Reinforced concrete (RC) arch bridges hold a strategic role in transportation networks. The definition of simplified assessment procedures for their vulnerability at large scale is of fundamental importance for a smart evaluation and maintenance. The role of these infrastructures is crucial in areas where the seismic risk is very high. For instance, in Italy, RC arch bridges, mainly in the form of vaulted slabs, are very common as railway bridges, dating back to the 60’s. Almost all of these bridges were designed in agreement to outdated design approaches based on masonry experience, without taking into account peculiarities of reinforced concrete. The key innovative aspect of proposed method is the possibility, with few parameters and reduced knowledge level, to define macro classes of bridges based on geometrical and material parameters that allow to estimate immediately the vulnerability of the most risky bridges. Based on these results it is possible to provide multilevel guidelines that can be used by administrators for the assessment of bridge vulnerability at bridge stock level (a basis for prioritizing the design of potential retrofit or strengthening interventions). Also in a post-emergency scenario this study allows to quickly estimate potential damage of arch bridge structures given main earthquake parameters to evaluate the operational state of the network and address early rescue and post-event operations.
{"title":"Evaluation of RC-arch Bridges and Main Parameters in Performance Assessment","authors":"G. Lignola, F. Porto, A. Prota, G. Manfredi","doi":"10.14359/51687083","DOIUrl":"https://doi.org/10.14359/51687083","url":null,"abstract":"Reinforced concrete (RC) arch bridges hold a strategic role in transportation networks. The definition of simplified assessment procedures for their vulnerability at large scale is of fundamental importance for a smart evaluation and maintenance. The role of these infrastructures is crucial in areas where the seismic risk is very high. For instance, in Italy, RC arch bridges, mainly in the form of vaulted slabs, are very common as railway bridges, dating back to the 60’s. Almost all of these bridges were designed in agreement to outdated design approaches based on masonry experience, without taking into account peculiarities of reinforced concrete. The key innovative aspect of proposed method is the possibility, with few parameters and reduced knowledge level, to define macro classes of bridges based on geometrical and material parameters that allow to estimate immediately the vulnerability of the most risky bridges. Based on these results it is possible to provide multilevel guidelines that can be used by administrators for the assessment of bridge vulnerability at bridge stock level (a basis for prioritizing the design of potential retrofit or strengthening interventions). Also in a post-emergency scenario this study allows to quickly estimate potential damage of arch bridge structures given main earthquake parameters to evaluate the operational state of the network and address early rescue and post-event operations.","PeriodicalId":191674,"journal":{"name":"\"SP-298: Advanced Materials and Sensors Towards Smart Concrete Bridges: Concept, Performance, Evaluation, and Repair\"","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125903805","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
F. Ghrib, Amr El Ragaby, B. Boufama, Li Li, Sara Memar
Recently, several infrastructure failures have highlighted the importance of structural inspection and increase awareness of the need for efficient structural health monitoring and damage detection techniques. The development of non-contact monitoring technique that is efficient and requires little preparation to implement would greatly benefit the civil engineering and construction community. Close range photogrammetry is a noncontact measurement technique that can be used to monitor a specimen’s deformation as it undergoes loading. This research investigates utilising an image matching algorithm to measure the deflection profile of concrete beams. The present paper illustrates the efficiency of the image matching algorithm (digital image correlation) in measuring the full deflection profile along a concrete beam. Five reinforced concrete beams, 2400 mm (94.48 in.) long, 250 mm (10 in.) deep and 150 mm (6 in.) wide were tested under 4-point bending. Three different surface treatment configurations for the test specimen’s side faces as well as two types of longitudinal flexural reinforcement, steel and carbon fiber reinforced polymer (CFRP), were used. Two Linear Variable Differential Transformers (LVDTs) were used to measure the deflection to validate the proposed digital image correlation algorithm. It was concluded that the image matching algorithm can be used efficiently to measure deflection profile of a flexural member. Despite all existing health monitoring techniques, image matching has the potential to reconstruct the deflection profile along the whole member length to evaluate its current structural behaviour.
