Search results

The safety of reinforced concrete structures is generally related to the expected service life of their individual materials. Corrosion damage manifesting on steel reinforcement is usually underestimated, although it greatly affects both load bearing capacity and plastic deformation limits of steel reinforcement. Corrosion damage degree has a great impact on the life expectancy of structures. This paper aims to discuss these issues.

In the present study, an effort has been made to examine and present critical parameters, which are significantly responsible for the differentiation of the corrosion damage level, as far as mass loss is concerned. Consequently, the size effect of the exposed – to the aggressive conditions – area of the specimen, as well as the volume of the protected (against corrosion) area, was examined in detail.

Differential aeration greatly affects the results of corrosion on the material, given that under both high and low oxygen concentration corrosion process is still ongoing.

Findings proceeded are worth mentioning, as they may contribute to a more pertinent evaluation of the corrosion damage (as far as mass loss is concerned), restricting the risk of erroneous predictions concerning the mechanical behavior of steel reinforcement.

As it is widely known, corrosion constitutes a major deterioration factor for reinforced concrete (RC) structures which are located on coastal areas. This phenomenon combined with repeated loads, as earthquake events, negatively affects their service life. Moreover, microstructure of steel reinforcing bars has significant impact either on their corrosion resistance or on their fatigue life.

In the present manuscript an effort has been made to investigate the effect of corrosive factor on fatigue response for two types of steel reinforcement; Tempcore steel reinforcing bars and a new generation dual phase (DP) steel reinforcement.

The findings of this experimental study showed that DP steel reinforcement led to better results regarding its capacity to bear repeated loads to satisfactory degree after corrosion, although this type of steel has less stringent mechanical properties.

Additionally, a fatigue damage material indicator is proposed as a parameter that could rank material quality and its suitability for a certain application. The results of this investigation showed that the fatigue damage indicator can be used as an appropriate index in order to evaluate the overall performance of materials, in terms of strength and ductility capacity.

Structures in seismic areas, during their service lifetime, are subjected to numerous seismic loads that certainly affect their structural integrity. The degradation of these structures, to a great extent, depends on the scale of seismic events, the steel mechanical performance on reversal loads and its resistance to corrosion phenomena. The paper aims to discuss these issues.

Based on the experimental results of seismic steel behavior S400 (BSt III), which was widely used in the past years, a prediction study of seismic steel behavior was conducted in the current study. This prediction on behavior of both reference and corroded steel was succeeded through a simulation of experimental low cycle fatigue conditions (LCF – strain controlled).

At the same time, the present study analyses fatigue factors (ef, a, f_SR, ed, ep, R, b) that define their inelastic relation between tension – strain and a prediction model on behavior of both reference and corroded steel rebar, in seismic loads conditions (LCF), is proposed.

Moreover, this study dealt with the synergy of corrosion factor and the existence of superficial ribs (ribbed and smoothed) in seismic behavior of steel bar S400 (BSt420). The S-N curves that are exported can be resulted in a first attempt of prediction of anti-seismic behavior on reinforced concrete structures with this the same steel class.

In the present study, an effort has been made to estimate the effect of significant parameters on the vulnerability of steel reinforcement to corrosion, using both impressed current density technique and Tafel extrapolation method.

Five sets of tests were performed. Corrosion vulnerability of various diameters, temperature and pH effect on the corrosion process, potential corrosion tendency after a precorrosion period and declination from the theoretical damage prediction model are some of the parameters examined

The results of the tests provide useful information on the main parameters, determining the quality of the corrosion damage.

The originality of the present study is the fact that an effort has been made to estimate the effect of significant parameters on the vulnerability of steel reinforcement to corrosion, using both impressed current density technique and Tafel extrapolation method. Interesting conclusions emerged.

Corrosive agent constitutes a major problem for constructions located in coastal areas, since it keeps affecting their durability. This phenomenon, in synergy with moisture and high temperatures, leads to premature deterioration of the structures. Under these conditions, the need for management of the problem of resistance of steel against corrosion is an issue of paramount importance and a challenge to the structural integrity and reliability. The paper aims to discuss these issues.

The need for management of the problem of resistance of steel against corrosion is an issue of paramount importance and a challenge to the structural integrity and reliability. In the present study, an effort was made to increase the corrosion resistance of the high strength and ductility dual-phase steel B500c category, with the use of different shot blasting processes, without any interference in the chemical composition or in the production mode. In particular, shot blasting treatment was used for both cleaning and creating compressive stresses on the surface of steel bars, according to the pertinent protocols. The modified samples were studied via both conventional characterization methods and electrochemical techniques.

Through the whole surface treatment process of B500c steel, a positive impact came about not only the corrosion resistance, but also the mechanical performance.

Shot blasting process aims to increase the corrosion resistance of high ductility dual-phase steel (B500c), without any interference in the chemical composition or in the production mode.

