Inelastic Wall Research Articles

Analysis of Reinforced Concrete Shear Walls with Different End Configurations for Seismic Design

The Canterbury earthquake royal commission report highlighted that, despite being well-detailed, several reinforced concrete (RC) shear walls did not achieve their anticipated ductility capacities. In order to enhance the performance of such walls during future seismic events, the report recommended the use of concentrated and confined rebars at the wall toes coupled with high reinforcement ratios within the wall to initiate secondary cracks and extend the inelastic wall regions, thus minimizing the corresponding seismic demands. In this respect, the current study evaluates the seismic performance of RC walls with flanged and boundary element configurations compared with their typical rectangular counterparts, when different reinforcement ratios are incorporated. Specifically, the study presents a detailed analysis of six three-story half-scaled RC shear walls tested under quasi-static cyclic loading representing different seismic demands. The six walls were originally tested in two phases, where each phase had three different wall types (i.e., rectangular, flanged, and boundary element configurations). Walls in both phases had the same overall dimension and cross-section area; however, Phase II walls had 2.4 times the vertical reinforcement ratios used in Phase I walls. Following a summary of the experimental program and results, the current study presents the analytical results of the walls in terms of their load-strain relationships, curvature profiles, stiffness degradation trends, energy dissipation capacities, and equivalent viscous damping ratios. A comparison between the theoretical and experimental curvatures is also presented for the test walls at different drift levels. The results show that flanged and boundary element walls had low yield curvatures and high ultimate curvatures which resulted in enhancing their displacement ductility capacities. Flanged and boundary element walls also exhibited higher stiffness degradation rates when compared with their rectangular counterparts, leading to reduced seismic demands. Moreover, flanged and boundary element walls with high vertical reinforcement ratios (1.58%–1.63%) had higher energy dissipation capacities than their counterparts with low vertical reinforcement ratios (0.66%–0.69%). However, rectangular walls with low vertical reinforcement ratios (1.17%) showed higher ultimate curvature capacities than rectangular walls with high vertical reinforcement ratios (2.80%). Overall, the results demonstrate that future editions of relevant design standards (e.g., CSA A23.3 and ACI 318-19) should consider assigning different seismic design parameters (e.g., ultimate compressive strains, equivalent viscous damping ratios, and ductility-related modification factors) for RC shear walls based on their end configurations that can significantly alter the performance of such walls under seismic events.

The peristaltic flow for Carreau fluid through an elastic channel

Abstract The purpose of this study is to investigate the effect of an elastic wall on the peristaltic flow of Carreau fluid between two concentric cylinders, where the inner tube is cylindrical with an inelastic wall and the outer wall is a regular elastic sine wave. For this problem, cylindrical coordinates were used, and a short wavelength “relative to channel width for its length,” as well as the governing equations of Carreau fluid in the Navier–Stokes equations. Then, the analytical solution has been investigated by using the regular perturbation technique. The solutions obtained by this perturbation are up to the fourth-order in dimensionless Weissenberg number ( W e {W}_{{\rm{e}}} ). The performed computations of various parameter values such as velocity, shear stress, and wave frame streamlines are discussed in detail for different values of the Weissenberg number ( W e {W}_{{\rm{e}}} ). The obtained results demonstrate that the fluid velocity increases with the increase in the value of W e {W}_{{\rm{e}}} and some features of the wall, while the opposite behavior is observed with the increase in other features of the wall. Hence, the presented numerical analysis reveals many aspects of the flow by considering a non-Newtonian Carreau fluid model, and the presented model can be equally applicable to other bio-mathematical studies. The results were evaluated using the Mathematica software program. The Mathematica program was used by entering various data for the parameters, where the program showed the graphs, then the effect of these parameters became clear and the results were mentioned in the conclusion.

