Search

Planetary Threaded Roller Bearing (PTRB) is a new bearing suitable for the heavy load linear drive mechanism. The load is transferred internally through annular threads, affecting the bearing capacity of the thread's contact load distribution characteristics. The structure of PTRB is discretized to study the contact load distribution of PTRB. The axial stiffness of the thread's teeth, its axial stiffness, and the contact stiffness of contact points are calculated. Moreover, a 1D equivalent spring network model is proposed based on discretized structure and stiffness. The PTRB contact load calculation model is proposed using the direct stiffness method and a 1D equivalent spring network model. Finally, the accuracy of the model proposed in this paper for calculating the contact load distribution of threaded teeth is verified by comparing the results obtained from theoretical model calculations, finite element methods, and experiments. The theoretical model proposed in this paper can provide theoretical guidance for PTRB parameters. [ABSTRACT FROM AUTHOR]

Steel constructions made of circular hollow sections are commonly joined by welding or ring‐flange bolting. An additional, novel joining method is the so‐called hybrid grouted joint. The hybrid grouted joint is characterised by its multi‐layered composition. In contrast to state‐of‐the‐art grouted joints, hybrid grouted joints include thin adhesive layers, which are applied on the steel surfaces prior to grouting. Sand grains are embedded in the yet uncured adhesive. After the curing of the adhesive, the surface has a high degree of roughness. This allows a high‐performance interlock between fine grain grout and the adhesively bonded sand granules across the contact surfaces in the overlap area. The ability to transfer loads across a wide area with low stress concentrations makes the hybrid grouted joint a promising joint alternative especially regarding the fatigue performance. This paper summarises the main findings concerning fatigue behaviour of the hybrid grouted joint under axial loading. Wöhler diagrams were determined in numerous fatigue tests for two combinations of adhesive and grout. [ABSTRACT FROM AUTHOR]

In the context of tall building design, the tube concept represents one of the most performing systems. The diagrid is the widespread type of tube system and consists of a diagonal grid of beams that wraps the building, forming a diamond pattern. It performs as lateral bracing and is additionally able to sustain vertical loading through axial forces. Despite its efficiency, a growing interest is recently observed in alternative geometries to replace the diagrid pattern and improve the architectural impact conferred by the building skin aesthetics on the urban environment. The paper pursues the use of a Voronoi mesh, in which the geometry of the cells is steered to known schemes for the structural design of a cantilever tube structure. The objective is to mimic a macroscopic structural behavior through a topology and size modification of the Voronoi mesh that increases the density for creating resisting paths with higher stiffness. The paper proposes a novel method Vorogrid for designing a new class of tall buildings equipped with an organic‐looking and mechanically sound tube structure, which makes them a valuable alternative to competitors (diagrid, hexagrid, random Voronoi). Diagrids and hexagrids still remain more efficient in terms of forces and displacements but are characterized by a more usual appearance, instead Vorogrid offers more design control and better performances on average with respect to random Voronoi structures. This method is streamed into a pipeline that includes grid initialization strategies, geometric and structural optimization to mitigate the effects of the grid randomness, and structural sizing. [ABSTRACT FROM AUTHOR]

This paper investigates the cyclic behavior of steel columns subjected to single‐sided cyclic loading protocols driven by residual deformations. First, nonlinear time‐history analyses are performed to steel framed structures using a set of repeated earthquakes. Then, based on the dynamic analysis results, a set of single‐sided loading protocols is developed to envelop the asymmetric seismic behavior of the examined frames. The developed protocols are used to identify the new single‐sided capacity margins of steel columns in terms of strength and ductility as well as evaluate the potential of using novel high‐strength materials. In this paper: (a) the new asymmetric loading protocols are proposed based on the seismic behavior of three medium‐rise frame buildings with different beam‐to‐column strength ratios (i.e. Mpc/Mpb) which are analyzed with the aid of the finite element analysis (FEA) software ABAQUS; (b) a computational databank of the inelastic responses of square tubular steel columns with high yield‐to‐tensile (YT) strength ratio is developed by subjecting column FEA models with various width‐to‐thickness ratio and axial loads to both conventional and asymmetric cyclic loading protocols. Due to the asymmetrical nature of the cyclic protocols, a lower post‐peak strength deterioration was observed in columns that enables the definition of new, extended, ductility capacity margins. The ductility capacity ratios under the asymmetric loading protocols were found to be 1.15 to 1.71 higher than those obtained under the conventional protocols enabling the use of high‐strength steels in steel columns of smaller width‐to‐thickness ratio. [ABSTRACT FROM AUTHOR]

This paper introduces a novel method to spontaneously predict displacement time histories and hysteresis curves of bridge lead rubber bearings under seismic loads and axial forces. The method leverages a stacked convolutional‐bidirectional Cuda Long Short Term Memory network, enhanced with multi‐head attention, skip connections, exponential learning rate scheduler, and a hybrid activation function to improve performance. The framework utilizes the functional application programming interface provided by the Python Keras library to build a model that takes input features such as horizontal and vertical ground accelerations, actuator loads in both lateral and vertical directions, and the superstructure mass. The effectiveness of the deep learning model is evaluated using a considerable experimental dataset of 53 real‐time hybrid simulations, spanning various earthquake intensities and superstructure masses (Chi‐Chi: 15 scenarios, El Centro: 15 scenarios, Kobe: 13 scenarios, and Northridge: 10 scenarios). Initially, Northridge earthquake data serves as unseen data, while the rest is used for training and validation. In a subsequent trial, the unseen data is centered on Kobe earthquake scenarios. By employing a hybrid loss function merging mean square and mean absolute errors, the model exhibits a substantial correlation of over 83% between predicted displacement time series and empirical measurements for the unseen data. In summary, the proposed model offers miscellaneous benefits, including time and cost savings in experimental efforts by decreasing the need for additional tests. It further delivers a swift and precise insight into the bridge bearing performance and its energy dissipation, facilitating timely and accurate bridge design in different scenarios for engineers. [ABSTRACT FROM AUTHOR]

ABSTRACT This paper evaluates the capability of the theory of critical distances (TCD) coupled with the Fatemi–Socie (FS), Smith–Watson–Topper (SWT), and normal stress range (S‐N) criteria for the lifetime estimation of combined fretting fatigue, that is, the combination of bending and axial loading modes, for 316L stainless steel along with the effect of increasing the grain size of the material. After evaluating the stress field, the point, line, area, and volume methods have been implemented to estimate the lifetimes of fretting fatigue experiments based on the dependency of the critical distance on the number of cycles to failure. Whereas the area and volume methods were overestimating the lifetimes, the point and line methods were more accurate. FS and SWT criteria were proper in lifetime estimation, but the normal stress range (S‐N) criterion was not a safe criterion. At the same time, increasing the grain size of the material leads the TCD to be more conservative. [ABSTRACT FROM AUTHOR]

