Dissertations / Theses on the topic 'Hybrid fibre concrete'

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This paper presents test results of six full scale reinforced concrete continuous T beams. One beam was reinforced with glass fibre reinforced polymer (GFRP) bars while the other five beams were reinforced with a different combination of GFRP and steel bars. The ratio of GFRP to steel reinforcement at both mid-span and middle-support sections was the main parameter investigated. The results showed that adding steel reinforcement to GFRP reinforced concrete T-beams improves the flexural stiffness, ductility and serviceability in terms of crack width and deflection control. However, the moment redistribution at failure was limited because of the early yielding of steel reinforcement at a beam section that does not reach its moment capacity and could still carry more loads due to the presence of FRP reinforcement. The experimental results were compared with the ultimate moment prediction of ACI 440.2R-17, and with the existing theoretical equations for deflection prediction. It was found that the ACI 440.2R-17 reasonably estimated the moment capacity of both mid-span and middle support sections. Conversely, the available theoretical deflection models underestimated the deflection of hybrid reinforced concrete T-beams at all load stages.
The full-text of this article will be released for public view after the publisher embargo on 10 Aug 2021.

Nowadays, thin-walled load bearing structures can be realised using textile reinforced concrete (BRAMESHUBER and RILEM TC 201-TRC [1]). The required tensile strength is achieved by embedding several layers of textile. By means of the laminating technique the number of textile layers that can be included into the concrete could be increased. To further increase the first crack stress and the ductility as well as to optimize the crack development, fine grained concrete mixes with short fibres can be used. By a schematic stress-strain curve the demands on short fibres are defined. Within the scope of this study, short fibres made of glass, carbon, aramid and polyvinyl alcohol are investigated in terms of their ability to fit these requirements. On the basis of these results, the development of hybrid fibre mixes to achieve the best mechanical properties is described. Additionally, a conventional FRC with one fibre type is introduced. Finally, the fresh and hardened concrete properties as well as the influence of short fibres on the load bearing behaviour of textile reinforced concrete are discussed.

ABSTRACT DETERMINATION OF MECHANICAL PROPERTIES OF HYBRID FIBER REINFORCED CONCRETE Yurtseven, Alp Eren M.Sc. Department of Civil Engineering Supervisor: Prof. Dr. Mustafa Tokyay Co-Supervisor: Asst. Prof. Dr. . Ö
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r Yaman August 2004, 82 pages Fiber reinforcement is commonly used to provide toughness and ductility to brittle cementitious matrices. Reinforcement of concrete with a single type of fiber may improve the desired properties to a limited level. A composite is termed as hybrid, if two or more types of fibers are rationally combined to produce a composite that derives benefits from each of the individual fibers and exhibits a synergetic response. This study aims to characterize and quantify the mechanical properties of hybrid fiber reinforced concrete. For this purpose nine mixes, one plain control mix and eight fiber reinforced mixes were prepared. Six of the mixes were reinforced in a hybrid form. Four different types of fibers were used in combination, two of which were macro steel fibers, and the other two were micro fibers. Volume percentage of fiber inclusion was kept constant at 1.5%. In hybrid reinforced mixes volume percentage of macro fibers was 1.0% whereas the remaining fiber inclusion was v composed of micro fibers. Slump test was carried out for each mix in the fresh state. 28-day compressive strength, flexural tensile strength, flexural toughness, and impact resistance tests were performed in the hardened state. Various numerical analyses were carried out to quantify the determined mechanical properties and to describe the effects of fiber inclusion on these mechanical properties. Keywords: Fiber Reinforcement, Hybrid Composite, Toughness, Impact Resistance

