Dissertations / Theses on the topic 'Glass fibre reinforced polyester (GFRP)'

Cette thèse porte sur la caractérisation non destructive par ondes ultrasonores des échantillons représentatifs des pales d’éoliennes offshore, avec confrontation aux tests mécaniques. Les échantillons sont en matériaux composites à base de la résine polyester renforcée par des fibres de verre UD GFRP (Unidirectional Glass Fibers Reinforced Polyester). Ils sont soumis à un vieillissement accéléré dans l’eau de mer chauffée à 40 °C et à 60 °C, afin de simuler le milieu marin et réduire la durée d’étude. L’objectif est de trouver des paramètres acoustiques sensibles au vieillissement permettant d’évaluer l’effet du vieillissement ou de le quantifier. L’analyse par ondes guidées de Lamb a montré une diminution des vitesses de phase des modes et de la vitesse de Rayleigh, ainsi que l’augmentation de l’atténuation dans le matériau, ce qui indique que les propriétés mécaniques des matériaux se dégradent à cause du vieillissement. L’imagerie C-scan montre une dégradation de la résine, entraînant la réorganisation des fibres et la modification de leur alignement. Une modélisation numérique par la méthode des éléments finis de la propagation des ondes guidées dans ces matériaux a montré que les propriétés structurelles et géométriques des matériaux se dégradent à cause du vieillissement. Les paramètres les plus attaquées sont les constantes d’élasticité, ainsi que la masse volumique pour des vieillissement plus forts et plus longs. Enfin, le nombre des plis des renforts dans un échantillons joue un rôle important dans sa résistance au vieillissement
This thesis discusses the ultrasonic non-destructive characterization of representative samples of offshore wind turbine blades. The samples are made of composite materials based on Unidirectional Glass Fibers Reinforced Polyester (UD GFRP). Samples are subjected to accelerated aging in heated seawater at 40°C and 60°C, in order to simulate the marine environment and reduce study times. The aim is to find acoustic parameters sensitive to aging, enabling the effect of aging to be assessed or quantified. Lamb's guided wave analysis showed a decrease in mode phase velocities and Rayleigh velocity, as well as an increase in attenuation in the material, indicating that the mechanical properties of the material are degrading due to aging. C-scan imaging shows degradation of the resin, leading to reorganization of the fibers and changes in their alignment. Finite element numerical modelling of guided wave propagation in these materials has shown that the structural and geometric properties of the materials degrade with age. The parameters most affected are the elasticity constants, as well as the density for stronger and longer aging. Finally, the number of reinforcement plies in a sample plays an important role in its resistance to aging

A previous study, looking at the creep-rupture behaviour of mixed reinforcement GRP when immersed in water, had discovered that low loads, behaviour became temperature sensitive. Since the recorded time to failure of a sample was reduced at elevated temperatures, from that predicted by a linear extrapolation of the short term creep-rupture results, this deviation caused problems in the accurate prediction of long-term design stresses. In order to improve the accuracy of long term design predictions, it was decided to study the mechanisms of creep in GRP that initiates time dependent failure. From this, it was hoped that accurate design criteria suitable for predicting GRP response over a 30 year design life from short term creep tests, could be developed. This thesis reports the results obtained from such a study. A series of creep tests were performed on mixed reinforcement GRP samples at several stress levels, both in air, and in room temperature distilled water, using a microcomputer based data collection system. In conjunction with this work, damage development in samples, due to combinations of water uptake and creep loading, was followed, using both scanning electron, and optical, microscopy. Moisture uptake measurements were undertaken under a series of load/temperature regimes, and fibre/matrix debonding followed using photographic techniques. In this way, water absorption, both in terms of uptake rate, and location within a sample, could be characterised. Tensile tests were also performed to determine the standard mechanical properties of the mixed reinforcement GRP used. It was found that a critical damage state was created at loads in excess of 50% of ultimate, but not below. This took the form of between 2 and 8 neighbouring filament breaks in the longitudinal woven rovings at weave crossover points, producing microcracks in the reinforcement. The creation of this multifilament fracture damage during primary creep, was considered to be necessary for time dependent failure to occur in air. Secondary greep strain was found to increase in discrete steps, both in air and water. This was attributed to the formation of transverse grasks in the longitudinal woven rovings, propogating from the above critical damage. In water, diffusion was found to be non-Fickian. Moisture uptake increased with increases in applied load and temperature. Water was seen to accumulate at weave cross-over points when immersed under load. This led to stress-enhanced fibre corrosion in these regions, weakening the reinforcement, and reducing the failure time from that expected at the same load level in air. The localised nature of moisture degradation was thought to result in the formation of critical fibre damage at loads below 50% of ultimate, when immersed in water. Two design criteria based on the observed creep mechanisms, have been developed for GRP that predict response when loaded in either air, or water. Both predict the existence of creep-rupture limits at low loads.

