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Surface Roughness Quasi Static Fracture And Cyclic Fatigue Effects On Gfrp And Cfrp Concrete Bonded Interfaces
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Book Synopsis Surface Roughness, Quasi-Static Fracture, and Cyclic Fatigue Effects on GFRP- and CFRP-Concrete Bonded Interfaces by : TO. Lawrence
Download or read book Surface Roughness, Quasi-Static Fracture, and Cyclic Fatigue Effects on GFRP- and CFRP-Concrete Bonded Interfaces written by TO. Lawrence and published by . This book was released on 2006 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: The recently developed experimental fracture approach known as the Single Contoured-Cantilever Beam (SCCB) was used to characterize the interface bonds between concrete substrates and two varieties of FRP: glass and carbon (abbreviated GFRP and CFRP, respectively). Limited research has been performed concerning the FRP-concrete interface bond relative to three surface-roughness grades: low- (10 ?m), moderate- (? 10-50 ?m), and high- (50 ?m), to establish the optimal formation for bonding. By use of the SCCB approach, Mode I critical strain energy release rate results are measured and quantified. Finally, considering that a majority of externally strengthened FRP concrete structures involves bridges and girders that are subjected to repeated (as opposed to static) loads, a preliminary study is conducted on cyclically fatigued FRP-concrete interfaces under varying load-ratio and frequency effects.
Book Synopsis Fatigue and Fracture Mechanics by : Richard Edward Link
Download or read book Fatigue and Fracture Mechanics written by Richard Edward Link and published by . This book was released on 2007 with total page 544 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Effects of Moisture on Debonding in FRP-retrofitted Concrete Systems by : Chakrapan Tuakta
Download or read book Effects of Moisture on Debonding in FRP-retrofitted Concrete Systems written by Chakrapan Tuakta and published by . This book was released on 2011 with total page 195 pages. Available in PDF, EPUB and Kindle. Book excerpt: FRP (fiber reinforced polymer) retrofit systems for reinforced concrete (RC) structures have been widely used in the past 10 years, and numerous studies on its short-term debonding behavior have been conducted extensively. Nevertheless, long-term performance and durability issues regarding such debonding behavior still remain largely uncertain and unanswered. In this study, comprehensive experimental and analytical investigations of debonding in FRP bonded concrete systems under long-term environmental exposure, namely moisture, have been performed to develop mechanics-based predictive debonding failure models and related design tools for the prevention of debonding failures. The experimental approach involves an investigation of debonding under moisture ingress, moisture reversal, cyclic moisture conditioning, using the concept of fracture mechanics and meso-scale tri-layer fracture specimens. Prolonged exposure to moisture condition has been shown to result in significant degradation of the FRP/concrete bond strength, while an irreversible weakening in the bond strength has also been observed in the fracture specimens under moisture cyclic condition. A predictive model has been developed based on the experimental results of the fracture specimens under variable cyclic moisture conditions for service life prediction of the FRP-strengthened systems. To incorporate this quantification method and experimental data, finite element analysis and correlation study have been conducted for RC beams externally strengthened with FRP plate. The cohesive zone model for interfacial fracture has been implemented, for which the properties of the interface were obtained from the meso-scale fracture tests. Test on laboratory-scale FRP-strengthened RC beam specimens under continuous moisture conditions has demonstrated the applicability of the methodology. In addition, molecular dynamics simulation has been conducted to gain more fundamental understanding of interface fracture behavior in bi-layer material systems (i.e. crack initiation and propagation direction) and the effects of material and interface properties at atomistic scale. Finally, a recommendation has been made to the current design of RC beams strengthened with FRP to prevent premature failure due to long-term exposure to moisture.
Book Synopsis Influence of Surface Roughness on CFRP/Concrete Composites in Flexure by : Erandi Ariyachandra
Download or read book Influence of Surface Roughness on CFRP/Concrete Composites in Flexure written by Erandi Ariyachandra and published by LAP Lambert Academic Publishing. This book was released on 2015-09-07 with total page 76 pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbon Fibre Reinforced Polymer (CFRP) composites have been progressively more utilized to strengthen the concrete members to improve its flexural performance. Flexural capacity of CFRP strengthened concrete members mainly hinge on controlling probable failure modes. The inter-facial bond failure takes place owing poor surface preparation for FRP application which grounds a bond failure between concrete and adhesive eventually. Preparation of concrete substrate plays a significant role in terms of engendering strong bond between FRP - concrete interface. Achieving uniform surface roughness all through the concrete substrates is the major issue in surface preparation procedure since the uniformity of the roughened concrete substrates totally depends on the human skills and experience. Existing surface roughness quantification methods have a substantial discrepancy although a unique quantification method is essential more imperatively. In the present study, the experimental investigation was focused on the flexural performance of the externally strengthened CFRP concrete beams with different types of surface preparation levels.
