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![Ultimate bond strength at rebar surface with corrosion level (XP): specimen with 16mm diameter bar [14].](profile/Hua-Peng-Chen/publication/262799980/figure/fig1/AS:668969279160325@1536506113432/Ultimate-bond-strength-at-rebar-surface-with-corrosion-level-XP-specimen-with-16mm.png)
Ultimate bond strength at rebar surface with corrosion level (XP): specimen with 16mm diameter bar [14].
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The bond between concrete and steel is the critical element of reinforced concrete (RC) structures, which directly affects their load carrying capacity and serviceability. Hence the evaluation of bond strength degradation is an essential parameter to predict the residual strength of RC structures affected by reinforcement corrosion. Existing resear...
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Citations
... Effective and compatible force transfer is necessary for a reinforced concrete structure to behave integrally, and the bond between the surrounding concrete and the embedded reinforcing steel bar serves as this interaction mechanism [46]. Several researchers have investigated and studied the effects of corrosion on the bond of steel with concrete [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40]. (Jiang, Wu et al. 2018) [36] reported bond degradation taking into account the change in adhesion, friction, and mechanical interlocking mechanisms. ...
... It is well understood that the strength of the bond represents the interaction force, in which it enables the integration of two related parts in reinforced concrete (RC) structures, which are the steel reinforcement and the concrete surrounding the steel [1]. Therefore, the reinforced concrete failure is highly related to the steel yielding, in which during the design of RC structures is usually considered as the excited normal bond between the reinforcements and the surrounding concrete. ...
The capacity efficiency of load carrying with the accurate serviceability performances of reinforced concrete (RC) structure is an important aspect, which is mainly dependent on the values of the ultimate bond strength between the corroded steel reinforcements and the surrounding concrete. Therefore, the precise determination of the ultimate bond strength degradation is of paramount importance for maintaining the safety levels of RC structures affected by corrosion. In this regard, hybrid intelligence and machine learning techniques are proposed to build a new framework to predict the ultimate bond strength in between the corroded steel reinforcements and the surrounding concrete. The proposed computational techniques include the multilayer perceptron (MLP), the radial basis function neural network and the genetic expression programming methods. In addition to that, the Levenberg–Marquardt (LM) deterministic approach and two meta-heuristic optimization approaches, namely the artificial bee colony algorithm and the particle swarm optimization algorithm, are employed in order to guarantee an optimum selection of the hyper-parameters of the proposed techniques. The latter were implemented based on an experimental published database consisted of 218 experimental tests, which cover various factors related to the ultimate bond strength, such as compressive strength of the concrete, concrete cover, the type steel, steel bar diameter, length of the bond and the level of corrosion. Based on their performance evaluation through several statistical assessment tools, the proposed models were shown to predict the ultimate bond strength accurately; outperforming the existing hybrid artificial intelligence models developed based on the same collected database. More precisely, the MLP-LM model was, by far, the best model with a determination coefficient (R²) as high as 0.97 and 0.96 for the training and the overall data, respectively.
... It is well understood that the strength of the bond represents the interaction force, in which it enables the integration of two related parts in reinforced concrete (RC) structures, which are the steel reinforcement and the concrete surrounding the steel [1]. Therefore, the reinforced concrete failure is highly related to the steel yielding, in which during the design of RC structures is usually considered as the excited normal bond between the reinforcements and the surrounding concrete. ...
... Bond strength is the interaction force that maintains the integration between steel reinforcement and surrounding concrete in reinforced concrete (RC) structures [48]. In the design phase of RC structures, it is commonly assumed that there is a normal bond condition between reinforcement and surrounding concrete; thus, the failure of concrete depends on the yielding of steel when the ultimate strength of steel bar is reached [26]. ...
