Horizontal Shear Research Articles

Two Flavors of Intraseasonal Variability and Their Dynamics in the North Equatorial Current/Undercurrent Region

Significant surface-intensified and subsurface-intensified intraseasonal variability (ISV) of the North Equatorial Current/Undercurrent with different periods are detected to coexist with mooring ADCP measurements at 13°N, 130°E. The ISV of the currents in the upper 200 m has a relatively shorter period of 45 days, while the period of the subsurface-intensified ISV between 400 and 800 m is around 85 days. By combining with sea surface height measurements from satellite altimeters and outputs from an eddy-resolving ocean general circulation model, the origin and dynamic mechanism of the two flavors of ISV are investigated. Eddy trajectory tracking and energy analysis indicate that both the surface-intensified and subsurface-intensified ISV are related to locally generated meso-scale eddies near the mooring sites. Stability analysis suggests the surface-intensified ISV is related to the baroclinic instability induced by the vertical velocity shear of the North Equatorial Current. While the generation of the subsurface-intensified ISV is more complex and is partly related to the enhanced barotropic instability induced by the intensified horizontal shear of the subsurface zonal background flow.

Strut-and-tie model for FRP effectiveness in shear strengthening of RC deep beams

In this article, a strut-and-tie model (STM) is proposed for predicting the ultimate shear capacity of fiber reinforced polymers (FRP)-strengthened reinforced concrete deep beams. The proposed STM accounts for the effect of concrete strength, FRP ratio, ratio of main steel, horizontal and vertical stirrups ratio and shear span-to-depth ratio. The ultimate shear predictions of the proposed model are validated with 55 test results from the literature. The comparison showed that the proposed model performs well in predicting the ultimate shear capacity of FRP-strengthened RC deep beams. The overall average value of the ratio between the experimental capacity to the theoretical capacity of the proposed STM (Pu( EXP )/Pu( STM ) ) is of value 1.16 with a standard deviation of 0.18. Also, comparative studies between the proposed modified STM and the STM provided by the ACI code and other researchers in the literature are presented. Finally, FRP effectiveness studies are performed to study the effect of many structural parameters on the ratio between the ultimate strength for RC deep beams strengthened with FRP materials and the ultimate strength for ordinary RC deep beams. These parameters are FRP ratio (ƿ FRP), the fiber orientation angle to the longitudinal axis of the deep beam, material type of FRP, concrete compressive strength (fc ’) and the shear span-to-depth (a/d) ratio

Durability assessment of GFRP rebars in marine environments

Technologies developed over the last two decades have facilitated the use of glass fiber reinforced polymer (GFRP) bars as internal reinforcement for concrete structures, specially in coastal environments, mainly due to their corrosion resistance. To-date, most durability studies have focused on a single mechanical parameter (tensile strength) and a single aging environment (exposure to high alkalinity). However, knowledge gaps exists in understanding how other mechanical parameters and relevant conditioning environments may affect the durability of GFRP bars. To this end, this study assesses the durability for different physio-mechanical properties of GFRP rebars, post exposure to accelerated conditioning in seawater.Six different GFRP rebar types were submerged in seawater tanks, at various temperatures (23°C, 40°C and 60°C) for different time periods (60, 120, 210 and 365 days). In total six different physio-mechanical properties were assessed, including: tensile strength, E-modulus, transverse and horizontal shear strength, micro-structural composition and lastly, bond strength. It was inferred that rebars with high moisture absorption resulted in poor durability, in that it affected mainly the tensile strength. Based on the Arrhenius model, at 23°C all the rebars that met the acceptance criteria by ASTM D7957 are expected to retain 85% of the tensile strength capacity.

