Horizontal Shear Research Articles

Analysis of cyclic shear characteristics of reinforced soil interfaces under cyclic loading and unloading

The cyclic properties of geosynthetic soil interface are crucial for reinforced soil structures subject to seismic loading. A series of cyclic direct tests under cyclic normal loading was conducted on geogrid-gravel interface. The relationship among the amplitudes of cyclic normal loading and shear displacement and frequencies in the horizontal and vertical directions with interface shear strength and volume change was investigated. Test results showed that the relative time shift, shear stiffness, and enhance coefficient increased with increasing amplitude of cyclic normal loading. The interface exhibited shear hardening and softening with increasing amplitude of shear displacement. The vertical displacement decreased with increasing amplitude of cyclic normal loading but increased with increasing amplitude of shear displacement. Furthermore, three patterns were analysed for different frequencies in two loading directions. The value of vertical displacement was largest when the normal loading impact frequency was larger than the cyclic horizontal shear frequency, and smallest at equal frequencies in two loading directions. The shear stiffness was positively correlated with the amplitude of cyclic normal loading. However, it was negatively correlated with the amplitude of shear displacement. The value of the damping ratio was smallest under constant normal loading at a shear displacement amplitude of 0.5 mm.

Analysis of Mesovortex Characteristics, Behavior, and Interactions during the Second 30 June-1 July 2014 Midwestern Derecho Event

A pair of intense, derecho-producing quasi-linear convective systems (QLCSs) impacted northern Illinois and northern Indiana during the evening hours of 30 June through the predawn hours of 1 July 2014. The second QLCS trailed the first one by only 250 km and approximately 3 h, yet produced 29 confirmed tornadoes and numerous areas of nontornadic wind damage estimated to be caused by 30‒40 m s‒1 flow. Much of the damage from the second QLCS was associated with a series of 38 mesovortices, with up to 15 mesovortices ongoing simultaneously. Many complex behaviors were documented in the mesovortices, including: a binary (Fujiwhara) interaction, the splitting of a large mesovortex in two followed by prolific tornado production, cyclic mesovortexgenesis in the remains of a large mesovortex, and a satellite interaction of three small mesovortices around a larger parent mesovortex. A detailed radar analysis indicates no definitive differences between tornadic and nontornadic mesovortices. All observed mesovortices were cyclonic, indicating that either the vertical tilting of streamwise vorticity, generation of vortices via the release of horizontal shearing instability, or both were involved in mesovortex genesis. This paper examines the environment ahead of the second QLCS, the characteristics of the mesovortices produced, and the aforementioned complex interactions. It also discusses implications for mesovortex genesis and dynamics as well as operational considerations.

Operational Uses of Spectrum Width

Spectrum width is a WSR-88D product that has been available to operational forecasters since the radar was deployed. In 2008, super-high-resolution reflectivity, velocity and spectrum width data became available. Six cases exemplifying operational use of spectrum width are presented; five are from after the upgrade. The cases were selected to depict the wide array of uses of spectrum width (SW). In one case, use of SW improved forecaster capability to evaluate the strength of horizontal shear within a bow echo’s mesovortex. One case shows that SW can be extremely helpful in determining location of boundaries, which aids in overall situational awareness. In another case, SW aided forecaster confidence to issue a tornado warning with lead time. If a storm is close to the radar (55 km in this example), SW can be used to clarify the location of the rear flank downdraft, assess where its wind damage may be a threat, and discern subsequent cutoff of the tornado from the warm, moist inflow. Finally, when used in a derecho case, SW helped a forecaster to identify more quickly where wind damage threats were likely.