The ultimate bond strength of corroded steel reinforcement and surrounding concrete critically affects the load carrying capacity and eventually serviceability of the reinforced concrete structures. This study constructs and verifies a data-driven method for estimating ultimate bond strength. The proposed method is a hybridization of Least Squares Support Vector Regression (LSSVR) and Differential Flower Pollination (DFP) computational intelligence approaches. Since the problem of ultimate bond strength prediction involves nonlinear and multivariate data modeling, the LSSVR is employed to infer the mapping function between ultimate bond strength and its influencing factors of concrete compressive strength, concrete cover, steel type, diameter of steel bar, bond length, and corrosion level. Moreover, in order to overcome the very challenging task of fine-tuning the LSSVR model training, the DFP algorithm, as a population based metaheuristic, is utilized to optimize the performance of the LSSVR prediction model. A data set including 218 experimental tests has been collected from the literature to construct and verify the proposed hybrid method. Experimental results supported by the Wilcoxon signed-rank test point out that the hybridization of LSSVR and DFP can deliver predictive results (root mean square error = 2.39, mean absolute percentage error = 33.82%, and coefficient of determination = 0.84) superior to those of benchmark models including the Artificial Neural Network, the Multivariate Adaptive Regression Splines, and the Regression Tree. Additionally, a software program based on the LSSVR model and the DFP optimization result has also been developed and compiled in Visual C# .Net to ease the model implementation. Hence, the hybrid model of DFP and LSSVR can be a promising alternative to assist engineers in the task of evaluating the health of reinforced concrete structures.
... Many researches have been undertaken to investigate the bond behavior of corroded steels in RC structures, which can be concluded as: experimental research, theoretical analysis and numerical simulation [48]. Some scholars experimentally explored the bond-slip behavior of corroded steels with stirrup constraints [49][50][51]. ...
Bridges, as the structures built to cross obstacles and generally has a relative larger span, play a key role in the road traffic. Pre-tensioned concrete structure is widely used in the bridge construction due to its superiority and advantages. However, with the mass exchange of its environment (water, CO2 and other chemical agents), the prestressing strand would be easy to corrode. Strand corrosion can cause concrete cracking, degrade the bond performance at the strand-concrete interface, lead to prestress loss, and deteriorate the capacity of beams. The present study mainly focuses on the concrete cracking, prestress loss and flexural capacity of pre-tensioned concrete beams after strand corrosion. The main research works are as follows: (1) The relationship between corrosion-induced crack widths and filling proportion of corrosion products has been established. The effect of stirrups on corrosion-induced cracking has also been investigated. An empirical model for crack width, considering the filling proportion of corrosion products and twisting shape of strand, is developed. The proposed model is validated by experimental data. Results show that the filling of corrosion products extends with crack propagation until a critical width. Beyond the critical width, the rust filling extent keeps stable. When the stirrups are used, the critical crack width decreases by 20%, comparing to that without stirrups. (2) The influence of prestress on the strand corrosion-induced concrete cracking is investigated by both experimental and analytical approaches. Experimental data on the critical time of cover cracking, crack width and corrosion loss obtained from the accelerated corrosion test are presented. An analytical model, incorporating the coupled effects of prestress and strand corrosion, is proposed to predict the global process of concrete cracking from initiation to propagation. Results show that prestress can accelerate the corrosion-induced cracking process. By varying prestress from 0 to 75% of strand tensile strength, the critical time of cover cracking decreases by 22% and the crack propagation rate increases by 9%. It is found that the proposed model is accurate in predicting corrosion-induced crack width in prestressed concrete beams. (3) A novel model is proposed to predict the corrosion-induced prestress loss in pre-tensioned concrete beams. The coupling effects of concrete cracking and bond degradation are included into the model. The effective prestress in eight corroded pre-tensioned concrete beams under various stress levels is conducted by the four-point flexural test. Experimental results are employed to verify the proposed model. Prestress loss in corroded pre-tensioned concrete beams depends on corrosion level. Corrosion-induced concrete cracking may not degrade bond strength and effective prestress unless the corrosion level exceeds 6.6%. As corrosion further progresses, bond strength and effective prestress reduce monotonically, and then decrease to zero when the corrosion level reaches 34.0%. (4) An analytical model, incorporating the effects of strand cross-section reduction, material deterioration, concrete cracking and bond degradation, is developed to predict the flexural capacity of corroded prestressed concrete beams. Additionally, the effects of flexural cracks are also included in the model. An equivalent bond stress concept is introduced to consider the effect of flexural cracks, which is further implemented into the flexural capacity prediction of corroded PC beams. The proposed model is validated by the experimental results collected from the previous studies. The flexural capacity deterioration of prestressed concrete beams depends on corrosion degree. Strand corrosion less than 5.5% leads to a slight decrement of flexural capacity. As corrosion progresses, the flexural capacity will exhibit a significant deterioration.
