Horizontal Shear Stress Research Articles

Prediction of Traffic Loading–Induced Settlement of Low-Embankment Road on Soft Subsoil

AbstractPrediction of subsoil deformation under traffic loading requires honoring the dynamic nature of moving wheel loads and representing the stress path caused by such loads. A practical method in the framework of the layerwise summation procedure is proposed here for predicting the settlement of road overlaid on soft subsoil caused by traffic loading. The proposed method consists of a simplified approach for calculating the wheel load–induced stress and an empirical model for describing the accumulation of residual strain. Two amplification coefficients are introduced to account for the effect of moving speed on deviator stress and horizontal shear stress, respectively. The analytical solutions of the two amplification coefficients, which can be evaluated numerically, are deduced, and numerical results are presented in charts. Hence, the wheel load–induced stress in subsoil at different moving speeds can be calculated by multiplying the stress from a commonly used pseudostatic method with the values o...

Deformation characteristics of overconsolidated clay sheared under constant and variable confining pressure

The traffic-induced settlements of clay subgrade are usually investigated based on one-way cyclic triaxial tests. Most one-way triaxial cyclic tests on clays have been carried out on normally-consolidated samples, with a constant confining pressure and under undrained conditions. However, it has been found that the varying stress field induced by traffic loading consists of not only cyclic axial stresses, but also cyclic horizontal stresses and shear stresses. Sometimes part of the subgrade soil is overconsolidated, rather than normally-consolidated, and the drainage of pore water is usually allowed under long-term traffic loading. Recognizing this, a series of one-way cyclic triaxial tests was performed on 30 specimens under partially-drained conditions, and the emphases were placed on the coupling effects of the overconsolidation ratio, the cyclic stress ratio, and the cyclic confining pressure on the deformation characteristics of the saturated clay. The test results show that increasing the amplitudes of cyclic confining pressure will cause a remarkable acceleration in the accumulation of both the permanent volumetric strain and the axial strain, whether the sample is overconsolidated or normally-consolidated. A linear relationship is found between the permanent axial strains from tests with variable confining pressure and their counterparts obtained from tests with constant confining pressure, regardless of the OCR and CSR values. A quantitative relationship, which considers the effects of the OCR values, is also established between the increments in cyclic confining pressure amplitudes and the increments in permanent axial strain.

Monotonic Direct Simple Shear Tests on Sand under Multidirectional Loading

AbstractStress–strain responses of Leighton Buzzard sand are investigated under bidirectional shear. The tests are conducted by using the variable direction dynamic cyclic simple shear (VDDCSS). Soil samples are anisotropically consolidated under a vertical normal stress and horizontal shear stress and then sheared in undrained conditions by applying a horizontal shear stress acting along a different direction from the consolidation shear stress. The influence of the orientation and magnitude of the consolidation shear stress is investigated in this study. There have been only a few previous studies on soil responses under bidirectional shear, of which most studies do not consider the impact of the magnitude of the consolidation shear stress. They are compared with current studies, indicating both similarities and differences. Generally, all test results indicate that a smaller angle between the first and second horizontal shear stress leads to more brittle responses with higher peak strengths, and a larg...

Dynamics of laterally confined marine ice sheets

We present an experimental and theoretical study of the dynamics of laterally confined marine ice sheets in the natural limit in which the long, narrow channel into which they flow is wider than the depth of the ice. A marine ice sheet comprises a grounded ice sheet in contact with bedrock that floats away from the bedrock at a ‘grounding line’ to form a floating ice shelf. We model the grounded ice sheet as a viscous gravity current resisted dominantly by vertical shear stresses owing to the no-slip boundary condition applied at the bedrock. We model the ice shelf as a floating viscous current resisted dominantly by horizontal shear stresses owing to no-slip boundary conditions applied at the sidewalls of the channel. The two shear-dominated regions are coupled by jump conditions relating force and fluid flux across a short transition region downstream of the grounding line. We find that the influence of the stresses within the transition region becomes negligible at long times and we model the transition region as a singular interface across which the ice thickness and mass flux can be discontinuous. The confined shelf buttresses the sheet, causing the grounding line to advance more than it would otherwise. In the case that the sheet flows on a base of uniform slope, we find asymptotically that the grounding line advances indefinitely as $t^{1/3}$, where $t$ is time. This contrasts with the two-dimensional counterpart, for which the shelf provides no buttressing and the grounding line reaches a steady state (Robison, J. Fluid Mech., vol. 648, 2010, pp. 363–380).

