Shear Strength Behavior Research Articles

Torsional shear strength behavior of advanced glass-ceramic sealants for SOFC/SOEC applications

Since reliable long term operation of SOFC and SOEC devices depends critically on the mechanical behavior of the sealant material, the current work focuses on the characterization of the shear strength by a torsion test of two different glass-ceramic sealants that are used to join Crofer22APU substrates in an application relevant configuration. The two glass-ceramic sealants differ in terms of characteristic temperatures and crystalline phases with possible impications on the joining behavior. Statistically identical shear stress values were measured at room temperature for joined hourglasses of different size with both sealants, thus confirming a size independence of the measured strength values. Experimental post-test examination results confirm that the interfaces play a strong role regarding the measured shear strength and provide important insights with respect to integration of metallic and glass-ceramic components in SOFC/SOEC stacks.

A Comparative Study on Shear Strength and Deformation Behaviour of Clayey and Sandy Soils Reinforced with Glass Fibre

In this investigation, the shear strength and specimen deformation behaviour of glass fibre-reinforced clayey and sandy soils have been compared based on the results of consolidated undrained and consolidated drained triaxial tests, respectively under varying moulded states. The clayey soil specimens were moulded with varying dry unit weight, whereas sandy soil specimens were moulded at relative densities ranging from 35 to 85%. For any moulded state, no peak is noted in the stress–strain curves of reinforced clayey soil up to 20% axial strain. In case of the reinforced sandy soil, clear peak is observed well before 20% axial strain with post-peak stress reduction at all relative densities. Reinforced clayey soil shows bulging at all dry unit weights. For the reinforced sandy soil, bulging failure is noted at 35% relative density, whereas shear failure occurs at relative densities of 65% and 85%. At all dry unit weights, under undrained condition, the reinforced clayey soil exhibits only positive pore water pressure indicating contractive behaviour at all axial strains. Under drained condition, the reinforced sandy soil of 35% relative density shows contractive behaviour, while the specimens of 65% and 85% relative densities indicate contractive response at smaller axial strain followed by dilative behaviour at higher strain. The increase of shear strength is up to 0.75% and 3% fibre content in the clayey and sandy soils, respectively irrespective of moulded states. At respective optimum fibre reinforcements, the benefit of glass fibre reinforcement is greater for the sandy soil. The possible environmental impact and field application of glass fibre-reinforced soil have also been discussed.

Friction stir spot welding of AA6061-T6 and Cu with preheating: Strength and failure behavior at different test temperatures

In the current study, the influence of test temperatures was investigated on lap shear strength and fracture behavior of dissimilar and similar friction stir spot-welded (FSSW) joints between Cu and AA6061-T6 sheets prepared without and with employing additional heating. Formation and distribution of intermetallic compounds (IMCs) in Cu-AA6061 FSSW joints was further appraised. An increase in maximum lap shear force was observed in Cu-AA6061 and Cu-Cu joints when preheating was employed. Lap shear force decreased with increase in test temperature for Cu-AA6061 joints prepared without preheating; however, for joints prepared employing preheating, the lap strength increased from 25 to 50 °C following a slight drop at 100 °C test temperature. For Cu-Cu joints, lap shear force also increased with test temperature for the range studied in the present work. X-ray diffraction, and energy dispersive spectroscopy analysis illustrates the formation of IMCs in the form of Al2Cu and Al4Cu9 in Cu-AA6061 and oxides in Cu-Cu joints. The interface failure from IMC rich regions in dissimilar joints was observed whereas similar joints failed under plug failure. Intermittently, thick IMC layer was observed in dissimilar Cu-AA6061 joint prepared with preheating. Presence of tearing/rupture from oxide dominated intermetallic region observed in Cu-AA6061 FSSW joints whereas dimples and micro-voids were noted in Cu-Cu joints.

Shear strength properties of Hong Kong soils for slope stability

With the recent advancement in technology, the method, accuracy and speed of slope stability analysis have been vastly improved. Nevertheless, the reliability and appropriateness of such analysis can be very much in doubt if the soil behaviour, in particular the shear strength behaviour, is not fully understood. The objective of this paper is therefore to evaluate the shear strength behaviour of various soil types in Hong Kong. This comprises the collection, processing and analysis of the laboratory and field works carried out in the past few decades, in particular the triaxial compression testing in the laboratory and standard penetration test (SPT) in the field. For correlating SPT with soil shear strength, a fairly large number of carefully controlled site investigation works with SPT are carried out both above and below any Mazier sampling. Laboratory triaxial tests are then carried out in these Mazier samples. Finally, it is hoped that a basically quantitative relationship between soil shear strength and SPT can be obtained as this would enable a soil shear strength profile to be established once the corresponding SPT profile has been determined on site by carrying out SPT in adequate number of drill holes.

