Charis Apostolopoulos | University of Patras (original) (raw)

Papers by Charis Apostolopoulos

Research paper thumbnail of The challenge of dairying in Greece

Bulletin International Dairy Federation, 1999

Research paper thumbnail of Letter to the Editor commenting on “Multilevel finite element modeling for the prediction of local cellular deformation in bone,” Deligianni DD and Apostolopoulos CA (2008) Biomech Model Mechanobiol 7(2):151–159

Biomechanics and Modeling in Mechanobiology, 2008

Dear Editor: Deligianni and Apostolopoulos (2008) use a clever modelling approach to reach the co... more Dear Editor: Deligianni and Apostolopoulos (2008) use a clever modelling approach to reach the convincing conclusion that the micromorphology of osteocytarian canaliculi network produces an amplification of the strain observed at the continuum (organ) level sufficient to move the strain experienced by the osteocytes within the lacunae to a level above 10,000 microstrain, for which in vitro studies observe a direct mechanosensitivity of the osteocytes. Because of this the authors conclude that the direct mechanotransduction hypothesis that reigned in the 1980s and 1990s (bone strains, cells attached to bone strain as well, cells sense such strain and react with a biochemical cascade that controls the bone adaptation; Huiskes et al. 2000) remains viable, since the very high deformation found necessary to activate such direct mechanotransduction might indeed be observed in physiological conditions at the cell level, because of such strain amplification. While the paper is clearly speculative, the approach and reasoning are solid and convincing. However, the authors seem to ignore what we consider an uttermost important point. The mineralised extracellular matrix, what we usually call bone tissue, shows very consistently in many different experiments, damage and even complete failure for strains in the range of 6,000–10,000 microstrain (Bayraktar et al. 2004; Currey 2004; Morgan et al. 2005a) almost independently from the degree of mineralization and the micromorphology of bone tissue. Detectable damage has been reported even for lower strains (around 2,000 microstrain) when

Research paper thumbnail of Residual Endurance of Corroded Aircraft Structural Elements

Research paper thumbnail of The Effect of the Shot Blasting Process on the Dynamic Response of Steel Reinforcement

Metals

As it is widely known, corrosion poses a real threat for reinforced concrete structures, especial... more As it is widely known, corrosion poses a real threat for reinforced concrete structures, especially when they are located in coastal areas. This phenomenon, in conjunction with repeated loads, such as intense seismic events, adversely affect their useful service life. Several experimental studies have presented the magnitude of degradation of steel reinforcement due to corrosion in the presence of fatigue, which affects either the serviceability or durability of steel reinforcement. As a result, the current experimental study presents the results of the shot blasting process of steel reinforcement at various times of exposure to a corrosive environment and the influence on their dynamic response after the execution of low cycle fatigue tests at different constant strain amplitudes. The findings show the beneficial effect of the shot blasting process in terms of percentage mass loss and the improvement of mechanical performance of steel bars in terms of service life and energy dissip...

Research paper thumbnail of Fatigue damage indicator of different types of reinforcing bars

International Journal of Structural Integrity

PurposeAs it is widely known, corrosion constitutes a major deterioration factor for reinforced c... more PurposeAs 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.Design/methodology/approachIn 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.FindingsThe 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.Originality/valueAdditionally, a fatigue damage material indicator ...

Research paper thumbnail of Effect of Corrosion on the Hysteretic Behavior of Steel Reinforcing Bars and Corroded RC Columns

Applied Sciences

The corrosion of steel reinforcement negatively influences the mechanical performance of reinforc... more The corrosion of steel reinforcement negatively influences the mechanical performance of reinforced concrete (RC) elements reducing both their strength capacity and ductility. Especially in seismic prone areas, the degradation of the cyclic behavior of corroded RC elements is more intense, limiting the service life of structures and leading to premature failures. In the present paper, in order to study the degraded behavior of the embedded (in concrete) steel reinforcement under cyclic loading, laboratory corrosion experiments were performed on embedded steel reinforcing bars. Thereafter, mechanical tests under dynamic loadings with gradually increased deformations were carried out. From the experimental study, hysteretic models of the non-linear behavior of steel bars were extracted in non-corroded and corroded conditions, in the case of both uniform and pitting corrosion. Based on the hysteretic models of steel bars, an analysis of the cyclic response of (non-corroded and corroded...

