Full Hysteresis Research Articles

Seismic behavior evaluation of friction-bearing type connection with slit dampers

Ductility-based design for structural collapse prevention may not be sufficient for the higher performance demand of minimizing the time and cost for function recovery. A friction-bearing type connection with slit dampers was introduced to the beam system at the beam end, and it followed the characteristics of the damage-controlled type connection. The design considerations for the proposed connection were presented and the experimental investigation on the cyclic behavior of the designed specimens was conducted. The results demonstrated that the designed connection exhibited a stable and full hysteresis behavior under cyclic loading, without obvious performance degradation. With a longer slotted hole in the slit damper, the friction-slipping behavior was obvious and the maximum rotation angle could be up to 0.05 rad, while the bearing capacity was enhanced with a shorter slotted hole. The friction-slipping behavior also improved the stress development of main structural members and enhanced the ductile behavior. The proposed connection could develop two-stage energy dissipation behavior, and the frictional slippage was greatly helpful for dissipating energy. The damage concentration was achieved, and the energy dissipated by the proposed connection accounted for more than 75 % of the total dissipated energy. The the inelastic deformation was mainly concentrated in the slit damper, while the beam and the column remained elastic, greatly improving the seismic resilience.

Wind-induced vibration and control of truss string structures subjected to thunderstorm downbursts

This study investigates the wind-induced vibration response of TSSs under thunderstorm downbursts and introduces self-centering braces to analyze the vibration control. The study reveals that the vertical peak displacement of the upper chord nodes exhibits a “V” shaped distribution along the span direction, while the vertical residual displacement follows an “S” shaped distribution. The wind-induced vibration response at the cantilevered end is much stronger, and after the introduction of self-centering braces, the wind-induced vibration response significantly decreases, indicating that the self-centering braces play a noticeable role in controlling wind vibration. Additionally, the cable forces of the TSS significantly decrease under thunderstorm downbursts, with a loss of about 68%. The residual cable forces are uniformly distributed for the original structure and show a minor correlation with cable locations, whereas the residual cable forces of the structure with self-centering braces have a higher correlation with the cable locations. The residual cable force is significantly reduced after installing the self-centering braces, with a maximum reduction of 57.22%. Furthermore, the self-centering braces have a full hysteresis curve under thunderstorm downbursts, which indicates that it has high energy dissipation capacity and a good self-centering effect, which is conducive to controlling the wind vibration response of the structure under thunderstorm downbursts.

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.

Fiscal Supermultiplier and Endogenous Money in the United States: The COVID-19 Pandemic vs. the Global Financial Crisis

ABSTRACT The paper examines different real-monetary dynamics and policy responses during the COVID-19 pandemic (C19P) and the Global Financial Crisis (GFC) in the United States through the lens of the Sraffian Supermultiplier model and the endogenous money approach. On the one hand, the C19P triggered a relatively deeper contraction in GDP, but its recovery was relatively faster and more robust. The ‘V’ shaped recovery from the C19P significantly contrasted the ‘L’ shaped trajectory of the post-GFC period. On the other hand, the money supply (M2) grew relatively more, and the monetary base expanded relatively less during the C19P. To explain these different real-monetary dynamics, a theoretical framework is developed and analyzed empirically for the United States. The theoretical model and the empirical analysis suggest that money supply is endogenously determined by creditworthy demand derived from the multiplier-accelerator effect of non-capacity generating autonomous demand, in which government spending plays a key role. Therefore, the absence of full hysteresis after the C19P shock had nothing to do with a traditional neoclassical trend reversal mechanism but with the fiscal supermultiplier effect of the extraordinary pandemic-related government spending.

