The Experts below are selected from a list of 1761 Experts worldwide ranked by ideXlab platform
Yunus Emre Harmanci - One of the best experts on this subject based on the ideXlab platform.
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behaviour of Prestressed cfrp anchorages during and after freeze thaw cycle exposure
Polymers, 2018Co-Authors: Yunus Emre Harmanci, Julien Michels, Eleni ChatziAbstract:The long-term performance of externally-bonded reinForcements (EBR) on reinForced concrete (RC) structures highly depends on the behavior of constituent materials and their interfaces to various environmental loads, such as temperature and humidity exposure. Although significant efforts have been devoted to understanding the effect of such conditions on the anchorage resistance of unstressed EBR, with or without sustained loading, the effect of a released Prestressing has not been thoroughly investigated. For this purpose, a series of experiments has been carried out herein, with concrete blocks strengthened with carbon fiber-reinForced polymer (CFRP) strips, both unstressed, as well as Prestressed using the gradient anchorage. The gradient anchorage is a non-mechanical technique to anchor Prestressed CFRP by exploiting the accelerated curing property of epoxy under higher temperatures and segment-wise Prestress-Force releasing. Subsequently, strengthened blocks are transferred into a chamber for exposure in dry freeze-thaw cycles (FTC). Following FTC exposure, the blocks are tested in a conventional lap-shear test setup to determine their residual anchorage resistance and then compared with reference specimens. Blocks were monitored during FTC by conventional and Fabry–Perot-based fiber optic strain (FOS) sensors and a 3D-digital image correlation (3D-DIC) system during gradient application and lap-shear testing. Results indicate a reduction of residual anchorage resistance, stiffness and deformation capacity of the system after FTC and a change in the failure mode from concrete substrate to epoxy-concrete interface failure. It was further observed that all of these properties experienced a more significant reduction for Prestressed specimens. These findings are presented with a complementary finite element model to shed more light onto the durability of such systems.
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long term residual anchorage resistance of gradient anchorages for Prestressed cfrp strips
Composites Part B-engineering, 2018Co-Authors: Yunus Emre Harmanci, Julien Michels, Christoph Czaderski, Roman Loser, Eleni ChatziAbstract:Abstract This paper presents findings from a series of experimental investigations on the long-term resistance of the gradient anchorage, a purely epoxy-based non-mechanical anchoring technique for Prestressed carbon fiber reinForced polymer (CFRP) strips, after exposure to accelerated ageing conditions. A segment of the complete anchorage solution is simulated by anchoring a Prestressed CFRP strip to a concrete block. A custom-designed clamping system on one end allows for maintaining the Prestress Force constant during exposure to accelerated ageing. Upon such an exposure, the specimens are tested in a conventional lap-shear test setup. Several exposure scenarios and their effect on the residual load carrying capacity are considered, namely the effect of carbonated concrete (CC), freeze-thaw cycles (FTC), as well as their combination. Forces and full-field displacements, the latter by means of a 3D-DIC system, were measured during the Prestress-Force-release and lap-shear tests. Results indicate a higher anchorage resistance for CC compared to the reference specimens. For both groups a debonding in the concrete substrate was observed. Specimens subjected to FTC exposure suffer from a significant reduction in residual anchorage resistance, as well as a shift in failure mode from a concrete substrate dominated to an epoxy/concrete interface failure. The current knowledge on the residual resistance of gradient anchorage has to be adapted accordingly.