{"title":"A Novel Technique for Displacement Measurements in RC Beams using Digital Image Correlation","authors":"F. Ghrib, Amr El Ragaby, B. Boufama, Li Li, Sara Memar","doi":"10.14359/51687086","DOIUrl":"https://doi.org/10.14359/51687086","url":null,"abstract":"Recently, several infrastructure failures have highlighted the importance of structural inspection and increase awareness of the need for efficient structural health monitoring and damage detection techniques. The development of non-contact monitoring technique that is efficient and requires little preparation to implement would greatly benefit the civil engineering and construction community. Close range photogrammetry is a noncontact measurement technique that can be used to monitor a specimen’s deformation as it undergoes loading. This research investigates utilising an image matching algorithm to measure the deflection profile of concrete beams. The present paper illustrates the efficiency of the image matching algorithm (digital image correlation) in measuring the full deflection profile along a concrete beam. Five reinforced concrete beams, 2400 mm (94.48 in.) long, 250 mm (10 in.) deep and 150 mm (6 in.) wide were tested under 4-point bending. Three different surface treatment configurations for the test specimen’s side faces as well as two types of longitudinal flexural reinforcement, steel and carbon fiber reinforced polymer (CFRP), were used. Two Linear Variable Differential Transformers (LVDTs) were used to measure the deflection to validate the proposed digital image correlation algorithm. It was concluded that the image matching algorithm can be used efficiently to measure deflection profile of a flexural member. Despite all existing health monitoring techniques, image matching has the potential to reconstruct the deflection profile along the whole member length to evaluate its current structural behaviour.","PeriodicalId":191674,"journal":{"name":"\"SP-298: Advanced Materials and Sensors Towards Smart Concrete Bridges: Concept, Performance, Evaluation, and Repair\"","volume":"42 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124959157","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Engineers currently lack the ability to non-destructively measure through-thickness elastic and plastic strain of steel reinforcement in reinforced concrete structures. This capability would be of considerable use in assessing structures damaged by extreme events, corrosion, or slower-acting expansive reactions in concrete such as alkali-silica reaction (ASR), delayed ettringite formation (DEF) and sulfate attack. New non-contact electromagnetic sensors have been demonstrated for providing this capability on bridge girder sections. When steel is strained, the electronic properties of the metal are altered and there is a measurable change in the electromagnetic response of the metal. These changes in material properties can be used to measure strain in the steel reinforcement from outside the concrete. This paper describes the results of preliminary tests involving samples of exposed rebar, concrete-encased rebar, and a full-scale reinforced concrete beam. The rebar specimens were placed in tension while typical strain gauges and the non-contact electromagnetic stress measurements were simultaneously performed. The specimens were then loaded well in excess of the yield point, to ensure both elastic and plastic straining occurred. Electromagnetic sensors were positioned to monitor changes in strain in a stirrup and a longitudinal reinforcing bar during a flexural test of a full-scale beam that had previously undergone significant expansion from ASR and DEF. The results of these early tests indicate the eStress system can provide valuable insight into the strains in bridges and other structures, thus providing an improved method for maintenance and repair.
