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Xin Cheng - One of the best experts on this subject based on the ideXlab platform.
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deformation of a Concrete Matrix subject to a cyclic freeze thaw process
RSC Advances, 2016Co-Authors: Peng Du, Lei Wang, Dongyu Xu, Zonghui Zhou, Shifeng Huang, Xin ChengAbstract:The cyclic freeze–thaw process has been recognized as one of the most primary factors leading to structural and function failure of Concrete. Strain, which may have certain inherent advantages when compared to traditional test parameters such as real-time non-destructive monitoring, which is more accurate and continuous with little error caused by manual intervention, was used to characterize the deformation and deterioration of a Concrete Matrix under a cyclic freeze–thaw process in this study. With the cyclic freeze–thaw process, the strain hysteretic loop is raised upwards indicating that residual strain is generated in the Concrete Matrix. The residual strain generated proves that damage in the Concrete Matrix is continuously accumulated and an irreversible deterioration process. The variation of freeze characteristic temperature ΔTf and the apparent frost heaving coefficient Δαf defined in this study can be used to characterize the degree of freeze–thaw damage and the frost resistance of Concrete, respectively. Through theoretical analysis, a numerical model, which can show the relationship between Concrete freeze–thaw damage and residual strain has been deducted and verified, which indicates that residual strain can be used to characterize the frost resistance of Concrete subjected to a cyclic freeze–thaw process such as traditional parameters. Moreover, the residual strain generated in 3.5 wt% NaCl solution is larger than in water, showing that chloride attack accelerates the freeze–thaw damage of Concrete.
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Deformation of a Concrete Matrix subject to a cyclic freeze–thaw process
RSC Advances, 2016Co-Authors: Peng Du, Lei Wang, Dongyu Xu, Zonghui Zhou, Shifeng Huang, Xin ChengAbstract:The cyclic freeze–thaw process has been recognized as one of the most primary factors leading to structural and function failure of Concrete. Strain, which may have certain inherent advantages when compared to traditional test parameters such as real-time non-destructive monitoring, which is more accurate and continuous with little error caused by manual intervention, was used to characterize the deformation and deterioration of a Concrete Matrix under a cyclic freeze–thaw process in this study. With the cyclic freeze–thaw process, the strain hysteretic loop is raised upwards indicating that residual strain is generated in the Concrete Matrix. The residual strain generated proves that damage in the Concrete Matrix is continuously accumulated and an irreversible deterioration process. The variation of freeze characteristic temperature ΔTf and the apparent frost heaving coefficient Δαf defined in this study can be used to characterize the degree of freeze–thaw damage and the frost resistance of Concrete, respectively. Through theoretical analysis, a numerical model, which can show the relationship between Concrete freeze–thaw damage and residual strain has been deducted and verified, which indicates that residual strain can be used to characterize the frost resistance of Concrete subjected to a cyclic freeze–thaw process such as traditional parameters. Moreover, the residual strain generated in 3.5 wt% NaCl solution is larger than in water, showing that chloride attack accelerates the freeze–thaw damage of Concrete.
G. Ruiz - One of the best experts on this subject based on the ideXlab platform.
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Cohesive modeling of dynamic fracture in reinforced Concrete
Computers and Concrete, 2008Co-Authors: Rena C. Yu, Xiaoxin Zhang, G. RuizAbstract:In this work we simulate explicitly the dynamic fracture propagation in reinforced Concrete beams. In particular, adopting cohesive theories of fracture with the direct simulation of fracture and fragmentation, we represent the Concrete Matrix, the steel re-bars and the interface between the two materials explicitly. Therefore the crack nucleation within the Concrete Matrix, through and along the re-bars, the deterioration of the Concrete-steel interface are modeled explicitly. The numerical simulations are validated against experiments of three-point-bend beams loaded dynamically under various strain rates. By extracting the crack-tip positions and the crack mouth opening displacement history, a two-stage crack propagation, marked by the attainment of the peak load, is observed. The first stage corresponds to the stable crack advance, the second one, the unstable collapse of the beam.
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NUMERICAL MODELING OF DYNAMIC CRACK PROPAGATION IN REINFORCED Concrete
2007Co-Authors: G. Ruiz, Etsi De CaminosAbstract:In this work we simulate explicitly the dynamic fracture propagation in reinforced Concrete beams. We represent the Concrete Matrix, the steel re-bars and the interface between the two materials explicitly. Therefore the crack nucleation within the Concrete Matrix, through and along the re-bars, the deterioration of the Concrete-steel interface are modeled explicitly. The numerical simulations are validated against experiments of three-point-bend beams loaded dynamically under various strain rates. The numerical results suggest a two-stage crack propagation. The rst stage corresponds to the stable crack advance, the second one, the unstable collapse of the beam.