Micromechanical modeling of ultrasonic velocity for pore-structure and porosity characterization considering anisotropy in carbonate samples

This work presents an approach to characterize the pore-structure and anisotropy in carbonate samples based on the Effective Medium Method (EMM). It considers a matrix with spheroidal inclusions which induce a transverse anisotropy. The compressional wave (VP), vertical (VSV) and horizontal (VSH) shear wave velocities are estimated taking into account parameters as characteristic length, frequency, angle of wave incidence, aspect ratio, mineralogy, and pore-filling fluid to predict pore shape in carbonates. Ranges of aspect ratios are shown to discriminate different pore types: intercrystalline, intergranular, moldic, and vuggy. The angle of wave incidence is a determinant parameter in the estimation of VP(0º, 45º, 90º), VSV(0º) and VSH(90º) to calculate dynamic anisotropic Young’s modulus (E33) and Poisson’s ratio (v31), as well as the Thomsen parameters, Epsilon, Gamma and Delta for quantification of the anisotropic pore-structure. The obtained results establish that the size, as well as the pore-structure, have a more significant impact on the elastic properties when the porosity takes values greater than 4% for the three frequencies, ultrasonic, sonic, and seismic. This investigation predicts the pore-structure and pore-size to improve characterization and elastic properties modeling of carbonate reservoirs. Validation of results includes porosity measurements and ultrasonic velocity data for different carbonate samples.

Development and application of triaxial rock shear - self-supporting fracture conductivity experiment system

The structure and function of shear - self-supporting fracture conductivity test device in great detail were presented. This device system consists of five parts: vertical loading system, horizontal shear loading system, the servo control system, power system, shear box and its sealing system, digital control and acquisition system. It can provide vertical force up to 2000KN, shear force 500KN, lateral stress 50MPa and hydraulic pressure 40 MPa. Characteristics of the system are illustrated as follows. (1) The experimental research of rock shear failure can be performed under three axial stress conditions, the lateral stress is loaded by hydraulic oil and the vertical stress is loaded by pressing machine. (2) True triaxial and quasi-triaxial loading modes can be switched by using different sealing sleeves. (3) The shear seepage coupling and self-supporting fracture conductivity tests could be conducted under three axial stress conditions. (4) The stress and displacement loading modes under different loading rate can be realized by servo system. Based on this experimental system, shear - fracture conductivity test under three axial stress conditions was performed on shale specimen and its reliability was verified. The experimental system can be used to provide theoretical basis for the shear destruction mechanism and Self-supporting shear fracture conductivity test under true triaxial stress conditions. The research has an important guiding significance on the formation mechanism of unconventional reservoir shear fracture and the flow capacity of self-supporting shear fracture and its influencing factors.

Synoptic‐scale and mesoscale controls for tornadogenesis on cold fronts: Shear‐zone vortex‐genesis in a developing frontal wave

AbstractHigh‐resolution model simulations and radar observations are used to investigate the onset of vortex‐genesis in a tornadic narrow cold‐frontal rain band (NCFR). The timing and location of vortex‐genesis was strongly constrained by a developing frontal wave, which tracked northeast across the United Kingdom and Ireland on 17 October 2011. In the simulations, vortices occurred preferentially during the early stages of wave development and just down‐front of the wave centre, where large increases in vertical vorticity occurred in concert with decreases in the cross‐frontal confluence. Vortex‐genesis ceased as the frontal wave matured, due to the onset of frontal fracture. Two distinct scales of vortex‐genesis are documented: primary vortex‐genesis on the meso‐γ‐scale, and secondary vortex‐genesis on the miso‐scale. We show that horizontal shearing instability is the most likely vortex‐genesis mechanism, consistent with previous theoretical work on the stability of vertical vortex strips in the presence of horizontal stretching deformation. Secondary vortices occurred along the braid regions between primary vortices where the shear zone became particularly narrow and intense. In the model, these vortices developed extremely rapidly (from small perturbations to maximum vertical vorticity in 5–15 min) and the strongest exhibited near‐surface vertical vorticity maxima approaching 10−1 s−1. Vortices of both scales were associated with characteristic local perturbations in the NCFR and we show, by comparison with radar reflectivity data, that primary and secondary vortices were likely present in the real NCFR. Tornado reports were associated with small NCFR perturbations like those associated with the secondary vortices in the model simulations. Analysis of the sub‐structure of individual simulated vortices suggests that tornado‐genesis is most likely within a region of intense near‐surface vertical vorticity stretching at the north or northwest flank of the secondary vortices.