Due to increase in the application of glass fibre reinforced polymer (GFRP) beams based structural systems for rehabilitation of existing and construction of new bridges there is a requirement for identification of critical components of these structural systems and the assessment of damage in this sort structural. The application of vibration-based damage detection (VBDD) techniques has been identified as one of the universal technique that is promising in damage assessment in composite beams. The current study aimed at using vibration-based damage detection technique for assessment of damage exhibited by FRP composite beam structure. This thesis addresses the experimental and numerical study of damage assessment of FRP composite beams using vibration data. Dynamic measurements were carried out considering different specified boundary conditions and the effect of supports on the modal parameters and the effect of damage would be obtained. Another set of experiments were conducted on a Fixed-Free beam with unspecified boundary conditions at the free end, where a mass and a spring attached to the free end and beams were tested for different damage scenarios. Triaxial accelerometers were placed at selected locations based on the result of simple FE beam model. The beams were excited in the two (vertical and horizontal) directions by means of a hammer but only the vertical direction was taken into consideration at this point. The responses at different points along the beam were recorded at different levels of damage and fed into an FIT analyzer. Post-processing of data was done with the stochastic subspace identification (SSI) technique. The effect of the damage on the natural frequencies, mode shapes, and damping ratio were determined. Finite element models for the intact, reference and damaged beams were constructed and used to support the dynamic measurements. FE model updating was applied to different five boundary conditions in order to evaiuate their effect. Damage assessment techniques based on selected methods such as modal frequency change, direct mode shapes, change in modal curvature, damage index method and model updating methods were developed and applied to the beams. A unique test configuration was introduced by combining fixed-free beam with undefmed boundary at the free end. The spring and masses were attached to the free-end, this was implemented for different damage scenarios. The outcome of this implement experiment was discussed and analysed.

Glass Fibre Reinforced Polymer (GFRP) bars have been developed as an alternative to steel reinforcement for various structural concrete applications. Due to their non-corrossive nature, they are particularly suited for harsh environments where steel reinforcement is prone to corrosion. The purpose of this research is to determine the feasibility of GFRP reinforcing bars as concrete bridge deck reinforcement for locations, such as coastal New Zealand, where the non-corrosive benefits of GFRP may offer an alternative to traditional mild steel reinforcement. GFRP use as structural reinforcement may offer life-cycle cost benefits for certain structures as maintenance to repair corroded reinforcement is not necessary. The use of GFRP reinforcement in a New Zealand design context was investigated to directly compare the structural performance of this alternative reinforcing product. Mateen-bar, manufactured by Pultron Composites Ltd, is the GFRP reinforcing bar used in the experimental tests. Experimental investigation of tensile properties of GFRP bar samples was carried out to understand the mechanical behaviour of GFRP reinforcement and validate the manufacturer’s specifications. This series of tests highlighted the complexities of carrying out tensile testing of FRP products, due to the inability to grip the GFRP directly in a testing machine without crushing the specimen. Two phases of full-scale tests were carried out to compare the performance of bridge deck slabs reinforced with typical mild steel and GFRP reinforcing bar. This experimental testing was different to most existing research on GFRP reinforced slab performance as it did not compare the performance of a GFRP reinforcing bar area equivalent to steel, but was designed in such a way as to dependably give the same moment capacity of the steel reinforced slab design. This incorporated the recommended limit of 20% of design stress given by the manufacturer which led to an apparent over-reinforced section for the GFRP slab design. The aim of the experiments was to investigate the comparative performance of a typical New Zealand bridge deck design and a GFRP reinforced equivalent designed in such a way as is currently recommended by the manufacturer. The over-reinforcement lead to differences in conclusions drawn by other authors who have studied GFRP reinforced slab behaviour. Both flexural and concentrated loading (simulating vehicle loading) tests were carried out on both the steel and GFRP reinforced slab designs. Due to over-reinforcement the GFRP slab was considerably stiffer and stronger than the steel design, indicating that serviceability issues are unlikely to be as much of a design issue as existing literature would suggest. Deflection prediction models generally underestimate the strength of over-reinforced sections. All slabs failed in punching shear under concentrated loads, indicating that punching shear may be a critical failure mechanism for GFRP reinforced slabs Based on the findings from the extensive experimental phases, a set of design recommendations were made to further improve the potential for GFRP to be used for bridge deck design in a New Zealand context.

