Full Hysteresis Loops Research Articles

Study on the Damping Efficiency of a Structure with Additional Viscous Dampers Based on the Shaking Table Test

This study specifically focuses on the damping efficiency of a damped structure with additional viscous dampers. A two-layer steel frame structure with eight sets of viscous dampers is used to conduct a series of seismic simulation shaking table tests, including a non-damped structure without dampers and two damped structures with dampers placed at 1/2 and 1/6 of the beam span, respectively. By conducting these tests, the energy dissipation, force, and displacement of the damper, as well as the parameters of the structure such as floor displacement and acceleration, are obtained. The main damping efficiency indicators of the damped structure are calculated, including the additional damping ratio, inter-story displacement utilization rate, as well as the reduction rate of the vertex displacement and the base shear relative to the non-damped structure. The study shows that the viscous dampers exhibit full hysteresis loops and a strong energy dissipation capacity in the structure. The seismic response of the vertex displacement and base shear in the damped structure is significantly smaller than that in the non-damped structure. Under different seismic levels, including frequent earthquakes, occasional earthquakes, and rare earthquakes, the damping effect of the dampers placed at 1/2 of the beam span is significantly better than that placed at 1/6 of the beam span. For example, the additional damping ratio for the X-direction artificial wave REN is 19% and 11%, 20% and 13%, and 13% and 11%, respectively. The patterns for inter-story displacement utilization ratio, reduction rate of the vertex displacement, and reduction rate of the base shear are similar. The research findings strongly indicate that the damped structure with additional viscous dampers exhibits excellent damping efficiency. In future damping design, designers need to fully consider the placement of viscous dampers within the beam span.

Numerical analysis on seismic behavior of a novel steel-timber composite frame column

Steel-timber composite structures are a novel hybrid structural system that combines the advantages of both steel and wood structures, holding great promise for various applications. In this paper, the seismic behaviors of steel- timber composite columns are investigated based on finite element analysis. The reliability of the finite element model is validated by quasi-static test results. Numerical analysis results indicate that the proposed steel- timber composite systems is with high ultimate bearing capacity, full hysteresis loops, and strong displacement ductility, demonstrating excellent seismic performance. The axial compression ratio, steel tube thickness, and flexural point height significantly influence the seismic resistance of the structure.

A Review on Slit Steel Shear Walls: Development, Implementation, and Performance

Over centuries, natural phenomena have claimed a large number of lives and caused large amounts of damage. However, they were the reason for the development of knowledge and science. In engineering, there is no doubt that earthquakes were the driving force behind many design philosophies and advanced technologies. In this regard, steel plate shear walls (SPSWs) represent one of the technologies employed in both new constructions and existing structures to bolster lateral load resistance. In addition to its high elastic stiffness and strength, SPSWs often experience significant pinching during their hysteretic response unless heavily stiffened. Thus, numerous investigations have been performed recently to enhance the seismic behavior of SPSWs during severe ground shaking. The shear walls of steel plates have been studied in various ways, including stiffened and unstiffened steel plates, low yield strength steel plates, SPSWs perforated with circular holes or vertical slits, steel walls with stiffened and unstiffened openings. A stiffened SPSW panel dissipates significantly more energy than an unstiffened panel, as well as exhibiting a ductile and stable behavior. In view of its high elongation, the SPSW with low yield point has the best damping capacity. It has been demonstrated that steel walls perforated with circular holes have improved energy dissipation, in addition to allowing utilities to pass through their openings. Vertical slits on steel plate shear walls produce an exceptionally full hysteresis loop with improved performances. Slit steel walls (SSWs) can sustain a drift of over 3% while experiencing minimal hysteresis degradation. Additionally, a frame with a SSW can endure up to 6% drift without significant damage, surpassing expected ductility levels of a special moment frame, particularly with efficient slit geometry.