Pull-Out and Shear Tests of Long Glass FRP Connector for Sandwich-Insulation Wall Panels

Sandwich insulation wall panels (SIWPs) are used extensively as thermal resistance components in buildings. Connectors in SIWPs are subjected to axial and shear forces to resist the load of the outer layer and transfer it to the inner layer and structure. In some areas, the insulation thickness needs to increase to achieve a satisfactory heat preservation effect, which leads to an increase in connector length. Most existing connectors do not satisfy the mechanical requirements for a thick insulation layer, e.g., 300 mm. In this work, a series of pull-out and shear tests were conducted for a novel long glass fiber-reinforced polymer I-shaped connector. The ply design and anchorage design of the connectors are key factors that affect the connector’s mechanical properties. Through comparative tests, the influence of these two factors on the axial and shear stiffness, capacity, and failure mode were explored. The addition of ±45° and 0°/90° multiaxial fiber cloth had little effect on axial performance, but the vertical shear stiffness and horizontal shear capacity improved. The pull-out and vertical shear capacity can be improved by optimizing the anchorage design and adding a row of anchorage rebar in the flange.

Case Study of a Long-lived Tornadic Mesocyclone in a Low-CAPE Complex-terrain Environment

On 22 May 2008 a long-lived mesocyclone spawned an EF2 tornado over terrain as high as 2650 m MSL in southeastern Wyoming. The mesocyclone was part of an elongated, complex storm system that grew rather early in the day near a slow-moving warm front. The mesocyclone is unusual in that it persisted and became tornadic in rather cold (~7°C), saturated surface conditions in an environment with CAPE < 1000 J kg-1 and no surface-based convective inhibition. The mesocyclone intensified as its parent storm moved over terrain gradually ascending by ~1000 m, reaching a radar-estimated low-level horizontal shear as high as 84 m s-1 km-1. This fast-moving mesocyclone could be tracked by the nearest Doppler radar for over 90 min.
 This paper examines the characteristics and the environment of this mesocyclone using both operational weather data and high-resolution numerical simulations. Near-surface radar observations and model output suggest that the formation and maintenance of the mesocyclone in this low-CAPE environment benefited from two terrain-related factors. One is the observed channeling of the low-level flow, locally enhancing the storm-relative helicity. The second is the presence, suggested by high-resolution simulations, of banners of high potential vorticity generated by the strong southerly flow shearing around the Colorado Front Range.

3D sine wave‐like geometry of soft sediment deformation structures: Possible record of the Late Pleistocene seismic activity over the Teisseyre‐Tornquist Zone

AbstractRemarkably regular load structures are recognised in the late Vistulian (~15 ka BP) fluvial deposits exposed at the Gołąb site (eastern Poland). A mud layer, sandwiched between non‐deformed sand, exhibits the unusual morphology of a 3D sine wave with parallel crests and troughs. Such structures are reported for the first time, remarkably differing from those previously described as having perfect linearity, which could be caused by horizontal shear affecting previously liquefied sediments or by lateral migration of the sediment liquefaction front. The deformation could be triggered by either seismic shock, loading by flood waters or periglacial processes. Seismicity of the study area is evident which supports the seismogenic hypothesis.

Numerical analysis of hydrodynamics influenced by a deformed bed due to a near-bank vegetation patch

Abstract This study uses a 2D hydro-morphological model to analyze hydrodynamics over flat and deformed beds with a near-bank vegetation patch. By varying the patch density, the generalized results show that the hydrodynamics over deformed beds differs a lot from those over flat beds. It is found that the deformed bed topography leads to an apparent decrease in longitudinal velocity and bed shear stress in the open region and longitudinal surface gradient for the entire vegetated reach. However, the transverse flow motion and transverse surface gradient in the region of the leading edge and trailing edge is enhanced or maintained, suggesting the strengthening of secondary flow motion. Interestingly, the deformed bed topography tends to alleviate the horizontal shear caused by the junction-interface horizontal coherent vortices, indicating that the turbulence-induced flow mixing is highly inhibited as the bed is deformed. The interior flow adjustment through the patch for the deformed bed requires a shorter distance, La, which is related to the vegetative drag length, (Cda)−1, with a logarithmic formula (La = 0.4ln[(Cda)−1] + b, with b = 3.83 and 4.03 for the deformed and flat beds). The sloping bed topographic effect in the open region accelerating the flow may account for the quick flow adjustment.

