The Experts below are selected from a list of 90711 Experts worldwide ranked by ideXlab platform
Riadh Almahaidi - One of the best experts on this subject based on the ideXlab platform.
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utilization of magnetic water in cementitious adhesive for near surface mounted cfrp Strengthening System
Construction and Building Materials, 2019Co-Authors: Rawaa Alsafy, Alaa Almosawe, Riadh AlmahaidiAbstract:Abstract Cement-based adhesive (CBA) is used as a bonding agent in Carbon Fibre Reinforced Polymer (CFRP) applications as an alternative to epoxy-based adhesive due to the drawbacks of the epoxy System under severe service conditions which negatively affect the bond between the CFRP and strengthened elements. This paper reports the results of, an investigation carried out to develop two types of CBA using magnetized water (MW) for mixing and curing. Two magnetic devices (MD-I and MD-II), with different magnetic field strengths (9000 and 6000 Gauss) respectively, were employed for water magnetization. Different water flows with different water circulation times in the magnetizer were used for each device. Compressive and splitting tensile strength tests of the magnetized CBA (MCBA) were conducted for different curing periods (3. 7, 14, 21 and 28 days) using MW. It was found that MW treatment increases the strength of CBA. The highest strength was obtained for MCBA samples when MD-I was used at a low flow rate (F = 0.1 m3/hr) for 15 mins of circulation time (T). The latter was found to positively affect MCBA properties when T was increased from 15 min to 60 mins. Prediction of the compressive and tensile strength values are also studied in this paper using genetic programming, the models showed good correlation with the experimental data.
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bond behaviour between nsm cfrp strips and concrete at high temperature using innovative high strength self compacting cementitious adhesive ihssc ca made with graphene oxide
Construction and Building Materials, 2016Co-Authors: Nihad Tareq Khshain Alsaadi, Alyaa Mohammed, Riadh AlmahaidiAbstract:Abstract Strengthening of reinforced concrete (RC) structures using the near-surface mounted (NSM) fibre reinforced polymer (FRP) method is becoming an attractive technique for upgrading the existing structural elements. The exposure of the NSM FRP Strengthening System to high temperatures greatly affects the bond between FRP, adhesive material and the concrete substrate. Organic adhesives are widely used in the NSM Strengthening technique. However, their low fire resistance is a major drawback. This study investigates the performance of NSM carbon FRP Strengthening technique using single-lap shear tests (pull-out tests) with innovative high-strength self-compacting cementitious adhesive (IHSSC-CA) under high temperatures. Graphene oxide and cementitious materials were used to synthesise the IHSSC-CA. Single-lab shear tests were conducted on NSM strengthened specimens which were exposed to high temperatures of 800 °C. The results obtained from the pull-out tests signifies that the samples made with IHSSC-CA were less affected by high temperature, and maintain considerable residual bond strength. Theoretical equations are proposed to simulate the effect of high temperature on bond strength.
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modified cement based adhesive for near surface mounted cfrp Strengthening System
Construction and Building Materials, 2016Co-Authors: Ahmed Alabdwais, Riadh AlmahaidiAbstract:Abstract The Strengthening System with near-surface mounted (NSM) has emerged in last decades as a promising technology to improve the flexural and shear strength of concrete structures. Large number of concrete structures have been strengthened worldwide by this technique using epoxy adhesives. However, the rapid deterioration of the mechanical properties of epoxy-based polymer matrix at elevated temperature, and the hazardous effects of toxic fumes during the application made the need of replacing this polymer with a new cementitious bonding agent to enhance the performance of concrete structures in high-temperature environments and reduce the environmental and health hazards. The application of cement-based adhesive has been studied for externally-bonded techniques using CFRP textile. Although, the good bond properties has been achieved, debonding was the critical failure between fibre and concrete substrate. To exploit the advantages of NSM technique, a new modification of cement-based adhesive has been achieved to be compatible with requirements of NSM application System. To assess the efficiency of this adhesive, an experimental investigation of pull-out testing using a single-lap shear test set-up was conducted to study the bond characteristics between CFRP textile and concrete. Four different mixes were used in this investigation. The test results show the efficiency of the NSM technique using modified cement adhesive and its superior bond properties compared to externally-bonded CFRP.