The Peristaltic Flow of Williamson Fluid through a Flexible Channel

The purpose of this study is to investigate the effect of an elastic wall on the peristaltic flow of Williamson fluid between two concentric cylinders, where the inner tube is cylindrical with an inelastic wall and the outer wall is a regular elastic sine wave. For this problem, cylindrical coordinates are used with a short wavelength relative to channel width for its length, as well as the governing equations of Williamson fluid in the Navier-Stokes equations. The results evaluated using the Mathematica software program. The Mathematica program used by entering the various data for the parameters, where the program shows the graphs, then the effect of these parameters became clear and the results mentioned in the conclusion. Williamson fluid peristaltic flow through an elastic conduit is the subject of this investigation. For a number of significant elements, such as velocity distribution, stress and wave frame streamlines, graphic findings are supplied at the end of the article.

Investigation of Tie Bars Axial Force Demands in Composite Plate Shear Walls—Concrete Filled

Tie bars axial force demands due to concrete dilation and prying action were investigated through numerical studies. In the first part of this study, the Karagozian and Case Concrete model, which proved to provide reasonable in-plane flexural cyclic inelastic wall response while accounting for concrete dilation effect, was used to investigate the variation of confinement inside the infill concrete, the distribution of passive confining pressures at the steel–concrete interface, and the resulting tie bar axial force demands. Finite element analyses involving C-PSW/CF having different tie spacings, wall depths, and wall thicknesses were performed. In the second part of this study, the influence of plate local buckling on tie bar axial force demand was investigated and explained by prying action. A separate finite element study was performed to investigate the significance of prying action and equations were developed from free-body diagrams. The results showed the significance of the passive confining pressures due to concrete dilation, and prying action due to local plate buckling, on imparting axial forces in tie bars. Neither of these behavior are currently considered as design parameters for tie bars. The numerical analyses and results presented here are intended to provide useful insights and direction for the design and instrumentation of future C-PSW/CF experiments by the broader research community.

Time-dependent study of blood flow in an aneurysmic stenosed coronary artery with inelastic walls

Coronary arteries are a family of arteries that are indulged in the supply of oxygenated blood to the muscles of the heart. These blood vessels envelop the entire heart. These blood vessels encounter a common disturbance in which the vessel wall gets thickened leading to the blockage of the vessel lumen. Also, an uncommon condition seen is the development of a protruding bulging structure outward the lumen. The common disturbance seen is the stenosis of the artery whereas the uncommon bulging is the aneurysm. In the present paper, a discussion on the two-dimensional simulation of blood flow across the computationally constructed coronary arterial domain with clinical measurements is made. The arterial segment is assumed to have an aneurysm protrusion as well as a plaque developed due to stenosis. The velocity profile, pressure profile, and the wall shear stress patterns observed are enunciated by treating blood as a classical Newtonian fluid. The results show that the spots below the aneurysm are prone to develop new sacs and lesions. The main innovations of this study are: a) identifying the most probable spots for new plaque development; b) the interrelation between the flow characteristics due to the presence of stenosis and the aneurysm sac.

Investigation of influence of concrete material models on cyclic inelastic response of a concrete filled composite plate shear wall

A previously benchmarked finite element model of a previously tested composite plate shear wall-concrete filled (C-PSW/CF) was used to investigate the influence of three concrete material models on in-plane cyclic inelastic wall response, using LS-Dyna. The concrete material models considered were the Winfrith, KCC and CSCM, all available in LS-Dyna. Wall moment hysteresis, using the three concrete material models, were obtained and compared. Individual contribution of the steel and concrete to total base moment was investigated for each wall with the three concrete material models. The numerical results obtained using the KCC and CSCM were compared against the benchmarked results obtained using the Winfrith concrete material model. Moment contribution of the steel web and the steel boundary on total base moment of the steel part of the wall and moment contribution of the concrete web and concrete boundary on total base moment of the concrete part of the wall were individually investigated. The wall models with the KCC and CSCM concrete models were observed to cannot capture wall pinching which was captured by the Winfrith concrete model. The wall strength was overpredicted by the CSCM concrete model and predicted reasonably by the KCC concrete model. Average axial stress distribution of the infill concrete was obtained to investigate wall neutral axis and the maximum attained concrete strength using the three concrete models. Concrete axial stress distribution showed some level of confinement for the concrete models considered.