Settling, consolidation and shear strength behaviour of coal tailings slurry

The volume change and shear strength behaviour of tailings slurry with the changes in gravimetric moisture content is important to effectively utilise the storage volume and analysis of dam failure potential. Consolidation testing of tailings from a slurry-like to soil-like state is a critical task, and conventional consolidation apparatus does not have the capability of doing such testing, as the tailings slurries contain high water content. Settling tests conducted on slurries having a 25% solids concentration showed very low efficiency; final sediment was still slurry-like. An intrinsic point was identified based on pore water pressure dissipation during consolidation tests in a slurry consolidometer that can define two states of the tailings i.e. slurry-like and soil-like. In the slurry-like state, the volume change was greater for Slurry 2 than Slurry 1, while the inverse was observed in the soil-like state. The evolution of peak vane shear strength with the changes in moisture content was almost similar for both samples and obeyed the power function. Regression models have been developed and validated to predict the shear strength of materials at any gravimetric moisture content or void ratio.

Behavior of Self Compacting Reinforced Concrete One Way Bubble Deck Slab

Reinforced concrete slab with plastic voids (Bubbled Deck system) is a new type of slabs which has two-dimensional arrangement of voids within the slab that is developed to decrease the slab self-weight while maintaining approximately the same load carrying capacity as compared with the solid slabs. Plastic voided slabs have the ability to reduce concrete amount by about 30 percent and this reduction is so important in terms of cost saving and enhancement the structural performance. In this research paper investigation is carried out to study the shear strength behavior of one-way bubble deck slab using self-compacting reinforced concrete. The experimental program consists of testing thirteen one-way slabs with dimensions of (1700 length, 700 width and 150 thick) mm. One of the tested slabs is a solid slab (without balls) is used as a reference, the remaining twelve bubbled slabs with ball diameter (73, 60) mm are divided into five groups according to the parameters of the experimental work, the parameters of the experimental work include: type of slab (bubble and solid slabs), ball diameter (73, 60) mm, shear reinforcement and spacing between balls. The experimental results showed that the bubbled slabs without shear reinforcement have a decrease in the ultimate load as compared to solid slab by about 3.7% to 14.3% and an increase in the deflection at ultimate load by about 10% to 22%, at the same time the first crack load decreases by about 15.3% to 42.4% as compared to solid slab due to decreases of moment of inertia of bubble slab compared to solid slab. Also, the results showed that the bubbled slabs withe shear reinforcement (multi-leg) have an increase in the ultimate load as compared to solid slab by about 35.4% to 57.3% and an increase in the deflection at ultimate load by about 1% to 15%, at the same time the first crack load decreases by about 2.8% to 27.4% as compared to solid slab.

Shear connection of prefabricated slabs with LWC - Part1: Experimental and analytical studies

This paper studies the shear strength and load-slip behaviours of a recently developed novel steel-concrete composite flooring system (PUSS) with two different types of shear connectors while also using lightweight concrete. PUSS consists of a T-ribbed lightweight concrete floor and C-channel steel edge beams. The proposed shear connection system is using either web-welded shear studs only, or combined with horizontally lying steel dowels. This unique system further minimises its structural depth and results in ultra-shallow floors.Eight full-scale push-out tests were conducted to investigate the connection under the direct shear force with three different concrete types (normal concrete, lightweight and ultra-lightweight concretes) and two different shear connection systems (web-welded shear studs only and horizontally lying steel dowels together with web-welded shear studs). Three types of failure were recorded from the push-out tests; shear failure with bending near the roots of the connectors, shear failure of the weld toe of shear studs, and concrete cracking. Among the conclusions, it was validated that the compressive strength of the concrete significantly influences the ultimate shear strength capacity loads while it is influencing the failure mode of the connection. The failure mechanisms of the shear connectors were extensively studied, which led to the development of a calculation method for the shear strength and load–slip behaviours of the new connectors embedded in lightweight concrete. The analytical results are compared with those predicted by modern codes of practices and available methods from the literature. It is concluded that the proposed formulae offer a reliable prediction.

