Hysteresis Envelope Research Articles

APPLICATION OF HYSTERESIS ENVELOPE MODEL TO STEEL BEAM-TO-COLUMN BOLTED JOINT

The paper demonstrates the applications of the hysteresis envelope model on the example of a double extended end plate beam-to-column bolted joint. The hysteresis envelope model represents a new analytical trilinear model that can describe the cyclic behaviour of joints in a moment-resisting steel frame and is suitable for nonlinear static pushover analysis.

Simplified shear force-chord rotation relationship for concrete-filled steel plate composite coupling beams

Concrete-filled steel plate (CFSP) composite coupling beam is a new type of coupling beam with large deformation and energy dissipation capacity. Given the need for shear force-chord rotation envelope curve of the coupling beam in the general modeling and analysis of coupled CFSP composite shear wall structures, this paper presents an envelope curve for CFSP composite coupling beams based on the results of nonlinear finite element analysis. A comparison between the results of finite element analysis (FEA) and the existing experimental data demonstrates the ability of the numerical model to accurately predict the shear force-chord rotation hysteresis curve and the local response of CFSP composite coupling beams. To gather sufficient data for plotting the envelope curve, multiple numerical models with different values assigned to the span/depth ratio, web plate thickness, flange plate thickness, and compressive strength of the concrete are analyzed under cyclic lateral loading. The analysis results are used to derive some equations for calculating the effective flexural and shear stiffness of the coupling beam based on the stiffness of steel plates and concrete infill, with a reduction coefficient applied to the stiffness contribution of the concrete. Some suggestions are provided for calculating the maximum and yield strengths of the coupling beam, based on the minimum strength corresponding to shear failure and flexural capacity. Finally, the analysis results are used to provide a trilinear model for the shear force-chord rotation hysteresis envelope of CFSP composite coupling beams.

Hysteresis Envelope Model of Double Extended End-Plate Bolted Beam-to-Column Joint

In this study, a hysteresis envelope mathematical model for the double extended end-plate bolted beam-to-column joint is proposed. The aim of a proposed joint model is to provide a more realistic behaviour of steel frames under seismic loading by using nonlinear static pushover analysis. The hysteresis envelope model defines the ratios between the monotonic properties of the joints and the properties of the joints during cyclic deformation. The proposed models are based on the hysteresis curves of the joints obtained by numerical simulations. The numerical model takes into account the geometric nonlinearity of the connecting elements, preloading of bolts, contacts between plates and bolts, and nonlinear properties of steel. Nonlinear static pushover analyses of steel frames are performed where the behaviour of the joints is described using the proposed hysteresis envelope models. The results are compared with the nonlinear static pushover analyses of steel frames with a trilinear monotonic joint model. Based on the results, the values of maximum peak ground acceleration for moment-resisting frames with the monotonic model of joints and hysteresis envelope model are estimated.

Analytical modelling of out-of-plane flexural response of unreinforced and strengthened masonry walls

The available literature on out-of-plane bending of masonry walls identifies two distinct phases – pre-cracking and post-cracking, in the force-displacement response. Accordingly, a semi-empirical model for out-of-plane behaviour of unreinforced and strengthened masonry walls is developed, which considers the overall load-displacement response in two phases. The pre-cracking phase model predicts the peak strength of the masonry, whereas the post-cracking model provides a hysteresis envelope (back-bone curve). A tri-linear displacement-based model is developed for one-way bending walls subjected to uniformly distributed lateral load, using a database of 38 experiments available in the literature. Analytical expressions for maximum lateral force and instability displacement are derived using the kinematic approach. Using the experimental database, two factors, λ1 and λ2 are estimated to calibrate the analytical results. The calibrated analytical model shows a good agreement with the experimental results. An analytical method for predicting the two-way out-of-plane flexural capacity in the pre-cracking phase of unreinforced and strengthened masonry walls using crackline method is also developed. This model shows reasonably good results, even with the assumption of an idealized crack pattern. However, the force-displacement parameters for obtaining two-way bending back-bone curve in the post-cracking phase show large scatter indicating that the available test results are not adequate to develop an empirically calibrated model.

Effect of Different Bracing Systems in Reinforced Concrete Frames under Cyclic Loading

Reinforced concrete (RC) framed structures are widely used as load transferring system in residential and commercial buildings. Even though the RC frames are designed for gravitational and seismic forces, but they are week under severe seismic events. The main disadvantage of the framed structures is inefficient bracing systems designed in it. This investigation is conducted mainly to study the effective bracing system in the RC framed structure to transfer the seismic force. This research aims to study the seismic performance of RC frames influenced by the various types of cross bracings under cyclic loading. The finite element analysis software package ABAQUS is used to investigate the braced RC frames analytically. The research scheme consists of three RC frames; the bare frame, the bare frame with single X-bracing (X frame), double X bracing (D-X frame) along the height. The structural parameters include, load-displacement hysteresis envelope, stiffness degradation and energy absorption were studied to analyze the performance of bracings. The results showed that the X frame and D-X frame noticeably increased the lateral strength, stiffness and energy dissipation properties compared to the bare RC frame. The results also indicated that the addition of X bracing along the height significantly enhanced the structural parameters of the RC frame.