As it is widely known, corrosion is a major deterioration factor for structures which are located on coastal areas. Corrosion has a great impact on both the durability and seismic performance of reinforced concrete structures. In the present study, two identical reinforced concrete columns were constructed and mechanical tests were organized to simulate seismic conditions. Prior to the initiation of the mechanical tests, the base of one of the two columns was exposed to predetermined accelerated electrochemical corrosion (at a height of 60 cm from the base). After the completion of the experimental loading procedure, the hysteresis curves – for unilateral and bilateral loadings – of the two samples were presented and analyzed (in terms of strength, displacement and dissipated energy). The paper aims to discuss this issue.

In the present study, two identical reinforced concrete columns were constructed and mechanical tests were organized to simulate seismic conditions. The tests were executed under the combination of a constant vertical force with horizontal, gradually increasing, cyclic loads. The implemented displacements, of the free end of the column, ranged from 0.2 to 5 percent. Prior to the initiation of the mechanical tests, the base of one of the two columns was exposed to predetermined accelerated electrochemical corrosion (at a height of 60 cm from the base). After the completion of the experimental loading procedure, the hysteresis curves of the two samples were presented and analyzed (in terms of strength, displacement and dissipated energy).

Analyzing the results, for both unilateral and bilateral loadings, a significant reduction of the seismic performance of the corroded column was highlighted. The corrosion damage imposed on the reference column resulted in the dramatic decrease of its energy reserves, even though an increase in ductility was recorded. Furthermore, more attention was paid to the consequences of the uneven corrosion damage, recorded on the steel bars examined, on ductility, hysteretic behavior and damping ratio.

In the present paper, the influence of the corrosion effects on the cyclic response of structural elements was presented and analyzed. The simulation of the seismic conditions was achieved by imposing, at the same time, a constant vertical force and horizontal, gradually increasing, cyclic loads. Finally, an evaluation of the performance of a column, under both unilateral and bilateral loadings, took place before and after corrosion.

The purpose of this paper is to demonstrate the effect of accelerated environmental loading, i.e. humidity, solar radiation, wet/dry cycling, CO2 concentration and temperature on specimens being initially protected using 4 commercially available coating systems and to evaluate their degradation considering the results.

For the purpose of the study, an accelerated environmental loading was performed in a highly sophisticated chamber able to replicate weather patterns representing the 8 characteristic climate zones of Australia.

The results in terms of degradation patterns can provide a qualitative classification leading to the development of a Dynamic Protection Index Factor (DPIF) which can be used as direct input in life cycle cost analysis appraisal.

This paper is considered to be very important, since the degradation results of different environmental conditions constiture a major problem for structures life inspections and durability

The purpose of this papaer is to study the effects of corrosion on bare and embedded in concrete steel bars and additionaly to study the impact on their mechanical behavior.

The mechanical properties on bare and embedded specimens of dual phase steel bar B500c were measured after tensile tests, before and after corrosion.

The results show superficial severe localized pitting corrosion of embedded specimens in contrast to bare specimens. Also recorded a significant influence of corrosion on the mechanical behavior of the embedded steel specimens in contrast to the corresponding bare specimens. The mechanical behavior of dual phase steel bar B500c, due to chloride induced corrosion, seems to be significantly influenced by the existence of local interactions and the intense of external pit depths of different inclusions (MnS and the FeS etc) close to the outer surface.

The originality in this paper is the research on bare and embedded specimens and the comparison between them and additionaly are presented SEM and EDX analysis with interesting findings.

A new modelling technique is developed to model the nonlinear behaviour of corrosion damaged reinforced concrete (RC) bridge piers subject to cyclic loading. The model employs a nonlinear beam-column element with multi-mechanical fibre sections using OpenSees. The nonlinear uniaxial material models used in the fibre sections account for the effect of corrosion damage on vertical reinforcing, cracked cover concrete due to corrosion of vertical bars and damaged confined concrete due to corrosion of horizontal tie reinforcement. An advance material model is used to simulate the nonlinear behaviour of the vertical reinforcing bars that accounts for combined impact of inelastic buckling and low-cycle fatigue degradation. The basic uncorroded model is verified by comparison of the computation and observed response of RC columns with uncorroded reinforcement. This model is used in an exploration study of recently tested reinforced concrete components to investigate the impact of different corrosion models on the inelastic response of corrosion damaged RC columns.

A series of pushover and cyclic analyses on a hypothetical corroded RC columns are conducted. The impact of corrosion on reinforcing steel and concrete is modelled. The influence of cyclic degradation due to low-cycle fatigue is also modelled.

(1) Corrosion has a more significant impact on ductility loss of RC columns than the strength loss (plastic moment capacity). (2) It was found that the flexural failure is initiated by buckling of vertical bars and crushing of core concrete which then followed by fracture of bars in tension. (3) The analyses results showed that for seismic performance and evaluation of existing corroded bridges monotonic pushover analysis is insufficient. The cyclic degradation due to low-cycle fatigue has a significant influence on the response of corroded RC columns.

The finite element developed in this paper is the most comprehensive model to date that is able to capture the onlinear behaviour of corroded RC columns under cyclic loading up to complete collapse.