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 study on the seismic performance of concrete-filled steel tube columns with a multiple-chamber round-ended cross-section

Reinforced concrete bridge piers with round-ended sections are susceptible to bending, bending–shear, and shear failure after earthquakes in high-intensity areas, thus necessitating improved seismic performance. This study introduced a novel design for a concrete-filled steel tube (CFST) column, featuring a multi-chambered, round-ended cross-section. The use of longitudinal and transverse stiffeners divided the column section into distinct chambers, thereby enhancing the seismic performance of the columns. A total of 12 groups of static tests were performed to examine the effect of chamber layout, axial compression ratio, and aspect ratio on columns’ hysteresis behavior, and the hysteresis curves, skeleton curves, failure modes, stiffness degradation, ductility, and energy dissipation capacity were obtained. Results demonstrated the favorable seismic performance of composite columns. Additionally, an increase in chambers led to a full hysteresis curve, enhancing bearing and energy dissipation capacities. The displacement ductility coefficient (μ) ranged between 3.88 and 7.45, and the design parameters have minimal influence on the stiffness degradation of the composite beam. Based on the results, the long and short sides of the CFST columns with a large length–width ratio should be arranged to be relatively close in length.

Shaking-Table Test and Finite Element Simulation of a Novel Friction Energy-Dissipating Braced Frame

To enhance the effect of seismic mitigation in medium-sized buildings, this study introduced a novel friction damper within a braced frame, forming a friction energy-dissipating braced frame (FDBF). The seismic reduction mechanism of the FDBF was examined, and its performance was evaluated through shaking-table tests and finite element simulations. The hysteresis performance of the novel damper was assessed through low-cycle repeated loading tests, which yielded predominantly rectangular and full hysteresis curves, exemplifying robust energy dissipation capacity. The shaking-table tests of the FDBF indicated significant modifications in the dynamic characteristics of the original frame structure, which notably reduced the natural vibration period and enhanced the damping. Additionally, the FDBF remarkably reduced both acceleration and displacement responses during seismic excitation. Optimizing the orientation of the energy dissipation brace significantly improved seismic reduction efficiency. A dynamic time history analysis, employing finite element software, was conducted on the FDBF equipped with a friction energy dissipation brace at each level. Comparative analysis with both the moment-resistant frame and ordinary braced frame revealed that the FDBF substantially lowered the peak acceleration at the apex of the structure, achieving a reduction rate of 40–50%. Under both design and rare earthquake conditions, the FDBF demonstrated superior seismic mitigation capabilities, especially under rare earthquakes. Future studies should investigate various structural types with energy dissipation braces at different levels to identify the most efficient layout for the novel friction energy dissipation brace, thereby guiding relevant engineering practices.

Experimental tests and numerical simulations of miniature buckling-restrained braces using iron-shape memory alloy bar

Miniature buckling-restrained braces (BRBs) have a concise configuration and clear working mechanism. Owing to stable and full hysteresis, miniature BRBs are emerging as favorable energy-dissipating fuse elements in seismic applications. This paper proposes using iron-shape memory alloy (FeSMA) in lieu of conventional steel as the yielding core and focuses on the cyclic behavior. Four specimens, corresponding to four loading protocols, were fabricated and tested. According to experimental data, the miniature FeSMA BRBs exhibited full hysteresis, which is characterized by large damping, noticeable isotropic and kinematic hardening behavior and appreciable post-yield stiffness ratio. The cumulative plastic deformations meet the requirement by ANSI/AISC 341-16. Further, high fidelity finite element models, which explicitly considered damage and fracture rules, were established for numerical simulations. Good agreement can be found between the experimental data and numerical simulations, in terms of failure modes, fracture locations and global hysteresis.

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.

Experimental study and constitutive modelling of wire arc additively manufactured steel under cyclic loading

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

Seismic Behavior of T-Shaped Concrete-Filled Steel Tubular Column to Steel Beam Joints with Side Plates

This study investigates the seismic behavior of the T-shaped concrete-filled steel tubular (CFST) column to steel beam joints, aimed at expanding their applicability in areas with high-seismic fortification intensity. A construction form of T-shaped CFST column to steel beam joint with side plates is presented. The variables studied in these experiments include the side plate length, the axial compression ratio, the presence of side plates, and the presence of binding bars. The force mechanism, failure modes, load–displacement curves, strength, stiffness, ductility, and energy dissipation capacity of seven specimens were evaluated under low-cycle reciprocating load. The experimental results demonstrate that the joints of side plates show a full hysteresis curve, with the ductility coefficient ranging from 1.67 to 2.49, and the equivalent viscous damping coefficient between 0.147 and 0.234. The joint panel zone displays strong deformation and energy dissipation capacity. The inclusion of side plates and binding bars improves the seismic behavior of the joint. The setting of side plates enables the formation of a plastic hinge on the steel beam, creating a beam hinge failure mechanism and satisfying the seismic design principle of “strong column and weak beam, strong joint and weak member” as required by the building structures.