Collapse of the magnetization by the application of crossed magnetic fields: observations in a commercial Bi:2223/Ag tape and comparison with numerical computations

We report on the effects of crossed magnetic fields on a commercial Bi:2223/Ag tape superconductor. The large magnetic moments which are generated in the specimen by the application or change of an external magnetic field (denoted Hz) directed perpendicularly to the plane of the tapes, hence along the c-axis of the crystallites, are considerably reduced in magnitude when subsequently a magnetic field (denoted Hy) directed along the plane of the tape, hence along the ab plane of the crystallites, is impressed and removed and made to undergo several half cycles of oscillations in the opposite direction. We find that a few cycles cause the magnetic moment to rapidly depart from the critical state major hysteresis envelope and reach asymptotically the reversible diamagnetic Meissner moment Mrev, which is aligned in the out-of-plane direction of the tape (c-axis). We observe that the application of crossed fields, first along the c-axis, then along the ab plane, effectively suppresses the bulk pinning magnetic moment, and quenches the associated persistent currents circulating in the ab plane. Our numerical computations, based on the finite element method and using an E–J power law to model the superconductor, can reproduce qualitatively the experimental data. In the numerical model, the current density flows perpendicularly to the plane within which the two components of the magnetic field vary. These investigations show that the observed decay in magnetization results from the complicated modification of current distribution due to the application of crossed magnetic fields within the sample cross section.

Theoretical study of the limitation of frequency excursion in hysteresis-mode boost-converter input stages in high power-factor AC-fed power supplies

Switched-mode power supplies employ either variable switch duty cycle or variable switching frequency (sometimes both) associated with some feedback circuitry to deliver the required output power. Intrinsic to both techniques is the generation of electromagnetic interference (EMI) and the spectrum of this unwanted interference, conducted as well as radiated, is wide. The authors present a theoretical basis for the design of a variable-output, variable-power switched-mode converter operating in the hysteresis mode at a fixed switch frequency and with limited current ripple; this makes the EMC filter circuits drastically simpler and cheaper. Instead of adjusting the high-frequency switching parameters, the technique involves the real time, responsive modulation of the hysteresis envelope. Suggestions for modulating the boost inductance are made. The former technique requires real time computer control of the feedback system (not a significant problem at 50 Hz supply frequency and today's digital processing speeds); the latter involves biasing the ‘operating point’ of a nonlinear inductance with a permanent magnet. The latter technique is not theoretically capable of delivering the required behaviour alone; this is demonstrated by a brief qualitative experiment where the technique alone has enabled reduction of switching frequency variation by a factor of two.

Magnetic relaxation in a commercial Bi:2223/Ag tape at 77 K

The evolution of the rate of flux creep along the major hysteresisenvelopes and along bridges between the envelopes in a commercial Bi:2223/Agtape at 77 K has been investigated. Magnetic relaxation rates depend stronglyon the prior magnetic history. It was found that the Bi:2223/Ag tape samplehas large flux creep along the hysteresis envelope. Flux creep activationenergy was calculated to be 0.12 eV from the rate of decay for the remanentmagnetization of 6 mT.

Seismic Behavior of Masonry Walls: Modeling of Hysteretic Rules

A method of modifying the lateral load–lateral displacement relationship obtained by a simple monotonic racking test to represent the skeleton hysteresis curve of an arbitrary dynamic response of a reinforced-masonry wall is proposed. The results of tests of 32 equal reinforced-masonry walls, tested by imposing monotonically increasing displacements, cyclic lateral displacements of two different shapes, and simulated displacement seismic response, have been used as a basis for the development of the procedure of modification. The amount of input energy, defined as the actuator work done to deform the specimens during the test, has been taken into account as the decisive parameter for carrying out this modification. On the basis of experimental results, correlation factors between the monotonic and cyclic hysteresis envelope curves, as well as stiffness and strength degradation parameters, which define the hysteretic rules, have been evaluated. Good agreement between predicted and experimental cyclic behavior of the walls has been obtained.

A constitutive model for hysteretic phase transition behavior

A model for rate independent hysteresis, based on the Duhem-Madelung framework, is examined in the context of temperature induced phase transitions such as those which occur in shape memory metals. Connection to experiment follows from its dependence upon the hysteresis envelope for complete transitions. Various requirements upon partial transitions, notably that such transitions proceed at a pace that is proportional to the phase fraction of the parent phase, complete the model. Restrictions on the hysteresis envelope are obtained that ensure monotonicity, containment and orientation requirements upon partial transition paths.

A model of adsorption-desorption hysteresis in which hysteresis is primarily developed by the interconnections in a network of pores

A porous material is described in terms of a model of its structure. The pores have a single internal cavity and four constrictions connecting this cavity to adjacent ones. Full and empty pores have various configurations of full and empty neighbours and these different configurations are used in the analysis of the behaviour of the material when it is being filled by adsorption and emptied by desorption. Their role is similar to that of intermediates in a chain of chemical reactions. The model for adsorption predicts a simple relation between adsorption scanning curves inside the hysteresis envelope irrespective of the number of interconnections of the pores. The desorption model gives results similar to published experiments.