scholarly journals An Experimental Study on Mechanical Behavior of Parallel Joint Specimens under Compression Shear

2018 ◽  
Vol 2018 ◽  
pp. 1-12
Author(s):  
Fei Wang ◽  
Ping Cao ◽  
Yu Chen ◽  
Qing-peng Gao ◽  
Zhu Wang
Keyword(s):  
Shear Stress ◽  
Shear Strength ◽  
Failure Mode ◽  
Shear Failure ◽  
Strain Curve ◽  
Shear Loading ◽  
Plane Shear ◽  
Joint Spacing ◽  
Dip Angle ◽  
Joint Inclination

In order to investigate the influence of the joint on the failure mode, peak shear strength, and shear stress-strain curve of rock mass, the compression shear test loading on the parallel jointed specimens was carried out, and the acoustic emission system was used to monitor the loading process. The joint spacing and joint overlap were varied to alter the relative positions of parallel joints in geometry. Under compression-shear loading, the failure mode of the joint specimen can be classified into four types: coplanar shear failure, shear failure along the joint plane, shear failure along the shear stress plane, and similar integrity shear failure. The joint dip angle has a decisive effect on the failure mode of the specimen. The joint overlap affects the crack development of the specimen but does not change the failure mode of the specimen. The joint spacing can change the failure mode of the specimen. The shear strength of the specimen firstly increases and then decreases with the increase of the dip angle and reaches the maximum at 45°. The shear strength decreases with the increase of the joint overlap and increases with the increase of the joint spacing. The shear stress-displacement curves of different joint inclination samples have differences which mainly reflect in the postrupture stage. From monitoring results of the AE system, the variation regular of the AE count corresponds to the failure mode, and the peak value of the AE count decreases with the increase of joint overlap and increases with the increase of joint spacing.

Fabrication and Mechanical Properties of Glass Fiber/Epoxy Nanocomposites

2006 ◽  
Vol 505-507 ◽  
pp. 37-42 ◽  
Author(s):  
Jia Lin Tsai ◽  
Jui Ching Kuo ◽  
Shin Ming Hsu
Keyword(s):  
Mechanical Properties ◽  
Shear Stress ◽  
Shear Strength ◽  
Glass Fiber ◽  
Shear Failure ◽  
Epoxy Nanocomposites ◽  
Plane Shear ◽  
Epoxy Nanocomposite ◽  
Transverse Normal Stress ◽  
Mechanical Mixer

This research is aimed to fabricate glass fiber/epoxy nanocomposites containing organoclay as well as to understand the organoclay effect on the in-plane shear strength of the nanocomposites. To demonstrate the organoclay effect, three different loadings of organoclay, were dispersed in the epoxy resin using mechanical mixer followed by sonication. The corresponding glass/epoxy nanocomposites were prepared by impregnating the organoclay epoxy mixture into the dry glass fiber through a vacuum hand lay-up process. Off-axis block glass/epoxy nanocomposites were tested in compression to produce in-plane shear failure. It is noted only the specimens showing in-plane shear failure mode were concerned in this study. Through coordinate transformation law, the uniaxial failure stresses were then converted to a plot of shear stress versus transverse normal stress from which the in-plane shear strength was obtained. Experimental results showed that the fiber/epoxy nanocomposite exhibit higher in-plane shear strength than the conventional composites. This increased property could be ascribed to the enhanced fiber/matrix adhesion promoted by the organoclay.

Research on Numerical Simulation of High Filling Culverts Foundation Failure Mode

2012 ◽  
Vol 594-597 ◽  
pp. 1257-1262
Author(s):  
Ji Wei Cao ◽  
Cheng Man Sha ◽  
Bin Liu ◽  
Yue Sun
Keyword(s):  
Numerical Simulation ◽  
Shear Stress ◽  
Shear Strength ◽  
Finite Difference ◽  
Finite Difference Method ◽  
Failure Mode ◽  
Shear Failure ◽  
Sliding Surface ◽  
Foundation Soil ◽  
Foundation Failure

Foundation failure mode of high filling culverts involves calculation theory and method of subgrade bearing capacity, and it has great theoretical and practical values. After model of the culvert has been established, finite difference method will be used to do the numerical simulation in FLAC3D. Reaserch suggests that traditional Terzaghi/Meyerhof failure mode are not suitable for relatively deep buried subgrade of high filling culvert. Foundation failure of high filling culvert is caused by difference in stiffness and earth press, which result in settlement difference, and then forms subsidiary shear stress on the sliding surface. When stress value reaches shear strength of the foundation soil, shear failure occured.

scholarly journals Experimental Study on the Shear Performance of Shallow Hinge Joints for Prefabricated Hollow Slab Bridges

