Case study on the strengthening of Routh Creek Bridge using externally bonded CFRP under adverse conditions

With increasing knowledge and technological advances, earthquake resistance regulations are undergoing updates. Buildings that existed before the new regulations will need to be reviewed. If it turns out that the results of the review do not meet the requirements of the new regulations, then one solution is retrofitting. Fiber reinforced polymer (FRP) has emerged as a viable alternative for reinforcing reinforced concrete components. The advantages of FRP are that it is corrosion resistant, lighter than steel reinforcement, high tensile strength, and easy application. FRP can be in the form of rods, grids, or sheets. There are generally 5 types of FRP, namely glass fiber reinforced polymer (GFRP), aramid fiber reinforced polymer (AFRP), carbon fiber reinforced polymer (CFRP), basalt fiber reinforced polymer (BFRP), and natural fiber reinforced polymer (NFRP). This research will present CFRP as reinforcement for reinforced concrete beam and column connections. Variations in CFRP length in the column were analyzed using MIDAS FEA. 1 models of reinforced concrete beam and column connections were made without CFRP and 7 models with CFRP. The analysis results show that CFRP can increase the load capacity carried by the connection by up to 25% and there is a limit to the length of CFRP use due to the limited capacity of concrete. Abstrak Dengan bertambahnya pengetahuan dan kemajuan teknologi, peraturan tahan gempa mengalami pembaruan. Bangunan yang sudah ada sebelum peraturan baru perlu ditinjau kembali. Jika ternyata hasil peninjauan tidak memenuhi persyaratan dari peraturan baru, maka salah satu solusinya adalah perkuatan. Fiber reinforced polymer (FRP) telah muncul sebagai alternatif yang layak untuk perkuatan komponen beton bertulang. Kelebihan FRP adalah tahan korosi, lebih ringan dibandingkan perkuatan baja, kuat tarik yang tinggi, dan aplikasi yang mudah. FRP dapat berbentuk rod, grid, ataupun lembaran. FRP secara umum ada 5 jenis, yaitu glass fiber reinforced polymer (GFRP), aramid fiber reinforced polymer (AFRP), carbon fiber reinforced polymer (CFRP), basalt fiber reinforced polymer (BFRP), dan natural fiber reinforced polymer (NFRP). Penelitian ini akan menampilkan CFRP sebagai perkuatan pada hubungan balok dan kolom beton bertulang. Variasi panjang CFRP pada kolom dianalisis menggunakan MIDAS FEA. Dibuat 1 model sambungan balok dan kolom beton bertulang tanpa CFRP dan 7 model dengan CFRP. Hasil analisis menunjukkan CFRP dapat meningkatkan kapasitas beban yang dipikul sambungan hingga 25% dan ada batas panjang penggunaan CFRP karena terbatasnya kemampuan beton.

This paper focuses on the interlaminar shear behavior of basalt fiber reinforced polymer (FRP) laminates impregnated with epoxy and vinyl ester resins as well as hybrid basalt and carbon FRP laminates. Meanwhile, the interlaminar shear behavior of carbon and E-glass FRP laminates was also studied for comparison. The experiments were conducted according to the ASTM-D-2344 standard, and the failure modes, load–deformation (L–D) relationships, and interlaminar shear stress to normalized deformation relationships of various FRP laminates were analyzed. The differences in interlaminar shear behavior among different fibers and resins were identified. The fracture surfaces of the laminate specimens with different fibers were examined by scanning electron microscopy. Furthermore, the hybrid effect on interlaminar shear behavior was discussed and the interlaminar shear strength was predicted based on above analysis. The results show that the L–D relationships of FRP laminates can be classified into three types, which are determined by the interlaminar shear strength between fiber layers and the resin as well as by the failure modes. The interlaminar shear strength of basalt FRP with vinyl ester resin is higher than that of the glass FRP but less than that of the carbon FRP. The adoption of epoxy resin and the hybridization of basalt and carbon fibers can enhance the interlaminar shear strength of basalt FRP. In addition, the scanning electron microscopy images of fracture surfaces of the laminate specimens confirm the differences of interlaminar behavior of various composites. The hybrid effect on the interlaminar shear behavior is reflected in the integration of both advantages of basalt FRP and carbon FRP in the interlaminar shear stress to nominal deformation relationship, which results in both higher interlaminar shear strength at the cracking and the final stages. Finally, the interlaminar shear strength of different FRP laminates can be accurately predicted by the proposed model.