Evolution of the Horizontal Winds in Jupiter's Great Red Spot From One Jovian Year of HST/WFC3 Maps

AbstractWe measured the horizontal winds in Jupiter's Great Red Spot (GRS) using data from the WFC3/UVIS instrument on board the Hubble Space Telescope (HST). The data cover 11 epochs from 2009 to 2020. Long‐term monotonic trends in size and shape previously noted from the visible cloud appearance are paralleled by changes in the high‐speed ring around the vortex. The circularization of the GRS cannot be explained by changes in the horizontal wind shear of the surrounding environment. The velocity fields suggest no long‐term trend in the static stability inside or outside the vortex. Instead, the changes are accompanied by a 4%–8% increase in the mean wind speeds of the high‐speed ring from 2009 to 2020. Changes in the wind field coincided with the South Equatorial Belt Outbreak storms of 2016–2017, but not with 2019 "flaking" events involving detachment of red material from the main oval.

Crustal deformation and exhumation within the India-Eurasia oblique convergence zone: New insights from the Ailao Shan-Red River shear zone

Abstract During the collision of India and Eurasia, regional-scale strike-slip shear zones played a key role in accommodating lateral extrusion of blocks, block rotation, and vertical exhumation of metamorphic rocks as presented by deformation on the Ailao Shan-Red River shear zone (ARSZ) in the Eastern Himalayan Syntaxis region and western Yunnan, China. We report structural, mica Ar/Ar, apatite fission-track (AFT), and apatite (U-Th)/He (AHe) data from the Diancangshan massif in the middle segment of the ARSZ. These structural data reveal that the massif forms a region-scale antiform, bordered by two branches of the ARSZ along its eastern and western margins. Structural evidence for partial melting in the horizontal mylonites in the gneiss core document that the gneiss experienced a horizontal shear deformation in the middle crust. Muscovite Ar/Ar ages of 36–29 Ma from the core represent cooling ages. Muscovite Ar/Ar ages of 25 and 17 Ma from greenschist-facies mylonites along the western and southern shear zones, respectively, are interpreted as recording deformation in the ARSZ. The AFT ages, ranging from 15 to 5 Ma, represent a quiescent gap with a slow cooling/exhumation in the massif. AHe results suggest that a rapid cooling and final exhumation episode of the massif could have started before 3.2 Ma, or likely ca. 5 Ma, and continue to the present. The high-temperature horizontal shearing layers of the core were first formed across the Indochina Block, locally antiformed along the tectonic boundaries, and then cooled through the mica Ar-Ar closure temperature during Eocene or early Oligocene, subsequently reworked and further exhumed by sinistral strike-slip movement along the ARSZ during the early Oligocene (ca. 29 Ma), lasting until ca. 17 Ma, then final exhumation of the massif occurred by dextral normal faulting on the Weixi-Qiaohou and Red River faults along the limbs of the ARSZ since ca. 5 Ma. The formation of the antiform could indicate local crustal thickening in an early transpressional setting corresponding to India-Asia convergence. Large-scale sinistral ductile shear along the ARSZ in the shallow crust accommodated lateral extrusion of the Indochina Block, and further contributed to the vertical exhumation of the metamorphic massif from the late Oligocene to the middle Miocene. Furthermore, the change of kinematic reversal and associated cooling episodes along the ARSZ since the middle Miocene or early Pliocene imply a tectonic transfer from strain localization along the major tectonic boundaries to continuous deformation corresponding to plateau growth and expansion.