Book Synopsis Hygrothermal Effects on Interface Fracture of Frp Bonded Concrete by : Ching Au
Download or read book Hygrothermal Effects on Interface Fracture of Frp Bonded Concrete written by Ching Au and published by LAP Lambert Academic Publishing. This book was released on 2009-09 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides an explicit description of the interface fracture behavior of FRP bonded concrete that is subjected to temperature and moisture effects. Extensive characterization of each constituent material is performed. Measured properties, in conjunction with peel and shear fracture load data, are used to calculate joint toughness by means of a newly developed tri-layer fracture model. Computed toughness, along with outputs of a fracture mode-mix analysis and a 3D moisture diffusion simulation are synergistically analyzed. Results suggest that moisture can physically change the property of a bond, and that of the adjoining materials. Joint toughness can degrade as much as 60% due to moisture ingress alone. Debonding mode will also shift from material decohesion to interface separation, which is rarely detected in short-term tests. Interface fracture analysis reveals why an initiated crack prefers to propagate along a debonded interface as opposed to bifurcating into concrete even though it appears to be the weakest link. This book aims to provide valuable test data and useful insights to structural engineers to design tougher retrofitted systems.
Book Synopsis Developments in fiber-reinforced polymer (FRP) composites for civil engineering by : J. Wang
Download or read book Developments in fiber-reinforced polymer (FRP) composites for civil engineering written by J. Wang and published by Elsevier Inc. Chapters. This book was released on 2013-05-15 with total page 35 pages. Available in PDF, EPUB and Kindle. Book excerpt: Strengthening reinforced concrete (RC) members using fiber reinforced polymer (FRP) composites through external bonding has emerged as a viable technique to retrofit/repair deteriorated infrastructure. The interface between the FRP and concrete plays a critical role in this technique. This chapter discusses the analytical and experimental methods used to examine the integrity and long-term durability of this interface. Interface stress models, including the commonly adopted two-parameter elastic foundation model and a novel three-parameter elastic foundation model (3PEF) are first presented, which can be used as general tools to analyze and evaluate the design of the FRP strengthening system. Then two interface fracture models – linear elastic fracture mechanics and cohesive zone model – are established to analyze the potential and full debonding process of the FRP–concrete interface. Under the synergistic effects of the service loads and environments species, the FRP–concrete interface experiences deterioration, which may reduce its long-term durability. A novel experimental method, environment-assisted subcritical debonding testing, is then introduced to evaluate this deteriorating process. The existing small cracks along the FRP–concrete interface can grow slowly even if the mechanical load is lower than the critical value. This slow-crack growth process is known as environment-assisted subcritical cracking. A series of subcritical cracking tests are conducted using a wedge-driven test setup t o gain the ability to accurately predict the long-term durability of the FRP–concrete interface.
Book Synopsis Toughening Mechanisms in Quasi-brittle Materials by : Surendra P. Shah
Download or read book Toughening Mechanisms in Quasi-brittle Materials written by Surendra P. Shah and published by Kluwer Academic Pub. This book was released on 1991-01-01 with total page 612 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Mode-I Fracture of CFRP Concrete Specimens Subjected to Elevated Temperatures by : Richard Alfred Cobb
Download or read book Mode-I Fracture of CFRP Concrete Specimens Subjected to Elevated Temperatures written by Richard Alfred Cobb and published by . This book was released on 2013 with total page 196 pages. Available in PDF, EPUB and Kindle. Book excerpt: The following thesis presents a methodology to evaluate Mode I fracture of Carbon Fiber Reinforced Polymer (CFRP) to concrete bonded interfaces subjected to both ambient and elevated temperatures. Current codes and standards such as ACI 440.2R-08 provide guidelines for the design of concrete strengthened or rehabilitated structures with CFRP. However, ACI considers the contribution of CFRP to be negligible in conditions above ambient temperatures. Previous methods of testing such as the Single Contoured Cantilever Beam (SCCB), Modified Double Cantilever Beam (MDCB), Peel test, and Three Point Bending Beam (3PBB) tests have been utilized in evaluating Mode I failure. However, due to size limitations the previously listed methodologies were unsuitable for testing under elevated temperatures. Therefore, a Modified Driven Wedge Test (MDWT) was developed based on the Boeing and Driven Wedge Test. This effort presents the development of the MDWT, the performance of the CFRP to concrete bonded interface subjected to ambient temperatures and elevated temperatures. It was discovered that with an introduction of elevated temperatures, Mixed-Mode Failure is induced at 100°F, but crack separation is supported by Mode-I failure at the subcritical level. An analysis of critical strain energy release rate and subcritical strain energy release rate revealed that as the temperature increases, energy release rate increase, but crack growth velocity decreases.