<p>Strengthening concrete structures with FRP(fiber reinforced polymer) have grown to be a widely used method over most parts of the world today, which FRP was developed in 1960's. A method to apply prestressing force to FRP is developed newly in these days, which can use the maximum performance of FRP materials. This study investigated the flexural behavior of simply supported Reinforced Concrete(R/C) beams strengthened with Prestressed Near Surface Mounted (NSM) CFRP(carbon fiber reinforced polymer) . CFRP plate and rod were used for flexural strengthening. Prestressing level changed from 0 % of CFRP tensile strength to 50 %. Any mechanical device has not been used to maintain the prestress during testing. Static four point loading tests are conducted for eleven R/C beams strengthened with Prestressed Near Surface Mounted (NSM) CFRP and Non-prestressed Near Surface Mounted (NSM) CFRP. The test shows that the beams with prestressed NSM CFRP exhibited a higher yielding load and a higher ultimate load, compared to the beams with non-prestressed NSM CFRP and the control beams. Beams strengthened by CFRP rod failed due to fiber rupture of the FRP in the groove, but beams strengthened by CFRP plate failed due to concrete cover separation.</p>

Creating sustainability and public infrastructure is a fairly recent subject the engineering community has been debating. Introducing new building materials or introducing new structural designs is a strategy for constructing buildings that have long-term reliability and low maintenance requirements. Fiber-reinforced polymers (FRP) are one of the innovative approaches in the field of civil engineering that offer promising results in this regard. In order to maximize the usage of FRP forms, researchers suggested the development of hybrid structural structures by mixing composite materials with standard materials, such as concrete, to enhance the stability, ductility and buckling resistance of single FRP members. Nevertheless, these composite solutions need more preliminary research to prove its feasibility due to the complexity and large range of hybrid components. However, as there is a current shortage of compulsory codes for the design of composite structures and consequently FRP-concrete members, accurate predictive models need to be created. Thus, the present work aims at testing the structural efficiency of hybrid slabs made of CFRP sheets under a concrete layer in bending and shear configurations by carrying an experimental and analytical analysis. Using Carbon Fiber Reinforced Polymer (CFRP) bonded with resin is usual to strengthen concrete slabs or other elements. This thesis introduces a novel technological definition of thin CFRP-concrete unidirectional hybrid slabs. In bending part, experimental quasi-static three-points bending tests and modal analysis tests were carry out to analyze the influence of the connection systems on the dynamic response. Moreover, the corresponding analytical methodology to calculate their response are presented. Four different connection strategies between CFRP sheet and concrete were tested. These included flexible mesh embedding and particle-based frictional enhancement. The maximum bending moment, the evolution of the neutral axis, the comparison between external moment (calculated from applied load) and internal moment (calculated from strain distribution), the CFRP-concrete interface shear stress, and the evolution of the vertical displacement at the loading point are the main results obtained from the tests. In shear part, this work investigates the shear behavior of hybrid slabs that used different types of particles and/or a flexible high strength fabric to connect both materials: concrete and CFRP sheet. Several pure-shear experiments have been carried out to characterize the interface shear response of these hybrid elements. These increase the experimental database on CFPR-concrete shear connection systems. Experimental results showed that the improvement resulting from fabric embedding is far more significant than other tested connection elements at increasing the shear connection strength between the parts of the composite slabs. Results are divided with technological and scientific contributions. The feasibility of using CFRP sheets in hybrid unidirectional slabs instead of steel sheets is the main technological contribution, which also offers the following advantages: lighter weight and resistance to corrosion. Qualitative and quantitative analysis of the CFRP-concrete connection