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Behaviour of Prestressed CFRP Anchorages during and after Freeze-Thaw Cycle Exposure
MDPI AG, 2018Co-Authors: Yunus Emre Harmanci, Julien Michels, Eleni ChatziAbstract:The long-term performance of externally-bonded reinForcements (EBR) on reinForced concrete (RC) structures highly depends on the behavior of constituent materials and their interfaces to various environmental loads, such as temperature and humidity exposure. Although significant efforts have been devoted to understanding the effect of such conditions on the anchorage resistance of unstressed EBR, with or without sustained loading, the effect of a released Prestressing has not been thoroughly investigated. For this purpose, a series of experiments has been carried out herein, with concrete blocks strengthened with carbon fiber-reinForced polymer (CFRP) strips, both unstressed, as well as Prestressed using the gradient anchorage. The gradient anchorage is a non-mechanical technique to anchor Prestressed CFRP by exploiting the accelerated curing property of epoxy under higher temperatures and segment-wise Prestress-Force releasing. Subsequently, strengthened blocks are transferred into a chamber for exposure in dry freeze-thaw cycles (FTC). Following FTC exposure, the blocks are tested in a conventional lap-shear test setup to determine their residual anchorage resistance and then compared with reference specimens. Blocks were monitored during FTC by conventional and Fabry–Pérot-based fiber optic strain (FOS) sensors and a 3D-digital image correlation (3D-DIC) system during gradient application and lap-shear testing. Results indicate a reduction of residual anchorage resistance, stiffness and deformation capacity of the system after FTC and a change in the failure mode from concrete substrate to epoxy-concrete interface failure. It was further observed that all of these properties experienced a more significant reduction for Prestressed specimens. These findings are presented with a complementary finite element model to shed more light onto the durability of such systems
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flexural strengthening of rc slabs with Prestressed cfrp strips using different anchorage systems
Polymers, 2015Co-Authors: Jose Senacruz, Yunus Emre Harmanci, Julien Michels, Luis Luciano Gouveia CorreiaAbstract:Externally Bonded ReinForcement (EBR) technique has been widely used for flexural strengthening of concrete structures by using carbon fiber-reinForced polymers (CFRP). EBR technique offers several structural advantages when the CFRP material is Prestressed. This paper presents an experimental and numerical study on reinForced (RC) slabs strengthened in flexure with Prestressed CFRP strips as a structural strengthening system. The strips are applied as an externally bonded reinForcement (EBR) and anchored with either a mechanical or a gradient anchorage. The former foresees metallic anchorage plates fixed to the concrete substrate, while the latter is based on an accelerated epoxy resin curing followed by a segment-wise Prestress Force decrease at the strip ends. Both anchorage systems, in combination with different CFRP strip geometries, were subjected to static loading tests. It could be demonstrated that the composite strip's performance is better exploited when Prestressing is used, with slightly higher overall load carrying capacities for mechanical anchorages than for the gradient anchorage. The performed investigations by means of a cross-section analysis supported the experimental observation that in case a mechanical anchorage is used, progressive strip debonding changes the fully bonded configuration to an unbonded end-anchored system. The inclusion of defined debonding criteria for both the anchorage zones and free length between the anchorage regions allowed to precisely capture the ultimate loading Forces.
Younghwan Park - One of the best experts on this subject based on the ideXlab platform.
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Estimation of Tendon Force Distribution in Prestressed Concrete Girders Using Smart Strand
MDPI AG, 2017Co-Authors: Keunhee Cho, Jeong-rae Cho, Sung Tae Kim, Younghwan ParkAbstract:The recently developed smart strand offers the possibility of measuring the Prestress Force of the tendon from jacking and all along its service life. In the present study, a method estimating the Force distribution in all the tendons of a Prestressed concrete (PSC) girder installed with one smart strand is proposed. The Force distribution in the Prestressed tendons is formulated by the friction and the anchorage slip, and is obtained through an optimization process with respect to the compatibility conditions and equilibrium of the Forces in the section of the PSC girder. The validation of the proposed method through a numerical example and experiment shows that it can be used to estimate the Force developed in the tendon
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estimation of Prestress Force distribution in multi strand system of Prestressed concrete structures using field data measured by electromagnetic sensor
Sensors, 2016Co-Authors: Keunhee Cho, Jeong-rae Cho, Sung Yong Park, Sung Tae Kim, Youngjin Kim, Younghwan ParkAbstract:The recently developed smart strand can be used to measure the Prestress Force in the Prestressed concrete (PSC) structure from the construction stage to the in-service stage. The higher cost of the smart strand compared to the conventional strand renders it unaffordable to replace all the strands by smart strands, and results in the application of only a limited number of smart strands in the PSC structure. However, the Prestress Forces developed in the strands of the multi-strand system frequently adopted in PSC structures differ from each other, which means that the Prestress Force in the multi-strand system cannot be obtained by simple proportional scaling using the measurement of the smart strand. Therefore, this study examines the Prestress Force distribution in the multi-strand system to find the correlation between the Prestress Force measured by the smart strand and the Prestress Force distribution in the multi-strand system. To that goal, the Prestress Force distribution was measured using electromagnetic sensors for various factors of the multi-strand system adopted on site in the fabrication of actual PSC girders. The results verified the possibility to assume normal distribution for the Prestress Force distribution per anchor head, and a method computing the mean and standard deviation defining the normal distribution is proposed. This paper presents a meaningful finding by proposing an estimation method of the Prestress Force based upon field-measured data of the Prestress Force distribution in the multi-strand system of actual PSC structures.
