Shear Failure Behavior Research Articles

Shear strength and failure behaviour of laser nano-structured and conventionally pre-treated interfaces in intrinsically manufactured CFRP-steel hybrids

Nowadays, the issues of environmental protection as well as energy and resource efficiency become of increasing importance. Especially in the automotive industry, the effort to realize an efficient manufacturing of lightweight structures is immense. Thereby a current trend is the fabrication of hybrid structures by using innovative procedures. As a consequence, the generation of a strong and durable connection between dissimilar materials is the toughest challenge. In this study, the influence of a laser based nano-structuring on the shear strength of hybrid structures out of carbon fibre reinforced plastics (CFRP) and micro-alloyed steel (1.0548) fabricated by a Vacuum Assisted Resin Transfer Molding (VARTM) process is presented. Furthermore, the failure behaviour is analysed. The exact stress distribution in the overlap area is investigated by using a Finite Element (FE) analysis. To this end, the input data for the interface are based on the results of butt bonded hollow cylinder-tests.

THE EFFECTS OF INCLINED SHEAR REINFORCEMENT IN REINFORCED CONCRETE BEAM

This paper presents the findings of an experimental data on the effects of inclined shearreinforcement in reinforced concrete (RC) beam. Two types of shear reinforcement of RC beamwere investigated, conventional stirrups (vertical links) and inclined shear reinforcement (45degrees of inclined shear reinforcement). The RC beam with conventional stirrups wasdesignated as a control specimen. The RC beams with different types of shear reinforcementwere tested for shear under four-point loading system. Comparisons were made between bothtypes of RC beam on load-deflection, load-steel strain, load-concrete strain behaviour and modeof failure. The theoretical and experimental were calculated by using conventional formulation inaccordance to EC 2 in order to verify the experimental results. From the results, it was observedthat the RC beam with 45 degree inclined shear reinforcement improved structural performancein shear by approximately 20% and thus prolong the shear failure behaviour as compared to theRC beam with vertical links.

THE EFFECTS OF INCLINED SHEAR REINFORCEMENT IN REINFORCED CONCRETE BEAM

This paper presents the findings of an experimental data on the effects of inclined shearreinforcement in reinforced concrete (RC) beam. Two types of shear reinforcement of RC beamwere investigated, conventional stirrups (vertical links) and inclined shear reinforcement (45degrees of inclined shear reinforcement). The RC beam with conventional stirrups wasdesignated as a control specimen. The RC beams with different types of shear reinforcementwere tested for shear under four-point loading system. Comparisons were made between bothtypes of RC beam on load-deflection, load-steel strain, load-concrete strain behaviour and modeof failure. The theoretical and experimental were calculated by using conventional formulation inaccordance to EC 2 in order to verify the experimental results. From the results, it was observedthat the RC beam with 45 degree inclined shear reinforcement improved structural performancein shear by approximately 20% and thus prolong the shear failure behaviour as compared to theRC beam with vertical links.

On shear failure behaviors of an armor steel over a large range of strain rates

A newly-designed double shear specimen (Xu et al. A novel method in dynamic shear testing of bulk materials using the traditional SHPB technique, Int. J. Impact Eng. 101: 90–104) is used in this work to study shear failure behaviors of the 603 armor steel with shear strain rate ranging from 0.001 s−1 to 45,000 s−1. Shear stress–shear strain curves are obtained at each strain rate until fracture initiates in the shear zone. It's observed that the failure strains drop abruptly while the failure stresses increase only slightly with strain rates, which means that the material tends to fail more easily at higher strain rates. With the aid of numerical simulation, it's found that in the shear zone a shear dominated stress state is formed, and the values of stress triaxiality and Lode angle parameter are quite low. Fractographic examination shows that under simple shear condition, the failure process of the material is controlled by totally different micro-mechanisms. With the increase of strain rates, the failure characteristics transform clearly from elongated dimples to adiabatic shear bands, which provide a reasonable explanation to the mechanical responses of the material. The results show that the mechanical behaviors of materials should be tested over a wide range of strain rates, and at the same time the data consistency and comparability should be kept, to set up a foundation for engineering computation and to guide the safety design.