... Clearly, under a similar corrosion rate and the same concrete cover thickness, the bond strength increased with the increase of the sustained load [25]. During the corrosion process, the steel bar was subjected to the tensile force producing a radial component force to the concrete cover, under which, the corroded products were well packed, and the interfacial friction was increased [38,39]. The bond strength thus became higher as the sustained load increased. ...
The dual action of hoop confinement and sustained loading significantly affects the cyclic bond performance between the corroded steel bar and the concrete. This process has been recognized, but the cyclic bond performance has not been well defined. This paper defines and analyzes this process through research involving the fabrication of 30 steel bar-concrete bond specimens. The corrosion of these steel bars was accelerated with and without sustained loading, after which the specimens were subjected to cyclic loading. This investigation covers the corrosion rate, sustained load, and hoop confinement provided by carbon fiber reinforced polymer (CFRP) laminate strips (used to wrap columns), which are referred to herein as CFRP confinement. Attention is also paid to the thickness changes of the concrete cover and its effect on bond strength. The results show that an appropriate degree of corrosion can improve both the static and cyclic bond performance; sustained load was beneficial to the cyclic behavior of the corroded interface in case of existing hoop confinement but detrimental to it if no hoop confinement was applied, indicating that the hoop confinement was of great importance to eliminating the negative influence of the sustained load on the bond performance of the corroded interface. The existence of the hoop confinement significantly improved the hysteretic behavior and the energy dissipation of the interface. The research results provided an experimental basis for the cyclic performance evaluation of structural reinforcement of corroded reinforced concrete structures under the coupling effects of hoop confinement and sustained loading.
... RC structures damaged by reinforcement corrosion compromises structural safety and durability by affecting their performance. The cost associated with managing these corrosion damaged RC structure (repair, rehabilitation, demolition) is in billion dollars[6][7][8][9]. For optimum and cost effective infrastructure management, time-dependent reliability analysis is considered as the effective tool. ...
Structural performance deterioration of reinforced concrete structures has been extensively investigated, but very limited studies have been carried out to investigate the effect of reinforcement corrosion on time-dependent reliability with consideration of the influence of mechanical characteristics of the bond interface due to corrosion. This paper deals with how corrosion in reinforcement creates different types of defects in concrete structure and how they are responsible for the structural capacity deterioration of corrosion affected reinforced concrete structures during their service life. Cracking in cover concrete due to reinforcement corrosion is investigated by using rebar-concrete model and realistic concrete properties. The flexural strength deterioration is analytically predicted on the basis of bond strength evolution due to reinforcement corrosion, which is examined by the experimental data available. The time-dependent reliability analysis is undertaken to calculate the life time structural reliability of corrosion damaged concrete structures by stochastic deterioration modelling of reinforced concrete. The results from the numerical example show that the proposed approach is capable of evaluating the damage caused by reinforcement corrosion and also predicting the structural reliability of concrete structures during their lifecycle.
... But in the case of confined concrete, the confinement stress P cnfx is the total contribution of cracked concrete and the stirrup (P cnfx,st ). By adopting the properties of the thick walled cylinder model with cohesive cracks as described in Fig. 2, Nepal et al. (2013) has modified the expression of confinement stress given by Giuriani et al. (1991), expressed here as where w bx =G f W bx /f t is actual crack width at the rebar surface corresponding to corrosion level; k c is the constant taken as 167; n st is the number of of stirrup leg; A st is the cross-section area of stirrup leg with diameter of D st ; S st is the spacing of stirrup; E st is the modulus of elasticity of steel; α st is the shape factor of stirrup taken as 2; a 2 , a 1 and a 0 are coefficients related to the trilateral local bond-slip law of the stirrup (Giuriani et al. 1991). From Eq. (15b) it is clear that the confinement stress provided by the cracked concrete depends on crack width at the rebar surface (w bx ). ...