This paper presents the design and numerical optimization of oil‐lubricated spiral grooved thrust bearing (SGTB) for its application at high speed and axial loading conditions. A numerical model is developed using nonlinear incompressible Reynold's equation and is solved using the finite volume method (FVM) to determine the static characteristics over the bearing surface. Further, the influence of groove parameters such as spiral angle, groove angle, film thickness ratio, number of grooves and speed on the static characteristics of the bearing has been investigated. The result shows that the designed oil‐lubricated SGTB can operate at high‐speed conditions and withstand high axial load. Further, the characteristic data sets acquired from the numerical analysis are trained using an artificial neural network (ANN), and their performance is evaluated through the computation of the regression coefficient. Then adaptive neuro‐fuzzy interface system (ANFIS) surface plot is obtained to determine the optimum bearing parameters. [ABSTRACT FROM AUTHOR]

This paper presents a hybrid simulation (HS) with a proposed substructuring technique that captures the effect of first‐story column local buckling and axial shortening on the frame behavior. The HS is applied to examine the seismic response of a two‐dimensional seven‐story, two‐bay steel dual system. The experimental substructure consists of a full‐scale interior column and beam cruciform subassemblage, including a moderately ductile first‐story built‐up box column and two I‐shaped beams. Under combined axial and lateral loads, local buckling can occur near the column base, resulting in column shortening. The specimen is loaded through a four‐degree‐of‐freedom (DOF) mixed‐mode control (three displacement‐ and one force‐control) actuation system that simplifies the actual complex boundary conditions of the frame structure. To account for column shortening in the HS, a new approach consisting of a set of fictitious equivalent forces applied to columns in the numerical model to achieve compatible displacements with the experiment is implemented. Shortening of the two exterior columns in the model is simulated through finite element analysis using the computer program ABAQUS in an attempt to capture the redistribution of axial loads with column shortening. The test results confirm that the proposed modeling and control methods successfully integrate the experimental substructure and ABAQUS simulation into the HS, resulting in a more realistic frame response that captures the effect of column shortening in the analysis. The moderately ductile built‐up box column is verified to perform well in near‐fault earthquake loadings. [ABSTRACT FROM AUTHOR]

Previous studies have underlined the importance of establishing a database of high‐fidelity benchmark experimental test results under random loading histories such as earthquake excitations for both existing structural systems as well as newly proposed ones. Such experimental results are useful for understanding the limitations of previously developed numerical models, proposing new numerical models for more recently developed structural systems, better assessing the ultra‐low cycle fatigue (ULCF) life of energy dissipative components, and improving the loading protocols used for element assessments or developments of numerical model. This paper presents experimental results from pseudo‐dynamic hybrid simulations on steel eccentrically braced frames (EBF) equipped with novel cast steel replaceable modular yielding links. The first set of experiments are carried out on a four‐story EBF, with the first‐floor yielding link physically tested in the laboratory. The second set of experiments are performed on a two‐story EBF where the second‐floor link is physically tested in the laboratory, while considering axial loads due to the imbalanced distribution of the seismic weight in the building. Each building structure is subjected to three Maximum Credible Event (MCE) level earthquakes. A framework for performing hybrid simulations on EBFs is proposed where the response of the yielding link is physically captured in a single degree of freedom control system, with or without axial loads. A substructuring strategy is proposed in conjunction with a modeling approach in the integration module. The results confirm the effectiveness of the hybrid simulation framework, which can be adopted in similar studies. Two numerical models are proposed for capturing the response of cast steel links using a simplified and a more advanced approach. The models are first calibrated using incremental reversed‐cyclic experimental test results, and then refined using the hybrid simulation test results. The effects of this calibration improvement are quantified through critically comparing the response prediction for different response parameters before and after improving the calibration with the experimental results. The numerical model which captures the physical mechanism of the cast steel links provides a more accurate response prediction compared to the simplified numerical model using a phenomenological truss with calibrated force‐deformation. The remaining ULCF life of the tested yielding links is experimentally investigated after having sustained three MCE level earthquakes, which indicates a large reserve ductility capacity which is more than twice the required plastic rotation capacity for cast steel links after seismic events. [ABSTRACT FROM AUTHOR]

This paper presents numerical simulations on the behavior of thin‐walled steel tubular bridge piers of box sections under cyclic lateral loading in the presence of constant axial compression loads, using three‐dimensional finite element analysis adopted in commercial computer software ABAQUS. The analysis and experimental results are compared to show how the adopted material models, such as elastic perfectly plastic (EPP), kinematic hardening (KH), and isotropic hardening (ISO) material models are effective and reliable for capacity prediction and cyclic behavior evaluation. The effects of cyclic lateral loading on the hysteresis behavior of the thin‐walled steel tubular bridge piers of box sections have been evaluated by analyzing the hysteresis curve, envelope curve, stiffness, and strength degradation characteristics, considering the interaction of local buckling and flexural buckling. In contrast to the ISO and EPP material models, the analysis results compare reasonably well with test results using the KH material model. [ABSTRACT FROM AUTHOR]

This paper describes experiments addressing the buckling and collapse behaviour of cold‐formed stainless steel cruciform section columns. To build doubly symmetrical flanged cruciform section columns, six individual press‐braked plain channels made of austenitic grade EN 1.4307 were assembled back‐to‐back. Two channel geometries were used – with cross‐section height 200 mm and 100 mm. They were connected using bolts M8 of class 8.8, with equidistant spacings along the column length. Six columns with three different lengths – namely, short (600 mm), intermediate (1200 mm) and long (2400 mm) – were tested under pure axial compression load and under end semi‐rigid support conditions. Two tests were included for each length. It was observed that the buckling patterns in the built‐up cruciform section specimens were affected by their global slenderness and by the spacing between the fasteners. However, in the cases of long specimens, where global torsional buckling was critical, the fastener spacing had a minor influence on the ultimate capacity of the columns. [ABSTRACT FROM AUTHOR]

Complex circular hollow section double KK‐joints are widely used in, e.g. offshore wind turbine jackets. As an alternative to conventional welded joints of the CHS multi‐membered structures, wrapped composite joints have shown superior structural performance in previous pilot tests. Experimentally characterizing the joint behaviour under uniplanar loading can be complicated, because of the ductile failure mechanisms of wrapped composite joints and second‐order bending moments. This paper presents the design of a test frame in combination with a conventional tensile 2.5 MN test rig. Ductile joint failure, joint imperfections and second‐order effects are considered in the design. Structural finite element software SOFiSTiK is used to analyse the effects of wrapped joint behaviour and imperfections on the test system and interaction of joint, frame and loading rig behaviours. Non‐linear joint behaviour and misalignments of the braces increased the second‐order effects significantly. Mitigation strategies have been explored to reduce additional bending moments in the KK‐joint. A complete test setup is proposed to perform static experiments on double KK‐joints in uniplanar axial loading conditions. [ABSTRACT FROM AUTHOR]

