Fiber Reinforced Polymer Repair Research Articles

Seismic performance of FRP-repaired RC piers after blast loading

Aiming to evaluate the effectiveness of fiber-reinforced polymer (FRP) repair on the seismic performance of blast-damaged reinforced concrete (RC) piers, the field test and numerical simulation were conducted. Firstly, a successive field explosion test, carbon FRP (CFRP) repair, and lateral cyclic loading test were performed on two 1/2-scale RC pier specimens. The test data including the incident overpressure-time histories of blast wave, damage profiles and lateral force-displacement relationships of pier specimens, etc. were comprehensively recorded and discussed. By comparing with the previous blast-damaged pier specimen, the negative maximum force and ductility of CFRP-repaired pier were increased by 97 % and 44.9 % after 1.0 kg TNT explosion, respectively. Then, an integrated numerical simulation approach based on explicit-implicit switching and full restart algorithms was proposed and validated in predicting the dynamic and quasi-static behaviors of RC piers under successive blast loading, CFRP repair, and lateral cyclic loading. Finally, a prototype RC pier was designed and the suicide vest bomb (TNT equivalence of 9 kg) specified by the Federal Emergency Management Agency was selected as the threat of contact explosion. The influences of FRP type, repair height, and number of FRP layer on restoring the seismic performance of the blast-damaged pier were further discussed. It indicates that, (i) CFRP is more effective than glass FRP and aramid FRP; (ii) increasing the repair height could not significantly improve the seismic performance of pier; (iii) the number of FRP layer has significant effect, e.g., the positive and negative maximum forces after 4-layer CFRP repair are improved by 9.4 % and 45.3 % compared to the unrepaired pier, respectively. The present study could provide a helpful reference for assessing the FRP repair effectiveness on the seismic performance of blast-damaged RC bridge piers.

Finite Element Analysis (FEA) of Fiber-Reinforced Polymer (FRP) Repair Performance for Subsea Oil and Gas Pipelines: The Recent Brief Review (2018-2022)

Fiber-reinforced polymer (FRP) materials are used to reinforce and repair subsea pipelines in the oil and gas (O&G) industry due to their great strength-to-weight ratio as well as corrosion resistance. The extreme environmental conditions that subsea pipelines must endure include high pressure, high temperature, as well as corrosion. Modelling the effects of these conditions on the repaired pipeline can be challenging, and inaccuracies in modelling the underwater environment can lead to incorrect predictions regarding the repaired pipeline's behaviour. The finite element method (FEM)’s capabilities, as well as applications, are examined in this work. FEM is being used in place of time-consuming processes and conventional codes since they have demonstrated their strength as prediction tools. This article provides information on the to better understand the accuracy and reliability of the FEA modelling techniques used to simulate the behaviour of the FRP repair system under different operating conditions. The descriptions focus on the many types of composite fibres and the qualities that come from their components. Related document gathering was conducted from 2018-2022 and research on 53 papers were downloaded and acquired from the Scopus and Science Direct database. The review also discusses the insight into the practical implementation of finite element analysis (FEA) modelling involves understanding how FEA is used to solve real-world problems. Moreover, the findings show that by diversifying the FRP materials used in the repair design, the overall performance of the repaired pipeline can be optimized, leading to increased safety and reliability in subsea O&G operations. Also, the scope for future studies.

A semi-empirical model for bond strength between FRP composites and concrete

An accurate estimate of fibre-reinforced polymer (FRP)–concrete bond is essential for a successful FRP repair. The present work aims at developing a semi-empirical model employing a large database (about 500 data points) collected from various literature works. In the beginning, an iterative regression process was followed to establish the trend in behaviour (of each key parameter against bond strength) and decide on insignificant ones. Then, the different equations were merged and manipulated into a simplified model with three regression constants. These were determined based on two-thirds of the database points using the statistical software SPSS. The key parameters involved in the final simplified model included concrete properties (compressive strength and maximum aggregate size) and mechanical and geometric characteristics of the FRP composites (axial stiffness and bond width and length). The proposed model showed a high fit of the regression database at 0.88 coefficient of determination (R2) with a very limited number of outliers. Moreover, the accuracy of prediction by the present model of the validation database far exceeds that of all well-known semi-empirical and empirical models. The sensitivity of the present model to the changes in the key parameters confirms the trend in behaviours reported in the various experimental works and models.

