Concrete Cracking Model Research Articles

Uncertainty of the crack width model based on fracture of concrete

AbstractA reliable crack width assessment is a basic part of the sustainability control of the reinforced concrete structures subjected to corrosion degradation. The uncertainty of the concrete cracking model based on a finite element method and nonlinear fracture mechanics is investigated. The parameters of numerical model, such as the finite element mesh size and amount and arrangement of reinforcement are the subject of a case study. The uncertainty of the crack width model is verified on the experimental data from the tests of reinforced concrete beams. The constitutive model of crack propagation is based on the smeared cracks. The effects of numerical discretization as well as dimensional simplification are shown.

Phase field modeling of concrete cracking for non-uniform corrosion of rebar

Non-uniform corrosion of rebar in reinforced concrete will lead to concrete cover cracking, thus significantly reducing the durability of structures. A 2D mesoscale phase field model was developed to explore the failure behaviors of corrosion-induced cracking. The expansion of rust was described by a time-dependent non-uniform corrosion model. The phase field regularized cohesive zone model was employed to study the cracking pattern. The proposed model was validated by available experimental results in publications. The effects of several geometric parameters, such as concrete cover thickness, rebar diameter, and clear spacing, on the crack pattern and crack width of single and multiple rebar models were investigated. Finally, the influence of the ratio of cover thickness to rebar diameter on the failure pressure was discussed.

Meso-scale modeling of concrete cracking induced by 3D corrosion expansion of helical strands

A meso-scale numerical model is established to simulate concrete cracking induced by the three-dimensional (3D) corrosion expansion of helical strands in the present study. A 3D corrosion expansion model is proposed to consider the longitudinal helix shape and transverse flower-like shape of the strand. The concrete in the model is considered as a three-phase composite material consisting of a mortar matrix, aggregate, and interfacial transition zones (ITZ) between the mortar matrix and aggregate. The rationality of the proposed model is validated, and the effects of the space helix structure and the lay length of the strand on corrosion-induced cracking are discussed. The results indicate that considering the space helix structure of a strand can effectively improve the prediction accuracy of strand corrosion-induced concrete cracking. The change in strand lay length has little effect on the critical corrosion loss of the initial damage occurrence. The critical corrosion loss at cover cracking increases with increasing strand lay length, whereas the corrosion-induced crack width decreases with increasing strand lay length.

Modeling of Cover Concrete Cracking Due to Uniform Corrosion of Reinforcement

Cracking of cover concrete due to the corrosion of reinforcing steel is one of the main causes of deterioration in Reinforced Concrete (RC) structures. An outbound stress is developed in concrete surrounding the reinforcing steels due to the expansive corrosion products of reinforcement leading to cracking of the concrete cover. In this paper, the cracking pressure was simulated through a finite element modeling. The effect of geometrical and material parameters, i.e. concrete cover thickness, bar diameter, and concrete tensile strength, on the cracking pressure was also investigated. Abaqus 6.14 was used as modeling platform. The cracking pressure was found to dependent on the cover thickness and tensile strength of concrete. A higher pressure was required to initiate crack for a higher cover thicknesses and tensile strength. The cracking pressure was decreased with the increase in bar diameter. Finally the crack initiation and propagation has been simulated successfully for different arrangements of reinforcements.
 Journal of Engineering Science 12(1), 2021, 43-49

Effect of correlated random fields on nonlinear dynamic responses of gravity dam

Uncertainty will inevitably be introduced into the structural analysis, while randomness is an important manifestation of uncertainty. Based on the random field theory, the correlated random fields of the Koyna gravity dam were realized, and the influence of the randomness of material parameters on the nonlinear responses of the gravity dam was investigated. A concrete continuum crack model was employed to describe the nonlinear mechanical behavior of gravity dams under static and dynamic loads. To avoid the contingency caused by the initial random samples, the comparisons of the nonlinear dynamic responses of the dam are based on the statistical analysis of a large number of random fields. The parameter sensitivity analysis is first implemented, and then, the nonlinear responses of the proposed correlated random field model and the conventional random variable-based model are comprehensively compared. The analysis showed that the randomness and spatial correlation of materials would affect the seismic performance of gravity dams, which should be considered in structural design and seismic risk analysis.

Strongly coupled XFEM formulation for non-planar three-dimensional simulation of hydraulic fracturing with emphasis on concrete dams

This paper presents a novel and robust three-dimensional plain concrete cracking model applicable to the study of structural stability of large structures, such as dams, while considering the presence of pressurized water in propagating cracks. When leaving the elastic range, there is a transition from a continuum approach to a XFEM approach. This mechanical model is coupled with a poro-damage model where the permeability is increased as micro-cracks coalesce into macro-cracks. The crack opening computation during continuum damage is based on a local XFEM formulation without the need for a reference length in a strongly coupled hydro-mechanical formulation to update the uplift pressures. The 3D crack path computation is adapted from an analogy to the heat conduction problem to draw the envelope of the discontinuities’ tangent vector field. Six benchmark problems available from the literature, including a 96m-high arch dam, are considered and indicate the very good performance of the proposed model as well as its applicability to real industrial structures.