This paper focuses on discussions about establishing the design resistance of hollow section joints, which have now been ongoing for 30 years. The question arose once physical experiments could be replaced by numerical tests and was temporarily solved by agreement on a displacement limit within the IIW. With the advent of design using finite element (FE) solutions and the use of high‐strength steels, this question is being raised once more. Many design guides and standards with considerable international consensus are now available for the design of welded hollow section joints in onshore and offshore construction. However, they typically cover relatively standardized joint types, geometries and loading cases. In the event of unusual joints it is now common for finite element modelling to be performed, but specific guidance needs to be provided on acceptable FE modelling procedures and the interpretation of the output in order to determine a suitable joint design resistance. With this objective in mind, this paper describes appropriate FE modelling and ultimate limit states that can be used; in particular, a 5 % ultimate strain limit state. Application of these ultimate limit states is demonstrated using validated FE models for RHS‐to‐RHS (rectangular hollow section) X‐joints, with braces in axial compression and tension, and brace plate‐to‐CHS (circular hollow section) joints with braces loaded in axial compression. [ABSTRACT FROM AUTHOR]

Highlights This paper presents the effect of varying the type of Z‐pin on the delamination bridging performance of unidirectional composite laminates. Carbon and Kevlar Z‐pins were inserted in thick composite laminates using the pre‐hole insertion Z‐pinning process and their bridging performance characterized across the different mode‐mixity range. The bridging response indicated that Kevlar Z‐pin experienced load reduction driven by interfacial friction (Stage III), which was absent in the Carbon Z‐pin. When Mode II dominated the bridging crack, Kevlar Z‐pin showed partial pullout and fiber shear cracking, while the Carbon Z‐pin exhibited clean transverse fracture. Although the bridging load obtained by the Carbon Z‐pin was twice that of Kevlar Z‐pin, the Kevlar Z‐pin provided a higher interlaminar fracture energy. The superior bridging performance of Kevlar Z‐pin is correlated with the enhanced ductility. Moreover, the resin‐rich area was involved in deformation and provided the extra axial load of Z‐pin. The comparison of mixed‐mode bridging mechanism between Kevlar Z‐pin and Carbon Z‐pin. Reveal the variation of multi‐directional load and energy consumption with mixed‐mode angle in thick laminates. Detailed scanning electron microscope observation to understand failure characteristics of ductile Z‐pin. Evidence that the extra axial load of Z‐pin provided by resin‐rich area. [ABSTRACT FROM AUTHOR]

This article presents high‐fidelity observations of the time evolution of unstable delamination growth in tapered composite beams under tensile loading via ultra‐high‐speed camera in conjunction with digital image correlation. Asymmetrically tapered GFRP laminates, with a thickness drop from 18 plies to 12 plies, are manufactured in three different layup configurations with grouped drop‐offs: [06/(02)3/06], [06/06/06], and [06/(±45)3/06]. Beam specimens are subjected to quasi‐static tensile loading in a servo‐hydraulic axial testing machine, and the damage evolution on one edge of the tapered beam is monitored in situ at 124,000 fps with a high‐speed camera (HSC). In selected tests, digital image correlation (DIC) analyses are conducted either on the edge or on the tapered surface to obtain the full‐field strain and elucidate failure mechanisms. Real‐time HSC observations of the damage sequence consistently affirm that the initial failure mechanism is a transverse crack at the nearest drop‐off to the thin section, which is followed by delaminations at interfaces of sublaminates. Unstable delamination growth is characterized by measurements of lower bounds of crack tip speeds. The unique crack speed data provide evidence for the existing effect of through‐the‐thickness stresses on delamination growth. The detailed sequence and patterns of dynamic failure presented in this paper can serve as a benchmark to validate damage models used in simulations of tapered laminates. Highlights: The sequence of unstable delamination growth in tapered GFRP beams is investigated experimentally.Characterized unstable delamination growth based on crack tip speed measurements.Strain fields are evaluated along beam edges using DIC in real‐time.In‐situ observations of dynamic failure can serve as a benchmark to validate damage models. [ABSTRACT FROM AUTHOR]

In this paper, seven half‐scale specimens are used to investigate the effects of the beam–column width ratio, concrete strength, and axial load on the seismic performance of wide exterior beam–column joints. The test results show that all the specimens undergo bending damage at the beam end. The concrete damage in the core column is not significant, meeting the seismic requirements of strong column–weak beams and strong joint–weak members. For specimens with small beam widths, the increase in axial load can effectively reduce the damage to the concrete in the outer joint and increase the strength of the specimen. Increasing the beam width and concrete strength reduces the ductility of the specimen while increasing the strength of the specimen. The bonding performance of the longitudinal bars anchored outside the core column is poor, as bond–slip with the concrete is observed during the test. In addition, compared with ACI 318‐19, GB 50011‐2010 is more conservative for calculating the shear strength of exterior wide beam–column joints. Finally, a corresponding finite element model is established by MSC Marc and verified based on the experimental results. [ABSTRACT FROM AUTHOR]

This paper investigates the effects of transverse shear walls (TSWs), out‐of‐plane bending stiffness of diaphragms (FDIA), and axial loading (AXL) on the lateral response of strong wood‐frame shear walls (SWs) used for multistory light frame timber buildings (LFTBs) located in highly active seismic zones. Experimental tests were conducted to understand the requirements for SW‐to‐TSW connections to achieve desirable TSW effects in non‐planar SWs and to characterize the lateral cyclic response of T‐shaped SW assemblies with and without diaphragms and axial load. Both slotted and screwed connections were evaluated as SW‐to‐TSW connections, and both showed sufficient stiffness and strength to achieve TSW effects. However, the slotted connection is preferred because it has a more ductile failure mode. Tests on T‐shaped SW assemblies with and without diaphragms and axial load revealed that TSWs significantly enhance the lateral stiffness and strength but reduce the deformation capacity with respect to that of planar SWs. FDIA and AXL effects further influence the stiffness and strength, overcoming the limitation of smaller deformation capacity in T‐shaped SWs without diaphragms. Diaphragms also make the T‐shaped SW response more symmetrical and improve the evolution of the secant stiffness, the cumulative dissipated energy, and the equivalent viscous damping over increasing levels of lateral drift. Numerical analyses of a theoretical building model with T‐shaped SWs show significant reductions in lateral drift (up to 46%) and uplift (up to 100%) compared to the case with planar SWs only, emphasizing the importance of considering system effects in the seismic design of LFTBs. [ABSTRACT FROM AUTHOR]

Structural stability tests on two‐span channel members in bending, axial compression and torsion The use of slender steel members promotes the competitiveness of steel structures in structural engineering. However, these members often necessitate stability verifications. Global research activities in this field have so far mainly focussed on single‐span members with doubly symmetric cross‐sections. For mono‐symmetric sections such as channels, only a few design models exist based on experimental evidence. Moreover, the potential of structural systems such as multi‐span members is yet not entirely exploited in the normative verification models. Therefore, this paper presents a comprehensive experimental study on the stability behaviour of two‐span members with steel channels under combined loading. Five‐point bending tests were conducted to determine the load‐bearing capacities and to experimentally analyse the influence of the constructional detail of the central support, the axial load, the slenderness ratio and other parameters on the load‐bearing behaviour. The article provides the scientific basis for extending the scope of the stability verification for members subjected to bending, axial compression and torsion in Annex C.2 of the novel EN 1993‐1‐1:2022 to two‐span channel members. [ABSTRACT FROM AUTHOR]

