Mitigation of the blast risk associated with terrorist attacks and accidental explosions threatening critical infrastructure has become a topic of great interest in the civil engineering community, both in Canada and abroad. One method of mitigating blast risk is to retrofit vulnerable structures to resist the impulsive effects of blast loading. A comprehensive re-search program has been undertaken to develop fibre reinforced polymer (FRP) retrofit methodologies for structural and non-structural elements, specifically reinforced concrete slabs and walls, subjected to blast loading. The results of this investigation are equally valid for flexure dominant reinforced concrete beams subject to blast effects. The objective of the research program was to generate a large volume of research data for the development of blast-resistant design guidelines for externally bonded FRP retrofit systems. A combined experimental and analytical investigation was performed to achieve the objectives of the program. The experimental program involved the construction and simulated blast testing of a total of thirteen reinforced concrete wall and slab specimens divided into five companion sets. These specimens were subjected to a total of sixty simulated explosions generated at the University of Ottawa Shock Tube Testing Facility. Companion sets were designed to study one- and two-way bending, as well as the performance of specimens with simply-supported and fully-fixed boundary conditions. The majority of the specimens were retrofitted with externally bonded carbon fibre reinforced polymer (CFRP) sheets to improve overall load-deformation characteristics. Specimens within each companion set were subjected to progressively increasing pressure-impulse combinations to study component behaviour from elastic response up to inelastic component failure. The blast performance of companion as-built and retrofitted specimens was quantified in terms of measured load-deformation characteristics, and observed member behaviour throughout all stages of response. The results show that externally bonded FRP retrofits are an effective retrofit technique to improve the blast resistance of reinforced concrete structures, provided that debonding of the composite from the concrete substrate is prevented. The test results also indicate that FRP retrofitted reinforced concrete structures may survive initial inbound displacements, only to failure by moment reversals during the negative displacement phase. The experimental test data was used to verify analytical techniques to model the behaviour of reinforced concrete walls and slabs subjected to blast loading. The force-deformation characteristics of one-way wall strips were established using inelastic sectional and member analyses. The force-deformation characteristics of two-way slab plates were established using commonly accepted design approximations. The response of all specimens was computed by explicit solution of the single degree of freedom dynamic equation of motion. An equivalent static force procedure was used to analyze the response of CFRP retrofitted specimens which remained elastic after testing. The predicted maximum displacements and time-to-maximum displacements were compared against experimental results. The analysis indicates that the modelling procedures accurately describe the response characteristics of both retrofitted and unretrofitted specimens observed during the experiment.

Samhället ändras konstant men detta innebär inte bara en förändring för människorna i samhället utan också att nya krav ställs på konstruktionen som brukas av människorna. Många byggnadskonstruktioner kan därmed behöva en förstärkning efter en viss tid. Behovet av en förstärkning kan bero på flera orsaker exempelvis ändrat nyttjande. Det är mer fördelaktigt med en förstärkning av konstruktionen än att den rivs ner och byts ut för att klara av dagens krav. Syftet med detta examensarbete är att undersöka förstärkning av betongkonstruktioner med hjälp av kolfiberkomposit. I rapporten presenteras beräkningar som gjordes för att undersöka tillökningen i böjoch tvärkraftskapacitet efter en utförd förstärkning. Parallellt med beräkningarna kontrollerades och utvecklades befintliga mallar som finns för denna metod. För att kunna uppnå syftet undersöktes två hypotetiska betongkonstruktioner. Ena konstruktionen är en plattramsbro som modellerades i FEM programmet Brigade Standard. Beräkningar på plattramsbron gjordes med avseende på böjande moment. Den andra konstruktionen som undersöktes är en T-balk som är en del utav ett bjälklag. På T-balken granskades tvärkraftskapaciteten innan och efter en utförd förstärkning med kolfiber. I resultatet redovisas mängden kolfiber som erfordras för att uppnå önskad kapacitet hos konstruktionerna. I resultatet redogörs också kapaciteten som uppnås efter kolfiberförstärkningen. / The society changes constantly, but this does not only affect the inhabitants of the society, but also that new demands are made on the construction used by the people. Many constructions may therefore require reinforcement after a certain amount of time. The need for reinforcement may be due many different reasons for example to altered use, corrosion to internal reinforcement or may be due to design errors, accidents or new standards. It is more beneficial to reinforce the structure than to tear it down and replace it to meet current requirements. The purpose of this thesis is to investigate carbon fiber reinforced polymer, CFRP, as a method to strengthen concrete structures. The report presents calculations that were made to investigate the increase in bending and shear capacity after a performed reinforcement. Alongside the calculations, existing templates for this method were checked and developed. In order to achieve the purpose, two hypothetical concrete structures were investigated. One design is a frame bridge modeled in the FEM program Brigade Standard. Calculations on the frame bridge were made with respect to bending. The other construction that was investigated is a T-beam. On the Tbeam, shear capacity was examined before and after reinforced carbon fiber reinforcement. The result present the amount of carbon fiber required to achieve the desired capacity of the structures. The result also describes the capacity achieved after carbon fiber reinforcement.

