considered. Numerical investigations of the sub-assemblages have been carried out under cyclic loading using nonlinear finite element analysis. Experimentally validated numerical models have been used for evaluating the performance of various upgrading schemes using NSM bars. Cyclic behaviour of reinforcement, concrete modelling based on fracture energy, bond–slip relations between concrete and steel reinforcement have been incorporated. The study also includes numerical investigation of crack and failure patterns, ultimate load-carrying capacity, strain comparisons and formation of plastic hinges, load–displacement hysteresis, energy dissipation and ductility. Seismic performance in terms of energy dissipation and development of strain in beam bar shows that some of the upgraded schemes are found to be comparable to the seismically designed ductile specimens. The findings of this study would be helpful to the practising and design engineers for developing detailing criteria for newly designed – or strengthening of deficient – reinforced concrete structure. [ABSTRACT FROM AUTHOR]

The seismic damages commonly observed on beam-column joints of old reinforced concrete structures, built with plain bars and without proper detailing, justifies the need to further study the behaviour of this type of structures. The response of these structures when loaded cyclically, as occurs during the earthquakes, is partially controlled by the bond properties between the reinforcing bars and the surrounding concrete. This paper presents the results of an experimental campaign of unidirectional cyclic tests carried out on six full-scale beam-column joints built with plain bars. These joint specimens are representative of existing reinforced concrete structures, that is, built without adequate reinforcement detailing for seismic demands. For comparison, an additional specimen is built with deformed bars and tested. The seven specimens are designed and detailed to allow the investigation of the influence of bond properties, lapping of the longitudinal bars in columns and beams, bent-up bars in the beams, slab contribution and concrete strength. The lateral force-drift relationships, global dissipated energy evolution, contribution of the joint, beams and columns to the global dissipated energy, ductility, equivalent damping, final damage observed, homogenized reinforced concrete damage index, displacement components, curvature evolutions and Eurocode requirements are presented and discussed. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

• The results contribute to enlarge the available data on seismic behaviour of substandard RC exterior beam-column joints. • The behaviour of RC exterior joints built with plain reinforcing bars under cyclic loading is not yet completely understood. • Different reinforcement detailing was adopted to study the influence of surface, lapping and anchorage. • Prescriptions of RC codes regarding joint shear capacity were compared with the experimental results obtained. • The results can be also used to calibrate numerical models of RC exterior joints built with plain reinforcing bars. The seismic behaviour of reinforced concrete structures built with plain reinforcing bars is sometimes conditioned by the slippage between the reinforcing bars and the surrounding concrete in the elements as exterior beam-column joints. The anchorage of the beam reinforcing bars in the core joint with weak concrete confinement, inappropriate reinforcement detailing for seismic loads and poor bond properties are the common reasons for collapse of many structures. This paper presents the results of four unidirectional cyclic tests and two unidirectional monotonic tests carried out on full-scale exterior beam-column joints built with plain and deformed reinforcing bars. These specimens are representative of reinforced concrete structures built without adequate reinforcement detailing for seismic loads. The influence of bond properties, lapping of the longitudinal bars, anchorage of the beam reinforcing bars and loading on the beam-column joints response are investigated. [ABSTRACT FROM AUTHOR]