Research paper thumbnail of Advanced Metallic Materials and Processes

The following main tendencies in the evolution of metal science are described: development of new... more The following main tendencies in the evolution of metal science are described: development of new materials with predetermined mechanical, physical and functional properties as e.g. amorphous materials, ultra-fine-grained (including nanostructured) etc. Advanced resource-saving technologies applied to traditional and new materials as e.g. different schemes of thermomechanical processing, cyclic thermal treatment, cyclic deformation treatment etc. are presented. Application of advanced techniques: laser beam, highenergy electron-beam, plasma and simulation technique are described as well.

Research paper thumbnail of Finite-element simulation of a beam-to-column connection with circle web opening

Proceedings of the ICE - Structures and Buildings, 2012

Connections with pre-cast hollow sections are commonly preferred in recent times because of the c... more Connections with pre-cast hollow sections are commonly preferred in recent times because of the convenience they offer. The present work describes a finite-element model developed to simulate the structural behaviour of beam-to-column joints with hollow sections. In order to verify the model, a simple beam-to-column joint is modelled in a laboratory test; the joint consists of an end-plate welded to a beam and bolted to a column. The validity of the finite-element model is then established by comparing its results with the corresponding experimental tests. Thereafter a parametric study is carried out to investigate the structural behaviour with variations in the pre-cast web opening radius and distance from the connection.

Research paper thumbnail of The design and application of selected techniques for the environmental and energy improvement of urban areas- the case study of Patras, greece

The present study deals with various techniques aiming primarily to improve the environmental and... more The present study deals with various techniques aiming primarily to improve the environmental and microclimatic quality of urban areas, and, secondly, to minimize the energy consumption in the buildings’ sector based mainly on bioclimatic principles and criteria in the same area. The selected techniques, which include the re-use of treated wastewater effluents using the wastewater treatment plan, as well as solar passive heating/cooling techniques, have been applied in a specific urban area located in Patras, a large city of western Greece. The application of the treated wastewater effluents re-use in urban areas is possible through the combined reuse of the treated municipal wastewater effluents indoors for domestic use, as well as for irrigating plants in outdoor spaces. One building of the area was selected as representative, and its thermal behavior was simulated and analyzed primarily in its existing situation, and, furthermore, after using several passive cooling techniques, such as the installation of a green roof system, the use of insulating materials in the external walls and roof, the insertion of an atrium, night ventilation techniques, etc. The obtained results showed that with regards to the cooling load, the application of night ventilation and a green roof system provided the higher energy saving, while with respect to the heating load, the more efficient improvements were the insulation on the building’s external walls and roof.

Research paper thumbnail of The effect of ribs on the mechanical behavior of corroded reinforcing steel bars S500s under low-cycle fatigue

Materials and Structures, 2007

Research paper thumbnail of Tensile properties of corroded embedded steel bars B500c in concrete

International Journal of Structural Integrity, 2013

PurposeThe corrosion of reinforcing steel bars reduces significantly the life and durability of c... more PurposeThe corrosion of reinforcing steel bars reduces significantly the life and durability of concrete structures. This critical concern causes great losses to the economy and industry. The purpose of this paper is to estimate the effects of corrosion on the tensile mechanical properties of embedded steel bars B500c in concrete.Design/methodology/approachThe concept is based on the curve fitting modelling, as well the mathematical correlation of the tensile mechanical properties between corroded bare and corroded embedded steel bars. In order to achieve this, extensive experiments were carried out on both bare (Ø8, 10, 12, 16 and 18 mm) and embedded (Ø8 mm) steel bars B500c, which were subjected to artificially accelerated corrosive conditions in a chloride‐rich atmosphere for several exposure times.FindingsThe research results show that the estimation method is available and effective in simulating the tensile mechanical behaviour of corroded reinforcing steel bars B500c.Original...