Flexural shear behaviour of reinforced Crumbed Rubber Concrete beam

This paper investigates the flexural shear behaviour of reinforced beams made from different Crumbed Rubber Concrete (CRC) mixes having similar compressive strength and different proportions of crumbed rubber. As part of the study concrete beam specimens, made from six different CRC mixes, were prepared and tested to failure under flexural load. For each mix, one beam with a large amount of shear reinforcement and another one without any shear reinforcements were used to distinguish between their bending and shear failure behaviour clearly. The experimental results allowed the comparison between the shear failure behaviour of beams with different CRC mixes. The measured shear capacities were used to examine the applicability and accuracy of available design guidelines for conventional concrete on predicting the shear capacity of reinforced CRC beams. The experimental results were also used to determine the adequacy of existing conventional concrete material models to numerically simulate the shear behaviour of CRC beams using finite element analysis.

Numerical Analysis for the Progressive Failure of Binary-Medium Interface under Shearing

Binary-medium specimens were fabricated using the particle flow code, and the shear strength, dilatancy, and failure behavior of the binary-medium specimens with different bond strength ratios (0.25, 0.5, 0.75, and 1.0) under different normal stresses were studied. Numerical results show that the bond strength ratio and normal stresses considerably influence the shear strengths of binary-medium interface. Shear strength increases as the bond strength ratio and normal stress increase. The dilation of interfaces with high bond strength ratios is more evident than those of interfaces with lower bond strength ratios, and the curves for the high bond strength ratio exhibit remarkable fluctuations during the residual stage. At increased normal stress and bond strength ratio, the peak dilation angle shows decreasing and increasing trends successively. In this study, the specimens exhibited three kinds of failure modes. In mode II, the sawtooth experienced shear failure, but some tensile cracks appeared on the interface of the binary-medium. In mode III, no sawtooth was cut off, indicating tensile failure on the interface. At a low bond strength ratio, damage or failure is mostly concentrated in the upper part of the model. Failure parts gradually transfer to the lower part of the model when the bond strength ratio and normal stress increase. Furthermore, evident tensile cracks occur on the interface. When the bond strength ratio reaches 1.0, the failure mode of the specimen gradually transforms from sheared-off failure to chip-off failure. The number of microcracks in the specimens indicates that the lower the bond strength ratio, the more severe the damage on the specimens.

Tensile and shear failure behaviour of compacted clay – hybrid failure mode

Tensile and shear behaviour of unsaturated soil have been investigated separately in the past. However, there is no comprehensive study on the transition from tensile to shear failure in compacted clayey soils. A series of uniaxial tensile, direct shear and triaxial compression tests were conducted on compacted Regina clay specimens to investigate the strength mobilisation and failure mode under different loading paths. It was observed that the matric suction increases the apparent cohesion and tensile strength of the material. At a given constant matric suction, the compacted clay displays a transition from tensile to shear failure with increasing confining stress which can be approximated by a bilinear failure envelope encompassing the transitional behaviour. The friction angles in tensile regime are greater than those in compressive regime, which can be explained by the transitional change in failure surface morphology from tensile ruptured to shear smoothened one.

Shear Failure of Patched Reinforced Concrete Beam without Web Reinforcements

Degradation of reinforced concrete (RC) element could lead to a reduction of its strength and serviceability. The degradation may be identified in the form of spalling of concrete cover. For the case of RC beam, spalling of concrete cover could occur at the web of the shear span due to corrosion of the web reinfocements. The shear strength of the damaged-RC beam possibly will become less conservative compared to the corresponding flexural strength with a risk of brittle failure. Patch repair could be a choice to recover the size and strength of the damaged-RC beam. This research investigates the shear failure of patched RC beam without web reinforcements with a particular interest to compare the shear failure behaviour of patched RC beam and normal RC beam. The patch repair material used in this research was unsaturated polyester resin (UPR) mortar. The results indicate that the initial diagonal cracks leading to shear failure of patched RC beam occur at a lower level of loading. However, the patched RC beam could carry a greater load before the diagonal crack propagates in length and width causing the beam to fail in shear.