Fiber reinforced polymer (FRP) composites have been of interest to the structural engineering society since the earliest days of FRP composites industry. The use of such systems has been implemented in both new construction and for repair and rehabilitation of existing structures. Since the 1980s, researchers have developed a significant body of knowledge to use FRP composites in infrastructure applications; however, most of this established knowledge was concentrated on the use of traditional epoxy (EP) systems (epoxy matrix FRPs and epoxy adhesives). FRP composites with polyurethane (PU) matrices and adhesives have recently attracted the attention of a few researchers due to their potential advantages in constructibility and mechanical properties. The deployment of these systems is currently limited by a lack of knowledge on mechanical and durability performance. The objective of this research is to quantify the mechanical behavior of PU composites utilized in externally-bonded repair of common flexural and flexural-axial reinforced concrete systems. In addition, the mechanical performance, strength, and failure modes are compared directly with an epoxy-based composite by subjecting reinforced concrete specimens utilizing each of the matrix types (EP and PU) to the same protocols. The study presented therefore allows an objective comparison (advantages and disadvantages) between the two composite system used for repair and rehabilitation of concrete infrastructure. An experimental research program was designed with different length scales. Small-scale experiments were utilized to characterize the component level properties of the materials and bond to concrete, which include the flexural behavior as well as the pure shear behavior. The results of these small scale experiments were used to calibrate analytical models of the interface behavior between FRP laminate and concrete, and paved the way for the next level of the research which studied the behavior of each composite system at larger scales. The large scale experiments included flexural retrofitting of reinforced concrete girders and retrofitting of circular columns using FRP laminates. The large-scale experimental specimens were mechanically damaged prior to FRP repair and testing, making the testing more appropriate compared to common practice of repairing undamaged specimens.

Metallic utility poles, light poles, and mast arms are intermittently damaged by vehicle collision. In many cases the vehicular impact does not cause immediate failure of the structure, but induces localized damage that may result in failure under extreme service loadings or can promote degradation and corrosion within the damaged region. Replacement of these poles is costly and often involves prolonged lane closures, service interruption, and temporary loss of functionality. Therefore, an in situ repair of these structures is required. This thesis examines the failure modes of damaged metallic poles reinforced with externally-bonded fiber reinforced polymer (FRP) composites. Several FRP repair systems were selected for comparison, and a set of medium and full-scale tests were conducted to identify the critical failure modes. The material properties of each component of the repair were experimentally determined, and then combined into a numerical model capable of predicting global response. Four possible failure modes are discussed: yielding of the unreinforced substrate, tensile rupture of the FRP, compressive buckling of the FRP, and debonding of the FRP from the substrate. It was found that simple linear, bilinear, and trilinear stress-strain relationships accurately describe the response of the composite and substrate components, whereas a more complex bond-slip relationship is required to characterize debonding. These constitutive properties were then incorporated into MSC.Marc, a versatile nonlinear finite element program. The output of the FEM analysis showed good agreement with the results of the experimental bond-slip tests.