Analytical and Experimental Investigation on Corrosion-Induced Concrete Cracking

Practical experience and observation suggest that corrosion-affected reinforced concrete structures are highly susceptible to cracking. This paper presents an analytical time to corrosion-induced concrete cracking model based on fracture mechanics. The concrete cover load-bearing capacity is proposed and is used as a fracture criterion for concrete cracking. An accelerated corrosion test has been undertaken to produce data on time to corrosion-induced concrete cracking and crack width over time. A comparison between the analytical model and experimental results on time to concrete cracking and on crack width over time shows reasonable agreement. It is found that the distribution and size of the porous zone are non-uniform which is one of the main causes for discrepancy between results. The larger the porous zone is the longer it takes for concrete cover to crack due to corrosion. Although the experimental and model results exhibit similar trend, it is also found that assuming only a single propagating crack in analytical model results in an overestimation of corrosion-induced crack width. The models presented in this paper can serve as useful tool for serviceability and durability assessment of corrosion-affected reinforced concrete structures.

Structural analysis of transverse cracks in short continuously reinforced concrete pavements

ABSTRACT Continuously reinforced concrete pavement (CRCP) is a widely used alternative for heavy traffic highways due to good performance and low maintenance needs. Recently, the use of short length CRCP (50-m long slabs) has been proposed for bus stops and terminals. This paper examines the structural behaviour of cracks in short CRCP. This includes analysis of the Falling Weight Deflectometer (FWD) deflections and strain gauge measurements obtained from the full-scale test sections as well as structural modelling of the pavement. An evaluation of the influence of cracks on the FWD deflection basins collected on the experimental short CRCP pavement along with FWD data collected under the Long-Term Pavement Performance programme for conventional CRCP resulted in similar behaviour between the short and conventional CRCP. Therefore, the effects of the short CRCP transverse cracks on stresses were investigated. Three ISLAB2000 models differed by the concrete base or crack model were developed and their stress predictions were compared with field stresses. An applicability of the conventional aggregate interlock model for describing the behaviour of short CRCP was evaluated as only the continuous slab (no cracks) model was able to match the field stresses. A need for re-appraisal of the PavementME structural model is also discussed.

Numerical determination of concrete crack width for corrosion-affected concrete structures

Corrosion-induced deterioration of reinforced concrete (RC) structures results in premature failure of the RC structures. In practice concrete crack width is one of the most important criteria for the assessment of the serviceability of RC structures. It is therefore desirable to predict the growth of the crack width over time so that better informed decisions can be made concerning the repairs due to concrete cracking. Literature review shows that little research has been undertaken on numerical prediction of concrete crack width. The intention of this study was to develop a numerical method to predict concrete crack width for corrosion-affected concrete structures. A cohesive crack model for concrete is implemented in the numerical formulation to simulate crack initiation and propagation in concrete. Choices for evaluating the parameters of cohesive elements are extensively discussed which is a key for developing a plausible model employing cohesive elements. The surface crack width is obtained as a function of service time. Accurate prediction of crack width can allow timely maintenance which prolongs the service life of the reinforced concrete structures.

CRACKING PROCESS OF REINFORCED CONCRETE INDUCED BY NON-UNIFORM REINFORCEMENT CORROSION

Expansion of rust, as a result of reinforcement corrosion, can cause additional internal expansive pressure and initiate cracking to the concrete. This paper presents experimental test and numerical modeling of concrete cracking induced by reinforcement corrosion. The simulation was performed using finite element based program Abaqus CAE using concrete smeared cracking approach. The numerical modeling used non-uniform and uniform corrosion assumption to get more accurate result. Based on the result, the numerical modeling has 3.01% lower stress than the experimental test. The result of the simulation using non-uniform assumption showed more similar cracking pattern with the experimental test compared with uniform assumption.

Direct finite element method for nonlinear analysis of semi‐unbounded dam–water–foundation rock systems

SummaryA direct finite element method is presented for nonlinear earthquake analysis of interacting dam–water–foundation rock systems. The analysis procedure applies viscous damper absorbing boundaries to truncate the semi‐unbounded fluid and foundation‐rock domains and specifies at these boundaries effective earthquake forces determined from the design ground motion defined at a control point on the free surface. The analysis procedure is validated numerically by computing the frequency response functions and transient response of an idealized dam–water–foundation rock system and comparing with results from the substructure method. Because the analysis procedure is applicable to nonlinear systems, it allows for modeling of concrete cracking, as well as sliding and separation at construction joints, lift joints, and at concrete–rock interfaces. Implementation of the procedure is facilitated by commercial finite element software with nonlinear material models that permit modeling of viscous damper boundaries and specification of effective earthquake forces at these boundaries. Copyright © 2017 John Wiley & Sons, Ltd.

