Effect Of Reinforcement Corrosion Research Articles

A numerical model database for rapid seismic damage assessment of typical regular reinforced concrete frame structures in urban building clusters

A vast city usually encompasses hundreds of thousands or even millions of buildings, majority of which are regular buildings with typical structural configurations. In the seismic damage simulation of cities, efficient and reliable simplified models are required to represent these buildings. A numerical model database of typical regular reinforced concrete (RC) frame structures was developed, utilizing shear models to simulate these RC frame structures. In contrast to existing shear models that are automatically generated based solely on the fundamental rules regulated by the theories of structures and the design codes, the shear models in this study were calibrated using refined numerical models to guarantee precise depiction of RC frame structures. The effects of reinforcement corrosion and the year of construction on structural performance were also considered. First, 108 RC frame structures were designed with typical configurations, strictly adhering to the regulations of design codes. Second, the refined models of the RC frame structures were established with modified material parameters to account for reinforcement corrosion, resulting in 540 refined models. Afterward, the parameters of each shear model were calibrated through cyclic pushover analysis of the corresponding refined numerical model. Finally, the characteristic points of the shear models were further modified to consider the different redundant capacities of the structures constructed in three time phases due to the update of design codes, by which a simplified numerical model database containing 1620 shear models was developed. The models' accuracy in predicting fundamental periods and seismic damage states was verified by comparing them to the refined models and three real RC frame buildings. The effects of the reinforcement corrosion and year of construction on the seismic damage states of the RC frame structures were also discussed. The developed numerical model database can be utilized for the seismic damage assessment of RC frame structures in urban building clusters.

Fragility functions for corroded reinforced concrete columns

Fragility functions for structural members play an important role in the FEMA P-58 methodology for the seismic performance assessment of structures. In this study, fragility functions were developed for aged reinforced columns with corroded reinforcing bars. To this end, an experimental database containing 120 specimens subjected to repeated cyclic loads was compiled from 20 previous studies. The experimental specimens were categorized into three groups: no corrosion damage (NCD), low corrosion damage (LCD), and high corrosion damage (HCD). These damage states were identified by experimental hysteretic responses in terms of the drift angle, which are linked to common methods of repair, including structural repair, structural enhancement, and component replacement. The obtained drift angles were used to fit the log-normal fragility functions of the NCD, LCD, and HCD columns. The effect of reinforcement corrosion was examined by comparing the fragility functions of uncorroded and corroded columns. According to the principles suggested by FEMA P-58, the developed fragility functions were mostly judged to have a high level of quality. The fragility medians of the corroded columns showed a clear decreasing trend along with an increasing degree of corrosion damage. However, the corrosion of the reinforcing bars had a limited effect on the fragility dispersion. The maximum differences in the exceedance probability were calculated by comparing the fragility curves for the LCD and NCD columns, which were greater than 20 % for all concerned damage states. For the HCD columns, the corrosion of the reinforcing bars led to the maximum difference in the exceedance probability, even beyond 50 %, compared to the results for the NCD columns. The above results reveal the significant effect of the corrosion of the reinforcing bars. The specific fragility functions developed for the corroded reinforced concrete columns will facilitate the seismic loss and resilience assessment of aging reinforced concrete building structures.

Effect of reinforcement corrosion on the seismic performance of reinforced concrete shear walls

Corrosion of reinforcing bars is an essential explanation for the deterioration of reinforced concrete (RC) members. Consequently, the seismic performance and collapse mechanism of RC members considerably decreased and altered for the sake of corrosion of reinforcing bars, respectively. For evaluating the effect of corrosion of reinforcing bars on the seismic performance of RC shear walls, four specimens with the corrosion rates of 0%, 3%, 9%, and 15% were investigated under the cyclic loadings. Test consequences illustrated that the seismic performances of corroded RC shear walls for instance crack pattern, hysteretic responses, ductility, energy dissipation capacity, etc., significantly decreased attributed to the corrosion of reinforcing bars, especially for severely corroded walls. Furthermore, the analytical model based on ACI 318-14 considering the influence of corrosion of reinforcing bars on the shear strength of RC shear walls and finite element model for simulating the deterioration of corroded walls were proposed and conducted, respectively.