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estimation of Prestress Force distribution in the multi strand system of Prestressed concrete structures
Sensors, 2015Co-Authors: Keunhee Cho, Jeong-rae Cho, Sung Yong Park, Sung Tae Kim, Younghwan ParkAbstract:Prestressed concrete (PSC) is one of the most reliable, durable and widely used construction materials, which overcomes the weakness of concrete in tension by the introduction of a Prestress Force. Smart strands enabling measurement of the Prestress Force have recently been developed to maintain PSC structures throughout their lifetime. However, the smart strand cannot give a representative indication of the whole Prestress Force when used in multi-strand systems since each strand sustains a different Prestress Force. In this paper, the actual distribution of the Prestress Force in a multi-strand system is examined using elastomagnetic (EM) sensors to develop a method for tracking representative indicators of the Prestress Force using smart strands.
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A sensor-type PC strand with an embedded FBG sensor for monitoring Prestress Forces
Sensors (Switzerland), 2015Co-Authors: Sung Tae Kim, Keunhee Cho, Younghwan Park, Sung Yong Park, Jeong-rae ChoAbstract:Prestressed Concrete Wire and Strand (PC) strands are the most used materials to introduce Prestress in a Pre-Stressed Concrete (PSC) structure. However, it is difficult to evaluate the final Prestress Force of the PC strand after Prestressing or its residual Prestress Force after completion of the structure on site. This impossibility to assess eventual loss of Prestress of the PC strand has resulted in a number of serious accidents and even in the collapse of several structures. This situation stresses the necessity to maintain the Prestress Force residual or after Prestressing for the evaluation of the health of the concrete structure throughout its lifespan. Recently, several researchers have studied methods enabling one to verify the Prestress Force by inserting an optical fiber sensor inside the strand but failed to provide simple techniques for the fabrication of these devices to fulfill measurement performance from the design Prestress to failure. Moreover, these methods require the additional installation of electrical resistance strain gages, displacement sensors and load cells on the outer surface of the structure for long-term precise measurement. This paper proposes a method enabling one to evaluate precisely and effectively the Prestress Force of the PC strand and intends to verify the applicability of the proposed method on actual concrete structures. To that end, an innovative PC strand is developed by embedding a Fiber Bragg Grating (FBG) sensor in the core wire of the PC strand so as to enable short term as well as long term monitoring. The measurement performance of the developed strand is then evaluated experimentally and the reliability of the monitoring data is assessed.
Julien Michels - One of the best experts on this subject based on the ideXlab platform.
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behaviour of Prestressed cfrp anchorages during and after freeze thaw cycle exposure
Polymers, 2018Co-Authors: Yunus Emre Harmanci, Julien Michels, Eleni ChatziAbstract:The long-term performance of externally-bonded reinForcements (EBR) on reinForced concrete (RC) structures highly depends on the behavior of constituent materials and their interfaces to various environmental loads, such as temperature and humidity exposure. Although significant efforts have been devoted to understanding the effect of such conditions on the anchorage resistance of unstressed EBR, with or without sustained loading, the effect of a released Prestressing has not been thoroughly investigated. For this purpose, a series of experiments has been carried out herein, with concrete blocks strengthened with carbon fiber-reinForced polymer (CFRP) strips, both unstressed, as well as Prestressed using the gradient anchorage. The gradient anchorage is a non-mechanical technique to anchor Prestressed CFRP by exploiting the accelerated curing property of epoxy under higher temperatures and segment-wise Prestress-Force releasing. Subsequently, strengthened blocks are transferred into a chamber for exposure in dry freeze-thaw cycles (FTC). Following FTC exposure, the blocks are tested in a conventional lap-shear test setup to determine their residual anchorage resistance and then compared with reference specimens. Blocks were monitored during FTC by conventional and Fabry–Perot-based fiber optic strain (FOS) sensors and a 3D-digital image correlation (3D-DIC) system during gradient application and lap-shear testing. Results indicate a reduction of residual anchorage resistance, stiffness and deformation capacity of the system after FTC and a change in the failure mode from concrete substrate to epoxy-concrete interface failure. It was further observed that all of these properties experienced a more significant reduction for Prestressed specimens. These findings are presented with a complementary finite element model to shed more light onto the durability of such systems.
