Displacement Ratio Research Articles

Prestressed concrete wall system with friction devices: Seismic performance and direct displacement–based seismic design

It is convenient to use the inelastic displacement ratio spectra and residual displacement ratio spectra to predict the maximum inelastic displacement and residual displacement of building structures based on linear elastic analysis directly. The prestressed concrete wall system with friction devices (PCW-FD system) can be simulated by single-degree-of-freedom (SDOF) model with self-centering behavior. To investigate the seismic performance of PCW-FD system, the SDOF models with fully and non-fully self-centering behavior are analyzed firstly, and it is concluded that the hysteresis parameters (strength reduction coefficient, post-yield stiffness coefficient, energy dissipation coefficient, and period) have significant influence on the seismic responses (such as constant relative strength inelastic displacement ratio, constant relative strength residual displacement ratio, maximum absolute acceleration, the hysteretic energy, and site classifications) during short period, and the trends of the seismic responses are similar at different site classifications. Then a large amount of the result data is summarized, and the constant relative strength inelastic displacement ratio spectra and the constant relative strength residual displacement ratio spectra with enough precision (the correlation coefficients are 0.957 and 0.947, respectively) are established by conducting regression analysis. Finally, the direct displacement–based seismic design method is improved and verified to be suitable for PCW-FD system.

Hydraulic microactuator with coarse/fine drive-switching mechanism

For precise physical and chemical analyses of cells in microfluidic devices, they should be located near the sensors on a microchannel wall. To transport cells close to the sensors precisely, a hydraulic microactuator with a coarse/fine drive-switching mechanism was developed. The microactuator has a movable thin film with micropillars, and switches drive modes through the contacts of the micropillars into a microchannel wall. A coarse approach and a fine adjustment of the position of cells on the thin film toward the microchannel wall by switching the drive modes was achieved in the microactuator. The displacement of the microactuator was measured at 1 µm resolution using the focus degrees obtained using the two-dimensional fast Fourier transformed images. The displacement ratio of the coarse to fine drive mode achieved using the microactuator was 13.9. Using the microactuator, cyanobacteria were introduced into the device and were transported 53 µm from the bottom to the top of the microchannel in the coarse drive mode, and the position of the cyanobacteria was precisely adjusted near the microchannel wall in the fine drive mode.

Numerical Analysis of the Basement Wall Behaviour nearby Unsupported Deep Excavation

This paper presents a numerical model of the influence of deep excavation on the behavior of a model of basement wall adjacent to an unsupported excavation. The examined wall has wall1 that has completely faced excavation. The normal, shear, bending, and vertical and lateral displacements of walls have been examined. The finite element modeling by PLAXIS 3D has been adopted to investigate the problem. The soil strata studied is 25 m deep. The nearby excavation has a 1.0 m excavation width. The results show that as the excavation depth is equal to wall depth, the lateral displacement and the bending moment are reduced and zero along with wall depth. At the excavation depth of more than 2.0 m, the lateral wall displacement Ux increases but in the reverse direction (towards excavation). The increasing ratio of lateral displacement is 10 times before the excavation at the wall head as the excavation depth is 6.0 m. The soil collapses, and the failure happens at 7.0 m depth of excavation. At these stages, the calculation is not completed, and the expected results are probably more than obtained values.

Structural analysis of GFRP elastic gridshell structures by particle swarm optimization and least square support vector machine algorithms

The gridshell structure is a kind of freeform structure, which is formed by the deformation of a flat grid and the final shape is a double curvature structure. The structural performance of the gridshell is usually obtained by finite element analysis (FEA), which is a time-consuming procedure. This paper aims to present a framework for structural analysis based on the machine learning (ML) model in order to reduce computational time. To this aim, design parameters including the length, width, height, and grid size of the structure are taken into consideration as inputs. The outputs are the member-stresses and the ratio of displacement to self-weight. Therefore, a combination of two algorithms, least square support vector machine (LSSVM) and particle swarm optimization (PSO), is considered. PSO-LSSVM hybrid model is applied to predict the results of the structural analysis rather than the FEA. The results show that the proposed hybrid approach is an efficient method for obtaining structural performance.