Nonlinear Finite Element Analysis of Corroded Reinforced Concrete Beams

Corrosion in reinforcing bars is a major cause of concern for sustainability of Reinforced Concrete (RC) structures exposed to extreme environmental conditions. Various RC structures, such as bridges and buildings are adversely affected due to the rebar corrosion, reducing its global load carrying capacity and ductility. In order to ensure an earthquake resistant design of any structure, the ductility of structural members is of chief concern. However, corrosion of reinforcing steel in RC members reduces its seismic performance. Thus, for safety and economic viability of any RC structure, an effective maintenance and repair work strategy is necessary. Based on the strong column - weak beam design concept of RC frames, the beams are the first structural members to absorb damage due to earthquake. Thus, to carry out maintenance and repair work, structural health assessment of RC beams considering the effect of reinforcement corrosion is of utmost importance. The present study aims at establishing a relation between the amount of corrosion induced and its effect on the ductility of an RC beam. A 3D Finite Element (FE) model of an RC beam including the effects of corrosion for nonlinear performance assessment has been modelled in ABAQUS. The FE model is validated with past experimental study including the effects of corrosion. Modelling of uniform corrosion in reinforcement bars involves defining the loss of bond between rebars and concrete, inducing spalling stresses on concrete and reduction in the cross-section area of the rebars. Bond-slip model between surface of concrete and reinforcement has been incorporated through cohesive surface. Spalling stress for uniform corrosion is applied in form of outward uniform pressure on the reinforcement and concrete interface. The cracking of cover concrete due to corrosion along with the flexural cracking in concrete due to incremental loading are implemented together in the present study. A comprehensive FE model is developed in order to obtain correct assessment of corroded beams. As observed from the FE model, the failure mechanism of the considered corroded RC beam is observed to be mostly shear failure as the corrosion level increases. Concrete crushing at the center of the RC beam is identified at the failure point of the beam due to corrosion induced damage. Evolution of displacement ductility index with respect to corrosion is determined for an RC beam based on the numerical study. It has been observed that the displacement ductility index of the beam is reduced significantly after considering a corrosion level of about 12%. Hence, the present study is an effort to establish a relation between structural performance of RC beams and level of reinforcement corrosion, which will be useful in proactive maintenance and repair work for corroded RC beams.

Effects of Reinforcement Corrosion and Sustained Load on Mechanical Behavior of Reinforced Concrete Columns.

The effects of reinforcement corrosion and sustained axial load on mechanical performance of reinforced concrete (RC) columns were investigated in the present study. Three different degrees of reinforcement corrosion were achieved by controlling the durations of accelerated corrosion test (i.e., 16 days, 31 days, and 63 days). Three levels of sustained axial load (i.e., 0%, 30%, and 60% of the ultimate bearing capacity) were concentrically applied on column specimens. The impressing current and the sustained load were applied on column specimens simultaneously, mimicking the degradation of RC columns in real structures. Results indicated that transverse stirrups yielded higher corrosion degree than that of the longitudinal rebar under identical duration of accelerated corrosion test. The application of sustained axial load improved the performance of corroded RC columns in terms of the reinforcement corrosion, the ultimate axial load, as well as the stiffness. Additionally, more longitudinal cracks along the main rebar were exhibited for column specimens subjected to sustained axial load. For both loaded and unloaded column specimens, corrosion of reinforcing steels exacerbated the mechanical deterioration of RC columns, lowering the ultimate load carrying capacity and the axial deformation compared to the uncorroded columns.

Effect of Reinforcement Corrosion on the Seismic Performance of Reinforced Concrete Shear Walls

Effect of Reinforcement Corrosion on the Seismic Performance of Reinforced Concrete Shear Walls

Effects of reinforcement corrosion on reinforced concrete buildings

The aim of this paper is to present the different effects of reinforcement corrosion on reinforced concrete buildings. A hypothetical five-storey reinforced concrete building frame was designed for this purpose. Three different modes of action were selected – corrosion on the ground floor alone, corrosion on one facade and corrosion on two neighbouring facades of the building. For each mode of action, different corrosion scenarios were selected, which were arranged in terms of mass loss from zero to 15% in ascending order an in 3% steps. Pushover analyses of the building were performed for each corrosion scenario and the results of these analyses were used to perform a structural performance evaluation conforming to Eurocode 8. A general decrease in structural performance was determined with significant changes in the dynamic characteristics of the building. The level of decrease depended on the corrosion scenarios and the modes of action. Important structural behaviour alterations and premature damage occurrences were found, in addition to a reduction in the displacement ductility of the building. For severe-corrosion scenarios, reductions in moment and curvature capacities could shift the structural behaviour of the load-bearing members from ductile to non-ductile.