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long term residual anchorage resistance of gradient anchorages for Prestressed cfrp strips
Composites Part B-engineering, 2018Co-Authors: Yunus Emre Harmanci, Julien Michels, Christoph Czaderski, Roman Loser, Eleni ChatziAbstract:Abstract This paper presents findings from a series of experimental investigations on the long-term resistance of the gradient anchorage, a purely epoxy-based non-mechanical anchoring technique for Prestressed carbon fiber reinForced polymer (CFRP) strips, after exposure to accelerated ageing conditions. A segment of the complete anchorage solution is simulated by anchoring a Prestressed CFRP strip to a concrete block. A custom-designed clamping system on one end allows for maintaining the Prestress Force constant during exposure to accelerated ageing. Upon such an exposure, the specimens are tested in a conventional lap-shear test setup. Several exposure scenarios and their effect on the residual load carrying capacity are considered, namely the effect of carbonated concrete (CC), freeze-thaw cycles (FTC), as well as their combination. Forces and full-field displacements, the latter by means of a 3D-DIC system, were measured during the Prestress-Force-release and lap-shear tests. Results indicate a higher anchorage resistance for CC compared to the reference specimens. For both groups a debonding in the concrete substrate was observed. Specimens subjected to FTC exposure suffer from a significant reduction in residual anchorage resistance, as well as a shift in failure mode from a concrete substrate dominated to an epoxy/concrete interface failure. The current knowledge on the residual resistance of gradient anchorage has to be adapted accordingly.
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Behaviour of Prestressed CFRP Anchorages during and after Freeze-Thaw Cycle Exposure
MDPI AG, 2018Co-Authors: Yunus Emre Harmanci, Julien Michels, Eleni ChatziAbstract:The long-term performance of externally-bonded reinForcements (EBR) on reinForced concrete (RC) structures highly depends on the behavior of constituent materials and their interfaces to various environmental loads, such as temperature and humidity exposure. Although significant efforts have been devoted to understanding the effect of such conditions on the anchorage resistance of unstressed EBR, with or without sustained loading, the effect of a released Prestressing has not been thoroughly investigated. For this purpose, a series of experiments has been carried out herein, with concrete blocks strengthened with carbon fiber-reinForced polymer (CFRP) strips, both unstressed, as well as Prestressed using the gradient anchorage. The gradient anchorage is a non-mechanical technique to anchor Prestressed CFRP by exploiting the accelerated curing property of epoxy under higher temperatures and segment-wise Prestress-Force releasing. Subsequently, strengthened blocks are transferred into a chamber for exposure in dry freeze-thaw cycles (FTC). Following FTC exposure, the blocks are tested in a conventional lap-shear test setup to determine their residual anchorage resistance and then compared with reference specimens. Blocks were monitored during FTC by conventional and Fabry–Pérot-based fiber optic strain (FOS) sensors and a 3D-digital image correlation (3D-DIC) system during gradient application and lap-shear testing. Results indicate a reduction of residual anchorage resistance, stiffness and deformation capacity of the system after FTC and a change in the failure mode from concrete substrate to epoxy-concrete interface failure. It was further observed that all of these properties experienced a more significant reduction for Prestressed specimens. These findings are presented with a complementary finite element model to shed more light onto the durability of such systems
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Prestress Force release tests at elevated temperatures gradient anchorage stability for Prestressed eb cfrp strips
Composite Structures, 2016Co-Authors: Juan Gallego, Christoph Czaderski, Julien MichelsAbstract:Abstract During the last decades, traffic loads by heavy vehicles have increased due to requirements of the current society and this fact has to be considered when the state of existing bridges is evaluated. Many concrete structures, for instance lateral cantilevers of highway boxgirder bridges, can be strengthened on the upper side with Externally Bonded (EB) Carbon Fiber ReinForced Polymer (CFRP) strips in order to increase their load-bearing capacity in flexure. These additional reinForcements can be applied as an unstressed or Prestressed system. The main objective of this paper is to analyze the influence of elevated temperatures for instance due to the application of warm mastic asphalt on the bond between the concrete substrate, the epoxy resin layer, and the externally Prestressed bonded CFRP strip. Background of the study is a non-mechanical anchorage system for Prestressed composite strips known as the gradient anchorage. A literature review collecting the most important experimental works performed in this field together with an own experimental investigation performed at Empa is presented in this paper. Besides, an analytical linear elastic model has been proposed to study the behavior of such Prestressed systems after the releasing stage.