This paper investigates the accuracy of the existing empirical design models and different machine learning (ML) models, known as Decision Tree (DT), Random Forest (RF), K‐Nearest Neighbors (KNN), Adaptive Boosting (AdaBoost), Gradient Boosting Regression Tree (GBRT), and Extreme Gradient Boosting (XGBoost) in predicting the ultimate axial load of circular concrete‐filled stainless steel tubular (CFSST) columns under axial loading. A test database encompassing the test results of 142 CFSST columns is used to validate the accuracy of the existing empirical design and different ML models. It was demonstrated that all the ML models can provide a better estimation of the ultimate axial load than the existing empirical design models do, in which XGBoost can provide the best estimation of the ultimate axial load of CFSST columns. Finally, a simple equation is proposed based on the XGBoost model for the practical design of CFSST columns. [ABSTRACT FROM AUTHOR]

This paper presents two experimental campaigns carried out on 36 reinforced concrete (RC) beams (with and without shear reinforcement) subjected to a three‐point bending loading with a shear force on the one hand, an axial compressive load and a negative bending moment applied at each end of the beams on the other hand. Such a loading configuration makes it possible to investigate the influence of both axial compression and negative bending moment on the shear capacity of RC beams. For each campaign, three values of axial compressive force were studied, and the test beams were divided into two series with low and high negative bending moment. During the tests, Digital Image Correlation technique was used to capture the cracking evolution of the specimens. Besides, the experimental shear strengths of the beams are confronted to the predictions of Eurocode 2 in order to assess its practical validity. Finally, a semi‐analytical method proposed by Wahbi et al. 2021 (A failure criterion for RC beams subjected to axial and transverse loadings) for evaluating the resistance domain of RC elements subjected to transverse and axial loads, is extended in this paper to take into account the negative bending moment and compared to the experimental results. [ABSTRACT FROM AUTHOR]

This paper focuses on discussions over establishing the design resistance of hollow section joints, which have now been ongoing for 30 years. The question arose once physical experiments could be replaced by numerical tests and was temporary solved by agreement on a displacement limit within IIW. With the advent of design by finite element (FE) solutions, and the application of high‐strength steels, it is being raised once more. A number of design guides and standards, with considerable international consensus, now exist for the design of welded hollow section joints in onshore and offshore construction. These, however, typically cover relatively standardized joint types, geometries and loading cases. In the event of unusual joints, it is now common for finite element modelling to be performed, but specific guidance needs to be provided on acceptable FE modelling procedures and the interpretation of the output, in order for a suitable joint design resistance to be determined. Towards this objective, this paper describes appropriate FE modelling and ultimate limit states that can be used; in particular, a 5 % ultimate strain limit state. Application of these ultimate limit states is demonstrated using validated FE models for RHS‐to‐RHS (rectangular hollow section) X‐joints and branch plate‐to‐CHS (circular hollow section) joints, with branches loaded in axial compression. [ABSTRACT FROM AUTHOR]

It is a well‐known fact, that hydrodynamically supported systems are prone to nonlinear vibrations. Their exact simulative prediction with respect to frequency and amplitude is complicated by the fact that different system properties interact. The paper at hand outlines an approach that takes all relevant influences like rigid body motions, elastic deformations, nonlinear relation between fluid film pressure and bearing kinematics as well as temperature increase due to power loss or adjacent heat sources into account as detailed as necessary. Both journal and thrust bearings are considered as they contribute to the system's stiffness and damping capabilities. The approach is applied to self‐excited pad vibrations of tilting pad thrust bearings as well as the run‐up simulation of a turbocharger rotor under different axial loads. Both models are validated against measurements. [ABSTRACT FROM AUTHOR]

In the present paper, the governing equations of a vibratory beam with moderately large deflection and arbitrary cross‐section are derived by using the first‐order shear deformation theory. The beam is homogenous, isotropic and it is subjected to the axial loads. The kinematic of the problem is according to the von‐Kármán strain‐displacement relations and the Hooke law is used as the constitutive equations. The partial differential governing equations describing the axial and transverse vibrations of homogeneous beams contain four coupled nonlinear equations with variable coefficients which are derived employing Hamilton's principle. The Galerkin method in conjunction with the perturbation technique is applied to obtain the linear natural frequencies. A parametric study is performed and the effects of different thickness functions such as linear, polynomial and trigonometric on the results are investigated. The non‐linear frequencies which contain the corrections on the linear frequencies are calculated. The corrected parts of the non‐linear frequencies are functions of the axial as well as the transverse amplitudes of the vibrations. The influences of the axial load and aspect ratio on the linear and non‐linear frequencies are studied too. To confirm the reliability of the vibration analysis carried out in the present paper, the analytical results are checked with the corresponding numerical results obtained from the finite element analysis. The numerical and analytical results are in a good agreement. [ABSTRACT FROM AUTHOR]

As a kind of lightweight structure with great economic benefits, metal/composite hybrid structure is raising rapidly among automobile safety components due to its excellent anti‐collision performance. In this paper, a new design was developed by introducing an induced circular hole to improve the energy absorption performance of the AL/CFRP hybrid thin‐walled tubes under different loading conditions. Quasi‐static experiments and finite element simulation were carried out on the hybrid tubular sample with induced circular holes, and the crash resistance of the number and diameter of induced round holes under different loading angles (θ) of 0°,10°, 20°, and 30° was analyzed through the verified finite element model. The results showed that the induction hole can effectively reduce the peak load and improve the energy absorption characteristics of the hybrid thin‐walled tube under the axial (0°) load. Under the inclined load, the energy absorption capacity of all samples decreased to different degrees with increasing loading angle, and the induced hole changed the deformation mode of the hybrid tube, especially under the 30° loading angle. The complex proportional assessment is then implemented on the optimal structures, and specific energy absorption, peak crush force, and crush force efficiency were selected as the objective functions to improve the overall impact resistance under different loading angles. Considering three design cases, the AL/CFRP hybrid thin‐walled structure with three groups of induced holes are finally found as the best energy absorbing devices. The work in this paper can provide a guide for the design of advanced energy absorbing devices for arbitrary loading condition. [ABSTRACT FROM AUTHOR]

In this research paper, a new method is developed that can be used as a precursor of violent rock failure. It is based on measuring the characteristics of rock failure using infrared radiation (IR) under uniaxial cyclic loading and unloading. The loading–unloading response ratio (LURR) is determined based on IR indexes such as average infrared radiation temperature (AIRT) and infrared radiation temperature rate (IRTR). The results show that the LURR based on AIRT revealed an overall rising trend and mutation that occurred in the last cycle, which can be used as a precursor of the imminent rock failure. By contrast, the LURR based on IRTR has a noticeable 'mutation‐rapid decrease' in the middle and later periods of cyclic loading and unloading, which can also be considered as an early precursor of rock failure. Combined with the precursors of the imminent rock failure, the categorized warning of rock failure is recognized. [ABSTRACT FROM AUTHOR]

