Crack Width Prediction Research Articles

Flexural cracking behavior of normal strength, high strength and high strength fiber concrete beams, using Digital Image Correlation technique

The paper presents the results of an experimental work on the flexural behavior of three types of concrete: normal strength concrete (NSC), high strength concrete (HSC) and high strength fiber concrete (HSFC) in terms of crack detection, crack development, crack width measurements and strain components, using the Digital Image Correlation (DIC) technique. The experimental results of the present work and from others published in the literature were used to assess the accuracy of the major codes provisions (Eurocode 2, ACI 318 and the BS8110 code) for the crack width predictions.The comparison between the classical measurement techniques and the DIC technique suggests that both of them are suitable for the analysis of the strain components (deformations) of structural members. The most important additional benefit of the DIC technique is that it allows the easy detection of the first crack with a high precision, measures the crack opening and follows the progressive cracking process until failure of reinforced concrete members. Furthermore, the experimental results show that the addition of steel fibers increases the load at first crack and amplifies the number of cracks which leads to a remarkable decrease in both the crack spacing and crack width as well as an improvement of the ductility. The flexural failure of the beam specimens also changes from a brittle concrete crushing at the compression zone to a ductile and smooth concrete compression failure.Moreover, the present study shows that, at service load, the code’s provision on crack width are conservative for beams containing steel fibers since predicting excessively higher values than the experimental ones; the overestimation exceeded 300% in some cases and none of the present major design codes takes into consideration the positive restraining effect of the fibers on the crack widening. The Rilem technical document appears to be the only one which takes account the positive effect of steel fibers on cracking, though still not accurate enough in predicting the crack width of fiber reinforced concrete. Based on the present experimental work and on data from the literature, a modification of the Rilem mathematical model is proposed with the aim of improving the crack width prediction of this challenging concrete material.

Crack width analysis of reinforced concrete members under flexure by finite element method and crack queuing algorithm

In reinforced concrete design, it is necessary to evaluate the crack widths so as to ensure compliance with the design codes. However, crack width analysis is not easy and so far only empirical formulas, which do not agree with each other, are available for rough estimation. Particularly, the smeared crack models, which do not allow for bond–slip of reinforcing bars, would not give any crack widths. On the other hand, the discrete crack models are difficult to apply because of the need to adaptively generate discrete crack elements to follow the crack formation. Herein, a new finite element method for discrete crack analysis, which does not require the use of discrete crack elements, is developed. The reinforcing bars are modeled by discrete bar elements and their bond–slip is allowed for using interface elements. Moreover, a crack queuing algorithm is employed to simulate the stress redistribution during cracking and a cracking criterion based on both tensile strength and fracture toughness is adopted to cater for stress concentration at crack tips for correct prediction of crack number, spacing and widths.

Prediction of Crack Width Due to Corrosion of PC Tendon in Prestressed Concrete Structures

Corrosion expansion of prestressed concrete (PC) tendon affects mainly crack width on surface of concrete. This paper simulates corrosion expansion of PC tendon in concrete. Elastic expansion model is utilized for growing of corrosive product as a result of oxidation reaction on reinforcement. In reality, corrosive product penetrate freely into concrete. In order to cover this behavior, elastic expansion is then enhanced its capability in numerical simulation. Furthermore the proposed model used an apparent expansion is adopted to predict width of corrosion crack. Laboratory test is conducted to verify numerical result. Single and multi PC tendons embedded in concrete attacked by corrosion is investigated. Finally, prediction of crack width on surface of concrete due to corrosion of multi layers of PC tendons in the real pretensioned PC girder are conducted using the proposed model. The results show that corrosion crack width of the proposed model meets the real pretensioned

Maximum Crack Width Prediction in Deck Slab Concrete Structure

Inspection of crack width prediction procedures proposed by various researchers indicates that each formula contains a different set of variables. A literature review also suggests that there is no general agreement among various researchers on the relative significance of different variables affecting the crack width, despite the large number of experimental work carried out during the past few decades. An analytical method is developed to determine the concrete stress distribution near flexural cracks in reinforced concrete one-way slabs and used to investigate the effects of various variables on the spacing and width of cracks. The formula is developed using a large number of curvature values calculated from the concrete and steel strains at various sections between adjacent cracks for a number of composite precast deck slabs. The present method of incorporating the tension stiffening effect is verified by comparing calculated fracture mechanic and those measured by other investigators. The curvature values at sections between adjacent cracks are calculated using an empirical formula. Development of this formula is based on the curvature values calculated using the concrete and steel strains at various sections between successive cracks, for a number of composite precast deck slabs. Using the curvature values evaluated by the proposed formula, short-term deflections were determined for a large number of flexural members and the results were compared with those measured by other investigators. This comparison indicated that the present method of incorporating the tension stiffening effect in fracture mechanic calculations is acceptable.

