Crack Propagation In Concrete Research Articles

CARPIUC benchmark overview: crack advance, reorientation, propagation and initiation under complex loadings

A series of experiments has been performed to build a benchmark for the numerical modeling of mixed mode crack propagation in concrete. Two tests are selected so that the propagation is almost always stable although the material is quasi-fragile. Moreover the variation of mode mixity enables the study of the reorientation of the crack, as well as more complex phenomena such as branching or link-up. To control stability and mode mixity, the loading is imposed with a 6-axis testing machine while the crack propagation is assessed by full-field measurement. In this paper, a description of the experimental setup is provided as well as numerical simulation results illustrating the sensitivity to boundary conditions and geometry. Links to data needed to perform numerical simulations of these benchmark experiments are given, together with references to publications giving full descriptions of the protocol and experiment results.

A comparative study on stress intensity factor-based criteria for the prediction of mixed mode I-II crack propagation in concrete

Combined with the fictitious crack model, the stress intensity factor (SIF)-based criteria are widely adopted to determine the crack propagation of mixed mode I-II fracture in normal strength concrete. However, less research is reported on the applicability of the different SIF-based criteria when they are used to analyze the crack propagation process of concrete with different strength grades. With this objective in mind, three-point bending and four-point shear tests were conducted in this study on C20, C50 and C80 grade concrete to measure the initial fracture toughness, fracture energy, load-crack mouth opening/sliding displacement (CMOD/CMSD). Four SIF-based criteria, including two initial fracture toughness-based (with/without mode II component of SIF KII) and two nil SIF-based (with/without KII), were introduced to determine crack propagation and predict the P-CMOD/CMSD curves for the notched concrete beams under four-point shear loading. The results indicated that the difference between the peak loads from experiment and from the analysis based on the nil SIF criterion with KII approximately increases with the increase of the concrete strength. By contrast, the predicted peak load and P-CMOD/CMSD curves adopting the initial fracture toughness-based criterion with KII showed better agreement with experimental results for the different concrete strength. Meanwhile, in the case of the initial fracture toughness-based criteria, the predicted initial load was underestimated if the component of KII was not considered. However, the fracture mode transformed from mixed mode I-II to mode I after the crack initiation, meaning the KII component in the criterion had a less significant effect on the crack propagation process.

An Introduction of Boundary Element Method.to the Analysis of Crack Propagation in Concrete

The dual boundary element method (DBEM) incorporated with fictitious crack model (FCM) is used to analyse and simulatethe crack propagation .in concrete. The fracture in concrete is represented by the FCM in which the fracture zone is replaced by applying closing forces on both crack surfaces. When the force at the ficti tious crack tip exceeds the maximum tensile strength of the concrete, the fictitious crack will propagate perpendicular to the maximum principal stress. Three-point bending specimen is used to check the numerical analysis and the res ults is compared to the analysis by finite element method and experimental results.

Effect of engineered cementitious composite on the bond behavior between fiber-reinforced polymer and concrete

Externally bonded fiber-reinforced polymer (FRP) to a degraded reinforced concrete structure is currently a very popular strengthening technology; however, premature debonding mainly caused by concrete crack propagation leads to the underutilization of FRP. Engineered cementitious composite (ECC) has an excellent crack control capability. When used in combination with FRP, ECC can effectively delay the debonding of FRP and enhance the bearing capacity and ductility of FRP-strengthened structures. For the safe and economic strengthening design, the bond-slip relationship of FRP-ECC-concrete needs to be properly understood. This paper investigated the bond behavior of FRP–ECC–concrete interface through a series of simple shear tests. The effects of ECC thickness, concrete surface treatment, and construction method on the bond behavior were evaluated. The deformation and strain data of FRP were collected and analyzed using a noncontact full-field strain measurement system VIC-3D (three-dimensional video image correlation system). The experimental results show that the addition of an ECC layer delayed the debonding of FRP and significantly increased the maximum strain of FRP. The bearing capacity, the ultimate slip, and the interface energy consumption capacity also improved significantly.