This paper presents a mathematical model for the elastic analysis of single floating piles subjected to axial dynamic loads, that is based on treating the soil surrounding the pile as a Tajimi‐type viscoelastic continuum. The pile and the soil column underlying the pile tip are modelled using one‐dimensional rod theory, and this allows obtaining an elegant solution that requires solving a system of linear equations, instead of complicated integral equations. Closed‐form expressions are derived for the dynamic stiffness at the pile head, and the frictional resistance along the pile shaft. The presentation concludes with a discussion on the main mechanisms that govern the inertial response of floating piles, and an investigation on the sensitivity of the dynamic stiffness and of the frictional resistance to the main geometrical and material problem parameters. [ABSTRACT FROM AUTHOR]

To improve the crashworthiness and reduce vehicle weight, a crash box made of carbon fiber reinforced plastics (CFRP)/aluminum (Al) hybrid materials was introduced in the paper. Quasistatic axial compression tests and numerical simulations were conducted for pure Al tubes and CFRP/Al hybrid tubes. The simulation models were validated and were further employed to investigate the effects of geometry, aluminum tube thickness, fiber wrapping angle and CFRP layers on the crashworthiness of the hybrid crash box under axial loading and 30° oblique collision. The multiobjectives were taken to obtain the optimal geometrical dimensions, aluminum tube thickness, wrapping angle, and the number of layers. The crashworthiness of the optimal CFRP/Al hybrid crash box was compared with that of original aluminum crash box. It was found that the mass of the crash box was reduced by 35.21%, while the specific energy absorption (SEA) and mean crushing force (Fmean) were increased by more than 18% and 46%, respectively. The paper was aimed to provide some references for the design and optimization of composite crash box. [ABSTRACT FROM AUTHOR]

This paper proposed a new approach for the strength interaction diagram (N‐M diagram) of FRP strengthened square steel reinforced high strength concrete (SSRHSC) column, considering the influence of the applied load eccentricity on the ultimate conditions of FRP strengthened high‐strength concrete (HSC). The analytical model for the strength interaction diagram of FRP strengthened SSRHSC (FRPS‐SSRHSC) columns, which incorporated the stress–strain models of constitutive materials into the rectangular stress block (RSB) method, was developed and verified against test data. The strength interaction diagrams of FRPS‐SSRHSC columns developed based on the proposed analytical model matched well with the test results, while the strength interaction diagrams developed using available design codes overestimated the experimental strength interaction diagrams. The effect of confinement ratio and longitudinal FRP strengthening on the strength interaction diagrams was examined via parametric analyses. It was found that longitudinal strengthening had a negligible influence on the axial load and bending moment when the axial load was applied at a small eccentricity but had a substantial influence when the axial load was applied at a large eccentricity. [ABSTRACT FROM AUTHOR]

In this paper, the frequency stability analysis of a fluid conveying cantilever viscoelastic carbon nanotube (CNT) in the Kelvin–Voigt material model with slip boundary condition (BC) regime on a viscoelastic Pasternak foundation and under axial load has been performed based on nonlocal Euler–Bernoulli thin beam theory. The governing partial differential equation of motion (EOM) and its associated BCs have been derived using the Hamilton principle. The governing EOM has been converted into an ordinary differential equation using mode summation technique and solved by applying the extended Galerkin method. Then, the frequency stability analysis has been carried out for the vibrational response of CNT in the state‐space form. The obtained results have been validated with the literature works. The effect of changes of various parameters like elastic stiffness, shear stiffness and damping coefficients of foundation, nonlocal scale‐effect parameter of the nanotube, fluid flow Knudsen number, mass ratio, structural damping of the nanotube and applied axial force have been investigated in terms of frequency to predict the occurrence of different instability modes for the system. It is concluded that flutter and divergence instabilities in the vibration of the viscoelastic CNT are significantly affected by changes of different above‐mentioned parameters. [ABSTRACT FROM AUTHOR]

Reinforced concrete structural walls are major vertical lateral load‐resisting members in reinforced concrete structures located in seismic regions. It is important to understand and evaluate the hysteresis behavior of these members for an efficient earthquake‐resistant design. Among the various models available for estimating this hysteretic behavior, the Pivot hysteresis model, which models hysteretic behavior through parameters α and β, respectively, representing the unloading stiffness and pinching behavior, has been effective and efficient for use with columns. In this paper, an effort is made to extend the application of the Pivot hysteresis model to reinforced concrete walls. Key variabratiosuch as axial load ratio, wall height‐to‐length ratio, web reinforcement indices, boundary element reinforcement indices, and length‐to‐effective thickness ratio were considered to derive expressions for α and β suitable for walls. Equations for α and β were calibrated through the hysteretic test data of 108 wall specimens subjected to cyclic loading and exhibiting different failure modes. The calibration is based on the optimization of energy dissipation for specimens from the collated database—a numerically complex task achieved through a superior optimization technique known as Simulated Annealing. The proposed formulations showed reasonably good accuracy in predicting complex hysteretic responses when verified against an extensive database of wall test specimens with flexural and shear modes of failure. [ABSTRACT FROM AUTHOR]

Summary: The present study deals with introducing a novel approach toward estimating the effective width of flanged reinforced concrete shear walls (FRCSWs). Due to the paucity of studies in assessing the effective width of nonrectangular sections, this paper aims at proposing efficacious formulations for the effective width estimation of short, squat, and slender T‐ and U‐shaped reinforced concrete (RC) shear walls subjected to the simultaneous action of the axial and lateral loading. To this end, at first, FRCSWs are simulated in the flanged shear wall numerical laboratory (FlashLab) program, which utilizes the finite element Abaqus software to analyze the walls. Thereafter, employing the developed numerical models, an extensive parametric investigation is conducted for a wide range of the key parameters. General expressions have then been developed to estimate the effective width of flanged RC shear walls invoking the evolutionary polynomial regression (EPR) analysis in conjunction with the genetic algorithm (GA). To assess the capability of the established equations in predicting the effective width of flanged sections, R‐factors have been calculated for all the cases examined in this study, which ranged between 0.78 and 0.94. Furthermore, a comparison has been made among the results attained through the proposed methodology and those obtained using the conventional design codes. It was revealed that the relative error obtained employing the proposed formulations is less than that of the corresponding values of the design codes by approximately 30% on average. The superiority of the established framework stems from consideration of the following: (1) influential parameters, (2) effective width variations at different performance levels, (3) loading direction, and (4) type of the wall in the effective width calculation process. [ABSTRACT FROM AUTHOR]