Application of force-monitor ultrasonography to assess distal radioulnar joint instability in patients with triangular fibrocartilage complex injury.

In this study, we evaluated the differences and measurement accuracy in the force-displacement relationship of the distal radioulnar joint (DRUJ) between patients with triangular fibrocartilage complex (TFCC) injury and healthy controls using force-monitor ultrasonography. This study included 11 TFCC injury patients and 22 healthy controls. We evaluated differences in the force-displacement relationship of the DRUJ in these patients using force-monitor ultrasonography. Cyclic compression was applied to the dorsal surface of the ulnar head. Distance between the dorsal surface of the distal radius and ulnar head at the DRUJ level was measured in the initial and pressed-down positions. Changes in radioulnar displacement, applied force, and displacement-to-force ratio were measured. Furthermore, we compared the parameters between the affected and unaffected wrists and between TFCC injury patients and controls. The radioulnar displacement and displacement-to-force ratio were significantly larger in the affected wrists than in the unaffected wrists (P = 0.003 and P = 0.02). The affected/unaffected side ratio of radioulnar displacement and displacement-to-force ratio were significantly larger in the TFCC injury patients than in the controls (P = 0.003 and P = 0.02). The area under the curve was 0.82 for the affected/unaffected ratio of the radioulnar displacement. The optimal cutoff value indicated by the receiver-operating characteristic curve for the affected/unaffected ratio of the radioulnar displacement was 1.71; the sensitivity and specificity were 82% and 86%, respectively. Assessing the DRUJ instability with force-monitor ultrasonography may help identify TFCC-injured wrists.

Cavernous-fractured carbonate reservoir: problem of water-oil displacement ratio substantiation

Cavernous-fractured carbonate reservoir: problem of water-oil displacement ratio substantiation

Comparative Study: The Effect of Tuned Mass Damper and Fluid Viscous Damper on The Response of Two Different Models of G+15 Storey Building During Earthquake

During the earthquake phase, dampers were used to dissipate energy as well as stop the Deformation of the Structure. We may reduce buckling and failure of columns and beams by increasing the stability of the frame with the help of dampers. During earthquakes, high-rise buildings are destroyed, and there is significant deformation. We may reduce the shaking of reinforcement cement concrete structures during an earthquake by using dampers. We used various types of dampers in this analysis to determine the suitability of various damper types during an earthquake. An Empirical study has been performed for the comparative review of various forms of dampers used for multi-story cement concrete building reinforcement. The Time History Method was used to assess the seismic behaviour of a G+15 storey building with and without dampers. The earthquake load is applied in both the x and y directions for research. The IS1893:2002(part 1) code is used in conjunction with the ETABS 2018 version 18.1.1 package for the purpose of analysis. The findings of these experiments are discussed in terms of various parameters such as maximal absolute displacement, absolute acceleration, absolute velocity, storey shear, storey drift, storey stiffness, and modal participation mass ratio. It is carried out in order to compare these various parameters. Different kinds of dampers are used to dissipate seismic energy. In this article, a comparison of two different buildings of different bay sizes (5mx5m & 6mx6m) is used, as well as a comparative analysis of various parameters using Tuned Mass Damper and Fluid Viscous Damper.TECT

Shock Isolation Characteristics of a Bistable Vibration Isolator With Tunable Magnetic Controlled Stiffness

Abstract This paper investigates the shock isolation characteristics of an electromagnetic bistable vibration isolator (BVI) with tunable magnetic controlled stiffness. The theoretical model of the BVI is established. The maximum acceleration ratio (MAR), maximum absolute displacement ratio (MADR), and maximum relative displacement ratio (MRDR) are introduced to evaluate the shock isolation performance of the BVI. The kinetic and potential energy are observed to further explore the performance of the BVI. The effects of the potential barrier, shape of potential well, and damping ratio on the BVI are discussed compared with the linear vibration isolators (LVIs). The results demonstrate that the intrawell oscillations and snap-through oscillations are determined by the excitation amplitude and duration time of main pulse. MADR and MRDR of the BVI are smaller than those of the LVI. The maximum acceleration peak amplitude of the BVI is far below that of the LVI, especially when the snap-through oscillation occurs. In brief, the proposed BVI has a better shock isolation performance than the LVI and has the potential to suppress the shock of space structures during the launch and on-orbit deploying process.