Cracking propagation of hardening concrete based on the extended finite element method

Self-deformation cracking is the cracking caused by thermal deformation, autogenous volume deformation or shrinkage deformation. In this paper, an extended finite element calculation method was deduced for concrete crack propagation under a constant hydration and hardening condition during the construction period, and a corresponding programming code was developed. The experimental investigation shows that initial crack propagation caused by self-deformation loads can be analyzed by this program. This improved algorithm was a preliminary application of the XFEM to the problem of the concrete self-deformation cracking during the hydration and hardening period. However, room for improvement exists for this algorithm in terms of matching calculation programs with mass concrete temperature fields containing cooling pipes and the influence of creep or damage on crack propagation.

Experimental study on water fracture interactions in concrete

A novel sealing device that has a minimal effect on the mechanical behaviour of concrete specimens is proposed in this paper. This device connects one side of silicon plates to a specimen using two specially designed clamps, instead of adhesive and screws the other side of the plates together to a steel plate. Several experimental wedge-splitting tests under compact tension are conducted with and without this sealing device to investigate the effect of water pressure on concrete crack propagation. The fracture experiments for concrete under different water pressures and different loading rates are carried out by wedge-splitting tests with the water pressure applied using this novel device. The water distribution is obtained based on experimental data recorded by five pressure transducers present at the tip of a notched crack, and the results show that the internal water pressure consists of a constant curve and a parabolic curve. The water within the crack has sufficient time to enter the crack when the specimen is subjected to a slow split loading, and the water front during slow loading test exceeds that of the fast loadings when reaching the same CMOD. The effect of the water interactions in concrete is severe in quasi-static conditions rather than in fast loading conditions during crack sudden opening. The loading rate plays a dominant role in the water pressure distribution and crack propagation.

Bearing mechanism of composite structure with reinforced concrete and steel liner: An application in penstock

For the composite structure comprised of steel-lined concrete, the inside steel liner and surrounding reinforced concrete are designed to work reliably. The potential sliding between the reinforced concrete and steel liner has a significant effect on the structure bearing mechanism. The Coulomb friction model is employed to simulate the sliding of the steel liner against the surrounding concrete. A concrete damage plasticity (CDP) model is proposed to simulate the surrounding reinforced concrete. The finite element (FE) models of the steel-lined reinforced concrete penstock (SLRCP) located on the downstream surface of a double curvature arch concrete dam are developed, in which the nodes-shared method (NSM) and the friction-contact method (FCM), respectively, are employed. The concrete crack initiation time, concrete crack propagation pattern, penstock deformation, tensile stresses of the steel liner and the reinforcements are presented. The results of the FCM model agree well with the monitoring data, validating that the proposed model could be directly employed in the FE software ABAQUS.

General cracked-hinge model for simulation of low-cycle damage in cemented beams on soil

The need for mechanistic constitutive models to evaluate the complex interaction between concrete crack propagation, geometry and soil foundation in concrete- and composite pavement systems has been recognized. Several models developed are either too complex or designed to solve relatively simple problems, e.g. limited to one type of load configuration or test set-up. In order to develop a general and mechanistic modeling framework for non-linear analysis of low-cycle damage in cemented materials, this paper presents a cracked-hinge model aimed at the analysis of the bending fracture of the cemented material. The model is based on the fracture mechanics concepts of the fictitious crack model. The proposed hinge is described in a general and consistent format, allowing for any type of stress-crack opening relationship and unloading- reloading formulation. The functionality of the proposed hinge model is compared to numerical- and experimental results. The proposed hinge shows good performance and seems promising for the description of low-cycle fracture behavior in cemented materials.