alternatives point out that combining adherence and frictional based strategies is the most promising method. An analytical method for the modelling of concrete slabs with CFRP was developed. In function of full cross-section interaction some equations for bending ultimate limit states were suggested. The possibility of using simpler formulas for quantifying interlayer slip effects was analyzed in assessing deflections, flexural stiffness, bending efficiency and normal and shear stress distributions. The proposed analytical method was able to capture the structural behavior and performance of the specimens. La creació d'infraestructura pública i sostenible és un tema de plena actualitat que la comunitat de l¿enginyeria ha estat debatent des de fa anys. Els polímers reforçats amb fibra (FRP) són un dels materials innovadors en el camp de l'enginyeria civil que ofereixen resultats prometedors en aquest sentit. Per maximitzar l'ús de formes de FRP s'estan desenvolupant estructures híbrides barrejant materials compostos amb materials tradicional, com el formigó, per millorar l'estabilitat, ductilitat i resistència al vinclament de membres individuals de FRP. A més, com hi ha una escassetat actual de codis obligatoris per al disseny d'estructures compostes i, en conseqüència, elements de formigó FRP, cal crear models predictius necessaris perquè es puguin estandarditzar. Abordar els problemes esmentats anteriorment és essencial per augmentar la introducció de materials compostos avançats en tipus comuns d'obres i construccions públiques. Així, el present treball té com a objectiu provar l'eficiència estructural de lloses híbrides de làmines de CFRP amb una capa de formigó, en configuracions de flexió i tallant, mitjançant la realització d'un anàlisi experimental i analític. L'ús de polímers reforçats amb fibra de carboni (CFRP) unit amb resina és habitual per reforçar lloses i altres elements de formigó. Aquesta tesi introdueix una definició tecnològica innovadora de lloses híbrides unidireccionals de formigó-CFRP de làmina prima. A la part de flexió es van realitzar assajos experimentals de flexió quasiestàtics, de tres punts, i assajos d'anàlisi modal per analitzar la influència dels sistemes de connexió en la resposta dinàmica. Així mateix, es presenta la metodologia analítica corresponent per calcular la seva resposta. Es van provar quatre estratègies de connexió diferents entre la làmina de CFRP i el formigó. Aquestes van incloure l¿embegut de malla flexible en el formigó i la millora de la fricció basada en partícules. El moment flector màxim, l'evolució de l'eix neutre, la comparació entre el moment extern (calculat a partir de la càrrega aplicada) i el moment intern (calculat a partir de les deformacions), l'esforç tallant de la interfície CFRP-formigó i l'evolució del desplaçament vertical en el punt de càrrega, són els principals resultats obtinguts de les proves. Aquest treball investiga el comportament rasant de lloses híbrides on els materials de CFRP i formigó es van connectar mitjançant diferents tipus d'agregats i tèxtils flexibles d'alta resistència. S'han dut a terme experiments de tall pur per caracteritzar la resposta de la interfície d'aquests elements híbrids. Aquests assajos augmenten la base de dades experimental sobre sistemes de connexió de tall de formigó-CFPR. Els resultats experimentals van mostrar que la tela embeguda produeix una millora en l'augment de la resistència estructural de manera molt més significativa que amb altres sistemes de connexió provats. La viabilitat d'utilitzar xapes de CFRP en lloses unidireccionals híbrides, en lloc de xapes d'acer, és la principal aportació tecnològica que, a més, ofereix els següents avantatges: menor pes i major resistència a la corrosió. Els anàlisis qualitatiu i quantitatiu de les alternatives de connexió CFRP-formigó assenyalen que la combinació d'estratègies basades en adherència i fricció és el mètode més prometedor. Així mateix, es va desenvolupar un mètode analític per a la modelització de lloses de formigó amb CFRP. En funció dels principis de la interfície completa, es suggereixen equacions per calcular els estats límit últims. La possibilitat d'utilitzar fórmules més simples per quantificar els efectes de lliscament entre capes va ser analitzada en l'avaluació de deflexions, rigidesa de flexió, eficiència de flexió i distribucions d'esforços normals i tallants. El mètode analític proposat va ser capaç de capturar el comportament estructural i el rendiment mecànic de les mostres. La creación de