Time-Dependent Shear Strength Behavior of Superf?ne Cement-Stabilized Clayey Soil

Time-Dependent Shear Strength Behavior of Superf?ne Cement-Stabilized Clayey Soil

Hydromechanical properties of 3D printed fractures with controlled surface roughness: Insights into shear-permeability coupling processes

We explore the potentials of three-dimensional (3D) printing to explore hydromechanical processes in laboratory-scale fractures. 3D printing enables replication of designer fractures with quantified and repeatable roughness to examine the interdependencies between mechanical and hydraulic response including, for example, the Barton-Bandis model. The present study successfully probes subtle variations of shear strength and dilation behavior in 3D printed fractures controlled by surface roughness. For constant materials and basic frictional characteristics, shear strength increases with increasing the standard deviation of the surface height with dilation rate principally controlled by the average amplitude of the long period wavelength of the fracture surface and insensitive the secondary (minor amplitude) roughness. Importantly, these sensitivities are manifest in the permeability response. With increasing shear displacement, the fracture permeability first decreases and then increases with oscillations resulting from step changes in fracture-fracture contact architectures. As these distinctive behaviors are consistent with those of real rock fractures, we conclude that 3D printed fractures provide a useful analog to real rock fractures when constraining slip-permeability coupling during shear slip.

Shear Behavior and Anisotropy Characteristics of the Fracture Morphology of Sandstone with Different Water Contents

Hydromechanical coupling in rock masses is an important issue for many rock mechanics and hydrogeology applications. The change of a water-bearing state will induce the fracture of the intact rocks and further accelerate the shear slip instability of the sheared surface. To investigate the weakening effect of water content on the mechanical properties of a rock mass, laboratory direct shear tests combined with three-dimensional analysis of sheared surfaces were carried out on sandstone samples with different water contents. The variogram parameters, sill and range, were applied to quantify the morphology of shear fracture surfaces, to reflect the shear failure process of the intact rock, and to provide a basis for resliding instability of jointed rock. It was determined that the sill represents the height of the fluctuation body in the fracture surface and the range represents the single fluctuation body and may reflect the frequency of fluctuations. The test results revealed that the increase in water content had a clear weakening effect on the shear strength and deformation behavior of rock, especially under saturated conditions. Moreover, the distribution of water in the samples directly affected the crack initiation and propagation and characteristics of the fracture morphology.

Effect of steel fiber on the shear transfer strength across a crack in reactive powder concrete

In structural concrete members that have geometrical discontinuities, the type of failure is called direct shear failure when there is no; the same member may change its response when the load arrangement is changed. This kind of failure is related to the cracks along the plane where the loaded member slides along the stationary support system and cracks are perpendicular to the axis of the member. Numerical analysis on push-off specimens were conducted in this study to investigate the shear strength in reactive powder concrete, which has cementitious compositions. The validation of the material and geometrical model to check the efficiency of the constitutive model to simulate the behavior of shear strength of RPC was achieved through comparison with the experimental result of previous work. The effects of volume fraction, aspect ratio, shape of steel fibers on the shear strength were considered to be the variables of the study. The data analyzed showed that the increase in volume fraction of steel fiber from 0% to 0.5% resulted in an increase in the shear strength of RPC by 40.3%, while, an increase in the volume fraction of steel fiber from 0% to 1.5% increased the shear strength of RPC by 140.3%. Using hook ended steel fiber increased the shear strength of RPC by 62.5%. Furthermore, the shear strength of RPC increased by 49.8% when the aspect ratio increased from 75 to 100. The stiffness and ductility of RPC members increased when the volume fraction, aspect ratio increased and provided shape of steel fiber.

Critical state behaviour of an unsaturated high-plasticity clay

This paper describes a series of tests carried out to examine triaxial compression and shearing of a high-plasticity compacted clay. Reconstituted and compacted samples which were saturated are used as a basis for interpreting the unsaturated test results within a critical state soil mechanics (CSSM) framework. The shear strength behaviour of unsaturated soils have previously been found to be reasonably well captured in a CSSM framework, whereas the volume change behaviour has been more difficult to rationalise. Based on test results presented using the Bishop effective stress, the volume change behaviour during shear suggests that a unique critical state line is approached, independent of the applied suction. The normalised shearing behaviour of the compacted unsaturated soil is interpreted to be analogous to that of saturated-structured soils.