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itt Performance - Instituto Tecnológico em Desempenho da Construção Civil
O desenvolvimento de novos concretos vem sendo ampliado ao longo dos anos, o que ocorre paralelamente ao aprimoramento dos cálculos estruturais e ao maior conhecimento sobre as propriedades dos materiais, o que conduz os projetistas ao desenvolvimento de estruturas que necessitam ter características específicas. Com isso surge a necessidade de se desenvolver concretos especiais, que apresentam elevada resistência mecânica e durabilidade. O concreto de pós reativos, também chamado de CPR, é um exemplo destes materiais. Trata-se de um concreto de ultra alto desempenho, com elevada resistência mecânica, extremamente dúctil e de baixa porosidade. Este tipo de concreto apresenta propriedades mecânicas superiores em comparação aos concretos de alta resistência, chegando a resistências à compressão de 200 MPa, à tração de 45MPa e módulo de elasticidade superior a 50 GPa. O consumo de cimento neste tipo de concreto pode atingir 800 kg/m3, além de incorporar elevado volume de sílica ativa. A otimização granular dos constituintes, realizada através de métodos de empacotamento de partículas, faz com que seja possível obter um material com o mínimo de vazios e elevada densidade. As fibras introduzidas no composto proporcionam elevada ductilidade. Neste trabalho, parte do cimento Portland foi substituído por cinza volante, para desenvolver um CPR com baixo consumo de aglomerantes. Também foi estudada a incorporação de dois tipos de fibras, ou hibridização, para uma matriz de CPR com menor consumo de cimento. A introdução de dois tipos distintos de fibras proporciona ao material maior sinergia, diminuindo a formação e a propagação de fissuras durante o carregamento. Os resultados obtidos nesta pesquisa mostram que a substituição parcial do cimento por cinza volante apresentou melhor desempenho mecânico, atingindo resistência à compressão de aproximadamente 190 MPa com 30% de adição. A incorporação de dois tipos distintos de fibras, aço e polipropileno em teores de 80% e 20% respectivamente, proporcionou ao material elevada resistência à tração na flexão e tenacidade. Portanto, é possível dosar CPR com menores consumos de cimento e uso de dois tipos de fibras, melhorando as propriedades da mistura e obtendo um compósito com reduzido impacto ambiental.
The development of new concretes is being expanded over the years, withal the improvements in structural design, along the increased knowledge of materials properties, which leads the designers to develop structures with specific requirements. It arises the need of the development of special concretes, with have enhanced mechanical strength and durability. Reactive powder concrete, also called RPC, is an example of these materials. This is an ultra-high-performance concrete with high mechanical strength, extremely ductile and low porosity. This type of concrete has superior mechanical properties compared to high strength concrete, reaching compressive strengths of 200 MPa, tensile strengths of 45 MPa and modulus higher than 50 GPa. The cement consumption in this type of concrete may reach 800 kg/m3, while incorporating high volumes of silica fume. The optimization of granular constituents accomplished by particle packing methods provides a material with a minimum of voids and also high density. The fiber introduced into the material compound provides high ductility. On this report, fly ash was used to replace some part of the cement, aiming the development of a RPC with low agglomerate consumption. It was also studied the use of two types of fiber, or hybridization, to a RPC matrix array of CPR with less consumption of cement. The introduction of two distinct types of fibers gives the material improved synergy, decreasing the formation and propagation of cracks during the charging. The results obtained in this study show that the partial replacement of cement by fly ash gives better mechanical performance, reaching the compressive strength of approximately 190 MPa with 30% addition. The incorporation of two different types of fibers, steel and polypropylene at levels of 80% and 20% respectively, provided the materials high tensile strength and toughness. Therefore, it is possible to compose an RPC with lower cement consumption and use of two types of fibers, improving the properties of the mixture and obtaining a composite with reduced environmental impact.

As part of a multi-university research program funded by NSF, a comprehensive experimental and analytical study of seismic behavior of hybrid fiber reinforced polymer (FRP)-concrete column is presented in this dissertation. Experimental investigation includes cyclic tests of six large-scale concrete-filled FRP tube (CFFT) and RC columns followed by monotonic flexural tests, a nondestructive evaluation of damage using ultrasonic pulse velocity in between the two test sets and tension tests of sixty-five FRP coupons. Two analytical models using ANSYS and OpenSees were developed and favorably verified against both cyclic and monotonic flexural tests. The results of the two methods were compared. A parametric study was also carried out to investigate the effect of three main parameters on primary seismic response measures. The responses of typical CFFT columns to three representative earthquake records were also investigated. The study shows that only specimens with carbon FRP cracked, whereas specimens with glass or hybrid FRP did not show any visible cracks throughout cyclic tests. Further monotonic flexural tests showed that carbon specimens both experienced flexural cracks in tension and crumpling in compression. Glass or hybrid specimens, on the other hand, all showed local buckling of FRP tubes. Compared with conventional RC columns, CFFT column possesses higher flexural strength and energy dissipation with an extended plastic hinge region. Among all CFFT columns, the hybrid lay-up demonstrated the highest flexural strength and initial stiffness, mainly because of its high reinforcement index and FRP/concrete stiffness ratio, respectively. Moreover, at the same drift ratio, the hybrid lay-up was also considered as the best in term of energy dissipation. Specimens with glassfiber tubes, on the other hand, exhibited the highest ductility due to better flexibility of glass FRP composites. Furthermore, ductility of CFFTs showed a strong correlation with the rupture strain of FRP. Parametric study further showed that different FRP architecture and rebar types may lead to different failure modes for CFFT columns. Transient analysis of strong ground motions showed that the column with off-axis nonlinear filament-wound glass FRP tube exhibited a superior seismic performance to all other CFFTs. Moreover, higher FRP reinforcement ratios may lead to a brittle system failure, while a well-engineered FRP reinforcement configuration may significantly enhance the seismic performance of CFFT columns.