Tropical cyclogenesis associated with premonsoon climatological dryline over the Bay of Bengal

Tropical cyclones of the Bay of Bengal (BoB) that formed near the synoptic-scale dryline usually intensified over a distance of 600–800 km within 3 days and caused severe destruction after landfall. High-resolution simulations of very severe cyclonic storms in association with dryline indicate that the meridional shear aids in the development of a linear-shaped group of convective cells that mature as an east–west oriented quasi-linear convective system (QLCS) within the boundary between the dry-moist air masses. The leading edge deep convections are supported by low-level moist southwesterly inflow; however, the typical mid-level mesoscale convective vortex (MCV) associated with these QLCS is unremarkable due to a very narrow trailing stratiform region within the QLCS. Supercells are likely to be organized within the QLCS due to extremely unstable atmospheric conditions resulting from a strong vertical shear of 27–39 m s−1 between 0 and 6 km and large convective available potential energy of > 3000 J kg−1. The vertical shear veering with height causes several numbers of low-level mesovortices having diameters less than 10 km at the leading edge in the different convective stages of the QLCS. The dryline aloft in the BoB produces horizontal positive shear vorticity of the order 10–5 s−1 with higher values in the levels 850–600 hPa. The advection of intense cloud-scale cyclonic mesovortices (~ 10–3 s−1) assists and enhances a cyclonic vortex to the rear side of the QLCS that performs as an MCV for cyclogenesis over the BoB.

Flow dynamics in lateral vegetation cavities constructed by an array of emergent vegetation patches along the open-channel bank

The hydrodynamics in a straight rectangular open channel containing novel lateral cavities constructed by an array of square emergent vegetation patches discontinuously distributed along the bank were explored numerically using three-dimensional large eddy simulations (LES). Five vegetation densities (Φ), ranging from 0.02 to 0.25, as well as the traditional lateral cavities created by impermeable solid media, were tested. The effects of the cavity aspect ratio (AR) were also examined. The LES results showed that the mean recirculation pattern inside the vegetation cavities and coherent structures in the horizontal shear layer were closely dependent on Φ and AR. When Φ ≥ 0.06, a main recirculation vortex that formed inside the vegetation cavities resembled that within solid media cavities, whereas the extent of the former increased upstream as Φ increased. Compared with the solid cases, the vegetation cavities exhibited a higher turbulent intensity within the shear layer and wider regions of enhanced turbulent kinetic energy, which decreased with increasing Φ. The penetration depth of the elevated turbulent kinetic energy into the cavities also decreased with increasing Φ, whereas a deeper penetration was expected at larger AR values. The interfacial turbulence was dominated by “cavities field”-scale coherent vortices at Φ ≤ 0.06, whereas “cavity element”-scale at Φ ≥ 0.15. When Φ = 0.1, the shear vortices of both scales contributed to the enhancement of the interfacial turbulence. The mean mass exchange showed a non-monotonic relationship with Φ and reached maximum values at Φ = 1. The total momentum transport efficiency decreased monotonically with increasing Φ. Despite the AR and Φ values, the turbulent motions dominated the momentum transport over most of the cavity length.

Feasibility analysis of magnesium phosphate cement as a repair material for base slab of China railway track system II ballastless track

This study proposed using magnesium phosphate cement (MPC) to repair the base slab of the Chinese ballastless railway track. Laminated members were subjected to static and fatigue bending tests. Results showed that the damage to the laminated members was caused first by bending and then by horizontal shear at the interface between the old and new materials. Fatigue test results showed that the stress level on the base slab was below the endurance limit and thus should not cause failure. Microscopic tests also revealed that the bond between Portland cement and MPC played a crucial role in the repair process.

Depth-integrated wave–current models. Part 2. Current with an arbitrary profile

The depth-integrated wave–current models developed by Yang & Liu (J. Fluid Mech., vol. 883, 2020, A4) are extended to investigate currents with an arbitrary vertical profile in the water column. In the present models, horizontal velocities are decomposed into two components. The first part deduces the prescribed current velocity when waves are absent. The second part is approximated in a polynomial form. The resulting depth-integrated wave–current models are obtained by applying the weighted residual method. In the absence of currents, the present models are identical to those in Yang & Liu (J. Fluid Mech., vol. 883, 2020, A4) and are validated with several three-dimensional (3D) benchmark laboratory experiments. A theoretical analysis is conducted to study the frequency dispersion relation of linear waves on currents with an exponential vertical profile and the results are compared with numerical solutions of the Rayleigh equation. Using the new models, validations and investigations are then conducted for periodic waves and solitary waves on currents with an arbitrary profile in one-dimensional horizontal (1DH) space. Furthermore, the new models are applied to wave–current interactions in two-dimensional horizontal (2DH) space. Two scenarios are considered: (1) wave propagation over a vortex-ring-like current and (2) obliquely incident wave propagation over a 3D sheared current on a varying bathymetry. The vertical and horizontal shear of the current have significant effects on modifying various wave properties, which are well captured by the present models. However, the time-averaged velocity under wave–current interaction shows small differences with the prescribed current velocity, except in the region between the wave trough and crest.