{"title":"Non-Contact Strain Measurements of Steel Reinforcement in Concrete Structures","authors":"A. Lasseigne, Eric R. Giannini, J. Jackson","doi":"10.14359/51687082","DOIUrl":"https://doi.org/10.14359/51687082","url":null,"abstract":"Engineers currently lack the ability to non-destructively measure through-thickness elastic and plastic strain of steel reinforcement in reinforced concrete structures. This capability would be of considerable use in assessing structures damaged by extreme events, corrosion, or slower-acting expansive reactions in concrete such as alkali-silica reaction (ASR), delayed ettringite formation (DEF) and sulfate attack. New non-contact electromagnetic sensors have been demonstrated for providing this capability on bridge girder sections. When steel is strained, the electronic properties of the metal are altered and there is a measurable change in the electromagnetic response of the metal. These changes in material properties can be used to measure strain in the steel reinforcement from outside the concrete. This paper describes the results of preliminary tests involving samples of exposed rebar, concrete-encased rebar, and a full-scale reinforced concrete beam. The rebar specimens were placed in tension while typical strain gauges and the non-contact electromagnetic stress measurements were simultaneously performed. The specimens were then loaded well in excess of the yield point, to ensure both elastic and plastic straining occurred. Electromagnetic sensors were positioned to monitor changes in strain in a stirrup and a longitudinal reinforcing bar during a flexural test of a full-scale beam that had previously undergone significant expansion from ASR and DEF. The results of these early tests indicate the eStress system can provide valuable insight into the strains in bridges and other structures, thus providing an improved method for maintenance and repair.","PeriodicalId":191674,"journal":{"name":"\"SP-298: Advanced Materials and Sensors Towards Smart Concrete Bridges: Concept, Performance, Evaluation, and Repair\"","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130582234","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper presents the performance of constructed bridge decks in a cold region with the aid of an extensive database acquired in North Dakota. A total of 1,328 decks are sampled from a 15 year inspection period. These data are statistically characterized and probabilistically analyzed. The importance of timely technical action for enhancing the condition rating of the decks is discussed. The stochastic response of the existing decks is effectively represented by Gaussian probability distributions, regardless of inspection years. The performance of the decks tends to converge to a certain state with time. The state-transition of the in-situ decks is identified through the global health index proposed. A new nondestructive testing method is developed to diagnose the physical damage of concrete based on near-field microwave.
{"title":"Performance of Bridge Decks in a Cold Region and a High-fidelity Sensing System for Damage Detection","authors":"Shahlaa Al Wakeel, Y. J. Kim, Y. Deng","doi":"10.14359/51687087","DOIUrl":"https://doi.org/10.14359/51687087","url":null,"abstract":"This paper presents the performance of constructed bridge decks in a cold region with the aid of an extensive database acquired in North Dakota. A total of 1,328 decks are sampled from a 15 year inspection period. These data are statistically characterized and probabilistically analyzed. The importance of timely technical action for enhancing the condition rating of the decks is discussed. The stochastic response of the existing decks is effectively represented by Gaussian probability distributions, regardless of inspection years. The performance of the decks tends to converge to a certain state with time. The state-transition of the in-situ decks is identified through the global health index proposed. A new nondestructive testing method is developed to diagnose the physical damage of concrete based on near-field microwave.","PeriodicalId":191674,"journal":{"name":"\"SP-298: Advanced Materials and Sensors Towards Smart Concrete Bridges: Concept, Performance, Evaluation, and Repair\"","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133704616","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper presents an initial experimental result concerning the behavior of near-surface mounted (NSM) carbon fiber reinforced polymer (CFRP) strips embedded in a concrete substrate at elevated temperatures. Thermal stresses varying from 25°C [77°F] to 200°C [392°F] are applied for three hours. The experimental program is comprised of 48 CFRP-concrete specimens bonded with an ordinary or high-temperature epoxy adhesive and their comparative performance is of interest in the present investigation. Emphasis is placed on the residual capacity of the conditioned NSM CFRP-concrete interface and corresponding failure mode. Test results show that the interfacial strength of the specimens bonded with the ordinary epoxy is maintained until 75°C [167°F] is reached, while the strength noticeably decreases with an increasing temperature above this limit. The specimens with the high temperature epoxy preserve interfacial capacity up to 200°C [392°F] despite a trend of strength-decrease being observed. The failure of the test specimens is brittle irrespective of adhesive type. Interfacial damage is localized along the bond-line with the presence of hairline cracks that further develop when interfacial failure is imminent.