Research paper thumbnail of Coastal bridges and the 120 Life Span – the Rio‐Antirio case study

International Journal of Structural Integrity, 2010

PurposeThe purpose of this paper is to shed light on the uncertainties related to durability pred... more PurposeThe purpose of this paper is to shed light on the uncertainties related to durability prediction of coastal bridges.Design/methodology/approachThe paper describes the problems encountered with the Rio‐Antric bridge in Greece.FindingsEven the most accurate models, especially those traditionally employed, fail to provide secure estimates, cases which create serious questions about suggested life spans. Local conditions, large‐scale effects, construction practise, dynamic phenomena, etc. create such a complex web of parameters able to negate even the most conservative estimates. As such, cathodic protection systems should be employed in every coastal structure as a defence measure.Originality/valueThe paper offers a typical example of how far engineering, material science and construction practise has to go to guarantee that any designed life is accurately met.

Research paper thumbnail of The Influence of Corrosion and Cross-Section Diameter on the Mechanical Properties of B500c Steel

Journal of Materials Engineering and Performance, 2008

Research paper thumbnail of The Effect of Shot Blasting Process on Mechanical Properties and Anti-Corrosive Behavior of Steel Reinforcement

Metals, 2022

The need to confront the problem of corrosion resistance of steel reinforcement is an issue of ma... more The need to confront the problem of corrosion resistance of steel reinforcement is an issue of major importance and a perpetual challenge to the structural integrity and reliability in reinforced concrete (RC) structures. The current experimental study presents the results of the combined effect of shot blasting and coating on steel reinforcing bars in respect to their anticorrosive resistance and their mechanical behavior, at various times of exposure to corrosive environment. In the present manuscript, a comparison of different abrasive materials was primarily conducted, via electrochemical measurements (Tafel tests), to estimate the corrosion current (icorr) for each abrasive material. After the indication that corrosion resistance can be modified by shot blasting with corundum, the method of Zn85Al15 coating was chosen to further investigate the combined effect of shot blasting with coating, in terms of percentage mass loss and mechanical behavior of steel reinforcement. The res...

Research paper thumbnail of Characteristic Defects-Corrosion Damage and Mechanical Behavior of Dual Phase Rebar

The demands for constructions with high mechanical performance, located in seismic areas, express... more The demands for constructions with high mechanical performance, located in seismic areas, expressed through EC2 and EC8part3, were importantly satisfied mainly with the use of Tempcore dual phase steel bars. High mechanical performance of dual phase steel comes from the combination of the mechanical properties of each individual phase. However, several times have been reported problems concerning their structural cohesion. In the present study four different technical classes (DP) of reinforcing steel bars were used: B500c, B450c, B400c and B500b. SEM and EDX analyses were used, focusing not only on the internal defects regions of the materials (before and after corrosion), but also on the external areas affected by pitting corrosion. Moreover, in terms of the experimental procedure, mechanical tensile tests were conducted, on both corroded and non corroded reinforcing steel bar specimens and the pertinent results are analyzed. The conclusion from the present study is that both inte...

Research paper thumbnail of Effects of corrosion on low-cycle fatigue (seismic) behaviour of high-strength steel reinforcing bars (Rusteel)

Research paper thumbnail of Seismic resistance prediction of corroded S400 (BSt420) reinforcing bars

International Journal of Structural Integrity

Purpose Structures in seismic areas, during their service lifetime, are subjected to numerous sei... more Purpose 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. Design/methodology/approach 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). Findings At the same time, the present study analyses fatigue factors (ef, a, fSR, ed, ep, R, b) that define their inelastic relation between tension – strain and a prediction model on behavior of both reference...

Research paper thumbnail of Critical parameters affecting mass loss of steel reinforcement

International Journal of Structural Integrity

Purpose The safety of reinforced concrete structures is generally related to the expected service... more Purpose 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. Design/methodology/approach 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. Findings Differential aeration greatly affects the results of corrosion on the material, given that under both high and ...

Research paper thumbnail of Computer-aided approach of parameters influencing concrete service life and field validation

Research paper thumbnail of Seismic assessment of RC column under seismic loads

International Journal of Structural Integrity

PurposeAs it is widely known, corrosion is a major deterioration factor for structures which are ... more PurposeAs 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.Design/methodology/approachIn the present study, two identical reinforced concrete columns were constructed and mechanical tests were organized to simulate s...