In this paper, a comparative study of the very‐high‐cycle fatigue (VHCF) behavior of railway wheel steel under axial loading and rolling contact loading was conducted. Fatigue tests were performed with an ultrasonic fatigue test machine under axial loading, and the fracture surfaces from the fatigue tests and shattered rims taken from the failed railway wheels were observed. The wheel steel under axial loading presents a VHCF behavior with Mode I crack, and that under rolling contact loading is a VHCF behavior with mix Mode II–III crack. For the VHCF behavior with Mode I crack, surface and interior crack initiation occurred with equal probability at both low and high stress levels and produced a dual linear S–N curve since the value of fatigue limits for the surface and interior crack initiation are close. For the VHCF behavior with mix Mode II–III crack, cracks were initiated from the interior Al2O3 inclusion, and the fatigue life was beyond 107 cycles. Fatigue bands were observed on the fracture surface under rolling contact loading. The ferrite nanograins formed due to the stress state of shear plastic strain with a large compressive stress. The formed nanograins were softer than the matrix caused by the redistribution of the carbon. Highlight: The VHCF under rolling contact loading is a failure mode of mix Mode II–III crack.The NG massively formed in the VHCF with mix Mode II–III crack.The shear plastic strain with a large compressive stress will help NG formation. [ABSTRACT FROM AUTHOR]

This paper presents a computationally efficient beam‐column element to simulate the nonlinear flexural and shear behaviors of reinforced masonry shear walls subjected to bilateral seismic forces. A three‐field mixed formulation based on the Hu‐Washizu variational principle is adopted. This mixed element is free of shear locking, and allows a wall to be modeled with one element. The axial and flexural responses are evaluated with a fiber‐section model at each integration point along the element, while the shear response in each loading direction is represented by a phenomenological model. The element accounts for the influence of the axial load, wall aspect ratio, and wall flange, if any, on the shear response of a wall. To consider axial‐flexure‐shear interaction, the shear model takes into account the axial stress resultant from the fiber‐section model, and the compressive strength of masonry in the fiber‐section model decreases when severe shear damage developed. The model has been calibrated and validated with experiment data. It has been demonstrated that it is able to reproduce experimental results from quasi‐static cyclic loading tests of single walls as well as shake‐table tests of wall systems with good accuracy. Furthermore, the ability of the proposed model to simulate the response of reinforced masonry shear wall systems subjected to bilateral seismic forces has been examined by comparing with results from a detailed finite element model. [ABSTRACT FROM AUTHOR]

This paper is aimed to examine the axial compression performance of reinforced concrete (RC) base column specimens strengthened by fiber‐reinforced high‐performance concrete (FRHPC) jackets using the enlarged cross‐section method. For this purpose, the axial compression performance test is performed on one un‐strengthened column and four strengthened columns to assess the effects of FRHPC jacket thickness, whether the jacket was configured with stirrup and the spacing of stirrup were considered. Based on the theory of confined concrete and the FRHPC principal structure relationship, a theoretical calculation model is also established to explore the axial load‐carrying capacity of the columns. The test results indicate that an increase of the cross‐sectional reinforcement of the FRHPC jacket can enhance the axial compression load capacity and ductility of the columns. Furthermore, an increase in the FRHPC jacket thickness leads to the growth of the load capacity; however, there is no significant increase on the ground of its ductility. The addition of stirrup in the FRHPC jacket can improve both load capacity and ductility of the columns such that the smaller the spacing of the stirrup, the greater the increase of both load capacity and ductility. The predicted results by the proposed model are in good agreement with those of the tests. [ABSTRACT FROM AUTHOR]

The effects of surface roughness and material properties of the planetary roller screw mechanism (PRSM) on the axial stiffness and load distribution are rarely studied. In this paper, the load distribution model is presented by incorporating into friction factor and surface microtopography. The microcontact model is built by considering elastic and plastic regimes to calculate the total actual contact area. Moreover, the load distribution model is modified by introducing surface microcontact coefficient. Then, the influences of the nut position, fractal dimension, fractal roughness, friction factor, axial load, and material yield strength on the axial stiffness and load distribution are studied in detail. The numerical results show that the axial stiffness rises with the increment of the nut position, axial load, fractal dimension, and yield strength, and reduces with the fractal roughness and friction factor increasing. In addition, the uniformity of the load distribution increases with the increment of the fractal roughness, and drops with the increase of the fractal dimension and material yield strength. This investigation lays the foundation for the design, manufacturing, and use of the PRSM. [ABSTRACT FROM AUTHOR]

This paper presents the results of an experimental investigation on the behavior of glass fiber reinforced polymer (GFRP) bar‐reinforced hollow‐core (GFRP‐HC) circular concrete specimens under concentric, 25 mm and 50 mm eccentric axial loading and four‐point bending. The main parameters investigated include the type of reinforcing bars, pitch of the helices and loading conditions. The test matrix of this study consists of 12 specimens, among which nine specimens (850 mm high) were tested under concentric and eccentric axial loading and the remaining three specimens (1500 mm long) were tested under four‐point bending. The specimens were circular in cross‐section with an outer diameter of 214 mm and an inner circular hole diameter of 56 mm. The experimental results showed that, for the similar amount of reinforcement, steel bar‐reinforced hollow‐core (steel‐HC) specimens sustained higher loads than the GFRP‐HC specimens under different loading conditions. Also, the steel‐HC specimens achieved higher ductility than the GFRP‐HC specimens under 50 mm eccentric axial loading and four‐point bending. However, under concentric and 25 mm eccentric axial loading, the GFRP‐HC specimens achieved higher ductility than the steel‐HC specimens. The close pitch of the GFRP helices significantly enhanced the load carrying capacity and ductility of the GFRP‐HC specimens. [ABSTRACT FROM AUTHOR]

Li‐ion batteries are widely used in electric vehicles (EVs) propulsion. Therefore, ensuring their safety under mechanical abuse and accidental loads is a major challenge for the industry. To get a better understanding of the battery behavior in such cases, material calibration and computational modeling of the battery cells are essential. This paper aims to develop a universal homogenized model for an 18,650 cell that can predict cell behavior under both axial and lateral loading cases as well as three‐point bending. Previous homogenized models presented in the literature have covered one or two of these cases, but none have been validated in all these three major loading scenarios. To achieve this, precise shell casing and jellyroll material calibrations were performed. The features included in this universal model are (I) uncoupled calibration of axial and lateral properties for the cylindrical jellyroll from experiments performed in these two loading directions and employment of an anisotropic crushable foam model to simulate these features, (II) using Hill's anisotropic yield criteria and modified Mohr–Coulomb fracture criteria for the shell casing. The universal model developed here was able to predict the response of the cell in all lateral, axial, and bending loading scenarios. A comparison of this model with the previously developed isotropic models shows the special advantage of the new model in cases of axial loading and bending. However, for lateral compression cases, even the isotropic model provides a very close prediction. The experiments used for this study were all performed on fresh discharged cells under quasi‐static loading. [ABSTRACT FROM AUTHOR]