Crack Width Prediction Method for Steel and FRP Reinforcement Based on Bond Theory

Crack Width Prediction Method for Steel and FRP Reinforcement Based on Bond Theory

Automated serviceability prediction of NSM strengthened structure using a fuzzy logic expert system

This paper presents a simplified model using a fuzzy logic approach for predicting the serviceability of reinforced concrete (RC) beams strengthened with near surface mounted (NSM) reinforcement. Existing analytical models lack proper formulations for the prediction of deflection and crack width in NSM strengthened beams. These existing models are based on the externally bonded reinforcement (EBR) technique with fiber reinforced polymer (FRP) laminates, which presents certain limitations for application in predicting the behavior of NSM strengthened beams. In this study seven NSM strengthened RC beams were statically tested under four point bending load. The test variables were strengthening material (steel or CFRP) and bond length (1600, 1800 or 1900mm). For fuzzification, load and bonded length were used as input parameters and the output parameters were deflection and crack width for steel bar and CFRP bar. Experimentally NSM steel strengthened beams showed better performance in terms of crack width and stiffness, although NSM FRP strengthened beams exhibited enhanced strength increment. For all parameters, the relative error of the predicted values was found to be within the acceptable limit (5%) and the goodness of fit of the predicted values was found to be close to 1.0. Hence, the developed prediction system can be said to have performed satisfactorily.

Estimation of the crack width and deformation of FRP-reinforced concrete flexural members with and without transverse shear reinforcement

As the general acceptance of FRP reinforcing bars in the concrete construction industry continues to rise, it is increasingly imperative that the structural behavior of FRP-reinforced concrete members be predicted with good accuracy. The current crack width equation used in North American design codes for FRP-reinforced concrete members assumes a constant value of the bond coefficient which results in inconsistent accuracy of crack width predictions depending on the stress level in the reinforcement relative to the stress at which the bond coefficient was calibrated. Meanwhile, effective moment of inertia equations which have been shown to be reasonably accurate for FRP-reinforced concrete members with transverse shear reinforcement do not account for the additional deformation which may result from the vertical displacement of inclined cracks in members without shear reinforcement. Simple modifications are proposed to the current deflection and crack width equations to improve their accuracy at all reinforcement stress levels within the service range and are compared to the experimental results of four full-scale FRP-reinforced concrete slabs tested in flexure.

New Analytical Approach of Flexural Crack Width Estimation for Reinforced Concrete Beams

This paper deals with the prediction of crack width for reinforced concrete structural members under pure bending. An analytical method is proposed to estimate the flexural crack width for reinforced concrete members. The proposed method utilizes conventional crack theory. Also, to consider stress conditions in tensile zone reinforced concrete members, a bond-slip relationship developed from axial tension tests was used. An analytical equation for the estimation of maximum crack width is formulated as a function of maximum bond stress. The validity, accuracy and efficiency of the proposed method are obtained by comparing the analytical results with the experimental data, and major design codes, as well as a number of analytical solutions. The analytical results presented in this paper indicate that the proposed method can effectively estimate the flexural crack width of reinforced concrete members under bending.

TINJAUAN LEBAR RETAK PADA PELAT BETON AKIBAT BEBAN STATIS

Inspection of crack width prediction procedures proposed by various investigators indicates that each formula contains a different set of variables. A literature review also suggests that there is no general agreement among various investigators on the relative significance of different variables affecting the crack width, despite the large number of experimental work carried out during the past few decades. An analytical method is developed to determine the concrete stress distribution near flexural cracks in reinforced concrete one-way slabs and used to investigate the effects of various variables on the spacing and width of cracks. The formula is developed using a large number of curvature values calculated from the concrete and steel strains at various sections between adjacent cracks for a number of composite precast deck slabs. The present method of incorporating the tension stiffening effect is verified by comparing calculated fracture mechanic and those measured by other investigators. The curvature values at sections between adjacent cracks are calculated using an empirical formula. Development of this formula is based on the curvature values calculated using the concrete and steel strains at various sections between successive cracks, for a number of slabs. Using the curvature values evaluated by the proposed formula, short-term deflections were determined for a large number of flexural members and the results were compared with those measured by other investigators. This comparison indicated that the present method of incorporating the tension stiffening effect in fracture mechanic calculations is acceptable. Keywords: crack width; formula; fracture mechanic; deflection.