Research paper thumbnail of The challenge of dairying in Greece

Bulletin International Dairy Federation, 1999

Research paper thumbnail of Letter to the Editor commenting on “Multilevel finite element modeling for the prediction of local cellular deformation in bone,” Deligianni DD and Apostolopoulos CA (2008) Biomech Model Mechanobiol 7(2):151–159

Biomechanics and Modeling in Mechanobiology, 2008

Dear Editor: Deligianni and Apostolopoulos (2008) use a clever modelling approach to reach the co... more Dear Editor: Deligianni and Apostolopoulos (2008) use a clever modelling approach to reach the convincing conclusion that the micromorphology of osteocytarian canaliculi network produces an amplification of the strain observed at the continuum (organ) level sufficient to move the strain experienced by the osteocytes within the lacunae to a level above 10,000 microstrain, for which in vitro studies observe a direct mechanosensitivity of the osteocytes. Because of this the authors conclude that the direct mechanotransduction hypothesis that reigned in the 1980s and 1990s (bone strains, cells attached to bone strain as well, cells sense such strain and react with a biochemical cascade that controls the bone adaptation; Huiskes et al. 2000) remains viable, since the very high deformation found necessary to activate such direct mechanotransduction might indeed be observed in physiological conditions at the cell level, because of such strain amplification. While the paper is clearly speculative, the approach and reasoning are solid and convincing. However, the authors seem to ignore what we consider an uttermost important point. The mineralised extracellular matrix, what we usually call bone tissue, shows very consistently in many different experiments, damage and even complete failure for strains in the range of 6,000–10,000 microstrain (Bayraktar et al. 2004; Currey 2004; Morgan et al. 2005a) almost independently from the degree of mineralization and the micromorphology of bone tissue. Detectable damage has been reported even for lower strains (around 2,000 microstrain) when

Research paper thumbnail of Residual Endurance of Corroded Aircraft Structural Elements

Research paper thumbnail of The Effect of the Shot Blasting Process on the Dynamic Response of Steel Reinforcement

Metals

As it is widely known, corrosion poses a real threat for reinforced concrete structures, especial... more As it is widely known, corrosion poses a real threat for reinforced concrete structures, especially when they are located in coastal areas. This phenomenon, in conjunction with repeated loads, such as intense seismic events, adversely affect their useful service life. Several experimental studies have presented the magnitude of degradation of steel reinforcement due to corrosion in the presence of fatigue, which affects either the serviceability or durability of steel reinforcement. As a result, the current experimental study presents the results of the shot blasting process of steel reinforcement at various times of exposure to a corrosive environment and the influence on their dynamic response after the execution of low cycle fatigue tests at different constant strain amplitudes. The findings show the beneficial effect of the shot blasting process in terms of percentage mass loss and the improvement of mechanical performance of steel bars in terms of service life and energy dissip...

Research paper thumbnail of Fatigue damage indicator of different types of reinforcing bars

International Journal of Structural Integrity

PurposeAs it is widely known, corrosion constitutes a major deterioration factor for reinforced c... more PurposeAs 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.Design/methodology/approachIn 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.FindingsThe 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.Originality/valueAdditionally, a fatigue damage material indicator ...

Research paper thumbnail of Effect of Corrosion on the Hysteretic Behavior of Steel Reinforcing Bars and Corroded RC Columns

Applied Sciences

The corrosion of steel reinforcement negatively influences the mechanical performance of reinforc... more The corrosion of steel reinforcement negatively influences the mechanical performance of reinforced concrete (RC) elements reducing both their strength capacity and ductility. Especially in seismic prone areas, the degradation of the cyclic behavior of corroded RC elements is more intense, limiting the service life of structures and leading to premature failures. In the present paper, in order to study the degraded behavior of the embedded (in concrete) steel reinforcement under cyclic loading, laboratory corrosion experiments were performed on embedded steel reinforcing bars. Thereafter, mechanical tests under dynamic loadings with gradually increased deformations were carried out. From the experimental study, hysteretic models of the non-linear behavior of steel bars were extracted in non-corroded and corroded conditions, in the case of both uniform and pitting corrosion. Based on the hysteretic models of steel bars, an analysis of the cyclic response of (non-corroded and corroded...