{"title":"An Experimental Investigation into the Residual Bond of NSM Composite Strips for Concrete at Elevated Temperatures","authors":"A. R. Namrou, Y. J. Kim","doi":"10.14359/51687089","DOIUrl":"https://doi.org/10.14359/51687089","url":null,"abstract":"This paper presents an initial experimental result concerning the behavior of near-surface mounted (NSM) carbon fiber reinforced polymer (CFRP) strips embedded in a concrete substrate at elevated temperatures. Thermal stresses varying from 25°C [77°F] to 200°C [392°F] are applied for three hours. The experimental program is comprised of 48 CFRP-concrete specimens bonded with an ordinary or high-temperature epoxy adhesive and their comparative performance is of interest in the present investigation. Emphasis is placed on the residual capacity of the conditioned NSM CFRP-concrete interface and corresponding failure mode. Test results show that the interfacial strength of the specimens bonded with the ordinary epoxy is maintained until 75°C [167°F] is reached, while the strength noticeably decreases with an increasing temperature above this limit. The specimens with the high temperature epoxy preserve interfacial capacity up to 200°C [392°F] despite a trend of strength-decrease being observed. The failure of the test specimens is brittle irrespective of adhesive type. Interfacial damage is localized along the bond-line with the presence of hairline cracks that further develop when interfacial failure is imminent.","PeriodicalId":191674,"journal":{"name":"\"SP-298: Advanced Materials and Sensors Towards Smart Concrete Bridges: Concept, Performance, Evaluation, and Repair\"","volume":"73 4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134098231","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
H. Rasheed, A. Wuertz, A. Traplsi, H. Melhem, T. Alkhrdaji
The technology of fiber-reinforced polymer (FRP) strengthening has matured to a great extent. However, there is always room for performance improvements. In this study, external bonding of glass-fiber reinforced polymer (GFRP) and near surface mounting of regular steel bars is combined to improve the behavior, delay the failure, and enhance the economy of the strengthening. E-Glass FRP is selected due to its inexpensive cost and non-conductive properties to shield the NSM steel bars from corrosion. On the other hand, the use of NSM bars gives redundancy against vandalism and environmental deterioration of the GFRP. An experimental program is conducted in which five rectangular cross-section beams are designed and built. The first beam is tested as a control beam failing at about 12 kips (53.4 kN). The second beam is strengthened using 5 layers of carbon-fiber reinforced polymer (CFRP), which failed at 27.1 kips (120.5 kN). CFRP U-wraps were used to anchor this external reinforcement. The third beam is strengthened using two #5 steel NSM bars and 1 layer of GFRP, both extending to the support. GFRP U-wraps were applied to anchor this external reinforcement. This beam failed at 31.5 kips (140 kN). The fourth beam is strengthened with the same system used for the third beam. However, the NSM steel bars were cut short covering 26% of the shear-span only while the GFRP was extended to the support. This beam failed at 30.7 kips (136.5 kN) due to the lack of sufficient development of the NSM steel bars and the shear stress concentration at the steel bar cut off point. Nevertheless, the failure load developed was higher than that of 5 layers of CFRP used for beam 2. The fifth beam was strengthened exactly as the fourth beam, but once strengthened, was loaded five times to cracking load and then submerged in a highly concentrated saline solution for six months. The beam was then tested to failure with a failure load of 29.8 kips (132.6 kN), showing that the GFRP wrapping provided good corrosion resistance.