• Block based micro models for historical masonry in dry and wet conditions are described. • Diagonal compression and lateral cyclic loading are both considered within the analyses. • Key modelling parameters are calibrated and formulated based on testing data. • Parametric assessments are conducted and different failure modes are identified and discussed. • Existing analytical methods are evaluated and modifications are proposed. This study examines the in-plane cyclic response of historic masonry elements using a micro modelling approach that incorporates damage-plasticity and surface-based cohesive-contact interface approaches. The nonlinear procedures adopted are validated against tests on dry and wet panels in diagonal compression and large walls under reverse shear-compression loading. Considering the inherent material variability, the numerical results are shown to correlate well with the test results in terms of stiffness, strength, ductility, overall hysteretic response, and cyclic degradation. Based on the validated models, followed by exploratory sensitivity studies, detailed parametric assessments are carried out. The parameter ranges are selected to cover historical masonry materials, consisting of bricks and mortar, and address both dry and wet conditions. Four typical failure modes, namely, flexural strut crushing, diagonal cracking, flexural toe crushing, and mixed sliding, in an order of increasing ductility, are quantified and discussed. It is shown that wet masonry walls have an average reduction of 16% in terms of stiffness and capacity compared with the dry counterparts. Although the failure modes in dry and wet wall pairs are similar, some cases are identified in which the weaker moisture-affected joint strength results in a shift to a more brittle mode. It is also shown that the ductility of the flexural strut crushing mode, which often governs the failure of historical masonry due to its low strength, is considerably overestimated in existing guidelines. Based on the results of the parametric investigations, analytical models for predicting the inelastic response are evaluated, and suggestions for modifications are proposed. [ABSTRACT FROM AUTHOR]

• Six concrete beam-to-CECFST column joints are tested under lateral cyclic loading. • Effects of column axial load ratio, construction and connection methods are studied. • Experimental results are analysed to study the seismic performance of CIP and PC composite joints. • Shear resistance contributions from each component of composite joints are analysed. • PC specimens with proposed connection details exhibit comparable hysteretic performance. Due to the excellent structural performance of Concrete-encased concrete-filled steel tube (CECFST) columns, they have been applied in real practice for several years. In addition, precast technology can be utilised in the construction of CECFST composite structures to further improve productivity. To investigate the behaviour of precast concrete (PC) and cast-in-place (CIP) beam-to-CECFST column joints, a total of 6 joint specimens, including 4 PC and 2 CIP specimens, were thus experimentally studied under lateral cyclic loading. In this paper, the main studied parameters included connection details, construction methods and existence of column axial load. The ultimate strength, failure mode, crack patterns and hysteretic performance of each specimen were analysed in detail. According to the test results, the performance of CIP and PC joint specimens were discussed in the aspect of energy dissipation, ductility and damping coefficients, strength and rigidity degradations. It was found that the PC specimens exhibited comparable cyclic behaviour to the CIP specimens in regards to the maximum strength, hysteretic performance and failure mode. Moreover, based on the measured shear strains, contributions of joint shear resistance from steel tube, inner and outer concrete were quantitatively investigated. Thereafter, the development of shear stress in the outer concrete was compared with the nominal concrete shear strengths from American and European design provisions. [ABSTRACT FROM AUTHOR]

Abstract: The structural performance and reliability of a new blind-bolting technique is investigated in this study. The new blind-bolt is termed Extended Hollobolt (EHB) and is a modification of the standard Hollobolt. The EHB enhances the tensile resistance and stiffness of the fastener by anchoring it in the concrete infill of a tubular column. This paper reports on an investigation into the cyclic behaviour of end-plate connections to concrete filled tubular (CFT) columns using the EHB. A series of six full-scale connections were tested under quasi-static cyclic loading. The key parameters investigated were amplitude of cyclic loading procedure, bolt grade, tube wall thickness, and concrete grade. The strength, stiffness, rotation capacity and energy dissipation capacity of the connections were evaluated at different load cycles. The EHB provided stable hysteretic behaviour with appropriate level of strength and stiffness, where strength is comparable to that of standard bolt-and-nut fasteners and where rigid behaviour can be achieved. The influence of tube wall thickness and concrete grade on the performance of the connection in terms of strength, stiffness, ductility and failure mode is investigated. It is shown that the required performance can be achieved by controlling the tube wall thickness and concrete strength. The results indicate that the connection can offer energy dissipation capacity and ductility appropriate for its potential use in seismic design. [Copyright &y& Elsevier]