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flexural performance of cfrp textile retrofitted rc beams using cement based adhesives at high temperature
Construction and Building Materials, 2012Co-Authors: Siavash Hashemi, Riadh AlmahaidiAbstract:Abstract Strengthening of concrete structures with epoxy-bonded FRP composites is suitable for environments where the temperature is well below the glass transition temperature of the epoxy adhesive, T g , which is normally in the range of 55–60 °C. It is very beneficial if cementitious mineral-based bonding agents replace epoxy adhesives in order to produce a fire-resistant Strengthening System. Tests conducted by the authors have already shown that excellent reinforcement action can be achieved using cement-based adhesives. Tests included in the current paper include the heat endurance of CFRP textile-retrofitted RC beams under constant service load. The strengthened RC beam with cement-based adhesive showed a considerable improvement in flexural performance at high temperature compared to the specimens with epoxy. The specimens with cement-based adhesive failed at temperatures nearly double of that with epoxy-based adhesive.
Sami Rizkalla - One of the best experts on this subject based on the ideXlab platform.
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CFRP shear Strengthening System for steel bridge girders
Engineering Structures, 2018Co-Authors: Hamid Kazem, Sami Rizkalla, Ye Zhang, Rudolf Seracino, Akira KobayashiAbstract:Abstract This paper presents an investigation undertaken to study the effectiveness of using small-diameter CFRP strands for shear Strengthening of steel bridge girders. The study includes a comprehensive experimental program to study effects of the CFRP reinforcement ratio and orientation of the strands. An analytical model, calibrated by the experimental tests, was used to provide design recommendation. Results of the study showed that the proposed Strengthening System is effective in increasing the shear capacity of steel bridge girders and there was no sign of CFRP debonding or rupture failure commonly observed by CFRP laminates up to approximately 80% of the steel yield stress.
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environmental durability of a cfrp System for Strengthening steel structures
Construction and Building Materials, 2010Co-Authors: Mina Dawood, Sami RizkallaAbstract:Recently a high modulus CFRP System was developed to enhance the load carrying capacity and serviceability of steel bridges and structures. However, the environmental durability of the System has not yet been demonstrated. This paper presents the findings of a research program that was conducted to evaluate the environmental durability of the bond of the proposed CFRP Strengthening System to steel surfaces. The program consisted of testing 44 steel-CFRP double-lap shear specimens. The specimens were exposed to severe environmental conditions for different durations, up to 6 months. Different methods to enhance the bond durability were studied including pre-treating the steel surface with a silane coupling agent, inserting a glass fiber layer within the adhesive and a combination of both methods of protection. The research findings indicate that the use of a silane coupling agent significantly enhanced the bond durability. While the presence of the glass fibers helped to enhance the initial bond strength of the System, it did not improve the durability of the bond. The use of both techniques enhanced both the overall bond strength and the environmental durability of the Strengthening System.
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Effective Splices for a Carbon Fiber–Reinforced Polymer: Strengthening System for Steel Bridges and Structures
Transportation Research Record, 2009Co-Authors: Mina Dawood, Murthy N. Guddati, Sami RizkallaAbstract:Carbon fiber-reinforced polymer (CFRP) materials have been used successfully to strengthen reinforced concrete bridges and structures. Recently, a new high modulus CFRP Strengthening System was developed to increase the allowable load carrying capacity and to enhance the serviceability of steel bridges and structures. Because of the relatively high flexural rigidity of the CFRP materials, the length of the CFRP plates that can be transported to the job site is limited. To implement the proposed Strengthening System in longer-span steel bridges, adjacent lengths of CFRP must be spliced. To develop an effective splice joint for the proposed Strengthening System, an experimental and analytical research program was conducted to study the bond behavior of the CFRP materials. The parameters considered included plate end geometry, splice length, and the possibility of using mechanical anchorage. The analytical study included a finite element analysis to determine the distribution of the stresses within the adhes...