Models for the pre‐ and post‐yield energy dissipation in reinforced concrete (RC) members are developed using a database of about 1200 tests with over 18,000 load cycles. Before yielding, the equivalent viscous damping ratio exceeds 5%, especially if the member is initially uncracked. It can be considered by using either a dedicated pre‐yield hysteretic model with parameters established in the paper or global viscous damping and special provisions against double counting of energy dissipation. The post‐yield model can be combined with various post‐yield hysteretic laws. It accounts for the member's type, shear‐span‐to‐depth ratio and likely failure mode, the continuity, ratio, and surface characteristics of longitudinal bars, and for FRP wrapping, if any. Alternatively, it recognizes only four member types but accounts also for the transverse steel ratio and the normal stress due to the axial load. [ABSTRACT FROM AUTHOR]

Understanding coal and rock permeability, and the corresponding influence on stress, is important in the field of energy development. In applied engineering, there is a tendency to employ three‐dimensional methods that are simpler, less time‐ and cost‐expensive, less computationally expensive, and larger scale. Thus, a numerical simulation fluid‐solid coupling method is proposed in this paper. The proposed numerical simulation method utilizes the stress‐permeability test results for elastic and plastic coal samples. The permeability models of the elastic and plastic coal samples under loading and unloading were obtained by fitting the experimental results and embedded them into FLAC3D software by using FISH language. The results of the uniaxial and triaxial flow simulations are consistent with the experimental results, thereby confirming the accuracy and feasibility of the numerical method proposed in this paper. This allows the permeability of the numerical reservoir model to be continuously updated according to the current stress level in the production process. [ABSTRACT FROM AUTHOR]

This paper extends the knowledge into the mechanical behaviour characterizations and constitutive modelling of polyethylene (PE) foam under multiple loading and unloading. The mechanical properties of PE foam subjected to single loading cases can be obtained by uniaxial compressive tests at quasi‐static and dynamic states. And the multiple loading and unloading behaviours of the foam can be revealed by consecutive drop tests. The major objective of this research is to propose a phenomenological model consists of shape function and modulus function, which can be predicted compressive response of PE foam for single loading cases. The constitutive models of foamed PE under multiple loading and unloading conditions are established by both using hyperbolic function, where the relations between coefficients and residual strain are introduced. And then, experiments are conducted to validate the proposed model by comparing the constitutive models proposed in this paper and those predicting by finite element software ABAQUS with those by experiments, showing that the proposed models are more accurate for predicting acceleration‐times curves of multiple drop scenarios. [ABSTRACT FROM AUTHOR]

The optimisation design of air-cored axial flux permanent magnet (PM) generator is a complex non-linear problem with constraints, multi-objective, multivariable and multi-peak value. The different variables will affect the same optimisation goal. In this paper, a multi-objective optimisation design of air-cored axial flux PM generator based on Taguchi-response surface method (RSM) is proposed. The main characteristics of generator efficiency, power quality, induction electromotive force and other main characteristics are taken as optimisation objectives. The parameter ranges that influence the optimisation objectives of the motor are selected as optimisation variables. First, the orthogonal matrix is established according to the number of selected parameters and the level factor of each parameter and the finite element method is used to solve the experimental matrix. Then, the mean and variance of the simulation results are analysed. The optimisation mathematical model was established between the target and the impact factor by using RSM for the conflicting factors, which can determine the optimal variable parameters. The effectiveness of the optimisation method is verified by finite element analysis and prototype experiments. The results show that the performance of optimised core less flux PM generator has been greatly improved. [ABSTRACT FROM AUTHOR]

To investigate the seismic behavior of high-strength concrete-encased concrete-filled steel tube (HSC-encased CFST) composite column, eight specimens with a high axial compression ratio were tested under lateral cyclic loading and constant axial compressive loading in this paper. Key points on the load-displacement skeleton curve of the composite columns were obtained based on the experimental results. The test parameters include the axial compression ratio, volume stirrup ratio, stirrup form, and the diameter-width ratio. All specimens failed in the flexural mode, with the crushing of compressive concrete and losing of vertical load-carrying capacity. The ductility and deformation capacity decrease with the axial compression ratio increasing, and enhancing the volume stirrup ratio within 1.33-1.63% can provide an effective confinement of composite column. The ultimate strength of specimen with the octagonal stirrup is 23.8% higher than that with well stirrup, and the ductility and load-carrying capacity are enhanced due to the increase of diameter-width ratio. A degrading trilinear restoring force model of HSC-encased CFST composite column with a high compression ratio is proposed. The comparisons made between calculated results and test results show such a high agreement, which indicates the proposed restoring force model is applicable to such HSC-encased CFST composite column. It provides a theoretical basement for further research on the nonlinear dynamic analysis of such CFST composite column. [ABSTRACT FROM AUTHOR]

The newest version of shells buckling standard prEN 1993‐1‐6 (2021) adopts linear elastic buckling stress expressions for steel perfect cylinders under axial, circumferential, and torsional effects separately. However, there are no explicit detailed rules that cover the influence of two or more loading combinations on the cylinder buckling resistance, considering a full‐length domain and different boundary conditions. Consequently, this paper looks into such a topic, which will be a useful reference for future research extensions. The examined cylinders were subjected to three loading configurations: axial plus pressure, axial plus torsion, and axial, pressure, and torsion altogether. The finite element (FE) buckling capacities were compared with the prEN 1993‐1‐6 (2021) buckling strengths, from which several findings were obtained. Aspects such as the load configuration applied to a cylinder, the length domain in which a cylinder falls, and the boundary type of a cylinder's ends each led to distinctive and complex descriptions of buckling behavior. The outcomes of this study will in turn assist in developing the current standard prEN 1993‐1‐6 (2021) and its recommendation ECCS EDR5 (2013), particularly the chapter that is relevant to cylindrical shells of constant wall thickness under general loading. [ABSTRACT FROM AUTHOR]

The concrete confinement is improved in octagonal concrete‐filled double steel tubular (OCFLDST) columns by linking the steel tubes with steel plates and thereby it enhances ductility. It has the potential to improve the torsional resistance in concrete‐filled steel tubular cross‐sections. This paper investigates the torsional behavior of OCFLDST through analytical and numerical investigations. The numerical model for OCFLDST is developed in ABAQUS and validated using test data available in the literature for axial loading conditions. The validated model is then subjected to pure torsion to study the torsional behavior of OCFLDST. In comparison with bare steel tubes, concrete filling of linked steel tubes has increased the torsional resistance by 33%. Further, parametric studies are conducted to understand the influence of various parameters like yield strength and thickness of the outer steel tube, compressive strength of concrete, the thickness of the linking plates, and axial load ratio. The numerical results are compared with the proposed expression for finding the torsional capacity based on St. Venant's torsion theory. The proposed capacity prediction is in good agreement with the numerical results. [ABSTRACT FROM AUTHOR]