A Laboratory Study on the Influence of Anisotropy on the Soil Behavior

Anisotropy refers to any directional-dependence on material property. In recent years, the anisotropy of intermediate-strain behavior and shear strength, small-strain stiffness anisotropy has attracted attention. The main aim of this paper is to clarify the influence of inherent anisotropy on the compressibility characteristics and shear strength behavior of fine-grained soils. A special manufactured device has been made in order to prepare and collect the samples in different directions. Then, a series of conventional tests have been carried out on the soil samples consists of unconfined compressive and Oedometer tests. Low plasticity clay has been used with three liquidity indices (0.22, 0.32, and 0.44) in order to achieve the goal of the study. The results have showed that the anisotropy had an impact on the undrained shear strength of cohesive soil and the soil strength can be considered as strength anisotropy. The higher anisotropy angle causes the more reduction in the shear strength. The settlement is affected by anisotropy, increasing of the anisotropy leads to the increase of the settlement, the compression and the swelling indices. The coefficient of consolidation in the vertical direction is lower than the coefficient in inclined direction and the ratio of (ch/cv) tends to increase with anisotropy angle the highest ratio is 1.4.

Physicochemical effect on shear strength characteristics of clayey soils based on ring-shear experiment

Pore fluid chemistry can significantly influence the shear strength characteristics of a clayey soil. To explore the underlying mechanisms, a series of ring shear experiments are performed on two natural clays, which represent two typical types of clayey minerals, i.e., expansive montmorillonitic clay and low-plasticity kaolinitic clay. The effects of pore solution concentrations on the shear strength of the two clays are experimentally characterized. It is shown that the shear strength of the expansive clay can be significantly influenced by the pore solution chemistry, whereas that of the low-plasticity clay proves to be relatively insensitive to it. To capture the main features of the shear strength behavior of clayey soils, the concept of intergranular stress, which is an extension of the Terzaghi’s effective stress to incorporate physicochemical effect, is introduced to interpret the experimental data. It is found that the evolution of residual shear strength can be very well characterized by using the intergranular stress, showing that the proposed intergranular stress formulation can be used alternatively to describe the stress state of clayey soils saturated with various pore solutions.

Double Shear Load Carrying Capacity of Kempas and GFRP Dowelled Connections

Glass fibre reinforcement polymers (GFRP) application for reinforcement of wood, concrete and steel member is relatively becoming more variety in construction applications. Although it is possible to build large monolithic structures with composite materials, there are still several reasons for the structure to fail. One of the main reasons that contribute to this failure is the connection performance due to its function in carrying load across the structure. Thus having the right fundamental data for connection design purposes according to the specific and technological upgraded materials is very important. One of the basic methodologies in gaining the design data is through experimental double shear test which can be verified by European Yield Model (EYM) theory. Therefore, the objective of this research is to determine the load carrying capacity of double shear strength behaviour connections made of Kempas timber species as the main member and dowelled by the GFRP or the Kempas rod. The specimens were tested under the shear load with 2mm/min rate and tested until failure. From the experiment, it was found that the average ultimate shear strength of member dowelled with GFRP rod is 21.36% higher compared to one doweled with Kempas rod. According to mode of failure between two types of bolt, GFRP dowelled performs well (Mode I& IV) rather than Kempas dowelled (Mode IV).

Creep Behavior of Red-Clay Under Triaxial Compression Condition

To investigate the shear strength and creep behavior of red-clay, laboratory experiments were conducted and the experimental results were compared with available theoretical creep models. Based on the consolidated-drained (CD) triaxial tests results, internal friction angle and cohesion of the red clay soil were 21.5° and 61.1 kPa, respectively. Three different confining pressures were set up to conduct the creep tests using multi-stage loading. The overall creep curves exhibited stepped stress-strain behavior. The creep behaviors were remarkably different for the soils tested with three different confining stresses. The post-creep failure mode of all the red clay samples exhibited drum shaped parabolic bulging with predefined shear planes. The experimental results were compared with three different types of creep models used in practice. Among the verified results, the Burger’s Model showed better fitting with the experimental data compared to the other models. An experimental result based empirical equation has also been developed, which fits well with the experimental results obtained from the tested red clay samples. The results of this study will be helpful to evaluate the long-term shear strength and deformation of red clays subjected to various structural loadings.

