The Experts below are selected from a list of 73434 Experts worldwide ranked by ideXlab platform
Naj Aziz - One of the best experts on this subject based on the ideXlab platform.
-
A New Equation for the Shear Strength of Cable Bolts Incorporating the Energy Balance Theory
Geotechnical and Geological Engineering, 2017Co-Authors: Haleh Rasekh, Ali Mirzaghorbanali, Jan Nemcik, Naj AzizAbstract:The application of cable bolts as a secondary support system is an increasing trend in underground coal mines worldwide. The performances of cable bolts have been evaluated under both axial and Shear loading conditions. Two methods of testing cables for Shear, single and double Shear, have been recognised. This paper examines the Shear Behaviour of a variety of cable bolts under different pre-tension loads by double Shear testing. Plain, spiral and the combination of both cable types were used in this study. The initial axial load and the type of cable bolts are the main factors affecting their Shear strength. By increasing the axial pre-tension load, the peak Shear load occurs at lower Shear displacement. The failure angle due to cable bending across the joint at different pre-tension loads varied between 41° and 49°. This demonstrates that the ratio of axial and perpendicular displacements is almost constant and on average the failure occurs at about 45°. A novel analytical model is proposed to evaluate the Shear Behaviour of pre-tensioned fully grouted cable bolts subjected to double Shearing. Energy and Fourier Series methods were incorporated in the model to simulate the Shear Behaviour of cable bolts. The comparison of the experimental results with the proposed model shows a good agreement.
-
effects of Shear rate on cyclic loading Shear Behaviour of rock joints under constant normal stiffness conditions
Rock Mechanics and Rock Engineering, 2014Co-Authors: Ali Mirzaghorbanali, Jan Nemcik, Naj AzizAbstract:The presence of joints and discontinuities within a rock mass can significantly affect its mechanical Behaviour and therefore the stability of structures constructed at close proximity. Several studies have been carried out by previous researchers to understand the mechanical Behaviour of joints under both constant normal load (CNL) conditions, in which the normal load remains unchanged during Shearing, and constant normal stiffness (CNS) conditions to imitate the stiffness of the surrounding rock mass (Patton 1966; Ladanyi and Archambault 1969; Barton 1973, 1976; Seidel and Haberfield 1995; Indraratna and Haque 2000; Buzzi et al. 2008). The importance of CNS conditions to simulate the actual Shear Behaviour of rock joints in the field has been described by Johnston and Lam (1989), Skinas et al. (1990) and Indraratna et al. (1998). The above-mentioned studies focussed only on the monotonic loading Shear Behaviour of rock joints. The effects of cyclic loading on the Shear Behaviour of rock joints in earthquakes and blasting were investigated in detail by Plesha (1987), Hutson and Dowding (1990), Lee et al. (2001), Stupkiewicz and Mroz (2001), Grasselli and Egger (2003), Jafari et al. (2003) and Belem et al. (2009). As the Shear rate might vary depending on the source of the load and rock media, Crawford and Curran (1981) carried out a series of experiments on artificial rock joints with various Shear rates and normal stresses under CNL conditions. Based on the measured data, they concluded that the Shear rate may influence the Shear strength of hard and soft rock joints differently. In another study, Jafari et al. (2004) verified the results of Crawford and Curran (1981) for Shear rates between 0.05 and 0.4 mm/min under monotonic loading. None of these researchers investigated the effects of Shear rate on the cyclic loading Shear Behaviour of rock joints under CNS conditions, which is a critical issue in stability analysis of underground structures subjected to seismic events. Accordingly, three sets of cyclic loading Shear tests with various Shear rates and initial normal stresses were conducted on artificial triangular joints under CNS conditions. In this study, the experimental data are critically analysed.