Braced frame construction is advantageous in reducing earthquake-induced displacements, but is susceptible to loss of ductility, attributed to brace behaviour. A three-dimensional, nonlinear, elastoplastic finite element model has been developed to simulate the hysteresis behaviour of bracing members subject to reversed axial displacements. The model was able to simulate the hysteresis behaviour of previously tested bracing members in terms of the peak loads and displacements, energy dissipation, and the degradation of both strength and stiffness. The finite element model was refined to include a damage accumulation model for low cycle fatigue and was then used to simulate a second series of experimental tests. The model provided new insight for analysis of the load-displacement hysteresis curves. New fracture life and energy life equations are thus proposed, based on a better understanding of the important parameters influencing brace behaviour. [ABSTRACT FROM AUTHOR]

• UHPFRC is eligible to enhance the performance of shear deficient RC shear walls. • Results indicated that a significant contribution of UHPFRC to the strength, ductility, and stiffness of the original wall. • Roughness and using steel shear connectors at the interface are crucial parameters. • A numerical study was carried out to provide a deeper understanding of the interfacial degradation. • A governing equation was derived to predict the shear strength capacity of UHPFRC strengthened walls. This paper presents an experimental and numerical investigation on the significant effect of the bond properties between Ultra-high performance fiber reinforced concrete (UHPFRC) layers and normal strength concrete (NSC) on the performance of strengthened composite squat shear walls through shear cyclic tests. Moreover, governing equation was derived to predict the shear strength capacity of UHPFRC strengthened walls considering tensile strength of UHPFRC, thickness of UHPFRC layers, surface roughness degree, ratio of steel shear connectors and its yield strength, concrete strength and thickness of original RC wall, and the axial normal force. A series of numerical analyses had been carried out, so proving the capabilities of the proposed formulation. The results indicated that the concrete substrate surface roughness, use of shear connectors, and UHPFRC layers thickness significantly affect the shear bond behaviour between UHPFRC layers and concrete. Installation of shear connectors at UHPFRC-concrete interfaces could significantly improve the post-peak shear behaviour as well as altered the failure mode from brittle due to debonding to ductile. The layer's thickness had a high influence on the shear behavior of specimens with properly roughened surfaces. [ABSTRACT FROM AUTHOR]

Although direct tension tests (DTT) on steel fibre reinforced concrete (SFRC) are difficult to perform, they are of interest because of the uniform tensile stress distribution. Therefore, this paper reports on 31 DTT under monotonic or progressive cyclic loading. All test specimens are notched and continuously monitored with acoustic emission (AE) sensors and clip gauges. The aim is a better understanding of the (cyclic) uniaxial tensile behaviour of SFRC by AE-based damage monitoring. The research shows the importance of fibre distribution and orientation on the load–displacement behaviour. Micro-cracking is detected in the loading cycle prior to fracture by means of AE analysis. Failure mode analysis of the AE signals shows more than 99% mode I damage and indicates the onset of macro-cracking. Localisation of AE events validates the fibre position, the damage stages and the main crack position. Based on AE analyses, differences in damage development are identified even when the post-peak behaviour of the DTT specimens is similar. As such, the obtained experimental data set has an added value to the limited existing research of AE monitoring during DTT on SFRC. • Uniaxial cyclic SFRC behaviour is studied by direct tension tests with AE monitoring. • Fibre amount in the crack plane is estimated and validated with DTT results. • Fibre distribution is analysed through combining fibre counting, clip gauges and AE. • AF/RA-analysis and AE activity distinguish between micro- and macro-cracking. • AE source localisation validates the different stages of damage development. [ABSTRACT FROM AUTHOR]

A novel metallic damper with torsional-yielding on the circular steel tube, called torsional steel-tube damper (TSTD), is proposed in this paper. Four specimens are designed for testing under cyclic loading to investigate their cyclic behaviour. The torsional-yielding mechanism contributes to the uniform yielding at the tube wall, results in an outstanding hysteretic performance and a high equivalent viscous damping ratio of about 0.5. Then the finite element analysis method is used for simulating the tested specimens, and the stress, strain, and parametric influence of the damper model are analyzed. Furthermore, a modified Bouc-Wen model is proposed to describe the cyclic behaviour of the tested specimens. The particle swarm optimization algorithm is used for identifying the model parameters. The identification results indicate that the modified Bouc-Wen model can accurately predict the hysteretic behaviour of the proposed damper. Finally, the proposed damper is implemented in a reinforced concrete frame model, and the nonlinear dynamic analysis method is adopted to assess the feasibility of the damper. [Display omitted] • A metallic damper with torsional-yield mechanism is proposed. • The cyclic behaviour of the damper is investigated by a laboratory test. • Finite element analysis method is used to further assess the damper. • The cyclic behaviour of the damper is described by the Bouc-Wen model. [ABSTRACT FROM AUTHOR]