Very limited research studies have been conducted to examine bond of glass fibre reinforced polymer (GFRP) bars with high concrete strength. The current research project aims to compare between bond measured from a pull-out test and a hinged beam test for GFRP bars embedded in high strength concrete. Different parameters influencing bond such as GFRP bar diameter, embedment length and surface configuration were investigated in both test methods, while the bar position, i.e. top or bottom, was only studied in hinged beams. Seventy-two pull-out cubes, eight pull-out prisms and twenty-four hinged beams reinforced with GFRP bars were constructed and tested to failure. Twelve pull-out cubes and four hinged beams reinforced with steel bars were also tested for comparison purposes. The results showed that bond stress – slip curves obtained from various testing methods were similar, consisting of high initial stiffness, followed by nonlinear ascending and softening branches. In addition, it was found that the experimental bond strength obtained from hinged beams was higher than both bond strengths measured by the pull-out cube and pull-out prism. However, when a finite element analysis was conducted for hinged beams, it was shown that the tensile force in the reinforcing bar estimated by equilibrium conditions is overestimated as the large deformation of hinged beams at failure was not considered. Therefore, if the tensile force obtained from the finite element analysis is used to calculate the bond strength, it would be similar to that obtained from pull-out cube and prism. Moreover, it was found that the distribution of tensile and bond stresses was nonlinear along the GFRP embedment length and bond stress at the vicinity of the free end increased with increasing the load due to redistribution of bond stresses along the embedment length. Bond strengths were compared against the prediction methods provided in ACI-440.1R, CSA-S806, CSA-S6 and JSCE 1997. In general, all design codes showed conservative results for all specimens tested and ACI predictions gave a good agreement with experimental data compared to other codes. Artificial neural network models were developed to predict bond strength of GFRP bars in concrete. These models used bar diameter, embedment length, concrete compressive strength and concrete cover as input variables. The developed ANN models showed to be able to predict bond strength of GFRP bars in concrete and, therefore, were used to conduct a parametric study.
Higher Education Institute, Government of Libya

Yes
In this study, bond properties of glass fibre reinforced polymer (GFRP) bars embedded in high-strength concrete (HSC) were experimentally investigated using a pull-out test. The experimental program consisted of testing 84 pull-out specimens prepared according to ACI 440.3R-12 standard. The testing of the specimens was carried out considering bar diameter (9.5, 12.7 and 15.9 mm), embedment length (2.5, 5, 7.5 and 10 times bar diameter) and surface configuration (helical wrapping with slight sand coating (HW-SC) and sand coating (SC)) as the main parameters. Twelve pull-out specimens reinforced with 16 mm steel bar were also tested for comparison purposes. Most of the specimens failed by a pull-out mode. Visual inspection of the tested specimens reinforced with GFRP (HW-SC) bars showed that the pull-out failure was due to the damage of outer bar surface, whilst the detachment of the sand coating was responsible for the bond failure of GFRP (SC) reinforced specimens. The bond stress – slip behaviour of GFRP (HW-SC) bars is different from that of GFRP (SC) bars and it was also found that GFRP (SC) bars gave a better bond performance than GFRP (HW-SC) bars. It was observed that the reduction rate of bond strength of both GFRP types with increasing the bar diameter and the embedment length was reduced in the case of high-strength concrete. Bond strength predictions obtained from ACI-440.1R, CSAeS806, CSA-S6 and JSCE design codes were compared with the experimental results. Overall, all design guidelines were conservative in predicting bond strength of both GFRP bars in HSC and ACI predictions were closer to the tested results than other codes.

2014 - 2015
Although traditional materials (steel, concrete, timber and masonry) still dominate the building industry, new materials are constantly being explored by engineers and scientists. For instance, the use of the so-called FRPs (Fibre-Reinforced Polymers) is gradually spreading worldwide [1-4]. The main idea of FRPs is the combination, on a macroscopic scale, of two different long continuous fibres and a polymeric resin. More specifically, high strength fibres (glass, carbon, aramid or ultra-thin steel wires) provide strength and stiffness while the resin (polyester, vinylester or epoxy) protects the fibres and guarantees the stress transfer between them. As a result, enhanced final properties are obtained with respect to those exhibited by the individual constituents. Among several type of fibers, Glass Fibre Reinforced Polymers (GFRP) are widely used due to their relatively low cost, although glass fibres exhibit much lower elastic modulus and ultimate strength than carbon fibres. In addition, some additional issues emerge with regard to durability in alkaline environments and long-term response under sustained stresses. FRP pultruded beams take advantage of their principal features [5-6]. Since the late 1990s, among the FRPs elements, those frequently used in civil engineering are the pultruded ones. They are obtained by the pultrusion process that make possible to produce such profiles with both closed or open cross sections; the only limitation is that the same cross section is required over the length. Pultruded profiles reinforced with glass fibers (GFRP) present many advantages, including very high stiffness and strength to weight ratios, magnetic transparency, corrosion resistance, and an effective manufacturing process. For these features they can be qualified as non-corrosive, high mechanical strength and lightweight materials. In the last few years, they have been used in several different civil structures, acquiring a relevant role as primary bearing structural elements for applications such as cables, stands, truss members, footbridges, boardwalks, high voltage electricity poles, small buildings and emergency-oriented solutions...[edited by Author]
XIV n.s.