Cyclic behavior of various sands and structural materials interfaces

This paper presents the results of an intensive experimental investigation on cyclic behavior of various sands and structural materials interface. Comprehensive measurements of the horizontal displacement and shear stresses developed during testing were performed using an automated constant normal load (CNL) cyclic direct shear test apparatus. Two different particle sizes (0.5 mm-0.25 mm and, 2.0 mm-1.0 mm) of sands having distinct shapes (rounded and angular) were tested in a cyclic direct shear testing apparatus at two vertical stress levels (σ = 50 kPa, and 100 kPa) and two rates of displacement (RD = 2.0 mm/min, and 0.025 mm/min) against various structural materials (i.e., steel, concrete, and wood). The cyclic direct shear tests performed during this investigation indicate that (i) the shear stresses developed during shearing highly depend on both the shape and size of sand grains; (ii) characteristics of the structural materials are closely related to interface response; and (iii) the rate of displacement is slightly effective on the results.

Earth’s rotation variability triggers explosive eruptions in subduction zones

The uneven Earth’s spinning has been reported to affect geological processes, i.e. tectonism, seismicity and volcanism, on a planetary scale. Here, we show that changes of the length of day (LOD) influence eruptive activity at subduction margins. Statistical analysis indicates that eruptions with volcanic explosivity index (VEI) ≥3 alternate along oppositely directed subduction zones as a function of whether the LOD increases or decreases. In particular, eruptions in volcanic arcs along contractional subduction zones, which are mostly E- or NE-directed, occur when LOD increases, whereas they are more frequent when LOD decreases along the opposite W- or SW-directed subduction zones that are rather characterized by upper plate extension and back-arc spreading. We find that the LOD variability determines a modulation of the horizontal shear stresses acting on the crust up to 0.4 MPa. An increase of the horizontal maximum stress in compressive regimes during LOD increment may favour the rupture of the magma feeder system wall rocks. Similarly, a decrease of the minimum horizontal stress in extensional settings during LOD lowering generates a larger differential stress, which may enhance failure of the magma-confining rocks. This asymmetric behaviour of magmatism sheds new light on the role of astronomical forces in the dynamics of the solid Earth.

The effect of preloading on the liquefaction cyclic strength of mixtures of sand and silt

The paper studies the effect of preloading on the liquefaction cyclic strength of silty sands in the free field condition. This effect first is investigated by cyclic shear tests where horizontal shear stress oscillated about a zero mean value. Samples with varying fines content and at varying pre-stress ratios, densities and vertical stresses are tested. Test results show a marked increase of the liquefaction cyclic strength with the pre-stress ratio. The effect is more pronounced for tests with less liquefaction cyclic strength without pre-stress. Using critical state soil mechanics concepts, factors simulating the effect of preloading on the liquefaction cyclic strength are identified and based on the results of the laboratory program an empirical expression is proposed predicting the increase in the liquefaction cyclic strength induced by pre-stress. This expression is validated by numerical simulation of the relevant laboratory tests using an elastoplastic multi-mechanism model. In addition, based on the derived expression, a methodology is proposed predicting the increase in liquefaction cyclic strength as a result of preloading in the field in the case of the free field condition. This methodology is validated by the comparison with field measurements on liquefaction-susceptible soils before and after the field application of preloading. Last but not least, the increase in liquefaction cyclic strength which the proposed methodology predicts for typical soil profiles and embankment preloads is predicted and discussed.

