Hysteretic Loops Research Articles

Entering Voltage Hysteresis in Phase-Separating Materials: Revealing the Electrochemical Signature of the Intraparticle Phase-Separated State.

Hysteresis is a general phenomenon regularly observed in various materials. Usually, hysteretic behavior is an intrinsic property that cannot be circumvented in the nonequilibrium operation of the system. Herein, it is shown that, at least with regard to the hysteretic behavior of phase-separating battery materials, it is possible to enter (deeply) the hysteretic loop at finite battery currents. This newly observed electric response of the electrode, which is inherent to phase-separating materials, is related to its microscopic origin arising from a (significant) share of the active material residing in an intraparticle phase-separated state. This intriguing observation is further generalized by revealing that a phase-separating material can feature (significantly) different chemical potentials at the same bulk lithiation level and temperature when exposed to the same finite current and external voltage hysteresis. Therefore, the intraparticle phase-separated state significantly affects the DC and AC characteristics of the battery. The experimental evidence for entering the intraparticle phase-separated state is supported by thermodynamic reasoning and advanced modeling. The current findings will help advance the understanding, control, diagnostics, and monitoring of batteries composed of phase-separating materials while also providing pertinent motivation for the enhancement of battery design and performance.

Effects of steel shim geometric characteristics and imperfections on the behavior of unbonded elastomeric bridge bearings subjected to large lateral displacements

Unbonded laminated elastomeric bridge bearings are designed to accommodate service-level deformations, but during an earthquake they can experience deformation demands that are significantly larger than those for which they were designed. Because these bearings are critical elements of a bridge, they must perform reliably even under seismic-level demands. The effects of the characteristics and condition of the steel shims on the seismic behavior of these bearings have received limited attention in the literature. Yet, the manufacturing process of these bearings sometimes introduces imperfections. For instance, during vulcanization, the steel shims might get rotated or bent. In this context, this paper investigates how manufacturing imperfections and the thickness characteristics of steel shims affect the behavior of unbonded elastomeric bridge bearings subjected to successive cycles of large lateral displacement. Finite element analysis is used to study the deformation pattern of these bearings, their hysteretic response characteristics, and the damageability of their steel shims. It is observed that imperfections can increase a bearing’s roll-off and risk of instability. Imperfections can also increase a bearing’s effective lateral stiffness and damage, quantified though a specific plastic-energy-based damage factor. Plastic damage in the shims is found to be appreciably dependent on their thickness. Under cyclic displacement, damage manifests itself more in the form of spreading of the yielded area rather than increased peak strain ductility. Plastic strains in the steel shims do not get close to the fracture limit, and all the bearings exhibit fairly stable hysteretic loops under the adopted loading protocol.

Quasi-static cyclic test on seismic performance of steel reinforced concrete frame with replaceable energy-dissipating member

In view of damage controlling and earthquake-resilient performance, the steel reinforced concrete (SRC) frame with replaceable energy-dissipating member (REDM) is proposed. The REDM is consisted of high damping concrete (HDC) wall panel and several fuses made by low yielding-point (LYP) steel. At first, low-cyclic reversed loading test on fuse is carried out to explore its shear capacity and hysteretic behavior. The suitable dimension and shape of fuse is determined for further study. Then the quasi-static cyclic test considering two loading patterns is applied on two SRC-REDMs. One specimen is loaded until overall failure while another is repaired by installing a new set of REDM during the loading history. The analyses and comparisons are conducted in terms of failure mode, yielding pattern, hysteretic characteristics, stress distribution, stiffness degradation, dynamic characteristics, ductility and energy dissipation. The failure mode is summarized as bending-shear failure of the wall panel, local buckling of fuses and beam hinge failure mechanism of SRC frame. The hysteretic loops are plump while large energy dissipation capacity is represented. The seismic performance is verified by high bearing capacity and ductility. The bearing capacity and stiffness of repaired specimen is significantly rehabilitated. The new REDM has dissipated much more hysteresis energy than that of non-repairing case. The earthquake-resilient behavior is confirmed by the significant recovery in mechanical properties.