Mesoscopic analysis of Crack Propagation in Concrete by Nonlinear Finite Element Method with Crack Queuing Algorithm

By means of nonlinear finite element method, the initiation and propagation of cracks in concrete are analysed numerically at the mesoscopic level. The concrete is treated and modelled as a three-phase system consisting of coarse aggregate, hardened mortar matrix and interfacial transition zones between coarse aggregate and mortar matrix. Nonlinear constitutive properties of the materials before and after cracking are incorporated in the modelling. An integrated cracking criterion based on both tensile strength and fracture toughness is proposed to cater for stress concentration at crack tips, and a crack queuing algorithm is employed to simulate the stress redistribution and stress relief upon cracking. To illustrate the applications of the proposed method, an example of the cracking process of concrete is presented.

Concrete Cracking Prediction Including the Filling Proportion of Strand Corrosion Products.

The filling of strand corrosion products during concrete crack propagation is investigated experimentally in the present paper. The effects of stirrups on the filling of corrosion products and concrete cracking are clarified. A prediction model of crack width is developed incorporating the filling proportion of corrosion products and the twisting shape of the strand. Experimental data on cracking angle, crack width, and corrosion loss obtained from accelerated corrosion tests of concrete beams are presented. The proposed model is verified by experimental data. Results show that the filling extent of corrosion products varies with crack propagation. The rust filling extent increases with the propagating crack until a critical width. Beyond the critical width, the rust-filling extent remains stable. Using stirrups can decrease the critical crack width. Stirrups can restrict crack propagation and reduce the rust filling. The tangent of the cracking angle increases with increasing corrosion loss. The prediction of corrosion-induced crack is sensitive to the rust-filling extent.

Modeling of Corrosion-Induced Damage in Reinforced Concrete Considering Electro-Mechanical Coupling

This paper presents an electro-mechanical model for evaluating the corrosion-induced damage in reinforced concrete under accelerated conditions. The model consists of structural analysis of concrete and the rebar using the Rigid Body Spring Method and corrosion current analysis with the truss networks model. The electric corrosion process is coupled with concrete cracking conditions by relating current efficiency to local crack width; the predicted radius losses of rebars are used to evaluate concrete crack propagation and residual tensile performance of corroded rebars. The model is validated with the results of accelerated corrosion tests using impressed current and a sodium chloride pond on the concrete cover. Good agreement with the test data is obtained with the proposed model, in terms of corrosion degree and profile, concrete crack pattern, and tensile behavior of corroded rebars. The model offers a corroborative tool with the accelerated corrosion technique to study the mechanical behavior of corroded concrete structures.

Crack propagation modelling in concrete using the scaled boundary finite element method with hybrid polygon–quadtree meshes

This manuscript presents an extension of the recently-developed hybrid polygon–quadtree-based scaled boundary finite element method to model crack propagation in concrete. This hybrid approach combines the use of quadtree cells with arbitrary sided polygons for domain discretization. The scaled boundary finite element formulation does not distinguish between quadtree cells and arbitrary sided polygons in the mesh. A single formulation is applicable to all types of cells and polygons in the mesh. This eliminates the need to develop transitional elements to bridge the cells belonging to different levels in the quadtree hierarchy. Further to this, the use of arbitrary sided polygons facilitate the accurate discretization of curved boundaries that may result during crack propagation. The fracture process zone that is characteristic in concrete fracture is modelled using zero-thickness interface elements that are coupled to the scaled boundary finite element method using a shadow domain procedure. The scaled boundary finite element method can accurately model the asymptotic stress field in the vicinity of the crack tip with cohesive tractions. This leads to the accurate computation of the stress intensity factors, which is used to determine the condition for crack propagation and the resulting direction. Crack growth can be efficiently resolved using an efficient remeshing algorithm that employs a combination of quadtree decomposition functions and simple Booleans operations. The flexibility of the scaled boundary finite element method to be formulated on arbitrary sided polygons also result in a flexible remeshing algorithm for modelling crack propagation. The developed method is validated using three laboratory experiments of notched concrete beams subjected to different loading conditions.