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Self-monitoring fiber reinforced polymer Strengthening System for civil engineering infrastructures
Nondestructive Characterization for Composite Materials Aerospace Engineering Civil Infrastructure and Homeland Security 2008, 2008Co-Authors: Guoliang Jiang, Mina Dawood, Kara Peters, Sami RizkallaAbstract:Fiber reinforced polymer (FRP) materials are currently used for Strengthening civil engineering infrastructures. The Strengthening System is dependant on the bond characteristics of the FRP to the external surface of the structure to be effective in resisting the applied loads. This paper presents an innovative self-monitoring FRP Strengthening System. The System consists of two components which can be embedded in FRP materials to monitor the global and local behavior of the strengthened structure respectively. The first component of the System is designed to evaluate the applied load acting on a structure based on elongation of the FRP layer along the entire span of the structure. Success of the global System has been demonstrated using a full-scale prestressed concrete bridge girder which was loaded up to failure. The test results indicate that this type of sensor can be used to accurately determine the load prior to failure within 15 percent of the measured value. The second sensor component consists of fiber Bragg grating sensors. The sensors were used to monitor the behavior of steel double-lap shear splices tested under tensile loading up to failure. The measurements were used to identify abnormal structural behavior such as epoxy cracking and FRP debonding. Test results were also compared to numerical values obtained from a three dimensional shear-lag model which was developed to predict the sensor response.
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development of a carbon fiber reinforced polymer System for Strengthening steel structures
Composites Part A-applied Science and Manufacturing, 2008Co-Authors: Sami Rizkalla, Mina Dawood, David SchnerchAbstract:Abstract This paper summarizes the development and use of high modulus carbon fiber reinforced polymer (HM CFRP) materials for the retrofit of steel structures and bridges. The development work included selection of an appropriate adhesive for bonding HM CFRP materials to steel and the performance of large-scale steel–concrete composite beams tested to examine the behavior using different Strengthening schemes. The experimental program investigated the behavior of the Strengthening System under fatigue and overloading conditions. A detailed study of bond behavior, including the possible presence of shear-lag effects and performance of spliced joints is also presented. Based on the findings, flexural design guidelines are proposed. The study indicates that CFRP materials can be effectively used to enhance the serviceability and ultimate strength of steel flexural members.
Mina Dawood - One of the best experts on this subject based on the ideXlab platform.
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environmental durability of a cfrp System for Strengthening steel structures
Construction and Building Materials, 2010Co-Authors: Mina Dawood, Sami RizkallaAbstract:Recently a high modulus CFRP System was developed to enhance the load carrying capacity and serviceability of steel bridges and structures. However, the environmental durability of the System has not yet been demonstrated. This paper presents the findings of a research program that was conducted to evaluate the environmental durability of the bond of the proposed CFRP Strengthening System to steel surfaces. The program consisted of testing 44 steel-CFRP double-lap shear specimens. The specimens were exposed to severe environmental conditions for different durations, up to 6 months. Different methods to enhance the bond durability were studied including pre-treating the steel surface with a silane coupling agent, inserting a glass fiber layer within the adhesive and a combination of both methods of protection. The research findings indicate that the use of a silane coupling agent significantly enhanced the bond durability. While the presence of the glass fibers helped to enhance the initial bond strength of the System, it did not improve the durability of the bond. The use of both techniques enhanced both the overall bond strength and the environmental durability of the Strengthening System.