Screening-current-induced magnetic fields and strains in a compact REBCO coil in self field and background field

REBa2Cu3O7−x (REBCO) coated conductors, owing to its high tensile strength and current-carrying ability in a background field, are widely regarded a promising candidate in high-field applications. Despite the great potentials, recent studies have highlighted the challenges posed by screening currents, which are featured by a highly nonuniform current distribution in the superconducting layer. In this paper, we report a comprehensive study on the behaviors of screening currents in a compact REBCO coil, specifically the screening-current-induced magnetic fields and strains. Experiments were carried out in the self-generated magnetic field and a background field, respectively. In the self-field condition, the full hysteresis of the magnetic field was obtained by applying current sweeps with repeatedly reversed polarity, as the nominal center field reached 9.17 T with a maximum peak current of 350 A. In a background field of 23.15 T, the insert coil generated a center field of 4.17 T with an applied current of 170 A. Ultimately, a total center field of 32.58 T was achieved before quench. Both the sequential model and the coupled model considering the perpendicular field modification due to conductor deformation are applied. The comparative study shows that, for this coil, the electromagnetic–mechanical coupling plays a trivial role in self-field conditions up to 9 T. In contrast, with a high axial field dominated by the background field, the coupling effect has a stronger influence on the predicted current and strain distributions. Further discussions regarding the role of background field on the strains in the insert suggest potential design strategies to maximize the total center field.

Asymmetry of AMOC Hysteresis in a State‐Of‐The‐Art Global Climate Model

AbstractWe study hysteresis properties of the Atlantic Meridional Overturning Circulation (AMOC) under a slowly‐varying North Atlantic (20°N–50°N) freshwater flux forcing in state‐of‐the‐art global climate model (GCM), the Community Earth System Model. Results are presented of a full hysteresis simulation (4,400 model years) and show that there is a hysteresis width of about 0.4 Sv. This demonstrates that an AMOC collapse and recovery do not only occur in conceptual and idealized climate models, but also in a state‐of‐the‐art GCM. The AMOC recovery is about a factor six faster than the AMOC collapse and this asymmetry is due to the major effect of the North Atlantic sea‐ice distribution on the AMOC recovery. The results have implications for projections of possible future AMOC behavior and for explaining relatively rapid climate transitions in the geological past.

Probabilistic residual displacement-based design for enhancing seismic resilience of BRBFs using self-centering braces

Buckling-restrained braces (BRBs) can effectively control the structural maximum displacements. However, their full hysteresis tends to cause significant residual drifts after strong earthquakes, resulting in massive economic loss. To improve the resilience of the buckling-restrained braced frames (BRBFs) by reducing the residual drifts, self-centering braces (SCBs) are introduced to BRBFs based on the probabilistic residual displacement-based design (PRDBD) method in this study. Parametric analyses are first carried out on single-degree-of-freedom (SDOF) systems to represent the retrofitted BRBFs subjected to near-fault pulse-like earthquakes, wherein the isotropic strain hardening of BRBs is considered. The probabilistic prediction models for maximum and residual displacement are subsequently developed by employing an artificial neural network (ANN) machine learning algorithm. Subsequently, the PRDBD method is proposed. A benchmark BRBF is retrofitted by SCBs to demonstrate the PRDBD’s effectiveness. System-level nonlinear time-history analyses (THAs) are performed to study the dynamic performance of the enhanced BRBFs. It can be observed from the analysis results that the proposed PRDBD is efficient in controlling residual displacements of the enhanced BRBFs within the prescribed guarantee rate. Moreover, the analysis results confirm that the retrofitted BRBF with partial self-centering behavior can achieve remarkable post-earthquake repairability, as evidenced by residual inter-story drifts below 0.5% with 99% probability subjected to the maximum considered earthquakes.

