Innovative new flooring systems utilising lightweight fibre reinforced polymer composite materials may have the significant potential to offer both economic and performance benefits for infrastructure asset owners compared to conventional concrete and steel systems. Over recent years, a range of prototype floor systems using fibre reinforced polymer composites have been developed by researchers at the University of Southern Queensland. However before such structural systems can be widely adopted by industries, fundamental understanding of their behaviour must be improved. Such work will allow for the development of new design and analysis procedures which will enable engineers to efficiently and accurately design and analyse such structures. This dissertation presents an investigation into a new two-way fibre reinforced composite floor slab system. The proposed new two-way slab system is, in essence, a sandwich structure with an innovative hollow core made from a castable particulate filled resin system. The key focus of this dissertation is the development of a new analysis tool to analyse the two-way fibre reinforced composite slab and facilitate subsequent parametric studies into slab configurations for concept refinement. The detailed 3D finite element analyses and experimental investigations are performed to verify the new analysis tool, and provide more detailed insight into the structural behaviour of this new two-way fibre reinforced composite slab. Comparisons with detailed 3D FEA and experiments illustrate that the simplified analysis tool is capable of providing sufficient accuracy for the preliminary analysis of a slab structure. Moreover, the 3D finite element analyses agree well with the experiments, and it is concluded that the behavioural responses of the proposed new slab structure can be reliably predicted. The experimental results show that this new slab concept exhibits quite a robust static behaviour and is likely to have a robust fatigue performance.

Ο σκοπός αυτής της διπλωματικής εργασίας είναι η σύγκριση της αποτελεσματικότητας της ενίσχυσης, στοιχείων από φέρουσα τοιχοποιία, με μανδύες συνθέτων υλικών, οι οποίοι αποτελούνταν από στρώσεις ανθρακοϋφάσματος, με οργανική ή ανόργανη μήτρα και με τοποθέτηση ράβδων οπλισμού, από ανθρακονήματα, μέσα στους συνεχείς αρμούς της τοιχοποιίας. Αρχικά δίνονται μορφολογικά και γενικά τεχνικά χαρακτηριστικά. Γίνεται μια σύντομη ιστορική ανασκόπηση για την τοιχοποιία και ακολουθεί ο διαχωρισμός της σε βασικές κατηγορίες. Αναφέρονται οι πρώτες ύλες των τεχνητών λιθοσωμάτων και η διαδικασία παραγωγής τους και στη συνέχεια σημειώνονται τα βασικά είδη τους, με τις συνήθεις διαστάσεις και οι τεχνικές προδιαγραφές τους. Γίνεται ακόμα αναφορά στις κατηγορίες και στις ιδιότητες των κονιαμάτων και των επιχρισμάτων που χρησιμοποιούνται. Ακολουθεί μια περίληψη της μηχανικής της τοιχοποιίας. Περιγράφεται η λειτουργία της άοπλης τοιχοποιίας και ο προσδιορισμός της αντοχής της, υπό θλιπτικά, καμπτικά και διατμητικά φορτία, κατά τον Ευρωκώδικα 6 (EC6) και Τάσιο. Περιγράφονται επίσης τα ελαστικά χαρακτηριστικά της τοιχοποιίας και ο τρόπος, με τον οποίο αυτή συμπεριφέρεται υπό οριζόντια πλευρική φόρτιση, ενώ φέρει θλιπτικά φορτία. Στη συνέχεια γίνεται περιγραφή των ενισχύσεων κατασκευών με σύνθετα υλικά. Κατηγοριοποιούνται τα σύνθετα υλικά και δίνονται οι ιδιότητες των συνθέτων ινο-πλισμένων υλικών. Αναφέρονται εν συντομία οι ιδιότητες των υλικών, ινών και ρητινών, που χρησιμοποιούνται συνήθως για την κατασκευή ινοπλισμένων πολυμερών. Ακόμα αναφέρονται τα βασικά συστήματα ενίσχυσης και οι ιδιότητες των συνθέτων υλικών. Ακολουθεί η μικρομηχανική των υλικών αυτών και οι