Experimental investigation and numerical modelling of the cyclic plasticity and fatigue behavior of additively manufactured 316 L stainless steel

This study addresses the critical need for a constitutive model to analyze the cyclic plasticity of additively manufactured 316L stainless steel. The anisotropic behavior at both room temperature and 300 °C is investigated experimentally based on cyclic hysteresis loops performed in different orientations with respect to the build direction. A comprehensive constitutive model is proposed, that integrates the Armstrong-Frederick nonlinear kinematic hardening, Voce nonlinear isotropic hardening and Hill's anisotropic yield criterion within a 3D return mapping algorithm. The model was calibrated to specimens in the 0° and 90° orientations and validated with specimens in the 45° orientation. A single set of hardening parameters successfully represented the elastoplastic response for all orientations at room temperature. The algorithm effectively captured the full cyclic hysteresis loops, including historical effects observed in experimental tests. A consistent trend of reduced hardening was observed at elevated temperature, while the 45° specimen orientation consistently exhibited the highest degree of strain hardening. The applicability of the model was demonstrated by computing energy dissipation for stabilized hysteresis loops, which was combined with fatigue tests to propose an energy-based fatigue life prediction model.

Experimental and numerical study on the seismic behavior of RC frame with energy dissipation self-centering hinge joints

Conventional reinforced concrete joints dissipate seismic energy through the deformation of plastic hinges, resulting in excessive residual deformation and difficult-to-repair damage. This paper proposes a new beam-column joint type: an Energy Dissipating Self-Centering Hinge Joint (EDSCHJ) with a high-stiffness spring and replaceable dampers fixed at the joint zone. The high stiffness spring provides restoring forces, and the replaceable dampers are utilized to dissipate seismic energy. A quasi-static test was conducted to investigate the seismic performance of the EDSCHJ. Three types of self-centering hinge joints with different dampers are designed and tested, and the hysteretic response, skeleton curve, stiffness degradation curve, and equivalent viscous damping coefficient of the EDSCHJ were obtained. The test results show that the specimens are undamaged at a story drift of 5%, the EDSCHJ without damper exhibits excellent self-centering capability with only a small residual deformation, the hysteresis curve of the EDSCHJ with dampers exhibits a full hysteresis loop with good energy dissipation capacity, the high-stiffness spring has remained elastic without strength degradation, and the lateral stiffness derived from the skeleton curve aligns closely with theoretical calculations. Finally, the finite element model of EDSCHJ is established and validated by comparing the test and numerical results. The structural parametric analysis reveals that as the relative lateral stiffness increases, the dynamic responses of the structure with EDSCHJ exhibits a increasing trend in displacement and an decreasing trend in acceleration and base shear. Additionally, the simulation results indicate an optimum relative stiffness ratio ranging from approximately 0.09 to 0.61.

High Temperature Magnetic Properties of Selected Steel Grades

In order to effectively control the microstructure of steel strip during manufacture it is vital that techniques be developed to monitor microstructural changes in the steel at high temperatures. Electromagnetic non-destructive testing is increasingly being used in these applications as it is non-contact, robust, relatively inexpensive and has the potential to provide real-time feedback to control the manufacturing process. However, if the data produced by these systems is to be fully exploited it is necessary to accurately measure the magnetic properties of steel grades of interest at temperatures up to the Curie point. This work details measurements carried out to assess the magnetic properties of selected steels grades, supplied by Tata Steel, up to the Curie temperature using a novel test rig based on a modified Epstein frame designed by the University of Manchester with high temperature trials at the University of Warwick. Several steel grades are studied with the full magnetic hysteresis (BH) loops reported during heating and cooling, along with extracted magnetic parameters including coercivity, magnetic saturation and magnetic permeability. The magnetic parameters of the selected steel grades are compared and implications of the results on electromagnetic monitoring of steel strip during manufacture considered. Results show the developed system has the potential to provide valuable data to inform online electromagnetic monitoring systems.