A comparative study on two stress intensity factor-based criteria for prediction of mode-I crack propagation in concrete

In the analysis of mode-I crack propagation of normal strength concrete at a crack tip, the initial fracture toughness and nil-stress intensity factor (nil-SIF) are two distinguished and widely adopted types of crack propagation criteria. However, there is little information reported on the difference resulting from the two criteria when they are employed to analyze concrete with different strength grades. Aiming at this objective, three-point bending tests are carried out on notched concrete beams of five strength grades, i.e. C20, C40, C60, C80 and C100, and an arrange of initial crack length/depth ratios as 0.2, 0.3 and 0.4, to investigate initial fracture toughness, fracture energy and load–crack mouth opening displacement (P–CMOD) relationship. Meanwhile, the three-point bending tests are also conducted on notched concrete beams of four specimen heights, i.e. 60, 90, 120, and 150mm. The two aforementioned types of concrete crack propagation criteria are introduced to determine crack propagation and predict the P–CMOD curves of a series of notched concrete beams under a three-point bending test. It has been found that the P–CMOD curves calculated using the initial fracture toughness criterion show a better agreement with experimental results than the ones calculated using the nil SIF criterion. With the increase of concrete strength, the difference between the peak loads from experiment and those from analyses based on the nil-SIF criterion becomes increasingly larger than the scenarios based on the initial fracture toughness criterion. Therefore, it can be reasonably concluded that for the two types of concrete crack propagation criteria, the initial fracture toughness is more appropriate for describing the fracture behavior of concrete, especially for high strength concrete.

Crack healing in concrete using various bio influenced self-healing techniques

Crack formation and progression under tensile stress is a major weakness of concrete. These cracks also make concrete vulnerable to deleterious environment due to ingress of harmful compounds. Crack healing in concrete can be helpful in mitigation of development and propagation of cracks in concrete. This paper presents the process of crack healing phenomenon in concrete by microbial activity of bacteria, Bacillus subtilis. Bacteria were introduced in concrete by direct incorporation, and thorough various carrier compounds namely light weight aggregate and graphite nano platelets. In all the techniques, calcium lactate was used as an organic precursor. Specimens were made for each mix to quantify crack healing and to compare changes in compressive strength of concrete. Results showed that bacteria immobilized in graphite nano platelets gave better results in specimens pre-cracked at 3 and 7days while bacteria immobilized in light weight aggregates were more effective in samples pre-cracked at 14 and 28days. In addition, concrete incorporated with bacteria immobilized in light weight aggregate, also exhibited significant enhancement in compressive strength of concrete.

Fracture Analysis of FRP-Plated Notched Concrete Beams Subjected to Three-Point Bending

AbstractThree-point bending tests of fiber-reinforced polymer (FRP) plated notched concrete beams have great potential to become a standard test method for evaluating the shear bond performance of FRP-to-concrete interfaces. This paper presents an analytical approach to predict the full-range response of FRP-plated notched concrete beams. The focus of the analysis is to simulate the interactions between Mode II debonding of the FRP-to-concrete interface and Mode I fracture at the crack tip of the concrete beam. In analyzing the FRP-to-concrete interface, the slip is selected as the unknown function to derive a second-order ordinary differential equation, and the analytical relationship between the pull force of the FRP laminate and the interfacial slip at its loaded end is formulated. Crack propagation in concrete is modeled using the weight function method. The stress intensity factors induced by various external loads and internal forces are all given in an analytical manner. Finally, a global equation ...

A combined XFEM–damage mechanics approach for concrete crack propagation

This paper presents a crack model that couples the benefits of the damage mechanics approach and the extended finite element method (XFEM). A crack-tracking technique is developed to propagate the crack path along a single row of finite elements as a function of the stress-based nonlocal method. The level sets are computed to predict the crack path, and the path is corrected with the use of continuum damage mechanics. Once a certain level of damage is reached inside an element, the previously-computed level sets are used to apply the XFEM formulation. A cohesive XFEM formulation is used to transfer energy dissipation from the damage mechanics approach to the XFEM model. Using numerous test cases, it is shown that the model is mesh independent and that it removes the spurious stress transfer exhibited by continuum damage models. Various transition damage criteria are compared, and the optimal one is determined.