επιπτώσεις, των περιβαλλοντικών συνθηκών, στην ανθεκτικότητά τους. Επίσης, γίνεται μια περιληπτική αναφορά στις τεχνικές ενισχύσεων δομικών στοιχείων με σύνθετα υλικά. Έπεται μια σύντομη αναφορά στις βάσεις σχεδιασμού ενισχύσεων με σύνθετα υλικά. Δίνονται οι καταστατικοί νόμοι των υλικών για οριακή κατάσταση αντοχής, τόσο για πλήρη συνεργασία όσο και για αποκόλληση του συνθέτου υλικού από την κατασκευή, και για οριακή κατάσταση λειτουργικότητας. Επίσης σχολιάζεται και το θέμα της συνάφειας των συνθέτων υλικών με το υπόστρωμα (τοιχοποιία). Ακολούθως περιγράφονται τα υλικά κατασκευής και ενίσχυσης, τα πειραματικά δοκίμια και δίνονται οι μηχανικές τους ιδιότητες. Ακόμα γίνεται περιγραφή των ειδών των δοκιμίων, που δημιουργήθηκαν, της διαδικασίας ενισχύσεώς τους, σύμφωνα με τους τρόπους που είχαν αποφασιστεί, δηλαδή με κατασκευή μανδυών και με τοποθέτηση ράβδων οπλισμού από σύνθετα υλικά. Επίσης περιγράφονται εν συντομία ο μηχανικός εργαστηριακός εξοπλισμός, που χρησιμοποιήθηκε για την εκτέλεση των πειραματικών διαδικασιών. Στην συνέχεια γίνεται αναλυτική προσομοίωση για κάθε είδος δοκιμίου και ενίσχυσης, από όπου εξάγεται και η θεωρητική τιμή της αντοχής τους, και περιγραφή της πειραματική διαδικασίας, που ακολούθησε για τον έλεγχό τους. Ακολούθως, γίνεται σύγκριση μεταξύ των τρόπων ενίσχυσης και αναφορά των σχετικών πλεονεκτημάτων και τα μειονεκτημάτων τους, ανά κατηγορία δοκιμίων. Τέλος, δίνονται τα συμπεράσματα της εργασίας, που συνοπτικά είναι ότι η χρήση α-νόργανης μήτρας για την κατασκευή μανδυών προσφέρει, με σχετική μείωση της αντοχής, μεγαλύτερη παραμορφωσιμότητα και ικανότητα απορρόφησης ενέργειας και ότι η ενίσχυση, με τοποθέτηση ράβδων ανθρακονήματος, μέσα στους συνεχείς αρμούς της τοιχοποιίας, είναι επισφαλής, λόγω της μη ικανοποιητικής συνάφειάς τους με το συνδετικό κονίαμα, αποτελέσματα, τα οποία μπορούν να χρησιμοποιηθούν για την καλύτερη διαστασιολόγηση των ενισχύσεων με σύνθετα υλικά. Επίσης αναφέρονται κάποια θέματα που χρήζουν περαιτέρω μελέτης, όπως η τοποθέτηση των ράβδων ανθρακονημάτων σε άλλες θέσεις και διευθύνσεις, το απαιτούμενο ποσοστό ινών και η πιθανή τροποποίηση των πειραματικών διατάξεων, ώστε να πραγματοποιηθεί ακριβέστερη προσομοίωση των πραγματικών στοιχείων και φορτίσεων, μιας κατασκευής. / The purpose of this study is the comparison between the use of fibre-reinforced polymers (FRP) as strengthening materials for masonry walls with jackets of polymeric matrix (organic and inorganic) using carbon fabrics and strips (into the constant joints of masonry). First of all, is discribed the history of masorny and its categories. Then, are mentioned the first materials for bricks, the procedure for their produce and their sizes. Also, are mentioned the categories of mortar and plaster. Moreover, is discribed the mechanics of masonry according the Eurocode 6(EC6) and the professor Tasios. Furthermore, are reported the categories of composite materials and their qualities. Also, is annotated the connection between the composite materials and the masonry (substratum). Apart from this, are described the materials that were used to form and reinforce elements of masonry wall. Also, are described the types of elements of masonry wall, that were built, the procedure for their reinforcement and the mechanical equipment of the laboratory, where expirements took place. Moreover, are annotated the analytical model for every type of masonry element, from where theoritical values were taken and the experimental procedure. Furthermore, is presenced the comparison between every type of reinforcment and their advantages or disadvantages. Finally, are decribed subjects for future usage and results of this study.