2018 ◽  
Vol 2018 ◽  
pp. 1-8
Author(s):  
Hanbin Yi ◽  
Chuanxi Li ◽  
Li Dai
Keyword(s):  
Shear Stress ◽  
Failure Mode ◽  
Shear Failure ◽  
Internal Force ◽  
Force Transmission ◽  
Transmission Performance ◽  
Joint Stress ◽  
Hinge Joint ◽  
Vehicle Load ◽  
Joint Fracture

To investigate whether shallow hinge joint fracture was caused by shear stress or flexural stress, during the demolition and reconstruction of Xiaojiang River bridge, two original girders were collected and shipped to the lab, and the shallow hinge joint between the two girders was rebuilt. Tests were performed to investigate the cracking load, failure mode, and force transmission performance of the hollow slab girder and shallow hinge joint under vehicle load. The test result shows that under eccentric load, when the load increases to 365 kN, the midspan bottom slab of the testing girder starts to fracture; as the load increases to 560 kN, the roof slab of the testing girder starts to fracture; the hinge joint has a maximum horizontal opening of 0.153 mm and vertical relative displacement of 0.201 mm; during the entire test loading process, the shallow hinge joint structure does not develop fracture and shear failure; and the shallow hinge structure demonstrates excellent shear stress transmission performance. In addition, based on hinge slab theory, the hinge joint internal force under vehicle load was calculated. Based on ACI 318-05 specification, CAN/CSA-S6-00, and JTG D61-2005, the hinge joint shear bearing capacity was calculated. Hinge joint stress resistances calculated from the three specifications all exceed the internal force. Among them, the calculation results from ACI 318-05 and CAN/CSA-S6-00 are similar, while the result from JTG D61-2005 specification significantly exceeds the internal force, which is mainly because the designed concrete direct shear strength fvd in the Chinese specification does not consider factors such as bonding surface coarseness, concrete pouring sequence, and material properties. Theoretical calculations and tests show that the actual failure mode of the shallow hinge joint in prefabricated hollow slab girder bridges is not caused by shear stress.

scholarly journals Mechanical Respond and Failure Mode of Large Size Honeycomb Sandwiched Composites under In-Plane Shear Load

Molecules ◽  
2019 ◽  
Vol 24 (23) ◽  
pp. 4248 ◽  
Author(s):  
Wang ◽  
Wang ◽  
Liu ◽  
Zhang ◽  
Wan ◽  
...  
Keyword(s):  
Theoretical Analysis ◽  
Shear Strain ◽  
Failure Mode ◽  
Field Distribution ◽  
Shear Failure ◽  
Buckling Load ◽  
Analysis Method ◽  
Plane Shear ◽  
Large Size ◽  
Honeycomb Sandwich

The present work focuses on the in-plane shear respond and failure mode of large size honeycomb sandwich composites which consist of plain weave carbon fabric laminate skins and aramid paper core. A special size specimen based on a typical element of aircraft fuselage was designed and manufactured. A modified in-plane shear test method and the corresponding fixture was developed. Three large size specimens were tested. The distributed strain gauges were used to monitor the mechanical response and ultimate bearing capacity. The results show that a linear respond of displacement and strain appears with the increase of the load. The average shear failure load reaches 205.68 kN with the shear failure occurring on the face sheet, and the maximum shear strain monitored on the composite plate is up to 16,115 με. A combination of theoretical analysis and finite element method (FEM) was conducted to predict the shear field distribution and the overall buckling load. The out-of-plane displacement field distribution and in-plane shear strain field distribution under the pure shear loading were revealed. The theoretical analysis method was deduced to obtain the variation rule of the shear buckling load. A good agreement was achieved among the experiment, theoretical analysis, and FEM results. It can be concluded that the theoretical analysis method is relatively conservative, and the FEM is more accurate in case of deformation and strain. The results predicted by h element and p element methods are very close. The results of the study could provide data support for the comprehensive promotion of the design and application of honeycomb sandwich composites.

scholarly journals Experimental study on deformation and failure characteristics of discontinuous prefabricated fractured tuff

2019 ◽  
Vol 16 (5) ◽  
pp. 862-874
Author(s):  
Yang Song ◽  
Heping Wang ◽  
Meng Ren
Keyword(s):  
Shear Failure ◽  
Failure Process ◽  
Dissipated Energy ◽  
Uniaxial Compression Test ◽  
Tensile Shear ◽  
Joint Spacing ◽  
Failure Characteristics ◽  
Deformation And Failure ◽  
Peak Intensity ◽  
Dip Angle