Fiber reinforced polymer (FRP) composites have become an attractive alternative to conventional methods for external-strengthening of civil infrastructure, particularly as applied to flexural strengthening of reinforced concrete (RC) members. However, durability of the bond between FRP composite and concrete has shown degradation under some aggressive environments. Although numerous studies have been conducted on concrete members strengthened with FRP composites, most of those studies have focused on the degradation of FRP material itself, relatively few on bond behavior under repeated mechanical and environmental loading. This thesis investigates bond durability under accelerated environmental conditioning of two FRP systems commonly employed in civil infrastructure strengthening: epoxy and polyurethane systems. Five environments were considered under three different conditioning durations (3 months, 6 months, and 1 year). For each conditioning environment and duration (including controls), the following were laboratory tested: concrete cylinders, FRP tensile coupons, and FRP-strengthened concrete flexural members. Numerical investigations were performed using MSC MARC finite element software package to support the outcomes of durability experimental tests. Precise numerical studies need an accurate model for the bond between FRP and concrete, a linear brittle model is proposed in this work that is calibrated based on nonlinear regression of existing experimental lap shear data. Results of tensile tests on FRP coupons indicate that both epoxy and polyurethane FRP systems do not degrade significantly under environmental exposure. However, flexural tests on the FRP strengthened concrete beams indicate that bond between FRP and concrete shows significant degradation, especially for aqueous exposure. Moreover, a protective coating suppresses the measured degradation. Also, experimental load-displacement curves for control beams show excellent agreement with numerical load-displacement curves obtained using the proposed bond iii model. Finally, a bond-slip model is predicted for concrete leachate conditioned beams by matching load-displacement curves for those beams with numerical load-displacement curves.

yes / This paper investigates the feasibility of using artificial neural networks (NNs) to predict the shear capacity of concrete members reinforced longitudinally with fibre reinforced polymer (FRP) bars, and without any shear reinforcement. An experimental database of 138 test specimens failed in shear is created and used to train and test NNs as well as to assess the accuracy of three existing shear design methods. The created NN predicted to a high level of accuracy the shear capacity of FRP reinforced concrete members. Garson index was employed to identify the relative importance of the influencing parameters on the shear capacity based on the trained NNs weightings. A parametric analysis was also conducted using the trained NN to establish the trend of the main influencing variables on the shear capacity. Many of the assumptions made by the shear design methods are predicted by the NN developed; however, few are inconsistent with the NN predictions.

Yes / This paper aims to investigate the flexural behavior of engineered cementitious composite (ECC)-concrete hybrid composite beams reinforced with fiber reinforced polymer (FRP) bars and steel bars. Thirty two hybrid reinforced composite beams having various ECC height replacement ratio and combinations of FRP and steel reinforcements were experimentally tested to failure in flexure. Test results showed that cracking, yield and ultimate moments as well as the stiffness of hybrid and ECC beams are improved compared with traditional concrete beams having the same reinforcement, owing to the excellent tensile properties of ECC materials. The average crack spacing and width decrease with the increase of ECC height replacement ratio. The ductility of hybrid reinforced composite beams is higher than that of traditional reinforced concrete beams while their practical reinforcement ratios are similar. Reinforced ECC beams show considerable energy dissipation capacity owing to ECC’s excellent deformation ability. Considering the constitutive models of materials, compatibility and equilibrium conditions, formulas for the prediction of cracking, yield and ultimate moments as well as deflections of hybrid reinforced ECC-concrete composite beams are developed. The proposed formulas are in good agreement with the experimental results. A comprehensive parametric analysis is, then, conducted to illustrate the effect of reinforcement, ECC and concrete properties on the moment capacity, curvature, ductility and energy dissipation of composite beams. / National Natural Science Foundation of China (51678514, 51308490), the Natural Science Foundation of Jiangsu Province, China (BK20130450), Six Talent Peaks Project of Jiangsu Province (JZ-038, 2016), Graduate Practice Innovation Project of Jiangsu Province (SJCX17-0625), the Jiangsu Government Scholarship for Overseas Studies and Top-level Talents Support Project of Yangzhou University

Diffusion of liquids into and through polymers is an important factor that negatively may influence the durability or lifetime of a polymer structure used in industrial applications. In this work two types of polymers, a liquid crystalline polymer (LCP, Vectra A950) and various thermoset resins as used in fibre reinforced plastics (FRP) process equipment were studied with regard to barrier properties, chemical resistance and long-term performance. LCP are known for their outstanding chemical resistance and barrier properties. FRP used in process equipment may be a cost-efficient solution in chemically aggressive environments where standard carbon or stainless steel cannot be used due to its limited corrosion resistance. Transport properties of typical industrial environments were determined for the LCP and the influence of annealing and orientation was investigated to study whether the barrier properties can be improved. The possibility to use LCP as cost-effective lining for FRP was explored. Special focus was put on the diffusion of water and its effect on long-term transport properties and stability of thermoset resins as the performance of FRP is strongly related to the diffusion of water. The results showed that Vectra A950 was suitable for organic solvent and non-oxidising acid environments. Its transport properties were gravimetrically determined and found to be 10 to 102 times lower than that of a high barrier fluoropolymer of type FEP. The degree of molecular packing increased with annealing time both below and above the melting point. Below the melting point this was – at least – partly due to crystal formation whereas above the melting point other mechanisms were involved. The effects of annealing and orientation on the transport properties in LCP were, however, very small or not significant and probably significantly longer annealing times are required. LCP has potential to be used as lining material for FRP as the use of an LCP-lining substantially reduced the permeability of and the solute sorption in a bisphenol A epoxy-based vinyl ester resin. The bonding strength was improved significantly by a combined abrasive and oxygen plasma treatment. The long-term sorption of water in thermoset resins including bisphenol A epoxy-based vinyl ester, novolac-based vinyl ester, urethane modified vinyl ester and bisphenol A polyester resins was found to increase with exposure time whereas the diffusion coefficient was not significantly affected. It was shown that the presence of water induced relaxation processes that were considered to be the primarily reason for the increase in sorption coefficient in comparison to degradation processes, such as hydrolysis, causing osmotic processes. A general relationship for the estimation of the sorption coefficient at 80ºC in dependence of the water activity and the sorption coefficient at unit activity independent of the resin type was established.