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flexural strengthening of rc slabs with Prestressed cfrp strips using different anchorage systems
Polymers, 2015Co-Authors: Jose Senacruz, Yunus Emre Harmanci, Julien Michels, Luis Luciano Gouveia CorreiaAbstract:Externally Bonded ReinForcement (EBR) technique has been widely used for flexural strengthening of concrete structures by using carbon fiber-reinForced polymers (CFRP). EBR technique offers several structural advantages when the CFRP material is Prestressed. This paper presents an experimental and numerical study on reinForced (RC) slabs strengthened in flexure with Prestressed CFRP strips as a structural strengthening system. The strips are applied as an externally bonded reinForcement (EBR) and anchored with either a mechanical or a gradient anchorage. The former foresees metallic anchorage plates fixed to the concrete substrate, while the latter is based on an accelerated epoxy resin curing followed by a segment-wise Prestress Force decrease at the strip ends. Both anchorage systems, in combination with different CFRP strip geometries, were subjected to static loading tests. It could be demonstrated that the composite strip's performance is better exploited when Prestressing is used, with slightly higher overall load carrying capacities for mechanical anchorages than for the gradient anchorage. The performed investigations by means of a cross-section analysis supported the experimental observation that in case a mechanical anchorage is used, progressive strip debonding changes the fully bonded configuration to an unbonded end-anchored system. The inclusion of defined debonding criteria for both the anchorage zones and free length between the anchorage regions allowed to precisely capture the ultimate loading Forces.
Eleni Chatzi - One of the best experts on this subject based on the ideXlab platform.
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behaviour of Prestressed cfrp anchorages during and after freeze thaw cycle exposure
Polymers, 2018Co-Authors: Yunus Emre Harmanci, Julien Michels, Eleni ChatziAbstract:The long-term performance of externally-bonded reinForcements (EBR) on reinForced concrete (RC) structures highly depends on the behavior of constituent materials and their interfaces to various environmental loads, such as temperature and humidity exposure. Although significant efforts have been devoted to understanding the effect of such conditions on the anchorage resistance of unstressed EBR, with or without sustained loading, the effect of a released Prestressing has not been thoroughly investigated. For this purpose, a series of experiments has been carried out herein, with concrete blocks strengthened with carbon fiber-reinForced polymer (CFRP) strips, both unstressed, as well as Prestressed using the gradient anchorage. The gradient anchorage is a non-mechanical technique to anchor Prestressed CFRP by exploiting the accelerated curing property of epoxy under higher temperatures and segment-wise Prestress-Force releasing. Subsequently, strengthened blocks are transferred into a chamber for exposure in dry freeze-thaw cycles (FTC). Following FTC exposure, the blocks are tested in a conventional lap-shear test setup to determine their residual anchorage resistance and then compared with reference specimens. Blocks were monitored during FTC by conventional and Fabry–Perot-based fiber optic strain (FOS) sensors and a 3D-digital image correlation (3D-DIC) system during gradient application and lap-shear testing. Results indicate a reduction of residual anchorage resistance, stiffness and deformation capacity of the system after FTC and a change in the failure mode from concrete substrate to epoxy-concrete interface failure. It was further observed that all of these properties experienced a more significant reduction for Prestressed specimens. These findings are presented with a complementary finite element model to shed more light onto the durability of such systems.