Seismic behavior of steel beam-column connection with assembled steel rod energy dissipaters

The exorbitant expenses associated with the post-earthquake rehabilitation of the primary structure has been addressing the importance of a resilient building that exhibit easy and cheap repairability. To achieve a resilient building structure, a feasible way is to localize the plastic damages in preselected structural fuses which can be easily replaced. In doing so, a novel energy-dissipative steel beam-column connection incorporating the assembled steel rod energy dissipaters (ASREDs) was proposed in this paper. Firstly, the moment-resistant capacity and the rotational stiffness was theoretically derived based on a simplified mechanical-based method and the component method, respectively. Then, cyclic tests on four specimens were conducted to investigate the cyclic and recovery performance of the connection. The influences of the quantity, location, and geometrical details of the ASREDs on the performance of the connection were evaluated. The considered connection performance indexes included strength, deformability, and energy dissipation capacity. Test results showed that the proposed connections efficiently protected the primary structural members of the steel frame, i.e., beams and columns, by restricting the plastic damage within the core rod of the ASREDs. The obtained hysteretic loops were stable and plump, whereas the strength degradation was not observed until the rotation of the beam-column connection exceeded 0.03. The damaged connection was easily repaired by replacing failed ASREDs. The repaired connection exhibited identical performance with the original one. Finally, numerical models accounting for the ductile damage of ASREDs were established to reproduce the test results and to enrich the experimental database. Results showed that the numerical model could simulate the seismic behavior of connections with reasonable accuracy, and the analytical methods for predicting the performance of the connections were validated against both experimental tests and numerical simulations.

Experimental analysis of a full-scale steel frame with replaceable dissipative connections

This work presents the experimental campaign performed on a full-scale 6-storey steel concentrically braced frame equipped with the so-called Dissipative Replaceable Braced Connection (DRBrC) made with plates of mild steel and high-strength steel. Such component, constituting the brace-column joint, is capable of dissipating large amounts of energy through wide hysteretic loops, while providing the possibility of being easily replaced after the building undergoes medium-high intensity earthquakes. To reduce the costs and, at the same time to obtain a representative response of the full frame, hybrid simulation tests were employed, in which only the ground floor was physically built in the laboratory. In contrast, the remainder of the structure was numerically simulated. The innovative frame was subjected to three different natural ground motions at the Damage Limitation (DL), Significant Damage (SD) and Near Collapse (NC) limit states, respectively. The outcomes highlighted the high potential of the DRBrC component in dissipating large amounts of energy and, at the same time, in protecting the remaining parts of the structure, by exhibiting very small residual displacements that enhance self-centring and repairability capabilities. Moreover, the numerical models were calibrated by including the non-negligible effect introduced by the bolt-hole clearances. All results are thoroughly described in the manuscript.

Development and seismic behavior of an assembly composite damping self‐centering brace

AbstractA new type of assembly composite damping self‐centering brace is proposed to simplify the configuration, reduce the manufacturing cost, and improve its energy dissipation capacity, which is assembled by several modules in parallel with different functions. A brace specimen with a total length of 1.843 m was designed and numerically analyzed. The brace exhibits stable and full flag‐shaped hysteretic responses, and dissipates adequate energy during cyclic motion, with a high bearing capacity. When the brace is unloaded, the viscous damping force disappears, and the residual displacement can be basically eliminated. The hysteretic envelope area increases with the increase in loading frequency. When the frequency is 0.5 Hz and the target displacement is 30 mm, the activation force, ultimate bearing capacity, residual displacement, energy dissipation during one cycle, and equivalent viscous damping ratio are 622.5 kN, 1018.7 kN, 9.11 mm, 41.10 kJ, and 0.214, respectively. Under random loading, the damping force provided by the viscous module ensures a fuller hysteretic loop than the existing displacement‐type energy dissipation self‐centering brace. The influences of design parameters on the hysteretic performances of the brace were studied. When the disc spring stiffness increases from 3.27 to 9.80 kN/mm, the ultimate bearing capacity, residual displacement, and equivalent viscous damping ratio change by 18%, −24%, and −15%, respectively. The viscous damping coefficient and flow index of the viscous module should be increased, and the prepressed force and stiffness of disc springs in recentering module should also be appropriately increased.