Design considerations for prefabricated composite jackets for structural repair: Parametric investigation and case study

Prefabricated fiber-reinforced polymer (FRP) repair systems are becoming popular for structural repair because FRPs superior resistance to corrosion and weathering. Several parameters impact the effectiveness of this type of repair, including the structural continuity provided by the joining system and grout properties. This study numerically investigated the effects of these critical design parameters to generate new knowledge and understand fundamental structural behaviour of a prefabricated composite repair system. The results reveal that the effective transverse tensile strength of FRP joint should be as low as 20% of the jacket strength for structural repairs. Moreover, grout stiffness dictated the stress transfer between the core and outer jacket. Increasing the compressive strength of the grout delayed grout cracking and degradation, accompanied by a rapid increase in FRP joint strain. Lastly, numerical simulation of a corroded steel column in an actual bridge shows that the application of the FRP jacket improves the strength capacity by 320%, which is 85% higher than that of the conventional FRP repair system. This study provides useful information for optimally designing and effectively using prefabricated composite jackets for structural repairs.

Assessment of the effectiveness of wood pole repair using FRP considering the impact of climate change on decay and hurricane risk

Electric power distribution systems are vulnerable to disruption due to severe weather events, especially hurricanes. Such vulnerability is expected to increase over time due to the impact of climate change on hurricanes and the decay of wood poles that support the distribution lines. This study investigates the effectiveness of using fiber-reinforced polymer (FRP) sleeve to reinforce wood poles subjected to decay and hurricane hazard to restore their lost strength and extend their effective service life. The potential impact of climate change on the pole decay rate and the intensity and frequency of hurricanes is also considered. The optimal FRP repair time based on the structural reliability of the poles is also determined. Three locations with varying climates are chosen to evaluate and compare the results: Miami, Charleston, and New York City. The results show that in all three locations, the application of the FRP sleeve can more than double the service life of the pole depending on the time of the repair. The results also show that climate change significantly increases the vulnerability of the pole. The probability of failure of the pole at the end of the 21st century under RCP8.5 emission scenario in Miami, Charleston, and New York City increase by about 30%, 70%, and 73%, respectively, compared to a no climate change scenario. If climate change is only assumed to affect the decay of the pole, i.e., no change in hurricane hazard intensity, the corresponding increases in failure probability are 5%, 22%, and 20% in Miami, Charleston, and New York City, respectively. This implies that most of the impact of climate change on pole failure risk is due to the increase in hurricane intensity. The impact of climate change on decay is found to be comparatively small. It increases with time as variation in temperature and precipitation becomes more prominent towards the end of the 21st century. The optimization results show that the optimal FRP repair time depends on how the FRP affects the pole's decay rate. If the FRP can significantly slow down the wood decay rate, the optimal time of repair is at the beginning of the pole's life cycle. If the FRP has no impact on the wood decay rate, it is better to repair the pole after significant decay has occurred.

Mechanical and Shrinkage Behaviors of Ductile Fiber-Reinforced Polymer Repair Mortar

Repair mortar (RM) with dense texture and high anti-crack is cost-effective for application onto the surface of concrete structure to effectively delay the detachment of concrete protective layer and the corrosion of steel bars. Here, the effects of ductile fiber and polymer latex on the flexural strength (ft), compressive strength (fc), bond strength (fb), and shrinkage rate (δr) of fiber-reinforced polymer repair mortar (FP-RM) were comprehensively studied. Results show, the individual doping of polymer latex can improve the ft, fb, and the toughness (the ft/fc ratio) of P-RM, and the fb is increased by 75.78% with respect to the plain mortar, which imply polymer ingredient is essential to P-RM. Some ductile fibers individual dosage also can enhance the ft, fc, and δr of F-RM, respectively; When the polymer latex and ductile fiber are simultaneously doped into the FP-RM mortar together, the ft and fb of FP-RM can be increased up to 9.4MPa, and 2.52MPa, respectively, in tandem with 40.54% reduction of δr, showing superior synergy effect.