Research paper thumbnail of Advanced Metallic Materials and Processes

The following main tendencies in the evolution of metal science are described: development of new... more The following main tendencies in the evolution of metal science are described: development of new materials with predetermined mechanical, physical and functional properties as e.g. amorphous materials, ultra-fine-grained (including nanostructured) etc. Advanced resource-saving technologies applied to traditional and new materials as e.g. different schemes of thermomechanical processing, cyclic thermal treatment, cyclic deformation treatment etc. are presented. Application of advanced techniques: laser beam, highenergy electron-beam, plasma and simulation technique are described as well.

Research paper thumbnail of Finite-element simulation of a beam-to-column connection with circle web opening

Proceedings of the ICE - Structures and Buildings, 2012

Connections with pre-cast hollow sections are commonly preferred in recent times because of the c... more Connections with pre-cast hollow sections are commonly preferred in recent times because of the convenience they offer. The present work describes a finite-element model developed to simulate the structural behaviour of beam-to-column joints with hollow sections. In order to verify the model, a simple beam-to-column joint is modelled in a laboratory test; the joint consists of an end-plate welded to a beam and bolted to a column. The validity of the finite-element model is then established by comparing its results with the corresponding experimental tests. Thereafter a parametric study is carried out to investigate the structural behaviour with variations in the pre-cast web opening radius and distance from the connection.

Research paper thumbnail of The design and application of selected techniques for the environmental and energy improvement of urban areas- the case study of Patras, greece

The present study deals with various techniques aiming primarily to improve the environmental and... more The present study deals with various techniques aiming primarily to improve the environmental and microclimatic quality of urban areas, and, secondly, to minimize the energy consumption in the buildings’ sector based mainly on bioclimatic principles and criteria in the same area. The selected techniques, which include the re-use of treated wastewater effluents using the wastewater treatment plan, as well as solar passive heating/cooling techniques, have been applied in a specific urban area located in Patras, a large city of western Greece. The application of the treated wastewater effluents re-use in urban areas is possible through the combined reuse of the treated municipal wastewater effluents indoors for domestic use, as well as for irrigating plants in outdoor spaces. One building of the area was selected as representative, and its thermal behavior was simulated and analyzed primarily in its existing situation, and, furthermore, after using several passive cooling techniques, such as the installation of a green roof system, the use of insulating materials in the external walls and roof, the insertion of an atrium, night ventilation techniques, etc. The obtained results showed that with regards to the cooling load, the application of night ventilation and a green roof system provided the higher energy saving, while with respect to the heating load, the more efficient improvements were the insulation on the building’s external walls and roof.

Research paper thumbnail of The effect of ribs on the mechanical behavior of corroded reinforcing steel bars S500s under low-cycle fatigue

Materials and Structures, 2007

Research paper thumbnail of Tensile properties of corroded embedded steel bars B500c in concrete

International Journal of Structural Integrity, 2013

PurposeThe corrosion of reinforcing steel bars reduces significantly the life and durability of c... more PurposeThe corrosion of reinforcing steel bars reduces significantly the life and durability of concrete structures. This critical concern causes great losses to the economy and industry. The purpose of this paper is to estimate the effects of corrosion on the tensile mechanical properties of embedded steel bars B500c in concrete.Design/methodology/approachThe concept is based on the curve fitting modelling, as well the mathematical correlation of the tensile mechanical properties between corroded bare and corroded embedded steel bars. In order to achieve this, extensive experiments were carried out on both bare (Ø8, 10, 12, 16 and 18 mm) and embedded (Ø8 mm) steel bars B500c, which were subjected to artificially accelerated corrosive conditions in a chloride‐rich atmosphere for several exposure times.FindingsThe research results show that the estimation method is available and effective in simulating the tensile mechanical behaviour of corroded reinforcing steel bars B500c.Original...