Hysteretic behavior and recoverability research on the shape memory effect of SMA bars under cyclic loading

To utilize the special shape memory effect of shape memory alloy (SMA) to develop energy dissipation devices with a good energy dissipation effect and easy recovery of residual deformation after an earthquake, six SMA bars with a diameter of 14 mm were tested under multiple loading schemes in this paper. Hysteretic performance indicators, such as the hysteresis loop, energy dissipation capacity, secant stiffness, equivalent damping ratio and deformation recovery rate, were analyzed. The results illustrated that all specimens exhibited the desired full and stable hysteresis loops and a high residual deformation recovery rate achieved by water-bath heating and cooling after being subjected to 6.0% tensile strain. Due to the characteristics of SMA material, excessive compressive strain caused the stress value to soar, and hysteresis loops contributed to the phenomenon of tension–compression stress imbalance and affected the deformation recovery rate. No significant differences were observed in the bearing capacity and energy dissipation capacity of the same specimen with a strain amplitude of 6.0% after repeated loadings, indicating that martensitic shape memory alloys (SMAs) have stable mechanical characteristics and favorable recycling performance. The tensile cyclic constitutive model and tension–compression cyclic constitutive model of the martensite shape memory effect were proposed. Based on MATLAB/Simulink software, numerical simulations were carried out. The simulation results and fitted the experimental results, which proved the theoretical support for utilizing the shape memory effect of martensite SMA.

Evaluation of seismic performance and effective lateral stiffness for corrugated steel-plate concrete composite structural walls repaired using bottom corner dampers

The plastic hinge regions of conventional structural walls often experience severe damage after earthquakes. In this study, a new repair method is proposed for corrugated steel-plate concrete composite structural walls based on corner failure. The proposed method involves installing a tension–compression dampers at the damage corners. The seismic performance of the retrofitted composite structural walls was evaluated by quasi-static test. The results demonstrated that the retrofitted walls had full hysteresis loops and large lateral displacement. The damage of retrofitted walls was primarily concentrated at the corner dampers. And the bottom corner dampers can be easily replaced after earthquakes. However, there was a substantial loss in the effective lateral stiffness of the retrofitted walls. Macro finite element models were then implemented to investigate the effective lateral stiffness of the retrofit walls using OpenSees. Lastly, an effective lateral stiffness equation for retrofit walls was suggested using a parametric regression analysis.

Behavior of magnetoelectric hysteresis and role of rare earth ions in multiferroicity in double perovskite Yb2CoMnO6

Double-perovskite multiferroics have been investigated because alternating orders of magnetic ions act as distinct magnetic origins for ferroelectricity. In Yb2CoMnO6, the frustrated antiferromagnetic order emerging at TN = 52 K induces ferroelectric polarization perpendicular to the c axis through cooperative O2− shifts via the symmetric exchange striction. In our detailed measurements of the magnetoelectric properties of single-crystalline Yb2CoMnO6, we observe full ferromagnetic-like hysteresis loops that are strongly coupled to the dielectric constant and ferroelectric polarization at various temperatures below TN. Unlike Lu2CoMnO6 with non-magnetic Lu3+ ions, we suggest the emergence of additional ferroelectric polarization along the c axis below the ordering temperature of magnetic Yb3+ ions, TYb ≈ 20 K, based on the spin structure established from recent neutron diffraction experiments. While the proposed description for additional ferroelectricity, ascribed to the symmetric exchange striction between Yb3+ and Co2+/Mn4+ magnetic moments, is clearly given, anomalies of dielectric constants along the c axis are solely observed. Our interesting findings on magnetoelectric hysteresis and the possible development of additional ferroelectricity reveal notable characteristics of double perovskites and provide essential guidance for the further examination of magnetoelectric functional properties.