-
Shear Behaviour of idealized infilled joints under constant normal stiffness
Geotechnique, 1999Co-Authors: Buddhima Indraratna, Asadul Haque, Naj AzizAbstract:The Shear Behaviour of soft joints containing infill materials was investigated in the laboratory under constant normal stiffness (CNS) conditions. Tests were conducted on joints with asperities having inclinations of 9·5° (type 1) and 18·5° (type II), under a given range of initial normal stresses (σno) 0·30 to 1·10 MPa, and at a constant normal stiffness of 8·5, Kn/mm. It was found that the Shear strength of joints decreases considerably even with the addition of a thin layer of infill. Results also show that the effect of asperities on Shear strength is significant up to an asperity height to infill thickness (t/a) ratio of 1·4—1·8, whereas the Shear Behaviour is controlled by the infill alone beyond this critical ratio. The Shear displacement corresponding to the peak Shear stress is considerably reduced once the infill starts to govern the Shear Behaviour of the joint. In this study, the drop in peak Shear stress under CNS conditions has been modelled by a hyperbolic relationship. In relation to ‘cle...
Gideon P A G Van Zijl - One of the best experts on this subject based on the ideXlab platform.
-
improved mechanical performance Shear Behaviour of strain hardening cement based composites shcc
Cement and Concrete Research, 2007Co-Authors: Gideon P A G Van ZijlAbstract:The retardation of moisture and gas ingress associated with important degradation mechanisms in cement-based composites in general and reinforced concrete or prestressed concrete in particular is an ongoing research focus internationally. A dense outer layer is generally accepted to significantly enhance durability of structural concrete. However, cracking leads to enhanced ingress, unless the cracks are restricted to small widths. Strain-hardening cement-based composites (SHCC) make use of fibres to bridge cracks, whereby they are controlled to small widths over a large tensile deformation range. In this paper, SHCC Shear Behaviour is studied, verifying that the cracks which arise in pure Shear are also controlled to small widths in these materials. The design of an Iosipescu Shear test setup and specific SHCC geometry is reported, as well as the results of a test series. A computational model for SHCC, based on finite element theory and continuum damage mechanics, is elaborated and shown to capture the Shear Behaviour of SHCC.
-
characterising the Shear Behaviour of strainhardening fibre reinforced cement based composites technical paper
Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese, 2007Co-Authors: Q Shang, Gideon P A G Van ZijlAbstract:Strain-hardening fibre-reinforced cement-based composites (SHCC) are a class of fibre-reinforced concrete (FRC) that, reinforced with relatively low volumes of short fibres, exhibit strain-hardening, tough tensile and flexural response. These qualities hold promise also for ductile, superior Shear Behaviour, which has been demonstrated in experimental projects internationally. The potential reduction or elimination of conventional steel Shear reinforcement in reinforced concrete by the use of FRC, and in particular SHCC, is an example of how the tensile ductility properties of SHCC may be exploited. Other uses include generally improved ductility and durability of structures by selective use of these superior construction materials. However, the true Shear Behaviour of SHCC is not yet understood and analytical and design models have not yet been formulated due to a lack of an appropriate, accurate direct Shear test method. This paper describes the investigation of the Shear properties of SHCC. A modified Iosipescu Shear test is developed for SHCC by finite element analysis. An experimental program of Shear tests is subsequently reported, which aims to characterise the true Shear mechanisms and properties of SHCC.
Zoltan Major - One of the best experts on this subject based on the ideXlab platform.
-
analysis of the thermomechanical Shear Behaviour of woven reinforced thermoplastic matrix composites during forming
Composites Part A-applied Science and Manufacturing, 2016Co-Authors: Martin Machado, Michael Fischlschweiger, Luca Murenu, Zoltan MajorAbstract:Abstract Shear Behaviour of a glass fibre/polypropylene composite is characterized over a wide range of strain rates and forming temperatures using the bias extension test. A temperature- and rate-dependent material model is here introduced to describe the observed Behaviour. The model is based on a continuous approach and formulated considering a stress objective derivative based on the warp and weft yarns rotation. The effects of temperature and strain rate on the Shear Behaviour are analysed via bias extension test simulations. Temperature change in the sheet during forming was measured. This data is used to model cooling during forming. Isothermal and transient forming simulations were performed in order to show the effects of temperature and forming speed on the obtained Shear angle distribution. It was found that at low forming speeds the assumption of isothermal forming is not valid anymore since the cooling of the sheet affects the Shear Behaviour.