Precision Ultrasonic Meters of Fluid Level in Sealed Containers

The problems of measuring the fluid level in steel containers through a wall by acoustic methods are considered. When measuring the level by sound propagation time in a fluid in case of an inelastic wall the best accuracy is provided by the correlation-phase reception of compound signals. But for measurements in steel containers, such a technique is usually not used due to phase structure distortions of a signal with a broad frequency bandwidth when transmitting through an elastic wall (having multiple resonances in this band). The use of correlation-phase reception in such cases may be possible by choice a probing signal, a phase structure distortion of which will be small when transmitting through a wall. The aim of the work is to determine the possibilities of using the correlation-phase reception and the achievable accuracy of level measuring in the conditions of different wall thickness of steel containers. The significance of research is determined by the possibilities of a multiple increase in the measuring accuracy. Acoustic methods and level measuring devices are considered; the advantage of time-pulse (time-of-flight, TOF) methods over interferometric (including swept-frequency acoustic interferometry, SFAI) and other measuring methods in large containers is shown. A method of level measuring using the correlation-phase reception of compound signals and a scheme for calculating the broadband impulse signal transmission through an elastic wall (and building the amplitude-frequency and phase-frequency characteristics) taking into account the longitudinal and shear waves of thickness wall vibrations and standing waves of its resonant vibrations along the length (diameter) are proposed. A method for selecting the probing signal frequency range according to an amplitude-frequency characteristic of elastic wall which provide the low phase structure distortions when transmitting through a wall is suggested. The achievable accuracy estimates of measuring the sound velocity and the fluid level in rail tank wagons are obtained. Experimental works carried out on a thin-walled (0.8 mm) barrel with signals of the frequency range of 250-750 kHz (i.e. frequencies below the first thickness resonance frequency of barrel bottom) are confirmed the small phase structure distortion of signals when transmitting through the bottom and the high efficiency of the correlation-phase reception. With a signal-to-noise ratio of 0.4, a high time measuring accuracy of ~0.15 μs corresponding to a level measuring accuracy of ~0.1 mm is obtained. For signals of frequency range 250-750 kHz the interval of wall thickness is defined as 0.3-3.6 mm at which the efficiency of the correlation-phase reception and the level measuring accuracy should be high. The results showed that the use of correlation-phase reception of compound signals when measuring a fluid level through the bottom of a thin-walled steel barrel is possible and provides both high operating efficiency in the noise conditions and high measuring accuracy. It can be expected that the same accuracy factors and operating efficiency will be kept in a bottom thicknesses range at which the probing signal frequencies will be less than the first bottom thickness resonance frequency. In cases of large bottom thicknesses, if the first bottom thickness resonance frequency is low, the probing signal spectrum may include frequency regions between the thickness resonance frequencies. In this case, it becomes possible to use the correlation-phase reception for the level measuring in containers with a wide range of bottom thicknesses. Ref. 20, tab. 1, fig. 7.

Inherent thermal convection in a granular gas inside a box under a gravity field

We theoretically prove the existence in granular fluids of a thermal convection that is inherent in the sense that it is always present and has no thermal gradient threshold (convection occurs for all finite values of the Rayleigh number). More specifically, we study a gas of inelastic smooth hard disks enclosed in a rectangular region under a constant gravity field. The vertical walls act as energy sinks (i.e. inelastic walls that are parallel to gravity), whereas the other two walls are perpendicular to gravity and act as energy sources. We show that this convection is due to the combined action of dissipative lateral walls and a volume force (in this case, gravitation). Hence, we call it dissipative lateral walls convection (DLWC). Our theory, which also describes the limit case of elastic collisions, shows that inelastic particle collisions enhance the DLWC. We perform our study via numerical solutions (volume-element method) of the corresponding hydrodynamic equations in an extended Boussinesq approximation. We show that our theory describes the essentials of the results for similar (but more complex) laboratory experiments.