The aim of this investigation is to characterise and refine the physical properties of glass fibre reinforced polyester polymer concrete. This material is currently being employed by AV Mouldings (Pty) Ltd. to manufacture manhole and drain components according to specifications existing for cast iron covers. No specification exists for polymer concrete. In particular it has been found that there is a large market for Type 2A replacement manhole covers and frames due to the current problem in South Africa of the cast iron versions being stolen and sold for scrap metal. It has been found that polymer concrete covers manufactured to replace stolen cast iron covers (in existing cast iron frames) fail occasionally in service. The investigation thus focuses on the characterisation of glass fibre reinforced polymer concrete and analysis of the current standards with a view to establishing a new South African Bureau of Standards (SABS) specification for polymer concrete manhole components. The main testing procedure involved flexural testing of beam specimens. Preliminary tests were carried out to measure strength, toughness, strain rate sensitivity, and the effect of different reinforcing materials. Accelerated degradation tests were then conducted to establish the materials resistance to UV radiation, acids, alkalis, and various solvents. Different resins were evaluated, and experiments were conducted using graded aggregates, in an attempt to reduce the number of voids in the material. Vibratory moulding techniques and postcuring methods were also evaluated. The viability of employing silane coupling agents in polymer concrete was investigated in detail towards the end of the research. Redesign of the Type 2A replacement cover was then undertaken.

In recent years, structural adhesive bonding has gained more interest in industrial and civil engineering. The wide use of combinations of different materials, e.g. steel and Glass-Fibre Reinforced Polymer (GFRP) adhesively bonded joints, is often the only alternative structural technique to welded or bolted joints. The structures of industrial storage tanks involved in situations that require high strength and stability to aggressive fluids make wide use of GFRP. The layout of plants usually needs slender, cylindrical and flat bottom tanks. These tanks need to be anchored at their base to withstand seismic loads. An anchorage system requires to transfer anchor bolts' vertical reactions to the tank wall through a steel hold-down lug joined to the GFRP tank shell. To date, standard codes provide solutions not involving adhesive bonding. In this research work, we propose a novel technique that uses the adhesive bonding combined with the classic overlay method to join the steel hold-down lug to the GFRP tank wall. Preliminary, for applying the new procedure to a selected case study, we provide an introduction to the composite material mechanics, then we describe the experimental campaign we performed on two selected adhesives through tensile, compression and shear bulk testing. Besides, we present the adopted procedure to assemble a double shear lap splice steel-GFRP joints and our modelling strategy regarding the finite element analysis of steel-GFRP joint. After calculated the tensile force to a single anchor bolt for a selected case study, taking into account the hydrodynamic actions induced by the earthquake to the tank, we perform a finite element analysis on a tank wall portion containing an anchorage. The results demonstrate the positive effects of the adhesive applied between the hold-down lug facing the tank shell's surface and the tank wall, in reducing the stresses on the joint's composite part.