Modern reinforced concrete bridges are designed to avoid collapse and to prevent loss of life during earthquakes. To meet these objectives, bridge columns are typically detailed to form ductile plastic hinges when large displacements occur. California seismic design criteria acknowledges that damage such as concrete cover spalling and reinforcing bar yielding may occur in columns during a design-level earthquake.

The seismic resilience of bridge columns can be improved through the use of a damage resistant hybrid fiber reinforced concrete (HyFRC). Fibers delay crack propagation and prevent spalling under extreme loading conditions, and the material resists many typical concrete deterioration mechanisms through multi-scale crack control.

Little is known about the response of the material when combined with conventional reinforcing bars. Therefore, experimental testing was conducted to evaluate such behaviors. One area of focus was the compression response of HyFRC when confined by steel spirals. A second focus was the tensile response of rebar embedded in HyFRC. Bridge columns built with HyFRC would be expected to experience both of these loading conditions during earthquakes.

The third focus of this dissertation was the design, modeling, and testing of an innovative damage resistant HyFRC bridge column. The column was designed to rock about its foundation during earthquakes and to return to its original position thereafter. In addition to HyFRC, it was designed with unbonded post-tensioning, unbonded rebar, and headed rebar which terminated at the rocking plane. Because of these novel details, the column was not expected to incur damage or residual displacements under earthquake demands exceeding the design level for ordinary California bridges. A sequence of scaled, three dimensional ground motion records was applied to the damage resistant column on a shaking table. An equal scale reinforced concrete reference column with conventional design details was subjected to the same motions for direct comparison.

Compression tests showed that the ductility of HyFRC is superior to concrete in the post-peak softening branch of the response. HyFRC achieved a stable softening response and had significant residual load capacity even without spiral confinement. Concrete required the highest tested levels of confinement to achieved comparable post-peak ductility. Tension tests showed that HyFRC provides a substantial strength enhancement to rebar well beyond their yield point. Interesting crack localization behavior was observed in HyFRC specimens and appeared to be dependent on the volumetric ratio of rebar.

The damage resistant HyFRC bridge column attained its design objectives during experimental testing. It exhibited pronounced reentering behavior with only light damage under earthquake demands 1.5 to 2.0 times the design level. It accumulated only 0.4% residual drift ratio after seven successive ground motions which caused a peak drift ratio of 8.0%. The conventional reinforced concrete column experienced flexural plastic hinging with extensive spalling during the same seven motions. It accumulated 6.8% residual drift ratio after enduring a peak drift ratio of 10.8%.

As an alternative to transverse spiral or hoop steel reinforcement, fiber reinforced polymers (FRPs) were introduced to the construction industry in the 1980's. The concept of concrete-filled FRP tube (CFFT) has raised great interest amongst researchers in the last decade. FRP tube can act as a pour form, protective jacket, and shear and flexural reinforcement for concrete. However, seismic performance of CFFT bridge substructure has not yet been fully investigated. Experimental work in this study included four two-column bent tests, several component tests and coupon tests. Four 1/6-scale bridge pier frames, consisting of a control reinforced concrete frame (RCF), glass FRP-concrete frame (GFF), carbon FRP-concrete frame (CFF), and hybrid glass/carbon FRP-concrete frame (HFF) were tested under reverse cyclic lateral loading with constant axial loads. Specimen GFF did not show any sign of cracking at a drift ratio as high as 15% with considerable loading capacity, whereas Specimen CFF showed that lowest ductility with similar load capacity as in Specimen GFF. FRP-concrete columns and pier cap beams were then cut from the pier frame specimens, and were tested again in three point flexure under monotonic loading with no axial load. The tests indicated that bonding between FRP and concrete and yielding of steel both affect the flexural strength and ductility of the components. The coupon tests were carried out to establish the tensile strength and elastic modulus of each FRP tube and the FRP mold for the pier cap beam in the two principle directions of loading. A nonlinear analytical model was developed to predict the load-deflection responses of the pier frames. The model was validated against test results. Subsequently, a parametric study was conducted with variables such as frame height to span ratio, steel reinforcement ratio, FRP tube thickness, axial force, and compressive strength of concrete. A typical bridge was also simulated under three different ground acceleration records and damping ratios. Based on the analytical damage index, the RCF bridge was most severely damaged, whereas the GFF bridge only suffered minor repairable damages. Damping ratio was shown to have a pronounced effect on FRP-concrete bridges, just the same as in conventional bridges. This research was part of a multi-university project, which is founded by the National Science Foundation (NSF) Network for Earthquake Engineering Simulation Research (NEESR) program.