Numerical Study on An Innovative Elastomeric‐Steel Cushion Damper

AbstractIn this research cyclic performance of a newly developed energy dissipating device is investigated through finite element studies. The device is constructed using yielding steel Cushions and bonded rubber cubes. The Cushions dissipate the induced energy of earthquakes while the rubber cubes provide lateral constraint and post‐elastic stiffness for the bracing system due to the Hyperelastic behavior of the rubber material. The main advantage of the proposed damper is its little maintenance expense and cost efficiency since the steel Cushions can easily be replaced. In this paper, the requisite details are presented for the application of the proposed device. It can be observed from the analytical results that the proposed damper exhibits full and wide hysteresis loops resulting in excellent equivalent viscous damping while maintaining adequate lateral stiffness at various displacement levels. The dissipated energy per cycle and the respective effective stiffness and equivalent damping of the model are presented in this study.

Experimental study on seismic behavior of steel structure with cellular beams and composite concrete slab

Quasi-static testing was conducted on a single-bay two-story cellular steel beam structure with composite concrete slab to evaluate the seismic performance of the frame under cyclic lateral loading. Test measurements of the cellular beams, joints, columns, and slabs were presented and analyzed in detail. The failure modes and damage mechanisms of the specimens were investigated, and the hysteresis behavior, strength and stiffness degradation, ductility, and energy dissipation of the structure were analyzed. The composite effects of the concrete slabs under cyclic loads were also evaluated. The results indicate that the structure exhibited a full hysteresis loop, and the structure had a good capacity for energy absorption. After the peak load of the skeleton curve for the upper frame layer had been reached, the bearing capacity of frame A decreased more rapidly than that of frame B, and the strength attenuation and stiffness degradation were more obvious for frame A. The ductility coefficients of the upper layers of the two frames were both greater than 3.0. Through the analysis of the destruction process, the failure mode of the frame was researched. Plastic hinges were formed around the opening before the joints yielded, and the positions of the plastic hinges were a considerable distance from the beam-to-column joints. Damage to the structure was presented as a typical plastic hinge failure, which protected the beam-to-column nodes and avoided brittle failure.

A quantitative assessment of the model form error of friction models across different interface representations for jointed structures

Hysteretic models are widely used to model frictional interactions in joints to recreate experimental behavior. However, it is unclear which models are best suited for fitting or predicting the responses of structures. The present study evaluates 26 friction model/interface representation combinations to quantify the model form error. A Quasi-Static Modal Analysis approach (termed Rayleigh Quotient Nonlinear Modal Analysis) is adopted to calculate the nonlinear system response, and a Multi-Objective Optimization is solved to fit experimental data of the first mode of the Brake-Reuß Beam. Optimized parameters from the first mode are applied to the second and third bending modes to quantify the predictive ability of the models. Formulations for both tracing full hysteresis loops and recreating hysteresis loops from a single loading curve (Masing assumptions) are considered. Smoothly varying models applied to a five patch representation showed the highest flexibility (for fitting mode 1) and good predictive potential (for modes 2 and 3). For a second formulation, which uses 152 frictional elements to represent the interface, the physically motivated spring in series with a Coulomb slip model (elastic dry friction) has high error for fitting mode 1 and performs near the middle for predicting higher modes. For both interface representation, the best fit models are not the most physical, but rather the ones with the most parameters (as expected); however, the more physical models perform somewhat better for predicting the higher modes.

Geometric effects in cylindrical core/shell hard–soft exchange-coupled magnetic nanostructures

We explore the optimal condition for cylindrical core/shell hard-soft exchange-coupled magnetic nanostructures by obtaining full hysteresis loops for various geometries by obtaining full hysteresis loops for various geometrical variables, including the dimensional scale and soft/hard-magnetic phase volume ratio through micromagnetic simulations. For achieving maximum energy product (BH), it is essential to increase the demagnetizing field by increasing the volume fraction of the soft magnet while maintaining a positive nucleation field and, which can be possible by the scaling-down. To scale up the nanostructure to a bulk magnet having high BH can be achieved by forming an array of needle-shaped exchange-coupled cylinders. These findings could lead to the flexible design and scalable fabrication of exchange-coupled permanent magnets.