Abstract To study more fully the characteristic law of deformation and failure of tuff jointed rock mass of prefabricated parallel discontinuous joint test specimens, the uniaxial compression test was used. The stress–strain curve, peak intensity, deformation parameters, energy characteristics, etc., of the rock test specimens were systematically studied under different combinations of joint dip angle and joint spacing. The research found that: (1) during the failure process of tuff, the peak intensity and elastic modulus followed a U-shaped change pattern and the minimum value was reached when α = 60°; (2) the fracture modes of test specimens with different joint dip angles were different. When α = 30° and 45°, failure characteristics were mixed modes of tensile or tensile shear failure. When α = 60°, failure characteristics were shear. At α = 75°, the failure characteristic was tensile shear failure. (3) The absorbed and dissipated energy of the rock increased nonlinearly at each stage of deformation. (4) We quantified rock energy damage through a correlation between dissipated energy and absorbed energy of the rock in the process of energy evolution, and obtained an evolution of the relationship between the dissipated energy ratio, crack dip angle and crack spacing. Based on different fracture distribution methods and according to the strain equivalence principle, the constitutive equation of the pre-peak rock damage was obtained.

Response of Honeycombs Subjected to In-Plane Shear

2016 ◽  
Vol 83 (6) ◽  
Author(s):  
Youming Chen ◽  
Raj Das ◽  
Mark Battley
Keyword(s):  
Shear Stress ◽  
Shear Strength ◽  
Young’S Modulus ◽  
Cell Walls ◽  
Young's Modulus ◽  
Constitutive Relations ◽  
Length Ratio ◽  
Plane Shear ◽  
Base Materials ◽  
Vertical Cell

Study on the response of honeycombs subjected to in-plane shear helps establish the constitutive relations for honeycombs and shed light on the mechanics of cellular materials. The present study explores the nonlinear elastic response of honeycombs under in-plane shear by analyzing the large deflection of cell walls in a unit cell. Governing equations are established which relate the macroscopic response of honeycombs to the deflection of cell walls. Solving these equations, the behavior of regular honeycombs under in-plane shear along horizontal (X) and vertical (Y) directions was investigated. It is found that the response of regular honeycombs under in-plane shear depends on the nondimensional shear stress which is a parameter combining the thickness-to-length ratio of cell walls, the Young's modulus of base materials, and macroscopic shear stress. Lateral shrinking is a distinctive characteristic for honeycombs under in-plane shear, which should be taken into account when establishing constitutive relations and performing simple shear experiments. Expressions for predicting the shear strength of honeycombs are formulated in this paper. It is noted that the normalized shear strength of regular honeycombs depends on two ratios: the thickness-to-length ratio of cell walls and the ratio of Young's modulus to yield strength of base materials, and the former has a dominant effect. By comparing honeycombs with cell walls of uniform thickness against honeycombs with vertical cell walls of double thickness, it is found that doubling the thickness of vertical cell walls of honeycombs increases their shear strength along horizontal (X) direction nearly twice, but does not improve the shear strength that much along the vertical (Y) direction.

Experimental Research on Failure Modes of Specimen Containing Non-Coplanar Joints

2013 ◽  
Vol 779-780 ◽  
pp. 332-336
Author(s):  
Ping Cao ◽  
Wen Cheng Fan ◽  
Ke Zhang
Keyword(s):  
Shear Strength ◽  
Failure Mode ◽  
Failure Modes ◽  
Cement Mortar ◽  
Failure Process ◽  
Jointed Rock ◽  
Important Relationship ◽  
Initial Setting ◽  
Series Of Experiments ◽  
Dip Angle

To study the failure mechanism and failure mode of jointed rock under compressive-shear, many rock-like material specimens containing non-coplanar joints were made and a series of experiments were carried out. In the experiments, mica sheets were used as joint fillings, cement mortar was selected as rock-like material. Joints were made by inserting the mica sheet in cement mortar before initial setting. Mica sheets were left down as joint fillings. The results of experiments show that the dip angles of major joint have important influence on the failure mode of specimens. And the emerging position of wing cracks which exist in the prophase of specimens failure process changes with the dip angle. The shear strength of specimens has an important relationship with the dip angle of major joints. The smallest shear strength happens in the specimen with a joint angle of 15°, while the biggest value happens in 60°.

Implication of Unbondedness in Reinforced Concrete Beams

2012 ◽  
Vol 587 ◽  
pp. 36-41 ◽  
Author(s):  
S.F.A. Rafeeqi ◽  
S.U. Khan ◽  
N.S. Zafar ◽  
T. Ayub
Keyword(s):  
Shear Strength ◽  
Reinforced Concrete ◽  
Failure Mode ◽  
Shear Failure ◽  
Concrete Beams ◽  
Experimental Results ◽  
Reinforced Concrete Beams ◽  
Rc Beams ◽  
Flexural Capacity ◽  
Flexural Reinforcement