This dissertation is focused on understanding the performance of a particular fiber-reinforced polymeric composite structural beam, a 91.4 cm (36 inch) deep pultruded double-web beam (DWB) designed for bridge construction. Part 1 focuses on calculating the Timoshenko shear stiffness of the DWB and understanding what factors may introduce error in the experimental measurement of the quantity for this and other sections. Laminated beam theory and finite element analysis (FEA) were used to estimate the shear stiffness. Several references in the literature have hypothesized an increase in the effective measured shear stiffness due to warping. A third order laminated beam theory (TLBT) was derived to explore this concept, and the warping effect was found to be negligible. Furthermore, FEA results actually indicate a decrease in the effective shear stiffness at shorter spans for simple boundary conditions. This effect was attributed to transverse compression at the load points and supports. The higher order sandwich theory of Frostig shows promise for estimating the compression related error in the shear stiffness for thin-walled beams. Part 2 attempts to identify the failure mechanism(s) under quasi-static loading and to develop a strength prediction for the DWB. FEA was utilized to investigate two possible failure modes in the top flange: compression failure of the carbon fiber plies and delamination at the free edges or taper regions. The onset of delamination was predicted using a strength-based approach, and the stress analysis was accomplished using a successive sub-modeling approach in ANSYS. The results of the delamination analyses were inconclusive, but the predicted strengths based on the compression failure mode show excellent agreement with the experimental data. A fatigue life prediction, assuming compression failure, was also developed using the remaining strength and critical element concepts of Reifsnider et al. One DWB fatigued at about 30% of the ultimate capacity showed no signs of damage after 4.9 million cycles, although the predicted number of cycles to failure was 4.4 million. A test on a second beam at about 60% of the ultimate capacity was incomplete at the time of publication. Thus, the success of the fatigue life prediction was not confirmed. / Ph. D.

Abstract: Recently, fiber-reinforced polymer (FRP) composite materials have been used in the field of civil engineering constructions especially in corrosive environments. They can be used as internal reinforcement for beams, slabs, and pavements, or as external reinforcement for rehabilitation and strengthening different structures. One of their innovative applications is the concrete-filled FRP tubes (CFFTs) which are becoming an alternative for different structural members such as piles, columns, bridge girders, and bridge piers due to their high performance and durability. In such integrated systems, the FRP tubes act as stay-in-place forms, protective jackets for the embedded concrete and steel, and as external reinforcement in the primary and secondary direction of the structural member. Extensive research was developed on CFFTs as columns, but comparatively limited research was carried out on CFFTs as beams especially those with rectangular sections. The circular sections exhibit magnificent confinement efficiency in case of columns. However, the rectangular sections have higher moment of inertia and flexural stiffness to resist the applied loads and deformations in case of beams. Moreover, the construction and architectural requirements prefer the rectangular section of beams, rather than the circular beams, due to its stability during installation and its workability during connecting to other structural members like slabs and columns. Also, CFFTs that are completely filled with concrete are not optimal for applications governed by pure bending, because the excess weight of the cracked concrete below the neutral axis may increase the transportation and installation cost. This dissertation presents experimental and theoretical investigations on the flexural behaviour of rectangular CFFT beams with steel rebar. These hybrid FRP-concrete-steel tubular rectangular beams contain outer rectangular filament-wound glass-FRP (GFRP) tubes to increase the sectional moment of inertia, to provide flexural and shear reinforcement, and to protect the inner structural elements (concrete and steel) against corrosion. The outer tubes were fully-or-partially filled with concrete and were reinforced with steel rebar at the tension side only. Inner hollow circular or square filament-wound GFRP tubes, shifted toward the tension zone, were provided inside the CFFT beam to eliminate the excess weight of the cracked concrete