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Effective Splices for a Carbon Fiber–Reinforced Polymer: Strengthening System for Steel Bridges and Structures
Transportation Research Record, 2009Co-Authors: Mina Dawood, Murthy N. Guddati, Sami RizkallaAbstract:Carbon fiber-reinforced polymer (CFRP) materials have been used successfully to strengthen reinforced concrete bridges and structures. Recently, a new high modulus CFRP Strengthening System was developed to increase the allowable load carrying capacity and to enhance the serviceability of steel bridges and structures. Because of the relatively high flexural rigidity of the CFRP materials, the length of the CFRP plates that can be transported to the job site is limited. To implement the proposed Strengthening System in longer-span steel bridges, adjacent lengths of CFRP must be spliced. To develop an effective splice joint for the proposed Strengthening System, an experimental and analytical research program was conducted to study the bond behavior of the CFRP materials. The parameters considered included plate end geometry, splice length, and the possibility of using mechanical anchorage. The analytical study included a finite element analysis to determine the distribution of the stresses within the adhes...
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Self-monitoring fiber reinforced polymer Strengthening System for civil engineering infrastructures
Nondestructive Characterization for Composite Materials Aerospace Engineering Civil Infrastructure and Homeland Security 2008, 2008Co-Authors: Guoliang Jiang, Mina Dawood, Kara Peters, Sami RizkallaAbstract:Fiber reinforced polymer (FRP) materials are currently used for Strengthening civil engineering infrastructures. The Strengthening System is dependant on the bond characteristics of the FRP to the external surface of the structure to be effective in resisting the applied loads. This paper presents an innovative self-monitoring FRP Strengthening System. The System consists of two components which can be embedded in FRP materials to monitor the global and local behavior of the strengthened structure respectively. The first component of the System is designed to evaluate the applied load acting on a structure based on elongation of the FRP layer along the entire span of the structure. Success of the global System has been demonstrated using a full-scale prestressed concrete bridge girder which was loaded up to failure. The test results indicate that this type of sensor can be used to accurately determine the load prior to failure within 15 percent of the measured value. The second sensor component consists of fiber Bragg grating sensors. The sensors were used to monitor the behavior of steel double-lap shear splices tested under tensile loading up to failure. The measurements were used to identify abnormal structural behavior such as epoxy cracking and FRP debonding. Test results were also compared to numerical values obtained from a three dimensional shear-lag model which was developed to predict the sensor response.
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development of a carbon fiber reinforced polymer System for Strengthening steel structures
Composites Part A-applied Science and Manufacturing, 2008Co-Authors: Sami Rizkalla, Mina Dawood, David SchnerchAbstract:Abstract This paper summarizes the development and use of high modulus carbon fiber reinforced polymer (HM CFRP) materials for the retrofit of steel structures and bridges. The development work included selection of an appropriate adhesive for bonding HM CFRP materials to steel and the performance of large-scale steel–concrete composite beams tested to examine the behavior using different Strengthening schemes. The experimental program investigated the behavior of the Strengthening System under fatigue and overloading conditions. A detailed study of bond behavior, including the possible presence of shear-lag effects and performance of spliced joints is also presented. Based on the findings, flexural design guidelines are proposed. The study indicates that CFRP materials can be effectively used to enhance the serviceability and ultimate strength of steel flexural members.
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proposed design guidelines for Strengthening of steel bridges with frp materials
Construction and Building Materials, 2007Co-Authors: David Schnerch, Sami Rizkalla, Mina Dawood, Eric SumnerAbstract:Abstract This paper focuses on the use of externally bonded high modulus carbon fiber reinforced polymer (HM CFRP) materials to strengthen steel bridges and structures. Proper installation of the CFRP materials is necessary to prevent premature failure due to debonding. The paper proposes guidelines and installation techniques based on the best practice reported in the literature and the extensive practical experience in bonding of composite materials. The surface preparation of the materials, the application of the adhesive and the detailing of the Strengthening are provided in detail. The design guidelines include the structural design criteria for the use of high modulus CFRP materials as flexural Strengthening System of typical steel–concrete composite bridge girders. The flexural design procedure is based on a moment–curvature analysis and a specified increase of the live load carried by the bridge to satisfy specific serviceability requirements. A bond model is also described which can be used to calculate the shear and peel stresses within the adhesive thickness. To prevent a premature debonding failure of the Strengthening System, the criteria specify a maximum principle stress in the adhesive which cannot be exceeded for a given characteristic strength of an adhesive. A worked example is presented to illustrate the proposed flexural design approach. The research findings conclude that high modulus CFRP materials provide a promising alternative for Strengthening steel bridges that can be easily designed and installed to increase their strength and stiffness.