Load Spectra–Incorporated Fatigue Cracking Model Implementation and Case Study

Traffic loading is one of the key factors that may cause asphalt concrete pavement fatigue cracking. Axle load spectra input provides an opportunity for evaluating the pavement response under real traffic loads throughout the pavement design life. This paper describes the methodology of incorporating axle load spectra into the mechanistic–empirical fatigue cracking model that uses a fracture mechanics method to determine crack propagation. The paper also presents the incorporation of the method into the Texas mechanistic–empirical flexible pavement design system. Several load spectra cases were studied, and the percentages of the corresponding fatigue cracking areas were predicted and compared. The comparison results confirmed the necessity of load spectra analysis. Overall, the implemented load spectra–incorporated asphalt concrete fatigue cracking model generated rational results. Further research is continuing on field validation and calibration.

Strategies for numerical modeling the behavior of RC beams strengthened in shear using the ETS technique

The strategy to simulate the crack shear stress transfer in a fixed smeared crack model for concrete is crucial to correctly predict the deformational and cracking behavior of RC elements that exhibit shear failure. This work presents a shear softening law able to correctly simulate the shear stiffness degradation and stress transfer during the crack opening. In cracked concrete, the element of the matrix corresponding to the fracture mode II is represented here by a τtcr-γtcr diagram, describing the shear behavior of the ith crack. The predictive performance is evaluated simulating RC beams failing in shear strengthened using the Embedded Through-Section Technique. According to this technique holes are opened through the cross section, with the desired inclination, and steel or FRP bars are introduced into these holes and bonded to the concrete substrate with adhesive materials. The parameters influencing the shear softening law are analyzed through a parametric study, furthermore a simple rule to estimate these parameters is provided and its predictive performance is assessed. The presented approach represents a valid alternative to the shear retention function.

Corrosion-induced concrete cracking model considering corrosion product-filled paste at the concrete/steel interface

When steel corrosion happens in concrete, the corrosion products migrate to the pores at the steel/concrete interface. The relationship between the thickness of the corrosion product-filled paste (CP) and that of the corrosion layer (CL) was analysed and established. This relationship can describe the phenomenon that the corrosion products are filling in the concrete pores and accumulating at the steel/concrete interface simultaneously. Based on this relationship, a corrosion-induced concrete surface cracking model which can quantitatively consider corrosion product-filled paste at the concrete/steel interface is proposed. This model is verified and in reasonable agreement with the experimental results. The possibility of the application of the proposed corrosion-induced cracking model to the non-uniform corrosion case is also discussed.

Multi-scale modeling for deformation mechanism analysis of composite joint substructures

Analyzing the deformation mechanism of composite joint substructures in a concrete filled steel tubular (CFST) column-composite floor frame structural system is essential to assessing its overall seismic performance and failure mode. Conventional microscopic and discrete finite element models have several problems hindering application for the deformation mechanism analysis. To address these problems, the present study develops a multi-scale modeling approach of the composite joint substructure. Two critical issues in the multi-scale modeling is first discussed: (i) modeling the slab spatial composite effect under bidirectional earthquake loading using efficient fiber beam–column elements and (ii) key parameters of the concrete crack model for simulating the spatial shear behavior of the composite joint core. The proposed multi-scale model is validated by several tested plane and spatial composite joint substructures. Finally, the deformation-component-proportion (DCP) diagram, which can be calculated directly from the displacement results of the proposed multi-scale model, is introduced to analyze the deformation mechanism of the composite joint substructure. The proportions of the beam flexural, column flexural and joint core shear deformations in the total deformation corresponding to different story drift angles and different story drift direction angles can be illustrated by the DCP diagram so that the failure mode of the composite joint substructure can be clearly revealed in any possible earthquake incident direction. The proposed multi-scale modeling approach offers a powerful tool for assessing the deformation mechanism of composite joint substructures.