Factors that contribute to the elongation of drumlins beneath the Green Bay Lobe, Laurentide Ice Sheet

AbstractDrumlin shape has been hypothesized to correlate with ice‐flow duration and slip speed, but modern‐day analogues and the Coulomb nature of till render the basis of these correlations in question. The evolution of flow‐parallel subglacial landforms is of importance for ice flow because the form drag they provide may be a dominant factor in regulating glacier slip speeds. Here we examine the relationship between drumlin shape and cumulative slip displacement (i.e. time‐integrated slip speed) as a dominant glaciological control on drumlin shape. First, a new method is developed that allows slip speed to be estimated for deformable bedded glaciers along a flow line from an ice surface profile. Then, reconstructed surface profiles for ice margin chronologies of the Green Bay Lobe (GBL) are used to construct and estimate the spatially varying cumulative slip displacement for use in comparison with drumlin elongation ratios. We focus on a sector of the GBL near the central flow line where the geology is simple and glaciological controls are likely to dominate bedform development. Using Bayesian statistical analysis, a positive and statistically robust relationship between cumulative slip displacement and drumlin elongation ratio is found. Our analysis indicates that drumlin shape could be used to infer palaeo glacier slip speeds if time under the ice can be well constrained and geologic influences are minimal. These findings also suggest that drumlin‐supplied drag could decrease with increased cumulative slip displacement in the absence of rigid geologic features that fix drumlin positions.

Design and Experiment Using Flexible Bumps for Piezoelectric-Driven Hydraulically Amplified Braille Dot Display.

This paper describes the design of a piezoelectric-driven hydraulically amplified Braille-flexible bump device that enables the flexible formation of Braille characters. A piezoelectric vibrator is used to excite fluid resonance in a cavity, and displacement is realized by compressing the fluid, allowing Braille character dots to be formed. First, the structural design and working principle of the device, as well as the method used to drive the fluid, are explained. Expressions for the output displacement and amplification ratio of the flexible film and piezoelectric vibrator are then obtained through kinetic analysis of the system unit. Subsequently, the structural parameters that affect the output displacement and the liquid amplification are described. Finally, experimental tests of the system are explained. The results indicate that the output displacement of the contact formed by the flexible film reaches 0.214 mm, satisfying the requirements of the touch sensitivity standard for the blind, when the fluid cavity diameter measures 31 mm and the resonance frequency is 375.4 Hz. The corresponding water discharge is 8.8 mL. This study proves that constructing a Braille bump device in this way is both feasible and effective.

Effect of Foundation Flexibility on the Seismic Performance of a High-Rise Structure under Far-Field and Near-Field Earthquakes

In this study, the seismic performance of a 20-storey steel structure with a mat foundation located on layered soil is investigated under an array of strong ground excitations, which includes 6 far-fault and 6 near-fault earthquakes. Eight different modes for soil layering have been considered in the numerical simulation. FLAC 2D nonlinear platform has been used to model the near-realistic behavior. To this end, hundred lines of codes and sub-routines have been developed in this platform to perform the analysis. The results of the analyzes include the absolute displacement of the floors, the ratio of the relative displacement of the floors, the shear force, the axial force, and the bending moment of the columns. It was concluded that for a 20-story structure on a mat foundation under both far-field and near-field earthquakes, the most reliable type of soil is the dense sandy soil and the most critical case is the soft clay soil. It was also observed that the near-field strong ground motions have imposed more critical structural responses compared to far-field records.