Book Synopsis Interface Fracture and Bond by : Oral Buyukozturk
Download or read book Interface Fracture and Bond written by Oral Buyukozturk and published by . This book was released on 1995 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Modeling of Adhesively Bonded Joints by : Lucas F. M. da Silva
Download or read book Modeling of Adhesively Bonded Joints written by Lucas F. M. da Silva and published by Springer Science & Business Media. This book was released on 2008-10-14 with total page 335 pages. Available in PDF, EPUB and Kindle. Book excerpt: A lot of recent developments have been made about adhesively bonded joints modeling using various methods of analysis. The increasing application of adhesives in industry is partly due to the increased sophistication and reliability of adhesive joints modeling. The book proposed intends to provide the designer with the most advanced stress analyses techniques in adhesive joints to reinforce the use of this promising bonding technique.
Book Synopsis Mode I Fracture and Durability of the CFRP-concrete Interface Bond by :
Download or read book Mode I Fracture and Durability of the CFRP-concrete Interface Bond written by and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Mechanics and Subcritical Cracking of FRP-concrete Interface by : Chao Zhang
Download or read book Mechanics and Subcritical Cracking of FRP-concrete Interface written by Chao Zhang and published by . This book was released on 2011 with total page 273 pages. Available in PDF, EPUB and Kindle. Book excerpt: The need for safe, effective, and efficient methods to strengthen and upgrade our nation's infrastructures is clear. Strengthening Reinforced Concrete (RC) members using Fiber Reinforced Polymer (FRP) composites through external bonding has emerged as a viable technique to retrofit/repair deteriorated infrastructures. The interface between the FRP and concrete plays a critical role in this technique. This study proposes a life-cycle analytical framework on the integrity and long-term durability of the FRP-concrete interface through a combined analytical, numerical, and experimental approach. A novel three-parameter elastic foundation model (3PEF) is first established to provide a general tool to analyze and evaluate the design of the FRP strengthening system. This model correctly predicts the location where debonding can occur. To simulate the interface stress redistribution and creep deformations accumulated during service life due to the strong time dependent features of the adhesive layer, linear viscoelastic analytical solutions are then developed for the FRP-strengthened RC beams. Small cracks usually exist within the FRP-concrete interface, making fracture mechanics a more appropriate tool to evaluate the integrity of the FRP-concrete interface. Analytical solutions of energy release rate (ERR) and its phase angle at the tip of a crack along the FRP-concrete interface are obtained. Under the synergistic effects of the service loads and environments species, these small cracks can grow slowly even if the ERR at the crack tip is lower than the critical value. This slow-crack growth process is known as environment-assisted subcritical cracking. A series of subcritical cracking testing are conducted using a wedge-driven testing to gain the ability to accurately predict the long-term durability of the FRP-concrete interface. It has been found that water, deicing salt and alkaline solutions can substantially reduce the ERR at the crack tip needed to drive the subcritical crack growth along the epoxy-concrete interface. Once the small cracks grow to the critical length, critical debonding will occur, leading to the premature failure of the structure. A nonlinear fracture mechanics model using a Cohesive Zone Model (CZM) is finally developed to simulate this final failure phase of the FRP-concrete interface.