The application of advanced materials in infrastructure has grown rapidly in recent years mainly because of their potential to ease the construction, extend the service life, and improve the performance of structures. Ultra-high performance concrete (UHPC) is one such material considered as a novel alternative to conventional concrete. The material microstructure in UHPC is optimized to significantly improve its material properties including compressive and tensile strength, modulus of elasticity, durability, and damage tolerance. Fiber-reinforced polymer (FRP) composite is another novel construction material with excellent properties such as high strength-to-weight and stiffness-to-weight ratios and good corrosion resistance. Considering the exceptional properties of UHPC and FRP, many advantages can result from the combined application of these two advanced materials, which is the subject of this research. The confinement behavior of UHPC was studied for the first time in this research. The stress-strain behavior of a series of UHPC-filled fiber-reinforced polymer (FRP) tubes with different fiber types and thicknesses were tested under uniaxial compression. The FRP confinement was shown to significantly enhance both the ultimate strength and strain of UHPC. It was also shown that existing confinement models are incapable of predicting the behavior of FRP-confined UHPC. Therefore, new stress-strain models for FRP-confined UHPC were developed through an analytical study. In the other part of this research, a novel steel-free UHPC-filled FRP tube (UHPCFFT) column system was developed and its cyclic behavior was studied. The proposed steel-free UHPCFFT column showed much higher strength and stiffness, with a reasonable ductility, as compared to its conventional reinforced concrete (RC) counterpart. Using the results of the first phase of column tests, a second series of UHPCFFT columns were made and studied under pseudo-static loading to study the effect of column parameters on the cyclic behavior of UHPCFFT columns. Strong correlations were noted between the initial stiffness and the stiffness index, and between the moment capacity and the reinforcement index. Finally, a thorough analytical study was carried out to investigate the seismic response of the proposed steel-free UHPCFFT columns, which showed their superior earthquake resistance, as compared to their RC counterparts.