Life cycle performance of corrosion affected RC structures is an important and challenging issue for effective infrastructure management. The accurate condition assessment of corroded RC structures mainly depends on the effective evaluation of deterioration occurring in the structures. Structural performance deterioration caused by reinforcement corrosion is a complex phenomenon which is generally uncertain and non-decreasing. Therefore, a stochastic modelling such as the gamma process can be an effective tool to consider the temporal uncertainty associated with performance deterioration. This paper presents a time-dependent reliability analysis of corrosion affected RC structures associated bond strength degradation. Initially, an analytical model to evaluate cracking in the concrete cover and the associated loss of bond between the corroded steel and the surrounding cracked concrete is developed. The analytical results of cover surface cracking and bond strength deterioration are examined by experimental data available. Then the verified analytical results are used for the stochastic deterioration modelling, presented here as gamma process. The application of the proposed approach is illustrated with a numerical example. The results from the illustrative example show that the proposed approach is capable of assessing performance of the bond strength of concrete structures affected by reinforcement corrosion during their lifecycle.
... Many investigations have been conducted during last decade regarding the influence of reinforcement corrosion and concrete cracking on the performance of concrete structures (Vidal et al. 2004, Pantazopoulou and Papoulia 2001, Fang et al. 2013, Nepal et al. 2013, Sadeghi and Rezvani 2013. Research has been undertaken to assess the influence of reinforcement corrosion on concrete cracking (Mullard and Stewart 2011, Ortega et al. 2011, Chen and Xiao 2012, Kim et al. 2012 and to predict the remaining useful service life (Torres-Acosta and Martinez-Madrid 2003, Bhargava et al. 2007, Chen andXiao 2011). ...
Reinforcement corrosion can cause serious safety deterioration to aging concrete structures exposed in aggressive environments. This paper presents an approach for reliability analyses of deteriorating reinforced concrete structures affected by reinforcement corrosion on the basis of the representative symptoms identified during the deterioration process. The concrete cracking growth and rebar bond strength evolution due to reinforcement corrosion are chosen as key symptoms for the performance deterioration of concrete structures. The crack width at concrete cover surface largely depends on the corrosion penetration of rebar due to the expansive rust layer at the bond interface generated by reinforcement corrosion. The bond strength of rebar in the concrete correlates well with concrete crack width and decays steadily with crack width growth. The estimates of cracking development and bond strength deterioration are examined by experimental data available from various sources, and then matched with symptom-based lifetime Weibull model. The symptom reliability and remaining useful life are predicted from the predictive lifetime Weibull model for deteriorating concrete structures. Finally, a numerical example is provided to demonstrate the applicability of the proposed approach for forecasting the performance of concrete structures subject to reinforcement corrosion. The results show that the corrosion rate has significant impact on the reliability associated with serviceability and load bearing capacity of reinforced concrete structures during their service life.
... P cnfx is the total confinement stress contributed by the cracked concrete (P cnfx,c ) and the stirrups (P cnfx,st ). By adopting the properties of the thick walled cylinder model with cohesive cracks, Nepal et al. (2013) has modified the expression of confinement stress given by Giuriani et al. (1991), expressed here as 1 , 1 ...
Corrosion in reinforcement is one of the major problems in the durability of any types of reinforced concrete structures exposed to aggressive environment. Deterioration caused by corrosion reduces the durability and the safety margin of concrete structures to an extent of serious structural failure, causing huge amount of costs in managing these structures. This paper aims to investigate the effects of the reinforcement corrosion on the residual strength of corrosion damaged reinforced concrete structures exposed in aggressive environment. A new analytical method has been proposed to evaluate the residual strength of concrete structures with corroded reinforcement failing in bond. The results from the analytical predictions show that the proposed approach is capable of predicting the residual strength of corrosion damaged concrete structures. A sensitivity analysis has also been carried out considering three important factors: geometrical, mechanical properties of the concrete and type of the corrosion product. The study concludes that residual load carrying capacity of corroded concrete structures decrease significantly due to bond strength loss.