Crack width prediction of FRC beams in short and long term bending condition

The use of short fibers inside concrete matrix is an effective method for reducing the vulnerability of concrete constructions subjected to harsh environment. The action of the short fibers in reducing the crack opening is the main issue that needs a research effort in order to optimize the expected results. At the moment the analytical prediction of the crack width and spacing in fiber reinforced concrete (FRC) structural elements under bending loads is still an open problem. A crack width relationship for FRC/RC elements similar to those developed for plain concrete structural members would be desirable for designers and engineers involved in the design of FRC structural elements. The recent development of important technical design codes, such as RILEM TC 162 TDF and the new Model Code (MC) 2010, embrace this idea. However further validation of these models by experimental results is still needed. On the other hand the study of the influence of a sustained load on crack width in presence of a short fibers reinforcement is a topic almost unexplored and important at the same time. In this research the cracking behaviour of full-scale concrete beams reinforced with both traditional steel bars and short fibers has been analyzed under short and long term bending condition. A theoretical prediction of crack width and crack spacing was carried out according to international design provisions based on different analytical models. The theoretical results are discussed and compared in order to highlight the differences between the available models and to check the reliability of the theoretical predictions on the basis of the experimental data. A modified relationship to take into account of the presence of stirrups has been proposed on the basis of experimental results; furthermore, some critical aspects, such as the influence of the type of fibers and the effect of loading-time, have been underlined that should be addressed in future research work.

Prediction of the maximum crack width formed in parapets of coastal structures

Prediction of the maximum crack width formed in parapets of coastal structures

Serviceability Analysis of Reinforced Concrete Members Based on Stress Transfer Approach

In present study, the stress transfer approach for deformation and cracking analysis of tensile reinforced concrete members is investigated. Stress transfer model which is able to take into account stochastic distribution of mechanical properties of concrete was developed. As numerically obtained results are principally governed by the bond-slip function used, a sensitivity analysis is performed examining the well known bond models and their influence on prediction results of the development of cracks and overall deformation. It has been shown that modeling deformation behavior of cracked reinforced concrete, satisfactory results can be achieved for a large range of possible bond stress-slip relationships. However crack spacing and width predictions are highly sensitive to the assumed bond model.

Enhancements to Punchout Prediction Model in Mechanistic–Empirical Pavement Design Guide Procedure

The punchout prediction model for continuously reinforced concrete pavements (CRCP) from the Mechanistic–Empirical Pavement Design Guide, along with improvements to the procedure made since the software program was released in 2004 as a product of NCHRP Project 1-37A, is presented. The punchout prediction procedure is based on mechanistic principles for estimating top-down fatigue damage in the CRCP and on an empirical punchout prediction model calibrated to field data. The mechanistic structural evaluation includes models for estimating crack width, crack spacing, load transfer efficiency across transverse cracks, and fatigue damage accumulation based on Miner's hypothesis. The punchout prediction model was calibrated to data on field distress development obtained from CRCP sections nationwide. Most of the field sections were part of the long-term pavement performance (LTPP) experiment, and most of the materials, traffic, climate, and construction data were obtained from the LTPP database. Since 2004, NCHRP has made two main technical enhancements to the design software. The first addressed comments from an independent panel that performed a formal review under Project 1-40A. Second, a systematic error was discovered in the coefficient of thermal expansion test procedure for portland cement concrete, and appropriate corrections were made in the LTPP database. The punchout model was recalibrated to account for this error. The developed models show that the procedure makes reasonable crack spacing, crack width, and punchout predictions that match field observations. The models resulted in similar CRCP thickness designs before and after the coefficient of thermal expansion corrections were made, if the corresponding model calibration coefficients were used.

Flexural Behavior and Serviceability of Normal- and High-Strength Concrete Beams Reinforced with Glass Fiber-Reinforced Polymer Bars

This paper investigated the flexural behavior and serviceability performance of glass fiber-reinforced polymer (GFRP)-reinforced concrete (GFRP-RC) beams fabricated with normal- and high-strength concretes (NSCs and HSCs). The beam specimens measured 4250 mm long x 200 mm wide x 400 mm deep (167.0 x 8 x 16 in.). Three GFRP products with moduli of elasticity ranging from 48.7 to 69.0 GPa (7100 to 10,000 ksi) with sand-coated and helically grooved surface textures were employed. A total of 12 full-scale beams reinforced with GFRP bars and two reinforced with steel bars, serving as control specimens, were tested to failure in four-point bending over a clear span of 3750 mm (148 in.). The test parameters were: 1) type and ratio of the GFRP reinforcement; 2) surface configuration of the GFRP bars; 3) concrete strength; and 4) bar diameter. The test results were reported in terms of deflection, crack width, strains in concrete and reinforcement, flexural capacity, and mode of failure; they were also employed to assess the accuracy of the current deflection and crack-width prediction equations in the FRP-RC codes. The test results revealed that the crack widths were affected by the bar diameter and surface configuration while the deflections were not significantly affected. In addition, the bond coefficient kb value of 1.4 was very conservative for both of the sand-coated and helically grooved GFRP bars in NSC and HSC.