L’obiettivo del presente lavoro è verificare l’applicabilità di materiali innovativi, quali compositi (GFRP - Glass Fibre Reinforced Polymer) e colle strutturali, per la realizzazione di facciate continue ad alte prestazioni meccaniche e termiche e a basso impatto ambientale. Tale obiettivo è stato verificato anche tramite l’applicazione del principio della “Semplificazione tecnologica” che rappresenta il filo conduttore alla base dello studio e delle sperimentazioni svolte dal gruppo di ricerca, coordinato dal Prof. P.Munafò, che ha sviluppato il brevetto “Sistema per la realizzazione di facciate di edifici” (n.102015000087569) di cui il Professore è inventore. Con tale filosofia di approccio è possibile realizzare componenti edilizi altamente prestazionali e semplici nella loro concezione essendo costituiti con un numero limitato di pezzi implicando così un minor consumo di energia nella produzione, assemblaggio, manutenzione e smaltimento del prodotto, classificandolo quindi come eco-sostenibile. In questa tesi viene verificata la fattibilità di un sistema costruttivo per la realizzazione di facciate continue per edifici studiando preventivamente, con test sperimentali e analisi sul ciclo di vita dei componenti, le prestazioni meccaniche dei profili in GFRP e degli adesivi strutturali in condizioni di invecchiamento accelerato (durabilità) e non, e l’interazione del componente edilizio con l’ambiente, dalla produzione alla dismissione finale (LCA - Life Cycle Assessment). I metodi principalmente usati in questo studio sono di tipo sperimentale al fine di testare le proprietà meccaniche dei materiali, in condizioni ambientali e dopo invecchiamento (accelerato in camera climatica ad elevata umidità e temperatura (ISO 6270-2) e sotto esposizione ai raggi UV (ASTM D904–99)). In seguito ai singoli test di invecchiamento precedentemente citati, sono stati condotti ulteriori sperimentazioni riguardanti il trattamento di campioni a condizioni di invecchiamento combinato (camera climatica ed esposizione ai raggi UV - Tcc+Tuv - e viceversa - Tuv+Tcc -). Al fine di validare i risultati ottenuti dalle sperimentazioni effettuate sono stati eseguiti test numerici e analitici. Il risultato più significativo è dato proprio dalla validazione dell’idea brevettuale dimostrando la possibilità di industrializzare componenti (facciate continue) che utilizzano tale materiale composito (pultruso - GFRP), mediante l’accoppiamento a materiali come l’acciaio che possono conferire al componente alte prestazioni meccaniche, soprattutto per quanto riguarda il contenimento delle deformazioni sotto carico. Le soluzioni tecniche studiate inoltre evitano il problema della rottura fragile delle giunzioni bullonate che è uno dei problemi che riguardano le giunzioni di questo tipo su profili in pultruso. La deformabilità e la rottura fragile delle giunzioni bullonate dei profili in pultruso ne hanno limitato l’utilizzo nel settore dell’ingegneria edile per la realizzazione di facciate continue specie di grandi dimensioni. A tal fine l’attività di ricerca è stata prevalentemente incentrata a verificare la possibilità di inserire nei montati in pultruso di tali facciate, una lamina d’acciaio incollata per contenere la deformazione e per migliorare la qualità della giunzione bullonata in modo da evitare rotture di tipo fragile raggiunto il carico di collasso. Le risultanze dei test sperimentali condotti dimostrano le buone performance del sistema ibrido GFRP-acciaio anche in seguito all’esposizione a differenti condizioni di invecchiamento artificiale e verificano la fattibilità di realizzazione di una facciata continua ad alte prestazioni meccaniche e termiche.
The aim of this work is to demonstrate the applicability of innovative materials, such as Glass Fibre Reinforced Polymer (GFRP) industrialized components (profiles), structural adhesives, for the realization of curtain walls with high mechanical and thermal performances and low environmental impact. This objective with the “Technological Simplification” principle is verified. This latter is the guiding principle to the base of the search and experimental tests carried out by the research group. The teamwork coordinator and patent inventor is Prof P.Munafò, with him I developed a “System for the realization of building façade” (n. 102015000087569). The “Technological Simplification” principle allows the building components realization with high performance and easy to assemble, by using a limited number of pieces. All this involves lower energy consumption in the production, assembly, maintenance and disposal phases. For this reason, the construction element can be considered environmentally sustainable. In this thesis, the feasibility of the constructive system for the realization of building façade, through the experimental tests and component life cycle analysis, is verified. The components and materials properties both in laboratory conditions and after different types of ageing conditions (durability) are tested. The interaction between building components and environment, from the production to ultimate disposal (LCA - Life Cycle Assessment) are analysed. The methods used were mostly of the experimental type. The material mechanical properties both in environmental conditions and in different types of ageing conditions were analysed, such as continuous condensation (ISO 6270-2) and UV irradiation (ASTM D904–99). Additional test with combined artificial ageing (climatic chamber and exposure to UV radiation - Tcc+Tuv – and the other way around - Tuv+Tcc) were tested. The numerical and analytical studies were carried out, with the objective to check and validate the results obtained through experimental tests. The main outcome was the validation of the patents basic ideas, which is a key point in the industrialization process of the construction elements (Structural Member). The aim of this work is to demonstrate the feasibility of the use of pultruded Glass Fiber Reinforced Polymers (GFRP) profiles, adhesively joined with other materials (i.e. steel), in the construction sector. The objective is both to reduce the GFRP profiles deformation under loading conditions, and to avoid the brittle fractures that could occur in bolted joints. In the building engineering field, in fact, these issues (deformations and brittle fractures) prevent the use of pultruded materials. In the research activity, the possibility to adhesively join a steel laminate on the pultruded profile mullion for curtain walls was verified. The containment of the deformations and the prevention of brittle fractures in the bolted joint were checked, in order to verify the pultruded curtain wall feasibility, both constructively and for its structural and energy performances. Experimental results, in fact, demonstrated that the use of GFRP profiles, bonded with structural adhesives and combined with steel, is successful on curtain walls, even when they are exposed to adverse environmental conditions. The feasibility of the curtain wall implementation with high performance is verified.

A study of the existing data shows that two areas of GFRP bar research among others are in need of investigation, the first being behaviour of GFRP bars at cold temperatures and the second being the behaviour of large diameter GFRP rods. Based on the results of experimental work performed, cold temperatures were found to have minimal effect on the mechanical properties of the GFRP bars tested. In addition, through beam testing, large 32mm diameter GFRP bars were found to not fail prematurely due to interlaminar shear failure. By evaluating the mechanical and durability properties of GFRP bars and behaviour of GFRP RC, it can be concluded that GFRP appears to be an adequate alternative reinforcement for concrete structures. Because of high strength, low stiffness and elastic behaviour of GFRP bars, issues of significant importance for reinforced concrete are bond development, influence of shear on member behaviour and member deformability.