Use of silicon rubber as a viscoelastic material in dampers

One of the most extensively utilized structural control devices is the viscoelastic damper (VD), and significant study has gone into enhancing their efficiency in structures. The mechanical response of a VD supplied with silicone rubber as viscoelastic material (SRD) under various loading conditions is investigated in this research. A conventional VD is the SRD, which is made up of dual layers of rubber mounted between three steel plates. A total of two specimens were produced. To evaluate the influence of strain amplitude and excitation frequency on the mechanical characteristics of SRD, each damper was exposed to harmonic loading with different values. Hysteretic loops for each loading case were extracted, and the variations of several mechanical parameters with the variated loading conditions were inspected. The results indicate that SRD has a high energy dissipation capacity, and has stable performance under different working conditions. Finally, a proper simplified element model was created using SAP2000 software to evaluate the dissipation characteristics and control impact of the SRD in structures, and then a time history analysis was executed on multi storey structure. Due to the obvious dampers’ extra stiffness and efficient damping property, the control impact of the SRD dampers on structural displacement is preferred and reflected on reducing the excessive displacement due to structure movement, according to data obtained.

A novel bi-directional rail variable friction pendulum-tuned mass damper (BRVFP-TMD)

The shape of hysteretic loops for a friction pendulum system transforms when excited by bi-directional motion, which exhibits unexpected dynamic behavior compared with unidirectional motion. Therefore, a novel bidirectional rail variable friction pendulum-tuned mass damper (BRVFP-TMD) with two independent rails that satisfied the purpose of bidirectional structural response control and provided a full bidirectional friction force was proposed. The variable friction arrangement was applied to the rails so that the BRVFP-TMD could be accomplished with a linear hysteretic damping property that is contributed by the displacement-dependent variable friction force. Using unidirectional harmonic excitations with attack angle as bi-directional loading, illustrations were created to investigate the control effect of traditional pendulum friction TMDs with a spherical sliding surface. This demonstrated the collapse of hysteretic loops of traditional pendulum friction TMDs and superiority of BRVFP-TMD in terms of mechanism. For the BRVFP-TMD with a lightly damped structure, the optimizations of the fixed-point theory were accessed to obtain the closed-form solutions of the optimal parameters of the BRVFP-TMD. Numerical verifications based on bidirectional motions were conducted to evaluate the performance of the BRVFP-TMD. The bidirectional earthquake results indicated stable and excellent performance of the BRVFP-TMD in terms of either frequency response reduction or friction energy dissipation efficiency. Meanwhile, bidirectional wind-induced vibrations confirmed the correctness of the optimization and the stable robustness of the optimized BRVFP-TMD.

Experimental Investigation of Seismic Performance of Precast Concrete Wall-Beam-Slab Joints with Overlapping U-Bar Loop Connections.

In the era of energy conservation and environmental protection, as well as the industrialization of buildings, precast concrete (PC) structures have been developed and increasingly applied in construction industries due to their advantages of outstanding workability and ecofriendliness. In order to verify the reliability of overlapping U-bar loop connections and a modified form of these connections, and study the seismic performance of PC wall-beam-slab joints with these connection methods, three full-scale wall-beam-slab joints were designed and tested under low reversed cyclic loading, including one cast-in-place (CIP) specimen and two PC specimens. Based on the test results, the seismic performance of the PC joints was studied by comparing their damage process, hysteretic loops and skeleton curves, load-carrying capacity, ductility, equivalent stiffness, and energy dissipation with those of the CIP joint. After analyzing the experimental results, the following conclusions can be drawn: the overlapping U-bar loop connection and its modified form are effective and reasonable; the specimen with the modified connection form showed slightly better mechanical properties; the failure mode of the PC joints was consistent with that of the CIP joint; and the generation, distribution, and development of cracks in the PC specimens were similar to those in the CIP specimen. In addition, the stiffness of the PC joints was similar to that of the CIP joint, and the load-carrying capacity, ductility, and energy dissipation of the PC joints were better than those of the CIP joint. Moreover, the research in this paper can also provide some guidance for assembling wall-beam-slab joints in PC shear wall structures.