at the tension side, to confine actively the concrete at the compression side and to act as reinforcement at the tension side. The surfaces of tubes adjacent to concrete were roughened by sand coating to fulfill the full composite action of such hybrid section. Several test variables were chosen to investigate the effect of the outer and inner tubes thickness, fibers laminates, and shape on the flexural behaviour of such hybrid CFFT beams. To fulfil the objectives of the study, twenty-four full-scale beam specimens, 3200 mm long and 305×406 mm2 cross section, were tested under a four-point bending load. These specimens include eight fully-CFFT beams with wide range of tube thickness of 3.4 mm to 14.2 mm, fourteen partially-CFFT beams with different outer and inner tubes configurations, and two conventional steel-reinforced concrete (RC) beams as control specimens. The results indicate outstanding performance of the rectangular fully and partially-CFFT beams in terms of strength-to-weight ratio and ductility compared to the RC beams. The fully-CFFT beams with small tube thickness failed in tension by axial rupture of fibers at the tension side. While, the fully-CFFT beams with big tube thickness failed in compression by outward buckling of the outer tube compression flange with warning signs. The results indicate also that the flexural strength of the fully-CFFT beams was ascending nonlinearly with increasing the tubes thickness until a certain optimum limit. This limit was evaluated to define under-and-over-reinforced CFFT sections, and consequently to define the tension and compression failure of fully-CFFT beams, respectively. The inner hollow tubes act positively in reinforcing the partially-CFFT beams and confining the concrete core at the compression side. The strength-to-weight ratio of the partially-CFFT beams attained higher values than that of the corresponding fully-CFFT beams. Generally, the partially-CFFT beams failed gradually in compression due to outward buckling of the outer tube compression flange with signs of confining the concrete core at the compression side. The inner circular voids pronounced better performance than the square inner voids, however they have the same cross sectional area and fiber laminates. Theoretical section analysis based on strain compatibility/equilibrium has been developed to predict the moment-curvature response of the fully-CFFT section addressing the confinement and tension stiffening of concrete. The analytical results match well the experimental results in terms of moment, deflection, strains, and neutral axis responses. In addition, analytical investigation was conducted to examine the validity of the North American design codes provisions for predicting the deflection response of fully and partially-CFFT beams. Based on these investigations, a new power and assumptions were proposed to Branson’s equation to predict well the effective moment of inertia of the CFFT section. These assumptions consider the effect of the GFRP tube strength, thickness and configuration, in addition to the steel reinforcement ratio. The proposed equations predict well the deflection in the pre-yielding and post-yielding stages of the hybrid FRP-concrete-steel CFFT rectangular beams. / Résumé: Les matériaux composites en polymère renforcé de fibres (PRF) ont récemment été utilisés dans le domaine des constructions de génie civil, en particulier dans les environnements corrosifs. Elles peuvent être utilisées comme une armature interne pour des poutres, dalles et les trottoirs, ou comme une armature externe pour la réhabilitation et le renforcement de différentes structures. L'une de leurs applications novatrices est les tubes de polymères renforcés de fibres remplis de béton (TPFRB ) qui sont en train de devenir une alternative pour divers éléments structuraux tels que les pieux, les colonnes, les poutres et les piliers de ponts en raison de leur haute performance et durabilité. Dans de tels systèmes intégrés, les tubes PRF agissent comme un coffrage permanent, une chemise protectrice pour le béton et l'acier encastrés, et comme une armature externe dans les directions longitudinale et transversale de l'élément structural. La recherche a été concentrée sur les TPRFB comme des colonnes, mais très peu de recherche a été effectué les TPRFB comme des poutres particulièrement celles à section rectangulaire. La section circulaire présente une efficacité de confinement efficace en cas de colonnes. Toutefois, la section rectangulaire a un moment d'inertie plus élevé et une rigidité flexionnelle plus efficace pour résister les charges appliquées et les déformations dans le cas des poutres. Par ailleurs, les travaux de construction et les exigences