Book Synopsis Effects of Temperature and Sustained Loading on the Response of FRP-strengthened Concrete Elements by : Yoseok Jeong
Download or read book Effects of Temperature and Sustained Loading on the Response of FRP-strengthened Concrete Elements written by Yoseok Jeong and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Fiber reinforced polymer (FRP) repair systems for concrete structures have been widely used in civil infrastructure. Concrete-epoxy interfaces (CEI) are formed during the installation of externally bonded FRP systems to concrete structures. Research on their short-term behavior under aggressive environmental conditions has been conducted extensively in the past. Nevertheless, long-term performance and durability issues of these strengthening systems still remain largely uncertain. Thus, it is critical to study the effects of sustained load and temperature on the time-dependent deformation of the concrete-epoxy interface along with the residual strength of the FRP-strengthened concrete element.Single-lap shear and three-point bending test specimens were used to evaluate temperature effect and the time-dependent behavior during sustained loading below and at ultimate strength after the sustained loading period. The test results demonstrated the effects of temperature and sustained loading on creep behavior and on the remaining strength (the fracture energy) after creep duration. The creep responses of single-lap shear and three-point bending test specimens depend on the creep response of the epoxy. The effect of sustained loading on the remaining strength is positive for the single-lap shear specimens. However, this positive effect decreases as the creep duration increases. On the other hand, for the three-point bending test specimens, the sustained loading effect is negative on the remaining strength because presence of sustained loading leads to a weakening in the bond strength in the concrete-epoxy interface, which is evidenced by the fracture surface analysis of tested three-point bending specimens.Results of a numerical study of the single-lap shear specimens are also presented. Numerical models used the viscoelastic model for the creep tests and a plastic damage model for the bond tests. Results were compared with the available experimental results. The results show good correlations between the analysis and tests. It is proven that the creep behavior of the single-lap shear specimen is mainly governed by the creep characteristics of the epoxy. The numerical results also suggest that the redistributing of the interfacial bond stress can lead to an increase in the remaining strength of the single-lap shear specimens. A parametric study is carried out in order to investigate the various factors affecting creep behaviors and bond behaviors of single-lap shear specimens. Elevated temperatures and increased epoxy thicknesses lead to an increase in the remaining strength of the single-lap shear specimens due to stress redistribution occurring during the sustained loading period.
Book Synopsis Fatigue Bond Behaviour of Corroded Reinforcement and CFRP Confined Concrete by : Ahmad Rteil
Download or read book Fatigue Bond Behaviour of Corroded Reinforcement and CFRP Confined Concrete written by Ahmad Rteil and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Effect of Surface Roughness and Putty Thickness on the Bond Performance of FRP Laminates by : Xianlin Shen
Download or read book Effect of Surface Roughness and Putty Thickness on the Bond Performance of FRP Laminates written by Xianlin Shen and published by . This book was released on 2002 with total page 181 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The ultimate goal of this study is to propose recommendations that may be used in the development of construction specifications for repair of concrete structures using FRP reinforcement."--Introduction, p. 2.
Book Synopsis Thermal and Mechanical Fatigue Effects on Glass Fiber-reinforced Plastic Rebar-concrete Bond by : Annie Christine Retika
Download or read book Thermal and Mechanical Fatigue Effects on Glass Fiber-reinforced Plastic Rebar-concrete Bond written by Annie Christine Retika and published by . This book was released on 1997 with total page 126 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Bond Characteristics and Fatigue Behaviour of Steel Structures Strengthened with Ultra High Modulus CFRP Plates by : Chao Wu
Download or read book Bond Characteristics and Fatigue Behaviour of Steel Structures Strengthened with Ultra High Modulus CFRP Plates written by Chao Wu and published by . This book was released on 2012 with total page 598 pages. Available in PDF, EPUB and Kindle. Book excerpt: Originated in 1940s, fibre reinforced polymer (FRP) composites are generally characterized by combining high strength and high stiffness fibres with relatively weaker matrices. The extraordinary properties of FRP composites of lightweight, high strength-toweight ratio corrosion resistance, potentially high overall durability and tailorability enable them to be used in areas where the conventional materials might be restricted. Approximately forty years ago, the concept of using bonded FRP composites as a means to maintain aging metallic aircraft was instituted in Australia. And this technique was promoted by research pioneers like Dr. Alan Baker, Dr. Francis Rose, Dr. Rhys Jones and Dr. L.J. Hart-Smith, etc. However, the retrofitting applications of FRP composite in civil infrastructures were much delayed until late 1980s, when the use of FRP composites for retrofitting concrete structures was initiated in Swinzerland by Urs Meier and his colleagues at the Swiss Federal Laboratories for Material Testing and Research (EMPA). Nowadays, the use of FRP for retrofitting of concrete structures is becoming more widely accepted in practice. Since last decade, the experiences in USA, the UK, Japan and Switzerland have showed great potential for FRP to be used in the