infraestructura pública y sostenible es un tema de plena actualidad que la comunidad de ingenieros ha estado debatiendo desde hace años. La introducción de nuevos materiales de construcción o la introducción de nuevos diseños estructurales es una estrategia eficiente para construir edificios que tengan fiabilidad a largo plazo y requisitos de bajo mantenimiento. Los polímeros reforzados con fibra (FRP) son uno de los materiales innovadores en el campo de la ingeniería civil que ofrecen resultados prometedores en este sentido. Para maximizar el uso de formas de FRP se están desarrollando estructuras híbridas mezclando materiales compuestos con materiales estándar, como el hormigón, para mejorar la estabilidad, ductilidad y resistencia al pandeo de miembros individuales de FRP. Sin embargo, estas soluciones compuestas necesitan más investigación preliminar para demostrar su viabilidad debido a la complejidad y la amplia gama de componentes híbridos. Además, como existe una escasez actual de códigos obligatorios para el diseño de estructuras compuestas y, en consecuencia, elementos de hormigón FRP, es necesario crear modelos predictivos precisos para que puedan estandarizarse. Abordar los problemas mencionados anteriormente es esencial para aumentar la introducción de materiales compuestos avanzados en tipos comunes de obras y construcciones públicas. Así, el presente trabajo tiene como objetivo probar la eficiencia estructural de losas híbridas de láminas de CFRP con una capa de hormigón, en configuraciones de flexión y cortante, mediante la realización de un análisis experimental y analítico. El uso de polímeros reforzados con fibra de carbono (CFRP) unido con resina es habitual para reforzar losas y otros elementos de hormigón. Esta tesis introduce una definición tecnológica novedosa de losas híbridas unidireccionales de hormigón-CFRP de lámina delgada. En la parte de flexión se realizaron ensayos experimentales de flexión cuasi estáticos, de tres puntos, y ensayos de análisis modal para analizar la influencia de los sistemas de conexión en la respuesta dinámica. Asimismo, se presenta la metodología analítica correspondiente para calcular su respuesta. Se probaron cuatro estrategias de conexión diferentes entre la lámina de CFRP y el hormigón. Estos incluyeron el embeber una malla flexible en el hormigón y la mejora de la fricción basada en partículas. El momento flector máximo, la evolución del eje neutro, la comparación entre el momento externo (calculado a partir de la carga aplicada) y el momento interno (calculado a partir de la distribución de deformaciones), el esfuerzo cortante de la interfaz CFRP-hormigón y la evolución del desplazamiento vertical en el punto de carga, son los principales resultados obtenidos de las pruebas. En el estudio del cortante, este trabajo investiga el comportamiento rasante de losas híbridas donde los materiales de CFRP y hormigón se conectaron mediante diferentes tipos de agregados y textiles flexibles de alta resistencia. Se han llevado a cabo experimentos de corte puro para caracterizar la respuesta de la interfaz de estos elementos híbridos. Estos ensayos aumentan la base de datos experimental sobre sistemas de conexión de corte de hormigón-CFPR. Los resultados experimentales mostraron que la tela embebida produce una mejora en el aumento de la resistencia estructural de manera mucho más significativa que con otros sistemas de conexión probados. Los resultados de la tesis se dividen en contribuciones de tipo tecnológico y científico. La viabilidad de utilizar chapas de CFRP en losas unidireccionales híbridas, en lugar de chapas de acero, es el principal aporte tecnológico, que además ofrece las siguientes ventajas: menor peso y mayor resistencia a la corrosión. Los análisis cualitativo y cuantitativo de las alternativas de conexión CFRP-hormigón señalan que la combinación de estrategias basadas en adherencia y fricción es el método más prometedor. Asimismo, se desarrolló un método analítico para el modelado de losas de hormigón con CFRP. En función de los principios de la conexión completa se sugieren ecuaciones conceptuales para calcular los estados límite últimos. La posibilidad de utilizar fórmulas más simples para cuantificar los efectos de deslizamiento entre capas fue analizada en la evaluación de deflexiones, rigidez de flexión, eficiencia de flexión y distribuciones de esfuerzos normales y cortantes. El método analítico propuesto fue capaz de capturar el comportamiento estructural y el rendimiento mecánico de las muestras.