Shear bearing of cross-plate joints between diaphragm wall panels – I: model tests and shear behaviour

This paper, the first part of two companion papers, describes a test programme involving seven specimens and experiments to investigate the effect of three main design parameters of longitudinal steel plates in cross-plate joints on the shear capacity. The load–displacement relationship, cracking of the concrete and strain of the longitudinal steel plate were experimentally measured. It was found that the failure modes of the specimens can be categorised into two types – concrete crushing and steel plate yielding. The failure mode is mainly affected by the relative stiffness of the cross-plate joints, while the ultimate shear load is primarily influenced by the number and area ratio of holes in the longitudinal plates. The paper shows that the available analytical expression for the shear capacity of rib shear connectors cannot be readily applied to cross-plate joints, and therefore further investigations should be conducted to develop a new shear capacity prediction formula for cross-plate joints. This experimental study on the performance of concrete diaphragm walls with cross-plate joints sheds light on the shear failure behaviour of diagram walls and provides some benchmark data for numerical analysis and development of empirical design formulae.

Seismic behavior of RC cantilever beams under low cyclic loading and size effect on shear strength: An experimental characterization

The main objectives of this study are, on one hand to present an experimental campaign on the seismic shear failure behavior of RC cantilever beams with transverse reinforcement subjected to low-cyclic fatigue loading, and on the other hand to evaluate the possibility of the existence of size effect on the corresponding nominal shear strength of the RC beams. Five groups of geometrically similar RC beams with cross-sectional height ranging from 200mm to 1000mm and a shear-span ratio of 2 were designed and tested. Based on the test results, the seismic shear behavior including the failure patterns, the hysteretic characteristics, the bearing capacity, the ductility capacity, the energy dissipation capacity and stiffness degradation are explored. Moreover, the size effect on the nominal shear strength is studied and discussed. The test results and analyses indicate that, (1) the failure patterns of the RC beams having different structural sizes are very similar; (2) under low-cyclic fatigue loadings, even with the transversal reinforcement, the failure of the RC beams is still brittle; (3) with increasing the structural size of the RC beams, the corresponding nominal shear strength, the safety reserve coefficient and the ductility capacity decrease pronouncedly; (4) the test data on the nominal shear strength is in good agreement with Bažant’s size effect law.

Room and elevated temperature shear strength of sealants for solid oxide fuel cells

The shear strength of glass-ceramic sealants was measured in torsion to aid the developments of robust sealants that can withstand the combined complex stress situation typical for solid oxide fuel cell stacks. The specimens consisted of hour-glass-shaped samples, with the sealant layer in typical application relevant thickness between two steel plates. Partially crystallized sealant materials with either silver particles or 8YSZ fibers as filler material were tested and compared with respect to their shear strength and failure behavior at room and elevated temperatures up to 800°C. The results emphasize the importance of interfacial bonding as well the effect of creep properties of sealant and steel substrates onto the testing results. An outlook on improvements of testing procedure and specimens’ geometry is given.