-
a rate dependent non orthogonal constitutive model for describing Shear Behaviour of woven reinforced thermoplastic composites
Composites Part A-applied Science and Manufacturing, 2016Co-Authors: Martin Machado, Michael Fischlschweiger, Zoltan MajorAbstract:Abstract A rate dependent constitutive model for woven reinforced thermoplastic matrix composites at forming temperatures is proposed in this work. The model is formulated using a stress objective derivative based on the fibre rotation. Nonlinear Shear Behaviour is modelled as a polynomial function and the rate dependence is described using a Cowper–Symonds overstress law formulated in terms of Shear angle rate. The model parameters are determined by means of bias extension tests. The applicability of the material model is validated through a forming experiment.
Ali Mirzaghorbanali - One of the best experts on this subject based on the ideXlab platform.
-
A New Equation for the Shear Strength of Cable Bolts Incorporating the Energy Balance Theory
Geotechnical and Geological Engineering, 2017Co-Authors: Haleh Rasekh, Ali Mirzaghorbanali, Jan Nemcik, Naj AzizAbstract:The application of cable bolts as a secondary support system is an increasing trend in underground coal mines worldwide. The performances of cable bolts have been evaluated under both axial and Shear loading conditions. Two methods of testing cables for Shear, single and double Shear, have been recognised. This paper examines the Shear Behaviour of a variety of cable bolts under different pre-tension loads by double Shear testing. Plain, spiral and the combination of both cable types were used in this study. The initial axial load and the type of cable bolts are the main factors affecting their Shear strength. By increasing the axial pre-tension load, the peak Shear load occurs at lower Shear displacement. The failure angle due to cable bending across the joint at different pre-tension loads varied between 41° and 49°. This demonstrates that the ratio of axial and perpendicular displacements is almost constant and on average the failure occurs at about 45°. A novel analytical model is proposed to evaluate the Shear Behaviour of pre-tensioned fully grouted cable bolts subjected to double Shearing. Energy and Fourier Series methods were incorporated in the model to simulate the Shear Behaviour of cable bolts. The comparison of the experimental results with the proposed model shows a good agreement.
-
effects of Shear rate on cyclic loading Shear Behaviour of rock joints under constant normal stiffness conditions
Rock Mechanics and Rock Engineering, 2014Co-Authors: Ali Mirzaghorbanali, Jan Nemcik, Naj AzizAbstract:The presence of joints and discontinuities within a rock mass can significantly affect its mechanical Behaviour and therefore the stability of structures constructed at close proximity. Several studies have been carried out by previous researchers to understand the mechanical Behaviour of joints under both constant normal load (CNL) conditions, in which the normal load remains unchanged during Shearing, and constant normal stiffness (CNS) conditions to imitate the stiffness of the surrounding rock mass (Patton 1966; Ladanyi and Archambault 1969; Barton 1973, 1976; Seidel and Haberfield 1995; Indraratna and Haque 2000; Buzzi et al. 2008). The importance of CNS conditions to simulate the actual Shear Behaviour of rock joints in the field has been described by Johnston and Lam (1989), Skinas et al. (1990) and Indraratna et al. (1998). The above-mentioned studies focussed only on the monotonic loading Shear Behaviour of rock joints. The effects of cyclic loading on the Shear Behaviour of rock joints in earthquakes and blasting were investigated in detail by Plesha (1987), Hutson and Dowding (1990), Lee et al. (2001), Stupkiewicz and Mroz (2001), Grasselli and Egger (2003), Jafari et al. (2003) and Belem et al. (2009). As the Shear rate might vary depending on the source of the load and rock media, Crawford and Curran (1981) carried out a series of experiments on artificial rock joints with various Shear rates and normal stresses under CNL conditions. Based on the measured data, they concluded that the Shear rate may influence the Shear strength of hard and soft rock joints differently. In another study, Jafari et al. (2004) verified the results of Crawford and Curran (1981) for Shear rates between 0.05 and 0.4 mm/min under monotonic loading. None of these researchers investigated the effects of Shear rate on the cyclic loading Shear Behaviour of rock joints under CNS conditions, which is a critical issue in stability analysis of underground structures subjected to seismic events. Accordingly, three sets of cyclic loading Shear tests with various Shear rates and initial normal stresses were conducted on artificial triangular joints under CNS conditions. In this study, the experimental data are critically analysed.