Today¿s engineers spend an increasing proportion of their time on the maintenance and retrofitting of existing structures. Many of these structures were designed for a purpose totally different from that for which they are now employed. The use of buildings has changed over the last few decades especially during the commercial boom in the 1990s and bridge structures are taking on more and more loads as traffic on the roads continues to rise dramatically.

Reinforcement of concrete flexural components has been traditionally provided by steel rebar; however, durability concerns and life maintenance costs of this product have powered the emergence of fibre reinforced polymers (FRP) as reinforcement in concrete. FRP products hold tremendous promise but their application can be constrained due to design challenges resulting from a reduced modulus of elasticity. The ability to meet serviceability behavior, such as crack width and deflection, is commonly the limiting factor for design. Therefore, the area of FRP reinforcement provided is often greater than the amount required for strength alone and this has significant impacts on the project economics. The bond dependent coefficient (kb) of FRP is required for serviceability design purposes in order to account for the bonding capability of FRP to concrete. The values of this coefficient reported in experimental studies are highly variable, resulting in unreliable crack response predictions. Therefore, a more consistent interpretation and calculation must be found for the bond dependent coefficient due to its critical importance in design. The bond dependent coefficient, as well as physical parameters which influence crack width in GFRP reinforced concrete, were investigated experimentally in this study using a total of 33 specimens. The test procedure was taken from a procedure being developed by the American Concrete Institute (ACI) Committee 440 and was evaluated and modified as required during testing. Phase I testing was used to investigate and determine the physical parameters which had the most significant influence on cracking behaviour and bonding capability. Using significant findings from Phase I, Phase II testing was structured to focus on the interpretation of the bond dependent coefficient and the statistical variation in a set of 5 identical test specimens. Current design equations, as recommended by ACI 440.1R-06 and CHBDC CAN/CSA-S6-06, were used for the calculation of the bond dependent coefficient for all specimens. Interpretation of the bond dependent coefficient was considered using the stress-level approach and newly developed slope approach. Results of the study indicated that the high variability of kb was likely due to its interpretation. Current design equations force a zero intercept, neglecting the fact that concrete does not crack immediately upon loading. In addition, clear definitions of service stress and maximum crack width are ambiguous, further complicating the calculation of the bond dependent coefficient. This resulted in a range of kb values for a given beam despite the fact that kb is inherently a material property of the bar. The behaviour of specimens following load cycling was also very different than the initial loading cycle and consequently, kb was also significantly different. As structures in the field will be subjected to continual loading and unloading, the effect of cyclic loading becomes a consideration in the calculation of kb.