Two water waves in subsurface interaction on a shear flow

Two plane-traveling water waves are superposed, with a background shear flow. The horizontal shear flow varies exponentially, with infinite depth. The present idea is to satisfy the two-dimensional vorticity equation for the second-order subsurface interaction between the two waves. The free-surface conditions are linearized, while the remaining (subsurface) nonlinearity has its amplitude set by the product of the two wave amplitudes. The first traveling wave is assumed steady, satisfying the same Helmholtz equation as the shear flow. Thereby, one single frequency enters the model, dictated by the second traveling wave. There are in total four wave components generated by subsurface interactions. Two of these are rotational waves arising from the exact quadratic interactions between the two first-order waves. The two other waves are compensational irrotational waves setup by linearized free-surface conditions, since the rotational waves alone are unable to satisfy these conditions.

Experimental study on seismic behaviour of eccentrically braced composite frame with vertical LYP steel shear link

An experimental investigation is conducted to study the seismic behaviour of eccentrically braced composite frame (EBCF) with vertical shear links, which has a better repairability and replaceability compared with traditional EBCFs with horizontal shear links. Particularly, the low-yield-point (LYP) steel is applied in the shear links to verified its influence on the seismic performance of the EBCFs. Cyclic loads are applied to two composite frames respectively with a bare moment resisting frame system and with a dual system composed of the moment resisting frame and the eccentric bracing system, the comparison of results indicates that the eccentric bracing system can effectively increase the stiffness, strength and energy dissipation capacity of the composite frame, but has few effects on the force conditions on the ends of the primary beams and columns, both two specimens failed by the fracture and buckling of the bottom flanges of the primary beams at a story drift ratio of 1/38. Due to the low-yield-point property and high ductility of the LYP steel, the shear link starts to efficiently dissipate energy when the story drift ratio is only 1/300, and the shear link has reached an inelastic rotation capacity of 0.16 before failure. However, due to the strain hardening of the LYP steel, the shear link achieved an over-strength factor up to 2.78, and the over-strength property of the shear link has resulted an unignorable bending moment of the middle segment of the primary beam, the concrete slab in this area is severely damaged with a maximum crack width of 0.16 mm. Finally, the analysis of working mechanism and test data indicates that, the added stiffness, added strength, and added energy dissipation capacity by the eccentric bracing system are directly in proportional to the contribution of the vertical shear link, and formulas to evaluate the added damage of concrete slab are also given.

Slip analysis of prestressed steel-concrete continuous composite beam

To analyze the horizontal shear resistance participation degree of the shear studs on the web and diaphragm flange in the negative moment area of the steel–concrete continuous composite box girder, the steel–concrete composite girder specimen was designed and manufactured based on the existing codes. The shear deformation of the two parts of the studs in the composite box girder is studied by the finite element parameter analysis of the nonlinear shear deformation of the studs and the stress analysis of the diaphragm. The results show that web flange studs provide the horizontal shear capacity of the steel–concrete composite box girder. The installation of baffle flange studs cannot improve the shear connection degree of composite beams. Removal of the flange stud from the diaphragm can relieve the force on the diaphragm and provide a theoretical basis for reducing the stiffeners of the diaphragm.

Overriding Plate Deformation and Topography During Slab Rollback and Slab Rollover: Insights From Subduction Experiments

AbstractSome subduction zones in nature show mainly overriding plate (OP) extension and low topography, and others show mainly shortening and elevated topography. Here we investigate how end‐member subduction modes (trench retreat with slab rollback and trench advance with slab rollover) affect overriding plate deformation (OPD), topography, and mantle flow with time‐evolving three‐dimensional fully‐dynamic analog models using particle image velocimetry. We conduct two sets of experiments, one of which is characterized by trench retreat, and the other characterized by trench advance. Experiments showing continuous trench retreat experience overall OP extension, while experiments dominated by trench advance experience overall shortening. Both subduction modes present fore‐arc shortening and intra‐arc extension. Our experiments indicate that the overall OPD is mainly driven by the horizontal mantle flow at the base of the OP inducing a viscous drag force (FD), and is determined by the horizontal gradient of the horizontal mantle shear rate , which controls the horizontal trench‐normal gradient in FD. Furthermore, a large‐scale trenchward OP tilting and overall subsidence are observed in the experiments showing continuous trench retreat, while a landward OP tilting and an overall uplift are observed during long‐term trench advance. The two types of topography during the two different subduction modes can be ascribed to the downward component of the large‐scale trenchward mantle flow and the upward component of the landward mantle flow, respectively, and thus represent forms of dynamic topography. Our models showing trench advance provide a possible mechanism for OPD and topography at the Makran subduction zone.