Research paper thumbnail of Coastal bridges and the 120 Life Span – the Rio‐Antirio case study

International Journal of Structural Integrity, 2010

PurposeThe purpose of this paper is to shed light on the uncertainties related to durability pred... more PurposeThe purpose of this paper is to shed light on the uncertainties related to durability prediction of coastal bridges.Design/methodology/approachThe paper describes the problems encountered with the Rio‐Antric bridge in Greece.FindingsEven the most accurate models, especially those traditionally employed, fail to provide secure estimates, cases which create serious questions about suggested life spans. Local conditions, large‐scale effects, construction practise, dynamic phenomena, etc. create such a complex web of parameters able to negate even the most conservative estimates. As such, cathodic protection systems should be employed in every coastal structure as a defence measure.Originality/valueThe paper offers a typical example of how far engineering, material science and construction practise has to go to guarantee that any designed life is accurately met.

Research paper thumbnail of The Influence of Corrosion and Cross-Section Diameter on the Mechanical Properties of B500c Steel

Journal of Materials Engineering and Performance, 2008

Research paper thumbnail of The Effect of Shot Blasting Process on Mechanical Properties and Anti-Corrosive Behavior of Steel Reinforcement

Metals, 2022

The need to confront the problem of corrosion resistance of steel reinforcement is an issue of ma... more The need to confront the problem of corrosion resistance of steel reinforcement is an issue of major importance and a perpetual challenge to the structural integrity and reliability in reinforced concrete (RC) structures. The current experimental study presents the results of the combined effect of shot blasting and coating on steel reinforcing bars in respect to their anticorrosive resistance and their mechanical behavior, at various times of exposure to corrosive environment. In the present manuscript, a comparison of different abrasive materials was primarily conducted, via electrochemical measurements (Tafel tests), to estimate the corrosion current (icorr) for each abrasive material. After the indication that corrosion resistance can be modified by shot blasting with corundum, the method of Zn85Al15 coating was chosen to further investigate the combined effect of shot blasting with coating, in terms of percentage mass loss and mechanical behavior of steel reinforcement. The res...

Research paper thumbnail of Characteristic Defects-Corrosion Damage and Mechanical Behavior of Dual Phase Rebar

The demands for constructions with high mechanical performance, located in seismic areas, express... more The demands for constructions with high mechanical performance, located in seismic areas, expressed through EC2 and EC8part3, were importantly satisfied mainly with the use of Tempcore dual phase steel bars. High mechanical performance of dual phase steel comes from the combination of the mechanical properties of each individual phase. However, several times have been reported problems concerning their structural cohesion. In the present study four different technical classes (DP) of reinforcing steel bars were used: B500c, B450c, B400c and B500b. SEM and EDX analyses were used, focusing not only on the internal defects regions of the materials (before and after corrosion), but also on the external areas affected by pitting corrosion. Moreover, in terms of the experimental procedure, mechanical tensile tests were conducted, on both corroded and non corroded reinforcing steel bar specimens and the pertinent results are analyzed. The conclusion from the present study is that both inte...

Research paper thumbnail of Effects of corrosion on low-cycle fatigue (seismic) behaviour of high-strength steel reinforcing bars (Rusteel)

Research paper thumbnail of Seismic resistance prediction of corroded S400 (BSt420) reinforcing bars

International Journal of Structural Integrity

Purpose Structures in seismic areas, during their service lifetime, are subjected to numerous sei... more Purpose 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. Design/methodology/approach 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). Findings At the same time, the present study analyses fatigue factors (ef, a, fSR, ed, ep, R, b) that define their inelastic relation between tension – strain and a prediction model on behavior of both reference...

Research paper thumbnail of Critical parameters affecting mass loss of steel reinforcement

International Journal of Structural Integrity

Purpose The safety of reinforced concrete structures is generally related to the expected service... more Purpose 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. Design/methodology/approach 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. Findings Differential aeration greatly affects the results of corrosion on the material, given that under both high and ...

Research paper thumbnail of Computer-aided approach of parameters influencing concrete service life and field validation

Research paper thumbnail of Seismic assessment of RC column under seismic loads

International Journal of Structural Integrity

PurposeAs it is widely known, corrosion is a major deterioration factor for structures which are ... more PurposeAs 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.Design/methodology/approachIn the present study, two identical reinforced concrete columns were constructed and mechanical tests were organized to simulate s...