Capacity gradients and capacity fragility of code-conforming RC frame joints based on pseudo-static tests

The design objectives of code provisions usually lack validations. This study aims to make clear the constitutive relations, capacity gradients and probability assurance of beam-column joints following Chinese seismic code based on pseudo-static tests. Twelve joint specimens are made in 1:1.5 large scale and grouped by fortification levels, exterior - interior locations, and middle – bottom stories. Loadings and measurements at beam ends were transformed to moment-rotation relations of joints; measurements at reinforcements and joint cores helped to confirm the dominance of bending failure and the independence of joints’ strength to locations. Thus, by summarizing the statistic properties of the hysteretic loops and backbone curves, beam hinge models were extracted; by including measurements at different wings and inserting test-unavailable points through regression relations, sample numbers were enlarged; by introducing randomness to earthquake actions, the fragility curves were obtained. Results showed that, the capacity gradients between columns and beams set by code are realized, but gradients between fortification levels aren’t; higher fortification does not help to improve the post-yielding performance; 8° external joints have the highest probability assurance, and then the internal 7° joints.

Seismic behavior of composite shear walls with boundary columns using rectangular and U-shaped concrete-filled steel tubes

Steel-concrete composite shear walls with boundary concrete-filled steel tube (CFST) columns have drawn the attention of researchers due to their good seismic performance such as high strength, ductility and energy dissipation capacity. The reported study proposes a novel composite shear wall design that aims to complete the majority of the work in the factory, leaving only concrete pouring, steel welding, and formwork removal to be done on-site, so that the constructional time and cost can be saved. Two types of CFSTs were used for the boundary columns of composite shear walls, one is conventional rectangular CFSTs, another one is U-shaped CFSTs. In order to study the seismic behavior of the novel composite shear walls, cyclic loading tests were conducted on four full-scale specimens. The bearing capacity, energy dissipation, skeleton curves, hysteretic loops, deformation capacity and failure mode are analyzed. The experimental results have demonstrated that the bearing capacity and stiffness of shear walls with U-shaped CFST columns are slightly higher than that of shear walls with rectangular CFST columns, whereas the latter has better deformation capacity. In addition, the reported study investigated the methods of calculating the shear capacity of the novel composite shear walls and provided recommendations on the calculation method to be used for design and structural analysis.

Seismic Behavior of Through-tenon Joints with Loose Gap

In this paper, the dry shrinkage deformation of through-tenon joints (TTJs) is simulated by reducing the height of tenon to produce a gap between tenon and mortise. The seismic behaviors of TTJS such as the failure characteristics, hysteretic loops, skeleton curves, degradation of rigidity and energy dissipation were studied through low-cycle reversed loading experiment on 2 groups of TTJs with different degrees of dry shrinkage and sizes. The results indicate that the shape of hysteretic loops of all joints are Z shaped and the gathering effect gets more obvious with the increase of loose degree. The dry shrinkage deformation of TTJs will weaken the seismic performance of the specimens, with the energy dissipation capacity of the joint decreases with the increase of dry shrinkage deformation, and the energy dissipation capacity will be significantly weakened when the gap between the mortise and tenon increases slightly, for example, the energy dissipation capacity of the specimen will be weakened to 50% that of the intact specimen when the gap value increases to 3% height of the mortise.

Ultra-low cycle fatigue life prediction of assembled steel rod energy dissipaters with calibrated ductile fracture models

In recent decades, various bar-typed miniature energy dissipaters with buckling restrained mechanisms have been proposed for seismic mitigation of engineering structures. The recently proposed assembled steel rod energy dissipater (ASRED), incorporating equally divided tubes as filler components, have shown plump hysteretic loops and remarkable fatigue performance. For such miniature dissipaters with varied dimensions, its ultra-low-cycle fatigue (ULCF) life is correlated with the geometrical dimensions. However, no research concerning this issue has been found. To enable the fracture prediction of ASREDs under various loading situations, numerical models integrated with the ductile fracture model were established in this paper. A newly proposed constitutive model and the famous combined hardening model were both employed in the numerical models to comparatively investigate the key factors affecting the accuracy of the fracture prediction. Moreover, the possible influence of Lode angle was also investigated by employing two different ductile fracture models, namely, the cyclic Bai-Wierzbicki model (CBWM) and the cyclic void growth model (CVGM). Seven specimens with different lengths and loading protocols were simulated, and the results show that the strain amplitude distributes unevenly in the ASRED and increases cycle by cycle at the fixed ends, which leads to the necking-induced failure mode. Using the fracture model of CBWM, numerical simulations that considers the influence of strain amplitude could successfully predict the fracture of all specimens. The dissipaters behaved approximately in an axially loaded state throughout the entire fatigue life, therefore the influence of the Lode angle was negligible, and the fracture predictions given by the CVGM are same with that by the CBWM. Based on a comprehensive analysis of the extended numerical investigations, an improved configuration for ASRED is proposed.