In this paper a methodology for studying the mechanical behaviour of complex structures made of GFRP structural members joined by means of adhesive connections and subject to variable intensity loads is presented. The fundamental equations are derived by an asymptotic approach applied on composite structures made of two elastic solids bonded together by a third thin one represented by a thin layer with a nonlinear behaviour. The adhesive layers are considered micro cracked according to the Kachanov's assumptions. Within this framework, to calibrate the parameters of the imperfect interface model, the mechanical properties and damage evolution of an epoxy adhesive have been experimentally evaluated under cyclic loadings. The experimental tests have been performed on aluminium cylinders considering different thicknesses of adhesive. The experimental results evidence how the adhesive thickness influences the strength, stiffness and consequently the initial damage parameter (initial cracks) of the bonded connections. Finally, the robustness and accuracy of the imperfect interface model is demonstrated by the excellent comparison with experimental results of a GFRP hollow column to built-up beam adhesive connection, under static, cyclic and fatigue loads using a description of damage evolution. [ABSTRACT FROM AUTHOR]

• A new cohesive law for cyclic mixed-mode crack propagation is proposed. • Experimental tests on FRP-concrete and steel interfaces are used for validation. • A good comparison with experimental data is shown. This paper presents a new cohesive law for modelling interfaces under mixed-mode cyclic loading. The formulation is based on the definition of a free energy function which governs the interface behaviour under monotonic loading, which is then extended to cyclic-driven decohesion through the introduction of a scalar damage variable, whose evolution in time is governed by a phenomenological rate equation. The cohesive model is formulated for a mixed-mode problem and then it is applied for the simulation of debonding phenomena occurring at the interface under a pure a shear stress state. Experimental results available in literature, related to single-lap shear tests, performed on both concrete and steel specimens reinforced by fibre reinforced composite (FRP), are used to validate the proposed model and to show its effectiveness to simulate very closely the observed experimental behaviour. [ABSTRACT FROM AUTHOR]

As the importance of safe and economical foundation design of offshore wind turbines has increased, suction bucket foundations have become increasingly common. A tripod suction bucket foundation consists of three individual buckets arranged in a triangular shape. The cyclic behaviour and soil-foundation-structure interaction of single suction bucket foundations has been a subject of active research. However, it is difficult to predict the behaviour of tripod bucket foundation because it is structurally complex and requires consideration of cyclic load effects. This study focuses on the behaviour of tripod suction foundations under cyclic loading. The rotational stiffness of the tripod foundation is estimated by combining equations depending on compression, pullout, and rotational stiffness of the single suction bucket with a series of centrifuge model test results. By presenting the theoretical stiffness values, it is verified that the rotational stiffness can be estimated only based on the cross-section of the foundation and the shear modulus of the soil. In addition, it is possible to predict the long-term rotational stiffness of the tripod by applying the vertical stiffness obtained from the cyclic loading test of the single bucket to the simplified method. [ABSTRACT FROM AUTHOR]