Computer Modeling of Controlled Microsphere Release and Targeting in a Representative Hepatic Artery System

Combating liver tumors via yttrium-90 ((90)Y) radioembolization is a viable treatment option of nonresectable liver tumors. Employing clinical (90)Y microparticles (i.e., SIR-Spheres and TheraSpheres) in a computational model of a representative hepatic artery system, laminar transient 3D particle-hemodynamics were simulated. Specifically, optimal particle release positions in the right hepatic (parent) artery as well as the best temporal release window were determined for the microspheres to exit specific outlet daughter vessels, potentially connected to liver tumors. The results illustrate the influence of a curved geometry on the velocity field and the particle trajectory dependence on the spatial and temporal particle injection conditions. The differing physical particle characteristics of the SIR-Spheres and the TheraSpheres had a subtle impact on particle trajectories in the decelerating portion of the arterial pulse, i.e., when the inertial forces on the particles are weaker. Conversely, particle characteristics and inelastic wall collisions had little effect on particles released during the accelerating phase of the arterial pulse, i.e., both types of microspheres followed organized paths to predetermined outlets. Such results begin paving the way towards directing 100% of the released microspheres to specific daughter vessels (e.g., those connected to tumors) under transient flow conditions in realistic geometries via a novel drug-particle targeting methodology.

Effects of surface friction on a two-dimensional granular system: Cooling bound system

Experiments performed by Phys. Rev. E 62, 2380 (2000)] on two-particle collisions and dynamics emphasized the importance of the role played by substrate friction, in particular kinetic friction, on the particle dynamics after collisions on a substrate. We present a numerical model which accounts for collisional and surface frictional dissipation and their influence on particle dynamics for a quasi-two-dimensional cooling initially dilute granular material. This model makes the simplifying assumption that the collision dynamics is determined solely by the incoming velocity and angular velocities of the colliding particles. We apply this model to a numerical simulation of a monolayer of monodisperse particles moving on a substrate, enclosed between inelastic walls. We find that surface friction-in particular, kinetic friction-plays a dominant role in determining the dynamics of quasi-two-dimensional multiparticle systems where the particles are in continuous contact with a substrate. Results from simulations performed for different system sizes indicate that surface friction and the inelastic walls lead to clustering of the particles in and near the vicinity of the walls. We find that the rate of decrease of average total kinetic energy is the highest when the majority of the particles have just collided and are experiencing kinetic frictional forces and torques. We also find from our calculations that, on average, particle-wall collisions lead to more dissipation than particle-particle collisions for a single particle for fixed restitutional parameters.

Strengthening of moment‐resisting frame structures against near‐fault ground motion effects

AbstractNear‐fault ground motions with forward directivity are characterized by a large pulse. This pulse‐like motion may cause a highly non‐uniform distribution of story ductility demands for code‐compliant frame structures, with maximum demands that may considerably exceed the level of code expectations. Strengthening techniques for multi‐story frame structures are explored with the objective of reducing maximum drift demands. One option is to modify the code‐based SRSS distribution of story shear strength over the height by strengthening of the lower stories of the frame. The modified distribution reduces the maximum story ductility demand, particularly for weak and flexible structures. However, this strengthening technique is less effective for stiff structures, and is almost ineffective in cases in which the maximum demand occurs in the upper stories, i.e. strong and flexible structures. As an alternative, the benefits of strengthening frames with elastic and inelastic walls are evaluated. The effects of adding walls that are either fixed or hinged at the base are investigated. It is demonstrated that strengthening with hinged walls is very effective in reducing drift demands for structures with a wide range of periods and at various performance levels. Wall inelastic behavior only slightly reduces the benefits of strengthening with hinged walls.Copyright © 2004 John Wiley & Sons, Ltd.