The use of corrosion free fibre reinforced polymer (FRP) composites as reinforcement to concrete is currently being seen as a promising option to generate durable concrete structures. However, there exists very little credible information about its field application and performance. This paper describes the Joffre Bridge project, in Sherbrooke (Québec, Canada), over the St-François River, where Carbon Fibre Reinforced Polymer (CFRP) was used as reinforcement for a portion of the concrete deck slab. The bridge consists of five longitudinal spans with lengths varying from 26 to 37 m. Each span has a concrete deck supported by five steel girders at 3.7 m. A part of the concrete deck slab (7.3 × 11.5 m) and a portion of the traffic barrier and the sidewalk were reinforced with Carbon (CFRP) and Glass Fibre Reinforced Polymer (GFRP) reinforcement. The bridge was extensively instrumented with many different types of gauges, including integrated fibre optic sensors (FOS) into FRP reinforcement. The performance of the bridge had been assessed under static and dynamic loading using calibrated heavy trucks. Moreover, structural design and construction details of the bridge and instrumentation were performed. The results from calibrated field tests on the bridge are presented in this paper.Key words: concrete bridge deck, FRP reinforcement, fibre optic sensors (FOS), field calibrated tests, performance monitoring.

Engineers have proposed relocating externally bonded strengthening fiber reinforced polymer (FRP) material from the unprotected exterior of the concrete to the protected interior. This technology is known as near-surface mounted (NSM) strengthening. In NSM reinforcement, the FRP is surrounded by concrete on three sides so the bond and damage problems associated with externally bonded FRP strengthening systems are reduced or eliminated. This paper presents experimental results from 12 full-scale concrete beams strengthened with NSM carbon FRP (CFRP) strips. Three companion unstrengthened specimens were also tested to serve as a control. Experimental variables include three different ratios of steel reinforcement and two different ratios of CFRP reinforcement. Yield and ultimate strengths, flexural failure modes, and ductility are discussed based on measured load, deflection, and strain data. Test results show measurable increases in yield and ultimate strengths in all beams strengthened with CFRP as well as predictable nominal strengths and failure modes. Force transfer between the CFRP, epoxy grout, and surrounding concrete was able to develop the full tensile strength of the CFRP strips. Energy and deflection ductilities were reduced for CFRP strengthened beams. Future research needs are addressed.

Unreinforced masonry (URM) walls are prone to a brittle failure when subjected to out-of-plane and in-plane forces caused by seismic events. Fiber Reinforced Polymer (FRP) materials offer an economical and viable solution for the seismic retrofit of URM to increase their resistance to in-plane and out-of-plane forces. This paper presents the results of an experimental program that aimed to determine the in-plane shear performance of unreinforced concrete masonry walls strengthened with different levels of externally applied Carbon and Glass FRP composites. All the wall specimens were tested under in-plane cyclic loading with increasing intensity. The test set-up configuration consisted of double-height walls loaded at the mid-height. A total of five specimens (one control, two carbon, and two glass) were tested with increasing amounts of FRP and different layouts. The FRP was applied to one face of the walls to simulate field conditions where access to only one face of the wall is possible. The ultimate shear strength, lateral deformation, and peak load were compared for all tested walls. In most cases, failure occurred in either the masonry or the epoxy and in no case did the FRP reach its ultimate capacity. The experimental results demonstrated that a significant increase in the in-plane shear capacity of masonry can be achieved for walls retrofitted with Glass and Carbon FRP. Ultimate shear strengths of the walls were compared with those determined using the design model in ACI 440.7R for predicting the in-plane shear capacity of CMU walls. A good correlation between experimental results and theoretical predictions was observed.