{"title":"Externally Bonded GFRP and NSM Steel Bars for Improved Strengthening of Rectangular Concrete Beam","authors":"H. Rasheed, A. Wuertz, A. Traplsi, H. Melhem, T. Alkhrdaji","doi":"10.14359/51687080","DOIUrl":"https://doi.org/10.14359/51687080","url":null,"abstract":"The technology of fiber-reinforced polymer (FRP) strengthening has matured to a great extent. However, there is always room for performance improvements. In this study, external bonding of glass-fiber reinforced polymer (GFRP) and near surface mounting of regular steel bars is combined to improve the behavior, delay the failure, and enhance the economy of the strengthening. E-Glass FRP is selected due to its inexpensive cost and non-conductive properties to shield the NSM steel bars from corrosion. On the other hand, the use of NSM bars gives redundancy against vandalism and environmental deterioration of the GFRP. An experimental program is conducted in which five rectangular cross-section beams are designed and built. The first beam is tested as a control beam failing at about 12 kips (53.4 kN). The second beam is strengthened using 5 layers of carbon-fiber reinforced polymer (CFRP), which failed at 27.1 kips (120.5 kN). CFRP U-wraps were used to anchor this external reinforcement. The third beam is strengthened using two #5 steel NSM bars and 1 layer of GFRP, both extending to the support. GFRP U-wraps were applied to anchor this external reinforcement. This beam failed at 31.5 kips (140 kN). The fourth beam is strengthened with the same system used for the third beam. However, the NSM steel bars were cut short covering 26% of the shear-span only while the GFRP was extended to the support. This beam failed at 30.7 kips (136.5 kN) due to the lack of sufficient development of the NSM steel bars and the shear stress concentration at the steel bar cut off point. Nevertheless, the failure load developed was higher than that of 5 layers of CFRP used for beam 2. The fifth beam was strengthened exactly as the fourth beam, but once strengthened, was loaded five times to cracking load and then submerged in a highly concentrated saline solution for six months. The beam was then tested to failure with a failure load of 29.8 kips (132.6 kN), showing that the GFRP wrapping provided good corrosion resistance.","PeriodicalId":191674,"journal":{"name":"\"SP-298: Advanced Materials and Sensors Towards Smart Concrete Bridges: Concept, Performance, Evaluation, and Repair\"","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124635537","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Fiber reinforced polymer (FRP) composites are now common structural materials for both new construction and repair/rehabilitation of existing structures. Since the 1980s researchers have developed a significant body of knowledge on externally-bonded composites for infrastructure repair; however, with emphasis on the use of epoxy systems (matrix and adhesives). Externally-bonded FRP composites with polyurethane matrices and adhesives have recently been investigated due to advantages in constructability and mechanical properties. However, little research is available on bond of polyurethane composites to concrete infrastructure, and direct comparisons between performance of epoxy and polyurethane systems. This paper presents several small-scale experiments to characterize the mechanical properties of the bond to concrete of polyurethane FRP composites alongside with epoxy composites. The tests include 3-point bending tests of concrete beams reinforced with the composite materials, lap shear tests, and coupon tensile tests. Strain data collected from the lap shear experiments were used to develop bond-slip relationships of the composite materials that were then implemented in a finite element model and compared with the experimental flexural results. While polyurethane matrices and adhesives are typically characterized by lower shear and normal strengths, results demonstrate the flexibility of the polyurethane matrix proved advantageous in spreading the bond stresses over a larger area compared with epoxy composites. Therefore polyurethane-reinforced concrete beam stiffness and strength properties are comparable with the epoxy counterparts.
{"title":"Fiber Reinforced Polymer (FRP) Composites in Retrofitting of Concrete Structures: Polyurethane Systems Versus Epoxy Systems","authors":"Elie El Zghayar, K. Mackie, J. Xia","doi":"10.14359/51687084","DOIUrl":"https://doi.org/10.14359/51687084","url":null,"abstract":"Fiber reinforced polymer (FRP) composites are now common structural materials for both new construction and repair/rehabilitation of existing structures. Since the 1980s researchers have developed a significant body of knowledge on externally-bonded composites for infrastructure repair; however, with emphasis on the use of epoxy systems (matrix and adhesives). Externally-bonded FRP composites with polyurethane matrices and adhesives have recently been investigated due to advantages in constructability and mechanical properties. However, little research is available on bond of polyurethane composites to concrete infrastructure, and direct comparisons between performance of epoxy and polyurethane systems. This paper presents several small-scale experiments