Development of Bridge and Lever Type Compact Compliant Mechanism for Micro Positioning Systems

Nowadays, for precision positioning applications (Micro-Electro-Mechanical Systems, Nano/Micro positioning devices), compliant mechanisms are extensively used over traditional mechanisms. Compliant mechanisms are joint less mechanism having merits as no wear and friction, no backlash and no lubrication. In this paper, a newly developed flexure hinge based bridge and lever type compact compliant mechanism has been proposed for the precision linear displacement applications. This mechanism can be used in the portable cameras for image stabilization, lens shutters, alignment and levelling devices, etc. The key performance parameters for developing the compliant mechanism are the input displacement/force, output displacement and amplification ratio. For designing compact amplified compliant mechanism (CACM), Pseudo-Rigid-Body-Model (PRBM) method is used. The finite element analysis of developed micro-displacement amplifier compliant mechanisms carried out by using ANSYS workbench. The analyses and experimentation is performed for the input displacement, output displacement and amplification ratio of mechanism. An input force range considered for analysis is in between 1 N to 50 N. All the results from analytical, simulation and experimentation are compared. The error in output displacement is observed up to 6% and the geometric amplification ratio for the mechanism is observed up to 6.5.

Time-averaged mean squared displacement ratio test for Gaussian processes with unknown diffusion coefficient.

The time-averaged mean squared displacement (TAMSD) is one of the most common statistics used for the analysis of anomalous diffusion processes. Anomalous diffusion is manifested by non-linear (mostly power-law) characteristics of the process in contrast to normal diffusion where linear characteristics are expected. One can distinguish between sub- and super-diffusive processes. We consider Gaussian anomalous diffusion models and propose a new approach used for their testing. This approach is based on the TAMSD ratio statistic for different time lags. Similar to the TAMSD, this statistic exhibits a specific behavior in the anomalous diffusion regime. Through its structure, it is independent of the diffusion coefficient, which, in general, does not influence anomalous diffusion behavior. Thus, the TAMSD ratio-based approach does not require preliminary knowledge of the diffusion coefficient's value, in contrast to the TAMSD-approach, where this value is crucial in the testing procedure. Based on the quadratic form representation of the TAMSD ratio, we calculate its main characteristics and propose a step-by-step testing procedure that can be applied for any Gaussian process. For the anomalous diffusion model used here, namely, the fractional Brownian motion, we demonstrate the effectiveness of the proposed methodology. We show that the new approach outperforms the TAMSD-based one, especially for small sample sizes. Finally, the methodology is applied to the real data from the financial market.

Experimental investigation into the seismic behavior of squat reinforced concrete walls subjected to acid rain erosion

Acid rain erosion will continuously deteriorate the physical and mechanical properties of materials and finally degrade the seismic performance of reinforced concrete (RC) structures. Nevertheless, the effect of acid deposition on squat RC walls, an important part of lateral force-resisting systems, has not been reported in existing research. Thus, in this paper, an artificial climate simulation method was used to accelerate the acidic attack process on four squat RC wall specimens with an aspect ratio of 1.0. Then quasi-static loading tests were conducted to observe their cyclic behavior under different acid rain spraying cycles (ARSCs). The results show that as ARSCs increase, the degree of degradation of concrete strength and the corrosion weight loss of steel bars have a rising trend, and the bearing capacity and deformation capacity of the squat RC walls deteriorate gradually. Simultaneously, the ratio of shear displacement to total lateral displacement increases, indicating a more noticeable shear failure characteristic with the addition of ARSCs. Moreover, the failure mode shifts from the mixed flexure and diagonal compression mode to the diagonal tension mode with a significant decrease in ductility and energy-dissipation capacity. It is also found that the degradation rate of the shear strength of squat walls under acid rain erosion is larger than that of the flexural strength, which may lead to the transition of failure mode.