Mechanical Effect Study of the Vehicle Braking on the Asphalt Pavement

This paper established a three-dimensional model of asphalt pavement by finite element analysis method, studied the effects of vehicle braking on the asphalt pavement, and analyzed the mechanical law of asphalt pavement through comparing the stress of pavement asphalt when the vehicle is in uniform motion or braking condition. The results show that the vertical stress, vertical displacement and horizontal shear stress of the asphalt pavement increase significantly while the vehicle is under the braking condition. In every asphalt pavement structure layer, the maximum horizontal shear stress under vehicle braking condition are all about four times to that of under vehicle uniform motion, so it’s necessary to significantly improve the shear strength of the asphalt pavement in these sections which often bear automobile braking force.

In situ surface shear strength as affected by soil characteristics and land use in calcareous soils of central Iran

Soil surface shear strength is an important input parameter in the process-based soil erosion models, but its direct measurement at the watershed scale is difficult, time-consuming and costly. This study was conducted to predict in situ shear strength of the soil surface using multiple-linear regression (MLR). The land use impact on the surface shear strength was examined as well. A direct shear box was constructed to measure in situ shear strength (cohesion, c and angle of internal friction, φ) of the soil surface in the Semirom region located in Isfahan province, central Iran. The shear device consisted of a circular shear box (with 10cm internal diameter and height of 1cm), an S-shaped load cell for measuring horizontal (shear) stress and an electric motor for applying the shear stress. The normal stress acting on the failure surface was adjusted by adding weights on the shear box. Soil surface shear strength was determined using the shear box at 100 locations under three land use systems of grassland, irrigated farming and dryland farming. Soil particle size distribution (clay, silt, sand and fine clay), organic matter content (OM), carbonate content, bulk density and gravel content were determined as predictors of the surface shear strength. Normalized difference vegetation index (NDVI) was also calculated using satellite images. The MLR was employed to predict the shear strength (i.e. c and φ) using two groups of input variables: i) easily-available soil properties (pedotransfer functions, PTFs) and ii) easily-available soil properties and NDVI (soil spatial prediction functions, SSPFs). A strong negative correlation (r=−0.72, p<0.001) was found between c and φ in the studied area. Positive correlation (r=0.41, p<0.001) was obtained between c and fine clay content. The c was negatively correlated (r=−0.31, p<0.01; r=−0.37, p<0.001) with sand and gravel contents, respectively. A significant positive correlation (r=0.47, p<0.001) was observed between φ and gravel content, indicating the roughness effect of coarse particles on frictional shear strength. The results also showed that NDVI is an important factor indirectly explaining the variability of both c and φ in the studied soils. The land use effect on the soil properties was investigated using the LSD0.05 test. The means of φ somehow follow the variation of gravel content among the land uses; the highest means of clay and fine clay contents and c, and the lowest means of sand and gravel contents and φ were observed in dryland farming. The c has the same trend as did clay content; irrigated farming with the highest mean of sand content and lowest mean of clay content had the lowest mean of c. The c means were significantly different between irrigated farming and dryland farming. Prediction models of in situ shear strength derived using both soil properties and NDVI as predictors (SSPFs) were more accurate than those derived using only soil properties (PTFs).

Analytical Modeling of the Interface between Lightly Roughened Hollowcore Slabs and Cast-In-Place Concrete Topping

Hollowcore slabs are commonly used in different types of structures. They usually include a 50-mm concrete topping. Structural engineers can use this topping to increase the slab load-carrying capacity. North American design standards relate the horizontal shear strength at the interface between hollowcore slabs and the concrete topping to the slab surface roughness. This paper presents the results of four push-off tests on hollowcore slabs supplied by two manufacturers and roughened using a conventional steel broom. The tested slabs sustained higher horizontal shear stresses than those specified by the design standards. Utilizing the data from the push-off tests, an analytical model was applied to evaluate the shear and peel stiffnesses, ks and kp, of the interface between hollowcore slabs and concrete topping. Structural engineers can utilize ks and kp values to model the composite action between hollowcore slabs from the two manufacturers and concrete topping. The analytical model was also used to evaluate the actual distribution of shear and peel stresses.