Effect of Particle‐Size Gradation on Coarse Sand‐Geotextile Interface Response in Cyclic and Postcyclic Direct Shear Test

In order to investigate the influence of sand particle‐size gradation on cyclic and postcyclic shear strength behaviour on sand‐geotextile interfaces, a series of monotonic direct shear (MDS), cyclic direct shear (CDS), and postcyclic direct shear (PCDS) tests were performed using a large‐scale direct shear apparatus. The influence of cyclic shear history on the direct shear behaviour of the interface was studied. The results indicated that cyclic shear stress degradation occurred at the sand‐geotextile interface. Shear volumetric contraction induced by the cyclic direct shear increased with the increase in cycle number. The lowest final contraction value was observed in discontinuously graded sand. In the MDS tests, there were great differences in interface shear strength due to the different particle‐size gradations, whereas the differences between shear volumes were negligible. In the PCDS tests, the shear stress‐displacement curves exhibited postpeak stress hardening behaviour for different particle‐size gradations, and differences in shear volumes were detected. The well‐graded sand‐geotextile interface had a higher value of shear stiffness and a higher damping ratio relative to the other interfaces. Postcyclic shear stress degradation was observed for the discontinuously graded sand‐geotextile interface.

Experimental Study on Shear Strength Behaviours of the Composite UHPC Steel Girders in Slender web

Modern structures require light elements with high stiffness to weight ratios. Composite structures with high-performance material are particularly useful for long spans such as in bridges and large buildings. Conventional concrete is brittle, with very low tensile and high compressive strength; ultra-high performance concrete UHPC can be used to improve the ductility and strength of the deck slab, yet though many researchers have examined the behaviour of UHPC individually, this material requires investigation in conjunction with other variables. A composite structure of steel plate girders and concrete deck is thus examined in the present study, with seven plate girders and three composite girders. Flat web plate girders without stiffeners were investigated to estimate ultimate strength in two parameters, web slenderness, and flange slenderness. In addition, three composite girders were tested with web slenderness ratings 167, 250, and 375. The results show the effects of slenderness on shear strength and the failure accrued due to tension field action, while elastic buckling was seen to contribute to shear strength.

Shear strength behaviour of sand-bentonite mixtures with pumice additivite under high temperature

Depending on increase in the number and type of energy geostructures, studies on the change in soil behavior against heat increase becomes more important. The engineering properties such as permeability, volume deformation of surrounding soils around energy structures mustn’t alter in the presence of heat and thermal cycles. Pumice is a material used in many fields especially for thermal insulation. For that reason, pumice can be used for increasing the resistance of soils in the presence of heat. In this study, the shear strength behavior of sand-bentonite mixtures was investigated with pumice additive under high temperature. In the experiments, 10% and 20% pumice were added to 10% and 20% sand-bentonite mixtures and compaction, direct shear tests were conducted. The direct shear tests were performed both room temperature and under 80°C. The results have shown that the pumice additive increased the shear strength of sand-bentonite mixtures under high temperature when compared the test results under room temperature.

Performance of hybrid fibre reinforced geopolymer concrete beams

An experimental investigation was carried out to study the effect steel fibres and hybrid fibres (steel and polypropylene) on the performance of low calcium fly ash based geopolymer concrete beams under shear. The main variable considered are the volume fraction of steel fibres (0.5% and 1%) and volume fraction of hybrid fibres (0.25% steel fibres and 0.25% polypropylene fibres, 0.25% steel fibres and 0.75% polypropylene fibres and 0.5% steel fibres and 0.5% polypropylene fibres). Test results revealed that the split tensile strength, flexural strength and modulus of elasticity of hybrid fibre reinforced concrete are more than that of steel fibre reinforced concrete. For studying the performance of fibre reinforced and hybrid fibre reinforced beams under shear, shear deficient beams of size 1200 mm × 100 mm × 150 mm size were prepared with varying volume fractions of fibres. The beams were tested under two point loading after 28 days of casting. Experimental results indicated that the hybrid fibre reinforced geopolymer concrete beams are having better shear strength and superior behaviour than steel fibre reinforced beams.