Modeling of concrete cracking due to corrosion process of reinforcement bars

The reinforcement corrosion in Reinforced Concrete (RC) is a major reason of degradation for structures and infrastructures throughout the world leading to their premature deterioration before design life was attained. The effects of corrosion of reinforcement are: (i) the reduction of the cross section of the bars, and (ii) the development of corrosion products leading to the appearance of cracks in the concrete cover and subsequent cover spalling. Due to their intrinsic complex nature, these issues require an interdisciplinary approach involving both material science and structural design knowledge also in terms on International and National codes that implemented the concept of durability and service life of structures.In this paper preliminary FEM analyses were performed in order to simulate pitting corrosion or general corrosion aimed to demonstrate the possibility to extend the results obtained for a cylindrical specimen, reinforced by a single bar, to more complex RC members in terms of geometry and reinforcement. Furthermore, a mechanical analytical model to evaluate the stresses in the concrete surrounding the reinforcement bars is proposed. In addition, a sophisticated model is presented to evaluate the non-linear development of stresses inside concrete and crack propagation when reinforcement bars start to corrode. The relationships between the cracking development (mechanical) and the reduction of the steel section (electrochemical) are provided. Finally, numerical findings reported in this paper were compared to experimental results available in the literature and satisfactory agreement was found.

Three-Dimensional Numerical Analysis of Compound Lining in Complex Underground Surge-Shaft Structure

The mechanical behavior of lining structure of deep-embedded cylinder surge shaft with multifork tunnel is analyzed using three-dimensional nonlinear FEM. With the elastic-plastic constitutive relations of rock mass imported and the implicit bolt element and distributed concrete cracking model adopted, a computing method of complex surge shaft is presented for the simulation of underground excavations and concrete lining cracks. In order to reflect the interaction and initial gap between rock mass and concrete lining, a three-dimensional nonlinear interface element is adopted, which can take into account both the normal and tangential characteristics. By an actual engineering computation, the distortion characteristics and stress distribution rules of the dimensional multifork surge-shaft lining structure under different behavior are revealed. The results verify the rationality and feasibility of this computation model and method and provide a new idea and reference for the complex surge-shaft design and construction.

Finite Element Analysis of Dynamic Responses of Plain Concrete Pavements Under Strong Impact Loading

Plain concrete pavements under heavy impact loading will induce flexure, crack and direct shear failure. To obtain dynamic response and failure mode of plain concrete pavement under heavy impact loading, the concrete brittle crack model is adopted and finite element model of plain concrete pavements is established; the dynamic response and failure mode under heavy impact loading in different loading points and different loading times are studied; the production, stretching and extension of cracking are researched; which is a powerful reference for practical engineering application.

Damage Mechanism and Numerical Analysis of SRAP to Reinforce Hollow Slab Beam Interface

To study the interface layer pasting mechanism of SRAP reinforcement technology, a multi-scale numerical model, which can simultaneously simulate the local microscopic damage and global macroscopic behavior of structure, is established according to the interface connection method among the models different scales. Based on the actual bridge reinforcement project, the nonlinear overall process of reinforced bridge is analyzed using the multi-scale model, and then the interface layer of reinforced bridge is simulated after the interface units of the bond damage function are determined. Results show that the calculation results by the multi-scale numerical model in the load deflection curve, bond interface layer slip of damage, and beam body concrete cracking model of actual reinforced bridge are consistent with the actual situation. With the multi-scale model, the actual stress of microscopic model is more accurately simulated, but also the overall performance of macro model can be more accurately controlled.

Lateral and radial corrosion propagation behavior of 9–21% Cr and 18% Cr + 2.8% Mo stainless steel reinforcing materials in simulated concrete environments

AbstractThe life of a concrete structure exposed to deicing compounds or seawater is often been limited by chloride induced corrosion of the steel reinforcement. A complete assessment of the potential benefits afforded by new candidate rebar alloys must address both the lateral and radial corrosion propagation behavior in comparison to conventional steel as well as other factors that might affect the risk of corrosion‐induced concrete cracking. The radial (depth) and lateral (length) corrosion propagation behavior of 18% Cr + 2.8% Mo (S31653) stainless steel, 21% Cr (S32101) duplex stainless steel, and 9% Cr steel compared to plain ASTM A615 carbon steel were characterized in saturated Ca(OH)2 solution. Radial pit growth was found to be Ohmically controlled for all materials but repassivation occurred more readily at high applied potentials for 18% Cr + 2.8% Mo and 21% Cr stainless steels. Conversely, pit growth on plain steel propagated at all applied anodic potentials and did not repassivate until deactivation by cathodic polarization. Stainless steel also showed the highest resistance to lateral corrosion propagation from an active site during microelectrode array testing. 21% Cr duplex stainless and 9% Cr steel showed similar radial propagation behavior and corrosion morphology, which was intermediate to that of plain steel and S31653 stainless steel. Based on an existing concrete cracking model, it is expected that 9–21% Cr and 18% Cr + 2.8% Mo corrosion resistant rebar materials would require a greater depth of corrosion attack than carbon steel before damaging concrete via corrosion product formation.