Epoxy intumescent coatings are fire protection systems for steel structural elements that are widely used in applications that protection from severe hydrocarbon fires is required, such as oil and gas facilities. These polymer coatings react upon heating and expand into a thick porous char layer that insulates the protected steel element. In the typical fire scenarios for these applications, the intumescent coatings must resist very high heat fluxes and highly erosive forces from ignited pressurised gases. Hence, continuous fibre reinforcement is embedded in the thick epoxy coating during installation, so as to ensure the integrity of the weak intumesced char during fire exposure. This reinforcement is typically in the form of a bidirectional carbon and/or glass fibre mesh, thus under normal service conditions a fibre-reinforced intumescent coating (FRIC) is essentially a lightly fibre-reinforced polymer (FRP) composite material. This thesis examines the impacts of embedded high strength fibres on the tensile behaviour of epoxy intumescent materials in their unreacted state prior to fire exposure, and the potential enhancements that arise in the structural performance of elements protected with FRICs. An experimental programme is presented comprising tensile coupon tests of unreacted intumescent epoxies, reinforced with different fibre meshes at various fibre volume fractions. It is demonstrated that the tensile properties of FRICs can be enhanced considerably by including increasing amounts of carbon fibre reinforcement aligned in the principal loading direction, which can be tailored in the desired orientation on the coated structural members to enhance their load carrying capacity and/or deformability. An experimental study is presented on coated intact and artificially damaged I-beams (simulating steel losses from corrosion) tested in bending, demonstrating that FRICs can enhance the flexural response of the beams after yielding of steel, until the tensile rupture of the coatings. An analytical procedure for predicting the flexural behaviour of the coated beams is discussed and validated against the obtained test results, whereas a parametric analysis is performed based on this analytical model to assess the effect of various parameters on the strengthening efficiency of FRICs. The results of this analysis demonstrate that it is feasible to increase the flexural load capacity of thin sections considerably utilising the flexural strength gains from FRICs. Finally, a novel application is proposed in this thesis for FRICs as a potential system for structural strengthening or retrofitting reinforced concrete and concrete-encased steel columns by lateral confinement. An experimental study is presented on the axial compressive behaviour of short, plain concrete and concrete-encased structural steel columns that are wrapped in the hoop direction with FRICs. The results clearly show that epoxy intumescent coatings reinforced with a carbon fibre mesh of suitable weight can provide lateral confinement to the concrete core resisting its lateral dilation, thus resulting in considerable enhancements of the axial strength and deformability of concrete. The observed strengthening performance of the composite protective coatings is found to be at least as good as that of FRP wraps consisting of the same fibre reinforcement mesh and a conventional, non-intumescent epoxy resin. The predictive ability of existing design-oriented FRP confinement models is compared against the experimental results, and is found to be reasonably precise in predicting the peak strength of the tested columns, hence existing models appear to be suitable for design and analysis of column strengthening schemes with the proposed novel FRIC system. The research presented herein shows clearly that FRICs have a strong potential as alternative systems for consideration in the field of structural strengthening and rehabilitation, since they can provide substantial enhancements in the load carrying capacity for both applications considered. At the same time FRICs can thermally protect the underlying structural elements in the event of a fire, by intumescing and charring, thus potentially eliminating the need for additional passive fire protection that is common with conventional fire-rated FRP wrapping systems. Although this thesis provides a proof-of-concept for use of the proposed novel FRICs as structural strengthening materials, considerable additional research is particularly required to study their fire protection performance when applied to concrete substrates, to make use of the proposed hybrid functionality with confidence.

yes / This paper reports the testing of three continuously and two simply supported concrete beams reinforced with carbon fibre reinforced polymer (CFRP) bars. The amount of CFRP reinforcement in beams tested was the main parameter investigated. A continuous concrete beam reinforced with steel bars was also tested for comparison purposes. The ACI 440.1R-06 equations are validated against the beam test results. Test results show that increasing the CFRP reinforcement ratio of the bottom layer of simply and continuously supported concrete beams is a key factor in enhancing the load capacity and controlling deflection. Continuous concrete beams reinforced with CFRP bars exhibited a remarkable wide crack over the middle support that significantly influenced their behaviour. The load capacity and deflection of CFRP simply supported concrete beams are reasonably predicted using the ACI 440.1R-06 equations. However, the potential capabilities of these equations for predicting the load capacity and deflection of continuous CFRP reinforced concrete beams have been adversely affected by the de-bonding of top CFRP bars from concrete.