Localized health monitoring for seismic resilience quantification and safety evaluation of smart structures

Natural hazards such as earthquakes, hurricanes, and floods cause billions of dollars of economic loss and claim thousands of lives every year. Researchers have proposed various tools and techniques to evaluate, manage, and mitigate seismic risk and improve resilience. Nonetheless, given the uncertainties involved, accurate system assessment requires real-time data on structural health and performance which can be attained through structural health monitoring (SHM) systems. This paper integrates component-based resilience quantification methods and SHM techniques to present a new probabilistic framework for seismic structural system evaluation and decision analysis. A trilateral framework is introduced which (1) uses the data obtained from a localized wireless sensor network to detect and locate damage, (2) develops component-based functionality curves to quantify the seismic resilience of the structure, and (3) makes post-quake rapid decisions based on a multi-criteria safety evaluation method. A nonlinear autoregressive exogenous (ARX) model is used to identify structural response and a statistical damage-sensitive coefficient is used to detect, locate, and measure damage in the system. Minor damages due to corrosion and major damages due to past extreme events are studied in the functionality analysis. Two groups of archetype building structures located in a high seismic region are studied, namely steel diagrid and special reinforced concrete structures. The results show that maximum absolute floor acceleration is the most accurate demand parameter for locating damage whereas maximum floor displacement and interstory drift ratio can effectively detect and measure damages.

Understanding the role of local texture variation on slip activity in a two-phase titanium alloy

During plastic deformation of engineering alloys with a hcp crystal structure, slip systems with different critical resolved shear stresses can be activated. In the case of two-phase titanium alloys such as Ti-6Al-4V, it is well established that various a→ and c→+a→ type slip systems can be activated in the α-phase, which dominates this alloy. However, their relative likelihood is less well established particularly when comparing prismatic a→ and basal a→ slip which are known to have similar critical resolved shear stress values. By combining EBSD-based grain orientation mapping and high-resolution digital image correlation, grain specific shear strain mapping and Burgers vector direction analysis was carried out after small levels of plasticity in two differently microtextured Ti-6Al-4V samples. This enabled the different types of strain heterogeneity and strain patterns to be linked to the underlying microstructure and microtexture. The detailed analysis shows that the dominance of a particular a→ type slip mode greatly varies with the local texture and that shear strain patterns extend across many grains when soft macrozones (clusters of similarly orientated grains) are present. The work highlights that the relative displacement ratio analysis significantly improves slip trace analysis in hcp crystals by reducing the cases of ambiguous solutions and that grain neighbourhood can have a greater impact on slip system activation than Schmid factor.

NMR characterization of fluid mobility in tight sand: Analysis on the pore capillaries with the nine-grid model

Pore fluids are generally classified into movable fluid and irreducible fluid by one or two NMR T2 cut-offs (T2C). Fluid movability in tight sands may not be accurately characterized by pore size-based classification methods solely because of the complex pore structure and heterogeneity in pore size. In this study, we propose a nine-grid model to characterize fluid movability and calculate the percentages of free fluid (FF), capillary-bound fluid (CAF), and clay-bound fluid (CBF). The pore size distributions and capillarity boundaries are converted from T2 and mercury injection capillary pressure (MICP). Three T2 spectra (TFF, TCAF, and TCBF) under water saturation, centrifugation, and heat-treatments are measured to classify pore fluids as FF, CAF, and CBF according to the pore capillary force needed to displace them. T2C1 and T2C2 are calculated to classify pores into three size categories. Finally, the nine-grid model that is composed of the three T2 distributions and two T2C is applied to explain results of a N2 displacement test and evaluate fluid movability in two samples. The results suggest that the conventional classification method based on fixed T2C results in the underestimation of CAF and overestimation of CBF. The macro-pores (T2 > T2C1) range in size larger than 85.20 nm and 113.64 nm and have pore capillary pressures lower than 6.46 MPa and 8.62 MPa. Micro-pores (T2 < T2C2) are smaller, ranging in size lower than 13.96 nm and 31.84 nm, and have high capillary pressures. Compared with conventional methods, the introduced model interprets the pore capacity-related displacement process well, especially for the remarkable displacement ratio of medium pores. The co-effect of fluid types and pore sizes in gas-displacing-water tests indicates that the process is primarily governed by fluid-matrix interaction and the connections among pores, rather than a simple sequential displacement of larger-to-smaller pores.