Experimental study of the friction properties and compressive shear failure behaviors of gas shale under the influence of fluids

Gas shale formation with extremely low porosity and permeability can only be developed economically by using a fracturing treatment to form spatial hydraulic fracture networks. Shearing slip is an important factor during fracture network formation and is controlled by the frictional strength of the fracture surface. A series of experimental studies were performed on shale's frictional coefficient, sliding behaviors and compressive shearing strength. The results showed that (1) normal stress has little effect on the sliding frictional coefficient, but the sliding mode is obviously changed with normal stress. Higher normal stress induces a smoother sliding. (2) Different shale exhibited different friction properties. When the clay content in shale is high enough (higher than 35% in this paper) and most of the clay minerals are smectite or an I/S mixed layer, a lower frictional coefficient will be observed (less than 0.6). Meanwhile, the shale's frictional coefficient was more sensitive to water. Slickwater with a resistance reducer additive can reduce the frictional coefficient to 0.36. (3) Absorbed water (e.g., by capillary force or osmotic pressure) inside the shale can activate the natural cracks in the shale and induce micro-slip under compressive stress conditions. The energy release process will be dispersively distributed, and complex fracture networks tend to form. These results are helpful in revealing the mechanisms of fracture networks formation in shale reservoirs under the combined effects of stress, fracturing fluid, and natural fractures.

Numerical approach for evaluating shear failure behavior of strain hardening cementitious composite member

This paper presents a numerical approach for evaluating the shear failure behavior of strain hardening cementitious composite (SHCC) member. The developed approach can clarify the respective contributions of both contact stress and fiber bridging stress for the shear stress transfer behavior on crack surface of SHCC member, which thus can disclose the contribution of fibers to local shear of SHCC member. In the numerical approach, a shear stress transfer model and shear lattice system are proposed, in which the shear lattice system can appropriately express the shape of crack surface, and the shear stress transfer model can accurately quantify the transferred shear stress on the crack surface of SHCC member, focusing on the contribution from both matrix’s contact effect and fiber bridging effect respectively. The effectiveness of the numerical approach is confirmed through the comparison between the experimental and numerical results.

Influence of loading positions on dynamic shear failure behaviors of RC beams

Influence of loading positions on dynamic shear failure behaviors of RC beams

Study on adhesively-bonded surface of tapered double cantilever specimen made of aluminum foam affected with shear force

Aluminum foam is widely used in diverse areas to minimize the weight and maximize the absorption of shock energy in lightweight structures and various bio-materials. It presents a number of advantages, such as low density, incombustibility, non-rigidity, excellent energy absorptivity, sound absorptivity and low heat conductivity. The aluminum foam with an air cell structure was placed under the TDCB Mode II tensile load by using Landmark equipment manufactured by MTS to examine the shear failure behavior. The angle of the tapered adhesively-bonded surfaces of specimens was designated as a variable, and three models were developed with the inclined angles differing from one another at 6°, 8° and 10°. The specimens with the inclined angles of 6°, 8° and 10° have the maximum reaction forces of 168 N, 194 N when the forced displacements are 6, 5 and 4.2 mm respectively. There are three specimens with the inclined angles of 10°, 8° and 6° in the order of maximum reaction force. As the analysis result, the maximum equivalent stresses of 0.813 MPa and 0.895 MPa happened when the forced displacements of 6 mm and 5 mm proceeded at the models of 6° and 8°, respectively. A simulation was carried out on the basis of finite element method and the experimental design. The results of the experiment and the simulation analysis are shown not different from each other significantly. Thus, only a simulation could be confirmed to be performed in substitution of an experiment, which is costly and time-consuming in order to determine the shearing properties of materials made of aluminum foam with artificial data.

Influence of time-dependence on failure of echelon rock joints through a novel DEM model

This article investigates the time-dependent influence on the shear failure behaviour of parallel rock joints in the echelon arrangement due to chemical weathering, which can be treated as a generalised time-dependency of the rock material. A time-dependent parameter α, identifying the accumulated relative mass removal of bonding material, has been implemented into a novel distinct element method bond contact model. This model is based on a series of mechanical test on bonded aluminium rods with different bond geometries. The numerical direct shear test results of echelon rock joints characterised by different values of α show that increasing time-dependent parameter α can lead to a lower crack initiation and peak stresses. This is accompanied by a growing ratio of the microscopic compressive–shear–torsional (CST) bond failure number of bond failures to the total number of failures, except for the case without weathering influence. High values of α render the material bridge a weaker part to be cut through, generating a large number of CST bond breakages along the central shear axis.