In recent years, Fiber Reinforced Polymers (FRPs) have gained significant popularity over traditional materials for enhancing the shear strength of Reinforced Concrete (RC) beams, particularly when they are deficient in shear or prone to shear failure. FRPs are advanced composite materials widely used to retrofit existing RC beams and improve the shear resistance of new ones. Among these, Carbon Fiber Reinforced Polymers (CFRP) stand out due to their lightweight nature, exceptional tensile strength, superior corrosion resistance, and ease of application in construction. Shear failure is commonly observed under seismic and impact loading conditions, making CFRP reinforcement a complex but essential solution. Although extensive research has been conducted in this field, existing studies remain insufficient. This study focuses on strengthening RC beams in shear using CFRP. A total of six simply supported RC beams (150 mm × 200 mm × 1800 mm) were subjected to four-point bending tests. The primary objective is to enhance the shear load-bearing capacity of the beams. The research involved testing RC beams reinforced with CFRP, including two control specimens and four beams wrapped with a single layer of CFRP. The wrapping configurations included two beams with 356 mm CFRP wrapping and two with 508 mm wrapping. The average maximum load capacity of the unwrapped beams was recorded at 84.74 kN, while those wrapped with 356 mm CFRP reached 120.46 kN. Meanwhile, the beams wrapped with 508 mm CFRP demonstrated an increased load capacity of 155.815 kN. Cracking was observed earlier in the unwrapped beams compared to those strengthened with CFRP, indicating improved structural performance. The failure patterns of the beams varied, particularly between those with and without CFRP wrapping. This study highlights CFRP's potential and provides a foundation for future research on optimizing its configurations for infrastructure rehabilitation.

In the present work, first an attempt has been made to prepare carbon, glass and carbon-glass fibre-reinforced polymer composites, and later, machining of these composites is done on abrasive water jet machine (AWJM) to compare and optimize the machining parameters. Actually, the carbon fibre-reinforced polymer (CFRP) composites, glass fibre-reinforced polymer (GFRP) composites and carbon-glass fibre-reinforced polymer (CGFRP) composites are prepared through vacuum bagging process by using epoxy resin as the polymer matrix. The machining experiments are conducted to analyse the effects of the predominant machining parameters, i.e. cutting speed rate, feed rate and stand-off distance on the required machining characteristics, i.e. surface roughness (Ra), kerf top width (kw) and material removal rate (MRR). The range of values of each parameter is set at three different levels, and Taguchi’s L9 orthogonal array is used to design factors so that all the interactions between the response variables and machining variables can be investigated. Based on the experimental values, second-order regression equations are fitted between each of the response parameters and the machining parameters using Minitab 18 software. The equations are then optimized by defining the three equations of Ra, kw and MRR as the three objectives of a multi-objective optimization problem (MOOP) using a multi-objective optimization algorithm called Elitist Non-dominated Sorting Genetic Algorithm (NSGA-II). Single best compromise solutions with respect to the MOOPs of GFRP, CFRP and CGFRP composites are also determined from the Pareto optimal solutions obtained by NSGA-II. Finally, confirmation tests are conducted on specimens of GFRP, CFRP and CGFRP composites machined at their corresponding optimum parameters given by the GA. It is observed that the optimum values of Ra, kw and MRR of all the optimization problems are closer to the corresponding experimental values of confirmation tests.

Extreme environmental temperatures are considered amongst many potential sources of infrastructural disfunctioning. This phenomenon emerges severely when it comes to the adoption of fibre reinforced polymer (FRP) in strengthening civil infrastructures due to the vulnerability of one FRP constituent, viz. polymer matrix, and most critically, the interfacial adhesive layer to extreme exposures. Accordingly, the main concern of the research program described in this thesis is in characterizing the bonding aspects between steel adherends and carbon fibre reinforced polymer (CFRP) at predefined non-ambient temperatures from both extremes, viz. subzero and elevated thermal exposures. In this research, the basic material and geometrical configuration of the experimental specimens is wet lay-up CF130RP and CF530RP composite reinforcement bonded to steel plates in double-strap joint configuration. Extensive literature reviews on the effect of extreme thermal exposures on different FRP strengthened real-life and small scale structural members were conducted. However, it is shown that most of published research is highlighting the synergistic detrimental effects within the durability context, in general. In addition, much more insight is paid in studying FRP strengthened concrete structures compared to steel substrata. Another distinguished feature in past studies is the scatter and divergence in behavioural trends of the non-ambient exposure FRP joints and the tendency to generalize those trends on all CFRP-steel joints without displaying adequate emphasis on the key roles played by the mechanical and thermal attributes of CFRP components, individually. In the experimental program, a new fabricating procedure of the composite double-strap joint was devised in an attempt to optimize the quality control and thus maximize the reliability of the results. Three different commercially available epoxide resins and two different-moduli carbon fibres were involved in the production of composite joints. All specimens were sUbjected to direct tensile testing at their predetermined thermal exposures after concluding their corresponding thermal stabilization procedure. Mixed-mode failure (i.e. either two or three patterns) was the prominent experimental failure pattern within almost all specimens. The outcome of the experimental research has emphasized the key effect of CFRP constituents, viz. the adhesive (i.e. epoxy) and CF reinforcing fibres, on the joints capacities, failure patterns, and CFRP strain and stress distributions, at all experimented temperatures. The theoretical and numerical validations of the experimental results were reasonably good in terms of all of the aforementioned parameters and at both ambient and extreme thermal exposures. Some experimental strain-capturing practices were highlighted as possible sources of divergence from theoretical and numerical models which was confined only to the vicinity of both bondlength lap ends, and at load levels much higher than normal service loads of the joints. The well-established stress-based method for predicting joint capacities in conjunction with triggering failure pattern from FE models was implemented by applying the suitable failure criteria. This method which was investigated previously, mainly in terms of ambient thermal exposures, has proved its effectiveness in predicting failure loads for the current extreme-exposures composite joints.