to characterize the mechanical properties of the bond to concrete of polyurethane FRP composites alongside with epoxy composites. The tests include 3-point bending tests of concrete beams reinforced with the composite materials, lap shear tests, and coupon tensile tests. Strain data collected from the lap shear experiments were used to develop bond-slip relationships of the composite materials that were then implemented in a finite element model and compared with the experimental flexural results. While polyurethane matrices and adhesives are typically characterized by lower shear and normal strengths, results demonstrate the flexibility of the polyurethane matrix proved advantageous in spreading the bond stresses over a larger area compared with epoxy composites. Therefore polyurethane-reinforced concrete beam stiffness and strength properties are comparable with the epoxy counterparts.","PeriodicalId":191674,"journal":{"name":"\"SP-298: Advanced Materials and Sensors Towards Smart Concrete Bridges: Concept, Performance, Evaluation, and Repair\"","volume":"10 1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123455804","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Corrosion of prestressing steel strands in concrete bridge members may lead to the rupture of single strands and catastrophic collapse before visual inspection uncovers evident signs of damage, and well before the end of the design life. Recognizing corrosion in its early stage is critical to plan maintenance and repairs and prevent premature failures. The acoustic emission (AE) technique is a rational means to develop structural health monitoring and prognosis systems for the early detection and location of corrosion in prestressed concrete. It is sensitive to micro- and macro-damage, non-intrusive, and suitable for remote monitoring. However, there is little understanding of the correlation between AE and the extent of early damage in prestressing strands. This paper presents recent advances in AE monitoring of corrosion for prestressing strands embedded in concrete. The state of the art is reviewed, and results from recent research efforts are reported, in which prestressed concrete specimens representative of scaled bridge girders and piles were exposed to salt water through wet/dry cycles. The acoustic emission activity resulting from the early corrosion of strands was studied by evaluating AE data vis-a-vis electrochemical measurements and evidence from scanning electron microscopy.
{"title":"Acoustic Emission Corrosion Monitoring of Prestressed Concrete Bridge Members","authors":"W. Vélez, M. ElBatanouny, F. Matta, P. Ziehl","doi":"10.14359/51687077","DOIUrl":"https://doi.org/10.14359/51687077","url":null,"abstract":"Corrosion of prestressing steel strands in concrete bridge members may lead to the rupture of single strands and catastrophic collapse before visual inspection uncovers evident signs of damage, and well before the end of the design life. Recognizing corrosion in its early stage is critical to plan maintenance and repairs and prevent premature failures. The acoustic emission (AE) technique is a rational means to develop structural health monitoring and prognosis systems for the early detection and location of corrosion in prestressed concrete. It is sensitive to micro- and macro-damage, non-intrusive, and suitable for remote monitoring. However, there is little understanding of the correlation between AE and the extent of early damage in prestressing strands. This paper presents recent advances in AE monitoring of corrosion for prestressing strands embedded in concrete. The state of the art is reviewed, and results from recent research efforts are reported, in which prestressed concrete specimens representative of scaled bridge girders and piles were exposed to salt water through wet/dry cycles. The acoustic emission activity resulting from the early corrosion of strands was studied by evaluating AE data vis-a-vis electrochemical measurements and evidence from scanning electron microscopy.","PeriodicalId":191674,"journal":{"name":"\"SP-298: Advanced Materials and Sensors Towards Smart Concrete Bridges: Concept, Performance, Evaluation, and Repair\"","volume":"65 6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133809875","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This report presents the results of an experimental study conducted to understand the stress-transfer mechanism of fiber reinforced concrete matrix (FRCM) composites externally bonded to a concrete substrate for strengthening applications. The FRCM composite was comprised of a polyparaphenylene benzobisoxazole (PBO) fiber net and polymer-modified cement-based mortar. Direct shear tests were conducted on specimens with composite strips bonded to concrete blocks. Parameters varied were composite bonded length and bonded width. Results were analyzed to understand the effective bonded length, which can be used to establish the load-carrying capacity of the interface to design the strengthening system. The normalized load carrying-capacity was plotted against the width of the composite strip to study the width effect. Finally, strain gage measurements along the bonded length were used to investigate the stress-transfer mechanism.