Strengthening and Retrofitting of RC Beams Using Fiber Reinforced Polymers

Abstract Reinforced Cement Concrete (RCC) Structures are bound to lose its strength while in service due to various causes. Rehabilitation restores the health and service life of the structures. Fiber Reinforced Polymer (FRP) composites overcome most of the limitations of conventionally practiced repair techniques.The Fiber Reinforced Polymer (FRP) application is a effective method to repair and strengthen structures that have become structurally weak over their life span. FRP repair systems provide an economically viable alternative to traditional repair systems and materials. Among the various fibers, Glass Fibers (GF) is widely used in FRP. Strengthening of RC structural elements using externally bonded GFRP composite is an effective method to increase the structural performance under both service and ultimate load conditions. Restoring or upgrading the strength of beams using GFRP sheet can result in increased strength and stiffness.

Comparative study on the behaviour of different infill materials for pre-fabricated fibre composite repair systems

Prefabricated fibre-reinforced polymer (FRP) composite jacket is now becoming an effective repair system for deteriorating piles and columns exposed to marine environment. This system works by providing grout infills between the annulus of the existing structure and the composite jacket. Few studies are however available on the optimal grouting materials that can effectively transfer the stresses between the existing structure and the FRP jacket. This study is investigating the effect of cementitious, concrete and epoxy-based grout infills on the structural behaviour of pre-fabricated glass-FRP (GFRP) tubes. The considered grouts have compressive strength and modulus of elasticity ranging from 10 MPa to 70 MPa and from 10 GPa to 35 GPa, respectively. The experimental results showed that the behaviour of the composite repair system is highly dependent on the modulus of elasticity and the compressive strength of the grout infill. The brittle failure behaviour of the cementitious and epoxy grouts led to localised failure in the FRP repair system while the progressive cracking and crushing of the concrete infill resulted in effective utilisation of the high strength properties of the composite materials. Theoretical analysis of the overall compressive behaviour has also been conducted and showed very good agreement with the experimental results.

Bearing Capacity Calculation and Fiber-reinforced Polymer Repair of Corroded Beam-slabs in a Wharf

Corrosion of steel reinforcement bars is a common problem for high-pile wharf in service, with the aim of solving this problem, a method to calculate the actual bearing capacity of corroded beam-slabs is proposed, in which the rate of loss of area and the reduction in strength of steel bars due to corrosion are considered. Taking Zhanjiang Port as an example, the actual bearing capacity of corroded beam slabs is calculated and is compared with that found under normal service conditions. For repair of corroded beam-slabs, a method in which fiber-reinforced polymer (FRP) bars partly replace the steel bars is proposed, and the basic assumptions and method of calculation for this mixed-reinforcement components are discussed.

Bearing Capacity Calculation and Fiber-reinforced Polymer Repair of Corroded Beam-slabs in a Wharf

Bearing Capacity Calculation and Fiber-reinforced Polymer Repair of Corroded Beam-slabs in a Wharf

Repair of shear-deficient and sulfate-damaged reinforced concrete beams using FRP composites

Reinforced concrete structures often demonstrate nonstructural cracking caused by the action of sulfates from external sources. These cracks are signs of concrete damage that reduces the flexural and shear capacity of reinforced concrete structural elements and require therefore immediate attention. In this paper, the potential of using advanced composite materials in repairing shear deficient reinforced concrete prototype beams that are damaged by a sulfate cyclic treatment to a predetermined level is investigated. Prototype sulfate-damaged beams were repaired using varying configurations of (carbon and glass) fiber reinforced polymer (FRP) sheets or strips. Experimental data on shear strength capacity, stiffness, deflection, FRP strain, crack opening and mode of failure of the repaired beams were obtained, and compared with those of control, and sulfate-damaged ones. The results confirmed that FRP composites applied to shear spans not only enhanced the shear capacity but also improved deflection characteristics, stiffness, toughness, profitability index, crack resistance, performance factor, and FRP composites strain. However, the effectiveness of the present FRP repair schemes in terms of load capacity was negatively affected by the level of sulfate damage. Finally, a suitable analytical model was developed and examined for the prediction of FRP contribution to shear capacity of sulfate-damaged beams.

Performance of FRP-Strengthened RC Beams with Surface Out-Of-Flatness

Fiber reinforced polymer (FRP) has become increasingly popular for the repair and retrofit of reinforced concrete structures. Surface condition of the substrate, in particular its flatness, plays a significant role on the performance of retrofitted structure. This paper reports on the effects of out-of-flatness as a surface defect on the flexural performance of FRP repair systems. The experimental program includes a total of nineteen specimens with two different FRP repair systems (wet lay-up and precured), and two different levels of surface unevenness in the form of peaks or valleys. Tests showed that the peaks on concrete surface, in the range studied, did not have a significant effect on the performance of FRP systems. However, valleys or depressions deeper than 1.6 mm over a length of 305 mm (1.38 × 10−4 mm−1 curvature) could reduce the strength of FRP systems. Typical failure mode was FRP debonding observed in both FRP repair systems. Test results and threshold recommendations were verified using a nonlinear finite element analysis. Bond-dependent coefficient for various surface flatness levels were analyzed and compared with the results available in the literature.