Glass Fibre Reinforced Polymer (GFRP) internal reinforcing bars are being increasingly considered as a potential corrosion free alternative to regular and stainless steel reinforcing bars. In spite of the availability of code provisions governing both design and certification of the GFRP bars, their use within concrete structures is currently limited to very specific applications unless some behaviour aspects are further investigated. In particular, crack control, ultimate member deformability and the behaviour of the bent GFRP bars are areas in need of such further investigation. An experimental program was conducted consisting of 24 large-scale beams reinforced with various types of GFRP and steel bars complying with CSA certification standards. The results of which show that the stress in the bent bar stirrups at beam failure exceeded minimum code-prescribed values for design (CSA S6, CSA S806, ACI440). An alternative bend-less system of shear reinforcement using straight double headed bars was successful as shear reinforcement but did however result in significant reductions to member deformability. A critical review of the various design provisions incorporating GFRP shear reinforcement, it was found that many of the design codes use conservative shear reinforcement strengths coupled with unconservative values of either the angle of inclination of the compression strut or the concrete contribution to shear resistance. A new relationship for the inclination of the compression strut was proposed for use within the Simplified Modified Compression Field Theory which when combined with the bend/anchor strength of the shear reinforcement correlate well with the experimental results. Also, it was determined that the design strain limits for GFRP shear reinforcement should not be increased until more detailed studies on the long-term performance of the stirrups are conducted. Finally, advanced analysis techniques like layered sectional- and finite element-analysis both gave excellent analytical estimates of the experimental beam response.

A study of existing research shows a need for an investigation of the bond properties of anchorage systems for GFRP bars including; straight, anchor heads and bends. The standard pullout test was modified to improve testing efficiency, accommodate bend tests, as well as reduce variability of concrete properties across specimens. Based on the results of the experimental work it was concluded that the surface profile of GFRP bars influences the post-peak phase of the bond stress-slip curve. It was also found that GFRP bars with anchor heads would still require a considerable embedment length to develop the bars’ full strength. Bend strengths of three GFRP manufacturers were determined to be between 58 and 80% of the strength of the straight portion of the same bar, while the development length of a two legged stirrup was found to be between five and ten times the bar diameter for all bar types.

There are approximately 6000 Gulfport-type wood structures used to support 1600 km of 230 kV electrical transmission lines in Ontario. An unexpected structural failure caused by wood deterioration has been recognized as a major risk to the safety of these transmission lines. Since the reliability of the electricity transmission and distribution lines is extremely important to the electrical industry and other users of electricity, failure of these structures can result in devastating incidents. Due to the remote location of the transmission network and the requirement to keep the power lines in continuous service, replacement of the Gulfport structures has proved to be very difficult and expensive. This research program investigated the use of Glass Fibre Reinforced Polymer (GFRP) wrap as a light weight and durable strengthening system that can be applied to the existing structures without any interruptions in the functionality of the transmission lines. A total of three control specimens and three strengthened samples were tested in Phase I of the experimental program, which was designed as a feasibility study. It was concluded that the average strength of strengthened samples was 42% higher than the average strength of the control samples, and was greater than the end of life (EOL) threshold of 30 MPa for the cross arms. Therefore, the proposed strengthening system was concluded to be an effective solution for strengthening the deteriorated cross arms of the Gulfport structures. Taguchi methods and Analysis of Variation (ANOVA) were employed in Phase II to optimize the proposed strengthening system. The optimal configuration was determined to be the application of the filler material, non-sanded surface, and the shorter width of wrap (width of 0.6 m). The mean strength of the optimal configuration was estimated to be 52 MPa with a 95% confidence interval of: 38.7 MPa < True Mean < 65.3 MPa. Phase III confirmed the estimated mean and the confidence interval for the optimal configuration in Phase II. The strengthening system changed the failure mode from combined shear-flexure failure to pure flexure and resulted in more consistent strength and stiffness values. The strain values of the GFRP wrap showed that a single layer of wrap was sufficient for the confinement purposes.

This study addresses the flexural performance of sandwich panels composed of a polyurethane foam core and glass fibre-reinforced polymer (GFRP) skins. Panels with and without GFRP ribs connecting the skins have been studied. While the motivation of the study was to develop new insulated cladding panels for buildings, most of the work and findings are also applicable to other potential applications such as flooring, roofing and light-weight decking. The study comprises experimental, numerical, and analytical investigations. The experimental program included three phases. Phase I is a comprehensive material testing program of the polyurethane core and GFRP skins and ribs. In Phase II, six medium size (2500x660x78 mm) panels with different rib configurations were tested in one-way bending. It was shown that flexural strength and stiffness have increased by 50 to 150%, depending on the rib configuration, compared to a panel without ribs. In Phase III, two large-scale (9150x2440x78 mm) panels, representing a cladding system envisioned to be used in the field, were tested under a realistic air pressure and discrete loads, respectively. The deflection under service wind load did not exceed span/360, while the ultimate pressure was about 2.6 times the maximum factored wind pressure in Canada. A numerical study using finite element analysis (FEA) was carried out. The FEA model accounted for the significant material nonlinearities, especially for the polyurethane soft core, and the geometric nonlinearity, which is mainly a reduction in thickness due to core softness. Another independent analytical model was developed based on equilibrium and strain compatibility, accounting for the core excessive shear deformation. The model also captures the localized deformations of the loaded skin, using the principals of beam-on-elastic foundation. Both models were successfully validated using experimental results. Possible failure modes, namely core shear failure, and compression skin crushing or wrinkling were successfully predicted. A parametric study was carried out to explore further the core density, skin thickness, and rib spacing effects. As the core density increased, flexural strength and stiffness increased and shear deformations reduced. Also, increasing skin thickness became more effective as the core density increased. The optimal density was 95-130 kg/m3. Reducing the spacing of ribs enhanced the strength up to a certain level; It then stabilized at a spacing of 2.9 times the panel thickness.
Thesis (Ph.D, Civil Engineering) -- Queen's University, 2010-09-21 16:29:00.315