The aim of this study is to experimentally evaluate the damage mechanisms occurring in the adhesive-bonded regions of glass fiber-reinforced polymer (GFRP) and carbon fiber-reinforced polymer (CFRP) composites, which are widely used in marine and offshore wind turbine applications, under environmental conditions. In particular, this study focuses on the degradation caused by long-term seawater exposure and its effects on the bending behavior and load-carrying capacity of adhesive joints. For this purpose, the specimens were prepared in accordance with ASTM D5868-01, using 7-layer GFRP and 8-layer CFRP laminates. Single-lap adhesive joints were fabricated. To simulate marine environmental conditions, the single-lap adhesive joints were immersed in natural seawater obtained from the Aegean Sea (22 °C temperature and 3.3-3.7% salinity) for 1, 2, and 3 months in separate containers. Three-point bending (3PB) tests were performed on specimens representing marine applications, while four-point bending (4PB) tests were conducted on specimens representing offshore wind turbine blade structures. The results quantitatively revealed the influence of seawater on adhesive-bonded composite joints. In 3PB tests, the reductions in the Young's modulus of GFRP specimens after 1, 2, and 3 months of exposure were measured as 5.94%, 8.90%, and 12.98%, respectively. For CFRP specimens, degradation was more limited, with corresponding reductions of 1.28%, 3.39%, and 3.74%. A similar trend was observed in 4PB tests representing offshore wind turbine applications, where GFRP joints exhibited modulus reductions of 3.15%, 6.42%, and 9.45%, while CFRP joints showed reductions of 1.29%, 2.62%, and 3.48% for the same exposure durations. Overall, the findings demonstrate that CFRP composites exhibit more stable mechanical behavior under environmental exposure, whereas GFRP structures undergo more pronounced performance losses, particularly in moisture- and salt-rich environments. These results highlight the critical importance of material selection for long-term durability in offshore composite structures. The outcomes of this study contribute to a better understanding of the damage processes occurring in composite adhesive joints under environmental conditions and provide a scientific basis for developing more reliable design and material selection strategies in both the marine and wind energy sectors.

This paper presents the tension and bond properties of commercially available Aramid fibre reinforced polymer (AFRP) and carbon fibre reinforced polymer (CFRP) rods and their uplift and sustained loading behaviour as ground anchor tendons. Variables for the tests were tendon type and constituent, grout type, and bond or fixed anchor length. Test results indicated that the tension properties of fibre reinforced polymer (FRP) rods were close to the reported data. The surface geometry of FRP rods and the properties of filling grouts influenced the pullout behaviour and bond strength of grouted FRP rods. CFRP Carbon Fiber Composite Cable and Leadline anchors had a higher uplift capacity but lower creep displacement than AFRP Arapree and Technora anchors. The tested CFRP monorod and FRP multirod anchors with a 1000 mm fixed anchor length exhibited an acceptable uplift behaviour according to existing codes. Creep behaviour appeared to control the long-term uplift capacity of prestressed FRP ground anchors. The recommended working load for post-tensioned FRP ground anchors is 0.40 fpu for AFRP rods and 0.50fpu for CFRP rods, where fpu is the ultimate load or strength of the anchor tendon.Key words: FRP, tendon, bond stress, anchorage, grouted anchor, fixed anchor length, free anchor length, slip, creep.