Modeling Ice‐Crystal Fabric as a Proxy for Ice‐Stream Stability

AbstractThe crystal structure within an ice sheet evolves in response to deformation; hence ice‐crystal fabric records ice‐flow history. However, the complexity of crystal‐fabric evolution, and the lack of model results with which to compare data, limit the usefulness of fabric measurements, particularly in areas with complex ice dynamics. Here, we use an ice‐flow model to identify characteristic fabrics associated with ice‐stream onset, with the goal of aiding interpretation of fabric measurements. Using time‐dependent model simulations, we identify how crystal fabric may be used to diagnose changes in an ice stream's speed or lateral position. Consistent with previous work, we find that fabric within an ice stream is generally a vertical girdle, though horizontal shear can lead to a horizontal single maximum. Transient simulations demonstrate that effects from changes in flow may be recorded in the crystal fabric for thousands of years after an ice stream activates and more than ten thousand years after an ice stream stagnates. Both transient and steady effects on fabric are sufficiently large as to be measurable in ice cores or with polarized radar, suggesting that in certain scenarios fabric could be used to identify past flow changes. These results could be used to design radar surveys in areas where ice streams are known to deactivate, such as the Siple Coast in Antarctica, or where they may migrate laterally or widen, such as in Northeast Greenland.

Mode-one internal tides propagating across a geostrophic current

As a mode-1 internal tide (IT) propagates across a geostrophic current V(x, z), we have investigated the amount of IT energy reflected from the current and the impact of the current on the transmitted wave field. These are quantified by considering the reflection coefficient R and the linear modal energy conversion Pn, where n is the modal number. Here, a linear theory built upon idealized barotropic currents is presented. Fully nonlinear numerical simulations are used for the baroclinic currents. We conclude that the reflection is determined by the horizontal shear of the current Vx through varying the effective frequency feff. The modal energy conversion Pn is determined by the vertical shear of the current Vz, i.e., the horizontal variation of the density ρx as a result of the thermal wind relation. The current can increase R up to around 50%. However, Pn is less than 6% among all our simulations. This indicates that IT can propagate through the current without losing much of its structure and the interaction is mostly linear.

Meander Response of the Kuroshio in the East China Sea to Impinging Eddies

AbstractBoth observations and an idealized model demonstrate that the path of a western boundary current, like the Kuroshio, can be perturbed by the impingement of an ocean eddy. When a strong cyclonic (anti‐cyclonic) eddy approaches the axis of the Kuroshio in the East China Sea, the current path can be repelled (attracted) by the eddy. The subsequent disruption occurs primarily near the interaction region and propagates downstream, forming a dissipating wavelike fluctuation. The spatial‐temporal evolution of Kuroshio axis shift by impinging eddy can be explained by idealized vorticity dynamics on the current‐eddy interaction process, and the magnitude of current path shift is shown to be determined by two nondimensional factors: the ratio of eddy strength to the Kuroshio strength; and the ratio of horizontal shearing strength in the background to that in the current.

Seismic behavior of large-size encased cross-section steel-reinforced high-strength concrete circular columns

Steel-reinforced high-strength concrete (SRHSC) columns can resist large percentages of horizontal shear forces and axial loads, and are widely used in super high-rise buildings. To investigate the effects of the axial load ratio, steel ratio, and loading direction on the seismic performances of encased cross-section SRHSC circular columns, a low-cyclic loading test was conducted on four large-sized specimens, each with a diameter of 700 mm. The failure characteristics, hysteresis curves, bearing capacity, deformation, stiffness degradation, and energy dissipation were analyzed. The finite element software OpenSEES (based on fiber elements) was used to simulate the hysteretic curves of the test specimens, and the simulated results were in good agreement with the test results. The results indicate that all four specimens show bending-dominated damage characteristics. The axial load ratio has a significant influence on the peak load, ductility, and deformation capacity. By increasing the steel ratio, the stiffness degrades more slowly and the specimen shows a better seismic energy dissipation performance. The effect of steel ratio on the improvement of peak load is more evident under a low axial load. With increasing steel strength, there is no significant effect on the initial stiffness and ductility. The specimens with different loading directions have balanced seismic performance, therefore, the columns are suitable for structures in seismic regions. There is little difference between the results calculated by the code of China and Europe and the test results, but the results calculated by the code of China are in better agreement.