Fatigue strength of fibre-reinforced-polymer-repaired beams subjected to mild corrosion

Infrastructure corrosion is an expensive problem worldwide. In the case of reinforced concrete (RC) structures, corrosion reduces the steel cross sectional area and thus decreases the capacity of the corroded RC members. The expansion of the corroded steel also induces tensile stresses in the concrete causing the concrete cover to crack and spall, thus reducing the bond capacity between concrete and steel. This paper reports on a research program conducted at the University of Waterloo that studied the effect of corrosion on flexural and bond fatigue strength. The effect of the addition of fibre-reinforced-polymer (FRP) sheets on the fatigue life of corroded RC beams was also assessed. Eighteen beams (152 mm × 254 mm × 2000 mm) were tested in two groups, with each group consisting of three sets of tests. Group F was designed to study the fatigue flexural behaviour; the repaired beams in this group were strengthened with a flexural FRP sheet along their tension side and confined by intermittent U-shaped FRP sheets along their length. Group B was designed to study the fatigue bond behaviour; hence, the repaired beams in this group were confined with U-shaped FRP sheets in the anchorage zone. The variables in each group were the percentage of corrosion (0% and 5% theoretical mass loss), the load range, and the use or omission of a FRP repair method. Results showed that a mild level of corrosion (5% theoretical mass loss) caused on average 10% and 20% reductions in flexural and bond fatigue strength, respectively. Strengthening the corroded beams with FRP sheets enhanced the fatigue behaviour of the beams. In both groups, the fatigue strength was on average 15% higher than that of the corroded unrepaired beams.Key words:corrosion, fibre-reinforced-polymer (FRP) sheets, fatigue strength, steel–concrete bond, flexural performance, durability.

Fiber-Reinforced Polymer Repair and Strengthening of Structurally Deficient Piles

The poor durability of conventional repairs has led to increased interest in the application of fiber-reinforced polymers (FRP) for repairing corroded concrete structures. The availability of resins that can cure under wet conditions has made it possible to consider FRP for repairing partially submerged piles. An overview is provided of a recently completed multiyear study that investigated this problem. In the project, laboratory studies were conducted to determine the effectiveness of FRP in corrosion repair, and two field demonstration projects were completed. A simple, new design method was developed and used for the design of the FRP wrap in the demonstration projects. Some of the issues related to pile repair are addressed, with particular attention to the newly developed design method.

FRP repair of concrete structures: performance in cold regions

This paper summarises work conducted at Queen's University on the performance of concrete members strengthened with Fibre-Reinforced Polymer (FRP) sheets when exposed to cold regions conditions. The freeze-thaw resistance of the FRP-concrete bond is studied by considering small-scale beams (100×150×1200 mm) strengthened with different types of FRP. The results show that no significant bond deterioration occurs when the specimens are exposed to up to 300 freeze-thaw cycles. Recent results that consider the combined effects of freeze-thaw and fatigue loading are discussed. The freeze-thaw behaviour of FRP confined concrete cylinders is also presented. The results show no significant deterioration of the FRP wrapped cylinders due to freeze-thaw exposure even when the cylinders are under sustained load. The low temperature behaviour of concrete beams strengthened with prestressed CFRP sheets is also investigated. In particular, the prestress losses due to low temperature and long-term loading are quantified.

Evaluation of corrosion activity in FRP repaired RC beams

Abstract This paper presents the results of an experimental study to evaluate the corrosion activity in reinforced concrete beams repaired with fibre reinforced polymer (FRP) sheets. Ten beam specimens (152 × 254 × 3200 mm) were constructed. One specimen was neither strengthened nor corroded to serve as a reference. Three specimens were corroded and not repaired. The remaining six beams were corroded and repaired with FRP sheets. The FRP sheets were applied after the main reinforcing bars were corroded to a 5.5% mass loss. Following the FRP repair, some specimens were subjected to further corrosion to investigate their post-repair performance. The corrosion activity was evaluated using non-destructive and destructive techniques. The non-destructive techniques included half-cell potential measurements. The destructive techniques included evaluation of the mass loss of the main reinforcing bars. The experimental results showed that the corrosion potential decreased with the progress of corrosion, and the FRP repair caused a higher rate of decrease in the corrosion potential with time than that observed when FRP was not provided. Results showed that mass loss of the main reinforcing bars due to corrosion was reduced by up to 16% because of FRP repair.