In this paper, behaviour of nine (09) RC beams (including two control beams) after unbonding and exposing flexural reinforcement has been studied which were intentionally designed and detailed to observe flexural and shear failure. Beams have been divided into three groups based on failure mode and unbounded and exposed reinforcement. Beams have been tested under two-point loading up to failure. Experimental results are compared in terms of beam behaviour with respect to flexural capacity and failure mode which revealed that the exposed reinforcement does not altered flexural capacity significantly and unbondedness positively influences shear strength; however, serviceability performance of beams with unbonded and exposed reinforcement is less.

scholarly journals Experimental Study on the Fracture Evolution Processof Rock-like Specimens Containing a Closed RoughJoint Based on 3D-Printing Technology

2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Jiawei Liu ◽  
Haijian Su ◽  
Hongwen Jing ◽  
Chengguo Hu ◽  
Qian Yin
Keyword(s):  
Mechanical Properties ◽  
3D Printing ◽  
Failure Mode ◽  
Shear Failure ◽  
Rock Joints ◽  
Image Correlation ◽  
Printing Technology ◽  
3D Printing Technology ◽  
Joint Inclination ◽  
Joint Length

In order to overcome the disadvantage of traditional joint fabrication method—inability to reproduce the rough surfaces of practical rock joints—3D-printing technology was applied to restructure five kinds of rough joint according to the failure surface formed by the triaxial prepeak unloading test in this study. And uniaxial compression test was carried out on the rock-like specimens containing closed 3D-printing rough joint to study the effects of joint inclination and joint length on the mechanical properties (peak strength, peak strain, elastic modulus, and secant modulus), cracking process, and failure modes. Besides, digital image correlation (DIC) method and acoustic emission (AE) system are used to investigate the whole evolution process of strain fields and crack propagation during loading. It is found that the mechanical parameters decrease first and then go up as the joint inclination increases, while presenting a continuous downward trend with the increase of joint length. Inclination of 45° and the larger joint length bring more extensive reduction to mechanical properties of specimens. Specimens exhibit typical brittle failure characteristics. The failure mode of specimens affected by different joint inclination is tension-shear failure. And the joint scale rises; the failure mode of specimens changes from tensile failure to shear failure. Larger joint scale results in the longer prepeak fluctuation phase on axial stress-strain curves and more dispersed distribution of high-value AE counts.

scholarly journals Experimental Study on Physical-mechanical Properties and Fracture Behaviors of Saturated Yellow Sandstone Considering Coupling Effect of Freeze-Thaw and Specimen Inclination

2020 ◽  
Vol 12 (3) ◽  
pp. 1029 ◽  
Author(s):  
Liang Chen ◽  
Peng Wu ◽  
Yanlong Chen ◽  
Wei Zhang
Keyword(s):  
Mechanical Properties ◽  
Shear Stress ◽  
Elastic Modulus ◽  
Failure Mode ◽  
Inclination Angle ◽  
Compression Strength ◽  
Shear Loading ◽  
Cold Regions ◽  
Freeze Thaw ◽  
Peak Compression

The effect of freeze-thaw on the physical-mechanical properties and fracture behavior of rock under combined compression and shear loading was crucial for revealing the instability mechanism and optimizing the structure design of rock engineering in cold regions. However, there were few reports on the failure behavior of rock treated by freeze-thaw under combined compression and shear loading due to the lack of test equipment. In this work, a novel combined compression and shear test (C-CAST) system was introduced to carry out a series of uniaxial compression tests on saturated yellow sandstone under various inclination angles (θ = 0°, 5°, 10°, and 15°) and the number of freeze-thaw cycles (N = 0, 20, 40, and 60). The test results showed that the P-wave velocity dramatically decreased, while the rock quality and porosity increased gradually as N increased; the peak compression strength and elastic modulus obviously decreased with the increasing θ and N, while the peak shear stress increased gradually with the increasing θ and decreased with the increase of N, indicating that the shear stress component can accelerate the crack propagation and reduce its resistance to deformation. The acoustic emission (AE) results revealed that the change of crack initiation (CI) stress and crack damage (CD) stress with the θ and N had a similar trend as that of the peak compression strength and elastic modulus. Particularly, the CI and CD thresholds at 60 cycles were only 81.31% and 84.47% of that at 0° cycle and indicated a serious freeze-thaw damage phenomenon, which was consistent with the results of scanning electron microscopy (SEM) with the appearance of some large-size damage cracks. The fracture mode of sandstone was dependent on the inclination angle. The failure mode developed from both the tensile mode (0°) and combined tensile-shear mode (5°) to a pure shear failure (10°–15°) with the increasing inclination angle. Meanwhile, the freeze-thaw cycle only had an obvious effect on the failure mode of the specimen at a 5° inclination. Finally, a novel multivariate regression analysis method was used to predict the peak compression strength and elastic modulus based on the initial strength parameters (θ = 0°, N = 0). The study results can provide an important reference for the engineering design of rock subjected to a complex stress environment in cold regions.

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