David Schnerch - One of the best experts on this subject based on the ideXlab platform.
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development of a carbon fiber reinforced polymer System for Strengthening steel structures
Composites Part A-applied Science and Manufacturing, 2008Co-Authors: Sami Rizkalla, Mina Dawood, David SchnerchAbstract:Abstract This paper summarizes the development and use of high modulus carbon fiber reinforced polymer (HM CFRP) materials for the retrofit of steel structures and bridges. The development work included selection of an appropriate adhesive for bonding HM CFRP materials to steel and the performance of large-scale steel–concrete composite beams tested to examine the behavior using different Strengthening schemes. The experimental program investigated the behavior of the Strengthening System under fatigue and overloading conditions. A detailed study of bond behavior, including the possible presence of shear-lag effects and performance of spliced joints is also presented. Based on the findings, flexural design guidelines are proposed. The study indicates that CFRP materials can be effectively used to enhance the serviceability and ultimate strength of steel flexural members.
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proposed design guidelines for Strengthening of steel bridges with frp materials
Construction and Building Materials, 2007Co-Authors: David Schnerch, Sami Rizkalla, Mina Dawood, Eric SumnerAbstract:Abstract This paper focuses on the use of externally bonded high modulus carbon fiber reinforced polymer (HM CFRP) materials to strengthen steel bridges and structures. Proper installation of the CFRP materials is necessary to prevent premature failure due to debonding. The paper proposes guidelines and installation techniques based on the best practice reported in the literature and the extensive practical experience in bonding of composite materials. The surface preparation of the materials, the application of the adhesive and the detailing of the Strengthening are provided in detail. The design guidelines include the structural design criteria for the use of high modulus CFRP materials as flexural Strengthening System of typical steel–concrete composite bridge girders. The flexural design procedure is based on a moment–curvature analysis and a specified increase of the live load carried by the bridge to satisfy specific serviceability requirements. A bond model is also described which can be used to calculate the shear and peel stresses within the adhesive thickness. To prevent a premature debonding failure of the Strengthening System, the criteria specify a maximum principle stress in the adhesive which cannot be exceeded for a given characteristic strength of an adhesive. A worked example is presented to illustrate the proposed flexural design approach. The research findings conclude that high modulus CFRP materials provide a promising alternative for Strengthening steel bridges that can be easily designed and installed to increase their strength and stiffness.
Kequan Yu - One of the best experts on this subject based on the ideXlab platform.
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flexural Strengthening of rc beams with cfrp grid reinforced ecc matrix
Composite Structures, 2018Co-Authors: Zhoudao Lu, Kequan Yu, Xu YangAbstract:Abstract This paper investigates the flexural performance of a series of RC beams externally bonded with carbon fiber-reinforced polymer (CFRP) grid-reinforced engineered cementitious composite (ECC) matrix. A total of 15 RC beams, including three control and twelve strengthened, were prepared and tested. The test variables included the longitudinal reinforcement ratio, the Strengthening configurations that consisted of different cementitious matrices (ECC versus epoxy mortar), different installation methods (prefabricated versus cast-in-place), and different stiffness of CFRP grids. The test results showed that ECC is an ideal cementitious matrix for the Strengthening applications where FRP grids are used as the external reinforcement. The flexural Strengthening configuration using the epoxy adhesive to bond prefabricated CFRP grid-reinforced ECC plate proved to be the most efficient solution. For such configuration, the plate-end debonding can be avoided and the mid-span debonding can be almost suppressed. Flexural capacity analysis was conducted and demonstrated that the plane section assumption is valid and the full strength composite action can be nearly achieved for the Strengthening System. The average ratio of the predicted peak loads to the experimental ones of the strengthened RC beams was 1.05.