architecturales préfèrent la section rectangulaire des poutres, plutôt que les poutres circulaires, en raison de sa stabilité pendant l'installation et sa maniabilité lors de la connexion à d'autres membres structuraux comme les dalles et les colonnes. En outre, les poutres TPRFB qui sont complètement remplis de béton ne sont pas optimales pour les applications contrôlées par la flexion pure, puisque le béton fissuré en dessous de l'axe neutre ne contribue pas à la résistance et augmente le poids propre et les coûts de transport et d'installation. Cette thèse présente des études théoriques et expérimentales sur le comportement en flexion de poutres rectangulaires (TPRFB) en béton armé. Ces poutres rectangulaires tubulaires hybrides en PRF-béton-acier sont composées de tubes rectangulaires externes fabriquées par enroulement filamentaire. Ces tubes fournissent un renforcement de flexion et de cisaillement; et protègent le béton armé contre la corrosion. Les poutres peuvent être soient entièrement ou partiellement remplies de béton. Des tubes intérieurs ( de section circulaires ou carrés) en polymères renforcés de fibres de verre (PRFV) sont positionnés dans la zone tendue de la poutre afin de réduire le poids et d’éliminer le béton fissuré en traction. Pour augmenter l'action composite de la section hybride, les surfaces des tubes adjacents au béton ont été rendues rugueuses par enrobage de sable. Plusieurs variables ont été choisis pour étudier l'effet de l’épaisseur des tubes extérieurs et intérieurs, les laminés de fibres, et la forme sur le comportement en flexion de ces poutres hybrides (TPRFB). Pour atteindre les objectifs de l’étude, vingt-quatre échantillons de poutre pleine grandeur, ayant une longueur de 3200 mm et une section transversale de 305×406 mm2, ont été testés sous une flexion à quatre points. Ces échantillons comprennent huit poutres de TPRFB entièrement remplis avec une large gamme d'épaisseur du tube externe de 3.4 mm à 14.2 mm, quatorze poutres de TPRFB partiellement remplis avec différentes configurations de tubes extérieurs et intérieurs, et deux poutres en béton armé conventionnel, comme échantillons de référence. Les résultats indiquent une performance exceptionnelle des poutres rectangulaires de TPRFB entièrement et partiellement remplies en termes du rapport de la résistance sur la masse et de la ductilité par rapport aux poutres en béton armé conventionnel. Les poutres de TPRFB entièrement remplies avec un tube de petite épaisseur ont rompu de façon moins ductile en tension par rupture axiale des fibres. Les poutres de TPRFB entièrement remplies et ayant une grande épaisseur ont rompu de façon ductile en compression par flambage local vers l’extérieur des parois en compression du tube externe. Les résultats indiquent également que la résistance à la flexion des poutres de TPRFB entièrement remplies augmente d’une façon non linéaire avec l'augmentation de l'épaisseur des tubes jusqu'à une certaine limite optimale. Cette limite a été évaluée pour définir les sections TPRFB sous-armées et surarmées et, par conséquent, pour définir la rupture en tension et en compression des poutres de TPRFB entièrement remplies, respectivement. Les tubes creux intérieurs agissent positivement dans le renforcement des poutres de TPRFB partiellement remplies et en confinant le noyau de béton du côté en compression. En général, les poutres de TPRFB partiellement remplies ont rompu en compression par flambage local vers l'extérieur des parois en compression du tube externe. Les vides circulaires intérieurs ont montré une meilleure performance que les vides carrés intérieurs, bien qu’ils aient la même superficie de la section transversale et le même taux de PRF. Une analyse théorique basée sur la compatibilité des déformations d’une section en flexion a été développée pour prédire la réponse moment-courbure de la poutre TPRFB en tenant compte des pourcentages de confinement externe et interne. Les résultats analytiques et les résultats expérimentaux s’accordent en termes de moment, flèche, déformations, et positions de l'axe neutre. En outre, une étude analytique a été menée afin d'examiner la validité des codes de conception nord-américains pour prédire la réponse en flexion des poutres TPRFB. En se basant sur les résultats de ces études, de nouvelles équations ont été proposées pour mieux prédire le moment effectif d'inertie de la section et une nouvelle procédure de conception pour prédire les capacités ultimes. Ces équations considèrent l'effet de la résistance des tubes en PRFV externe et interne que le taux d’armature en acier. En outre, ils prédisent bien la flèche dans les phases avant et après la limite élastique des poutres rectangulaires hybrides à haute performance.