• A new kind of structural system, UHPC columns with hybrid reinforcement, is proposed; • Quasi-static tests of four UHPC columns with hybrid reinforcement are conducted; • Influences of CFRP bars and axial-load ratio on the UHPC columns are analyzed; • The design axial-load ratio limit of the hybrid UHPC columns is proposed; • A proper replacement ratio of CFRP bars was suggested for the hybrid UHPC columns. A new type of reinforced concrete column with ultra-high-performance concrete (UHPC) and hybrid carbon fibre-reinforced polymer (CFRP) and steel bars is proposed in this paper. The CFRP bars with an excellent linear elastic property are used in the columns to enable the expected self-centring capacity. Steel bars with good plastic properties and high ductility UHPC were used to maintain the high energy-dissipation capacity of the columns. Four UHPC columns were tested under reversed cyclic lateral loading; the behaviour of the UHPC columns with hybrid CFRP/steel reinforcement bars was analysed numerically using OpenSees, and the influences of the CFRP bars and axial-load ratio on the seismic behaviour of the columns were analysed. The results indicate that the strain in the longitudinal bars at the ultimate state is a crucial criterion for determining the effectiveness of the CFRP bars. The UHPC columns with the hybrid CFRP/steel reinforcement exhibit both excellent self-centring capacity and good energy dissipation when the design axial-load ratio is less than 0.7. The replacement ratio of the CFRP bars is suggested to be 1/3–2/3 so that the self-centring and energy-dissipation capacity of the UHPC columns with hybrid CFRP/steel reinforcement bars can be balanced. [ABSTRACT FROM AUTHOR]

This paper presents the results of an extensive experimental investigation on the behaviour of a new type of joint between open structural steel beam and rectangular hollow section (RHS) column. The proposed joint is demountable: threaded studs are welded to the front face of the hollow section column and angle cleat legs are then bolted to the column by means of the welded studs and to the beam flanges by ordinary bolts. Twenty-one full-scale single side or double side bolted beam-column joints combining different sections have been tested under monotonic and cyclic loads. The test results confirm that these joints behave as semi rigid and partial strength ones which possess sufficient stiffness and moment resistance for use in the construction of low to medium-rise steel buildings as an alternative to other traditional solutions. The proposed joints also exhibit a moderate energy dissipation capacity under cyclic loads, suitable for construction in moderate seismic regions. This research work demonstrates that the proposed joint is easy to execute on site without specialized manpower or expensive facilities. • New joints are proposed that are cheap, easy to execute, and may be reused contributing to sustainable construction. • These new joints behave as semi-rigid in the frame analysis. • Monotonic and cyclic tests have been carried out on a set of joints to determine their static and dynamic behaviour. • Material properties of welded studs have been obtained. [ABSTRACT FROM AUTHOR]

Numerical simulations of pile installation in sands require advanced constitutive models which are able to predict the mechanical behaviour of soils in a wide range of soil stresses under different loading conditions such as cyclic and monotonic loadings. In this paper, an elasto-plastic constitutive model within a double hardening framework is described which is capable of reproducing the mechanical behaviour of sands in different soil states (stress and relative density) under deviatoric and volumetric loadings. First, the formulation of the model is described and then the capability of the model is shown by simulating laboratory tests data of Karlsruhe sand for various relative densities, stress states and loading conditions. [ABSTRACT FROM AUTHOR]

• The stress-controlled drained simple shear tests, with 5000 cycles on Fontainebleau sand are carried out and presented. • The initial void ratio, normal stress, cyclic shear stress ratio and average shear stress ratio significantly affect the accumulation of volumetric strain. • The analytical model of volumetric strain accumulation is developed considering the different initial conditions. Volumetric strain of a soil element surrounding the pile accumulated under the drained cyclic loading condition is one of major concerns in geotechnical engineering design. In this paper, twenty stress-controlled drained simple shear tests, with 5000 cycles on Fontainebleau sand have been carried out, which aims to investigate four factors influencing cyclic accumulation behaviour: initial void ratio, normal stress, cyclic shear stress ratio and average shear stress ratio. Based on results, the cyclic volumetric strain accumulation for each influencing factor is summarized, which is found highly sensitive to the cyclic shear stress ratio that a bigger magnitude (more than 0.2) leads to a larger degree of densification. In addition, a simple analytical model is then proposed accounting for these factors with seven parameters that can be directly calibrated from laboratory tests. Finally, the applicability of the model is examined by simulating the additional tests through an adoption of the parameters calibrated by the training tests. [ABSTRACT FROM AUTHOR]