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long term residual anchorage resistance of gradient anchorages for Prestressed cfrp strips
Composites Part B-engineering, 2018Co-Authors: Yunus Emre Harmanci, Julien Michels, Christoph Czaderski, Roman Loser, Eleni ChatziAbstract:Abstract This paper presents findings from a series of experimental investigations on the long-term resistance of the gradient anchorage, a purely epoxy-based non-mechanical anchoring technique for Prestressed carbon fiber reinForced polymer (CFRP) strips, after exposure to accelerated ageing conditions. A segment of the complete anchorage solution is simulated by anchoring a Prestressed CFRP strip to a concrete block. A custom-designed clamping system on one end allows for maintaining the Prestress Force constant during exposure to accelerated ageing. Upon such an exposure, the specimens are tested in a conventional lap-shear test setup. Several exposure scenarios and their effect on the residual load carrying capacity are considered, namely the effect of carbonated concrete (CC), freeze-thaw cycles (FTC), as well as their combination. Forces and full-field displacements, the latter by means of a 3D-DIC system, were measured during the Prestress-Force-release and lap-shear tests. Results indicate a higher anchorage resistance for CC compared to the reference specimens. For both groups a debonding in the concrete substrate was observed. Specimens subjected to FTC exposure suffer from a significant reduction in residual anchorage resistance, as well as a shift in failure mode from a concrete substrate dominated to an epoxy/concrete interface failure. The current knowledge on the residual resistance of gradient anchorage has to be adapted accordingly.
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Behaviour of Prestressed CFRP Anchorages during and after Freeze-Thaw Cycle Exposure
MDPI AG, 2018Co-Authors: Yunus Emre Harmanci, Julien Michels, Eleni ChatziAbstract:The long-term performance of externally-bonded reinForcements (EBR) on reinForced concrete (RC) structures highly depends on the behavior of constituent materials and their interfaces to various environmental loads, such as temperature and humidity exposure. Although significant efforts have been devoted to understanding the effect of such conditions on the anchorage resistance of unstressed EBR, with or without sustained loading, the effect of a released Prestressing has not been thoroughly investigated. For this purpose, a series of experiments has been carried out herein, with concrete blocks strengthened with carbon fiber-reinForced polymer (CFRP) strips, both unstressed, as well as Prestressed using the gradient anchorage. The gradient anchorage is a non-mechanical technique to anchor Prestressed CFRP by exploiting the accelerated curing property of epoxy under higher temperatures and segment-wise Prestress-Force releasing. Subsequently, strengthened blocks are transferred into a chamber for exposure in dry freeze-thaw cycles (FTC). Following FTC exposure, the blocks are tested in a conventional lap-shear test setup to determine their residual anchorage resistance and then compared with reference specimens. Blocks were monitored during FTC by conventional and Fabry–Pérot-based fiber optic strain (FOS) sensors and a 3D-digital image correlation (3D-DIC) system during gradient application and lap-shear testing. Results indicate a reduction of residual anchorage resistance, stiffness and deformation capacity of the system after FTC and a change in the failure mode from concrete substrate to epoxy-concrete interface failure. It was further observed that all of these properties experienced a more significant reduction for Prestressed specimens. These findings are presented with a complementary finite element model to shed more light onto the durability of such systems
Keunhee Cho - One of the best experts on this subject based on the ideXlab platform.