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Explicit finite element modeling of static crack propagation in reinforced Concrete
International Journal of Fracture, 2006Co-Authors: Rena C. Yu, G. RuizAbstract:We propose a methodology to model complex fracture processes in reinforced Concrete beams subjected to static loading. The discrete cohesive approach, accompanied by an insertion algorithm, is adopted and a modified dynamic relaxation method is chosen as an alternative solver. The Concrete Matrix and steel re-bars are modeled explicitly; the connection in between is represented by means of interface elements. Such elements allow for slip of re-bars and transmit forces to the Matrix that may generate secondary cracking around the reinforcement. The methodology is validated against three-point bending tests on lightly reinforced Concrete (LRC) beams.
Amjad Khabaz - One of the best experts on this subject based on the ideXlab platform.
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Monitoring of impact of hooked ends on mechanical behavior of steel fiber in Concrete
Construction and Building Materials, 2016Co-Authors: Amjad KhabazAbstract:Abstract The efficiency of hardened composite of Steel Fiber Reinforced Concrete (SFRC) is mainly related to the ability of its components to work together homogeneously. This homogeneously work of SFRC components might be obtained through sufficient bond between the fiber and the Concrete Matrix at its contact points on the interface surfaces. Usually, if a smooth and straight steel fiber is embedded in Concrete Matrix and subjected to tensile force, only weak bond may obtain at the interface between the fiber and the Concrete. This weak bond decreases gradually parallel with increasing the value of the applied tensile force in the pull-out test, and the fiber can’t develop its yield strength, whereas debond length increases toward the depth of the Concrete along the embedded length of the fiber until failure occurs in bond strength between the fiber and the Concrete, then the fiber pulls out of the Concrete through frictional sliding movement. The fracture mechanism of bond strength between the fiber and the Concrete might be observed through pull-out tests. To enhance the bond strength performance of the fiber without change the Concrete mix properties, it is necessary to find sophisticated form for the fiber such as end hooks. Monitoring of impact of hooked ends on mechanical behavior of steel fiber in Concrete is observed during this research, where various pull-out experiments of single steel fiber in two forms (straight and hooked ends) are set using different values of embedded fiber length in Concrete Matrix. As well as computer simulations of single steel fiber with hooked ends embedded in Concrete Matrix are created using finite element model to monitor the development of stresses in different directions. Nonlinear results with contour maps and curves of different types of stresses are also obtained from the computer simulations, and numerical evaluation of the impact of enhancing the steel fiber shape has been done through this research.
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Impact of fiber shape on mechanical behavior of steel fiber in fiber reinforced Concrete FRC
2015Co-Authors: Amjad KhabazAbstract:Fiber pull-out process is the main micro-mechanism that governs post-cracking behaviour of short steel fiber reinforced Concrete structural beams. A detailed analysis of the fiber pull-out process provides understanding about the role of different micro-mechanisms involved in the pull-out process and leads to conclusions about the optimal fiber shape as well as the optimal properties of the Matrix. Different steel fiber shapes involve different micro-mechanisms in the pull-out process. Initially fibers and the surrounding Concrete Matrix deform elastically. The linear elastic behaviour of the fiber-Matrix system is interrupted by interface debonding which occurs due to overall weak bonding between the Concrete Matrix and the surface of the steel fiber. Shear crack propagates and the interface debonding continues untill whole length of the fiber has parted from the surronding Concrete Matrix. At that point the further applied pull-out load is resisted only by friction forces resulting from fiber sliding out of the Concrete Matrix. In some cases, if steel fibers have sophisticated form (e.g., end hooks or corrugated form) , much of the pull-out resistance can be achieved from straightening of the fibers. Straightening of steel fibers can only be possible if the surrounding Concrete Matrix has sufficiently enough strength to resist stress concentration at fiber edges. If surrounding Concrete Matrix is weak, the stress concentration causes failure of the brittle Matrix and no pull-out resistance is obtained. Concrete Matrix failure (spalling) is more likely to happen for cases with larger fiber diameters. This paper introduces experimental study relevant to impact of fiber shape on mechanical behavior of steel fiber in fiber reinforced Concrete FRC using three femouse steel fiber types and different cases of embedded length into Concrete Matrix.
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Determination of Friction Coefficient between Glass Fiber and the Concrete Fri (GF.C)
International Journal of Materials Science and Applications, 2014Co-Authors: Amjad KhabazAbstract:The friction forces between glass fiber and the Concrete in the case of Fiber Reinforced Concrete F.R.C are considered as the main factor to generate the bonding between these two building construction materials. In the case of using glass fiber as reinforcement material to improve the resistance capacity of plain Concrete under an axial or flexural tension forces, bonding forces at the interface between the glass fiber and the Concrete Matrix must be satisfactory. Bonding forces between these two materials are generated due to friction forces at the interface; therefore the final evaluation of the bonding forces is related with the real value of the friction forces, consequently the friction coefficient value between glass fiber and the Concrete is important to evaluate and calculate the real value of friction forces. This paper is devoted to introduce an experimental studies about the mechanism of glass fiber removing from Concrete Matrix which are named (pull-out tests) as well as a programming simulations prepared to represent this mechanism too, theses laboratory experiments and computer simulations have been used in determination process of the friction coefficient value between the glass fiber and the Concrete Matrix Fri(GF.C).