In order to study the constitutive relation of stainless-clad (SC) bimetallic steel under earthquake actions, tests of 23 specimens prepared from 316L+Q235B SC bimetallic steel plate with a nominal thickness of 3 + 5 mm are carried out, in which tensile and compressive monotonic loadings as well as 15 different cyclic loading spectrums are incorporated. Based on the test results, monotonic and hysteretic behaviour, macro- and micro-failure characteristics are analysed. Through comparison and analyses, it is indicated that the envelope curves of the SC bimetallic steel under cyclic loadings are markedly higher than the monotonic tensile curves, which demonstrates that the cyclic hardening effect is significant. Both isotropic and kinematic hardening characteristics are observed, i.e. the cyclic behaviour of the SC bimetallic steel exhibits a typical combined hardening effect. In addition, it is found that envelope curves of the SC bimetallic steel may be described well by using the Ramberg-Osgood (R-O) three-parameter model, of which the parameters are updated though nonlinear fitting of the test data. To develop a constitutive model for simulating the cyclic behaviour of the SC bimetallic steel, the Chaboche plastic constitutive model is employed herein, and its relevant parameters are updated and calibrated. By using the adapted Chaboche model in finite element (FE) analyse through ABAQUS, the cyclic behaviour of all the test specimens are simulated. It is found that the simulated curves obtained from the FE model results agree well with the test curves, which demonstrates that the constitutive model proposed herein is adequate for evaluating the cyclic responses of the SC bimetallic steel. The research outcomes may provide an important basis for accurate analyses of structures fabricated from the SC bimetallic steel under earthquake actions. • 23 cyclic tests on stainless-clad bimetallic steel were conducted. • Combined cyclic hardening effects including isotropic and kinematic ones were seen. • The R-O three parameter model may well describe the cyclic envelop curves. • The adapted Chaboche model is capable of simulating the cyclic behaviour. [ABSTRACT FROM AUTHOR]

With the rapid development of high-speed railways (HSRs) in seasonally frozen regions in China in recent years, there is an increasing need for better understanding of how the construction materials behave. In particular, the dynamic behaviours of coarse-grained materials (CGMs) used for China's HSRs subjected to combined actions of cyclic loading and freeze-thaw (F-T) cycles has attracted much attention. In this study, a series of cyclic triaxial tests were performed to investigate the characteristics of CGMs considering the effects of number of F-T cycles (N FT), confining pressures (σ 3), dynamic stress amplitude (σ ¯ d), and fines content (FC). Representative test results of accumulative axial strain (ε acc), resilient modulus (M r), dynamic shear modulus (G d) and damping ratio (D) are then presented and discussed. Empirical models are proposed and validated for predicting the evolution of ε acc and M r for CGMs under the cyclic loading. In addition, the evolution models of G d and D were established, which can be used for computing the response of CGMs under various influencing factors. Overall, this study provides further insights into the cyclic behaviours of CGMs in seasonally frozen regions. • Cyclic triaxial tests were carried out on prepared thawed coarse-grained materials. • Effects of freeze-thaw cycles, confining pressure, dynamic stress amplitude, and fines content were discussed. • Models for accumulative strain, resilient modulus, dynamic shear modulus and damping ratio were proposed and validated. [ABSTRACT FROM AUTHOR]

Bainitic steels play an important role in the modern automotive and rail industries because of their balanced properties. Understanding the relationship between the bainitic microstructure features and the fatigue performance is a fundamental ingredient in developing safer and durable products. However, so far this relationship is not sufficiently clear. Therefore, there is the need to strengthen the knowledge within this field. The present paper aims at comparing the uniaxial cyclic behaviour of carbide-bearing and carbide-free bainitic steels. To meet this goal, fully-reversed strain-controlled tests at various strain amplitudes were performed. After the final failure, fracture surfaces were observed by transmission electron microscopy to relate the bainitic morphology to the fatigue performance. The main findings of this work show that the carbide-free lower bainite has superior fatigue performance compared to the carbide-bearing lower bainite. This is explained by the presence of stable carbides and thick bainite ferrite plates. [ABSTRACT FROM AUTHOR]