In‐Situ Stress Measurements and Slip Stability of Major Faults in Beijing Region, China

AbstractIn order to estimate the upper crustal stress state and slip stability of major faults after the Wenchuan Ms 8.0 earthquake, five boreholes, i.e., Pinggu, Shisanling, Xifengsi, Miyun, and Lisiguang Memorial Hall borehole ranging from 600 to 1000 m were drilled in Beijing region. Hydraulic fracturing method was used to conduct in‐situ stress measurements in these five boreholes, and stress monitoring equipment was installed at appropriate depth and monitoring stations were constructed. Those data derived from the in‐situ stress measurements reveal that the gradient coefficients of the maximum horizontal stresses and minimum horizontal stresses versus depth are 0.0328 and 0.0221, respectively; and the magnitudes of lateral pressure coefficient such as Kav, KHv and the ratios (KHh) of the maximum horizontal stress to minimum horizontal stress are consistent with previous studies. However, the ratios (μm) of the maximum horizontal shear stress to the average horizontal stress are relatively low. It is noted that the dominant direction of the maximum horizontal stress in Beijing region is ∼EW which is the same with the tectonic stress field of North China. However, sub‐regional stress field induced by faults which shows deviation from the orientation of North China, has been also revealed. In addition, the stress regimes inferred from in‐situ stress data imply that the maximum horizontal stress (σH) is the maximum principal stress (σ1), while the intermediate (σ2) and the minimum principal stress (σ3) show some variations. It is suggested that these variations may be caused mainly by the regional tectonic evolution and the activity of faults near the boreholes. Based on these characteristic parameters, we can point out that the maximum horizontal stress in the upper crust of Beijing region can be defined as dominant stress, while the horizontal shearing stress is relatively weak. Finally, slip stability of major faults in Beijing region is estimated according to Column friction criterion and Byerlee's law, together with the frictional coefficients being assumed to be 0.2, 0.4, 0.6 and 1.0. The results reveal that when the frictional coefficient ranges from 0.6 to 1.0, the recent crustal stress state of Beijing region does not yet reach the expected limit of fault slip. The stress values of the Xifengsi borehole will reach the expected limit when the frictional coefficient is weakened to 0.4, revealing that the Babaoshan fault stands chance of slipping; the Xiadian‐Mafang fault and the Huangzhuang‐Gaoliying fault will approach to the expected limit of slip and will stand chance of slipping under this hypothesis, but only with very low possibility. However, it should be pointed out that if the frictional coefficient is weakened to as low as 0.2, the major faults in Beijing region will be unstable and slip may occur under the present‐day crustal stress state. Conclusions in this paper would be of great significance for studies on tectonic stress field and seismogeology in Beijing region, even North China.

판형 중공재를 사용한 중공슬래브의 전단실험

판형태 중공재를 사용한 중공슬래브는 중공에 의해 자중을 절감시킬 수 있어 제작 및 운송비용을 줄일 수 있다. 하지만 큰 중공률 때문에 전단저항성능이 감소될 수 있고, 중공재를 기준으로 슬래브의 상 하부 플랜지 콘크리트의 일체성에 취약할 수 있다. 본 연구에서는 판형 중공재를 사용하는 중공슬래브의 전단파괴모드와 전단강도에 대하여 연구하였다. 12개의 전단 실험체에 2점 가력을 수행하였다. 실험 변수는 중공률, 중공재 수직 위치, 수직철근(다월철근)의 설치여부 이다. 실험결과 슬래브 하부에 휨균열이 발생한 직후, 웨브 콘크리트의 상 하에서 수평균열이 발생하여 강성이 크게 저하되었다. 중공률 32.5% 이상의 슬래브 실험체는 웨브 콘크리트 수평균열로 인하여 최종파괴 되었지만, 중공률 28.9% 미만의 실험체는 일반 보에서 흔히 관찰되는 웨브 콘크리트의 대각전단파괴가 발생하였다. 중공슬래브 웨브 콘크리트의 최대 수평전단응력은 중공률이 32.5%에서 41.4%로 증가함에 따라 0.26 <TEX>$\sqrt{f_{ck}}$</TEX>에서 0.51 <TEX>$\sqrt{f_{ck}}$</TEX>로 증가하였다. 또한 수평균열과 직각으로 배근된 수직철근은 슬래브의 전단강도를 강화시켰다. Due to less weight (i.e. greater void ratio), voided concrete slabs with board-type voiding materials take advantages of easier fabrication and less transportation cost. However the shear resistance can be decreased due to the greater void ratio(or the poor integrity between concrete plates at the top and bottom of the voiding material). In the present study, the shear resistance and failure mode of the voided slabs with board-type voiding material were investigated. Two-point loading shear tests were performed for 12 slab specimens. Test parameters were the void ratio, the location of the voids, and the presence of reinforcing vertical bar (or dowel bar). Test results showed that premature horizontal cracking developed at the top and bottom of the web concrete, shortly after flexural cracking at the bottom of the slabs. The slab specimens with void ratios greater than 32.5% were ultimately showed the horizontal shear failure of the web concrete, while the specimens with the void ratios less than 28.9% showed the conventional diagonal shear failure. The maximum horizontal shear stresses of concrete at failure, increased 0.26 <TEX>$\sqrt{f_{ck}}$</TEX> to 0.51 <TEX>$\sqrt{f_{ck}}$</TEX> as the void ratio increased from 32.5 % to 41.4 %. The vertical bars of the web which were perpendicular to the horizontal cracks of the web concrete, enhanced the shear strength of the slabs.