Sprayed FRP repair of simulated impact in prestressed concrete girders

The sprayed fiber reinforced polymer (FRP) technique consists of discontinuous glass fibers sprayed onto the concrete surface concurrently with a vinyl ester resin. In order to evaluate the potential for sprayed FRP repair on impact damaged girders, a series of three AASHTO Type II girders, 13.3 m in length, were tested in flexure. The intent was to determine whether the sprayed FRP technique was capable of restoring the damaged girders to their original undamaged strength and stiffness. One of the girders acted as a control specimen and was tested in an undamaged condition. The remaining two were subjected to simulated impact damage at midspan, including the rupturing of prestressing strands. Of the two damaged girders, the first represented the “damage control” condition and was tested without being repaired. The other was repaired using the sprayed FRP rehabilitation technique, and succeeded in reaching the target rehabilitation goal of 95% of the original undamaged girder strength.

FRP confined concrete columns: Behaviour under extreme conditions

Abstract The behaviour of concrete columns wrapped with fibre reinforced polymer (FRP) materials when exposed to several extreme conditions is evaluated. Cold regions environments, FRP repair of corroding reinforced concrete columns, and fire resistance are all considered. For the cold regions exposure, FRP wrapped cylinders (152 × 305 mm) are exposed to temperatures as low as −40 °C or to up to 300 cycles of freeze-thaw (−18 °C to +15 °C). The combination of freeze-thaw exposure with sustained loading is also examined. For FRP wrapping of corroding reinforced concrete columns, the results of tests on cylinders and larger-scale circular columns (300 × 1200 mm) are presented. The specimens are corroded and then wrapped with FRP sheets. The rate of corrosion is monitored both before and after wrapping. The final extreme condition that is considered is fire exposure. Tests on full-scale reinforced concrete columns (400 × 3800 mm) exposed to a standard fire are described and discussed. Overall, the results demonstrate that FRP confined concrete columns tested in concentric axial compression have adequate performance under several extreme conditions such as low temperature, freeze-thaw action, corrosion of internal reinforcement, and fire exposure.

Postrepair Fatigue Performance of FRP-Repaired Corroded RC Beams: Experimental and Analytical Investigation

This paper presents the results of an experimental and analytical study of the fatigue performance of corroded reinforced concrete (RC) beams repaired with fiber-reinforced polymer (FRP) sheets. Ten RC beam specimens (152×254×3,200 mm) were constructed. One specimen was neither strengthened nor corroded to serve as a reference; three specimens were corroded and not repaired; another three specimens were corroded and repaired with U-shaped glass FRP sheets that wrapped the cross section of the specimen; and the remaining three specimens were corroded and repaired with U-shaped glass FRP sheets for wrapping and carbon-fiber-reinforced polymer (CFRP) sheets for flexural strengthening. The FRP sheets were applied after the main reinforcing bars were corroded to an average mass loss of 5.5%. Following FRP repair, some specimens were tested immediately to failure, while the other repaired specimens were subjected to further corrosion before being tested to failure to investigate their postrepair (long-term) per...

Fire insulation schemes for FRP-strengthened concrete slabs

In recent years, widespread deterioration of civil infrastructure has been a catalyst for the application of externally bonded fiber reinforced polymer (FRP) sheets for reinforcement or strengthening of concrete structures. However, the performance of these FRP strengthening systems in fire is a serious concern, and this represents a critical obstacle to the widespread implementation of FRP repair techniques in buildings. This paper presents the results of an experimental and numerical study conducted to investigate the performance in fire of insulated FRP-strengthened concrete slabs. Four different supplemental fire insulation systems are examined through standard fire tests, and a numerical model to predict member behavior in fire is presented. Model predictions are shown to satisfactorily agree with test data. The results of this study indicate that appropriately designed and insulated FRP-strengthened concrete slabs are capable of achieving satisfactory fire endurances.