Modified Epoxy for Fibre Reinforced Polymer Strengthening of Concrete Structures

Fibre-Reinforced Polymer (FRP) is a preferable material for repairing concrete structure due to excellent material properties and effective installation cost over the long-term maintenance of structures. The successful application of FRP strengthening system very much depends on the bond between the concrete substrate and the FRP material using epoxy adhesive. Epoxy acts as a bridge to transfer stress from the concrete to the FRP material. The use of wet lay-up technique to apply FRP onto concrete structure requires epoxy to undergo a curing process normally referred to as cold curing. This paper intends to give a review of the problems with cold-cured epoxy and its effect on structural performance. Cured epoxy is characterised as brittle; therefore, modifications of epoxy are required to toughen the epoxy to suit the purpose of repairing a concrete structure. The methodological approaches from previous studies on modified epoxy were collected and reviewed in this paper. This review also offers some important insights regarding the use of sustainable materials, as well as recommendations for new epoxy in the future. &nbsp

Investigation of the constancy of the MWCNTs on the fibres surface for manufactured self-sensing composites

This the author accepted manuscript. The fial version is available from Elsevier via the DOI in this recordDifferent methods have been used to deposit the multi-walled carbon nanotubes (MWCNTs) onto the fibre surface to fabricate self-sensing composites. However, the constancy of the MWCNTs onto the fibre surfaces during infusion processing still unclear. In this study, we have deposited MWCNTs onto the glass fibre surface by two methods to investigate the state of MWCNTs during and after epoxy infusion processing. In the first method, the glass fibres were directly coated with the MWCNTs and in the second method, an adhesive was applied to coat the glass fibre surface before depositing the MWCNTs over it. Rectangular specimens for both types of self-sensing composites were cut from different specified zones and then tested. The results showed that the self-sensing composites with adhesively bonded MWCNTs exhibited more consistent in their properties than the composites where no adhesive was used. In addition, the electrical resistance of both types of self-sensing composites was monitored during the epoxy infusion process. The results showed that the electrical resistance was not obviously affected for composite with non-adhesive bonded MWCNTs and was high for the specimens where the MWCNTs were not adhesively bonded. Moreover, the numerical study was also conducted and the results indicated that the relationship between the volume fraction of the MWCNTs and their tunnelling distance was an inverse. The current study proves evidence that the properties of the self-sensing composites are strongly dependent on the method that used to deposit the MWCNTs on the surface of glass fibres layers.Iraqi Ministry of Oi

Smart Textiles for Strengthening of Structures

This paper presents results of mechanical tests on a prototype of an innovative structural strengthening in form of self-monitoring fabric. Smart textile employs carbon fibers conductivity for measuring strains while monitoring changes of electric resistance under increasing load. A general solution was tested in a series of calibrating tests on strengthening of small size concrete slabs. Promising results of simple specimen, has encouraged the research team to perform the next tests using mastered carbon fibre reinforced fabric. Main tests were performed on natural scale RC beam. Smart textile proved its efficiency in both: strengthening and monitoring of strains during load increase. New strengthening proposal was given 10% increase of loading capacity and the readings of strain changes were similar to those obtained in classical methods. In order to calibrate the prototype and to define range limits of solution usability, textile sensor was tested in areas of large deformations (timber beam) and as well as very small strains (bridge bearing block). In both cases, the prototype demonstrated excellent performance in the range of importance for structural engineering. This paper also presents an example of use of the smart strengthening in situ, in a real life conditions.info:eu-repo/semantics/publishedVersio

A Review of Fibre Reinforced Polymer Structures

This paper reviews Fibre Reinforced Polymer (FRP) composites in Civil Engineering applications. Three FRP types are used in Structural Engineering: FRP profiles for new construction, FRP rebars and FRP strengthening systems. Basic materials (fibres and resins), manufacturing processes and material properties are discussed. The focus of the paper is on all-FRP new-build structures and their joints. All-FRP structures use pultruded FRP profiles. Their connections and joints use bolting, bonding or a combination of both. For plate-to-pate connections, effects of geometry, fibre direction, type and rate of loading, bolt torque and bolt hole clearance, and washers on failure modes and strength are reviewed. FRP beam-columns joints are also reviewed. The joints are divided into five categories: web cleated, web and flange cleated, high strength, plate bolted and box profile joints. The effect of both static and cyclic loading on joints is studied. The joints’ failure modes are also discussed

Seismic and Thermal Retrofitting of Masonry Buildings with Fiber Reinforced Composite Systems: A State of the Art Review

Old masonry buildings represent the largest part of traditional constructions. Generally, they are both seismically vulnerable and thermally dispersive. Therefore, the need for seismic and thermal retrofitting aimed at reducing their vulnerability and environmental impact has motivated research efforts towards sustainable retrofitting solutions. This study presents a literature review of the approaches currently available for masonry retrofitting. Specifically, it highlights the use of fiber in textile form i.e., Textile Reinforcement Mortar (TRM), as Fiber Reinforced Polymer (FRP) and natural fibers (animal and plant sources) to masonry retrofitting. In addition, specific attention is devoted to the integrated (structural and thermal) fiber-based integrated retrofitting techniques that are becoming very important in the last years

CAREER: Framework for Integrating Embedded Sensors in Durability Analysis of FRP Composites in Civil Infrastructure