Predicting shear strength of RC interior beam–column joints by modified rotating-angle softened-truss model

A theoretical model is presented for analysing the shear behaviour and predicting the shear strength of reinforced concrete (RC) interior beam–column joints. The model presented is referred to as the modified rotating-angle softened-truss model (MRA-STM), which is modified from the rotating-angle softened-truss model and the modified compression field theory. In the proposed methodology, the RC interior joint is treated as an RC shear panel that is subjected to vertical and horizontal shear stresses transferred from adjacent columns and beams. Employing the deep beam analogy, the characteristic strut and truss actions typical in beam–column joints are represented by the effective transverse compression stresses and the softened concrete truss in the model. Sixteen RC interior beam–column joints were subsequently analysed with the proposed model. Shear strengths of the RC interior beam–column joints predicted by the proposed model show very good agreement with the experimental results.

Effect of Type and Position of Shear Reinforcement of High-Strength Reinforced Concrete Deep Beams -ENG

This paper reports experimental data on the behavior and strength of high-strength concrete deep beams reinforced with shear reinforcement. Tests were conducted on eight reinforced concrete deep beams with stirrups in different type and positions using high-strength concrete (compressive strength of about 85.0 MPa). The beams measured 1400 mm long, 100 mm wide and 300 mm deep, and were tested under two point loads. The test variables were type and position of web reinforcements [Shear stress of vertical stirrups (vfy), Shear stress of horizontal stirrups (hfy) and Shear stress of inclined stirrups (αfy)] within shear span, within middle span(between two point loads) and along the beam. Conventional steel bars were used as longitudinal reinforcement in this investigation. The test results indicated that beams with vertical and inclined shear reinforcement within the shear span (B4) resisting the ultimate load of about 417.90kN. While beams with horizontal shear reinforcement (B3), shear reinforcement between two point loads (B7), and the beam without shear reinforcement (B8) resisting, 255.77, 260.18 and 250.55kN respectively. All the beams failed in shear and the optimum position of stirrups is the shear span for high strength concrete deep beams and with combination of vertical and inclined stirrups. Keywords: Concrete; Deep beams; High strength; Position; Shear; Stirrups.

Transfer Function of Interfacial Stress Sensor for Artificial Skin Applications

To help improve the comfort of an amputee, it is important to develop artificial skin to understand the load distribution between the residual limb and the prosthetic socket for a prosthetic socket system. This paper presents an interfacial stress sensor which is capable of simultaneously measuring normal compressive stress and horizontal shear stress and is expected to create an artificial skin to understand such load distribution. A mathematical model based on regression analysis is built and an experiment is conducted to obtain the transfer function of the sensor. A significance test shows that the transfer function has a statistical significance at a significance level of 0.05 and the regression model fits the experimental data with a sample determination coefficient . The relative error is also analyzed in the end. The results show that the sensor is capable of measuring a range 0-320 kPa normal compressive stress with a relative error of 5% and a range of 0-70 kPa horizontal shear stress with a relative error of 14%.