El uso de barras de materiales compuestos (FRP) se propone como una alternativa efectiva para las tradicionales estructuras de hormigón armadas con acero que sufren corrosión en ambientes agresivos. La aceptación de estos materiales en el mundo de la construcción está condicionada a la compresión de su comportamiento estructural. Este trabajo estudia el comportamiento adherente entre barras de FRP y hormigón mediante dos programas experimentales. El primero incluye la caracterización de la adherencia entre barras de FRP y hormigón mediante ensayos de pull-out y el segundo estudia el proceso de fisuración de tirantes de hormigón reforzados con barras de GFRP mediante ensayo a tracción directa. El trabajo se concluye con el desarrollo de un modelo numérico para la simulación del comportamiento de elementos de hormigón reforzado bajo cargas de tracción. La flexibilidad del modelo lo convierte en una herramienta flexible para la realización de un estudio paramétrico sobre las variables que influyen en el proceso de fisuración. / The use of Fibre Reinforced Polymers (FRP) as reinforcement in concrete structures is considered to be a possible alternative to steel in those situations where corrosion is present. The full acceptance of FRP reinforcement in concrete construction is contingent on a complete study and comprehension of all aspects of their structural performance. This thesis investigates the bond behaviour between Fibre Reinforced Polymer (FRP) reinforcement and concrete. Two experimental programs were conducted. In the first program the role of the variables which affect the bond behaviour was studied through pull-out test. In the second program, GFRP RC members were tested in tension to study their cracking response. To conclude the thesis, a numerical model was developed to simulate the cracking behaviour of RC tensile members. Since the model was flexible enough to include any "user-defined" bond-slip law and variable materials' properties, a parametric study was conducted to analyze which are the variables that influence the cracking behaviour.

Research Doctorate - Doctor of Philosophy (PhD) / Inserting fibre reinforced polymer (FRP) strips into pre-cut grooves in the surface of masonry walls is an emerging technique for the retrofit of unreinforced masonry (URM) structures. This method, known as near surface mounting (NSM), provides significant advantages over externally bonded FRP strips in that it has less of an effect on the aesthetics of a structure and can sustain higher loading before debonding. As this technique is relatively new, few studies into the behaviour of masonry walls strengthened using this technique have been conducted. A combined experimental and numerical program was conducted as part of this research project to study the in-plane shear behaviour of masonry wall panels strengthened with NSM carbon FRP (CFRP) strips. In this project the FRP strips were designed to resist sliding along mortar bed joints and diagonal cracking (through mortar joints and brick units). Both of these failure modes are common to masonry shear walls. Different reinforcement orientations were used, including: vertical; horizontal; and a combination of both. The first stage of the project involved characterising the bond between the FRP and the masonry using experimental pull tests (18 in total). From these tests the bond strength, the critical bond length and the local bond-slip relationship of the debonding interface was determined. The second stage of the project involved conducting diagonal tension/shear tests on masonry panels. A total of four URM wall panels and seven strengthened wall panels were tested. These tests were used to determine: the effectiveness of the reinforcement; the failure modes; the reinforcement mechanisms; and the behaviour of the bond between the masonry and the FRP in the case of a panel. The third stage of the project involved developing a finite element model to help understand the experimental results. The masonry was modelled using the micro-modelling approach, and the FRP was attached to the masonry model using the bond-slip relationships determined from the pull tests. Reinforcement schemes in which vertical FRP strips were used improved the strength and ductility of the masonry wall panels. When only horizontal strips were used to reinforce a wall panel, failure occurred along an un-strengthened bed joint and the increase in strength and ductility was negligible. The vertical reinforcement prevented URM sliding failure by restraining the opening (dilation) of the sliding cracks that developed through the mortar bed joints. The finite element model reproduced the key behaviours observed in the experiments for both the unreinforced and FRP strengthened wall panels. This model would potentially be useful for the development of design equations.