Sofiane Amziane - One of the best experts on this subject based on the ideXlab platform.
-
influence of yield stress and compressive strength on direct Shear Behaviour of steel fibre reinforced concrete
Global Journal on Technology, 2015Co-Authors: Sofiane Amziane, Bensaid Boulekbache, Mostefa Hamrat, Mohamed ChemroukAbstract:This study aims in examining the influence of the paste yield stress and compressive strength on the Behaviour of fibre-reinforced concrete (FRC) versus direct Shear. The parameters studied are the steel fibre contents, the aspect ratio of fibres and the concrete strength. Prismatic specimens of dimensions 10x10x35cm made of concrete of various yield stress reinforced with steel fibres hooked at the ends with three fibre volume fractions (i.e. 0, 0.5 and 1%) and two aspects ratio (65 and 80) were tested to direct Shear. Three types of concretes with various compressive strength and yield stress were tested, an ordinary concrete (OC), a self-compacting concrete (SCC) and a high strength concrete (HSC). The concrete strengths investigated include 30 MPa for OC, 60 MPa for SCC and 80 MPa for HSC. The results show that the Shear strength and ductility are affected and have been improved very significantly by the fibre contents, fibre aspect ratio and concrete strength. As the compressive strength and the volume fraction of fibres increase, the Shear strength increases. However, yield stress of concrete has an important influence on the orientation and distribution of the fibres in the matrix. The ductility was much higher for ordinary and self-compacting concretes (concrete with good workability). The ductility in direct Shear depends on the fibre orientation and is significantly improved when the fibres are perpendicular to the Shear plane. On the contrary, for concrete with poor workability, an inadequate distribution and orientation of fibres occurred, leading to a weak contribution of the fibres to the direct Shear Behaviour. Keywords: concrete, fibre, direct Shear, yield stress, orientation, strength.
-
influence of yield stress and compressive strength on direct Shear Behaviour of steel fibre reinforced concrete
Construction and Building Materials, 2012Co-Authors: Bensaid Boulekbache, Mostefa Hamrat, Mohamed Chemrouk, Sofiane AmzianeAbstract:Abstract This study aims in examining the influence of the paste yield stress and compressive strength on the Behaviour of fibre-reinforced concrete (FRC) versus direct Shear. The parameters studied are the steel fibre contents, the aspect ratio of fibres and the concrete strength. Prismatic specimens of dimensions 10 × 10 × 35 cm made of concrete of various yield stress reinforced with steel fibres hooked at the ends with three fibre volume fractions (i.e. 0%, 0.5% and 1%) and two aspects ratio (65 and 80) were tested to direct Shear. Three types of concretes with various compressive strength and yield stress were tested, an ordinary concrete (OC), a self-compacting concrete (SCC) and a high strength concrete (HSC). The concrete strengths investigated include 30 MPa for OC, 60 MPa for SCC and 80 MPa for HSC. The results show that the Shear strength and ductility are affected and have been improved very significantly by the fibre contents, fibre aspect ratio and concrete strength. As the compressive strength and the volume fraction of fibres increase, the Shear strength increases. However, yield stress of concrete has an important influence on the orientation and distribution of the fibres in the matrix. The ductility was much higher for ordinary and self-compacting concretes (concrete with good workability). The ductility in direct Shear depends on the fibre orientation and is significantly improved when the fibres are perpendicular to the Shear plane. On the contrary, for concrete with poor workability, an inadequate distribution and orientation of fibres occurred, leading to a weak contribution of the fibres to the direct Shear Behaviour.