The introduction of fibre-reinforced polymers (FRPs) to the field of civil engineering has led to numerous research efforts focusing on a wide range of applications where properties such as high strength, light weight or corrosion resistance are desirable. In particular, FRP materials have been especially attractive for use as internal reinforcement in reinforced concrete (RC) structures exposed to aggressive environments due to the rapidly deteriorating infrastructure resulting from corrosion of conventional steel reinforcement. While FRPs have been successfully implemented in a variety of structural applications, little research has been conducted on the use of FRP reinforcement for short span slab bridges. Furthermore, the behaviour of FRP-RC flexural members cast with self-consolidating concrete (SCC) is largely absent from the literature. The present study investigates the behaviour of an all-FRP reinforcement system for slab bridges which combines lower cost glass FRP (GFRP) reinforcing bars with high performance carbon FRP (CFRP) prestressed tendons in SCC to produce a structure which is both cost-efficient and characterized by excellent structural performance at the serviceability, ultimate and fatigue limit states. An extensive experimental program comprised of 57 large or full-scale slab strips was conducted to investigate the effects of reinforcement type, reinforcement ratio, prestressing level and shear reinforcement type on the flexural performance of slab bridges under both monotonic and fatigue loading. The proposed reinforcement system was found to display excellent serviceability characteristics and high load capacities as well as significant deformability to allow for sufficient warning prior to failure. Lastly, the use of post-tensioned CFRP tendons limited the stresses in the GFRP reinforcing bars leading to significantly longer fatigue lives and higher fatigue strengths compared to non-prestressed slabs. Analytical models were used to predict the behaviour of the slab bridge strips at service and at ultimate. Where these models failed to accurately represent the experimental findings, simple modifications were proposed. The results from ancillary tests were also used to modify existing analytical models to predict the effects of fatigue loading on the deflection, crack width, shear resistance and flexural capacity of each of the tested slabs.

Masonry structures constitute a significant portion of building stock worldwide. Seismic performance of unreinforced masonry has been far from satisfactory. Masonry is purported to be a major source of hazard during earthquakes by reconnaissance surveys conducted aftermath of an earthquake. Reasons for the poor performance of masonry structures are more than one namely lack of deformational capacity, poor tensile strength & lack of earthquake resistance features coupled with poor quality control and large variation in strength of materials employed. Fibre Reinforced Plastic (FRP) composites have emerged as an efficient strengthening technique for reinforced concrete structures over the past two decades. Present thesis is focused towards analysing the behaviour of Fibre Reinforced Plastic (FRP) strengthened masonry under axial compression and in-plane shear loading. Determination of in-planes hear resistance of large masonry panels requires tremendous effort in terms of cost, labour and time. Masonry assemblages like prisms and triplets that represent the state of stress present in masonry walls and masonry in-fills when under the action of in-planes hear forces present an alternative option for research and analysis purposes. Hence, present research is focused towards analysing the performance of FRP strengthened masonry assemblages and unreinforced masonry assemblages. Chapter1 provides a brief review on the behaviour of masonry shear walls and masonry in-fills under the action of in-plane shear forces in addition to the performance of masonry structures during past earthquakes. Review of available literature on FRP confinement of masonry prisms with bed joints inclined from 00 to 900 to the loading axis under axial compression, analytical models available for FRP confined concrete, shear strength of masonry triplets attached with FRP is presented. Chapter 2 primarily focuses on determining the various properties of the materials involved in this research investigation. Test procedure and results of the tests conducted to determine the mechanical and related properties of the materials involved are presented. Elastic properties and stress-strain response of burnt clay brick, mortar and FRP laminates are presented. Studies conducted on behaviour of GFRP confined masonry prisms under monotonic axial compression are included in Chapter 3. The study comprised of testing masonry prisms, both unconfined and FRP confined masonry prisms under axial compression. Stretcher bond and English bond prisms, with bed joints normal and parallel to loading axis are included in this study. Two grades of GFRP,360g/m2 and 600 g/m2 are employed to confine masonry prisms. The experimental program involved masonry prism types that accounted for variations in masonry bonding pattern, bed joint inclination to the loading axis and grade of GFRP. Review of the available analytical models predicting compressive strength of FRP confined masonry prism is presented. Available models for FRP confinement of masonry are re-calibrated using the present experimental data generating new coefficients for the already existing model to develop new expression for predicting the compressive strength of FRP confined prisms. In addition to the prism types mentioned earlier, behaviour of unconfined and GFRP confined stretcher bond prisms with bed joints inclined at 300, 450 & 600 to the loading axis are further investigated. Chapter 4 primarily deals with the shear strength and deformational capacity of masonry triplets that represent joint shear failure in masonry. An experimental program involving masonry triplets attached with different types of FRP(GFRP and CFRP), grade of FRP, percentage area covered by FRP and reinforcement pattern is executed. This exercise determined the influence of these parameters over the enhancement achieved in terms of shear strength and ultimate displacement. Results of tests conducted on stretcher bond prisms presented in chapter 3 and results of tests on shear triplets presented in this chapter are combined to study the interaction between shear and normal stresses acting along the masonry bed joint at different angles of inclination. The thesis culminated with chapter 5 as concluding remarks highlighting the salient Information pertaining to the behaviour of FRP strengthened masonry under axial compression and in-plane shear loading obtained as an outcome of the research conducted as a part of this thesis.