Observations and Modeling of a Buoyant Plume Exiting Into a Tidal Cross‐Flow and Exhibiting Along‐Front Instabilities

AbstractAerial image sequences of an ebbing river plume propagating into a tidal cross‐flow demonstrate the presence of along‐front instabilities at multiple scales, which appear to propagate along‐front in the direction of the shear flow. We hypothesize the instabilities are due to cross‐front shear in the along‐front velocity field. Image analysis quantifies the horizontal shear across the plume front as well as the length scales and propagation speeds of the instabilities. In situ measurements from cross‐front ship transects are also used to examine shear and the width of the shear layer. A non‐hydrostatic numerical simulation of an ebb plume in an idealized tidal cross‐flow was conducted using comparable flow parameters and confirms the presence of shear instabilities. An additional numerical simulation without a tidal‐cross flow demonstrates that shear instabilities are not present; rather, lobe‐and‐cleft structures on the nose of the gravity current emerge. According to the scaling of White and Helfrich (2013), utilizing both the observed and modeled parameters, it is shown that shear instabilities are likely in the observed and modeled cross‐flow scenario, and confirms that they are unlikely to emerge in the no cross‐flow model case.

Comparative Study of Seismic Design for Different Bridges Structures

The main objective of this study is to compare the structural members capacity between different types of bridges structures under seismic load. The results of seismic modal analysis showed that the models of box girder bridge, precast T girder bridge, and U steel girder bridge had the higher values of natural frequency comparing with others bridges structures under seismic load. Pushover analysis in transvers direction showed that bent No. 2 of bridges structures which was located in the middle of bridges superstructure was displaced in transvers direction more than bent No. 1 and bent No. 3. In longitudinal direction, Precast I girder bridge had higher value of longitudinal displacement comparing with others bridges structures, and it was more than the maximum value of transvers displacement. The results of demand and capacity ratio showed that bent No. 2 was the critical structural member which had values of demand/capacity ratio more than 1.0 or near from it especially precast I girder bridge, precast T girder bridge, and U steel bridge, indicating that these types of bridges will be subjected to failure in bent No. 2. Therefore, there was needing to redesign the bents of these types of bridges by increasing the numbers of piers, using high strength materials in construction of bents, and increasing of dimensions of piers and pier caps. The results of internal forces showed that bent No. 2 was subjected to the maximum values of axial force, horizontal shear, and bending moment for all types of bridges structures. Also, it can be seen that the models of precast I girder bridge, precast T girder bridge, and U steel bridge had the higher values of forces comparing to others models, indicating that these results agree with results of demand/capacity ratio and pushover analysis method.

Comparing the Currents Measured by CARTHE, CODE and SVP Drifters as a Function of Wind and Wave Conditions in the Southwestern Mediterranean Sea.

Instruments drifting at the ocean surface are quasi-Lagrangian, that is, they do not follow exactly the near-surface ocean currents. The currents measured by three commonly-used drifters (CARTHE, CODE and SVP) are compared in a wide range of sea state conditions (winds up to 17 m/s and significant wave height up to 3 m). Nearly collocated and simultaneous drifter measurements in the southwestern Mediterranean reveal that the CARTHE and CODE drifters measure the currents in the first meter below the surface in approximately the same way. When compared to SVP drogued at 15 m nominal depth, the CODE and CARTHE currents are essentially downwind (and down-wave), with a typical speed of 0.5–1% of the wind speed. However, there is a large scatter in velocity differences between CODE/CARTHE and SVP for all wind and sea state conditions encountered, principally due to vertical and horizontal shears not related to the wind. For the CODE drifter with wind speed larger than 10 m/s and significant wave height larger than 1 m, about 30–40% of this difference can be explained by Stokes drift.