Research Doctorate - Doctor of Philosophy (PhD) / Inserting fibre reinforced polymer (FRP) strips into pre-cut grooves in the surface of masonry walls is an emerging technique for the retrofit of unreinforced masonry (URM) structures. This method, known as near surface mounting (NSM), provides significant advantages over externally bonded FRP strips in that it has less of an effect on the aesthetics of a structure and can sustain higher loading before debonding. As this technique is relatively new, few studies into the behaviour of masonry walls strengthened using this technique have been conducted. A combined experimental and numerical program was conducted as part of this research project to study the in-plane shear behaviour of masonry wall panels strengthened with NSM carbon FRP (CFRP) strips. In this project the FRP strips were designed to resist sliding along mortar bed joints and diagonal cracking (through mortar joints and brick units). Both of these failure modes are common to masonry shear walls. Different reinforcement orientations were used, including: vertical; horizontal; and a combination of both. The first stage of the project involved characterising the bond between the FRP and the masonry using experimental pull tests (18 in total). From these tests the bond strength, the critical bond length and the local bond-slip relationship of the debonding interface was determined. The second stage of the project involved conducting diagonal tension/shear tests on masonry panels. A total of four URM wall panels and seven strengthened wall panels were tested. These tests were used to determine: the effectiveness of the reinforcement; the failure modes; the reinforcement mechanisms; and the behaviour of the bond between the masonry and the FRP in the case of a panel. The third stage of the project involved developing a finite element model to help understand the experimental results. The masonry was modelled using the micro-modelling approach, and the FRP was attached to the masonry model using the bond-slip relationships determined from the pull tests. Reinforcement schemes in which vertical FRP strips were used improved the strength and ductility of the masonry wall panels. When only horizontal strips were used to reinforce a wall panel, failure occurred along an un-strengthened bed joint and the increase in strength and ductility was negligible. The vertical reinforcement prevented URM sliding failure by restraining the opening (dilation) of the sliding cracks that developed through the mortar bed joints. The finite element model reproduced the key behaviours observed in the experiments for both the unreinforced and FRP strengthened wall panels. This model would potentially be useful for the development of design equations.

El uso de materiales compuestos de matriz polimérica (FRP) emerge como alternativa al hormigón convencionalmente armado con acero debido a la mayor resistencia a la corrosión de dichos materiales. El presente estudio investiga el comportamiento en servicio de vigas de hormigón armadas con barras de FRP mediante un análisis teórico y experimental. Se presentan los resultados experimentales de veintiséis vigas de hormigón armadas con barras de material compuesto de fibra de vidrio (GFRP) y una armada con acero, todas ellas ensayadas a flexión de cuatro puntos. Los resultados experimentales son analizados y comparados con algunos de los modelos de predicción más significativos de flechas y fisuración, observándose, en general, una predicción adecuada del comportamiento experimental hasta cargas de servicio. El análisis de sección fisurada (CSA) estima la carga última con precisión, aunque se registra un incremento de la flecha experimental para cargas superiores a las de servicio. Esta diferencia se atribuye a la influencia de las deformaciones por esfuerzo cortante y se calcula experimentalmente.Se presentan los aspectos principales que influyen en los estados límites de servicio: tensiones de los materiales, ancho máximo de fisura y flecha máxima permitida. Se presenta una metodología para el diseño de dichos elementos bajo las condiciones de servicio. El procedimiento presentado permite optimizar las dimensiones de la sección respecto a metodologías más generales. / Fibre reinforced polymer (FRP) bars have emerged as an alternative to steel for reinforced concrete (RC) elements in aggressive environments due to their non-corrosive properties. This study investigates the short-term serviceability behaviour of FRP RC beams through theoretical and experimental analysis. Twenty-six RC beams reinforced with glass-FRP (GFRP) and one steel RC beam are tested under four-point loading. The experimental results are discussed and compared to some of the most representative prediction models of deflections and cracking for steel and FRP RC finding that prediction models generally provide adequate values up to the service load. Additionally, cracked section analysis (CSA) is used to analyse the flexural behaviour of the specimens until failure. CSA estimates the ultimate load with accuracy, but it underestimates the experimental deflection beyond the service load level. This increment is mainly attributed in this work to shear induced deflection and it is experimentally calculated.A discussion on the main aspects of the SLS of FRP RC is introduced: the stresses in materials, maximum crack width and the allowable deflection. A methodology for the design of FRP RC at the serviceability requirements is presented, which allows optimizing the overall depth of the element with respect to more generalised methodologies.