Peng Du - One of the best experts on this subject based on the ideXlab platform.
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deformation of a Concrete Matrix subject to a cyclic freeze thaw process
RSC Advances, 2016Co-Authors: Peng Du, Lei Wang, Dongyu Xu, Zonghui Zhou, Shifeng Huang, Xin ChengAbstract:The cyclic freeze–thaw process has been recognized as one of the most primary factors leading to structural and function failure of Concrete. Strain, which may have certain inherent advantages when compared to traditional test parameters such as real-time non-destructive monitoring, which is more accurate and continuous with little error caused by manual intervention, was used to characterize the deformation and deterioration of a Concrete Matrix under a cyclic freeze–thaw process in this study. With the cyclic freeze–thaw process, the strain hysteretic loop is raised upwards indicating that residual strain is generated in the Concrete Matrix. The residual strain generated proves that damage in the Concrete Matrix is continuously accumulated and an irreversible deterioration process. The variation of freeze characteristic temperature ΔTf and the apparent frost heaving coefficient Δαf defined in this study can be used to characterize the degree of freeze–thaw damage and the frost resistance of Concrete, respectively. Through theoretical analysis, a numerical model, which can show the relationship between Concrete freeze–thaw damage and residual strain has been deducted and verified, which indicates that residual strain can be used to characterize the frost resistance of Concrete subjected to a cyclic freeze–thaw process such as traditional parameters. Moreover, the residual strain generated in 3.5 wt% NaCl solution is larger than in water, showing that chloride attack accelerates the freeze–thaw damage of Concrete.
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Deformation of a Concrete Matrix subject to a cyclic freeze–thaw process
RSC Advances, 2016Co-Authors: Peng Du, Lei Wang, Dongyu Xu, Zonghui Zhou, Shifeng Huang, Xin ChengAbstract:The cyclic freeze–thaw process has been recognized as one of the most primary factors leading to structural and function failure of Concrete. Strain, which may have certain inherent advantages when compared to traditional test parameters such as real-time non-destructive monitoring, which is more accurate and continuous with little error caused by manual intervention, was used to characterize the deformation and deterioration of a Concrete Matrix under a cyclic freeze–thaw process in this study. With the cyclic freeze–thaw process, the strain hysteretic loop is raised upwards indicating that residual strain is generated in the Concrete Matrix. The residual strain generated proves that damage in the Concrete Matrix is continuously accumulated and an irreversible deterioration process. The variation of freeze characteristic temperature ΔTf and the apparent frost heaving coefficient Δαf defined in this study can be used to characterize the degree of freeze–thaw damage and the frost resistance of Concrete, respectively. Through theoretical analysis, a numerical model, which can show the relationship between Concrete freeze–thaw damage and residual strain has been deducted and verified, which indicates that residual strain can be used to characterize the frost resistance of Concrete subjected to a cyclic freeze–thaw process such as traditional parameters. Moreover, the residual strain generated in 3.5 wt% NaCl solution is larger than in water, showing that chloride attack accelerates the freeze–thaw damage of Concrete.
Lucie Vandewalle - One of the best experts on this subject based on the ideXlab platform.
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short term and creep pull out behavior of polypropylene macrofibers at varying embedded lengths and angles from a Concrete Matrix
Construction and Building Materials, 2017Co-Authors: Rutger Vrijdaghs, Marco Di Prisco, Lucie VandewalleAbstract:Abstract This paper reports on the short-term and creep pull-out behavior of different polypropylene fibers from a Concrete Matrix. 85 displacement controlled tests are carried out for two types of fibers with different embedded lengths and angles. Additionally, 15 creep tests are performed in a climate controlled room at different load ratios to study long-term loading effects. The pull-out tests show that an increase in the embedded length of the fiber increases the maximum pull-out force. More inclined fibers with respect to the load application direction initially increase the pull-out force as well, but the fibers tend to rupture more at the Concrete surface, leading to a brittle failure mode. Furthermore, an oscillating post-peak behavior is observed during pull-out which is related to the embossed surface profile of the fibers. The profile is gradually abraded during the test which in turn leads to a pure-friction controlled pull-out behavior at large relative displacements. The pull-out creep tests show that the behavior strongly depends on the load ratio, with higher loads decreasing the failure time. A novel positive feedback loop mechanism is proposed to qualitatively explain the pull-out creep behavior in which the fiber creep deformations are the driving force behind pull-out creep.