Structural behavior of high-strength concrete corbels involving steel fibers or closed stirrups

A comprehensive experimental evaluation of the shear behavior of corbels made by high-strength concrete (HSC) with steel fiber or with stirrups was investigated. Thirteen samples were prepared and tested, the main variables in this research were steel fiber type, steel fiber content (Vf %), and amount of horizontal closed stirrups (Ah). The constants in this investigation were the area of the main steel reinforcement (As), ratio of shear span to depth (a/d) and cube concrete strength (fcu). The obtained results clearly showed that, the presence of fibers or closed stirrups enhanced the strength and decreased the deformation of the explored specimens. It was concluded that the horizontal shear reinforcement can be substituted by supplementation of steel fibers to RHSC corbels. A comparison was performed between the test results and estimated shear capacity by ACI code and other adopted equations. Very conservative shear strength values were obtained from ACI 318–19 for corbels prepared with high-strength concrete because the strut and tie method were influenced by concrete strength and did not take the contribution of closed stirrups into account. However, the shear friction method depends only on the quantity of the main steel reinforcement and closed stirrups. Russo [2] proposed a model that adequately predicted the ultimate force of high-strength RC corbels incorporating closed stirrups, but this model did not take the effect of steel fibers into account. Campione [3] added the effect of steel fibers by means of the residual tensile strength expression.

The behavior of self compacting concrete exterior beam-column joints with a variation of shear reinforcement against cyclic lateral loads

The beam-column joints are designed to have sufficient capacity under earthquake loads. This requirement needs design details of reinforcement that fulfill the seismic criteria and adequate compaction of concrete. Using Self Compacting Concrete (SCC) material can solve the difficulty of compacting conventional concrete due to the close reinforcement distance. This study aimed to analyze the behavior of the Exterior Beam-column Joints (EBJ) using SCC as materials with a variation of shear reinforcements to withstand cyclic lateral loads. The analysis was carried out using the ANSYS software and the Finite Element Method. The analysis included hysteresis curves, stress contours, ductility, stiffness, and structural strength. The performance of an EBJ without shear reinforcement (EBJ-S1 model) was compared to other EBJs using horizontal (EBJ-S2 model) and diagonal (EBJ-S3 model) shear reinforcements in the joint zones. The results showed that horizontal and diagonal shear reinforcement in the joint zones affected the performance of the EBJs in resisting cyclic lateral loads as the representative of earthquake loads. The EBJ without shear reinforcement could withstand compressive stresses of 3.33 to 17.22 MPa, while both EBJs using horizontal and diagonal shear reinforcement achieved the same compressive stresses range of 3.33 to 20 MPa. The EBJ with diagonal reinforcement performed a wider compressive area of stress contour than the EBJ of horizontal reinforcement. The EBJ-S3 model achieved the highest ductility value of 4.733 with diagonal shear reinforcements because it achieved the highest ultimate displacement of the other EBJ models.

VISPNN: VGG-inspired Stochastic Pooling Neural Network.

Alcoholism is a disease that a patient becomes dependent or addicted to alcohol. This paper aims to design a novel artificial intelligence model that can recognize alcoholism more accurately. We propose the VGG-Inspired stochastic pooling neural network (VISPNN) model based on three components: (i) a VGG-inspired mainstay network, (ii) the stochastic pooling technique, which aims to outperform traditional max pooling and average pooling, and (iii) an improved 20-way data augmentation (Gaussian noise, salt-and-pepper noise, speckle noise, Poisson noise, horizontal shear, vertical shear, rotation, Gamma correction, random translation, and scaling on both raw image and its horizontally mirrored image). In addition, two networks (Net-I and Net-II) are proposed in ablation studies. Net-I is based on VISPNN by replacing stochastic pooling with ordinary max pooling. Net-II removes the 20-way data augmentation. The results by ten runs of 10-fold cross-validation show that our VISPNN model gains a sensitivity of 97.98±1.32, a specificity of 97.80±1.35, a precision of 97.78±1.35, an accuracy of 97.89±1.11, an F1 score of 97.87±1.12, an MCC of 95.79±2.22, an FMI of 97.88±1.12, and an AUC of 0.9849, respectively. The performance of our VISPNN model is better than two internal networks (Net-I and Net-II) and ten state-of-the-art alcoholism recognition methods.