Magnetite-graphene oxide nanocomposites: Facile synthesis and characterization of optical and magnetic property

Graphene based magnetic nanocomposites provides promising applications for flexible transparent electronics due to increase in number of interfaces in nanocomposites which can provide better magnetic coupling. In this present work, magnetite-graphene oxide (MGO) and magnetite-reduced graphene oxide (MRGO) nanocomposites are synthesized with a homogeneous dispersion of Fe3O4 nanoparticles using a facile synthesis method i.e. co-precipitation and reduction processes at room temperature. UV–Visible and Fluorescence spectroscopy techniques are used to study the optical characteristics, while the structural, morphological and compositional characteristics are studied using X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Analysis (EDAX) techniques respectively. The magnetic hysteresis curves of MGO and MRGO are measured by the Vibrating Sample Magnetometer (VSM) system. The full hysteresis loop is obtained from −5 kOe to 5 kOe. Both MGO and MRGO nanocomposites have shown superparamagnetism at room temperature. The saturation magnetization obtained for MGO and MRGO is 3.45 emu/g and 3.92 emu/g respectively. Such nanocomposites can be used in graphene based environmental technologies.

Cyclic Testing of Bolt‐Weld Joints Reinforced by Sleeves Connecting Circular CFST Columns to Steel Beams

This study examined the design of joints reinforced by sleeves for connecting circular concrete‐filled steel tube columns to steel beams. Six half‐scale specimens, including four bolt‐weld joints reinforced by sleeves and two bolt and stiffened end‐plate joints, were designed and tested under cyclic loading to evaluate the seismic behavior of these joints. The joint construction and beam‐column stiffness ratio were taken as the main parameters in the tests. The seismic behaviors, including the failure modes, hysteretic curves, ductility, strength and stiffness degradation, and energy dissipation, were investigated. The experimental results showed that no obvious bolt loosening, fracture, or widespread weld cracking appeared in the joints reinforced by sleeves. Furthermore, the joint strength and stiffness were markedly increased by the sleeves in the joint core area. Overall, most specimens exhibited full hysteresis loops and excellent ductilities, the equivalent viscous damping coefficients were 0.263∼0.532, and the ductility coefficients were 1.77∼3.42. The interstory drift ratios satisfied the requirements specified by technical regulations. The connections of these types exhibit favorable energy dissipations and can be effectively utilized for building construction in earthquake‐prone areas. This research should contribute to the future engineering applications of concrete‐filled steel tube to composite structure.

Application of Magnetic Information Parameters for Nondestructive Testing of the Hardness of Medium-Carbon Alloy Steels

It is proposed that magnetic information parameters constructed from the parameters of the full magnetic hysteresis loop of steels be used for nondestructive testing of medium-carbon alloy steels. Analytic expressions for calculating the relative error in the determination of the magnetic information parameters are derived and analyzed. The measurement errors of the constituents of the parameters and the errors associated with the mathematical computations are taken into account. It is shown that the errors in the determination of the magnetic information parameters over the potential range of variation of the magnetic properties of steels is several-fold less than the relative error of the measurement of the relaxation magnetic parameters of steels. The use of the magnetic information parameters for nondestructive testing of the hardness of 40Kh steel in the range of hardness of practical importance is considered.

Bubble Magnetometry of Nanoparticle Heterogeneity and Interaction.

Bubbles have a rich history as transducers in particle-physics experiments. In a solid-state analogue, we use bubble domains in nanomagnetic films to measure magnetic nanoparticles. This technique can determine the magnetic orientation of a single nanoparticle in a fraction of a second and generate a full hysteresis loop in a few seconds. We achieve this high throughput by tuning the nanomagnetic properties of the films, including the Dzyaloshinskii-Moriya interaction, in an application of topological protection from the skyrmion state to a nanoparticle sensor. We develop the technique on nickel-iron nanorods and iron-oxide nanoparticles, which delineate a wide range of properties and applications. Bubble magnetometry enables precise statistical analysis of the magnetic hysteresis of dispersed nanoparticles, and direct measurement of a transition from superparamagnetic behavior as single nanoparticles to collective behavior in nanoscale agglomerates. These results demonstrate a practical capability for measuring the heterogeneity and interaction of magnetic nanoparticles.