{"title":"Experimental Investigation of FRCM-Concrete Interfacial Debonding","authors":"L. Sneed, Tommaso D’Antino, C. Carloni","doi":"10.14359/51687076","DOIUrl":"https://doi.org/10.14359/51687076","url":null,"abstract":"This report presents the results of an experimental study conducted to understand the stress-transfer mechanism of fiber reinforced concrete matrix (FRCM) composites externally bonded to a concrete substrate for strengthening applications. The FRCM composite was comprised of a polyparaphenylene benzobisoxazole (PBO) fiber net and polymer-modified cement-based mortar. Direct shear tests were conducted on specimens with composite strips bonded to concrete blocks. Parameters varied were composite bonded length and bonded width. Results were analyzed to understand the effective bonded length, which can be used to establish the load-carrying capacity of the interface to design the strengthening system. The normalized load carrying-capacity was plotted against the width of the composite strip to study the width effect. Finally, strain gage measurements along the bonded length were used to investigate the stress-transfer mechanism.","PeriodicalId":191674,"journal":{"name":"\"SP-298: Advanced Materials and Sensors Towards Smart Concrete Bridges: Concept, Performance, Evaluation, and Repair\"","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130486917","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Overlays are installed on concrete bridge decks to improve ride quality, and in the case of impermeable overlays, also protect the deck from exposure to moisture and chlorides. Moisture and chlorides can penetrate over time into reinforced concrete, allowing for the initiation and progression of corrosion, which shorten the service life of a structure. To evaluate whether impermeable overlays are truly keeping moisture from penetrating into the concrete deck, researchers have implemented wireless moisture sensors in several bridge decks to monitor the moisture content of the deck below the overlay. In this study, the four overlays that are being monitored are a hot-mix asphalt wearing surface with a thermoplastic additive, an epoxy polymer concrete overlay, a fabric-reinforced liquid membrane with asphalt wearing surface, and a thin-set urethane membrane with an asphalt wearing surface. The moisture sensors have been installed at various locations in each deck including near the bridge joints, overlay construction joints, drainage paths, and under wheel paths. Results indicate that the hot-mix asphalt wearing surface with thermoplastic additive overlay only has moisture penetrating in regions that are near the joints. Measurements also indicate that the polymer concrete overlay has been effective at preventing the penetration of moisture. The latter two overlays, a fabric-reinforced asphalt membrane and a thin-set urethane, were recently installed and some preliminary conclusions may be offered about their effectiveness based upon early results.
{"title":"Evaluation of the Impermeability of Bridge Deck Overlays using Embedded Wireless Moisture Sensors","authors":"B. Pailes, Michael C Brown, A. Foden, N. Gucunski","doi":"10.14359/51687079","DOIUrl":"https://doi.org/10.14359/51687079","url":null,"abstract":"Overlays are installed on concrete bridge decks to improve ride quality, and in the case of impermeable overlays, also protect the deck from exposure to moisture and chlorides. Moisture and chlorides can penetrate over time into reinforced concrete, allowing for the initiation and progression of corrosion, which shorten the service life of a structure. To evaluate whether impermeable overlays are truly keeping moisture from penetrating into the concrete deck, researchers have implemented wireless moisture sensors in several bridge decks to monitor the moisture content of the deck below the overlay. In this study, the four overlays that are being monitored are a hot-mix asphalt wearing surface with a thermoplastic additive, an epoxy polymer concrete overlay, a fabric-reinforced liquid membrane with asphalt wearing surface, and a thin-set urethane membrane with an asphalt wearing surface. The moisture sensors have been installed at various locations in each deck including near the bridge joints, overlay construction joints, drainage paths, and under wheel paths. Results indicate that the hot-mix asphalt wearing surface with thermoplastic additive overlay only has moisture penetrating in regions that are near the joints. Measurements also indicate that the polymer concrete overlay has been effective at preventing the penetration of moisture. The latter two overlays, a fabric-reinforced asphalt membrane and a thin-set urethane, were recently installed and some preliminary conclusions may be offered about their effectiveness based upon early results.","PeriodicalId":191674,"journal":{"name":"\"SP-298: Advanced Materials and Sensors Towards Smart Concrete Bridges: Concept, Performance, Evaluation, and Repair\"","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114202304","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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