Tornadogenesis in a Quasi-Linear Convective System over Kanto Plain in Japan: A Numerical Case Study

Abstract The environmental characteristics and formation process of a tornado spawned by a quasi-linear convective system (QLCS) over Kanto Plain, Japan, are examined using observations, a reanalysis dataset, and a high-resolution numerical simulation with a horizontal grid spacing of 50 m. The QLCS environment responsible for tornadogenesis was characterized by small convective available potential energy and large storm-relative environmental helicity due to strong vertical shear associated with a low-level jet. The strong low-level jet was associated with a large zonal pressure gradient between two meridionally aligned extratropical cyclones and a synoptic-scale high pressure system to the east. The numerical simulation reproduced the tornado in the central part of the QLCS. Before the tornadogenesis, three mesovortices developed that were meridionally aligned at 500-m height, and a rear inflow jet (RIJ) associated with relatively cold air originated from aloft and developed on the west side of the QLCS, while descending from rear to front. Tornadogenesis occurred in the southernmost mesovortex at the northern tip of the RIJ. This mesovortex induces strong low-level updrafts through vertical pressure gradient force. A circulation analysis and vorticity budget analysis for the mesovortex show that environmental crosswise vorticity in the forward inflow region east of the QLCS played a significant role in the formation of the mesovortex. The circulation analysis for the tornado shows that frictional effects contribute to the increase of circulation associated with the tornado. Moreover, environmental shear associated with horizontal and vertical shear of the horizontal wind also contribute to the circulation of the tornado.

Tilt-Up Partially Composite Insulated Wall Panels

This research project was initiated to investigate the behavior of load-bearing concrete insulated wall (CIP) panels for use in tilt-up construction. The primary objective was to understand the inelastic behavior of these panels so that engineers could perform a proper second-order analysis for combined axial and out-of-plane loading. Toward this aim, the Tilt-up Concrete Institute (TCA) and wythe connector suppliers Innstruct, Thermomass, HK Composites, Dayton Superior, and IconX, funded this study. Since tilt-up panel testing of similar scope had not been done since the 1980s on panels of lower height, there were several goals for this testing. This represented an opportunity to validate the current ACI code alternate slender wall analysis method and provide a set of control panels for testing solid tilt-up panel behavior. Testing solid panels and CIPs of 40 ft span, a length typical of contemporary construction, was critical so that such slenderness ratios could be observed and significant second-order panel behavior could be identified. As part of this, the research team created a modified version of the slender wall design method to predict second-order load and deflection behavior in the post-cracking range in CIPs. For solid panels, the 1980s testing program popularized the “slender wall design method” outlined in ACI 551 and the goal of this newer methodologies is to do the same for CIPs. Additionally, horizontal shear failure analysis methods were investigated to enable design against such failures.

Longitudinal shear bond strength of profiled deck composite slab: An experimental and analytical investigation

In recent years, composite slabs with concrete topping and profiled/ re-entrant decking sheets have gained popularity as they are faster, more economical, and lightweight construction techniques. In a composite floor, profiled/re-entrant decking sheets serve a dual purpose: they serve as permanent formwork during the construction phase and as main reinforcement after the concrete topping has hardened. Horizontal shear bond strength is a crucial parameter in the design of the composite floor. Presently, the m-k and PSC methods are the most commonly used techniques to calculate the horizontal shear bond strength of the composite slab. In this study, four full-scale composite slabs were cast and tested for four distinct shear spans under four-point loading conditions. The influence of shear span was investigated. Short and long shear span specimens were investigated. Three alternative approaches (the modified partial shear connection method, the force equilibrium method, and the composite beam partial shear connection method) were adopted to evaluate the horizontal shear bond strength of the profiled deck composite slab. Load- displacement behavior, horizontal shear bond strength, and failure modes were used to assess the structural performance of composite slab specimens. The results of all three methods were compared. The horizontal shear bond stress evaluated by the slenderness and force equilibrium methods were in close agreement, whereas the composite beam partial shear connection method approach may underestimate the longitudinal shear bond strength, but it may still be employed as an alternative method.