retrofitting of steel structures. One of the most promising applications is to restore or improve the fatigue performance of steel members by externally attached FRP composites. The carbon fibre reinforced polymer (CFRP) seems to perform better in fatigue strengthening with higher elastic modulus comparing to other FRP composites, like glass fibre reinforced polymer (GFRP) or aramid fibre reinforced polymer (AFRP). In the previous studies on the fatigue retrofitting of steel structures, the elastic moduli of adopted CFRP composites are generally lower than 300 GPa. In addition, most CFRP composites were thinner than the corresponding steel adherents, resulting in a relatively lower CFRP stiffness. Therefore, the further improvement in the fatigue performance of retrofitted steel structures relies on the increase of either the elastic modulus or the thickness of CFRP composite. Fortunately, with the development of the FRP manufacturing industry, the mechanical properties of CFRP composites have gained considerable improvement. Unidirectional CFRP sheet with a modulus of 640 GPa and pultruded CFRP plate with a modulus of 460 GPa are now commercially available. The researchers in Civil Engineering Department of Monash University in Melbourne have conducted extensive research on the retrofitting of steel members using the CFRP sheets with a modulus of 640 GPa. The high modulus CFRP sheet shows great potential in improving the fatigue performance of cracked steel members. Comparing to CFRP sheeting system, CFRP plate of 460 GPa has other benefits for fatigue retrofitting like larger thickness, more convenient installation and better quality control. However, there has been no report on its fatigue retrofitting applications in steel structures. In this thesis, the CFRP plate with a modulus of 460 GPa is named ultra high modulus (UHM) CFRP plate. The issues regarding fatigue strengthening of cracked steel members using this UHM CFRP plates are investigated, including (1) the bond behaviour between this UHM CFRP plate and steel under static loading and fatigue loading conditions; (2) fatigue behaviour of non-welded cracked steel plates with UHM CFRP plate strengthening and (3) fatigue behaviour of welded cracked steel connections with UHM CFRP plate strengthening. Experimental, numerical and analytical approaches have been resorted.The first part of the thesis presents the static bond behaviour between this UHM CFRP plate and steel. A series of tests was conducted on the CFRP-steel double strap joints. Experimental results, including bond strength, effective bond length, failure modes, stress and strain distribution along the bond line were reported. Theoretical models were proposed for the prediction of bond strength and effective bond length of CFRP-steel double strap joint. Finite element models were built to simulate the tests. It was found that the failure mode of double strap joint was dependent on the adhesive properties. CFRP delamination and CFRP rupture were observed for specimens with Araldite 420 adhesive, whereas specimens with Sikadur 30 only experienced CFRP delamination. The effective bond lengths of Araldite and Sikadur specimens were 100~120mm and 70~100 mm respectively. The proposed theoretical and finite element models agreed well with the experimental results.The second step of the research is to understand the effect of fatigue loading on the bond between UHM CFRP plate and steel. Similar CFRP-steel double strap joints were prepared and tested under fatigue loading. These joints were tensioned to failure after enduring a pre-set number of fatigue cycles at various load ratios and then compared with those joints subjected to static tension alone. It was found that the same failure mode of CFRP delamination was observed from visual inspection for all specimens. Unexpectedly, limited effects of fatigue loading on the bond between CFRP and steel were identified. Microscopic investigation was conducted and the failure mechanism was explained by a "fatigue damage zone" concept.The third part of the PhD study is to investigate the effectiveness of the UHM CFRP plate on preventing fatigue crack propagation and extending the fatigue life of cracked steel plates. Steel plates with through thickness centre crack were repaired with UHM CFRP plates with various strengthening configurations. The effects of CFRP bond length, bond width, and bond locations were investigated. The experimental results showed that the fatigue crack propagation was largely delayed by the CFRP strengthening. The fatigue life was increased up to 7 times more than un-strengthened steel plates. Finally, it was recommended that it be better to attaché CFRP as close to the crack as possible, so that better strengthening effect can be achieved. Following the experimental study, fracture mechanics was introduced to analyse the stress intensity factor (SIF) of cracked steel plate considering the CFRP reinforcement. A simplified mode I SIF formula was proposed for CFRP strengthened steel plates, which provided a method for quick assessment of CFRP strengthening efficiencies.Finally, a series of fatigue tests were conducted on welded steel joints with CFRP strengthening. The experimental results were compared with those of non-welded CFRP strengthened steel plates. The effects of welding and stress concentration due to the weld attachment on CFRP strengthening effectiveness were investigated. It was found that the strengthening efficiency of UHM CFRP plate was largely decreased due to the welding and attachment. The experimental results suggested that it be better to attaché CFRP on the welding side as close to the crack as possible to achieve longer fatigue life. Based on the experimental, numerical and theoretical studies, recommendations were provided for the application of fatigue strengthening techniques using this UHM CFRP plate. Future research in the fatigue behaviour of composites reinforced steel structures was also identified.