Numerical prediction for corrosion-induced concrete crack width

Corrosion-induced deterioration of reinforced concrete structures results in premature concrete cracking and spalling, leading to ultimate structural collapse. In practice concrete crack width is one of the most important criteria for the assessment of the serviceability of concrete structures. It is therefore desirable to have knowledge of 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 corrosion-induced concrete cracking and crack width for corrosion-affected concrete structures. A cohesive crack model for concrete is presented and direct tension tests on concrete are carried out to determine accurate concrete properties. Worked examples show that the numerical results are in good agreement with the analytical results. It can be concluded that the numerical method developed in the paper can predict corrosion-induced concrete cracking and crack width with reasonable accuracy.

Crack width model for thick reinforced concrete plates subjected to in-plane forces

An extensive experimental program is conducted in the present study to investigate the cracking behavior of two normal strength concrete plates and thirteen high strength concrete plates. The results raise questions about the applicability of the present code approaches to predict the crack width of thick concrete plates used for offshore structures and containment structures for nuclear power plants. The main objective is to provide a simple equation for crack width prediction of a concrete plate to ensure the control of crack openings in designing thick high strength reinforced concrete structures. The model predictions are compared with the results of the tests of reinforced concrete panels subjected to in-plane tension forces along with the code approaches for predicting the crack width.

Plieno pluoštu armuotų gelžbetoninių elementų pleišėtumo analizė

Straipsnyje aptariamas gelžbetoninių elementų armavimo plieno pluoštu efektyvumas, lyginant juos su paprastąja armatūra armuotais elementais. Apžvelgiamos dispersiniam armavimui naudotinos plieno pluošto formos, nusakomi jų privalumai ir trūkumai. Pateikiamas gelžbetoninių elementų betone atsiveriančių plyšių pločių skaičiavimo algoritmas, remiantis EC2 bei (Rilem) metodikomis. Atliekamas skaitinis eksperimentas, analizuojant plieno pluoštu armuotų lenkiamųjų gelžbetoninių elementų pleišėtumą ir lyginant skaičiuotines plyšių pločių reikšmes su eksperimentinėmis reikšmėmis. Nustatomos santykinės skaičiuotinių ir eksperimentinių plyšių pločių reikšmių paklaidos.

Empirical crack estimation on the strengthened concrete members with FRPs

The crack pattern in a strengthened concrete member differs from that in a traditional reinforced concrete member. Generally, average crack spacing and width in strengthened concrete is dependent on strengthening factors other than the rebar. Therefore, it is difficult to determine actual crack widths in a strengthened concrete member with FRPs, such as a beam or a two-way slab, using existing equations. In this study, crack propagation characteristics were identified based on test results; a semi-empirical crack equation is proposed to evaluate the serviceability of strengthened concrete members and the possibility of intermediate crack-induced interfacial debonding failure. Although the proposed equation provides more accurate results, prediction error increases with the strain in the rebar or strengthening material after the rebar yields due to fatigue loading conditions. Therefore, further research is required to improve crack-width predictions after rebar yields.

Comparative Study on Crack Width Prediction for Concrete Flexural Members with GFRP Reinforcement

Fiber reinforced polymer (FRP) bars are being used as an alternative to steel bars to overcome the corrosion problem. Design criteria and methods have to be reinterpreted for its different properties, and several countries have already established corresponding design codes. The method for predicting crack widths of concrete beams with FRP bars provided in ACI440 is based on the method for that with steel bars. Similarly, a modified method based on GB50010 is proposed in this paper to estimate crack widths of concrete beams with FRP bars. Furthermore, the new method together with ACI440 and GB50010 ones are verified by nine test beams in three existing experiments and most of them show a good agreement with the experimental data. Simultaneously, the new method also proves precise and accurate with the same level as the ACI440 one and indicates its potential to estimate crack width in Chinese concrete code system.

EVALUATING AND PROPOSING PREDICTION MODELS OF SHEAR CRACK WIDTH IN CONCORETE BEAMS

This paper presents a comprehensive review on the available prediction models in the literature to estimate shear crack width in reinforced and prestressed concrete members by comparing shear crack openings calculated from prediction model with those obtained from seven experimental investigations to evaluate their accuracy together with effectiveness of factors considered. As a result of this study, the models for the prediction of shear crack spacing and width in reinforced and prestressed concrete beams are proposed. The proposed models show a better correlation with all the test results compared to the other prediction models. The models can predict both average and maximum shear crack width and are applicable to fatigue loading.