A comprehensive study on the smooth joint model in DEM simulation of jointed rock masses

This paper reports the results from a comprehensive numerical study on the effects of micro-parameters of the smooth joint model (SJM) on the macro-properties and the associated failure modes of synthetic rock masses (SRM) under the uniaxial compression condition using the three-dimensional discrete element method. Important mechanical and geometrical micro-parameters of SJM that show significant effects on the macro-properties and the failure modes of SRM are identified. Strong coupling effects are found to exist between various important micro-parameters so that the eventual sample failure is a result of the complicated interaction among these micro-parameters. A limitation of the current stress-dilatancy relation accounting for the joint roughness effect is also identified. The numerical results presented in this paper are valuable for the evaluation of the current model capability in simulating and predicting the shear failure behavior of rock masses, and the further improvement of the model for its full application to the study of the behavior of real rock masses at the laboratory or field scales.

Shear Evolution of Fiberglass Composites Under Compression

Woven composites can offer mechanical improvements over more traditional engineering materials, yet understanding the complex interplay between the fiber-matrix architecture during loading remains a challenge. This paper investigates the evolution of shear failure behavior during the compression of high performance fiberglass composites with varying resin binders at both quasi-static and dynamic strain rates. All samples are comprised of commercially available woven glass cloth with approximately 56 % fiber volume fraction. Laminates with thermosetting resin binders of silicone, melamine, and epoxy were examined. High-speed imaging reveals that failure occurs within a localized shear band region through multiple fiber-weave matrix interface failure with a characteristic macroscopic angle. The shear evolution was spatially mapped using grayscale histograms of the light intensity in the shear regions, and the resulting characteristic angles were measured and analyzed in the context of a Mohr-Coulomb failure criterion. Optical microscopy and high-speed imaging of the shear formation shows initiation appears due to local instabilities from kinking and microbuckling, influenced by the stacking and interlacing regions of tows.

저하중용 후설치 세트앵커의 전단파괴거동에 관한 매개변수 연구

Post-installed concrete set anchors are installed after the concrete hardened. These anchors increasing usage in development of construction equipment and flexible construction. The anchor loaded in shearing exhibits various failure modes such as steel failure, concrete failure, concrete pryout, depending on the shear strength of steel, the strength of concrete, edge distance and anchor interval, etc,. In this study, the objective is to investigate the effects of the variations like anchor embedment depth, edge distance and concrete strength on experimental and finite element analysis of shear failure behavior of post-installed concrete set anchor for light load embedded in concrete. The results of embedment depth experiments show that concrete strength has much affection on the shallow embedment depth. Concrete strength has no much affection with anchor interval and edge distance parameter and both experimental results occurred same failure mode. By comparing the experimental results that occurred steel failure mode show that as strong as concrete strength are the displacement results are small.

An application of a cohesive fracture model combining compression, tension and shear in soft rocks

A cohesive fracture model considering tension, compression and shear material behaviour is implemented into the hybrid continuum–discrete element method, i.e. Universal Distinct Element Code (UDEC), to simulate possible multiple fracture in soft rocks. The fracture model considers both elastic and inelastic (decomposed to fracture and plastic) displacements. The norm of the effective inelastic displacement is used to control the fracture behaviour. Three numerical examples, including Mode-I, Mode-II and Mixed-mode tests, are conducted to verify the model and its implementation in UDEC. The model is subsequently applied to simulate uniaxial compression and Brazilian disc tests on soft rocks and the results are compared with experimental results. The results indicate that the cohesive fracture model is capable of realistically simulating the combined tensile, shear and mixed-mode failure behaviour applicable to geomaterials.