Study on seismic performance of an innovative single-tube self-centering buckling-restrained brace

To simplify the construction of traditional self-centering buckling-restrained braces (SC-BRBs) and achieve efficient recovery function, an innovative type of single-tube self-centering buckling-restrained braces (ST-SC-BRBs) is proposed. The ST-SC-BRBs only require one outer tube for the prestressed system. The detailed structure and working principle of the ST-SC-BRBs are described, and it is emphasized that the restrained steel tube should be checked as a compression-bending member to ensure its overall stability. Low-cycle fatigue tests are conducted on scaled models of one traditional BRB and two ST-SC-BRBs. The results show that the residual deformation of the ST-SC-BRBs is significantly reduced compared to that of the traditional BRB, with comparable energy dissipation capacity. The ST-SC-BRB works stably with a full hysteresis curve and an obvious “flag-shaped” pattern within the inter-story drift ratio of 2%. The self-centering ratio is the key factor affecting the recovery effect of the ST-SC-BRB. To achieve smaller residual deformation, the self-centering ratio is suggested to be greater than 1. Overall, the ST-SC-BRB presents a more simplified and effective approach to constructing a recoverable functional structure.

Transformer modelling considering power losses using an inverse Jiles-Atherton approach

Power transformers are devices with non-linear behavior due to the saturation of the ferromagnetic core. When modelling such devices, the saturation effect must be taken into account because it greatly affects their performance and efficiency. In this paper, an electromagnetic model for power transformers is proposed and experimentally validated using an electrical T-model coupled with a reluctance network to model the magnetic part. The electrical circuit and the reluctance network are linked by two B–H approaches. The B–H relationships are modelled by the full hysteresis cycle based on the inverse Jiles-Atherton theory and by the initial magnetization curve. The results obtained with the inverse Jiles-Atherton theory model reproduce the magnetic core behavior with more accuracy than the one based on the initial magnetization curve, especially at low load conditions where saturation plays a more prominent role on the no-load current. The proposed model can be applied to other magnetic devices such as inductors for power electronic applications or electromechanical relays, among others.

Experimental analysis on the structural seismic behavior of steel frame-precast steel reinforced concrete (SRC) infill wall with lateral force resisting

The structural seismic performance of steel frame-precast steel reinforced concrete (SRC) infill wall with lateral force resisting is analyzed, and the structural strength of steel frame-precast SRC infill wall with lateral force resisting is improved. The structural seismic performance optimization model of SRC lateral force resisting wall based on buckling restrained brace is proposed. Through the finite element simulation software, the seismic performance and response results of ordinary steel frames, buckling restrained braced steel frames and a relatively new type of sacrificial-energy dissipation braced steel frames under earthquake are compared and analyzed to demonstrate the applicability and performance advantages of sacrificial-energy dissipation braced steel frames in the steel frame braced structure system. Under the action of horizontal earthquake, the supporting members experience reciprocating axial tension and compression cycles, which dissipate a large amount of seismic energy input into the structure. Therefore, the buckling restraint support method can be used in the structure to improve the support strength. Under horizontal reciprocating load action of earthquake, the ability to consume seismic energy through self-hysteresis of the brace is poor. Experimental research shows that, the unbalanced force formed in the beam of the frame beam under seismic action will form a plastic hinge at the beam end at both ends of the frame beam. Especially when the brace is buckling unstable and the stiffness of the frame beam is small, the plastic hinge effect at the beam end is significant. This phenomenon may cause damage to the frame beam or even local floor subsidence. The buckling restraint support has a full hysteresis area under axial tension and compression, and its mechanical performance is excellent. It is obviously superior to ordinary steel bracing in energy dissipation capacity and seismic performance. It can accurately predict the bearing capacity of reinforced concrete under strong earthquake, and the energy dissipation distribution is more in line with the requirements of “energy seismic design method”.

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.