Fatigue behaviour analysis of aluminium alloy riveted single-shear lap joints

Analysing the dynamic response, the fatigue failure process of aluminium alloy riveted single-shear lap joints is quantitatively described. Firstly, numerical analysis of hysteretic loops based on MATLAB is proposed, and cyclic relative displacement amplitude, stiffness and dissipated energy are calculated. Secondly, the service behaviour corresponding to the evolution of relative displacement amplitude and dissipated energy is analysed and verified by finite element simulation. Finally, based on the evolution of cyclic compression stiffness, the cycles corresponding to crack initiation, as well as slow and rapid propagation, are calculated and verified by observing crack growth propagation through interruption tests.

Hysteretic energy damage coupled elastoplastic constitutive model and its application to low-cycle fatigue life prediction of martensitic steel

The microstructure of martensitic steel is analyzed by transmission electron microscopy and X-ray diffraction. The low-cycle fatigue (LCF) test of martensitic steel with different strain amplitudes is carried out by MTS universal hydraulic servo testing machine. The damage accumulation and cyclic elastic-plastic constitutive model of martensitic steel are studied. The influence of tempering on hysteretic loop and fatigue damage is discussed. With the tempering temperature increasing, the area of hysteresis loop increase, the hysteresis energy increases, and the fatigue life decreases. According to the fatigue damage accumulation model of the hysteresis energy method, an improved kinematic and isotropic composite hardening model is proposed in tempering temperature. This model is used to simulate the LCF behavior before fracture under LCF load and to predict the fatigue life with the variation of applied strain amplitude and tempering temperature. The verification results show that the modified model can well describe the phenomenon of acceleration of cyclic softening and great reduction of cyclic stress.

Hysteretic behavior of SMA energy dissipater with shape memory effect induced by heating recovery

The buckling restrained energy dissipater is one small axial yield type energy dissipation device usually attached to the prefabricated structure to improve seismic performance. In this paper, a shape memory alloy bamboo-shaped energy dissipater (SMA-BED) was proposed, which used bamboo-shaped SMA rod as the energy dissipation core. The special shape memory effect of SMA material was expected to recover the residual deformation, and the outer restraining tube was used to prevent the core buckling and instability. The tests of 8 SMA-BED specimens were completed to compare the effect of repeated loadings on hysteretic behavior. The results showed that all specimens exhibited stable and full hysteretic loops. After loading, the average deformation recovery ratio of all specimens was about 97.9% by heating in a water bath and cooling to room temperature. The load-displacement curve obtained by reloading the specimen basically coincided with the previous curve, and the results were consistent after repeated 3 loading times. The compression and deformation modes of the SMA-BED core with different construction forms were analyzed theoretically, meanwhile a lateral displacement computation model of the yielding part was proposed, which could better estimate the contact between yielding part and restraining tube.

Parametric studies and design recommendations for assembled steel rod energy dissipaters

A recently proposed assembled steel rod energy dissipater (ASRED) has been demonstrated to have distinctive hysteretic behavior and satisfactory low-cycle fatigue performance for mitigating seismic effects by experimental tests. However, design recommendations and fatigue model for the ASRED have not been established, thus hindering its practical applications in earthquake-resistant engineering structures. To solve this dilemma, parametric analysis via calibrated numerical models was carried out in this paper. Numerical models were reinforced by the newly proposed cyclic constitutive model and the cyclic Bai-Wierzbicki ductile model (CBWM) to enable high-fidelity simulations on the full-life hysteretic behavior of the energy dissipaters. Four key design parameters including the length of dissipation segment, clearance size, friction coefficient, and the length of middle stopper, which generate 54 cases in total, were considered in the parametric studies. The influences of these parameters on the hysteretic behavior of an ASRED were comprehensively analyzed. It was found that increasing the dissipation segment length and friction coefficient would impair the fatigue life and increase the cyclic hardening rate of the energy dissipater. Comparatively, an increased stopper length had no influence on the cyclic curves and the fatigue life. Besides, an excessive clearance size would cause pitching effects and tensile strength deterioration of the hysteretic loops. Based on the numerical results, the optimal stopper length for an ASRED with a diameter of, say, 18 mm, is 20 mm, and the corresponding clearance size should be no larger than 1.5 mm. Moreover, the length-diameter ratio and the clearance-diameter ratio are identified as the key parameters to affect the deformation nonuniformity of the energy dissipater. Finally, a design-orientated fatigue model was proposed to predict the fatigue life of the ASRED with varied yield strength and length.