Masonry structures constitute a significant portion of building stock worldwide. Seismic performance of unreinforced masonry has been far from satisfactory. Masonry is purported to be a major source of hazard during earthquakes by reconnaissance surveys conducted aftermath of an earthquake. Reasons for the poor performance of masonry structures are more than one namely lack of deformational capacity, poor tensile strength & lack of earthquake resistance features coupled with poor quality control and large variation in strength of materials employed. Fibre Reinforced Plastic (FRP) composites have emerged as an efficient strengthening technique for reinforced concrete structures over the past two decades. Present thesis is focused towards analysing the behaviour of Fibre Reinforced Plastic (FRP) strengthened masonry under axial compression and in-plane shear loading. Determination of in-planes hear resistance of large masonry panels requires tremendous effort in terms of cost, labour and time. Masonry assemblages like prisms and triplets that represent the state of stress present in masonry walls and masonry in-fills when under the action of in-planes hear forces present an alternative option for research and analysis purposes. Hence, present research is focused towards analysing the performance of FRP strengthened masonry assemblages and unreinforced masonry assemblages. Chapter1 provides a brief review on the behaviour of masonry shear walls and masonry in-fills under the action of in-plane shear forces in addition to the performance of masonry structures during past earthquakes. Review of available literature on FRP confinement of masonry prisms with bed joints inclined from 00 to 900 to the loading axis under axial compression, analytical models available for FRP confined concrete, shear strength of masonry triplets attached with FRP is presented. Chapter 2 primarily focuses on determining the various properties of the materials involved in this research investigation. Test procedure and results of the tests conducted to determine the mechanical and related properties of the materials involved are presented. Elastic properties and stress-strain response of burnt clay brick, mortar and FRP laminates are presented. Studies conducted on behaviour of GFRP confined masonry prisms under monotonic axial compression are included in Chapter 3. The study comprised of testing masonry prisms, both unconfined and FRP confined masonry prisms under axial compression. Stretcher bond and English bond prisms, with bed joints normal and parallel to loading axis are included in this study. Two grades of GFRP,360g/m2 and 600 g/m2 are employed to confine masonry prisms. The experimental program involved masonry prism types that accounted for variations in masonry bonding pattern, bed joint inclination to the loading axis and grade of GFRP. Review of the available analytical models predicting compressive strength of FRP confined masonry prism is presented. Available models for FRP confinement of masonry are re-calibrated using the present experimental data generating new coefficients for the already existing model to develop new expression for predicting the compressive strength of FRP confined prisms. In addition to the prism types mentioned earlier, behaviour of unconfined and GFRP confined stretcher bond prisms with bed joints inclined at 300, 450 & 600 to the loading axis are further investigated. Chapter 4 primarily deals with the shear strength and deformational capacity of masonry triplets that represent joint shear failure in masonry. An experimental program involving masonry triplets attached with different types of FRP(GFRP and CFRP), grade of FRP, percentage area covered by FRP and reinforcement pattern is executed. This exercise determined the influence of these parameters over the enhancement achieved in terms of shear strength and ultimate displacement. Results of tests conducted on stretcher bond prisms presented in chapter 3 and results of tests on shear triplets presented in this chapter are combined to study the interaction between shear and normal stresses acting along the masonry bed joint at different angles of inclination. The thesis culminated with chapter 5 as concluding remarks highlighting the salient Information pertaining to the behaviour of FRP strengthened masonry under axial compression and in-plane shear loading obtained as an outcome of the research conducted as a part of this thesis.