This paper presents investigations on the load‐bearing behaviour of sandwich panels under bending load and axial load. The sandwich panels investigated here have the special feature that they consist of two face sheets, a polyurethane core and two integrated reinforcement profiles. These integrated profiles allow the stiffness of the panels to be significantly increased, resulting in a delayed wrinkling failure and thus opening up new fields of application. Experimental results from bending tests are presented. From these results, analytical approaches are then described that can be used to predict the load‐bearing behaviour under axial loading. In addition, the test setup is described, which will be used in the future for the experimental investigation of the panels under axially loading. [ABSTRACT FROM AUTHOR]

Cylindrical shells are frequently used in industrial constructions, for example in pipes, towers and masts and are often subjected to fatigue loading. Two common welded constructional details were studied: i) detail 1, the wall thickness transition with a circumferential butt weld and ii) detail 2, the welded ring stiffener. Both details are loaded with axial stresses due to N and/or M. In the new Eurocode prEN 1993‐1‐9:2021 three different fatigue design stress methods are provided in general. For these two constructional details, beside the modified nominal stress method, the hot spot stresses and effective notch stresses are determined with Finite‐Element‐Analyses, with variation of geometric parameters, like shell thickness t, radius‐over‐thickness‐ratio, t2/t1‐ratio at the thickness transition and thickness ts of the ring stiffener. Stress concentration factors for the different fatigue design stress methods are presented and the influence of the geometric parameters are investigated. Especially the difference between a plate with an infinite radius‐over‐thickness‐ratio and the pipe with a finite radius‐over‐thickness‐ratio is shown. Also, the influence of the shell thickness is investigated. For comparison of the three different methods the utilization factors of the hotspot stress method and the effective notch stress method are compared with those of the modified nominal stress method. A recommendation is given, which design stress method is appropriate for the two studied details, depending on the geometric parameters. [ABSTRACT FROM AUTHOR]

ISO 14346 permits fillet welds in rectangular hollow section (RHS) joints to be designed either (i) to develop the capacity of the connected brace or (ii) to resist the actual load(s) in the brace (i.e. as "fit‐for‐purpose"). However, no methods for design according to approach (ii) are given in the ISO or any European standard. In this paper, data from 41 weld‐critical tests on RHS gapped K, T, Y and X joints under brace axial load(s) are analysed to determine a reliable method for the design of fillet welds as "fit‐for‐purpose". "Weld effective length" formulae are evaluated in conjunction with EN 1993‐1‐8 (directional and simplified methods) according to the standard procedure of EN 1990. A reliable method, based on ISO 14346, is proposed for calculating the design resistance of all‐around fillet welds in RHS gapped K, T, Y and X joints. Updates to the minimum fillet weld throat thicknesses required to develop the capacity of a connected RHS brace are also discussed. [ABSTRACT FROM AUTHOR]

Summary: In order to improve the seismic performance of traditional superimposed reinforced concrete shear walls, a kind of superimposed reinforced concrete shear wall with X‐shaped steel plate bracings (labeled as SRCXSW) was proposed in this paper. And seismic behaviors of three 1/2‐scale shear walls including two SRCXSWs with different axial load ratios (ALRs) and one cast‐in‐place reinforced concrete shear wall with X‐shaped steel plate bracings (labeled as CRCXSW) were investigated by the quasi‐static loading test. Experimental results indicated that SRCXSW and CRCXSW with the same ALR exhibited the similar seismic behaviors, different ALRs applied in SRCXSW greatly affected the seismic behaviors in terms of load‐bearing capacity, deformation, lateral stiffness, and energy dissipation capacity and slightly affected the failure mode and cooperative mechanism between the precast and cast‐in‐place concrete layers. In particular, a high ALR applied on SRCXSW had little effect on the stiffness degradation before yielding, but accelerated the post‐yield stiffness degradation. Then, based on the discussion conclusion about the contribution of three mechanisms to the load‐bearing capacity varying with aspect ratio, a modified strut‐and‐tie model for predicting the maximum strength of specimens was proposed, and good predictive ability under different ALRs was verified by experimental and finite element analysis (FEA) results. Besides, FEA based on OpenSees was implemented to further investigate the effect of critical parameters, FEA results showed that ALR and longitudinal reinforcement ratio in boundary element had a significant influence on the load‐bearing capacity and deformation capacity of SRCXSW. And a higher volumetric ratio of X‐shaped steel plate bracings and longitudinal reinforcement ratio in boundary element led to a greater load‐bearing capacity but their contribution decrease with the increase of ALR. [ABSTRACT FROM AUTHOR]

Most existing studies on fiber reinforced polymer (FRP) confined concrete have focused on undamaged concrete that is subjected to uniaxial monotonic compression. However, FRP jackets are usually applied to concrete columns with existing material damage and potential future damage. This paper investigates FRP confinement on concrete with damage before and after FRP jacketing. A total of 32 FRP‐confined concrete specimens were tested under axial compression in this work. The prior damage before FRP jacketing was implemented as predamaging by applying preloading and then release on the plain concrete specimens. The post damage after FRP jacketing was performed by applying cyclic axial compression loading on FRP‐confined concrete specimens. The test results reveal that the concrete predamage levels have significant influences on the cyclic stress–strain curve and envelop stress–strain curve for FRP confined concrete under cyclic loading. Existing models on ultimate state, plastic strain, reloading and unloading moduli were evaluated and investigated in this work. [ABSTRACT FROM AUTHOR]

In order to reduce the crushing damage at shear wall corners and improve the seismic behavior of ordinary concrete shear walls, this paper develops a high‐performance steel‐polyvinyl alcohol (S‐PVA) hybrid fiber‐reinforced concrete (HyFRC) shear wall. Two‐phase studies from experiment to numerical analysis were carried out. The first phase investigates the seismic behavior of S‐PVA HyFRC shear walls by quasi‐static tests. Five S‐PVA HyFRC shear walls were fabricated, designed with various S‐PVA HyFRC distribution heights and locations. One ordinary concrete shear wall was fabricated as a reference specimen. The test hysteretic curve and skeleton curve were analyzed. Experimental results confirm that using the S‐PVA HyFRC at the bottom of the shear walls can improve their overall seismic behaviors effectively. Based on the test results, the optimal distribution height and location of S‐PVA HyFRC that generate the most cost‐effective benefits were determined. The second phase developed a numerical model to simulate the shear wall's behavior in OpenSees using SFI‐MVLEM model. Confined and unconfined constitutive models for S‐PVA and ordinary concrete under compression and tension were established and incorporated in the model. The model was compared with the experimental data and then was used for a parametric analyses, which provide theoretical basis for the seismic design and nonlinear analyses of HyFRC shear walls. Five parameters were considered in the parametric analyses, including the height of HyFRC in shear wall, the length of boundary elements, the ratio of longitudinal reinforcement, the ratio of transverse reinforcement, and the axial load ratio. Results suggest that the plastic hinge calculated by well‐developed equations can be used in the design of the HyFRC height. Current regulations about the boundary element length are applicable to HyFRC shear wall and the axial compression ratio is suggested to be smaller than 0.6. [ABSTRACT FROM AUTHOR]