Influence of Four Ageing Methods on the Mechanical Properties of Bamboo Scrimber

In this study, the six-cycle accelerated ageing method (method I), the 6 h boiling-freezing-drying method (method II), the wet circulation method (method III), and the boiling-testing method (method IV), which are accelerated ageing testing methods, were used to study the ageing resistance of bamboo scrimber. Changes in the nail-holding power of the plane, the side, and the end face of untreated/treated bamboo scrimber were analyzed systematically, including other changes in mechanical properties, such as the horizontal shear strength, the modulus of rupture (MOR), and the modulus of elasticity (MOE) along the smooth grain, etc. The results show that all mechanical properties decreased after treatment with the four accelerated ageing testing methods: the nail-holding power decreased by 4%~42% on the plane, 8%~40% on the side, and 5%~66% on the end face. The horizontal shear strength decreased by 3.1%~16.7%, the MOR decreased by 15%~27.2%, and the MOE decreased by 2.6%~12.8%. The nail-holding power of the three sides and the MOR were the most affected properties after treatment. So, the nail-holding power and the MOR can be chosen as important indices to evaluate bamboo scrimber’s weather resistance. For the four accelerated ageing testing methods, the degree of influence on the nail-holding power was in this sequence: method I > method III > method IV > method II. However, after comprehensive consideration, the degree of influence on the mechanical properties was in this sequence: method I > method IV > method III > method II.

Performance Enhancement by Wing Sweep for High-Speed Dynamic Soaring

Dynamic soaring is a flight mode that uniquely enables high speeds without an engine. This is possible in a horizontal shear wind that comprises a thin layer and a large wind speed. It is shown that the speeds reachable by modern gliders approach the upper subsonic Mach number region where compressibility effects become significant, with the result that the compressibility-related drag rise yields a limitation for the achievable maximum speed. To overcome this limitation, wing sweep is considered an appropriate means. The effect of wing sweep on the relevant aerodynamic characteristics for glider type wings is addressed. A 3-degrees-of-freedom dynamics model and an energy-based model of the vehicle are developed in order to solve the maximum-speed problem with regard to the effect of the compressibility-related drag rise. Analytic solutions are derived so that generally valid results are achieved concerning the effects of wing sweep on the speed performance. Thus, it is shown that the maximum speed achievable with swept wing configurations can be increased. The improvement is small for sweep angles up to around 15 deg and shows a progressive increase thereafter. As a result, wing sweep has potential for enhancing the maximum-speed performance in high-speed dynamic soaring.

Investigation the iron ore fine granulation effects and particle adhesion behavior in a horizontal high-shear granulator

This work presents a study of the granulation of iron fines in a horizontal high shear granulator. Both experiments and DEM simulations were conducted to investigate the effect of water content, impeller rotational speed and particle sizes on granulation performance. The experimental results showed that the granule size increased with increasing water content, but the granules had the most uniform size at 8% of water content. The DEM model was developed to understand the inter-particle force, particle motion and adhesion during granulating. The results show that the liquid bridge force and the amount of bonded small particles increased with increasing water content, resulting in larger granules with wider granule size distributions. Increasing impeller speed also increased granulation efficiency due to increased collisions between particles. The simulation of the granulation of particles with different size ratios showed that granulation efficiency increased with increasing size ratios of nucleating and adhesive particles.

Mechanical characteristics and deformation calculation of steel diagrid structures in high-rise buildings

In order to propose a simple and practical methodology for calculating the deformation of diagrid structure with polygon plane in arbitrary direction, the diagrid structure is considered to be mainly composed of “element” by geometric method. The vertical stiffness and lateral stiffness of diagrid structure with arbitrary polygon plane under vertical load and horizontal load are derived respectively. The corresponding laboratory test and numerical simulation analysis are carried out through the scale models of steel diagrid structures. The analysis results show that the calculated results of each deformation equation are in good agreement with the test results and numerical simulation results. In addition, the influence of the parameters on the stiffness of the structure is revealed theoretically. The results demonstrate that when the diagonal angle is about 55°, the variation of the diagonal angle has the greatest effect on the vertical stiffness of the diagrid structure. Moreover, the vertical stiffness of steel diagrid structure is smaller than that of traditional structure, and the vertical displacement is obviously larger. It is necessary to limit the inter-story drift ratio of vertical modules. Furthermore, current paper theoretically explains that the more edges of diagrid structure, the greater the horizontal shear stiffness of the structure.