Bond strength of corroded reinforcements in concrete after high-temperature exposure

Reinforcement corrosion is common in concrete structures subjected to chloride exposure. The bond behaviours between corroded reinforcements and concrete after high-temperature exposure are important in the fire damage assessment of aging concrete structures. The effects of reinforcement corrosion on the bond behaviour between concrete and reinforcements after high-temperature exposure is investigated in this paper. Corroded pull-out specimens were prepared using accelerated corrosion tests. These corroded specimens were heated in an electric resistance furnace and then subjected to pull-out tests. The test results showed that the failure mode of the pull-out specimen was affected by the degree of steel corrosion, the temperature experienced, concrete cover depth and stirrup usage. The bond behaviour was less influenced when the degree of corrosion was less than 0.05 or when the exposure temperature was less than 200 °C. The bond strength reduced significantly when the temperature was between 400 and 600 °C or when the corrosion degree was greater than 0.05. The concrete cover depth and stirrup usage also had an obvious effect on the bond strength after exposure to different temperatures, whereas these parameters had little influence on the bond strength when the experienced temperatures exceeded 600 °C. Finally, a calculation method for bond strength was proposed considering the corrosion degree and temperature.

Comparative post-yield performance evaluation of flexure member with corroded reinforcement

Existing plastic hinge models for reinforced concrete beams do not consider the effect of reinforcement corrosion. This paper represents the plastic hinge model of corroded Reinforced Concrete (RC) beams tested experimentally as well as investigated analytically through nonlinear finite element modeling. An attempt is then made to arrive at simple empirical equation for maximum moment including the percentage of corrosion, using soft computing technique of Genetic Programming (GP). Simply supported beams are analysed with varying grades of concrete and type of reinforcement along with the condition of reinforcement by applying two-point loading (approximately 1/3rd and 2/3rd of span) and verified with the experiments performed. Test results show that the model can accurately predict the force deflection response and failure mode. The results show decrease in the moment and rotation capacity with the increase in corrosion percentage of reinforcement bars used in RC beams. The equation obtained as an output of GP models indicates the influence of yield strength of reinforcement, concrete grade and percentage of corrosion of RC beam over maximum moment carrying capacity.

Flexural performance of corroded continuous RC beams rehabilitated by ICCP-SS

Continuous reinforced concrete (RC) beams are popular structural components. However, RC structures in corrosive environments can be degraded due to steel reinforcement corrosion. In this study, a dual-functional intervention method, i.e., impressed current cathodic protection and structural strengthening (ICCP-SS), is adopted to repair degraded beams. The carbon fabric-reinforced cementitious matrix (C-FRCM) composite serves dual functions in the intervention method. The effects of reinforcement corrosion, cathodic protection and the C-FRCM strengthening system on the behaviors of continuous beams should be investigated. This study provides experimental data on continuous RC beams rehabilitated by ICCP-SS in corrosive environments and investigates the structural responses, moment redistributions and design rules of these beams. The electrochemical monitoring results showed that steel reinforcements in continuous beams under corrosive environments are successfully protected. Five-point bending test results showed that beams strengthened with C-FRCM composites have higher yielding loads and ultimate loads than corroded beams without protection. Comparison of the predicted and measured moment capacities at the central support and midspan showed that the design methods generally underestimate the moment capacities of unstrengthened sections and overestimate those of strengthened sections.

Influence of reinforcement corrosion on fire performance of reinforced concrete beams

Abstract Corroded steel bars frequently exist in concrete structures under chloride exposure conditions; moreover, corroded reinforced concrete (RC) is not fireproof. This paper presents an investigation on the effects of reinforcement corrosion on the fire performance of RC beams. The corroded RC beams were prepared using an accelerated corrosion test, and the fire test was carried out according to the ISO 834 standard fire. Test results indicated that corrosion of the tensile steel bars led to premature failure of the concrete beams. During the fire tests, with the increase of the steels’ degree of corrosion, the midspan deflection of the RC beam rapidly develops, while the fire resistance obviously decreases. Because the thermal diffusion coefficient of air is higher than that of concrete, a corrosion induced crack increased the heating rate of the corroded steel bar inside the concrete, and the vertical cracks caused by the applied loading had a significant impact on the temperature field of the beam tensile zone. Notably, reinforcement corrosion may lead to brittle failure in a balanced-reinforced beam subjected to fire.