Normal and shear stresses acting on arbitrarily oriented faults, earthquake energy, crustal GPE change, and the coefficient of friction

As usual, earthquake energy is defined as the total energy released from an earthquake, which is partitioned into radiated energy, friction energy, and rupture energy regardless of crustal gravitational potential energy (GPE) change. We analyze the energy and stress parameters in earthquake energy budget. For arbitrarily oriented faults, we deduce the formulas for calculating the normal and shear stresses acting on the fault under principal stresses. We show that shear stress is composed of horizontal and vertical shear stresses. Then, we provide the expressions for computing crustal GPE change and the coefficient of friction. The GPE change should be considered, except strike-slip faulting, when investigating earthquakes. Also, for various faulting types, we show that the ratio of differential stresses is related to the fault orientation and the relative magnitudes of stresses. Finally, “12 May, 2008, Wenchuan, Sichuan, China, MW 7.9 Earthquake” is cited to analyze and calculate various energy/stress parameters and the coefficient of friction. Our result of GPE change coincides with the post-event field observations.

Performance of an Interior Beam-Column Joint with and without a Slab under Cyclic Load

The beam-column joint is a crucial zone in a reinforced concrete moment resisting frame. It is subjected to large forces during severe ground shaking, and its behaviour has a significant influence on the response of the structure. In the present study, two half-scaled cast-in-situ beam-column subassemblies (i) without slab and (ii) with slab, with reinforcement detailing as per ACI 318-63 (1963) provisions are constructed. The beam-column joints are comprehensively instrumented and tested under static displacement controlled cyclic loading. This paper explains the contribution of the floor slab, especially in “Tension flange” on the overall cyclic behaviour of the subassembly, and the experimental results of horizontal joint shear stress are discussed, and compared with the ACI 352R-02 provisions.

Three-Dimensional Finite Element Analysis of Dynamic Response of the Stress in Pavement Structure under Overload

In recent years, the phenomenon of vehicle overload in highway transportation is more and more serious. The three-dimensional dynamic FEM was adopted and a three-dimensional simulative model for asphalt pavement with subgrade based on cross-anisotropy under moving load was established by the large-scale finite element analysis software ABAQUS. The response of the stress in the pavement structure was got by using ABAQUS/Standard code. During deceleration, The simulation analysis results under the rated load were compared with those under the different overload ratio. The results show that, under moving load, the surface course of pavement is mainly in three dimension compressive stress state. The horizontal load caused by deceleration has a remarkable effect on the longitudinal stress and the horizontal shearing stress. The stress of the pavement structure under overload is much greater than that caused by the rated load. And the greater the overload ratio, the greater the deviation between them.

The Mechanical Response Analysis of the Airport Asphalt Pavement Considering Horizontal Load

In order to research the mechanical response of asphalt pavement under horizontal load which produced by the large aircraft braking process, large-scale finite element software is used in this paper. The model of main landing gear load is established to analyze the change of principal mechanics indexes of airfield pavement when the aircraft has different landing distance. The results show that: the horizontal load has a significant influence on the normal stress of landing direction, but the influence area is concentrated in the rear of the wheel. The horizontal load has more effect on horizontal shear stress and longitudinal shear stress, while has less effect on tensile stress of surface layer bottom, tensile tress of base course bottom and transverse shear stress. The tensile stress of surface layer will increase significantly when the braking distance is less than 2000m. Meanwhile, thickening surface layer could decrease the tensile stress and increase the fatigue lifetime apparently.

Unsteady Incompressible Couette Flow Problem for the Eyring-Powell Model with Porous Walls

This work is concerned with the influence of uniform suction or injection on unsteady incompressible Couette flow for the Eyring-Powell model. The resulting unsteady problem for horizontal velocity field is solved by means of homotopy analysis method (HAM). The characteristics of the horizontal velocity field and wall shear stress are analyzed and discussed. Pade approximants and Taylor polynomials are also found for velocity profile and are used to make the maximum error as small as possible. The graphs of the error for the Pade approximation and Taylor approximation are drawn and discussed. Convergence of the series solution is also discussed with the help of h-curve and interval of convergence is also found.