Discussion of “Calculating crack extension resistance of concrete based on a new crack propagation criterion” by Wei Dong, Zhimin Wu, Xiangming Zhou

Based on the original paper, a revised Young’s modulus E and a more accurate calculation of initial fracture toughness are proposed in present discussion.The main contribution of the discussed paper is to develop a numerical method to simulate the whole crack propagation in concrete by considering the variation of FPZ length. Notched concrete beams were tested under three-point bending with P-CMOD curves obtained which were then compared with the numerical ones to validate the proposed numerical method. After that, the proposed method was employed to obtain KR-curve for the complete fracture process, taking into consideration the cohesive stress acting on FPZ. Finally, the effect of variation of FPZ length and fracture energy on KR-curve, as well as size effect on KR-curve, was discussed. The discusser appreciates the authors’ meaningful work. However some findings are interesting to the discusser and are worthy of further discussion.

Evaluation of concrete fracture procedure based on acoustic emission parameters

Acoustic emission (AE) acquiring technique was employed to explore the concrete fracture procedure in this study. Several parameters were evaluated through three-point bending beam tests using concrete fracture experiments. Acoustic emission instrument and strain gauges were used to monitor the initial and final fracture loads during crack propagation stage of specimens. In addition, the parameter values associated to crack propagations were obtained from the well-developed formula and test results. The typical trend curves and failure forms of each group of specimens were accompanied based on the crack-propagation theory. The designated concrete tests used in this study conducted a general process of crack fracture propagation. The experimental results indicated that AE detection system could well reflect the internal defects and cracks of the specimen. Additionally, the results illustrated that AE technology could reflect the initial fracture moment and final structure failure at a relatively low loading rate, and consequently could acquire the initial and failure fracture loadings. Based on this limited study, it can be found that, in most cases, concrete AE parameter characteristic could reflect the concrete crack propagation and its complete structure failure during the loading procedure. Additionally, it was found that the test results from AE method were similar to those from strain gauge method.

Numerical Method for Mixed-Mode I–II Crack Propagation in Concrete

A crack-propagation criterion is proposed in this paper for mixed-mode I–II fracture in concrete. In this criterion, crack propagation is initiated when the difference between the stress-intensity factor at the crack tip caused by the external force and that by the cohesive stress satisfies the crack-initiation equation. On the basis of this criterion, a numerical method is developed to simulate mixed-mode I–II crack propagation in concrete. To verify the criterion, three sets of experimental data are selected: one is obtained from the self-conducted test and the other two are collected from the literature. The numerical results show that the calculated load versus crack-mouth opening and sliding displacement curves and crack trajectories are in good agreement with experimental results. Therefore, once the mode I initial cracking toughness, elastic modulus, fracture energy, possion’s ratio, and tensile strength of concrete are available, the whole mixed-mode I–II fracture process in concrete can be predicted with reasonable accuracy.

Implementation of Fictitious Crack Model Using Contact Finite Element Method for the Crack Propagation in Concrete under Cyclic Load

The mixed freedom finite element method proposed for contact problems was extended to simulate the fracture mechanics of concrete using the fictitious crack model. Pairs of contact points were set along the potential developing path of the crack. The displacement of structure was chosen as the basic variable, and the nodal contact force in contact region under local coordinate system was selected as the iteration variable to confine the nonlinear iteration process in the potential contact surface which is more numerically efficient. The contact forces and the opening of the crack were obtained explicitly enabling the softening constitutive relation for the concrete to be introduced conveniently by the fictitious crack model. According to the states of the load and the crack, the constitutive relation of concrete under cyclic load is characterized by six contact states with each contact state denoting its own displacement-stress relation. In this paper, the basic idea of the mixed freedom finite element method as well as the constitutive relation of concrete under cyclic load is presented. A numerical method was proposed to simulate crack propagation process in concrete. The accuracy and capability of the proposed method were verified by a numerical example against experiment data.