Analysis of the Seismic Performance of a Masonry Structure with RC Frames on the First Story with Concrete-Filled Steel Tubular Dampers

The concrete shear walls of masonry structures with RC frames on the first story are low-rise shear walls with a height–width ratio of less than 1. The strength, stiffness, and ductility of these low-rise shear walls are not matched, resulting in poor seismic performance. Based on the idea of the passive control theory and multi-seismic defensive lines, the scheme of a masonry structure with RC frames on the first story with a concrete-filled steel tubular (CFST) dampers is proposed in this paper. To explore the seismic mitigation effect of CFST dampers applied to a masonry structure with RC frames on the first story, the seismic performance under low-reversed cyclic loading of the frame with the CFST dampers is first compared with that of the energy-dissipated low-rise concrete shear wall proposed by previous researchers and the ordinary low-rise concrete shear wall. Furthermore, the response of the masonry structure model with RC frames on the first story with CFST dampers and two other comparative structural models under earthquake action are discussed. The results show that a masonry structure with RC frames on the first story with CFST dampers has a fuller hysteretic loop, lighter pinching, better energy dissipation ability, and better seismic performance. Compared with the other two structures, the energy dissipation capacity of the masonry structure with RC frames on the first story with CFST dampers is significantly improved, by 1.25~1.5 times. The amplification effect of the deformation angle allows the CFST dampers to play a significant role in energy dissipation, whereas the main structure still undergoes a small deformation. The CFST dampers can dissipate more seismic energy to protect the main structure from damage and improve the seismic performance of masonry structures with RC frames on the first story.

Mechanical Behaviors of a Buckling-Plate Self-Centering Friction Damper

In order to improve the resilience of structures subjected to strong earthquakes, a buckling-plate self-centering friction damper (BPSCFD) with low post-yielding stiffness is proposed, which consists of a group of post-buckling plates and a self-centering variable friction mechanism. The damper is intended to not only reduce the peak and residual deformation of structures, but also to limit the additional internal force of the structural elements. Through theoretical derivation and finite element simulation, the hysteretic damping and self-centering characteristics of BPSCFDs are studied. In order to examine the seismic performance of the BPSCFDs, the dampers are employed to retrofit a double-columns bridge bent, and the corresponding elastic-plastic time history analysis is conducted. The results show that the force-displacement relationships of BPSCFDs with different parameter combinations are characterized by typical flag-shaped self-centering hysteretic loops and low post-yielding stiffness, and the dampers can effectively reduce the peak and residual deformation of the bridge bent without increasing the peak acceleration and base shear. The research results could supply a guideline for the design and application of the damper.

A quasi-zero-stiffness elastic metamaterial for energy absorption and shock attenuation

A multi-step quasi-zero-stiffness metamaterial (MS-QZSM) is proposed, which exhibits potential applications in various engineering scenarios, such as multi-vibration mitigation and mechanical protection. At the level of the cell, the MS-QZSM is characterized by the elastic ring connected in parallel with two cross-curved beams respectively, which exhibits multiple deformation behaviors and quasi-zero-stiffness phases (force plateaus) under global compression load. Whithin the line elastic range of material, the proposed metamaterial can achieve QZS region. The multi-step QZS features of the MS-QZSM are theoretically analyzed, and validated by experiments and numerical calculations. Furtherly, the MS-QZSM performances of multiple deformation behavior and energy absorption are investigated by loading–unloading compressive experiments and simulations. Experiment results are in agreement with the simulation results, which show that there are two force plateaus and an obvious hysteretic loop. MS-QZSM has no structural damage during deformation, but plastic deformation occurs. In the area of multi-vibration mitigation and mechanical protection, the findings of this study can expand application prospects of metamaterial in engineering structures.