Experimental and numerical assessment of Piston Hybrid Frictional Metallic Damper (PHFMD)

A novel hybrid frictional metallic passive damper is introduced in this study. The Piston Hybrid Frictional Metallic Damper (PHFMD) is equipped with friction pads and steel variable-width strips as energy dissipating parts. These parts are put in the final assembly of the damper with the aid of connectors and rigid parts. The PHFMD characterizing parameters have been determined based on comprehensive experiments. At first, a setup is designed to test the response of friction pads at different clamping torque. The experimental data approves the applicability of the pads in terms of the stability of their hysteretic response. At the second stage, cyclic loads have been applied to three different PHFMD specimens. These specimens are specially designed to exhibit single-phase (PHFMD-A and PHFMD-B) and dual-phase (PHFMD-C) response when subjected to displacements. In the case of dual-phase response, the first phase’s capacity will be activated in case of wind or light to moderate earthquake excitations. In case of severe earthquakes, the full capacity of the dual-phase damper will be mobilized to mitigate earthquake impact on the structure. The experimental results approve the significant performance of the dampers in fulfilling design goals. The performance parameters include the achievable cumulative displacement, dissipated energy, and effective equivalent viscous damping ratio. It is observed that all the specimens have endured accumulated displacement of over 2000 mm (reaching near 4000 mm for the PHFMD-C specimen) while dissipated a significant amount of energy. The specimens also have demonstrated significant viscous damping ratios in the range 45–55%. None of the dampers has shown any degradation or damage when subjected to standard loading protocol. In order to provide a means for the analysis, FE models of dampers have also been developed. Comparison of FE results and experimental data show remarkable agreement. Finally, FE-verified analytical relations are provided for the design purposes of single-phase and dual-phase PHFMDs.

Effect of Aftershocks on Seismic Fragilities of Single-Story Masonry Structures

The effect of aftershocks on the fragility of single-story masonry structures is investigated using probabilistic seismic demand analysis Finite element models of an unreinforced masonry (URM) structure and a confined masonry (CM) structure are established and their seismic response characteristics when subjected to mainshock, aftershock, and the mainshock-aftershock sequence are then comparatively investigated. The effects of aftershocks and the use of confining members on the seismic response are studied. Probabilistic seismic demand models of the structures are built, and fragility curves under various conditions are derived to investigate the effect of aftershocks on structural fragility. The maximum roof displacement and maximum inter-story drift ratio are lower in the confined masonry model than in the unreinforced masonry model; additionally, the probability of exceedance (PE) values of each damage limit state reduced, and those of the mainshock-damaged models subjected to aftershock significantly increase compared to those directly subjected to a same-intensity aftershock. The probability of severe damage or collapse compared with the mainshock-damaged CM model is greater than when each is subjected to a same intensity aftershock. The use of confining members benefits aftershock resistance and reduces the failure probability of the mainshock-damaged structure. The PE values significantly increase with the aftershock scaling factor δ. Therefore, the effect of aftershocks should be considered in the seismic design and analysis of masonry structures.

Study on fast interference wave resistance optimization method for trimaran outrigger layout

The configuration of outriggers has a significant influence on the wave resistance of a trimaran. In this paper, slender ship theory is applied to calculate the wave resistance of trimarans. In order to improve the calculation accuracy, NURBS (Non-Uniform Rational B-Splines) method is introduced to molding the hull surface and the relative ideal results are obtained. On this basis, a series of 3D color maps of interference resistance (between main hull and outriggers) under different speeds and different displacement ratios are given to study the influence of the outrigger layout on the interference resistance. The results show that within an appropriate range, there is only one valley point of interference resistance exists in each 3D color map. For this reason, in combination with the characteristic of linear wave resistance has analytic expression, the steepest descent method can be applied to solve the problem of searching the outrigger layout with minimum wave resistance efficiently. Based on the above aspects, this paper proposes a fast trimaran outrigger layout resistance optimization method. By means of selecting an appropriate initial outrigger layout position, using trimaran wave resistance formula combined with steepest descent method, the minimum interference resistance layout in specific speed can be obtained efficiently. The results show a good precision of the optimal solution and an obvious promotion in computing efficiency compared to typical enumeration method.