Structural behavior of corroded reinforced concrete beams under sustained loading

This paper presents the results of an experimental study designed to investigate the combined effects of corrosion and sustained loads on the structural performance of reinforced concrete beams. A total of eight RC beams, including both uncorroded beams and corroded ones accelerated by the impressed current method, were tested. All the beams were subjected to a four-point sustained bending load which was equivalent to 17%, 33% or 50% of the designed ultimate load, respectively. Corrosion degree, crack patterns, crack width and mid-span deflection of the beams were monitored during the test. The results showed that reinforcement corrosion had no obvious effect on the transverse crack spacing and a slight effect on the development of transverse crack width for the beams under simultaneous loading and corrosion. A higher load level and a lower current density allow for more sufficient oxidation of corrosion products with a larger volume expansion rate, leading to premature initiation and rapid propagation of corrosion cracking, and more obvious deflection development of RC beams. For a beam under simultaneous loading and reinforcement corrosion, the effect of reinforcement corrosion on its deflection cannot be ignored, because it may exceed creep effect at a relatively low corrosion degree.

Research on compression behavior of coral aggregate reinforced concrete columns under large eccentric compression loading

The large eccentric compression behavior of 9 coral aggregate reinforced concrete columns (CARCC) and 2 ordinary Portland reinforced concrete columns (OPRCC) was tested. The concrete type, concrete strength grade and reinforcement type were selected as parameters. The crack development, deformation and bearing capacity were investigated. The relationships of load–displacement and load–axial compressive (tensile) strain were established. The applicable calculation model for the ultimate bearing capacity (Nu) of CARCC under large eccentric compression was suggested. The results showed that the compression behavior of CARCC were similar to OPRCC. Under the same mix proportion, the lateral stiffness and ductility of CARCC of C25 were both worse than OPRCC of C35. Under the same load, the load shared by reinforcements in CARCC was more than that shared by reinforcements in OPRCC. The application of organic new coated steels, 3% calcium nitrate inhibitor and concrete strength grade over C60 in the CARCC was suggested to effectively inhibit reinforcement corrosion and extend the effective service life of the structure. A comprehensive consideration on the effects of reinforcement corrosion and slip of the coated steel on Nu of CARCC was performed. Consequently, a calculation model for the Nu of CARCC under large eccentric compression was proposed.

Seismic behavior of low-corroded reinforced concrete short columns in an over 20-year building structure

In reinforced concrete (RC) structures, reinforcement corrosion, concrete carbonization, and chloride ion erosion occur during service life, which deteriorate the seismic structural capacity of the structures. Most researchers have focused on the effect of the reinforcement corrosion on the seismic behavior of RC columns showing flexural behavior. On the other hand, research on the influence of the combined reinforcement corrosion and concrete carbonization on the seismic behavior of in-service RC columns showing shear-flexural behavior has not been performed. The present study evaluates the seismic performance of low-corroded in-service RC columns showing shear failure under cyclic load. Four RC columns with shear-span ratio 2.3 and light transverse reinforcement were obtained from an in-service RC moment frame building constructed in 1987, and quasi-static cyclic tests were conducted to investigate the seismic behavior of these columns. For the test parameters, axial compression force ratios and longitudinal bars arrangements were considered. The test results showed that as the compression force ratio increased, the failure modes of the in-service RC columns shifted from shear-bond failure to shear-compression failure, and the ductility and energy dissipation capacity decreased. The shear strength of the column specimens was evaluated by five existing shear strength models, considering the effect of reinforcement corrosion. Finally, seismic performance of RC short columns with corroded bars was discussed.

Modified axial-shear-flexure interaction approaches for uncorroded and corroded reinforced concrete beams

Two new axial-shear-flexure interaction approaches, the modified axial-shear-flexure interaction (MASFI) approach and its extension to consider the effects of reinforcement corrosion (MASFI-C), are proposed in this research to predict the lateral force-displacement behavior of uncorroded and corroded reinforced concrete (RC) beams, respectively. The MASFI considers the effects of shear on concrete confinement and buckling of longitudinal reinforcement, and the softening effect of tensile strains of transverse reinforcement on the flexural concrete compression zone. The MASFI-C considers the effect of reinforcement corrosion by using the corroded constitutive models for concrete, steel, and bond. The proposed models were used to predict the envelope response of uncorroded and corroded RC beams tested using cyclic loading. It was found that the MASFI captured well the behavior of uncorroded beams and the effects of shear on concrete confinement and buckling of longitudinal reinforcement are important for predicting the post-peak behavior. The MASFI-C with the average residual cross-sectional area and average strengths of corroded reinforcement captured well the initial stiffness and strength behavior of corroded RC beams before fracture of corroded reinforcement. However, with the average ultimate strain of corroded reinforcement, the MASFI-C did not captured well the drift at which longitudinal or transverse reinforcement fractured due to the variation in corrosion mass loss among corroded reinforcement and in ultimate strain for a given corrosion mass loss, and due to inelastic deformations caused by bending process for corroded transverse reinforcement.