Energy of dendritic avalanches in thin-film superconductors

A method for calculating stored magnetic energy in a thin superconducting film based on quantitative magneto-optical imaging is developed. Energy and magnetic moment are determined with these calculations for full hysteresis loops in a thin film of the superconductor NbN. Huge losses in energy are observed when dendritic avalanches occur. Magnetic energy, magnetic moment, sheet current and magnetic flux distributions, all extracted from the same calibrated magneto-optical images, are analyzed and discussed. Dissipated energy and the loss in moment when dendritic avalanches occur are related to each other. Calculating these losses for specific spatially-resolved flux avalanches is a great advantage, because of their unpredictable and non-reproducible nature. The relative losses in energy are much higher than the relative losses in moment.

Cyclic Testing of Concrete‐Filled Double‐Skin Steel Tubular Column to Steel Beam Joint with RC Slab

The design of composite joints for connecting concrete‐filled double‐skin tubular (CFDST) columns to steel beams supporting reinforced concrete (RC) slabs is presented in this paper. Five half‐scale specimens were designed, including four composite joints with RC slab and one bare steel beam joint, and were tested under a constant axially compressive force and lateral cyclic loading at the top end of the column to evaluate their seismic behavior. The main experimental parameters were the construction of the joint and the type of the column. The seismic behaviors, including the failure modes, hysteresis curves, ductility, strength and stiffness degradation, and energy dissipation, were investigated. The failure modes of the composite joints depended on the joint construction and on the stiffness ratio of beams to columns. Joints of stiffening type had significantly higher load‐bearing and deformation capacities than joints of nonstiffening type. Compared with the bare steel beam joint, the bearing capacities of the composite joints with RC slabs were markedly increased. The composite action was remarkable under sagging moments, resulting in larger deformation on the bottom flanges of the beams. Overall, most specimens exhibited full hysteresis loops, and the equivalent viscous damping coefficients were 0.282∼0.311. The interstory drift ratios satisfied the requirements specified by technical regulations. Composite connections of this type exhibit excellent ductility and favorable energy dissipation and can be effectively utilized in superhigh‐rise buildings erected in earthquake zones.

Seismic performance of recycled aggregate concrete–filled steel tube columns

In this study, low cyclic loading tests were performed on nine seamless steel tube columns filled with recycled aggregate concrete (RAC) and two steel tube columns filled with normal concrete to analyse their seismic performance and damage mechanism. The hysteresis behaviour, skeleton curve, ductility coefficient, stiffness degradation, and energy dissipation capacity of the steel tube columns were studied. The influence of the axial compressive ratio, steel strength, and steel thickness on the seismic performance of the steel tube columns was discussed. In addition, the failure mode and damage mechanism of the specimens were investigated; a skeleton curve–fitting formulation based on the Boltzmann mathematical model was proposed. A damage degree–based model was built for representing the damage degree quantitatively. The results indicate that the RAC-filled steel tube columns exhibit a full hysteresis loop, the equivalent coefficient of viscosity ranges from 0.402 to 0.572, and the coefficient of energy dissipation ranges from 2.617 to 3.595. The comparisons between the two types of steel tube columns indicate that the seismic performances of the RAC-filled steel tube columns are similar to those of the corresponding normal concrete–filled steel tube columns and that the RAC-filled steel tube columns even have appreciably better lateral bearing capacity, better ductility, and slightly lower energy dissipation ability at the same displacement level. These results consistently indicate that desirable seismic performance is achieved, and they serve as a potential reference for the structural design and application of RAC components in seismic areas.