Flexural Capacity of Pressurized Steel Pipe

This paper describes the experimental and theoretical behavior of two large-scale pressurized pipes tested with a sleeve fully welded to the midspan of each specimen. Each specimen was subjected to an internal pressure, a constant axial load and lateral deformation of a four-point bend test to simulate the flexural behavior of a buried pipeline. The only test parameter was the length of the sleeve needed for pipe repair; one specimen had a sleeve length equal to one pipe diameter, and the second specimen had a sleeve that was two pipe diameters in length. Flexural deformations were imposed on each test specimen until clear failure occurred. For both specimens, failure occurred by local wall buckling of the carrier pipe adjacent to the sleeve region. A simple theoretical model is discussed to predict the flexural capacity of pipes subjected to these load conditions. This analytical method was developed to enable a quick computation of the inelastic flexural strength of the pipe, and to enable a check of the output from a more sophisticated finite element analysis. Reasonably good agreement was found between the theoretical and the experimental flexural capacity of the pressurized pipe. Analytical results demonstrated that the Tresca yield criterion conservatively estimated the inelastic flexural strength of the pressurized pipe. It was also found that, when using the Tresca criterion to describe the inelastic behavior of the pipes tested in this research program, local inelastic wall buckling was initiated at a displacement ductility of about 3.

Analysis of a thin-walled pressurized torus in contact with a plane

Finite element analysis is applied to study the large deflection of a standing torus loaded by a plane. The internally pressurized thin-walled structure is found to have an elliptical footprint area. Considerable bulge occurs in the sidewall in the region of the load plane. Stress distributions throughout the torus are shown for various load levels and for various modeling strategies at a given load level. In large load ranges finite element calculations show compressive circumferential stress and negative curvature in the footprint region. Results are compared with inelastic wall analysis.

Models of elastic and inelastic flux switching

The total <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\dot{\phi}(t)</tex> waveform of a square-loop magnetic core switched by MMF <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">F(t)</tex> from negative remanence <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\phi = -\phi_{r}</tex> is composed of elastic <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\dot{\phi}_{\epsilon}(t)</tex> , decaying inelastic <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\dot{\phi}_{i}(t)</tex> , and bell-shaped main inelastic <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\dot{\phi}_{ma}(t)</tex> . The worst delta noise in a coincident-current memory core pair is essentially <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\dot{\phi}_{i}(t)</tex> . The sources of these components and the static <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\phi(F)</tex> curve are explained qualitatively by means of the random variations of the energy gradient vs. domain-wall position: elastic wall displacements and elastic rotation of magnetization induce <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\dot{\phi}_{\epsilon}(t)</tex> ; minor inelastic wall displacements of essentially constant wall areas induce <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\dot{\phi}_{i}(t)</tex> ; and major inelastic wall displacements (involving domain collisions) of varying wall areas induce <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\dot{\phi}_{ma}(t)</tex> . Semiempirical models for the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\dot{\phi}</tex> components are based on the characteristics of these displacements. A satisfactory agreement is obtained between these models and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\dot{\phi}(t)</tex> oscillograms of a thin ferrite core.

THE IMPORTANCE OF AURAL SYMPTOMS IN THE EARLY DIAGNOSIS OF. TUMOR OF THE CEREBELLOPONTILE ANGLE

The eighth nerve, comprising the auditory and the vestibular, from a diagnostic surgical standpoint, may be divided into three portions: the<i>peripheral</i>, comprising the end organs in the labyrinth; the<i>intradural</i>, extending from the fundus of the internal auditory meatus to its entrance in the groove between the pons and the medulla, and the<i>intracerebral</i>ramifications of its tracts in the brain to its cortical centers in the temporosphenoidal lobe and cerebellum. The sudden and commanding character of the symptoms in inflammation of the cochlea and semicircular canal are due largely to the small, inelastic walls of the containing bony labyrinth, compelling an immediate paralysis of the function of the delicate nerve structures; their bony case not allowing the gradual development of symptoms from slow increasing pressure on the nervous structure, which frequently occurs in nervous tissue elsewhere. (The greater resistance of the auditory portion in the labyrinth in serous