The CAREER proposal will develop a framework to characterize durability of composites in civil infrastructure by integrating fiber-optic embedded sensors with damage mechanics models and life prediction methods. To tackle this problem, a combined analytical and experimental methodology is proposed, as follows: 1) Integrate embedded sensors in composites fabrication by VARTM and filament winding; 2) Implement strain, temperature, moisture and chemical degradation fiber-optic sensors; 3) Evaluate the embedded sensor system with controlled damage; 4) Develop a damage mechanics model and life-prediction methodology for durability analysis based on interrogating senors; 5) Assess reliability of sensor data and scale to composite structures (bridge decks and pipe walls); and 6) Validate the durability methodology and synthesize into a health-monitoring protocol. The educational approach is two-fold encompassing student recruitment and advanced graduate education. First, and educational collaboration is being developed with an applied technology center at a high school in Maine. The objective is to introduce high school students to the engineering experience by collaborating with civil engineering juniors in a composite bridge design and fabrication project. Second, an advanced graduate course on composites in civil engineering will be developed

Fibre-Reinforced Polymer (FRP) in Civil Engineering

Construction produces a third of global carbon emissions. These emissions cause global warming and contribute to climate emergency. There is a need to encourage use of sustainable and eco-friendly materials to effectively deal with climate emergency. Fibre reinforced polymer (FRP) is an eco-friendly material with low carbon footprint. FRP composites in civil engineering are mainly used in three applications: (1) FRP profiles in new-build; (2) FRP reinforcing bar in concrete members and (3) FRP in repair and rehabilitation of existing structures. This chapter presents basic properties of constituent materials (fibres and polymer resins), mechanical properties of FRP bars, strengthening systems and profiles, manufacturing processes and civil engineering applications of FRP composites. Durability, sustainability and recycling of FRP composites are also discussed

A Review of Fibre Reinforced Polymer Bridges

Fibre reinforced polymer composites (FRP) offer various benefits for bridge construction. Light-weight, durability, design flexibility and fast erection in inaccessible areas are their unique selling points for bridge engineering. FRP are used in four bridge applications: (1) FRP rebars/tendons in concrete; (2) repair and strengthening of existing bridges; (3) new hybrid-FRP bridges with con-ventional materials and (4) all-FRP composite new bridges made entirely of FRP materials. This paper reviews FRP bridges, including all-FRP and hybrid-FRP bridges. FRP bridges’ history, ma-terials, processes and bridge components – deck, girder, truss, moulded parts and cables/rebars are considered. This paper does not discuss use of FRP as an architectural element and a strengthening system. While lack of design codes, material specifications and recycling are the major challenges, the high cost of FRPs still remains the most critical barrier to the progress of FRPs in bridges

Static and dynamic response of RC beams strengthened with NSM C/GFRP rods

openNegli ultimi anni è stato dimostrato che la tecnica di rinforzo Near Surface Mounted (NSM) rappresenta una valida alternativa ai metodi di rinforzo convenzionali, come le fasciature esterne (metodo Externally Bonded). Potenzialità, vantaggi ed applicazioni sono stati studiati negli ultimi 20 anni cercando di ottimizzare il sistema ed i parametri che lo influenzano. È interessante approfondire il tema sia dal punto di vista statico, evidenziando la non validità dell’ipotesi di conservazione delle sezioni piane, che si manifesta a causa dello scorrimento tra FRP e resina, che per semplicità non viene mai preso in considerazione dai modelli analitici proposti in letteratura, che dal punto di vista dinamico, che consente di analizzare l’andamento delle frequenze proprie di vibrazione, per monitorare l’efficacia del rinforzo e come agisce il grado di danneggiamento. Durante questo lavoro di ricerca sono state effettuate prove statiche e dinamiche su campioni di travi in cemento armato rinforzati con barre in CFRP e GFRP mediante tecnica NSM. Lo scopo del progetto è proprio quello di analizzare gli effetti delle differenti tipologie di rinforzo applicate. Le prove statiche a flessione sono consistite nell’applicazione di cicli di carico e scarico, questi test hanno consentito di definire il comportamento dei campioni di trave anche in presenza di fessurazione del calcestruzzo e di individuare diversi livelli di danno. Dopo ogni step di carico sono state effettuate le prove dinamiche in vibrazione libera che hanno consentito di osservare come agisce il rinforzo. Sono stati osservati anche i modi di rottura delle travi. Le risposte del campione non rinforzato sono quindi state confrontate con quelle dei campioni rinforzati, il comportamento è stato analizzato anche attraverso dei modelli teorici. Infine, è stato sviluppato un modello agli elementi finiti dei campioni di trave in modo da validare i risultati ottenuti sperimentalmente.The Near-Surface Mounted (NSM) strengthening technique has proven, in recent years, as a valid alternative to the conventional strengthening methods, like the externally bonded (EB) technique. In the last two decades its potential and its advantages, as well as its applications, has been studied, trying to optimize the construction system and the parameters that influence it. However, it is interesting to deepen the topic both in static, highlighting the non-conservation of the flat section, due to the bond-slip effect between FRP rod and resin, which, for simplification has never been taken into consideration by analytical models proposed in literature, both in dynamic key, which allows, by studying the trend of proper frequencies of vibration, to understand the effectiveness of the reinforcement and how different types of damage affect it. Therefore, in this research work, static and dynamic tests were performed on RC beams strengthened with NSM CFRP and GFRP rods, which still need to be investigated. The aim of the research is to analyze the effects of different types of strengthening. Bending tests with cycles of loading until failure are carried out, these tests allowed to define the behavior of beam specimens, even in presence of damage, and to generate different damage degrees, due to cracking of concrete. At each step of load, dynamic analysis, by free vibration test, allows monitoring the effectiveness of the reinforcement at different damage degrees. Failure modes of beam models are also analyzed. A comparison between the responses of the unreinforced and reinforced models is presented; the behavior of beam specimens was also analyzed by theoretical models. In the end, a finite element analysis of beam models has been developed, in order to validate the results obtained by the experimental research.INGEGNERIA CIVILE, EDILE E ARCHITETTURAopenVecchietti, MARIA VITTORI