Bond degradation of corroded reinforcement: an experimental and numerical study

Abdellatef, Mohammed; Salem, Elsayed Mohamed; Lau, David T.; Stenroos, Lauren; Alnaggar, Mohammed

doi:10.21012/fc9.048

“…In addition, this high level of stress means clearly that rebar-concrete slippage probably occurred in the experiments. While LDPM was recently extended to capture bond-slip behavior [108], due to lack of enough experimental data, this phenomenon was neglected in this study. The possibility of slippage supports the explanation of why the simulated RRC1 and RRC2 deflections are larger than the experimental ones.…”

Section: Discussion Of Resultsmentioning

confidence: 99%

Modeling Time-Dependent Behavior of Concrete Affected by Alkali Silica Reaction in Variable Environmental Conditions

Alnaggar¹,

Luzio²,

Cusatis

³

2017

Preprint

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Alkali Silica Reaction (ASR) is known to be a serious problem for concrete worldwide, especially in high humidity and high temperature regions. ASR is a slow process that develops over years to decades and it is influenced by changes in environmental and loading conditions of the structure. The problem becomes even more complicated if one recognizes that other phenomena like creep and shrinkage are coupled with ASR. This results in synergistic mechanisms that can not be easily understood without a comprehensive computational model. In this paper, coupling between creep, shrinkage and ASR is modeled within the Lattice Discrete Particle Model (LDPM) framework. In order to achieve this, a multi-physics formulation is used to compute the evolution of temperature, humidity, cement hydration, and ASR in both space and time, which is then used within physics-based formulations of cracking, creep and shrinkage. The overall model is calibrated and validated on the basis of experimental data available in the literature. Results show that even during free expansions (zero macroscopic stress), a significant degree of coupling exists because ASR induced expansions are relaxed by meso-scale creep driven by self-equilibriated stresses at the meso-scale. This explains and highlights the importance of considering ASR and other time dependent aging and deterioration phenomena at an appropriate length scale in coupled modeling approaches.

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“…In addition, this high level of stress means clearly that rebar-concrete slippage probably occurred in the experiments. While LDPM was recently extended to capture bond-slip behavior [ 111 ], due to lack of enough experimental data, this phenomenon was neglected in this study. The possibility of slippage supports the explanation of why the simulated RRC1 and RRC2 deflections are larger than the experimental ones.…”

Section: Discussion Of Resultsmentioning

confidence: 99%

Modeling Time-Dependent Behavior of Concrete Affected by Alkali Silica Reaction in Variable Environmental Conditions

Alnaggar

¹

,

Luzio

²

,

Cusatis

³

2017

Self Cite

View full text Add to dashboard Cite

Alkali Silica Reaction (ASR) is known to be a serious problem for concrete worldwide, especially in high humidity and high temperature regions. ASR is a slow process that develops over years to decades and it is influenced by changes in environmental and loading conditions of the structure. The problem becomes even more complicated if one recognizes that other phenomena like creep and shrinkage are coupled with ASR. This results in synergistic mechanisms that can not be easily understood without a comprehensive computational model. In this paper, coupling between creep, shrinkage and ASR is modeled within the Lattice Discrete Particle Model (LDPM) framework. In order to achieve this, a multi-physics formulation is used to compute the evolution of temperature, humidity, cement hydration, and ASR in both space and time, which is then used within physics-based formulations of cracking, creep and shrinkage. The overall model is calibrated and validated on the basis of experimental data available in the literature. Results show that even during free expansions (zero macroscopic stress), a significant degree of coupling exists because ASR induced expansions are relaxed by meso-scale creep driven by self-equilibriated stresses at the meso-scale. This explains and highlights the importance of considering ASR and other time dependent aging and deterioration phenomena at an appropriate length scale in coupled modeling approaches.

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“…In the elastic regime, the normal stress is proportional to the normal strain through a parameter

termed the normal modulus, and the shear stresses are proportional to the shear strains through

where

(

effective normal modulus) and

is the product of

and

(

shear-normal coupling parameter). The three strain components are corrected by eigenstrain values, which might arise from a variety of phenomena such as, but not limited to thermal strains, shrinkage [ 26 ], expansion due to alkali-silica reaction (ASR) [ 20 ] or corrosion [ 27 ]. Visco-elasticity is treated as a standard elasticity problem by introducing additionally equivalent eigenstrains for the creep-related increase in strains.…”

Section: Modeling Bonded Anchors At Different Scalesmentioning

confidence: 99%

“…A stress-slip constitutive model [ 27 ] describes the interaction between concrete particles and the beam elements representing the anchor. These beam elements are placed inside the concrete domain without actually modeling a borehole, a convenient and computationally-effective simplification that has been shown to suffice for many practical problems associated with reinforced or prestressed concrete.…”

Section: Modeling Bonded Anchors At Different Scalesmentioning

confidence: 99%

“…At the midpoint of every segment, a control point is placed obtaining

. This formulation can be extended to different constitutive equations such as the one used for modeling rebars subjected to corrosion [ 27 ], fiber-reinforced concrete [ 29 , 30 ] or the one used for bonded anchors presented in the next paragraphs.…”

Section: Modeling Bonded Anchors At Different Scalesmentioning

confidence: 99%

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Modeling Adhesive Anchors in a Discrete Element Framework

Marcon

¹

,

Vorel

²

,

Ninčević

³

2017

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In recent years, post-installed anchors are widely used to connect structural members and to fix appliances to load-bearing elements. A bonded anchor typically denotes a threaded bar placed into a borehole filled with adhesive mortar. The high complexity of the problem, owing to the multiple materials and failure mechanisms involved, requires a numerical support for the experimental investigation. A reliable model able to reproduce a system’s short-term behavior is needed before the development of a more complex framework for the subsequent investigation of the lifetime of fasteners subjected to various deterioration processes can commence. The focus of this contribution is the development and validation of such a model for bonded anchors under pure tension load. Compression, modulus, fracture and splitting tests are performed on standard concrete specimens. These serve for the calibration and validation of the concrete constitutive model. The behavior of the adhesive mortar layer is modeled with a stress-slip law, calibrated on a set of confined pull-out tests. The model validation is performed on tests with different configurations comparing load-displacement curves, crack patterns and concrete cone shapes. A model sensitivity analysis and the evaluation of the bond stress and slippage along the anchor complete the study.

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Bond degradation of corroded reinforcement: an experimental and numerical study

Cited by 6 publications

References 6 publications

Modeling Time-Dependent Behavior of Concrete Affected by Alkali Silica Reaction in Variable Environmental Conditions

Modeling Time-Dependent Behavior of Concrete Affected by Alkali Silica Reaction in Variable Environmental Conditions

Modeling Time-Dependent Behavior of Concrete Affected by Alkali Silica Reaction in Variable Environmental Conditions

Modeling Adhesive Anchors in a Discrete Element Framework

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