Axial loading capacity of concrete‐jacketed RC columns with pre‐ and post‐corrosion damage

AbstractThe main objective of this study is to investigate the effect of pre‐ and post‐jacketing corrosion and loading damage on concrete‐jacketed reinforced concrete (RC) columns under uniaxial loading and to develop a methodology for predicting the corresponding compressive strength. The pre‐ and post‐damage involved preloading up to 50 % of the peak load of the core column, an electrochemical process to accelerate the migration of chlorides from an external electrolyte into the test columns and a wetting–drying cycle process with a controlled current to speed up the corrosion of the steel reinforcing bars in the test columns. Uniaxial loading tests were performed to determine the structural performance of the concrete‐jacketed columns with and without corrosion damage. The failure mode and load–displacement and load–strain responses of the test columns were recorded, and the related mechanisms are discussed. A model capable of evaluating the compressive strength of unjacketed or jacketed RC columns with and without corrosion damage was then developed. The analytical approach considered the effect of reinforcement corrosion on the effective loadbearing area of the concrete and the confinement effect of the stirrups. The analytical results agree well with the experimental results, indicating the reliability and effectiveness of the models developed.

Effects of Reinforcement Corrosion and Repeated Loads on Performance of Reinforced Concrete Beam

The effects of both steel corrosion and repeated loading on performance of reinforced concrete beam were investigated. Repeated loads were applied to corroded reinforced concrete specimens with corrosion levels ranging from 0% to 5%. The experiments were conducted for the deflection, cracking, stiffness, bearing capacity and failure type of the corroded beams. For corrosion levels less than 5%, the residual deflection was about 3% of the maximum value of failure deflection. The deflection of beams of high corrosion levels were generally greater than those of low corrosion levels, while the flexural rigidity of the high corrosion levels decreased more in value than those of low corrosion levels. The failure modes of beams changed from plastic type to brittle type with the increase of corrosion level.

Risk-based optimum repair planning of corroded reinforced concrete structures

Civil engineering infrastructure is aging and requires cost-effective maintenance strategies to enable infrastructure systems operate reliably and sustainably. This paper presents an approach for determining risk-cost balanced repair strategy of corrosion damaged reinforced concrete structures with consideration of uncertainty in structural resistance deterioration. On the basis of analytical models of cover concrete cracking evolution and bond strength degradation due to reinforcement corrosion, the effect of reinforcement corrosion on residual load carrying capacity of corroded reinforced concrete structures is investigated. A stochastic deterioration model based on gamma process is adopted to evaluate the probability of failure of structural bearing capacity over the lifetime. Optimal repair planning and maintenance strategies during the service life are determined by balancing the cost for maintenance and the risk of structural failure. The method proposed in this study is then demonstrated by numerical investigations for a concrete structure subjected to reinforcement corrosion. The obtained results show that the proposed method can provide a risk cost optimised repair schedule during the service life of corroded concrete structures.

Effect of Reinforcement Corrosion on Bond Behaviour

One of the major degradation processes of reinforced concrete structures is the corrosion of the steel reinforcement. The main reason associated with the deterioration of reinforced concrete due to reinforcement corrosion is not the reduction in mechanical strength of the reinforcing bar itself, but rather than that the pressure exerted from the expansion of the corrosion products. This may result in damage of the structures due to expansion, cracking and eventually spalling of the concrete cover. In addition to this, the damage of construction may be caused by loss of bond between reinforcement and concrete and loss of reinforcement cross-sectional area. The paper introduces effect of corrosion to bond between reinforcement and concrete.

Effects of Reinforcement Corrosion on the Performance of RC Frame Buildings Subjected to Seismic Actions

AbstractCorrosion of reinforcing bars is a common deficiency for existing RC buildings, which may have significant adverse effects on seismic performance of those buildings. The main effects of corrosion of reinforcing bars are strength loss as a result of reduction of the effective cross-sectional area of the bars, reduced bond strength between concrete and bars as a result of the increased volume of the bars because of rust products, and reduced elongation capacity of the bars as a result of the concentration of plastic deformations at sections of corrosion pits. The last item (concentration of plastic deformations of reinforcing bars only at the most heavily corroded sections rather than occurring all through the potential plastic hinge length) has a very remarkable adverse effect on the displacement capacity of existing buildings. It is known that the displacement capacity is as important as strength, particularly for the buildings that are designed to exhibit ductile behavior during earthquakes. In t...