In the recent construction industry, Fiber reinforced polymers (FRPs) have been considered to be an innovative material to repair and strengthen damaged structures. It is because FRPs have many beneficial characteristics, such as corrosion resistance, a high tensile strength-to-weight ratio, non-conductivity and design flexibility. As a demand of FRPs has increased, many researches on behavior of the structures which were externally strengthened with FRPs have been conducted. However, researches on time-dependant behavior of the structures have not been conducted yet. In order to provide improved serviceability to reinforced concrete (RC) members, the behavior of the RC members strengthened with FRPs under sustained loads should be investigated. This paper presents a series of long-term experiments and deformation-recovery experiments. For the long-term experiments, three RC beams were fabricated and two of the beams were strengthened with a carbon fiber reinforced polymer (CFRP) plate and a glass fiber reinforced polymer (GFRP) plate respectively. The beams were placed under sustained loads for about 550 days. After the 550 days, all of the beams were unloaded for the measurement of deformation recovery. The deflection and strains of rebar and FRP reinforcements were measures for about 60 days. As the result of long-terms experiment, the beams strengthened with CFRP plate showed a better performance in terms of deflection and strains of rebar and CFRP plate. Moreover, the beam with CFRP plate showed a higher deformation recovery and residual strength than the other beams.

Results are presented from an experimental investigation into the performance of 20-ft-long reinforced concrete (RC) T-girders strengthened in shear using epoxy-bonded bidirectional carbon fiber reinforced polymer (CFRP) fabric. The aim was to evaluate and gain insight into the effectiveness of shear strengthening of large-scale girders with externally bonded CFRP under a low shear span condition. Four series of tests, corresponding to stirrup spacings of 5.5, 8, 16, and 24 in, were considered. Each series of girders included control specimens with no CFRP wrap and specimens retrofitted in shear with 1, 2, and 3 layers of CFRP wrap. Results indicate that for unwrapped specimens, values for nominal shear predicted by ACI underestimated, by 40-80%, the shear resistance of beams developing arch action, such as those considered herein. For wrapped specimens, the maximum shear force as well as the midspan deflection generally increased with the number of CFRP layers. The optimum number of layers to achieve the maximum gain in shear resistance was found to depend on the internal shear steel reinforcement provided. The effective CFRP strain used to calculate the contribution of the CFRP to the shear capacity was correlated to the total shear reinforcement ratio consisting of steel stirrups and CFRP wrap. Retrofitting RC girders in shear with CFRP wrap also increased the ductility. Experimental evidence shows an optimum combination of CFRP layers and steel stirrups exists for a maximum increase in ductility.

Reinforced concrete structures are very commonly used in buildings because they are cheaper than the steel structures. But in reality, many concrete structures are damaged, so there are several ways to overcome this problem, by providing reinforcement with Fiber Reinforced Polymer (FRP) and reinforcement with steel plates. Each type of reinforcements has its advantages and disadvantages. In this study, researchers discuss the comparison between flexural strength of reinforced concrete beam using steel plates and Fiber Reinforced Polymer (FRP). In this case, the researchers use Carbon Fiber Reinforced Polymer (CFRP) and Glass Fiber Reinforced Polymer (GFRP) as external reinforcements. The dimension of the beams is 15 x 25 cm with the length of 320 cm. Based on the analytical results, the strength of the beam with CFRP is 1.991 times its initial, GFRP is 1.877 times while with the steel plate is 1.646 times. Based on test results, the strength of the beam with CFRP is 1.444 times its initial, GFRP is 1.333 times while the steel plate is 1.167 times. Based on these test results, the authors conclude that beam with CFRP is the best choice for external reinforcement in building technology than the others.