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Estimation of Tendon Force Distribution in Prestressed Concrete Girders Using Smart Strand
MDPI AG, 2017Co-Authors: Keunhee Cho, Jeong-rae Cho, Sung Tae Kim, Younghwan ParkAbstract:The recently developed smart strand offers the possibility of measuring the Prestress Force of the tendon from jacking and all along its service life. In the present study, a method estimating the Force distribution in all the tendons of a Prestressed concrete (PSC) girder installed with one smart strand is proposed. The Force distribution in the Prestressed tendons is formulated by the friction and the anchorage slip, and is obtained through an optimization process with respect to the compatibility conditions and equilibrium of the Forces in the section of the PSC girder. The validation of the proposed method through a numerical example and experiment shows that it can be used to estimate the Force developed in the tendon
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estimation of Prestress Force distribution in multi strand system of Prestressed concrete structures using field data measured by electromagnetic sensor
Sensors, 2016Co-Authors: Keunhee Cho, Jeong-rae Cho, Sung Yong Park, Sung Tae Kim, Youngjin Kim, Younghwan ParkAbstract:The recently developed smart strand can be used to measure the Prestress Force in the Prestressed concrete (PSC) structure from the construction stage to the in-service stage. The higher cost of the smart strand compared to the conventional strand renders it unaffordable to replace all the strands by smart strands, and results in the application of only a limited number of smart strands in the PSC structure. However, the Prestress Forces developed in the strands of the multi-strand system frequently adopted in PSC structures differ from each other, which means that the Prestress Force in the multi-strand system cannot be obtained by simple proportional scaling using the measurement of the smart strand. Therefore, this study examines the Prestress Force distribution in the multi-strand system to find the correlation between the Prestress Force measured by the smart strand and the Prestress Force distribution in the multi-strand system. To that goal, the Prestress Force distribution was measured using electromagnetic sensors for various factors of the multi-strand system adopted on site in the fabrication of actual PSC girders. The results verified the possibility to assume normal distribution for the Prestress Force distribution per anchor head, and a method computing the mean and standard deviation defining the normal distribution is proposed. This paper presents a meaningful finding by proposing an estimation method of the Prestress Force based upon field-measured data of the Prestress Force distribution in the multi-strand system of actual PSC structures.
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estimation of Prestress Force distribution in the multi strand system of Prestressed concrete structures
Sensors, 2015Co-Authors: Keunhee Cho, Jeong-rae Cho, Sung Yong Park, Sung Tae Kim, Younghwan ParkAbstract:Prestressed concrete (PSC) is one of the most reliable, durable and widely used construction materials, which overcomes the weakness of concrete in tension by the introduction of a Prestress Force. Smart strands enabling measurement of the Prestress Force have recently been developed to maintain PSC structures throughout their lifetime. However, the smart strand cannot give a representative indication of the whole Prestress Force when used in multi-strand systems since each strand sustains a different Prestress Force. In this paper, the actual distribution of the Prestress Force in a multi-strand system is examined using elastomagnetic (EM) sensors to develop a method for tracking representative indicators of the Prestress Force using smart strands.
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A sensor-type PC strand with an embedded FBG sensor for monitoring Prestress Forces
Sensors (Switzerland), 2015Co-Authors: Sung Tae Kim, Keunhee Cho, Younghwan Park, Sung Yong Park, Jeong-rae ChoAbstract:Prestressed Concrete Wire and Strand (PC) strands are the most used materials to introduce Prestress in a Pre-Stressed Concrete (PSC) structure. However, it is difficult to evaluate the final Prestress Force of the PC strand after Prestressing or its residual Prestress Force after completion of the structure on site. This impossibility to assess eventual loss of Prestress of the PC strand has resulted in a number of serious accidents and even in the collapse of several structures. This situation stresses the necessity to maintain the Prestress Force residual or after Prestressing for the evaluation of the health of the concrete structure throughout its lifespan. Recently, several researchers have studied methods enabling one to verify the Prestress Force by inserting an optical fiber sensor inside the strand but failed to provide simple techniques for the fabrication of these devices to fulfill measurement performance from the design Prestress to failure. Moreover, these methods require the additional installation of electrical resistance strain gages, displacement sensors and load cells on the outer surface of the structure for long-term precise measurement. This paper proposes a method enabling one to evaluate precisely and effectively the Prestress Force of the PC strand and intends to verify the applicability of the proposed method on actual concrete structures. To that end, an innovative PC strand is developed by embedding a Fiber Bragg Grating (FBG) sensor in the core wire of the PC strand so as to enable short term as well as long term monitoring. The measurement performance of the developed strand is then evaluated experimentally and the reliability of the monitoring data is assessed.