La sostenibilidad de los edificios y de las infraestructuras públicas es un tema de importancia reciente puesto en discusión por la comunidad de ingeniería. La necesidad de diseñar estructuras con bajos requerimientos de mantenimiento y durabilidad a largo plazo puede ser resuelta mediante la introducción de nuevos materiales de construcción o la implementación de sistemas estructurales innovadores. En este sentido, los polímeros reforzados con fibras (FRP) representan una de las soluciones en el campo de la ingeniería civil que ofrecen resultados prometedores. Para optimizar el uso de secciones de FRP los investigadores han propuesto la creación de sistemas híbridos donde se combinan materiales compuestos con materiales convencionales, tales como el hormigón. Las soluciones híbridas mejoran la rigidez, la ductilidad y la resistencia a pandeo de los elementos aislados de material compuesto. Debido a la novedad y a la variedad de soluciones híbridas, la tecnología requiere de la realización de más ensayos experimentales para valorar su viabilidad. Además, en la actualidad hay una falta de códigos prescriptores y normas que ayuden al diseño de estructuras construidas con perfiles compuestos y, por consiguiente, los elementos mixtos requieren del desarrollo de modelos predictivos fiables. Por lo tanto, la presente investigación tiene como objetivo estudiar el comportamiento estructural de vigas híbridas hechas de perfiles pultrusionados de FRP unidos a losas de hormigón, mediante la realización de una investigación experimental, analítica y numérica. Puesto que los efectos de deslizamiento en la interfaz han sido mayoritariamente ignorados en el pasado, la tesis se centra también en la influencia de la flexibilidad de la conexión sobre el comportamiento de flexión. Con respecto a la campaña experimental, se han fabricado y ensayado a flexión ocho vigas de perfiles de FRP de fibra de vidrio (GFRP) y hormigón, con conectores mecánicos en el rasante. También se ha comparado su comportamiento con respecto a vigas de hormigón armado equivalentes y perfiles estructurales individuales de GFRP. Previamente a dichos ensayos, se propuso un procedimiento eficaz de caracterización no destructiva para la obtención de las propiedades elásticas de los materiales que componían los especímenes, mediante el uso de un análisis de la respuesta a la vibración libre. En general, los ensayos de flexión han demostrado la alta eficiencia estructural de la solución de viga híbrida y han subrayado la importancia de tener en cuenta la flexibilidad de conexión del rasante. También se ha desarrollado un procedimiento analítico para el diseño de vigas mixtas de FRP-hormigón bajo cargas a corto plazo. Se han propuesto ecuaciones de diseño para los estados límite de servicio y último en función de la interacción completa o parcial del rasante. Además, se ha analizado la viabilidad de utilizar fórmulas aproximadas para cuantificar los efectos del deslizamiento entre capas y su repercusión en la evaluación de los desplazamientos, la rigidez a flexión, la capacidad de flexión y las distribuciones de tensiones. Debido a la mejora de la precisión de las expresiones que representan la flexibilidad de la conexión del rasante, el procedimiento analítico propuesto ha sido capaz de capturar de manera adecuada el comportamiento estructural. Por último, en referencia a los análisis numéricos, se han desarrollado modelos de elementos finitos capaces de simular el comportamiento fundamental de vigas híbridas con conectores tipo perno. El modelo que representó las no linealidades en el material, en los contactos y en la geometría fue el que ofreció los mejores resultados en comparación con los datos experimentales y las estimaciones analíticas. El aplastamiento del hormigón en la losa y su fisuración, los efectos de rigidización post fisuración, la fricción de la interfaz y el comportamiento elasto-plástico de los conectores fueron tomados en consideración.
Sustainability of buildings and public infrastructure is a relatively recent topic put into discussion by the engineering community. A solution to designing structures that have long-term durability and low maintenance requirements is to introduce new construction materials or to implement new structural systems. In this regard, fiber reinforced polymers (FRP) represent one of the novel solutions in the civil engineering field that offer promising results. To optimize the use of FRP shapes, researchers have proposed to form hybrid structural systems by combining the composite materials with conventional materials, such as concrete, in order to improve on the stiffness, ductility, and buckling resistance of single FRP members. However, due to the novelty and wide variety of hybrid elements, the technology demands further experimental testing to prove its viability. In addition, because there is a current lack of mandatory codes for the design of structures built with composite profiles and consequently FRP-concrete members, reliable predictive models have to be developed. Addressing the above-mentioned issues is essential in lessening the introduction of advanced composite materials in common types of public works and constructions. The present research aimed thus to study the structural performance of hybrid beams made of FRP pultruded profiles attached to concrete slabs by carrying an experimental, analytical, and numerical investigation. Since interface slip effects had been largely overlooked in the past, the thesis focused also on the influence of the connection flexibility over bending behavior. With respect to the developed experimental campaign, eight glass FRP-concrete hybrid beams with mechanical shear connectors were fabricated and their flexural behavior was assessed against that of equivalent reinforced concrete beams and single GFRP structural profiles. The variables of the research were the type of hybrid cross-section and the concrete strength class. The laboratory campaign was divided in two phases depending on the specific test setup configuration, and observations were made regarding the short-term behavior of the novel elements under positive bending moments. Previous to the experimental tests, a nondestructive characterization procedure was proposed for obtaining the elastic properties of the constitutive materials of hybrid members in a reduced amount of time, by using an analysis of the free vibration response. Overall, the bending tests have demonstrated the high structural efficiency of the hybrid beam solution and have underlined the importance of accounting for shear connection deformability. An analytical procedure was introduced for the design of FRP-concrete beams under short-term loading. Design equations for the serviceability and ultimate limit states were proposed in function of complete or partial shear interaction assumptions. The feasibility of using simplified formulas to quantify for interlayer slip effects was studied in evaluating deflections, flexural stiffness, bending capacities, normal and shear stress distributions. Due to the improved precision of the expressions that had considered the shear connection flexibility, the proposed analytical procedure was able to capture appropriately the structural behavior and performance of the specimens. Finally, referring to the numerical analyses, predictive finite element models capable of simulating the fundamental behavior of FRP-concrete beams with bolted joints were developed. The model that included material, contact, and geometry nonlinearities offered the best results in comparison with the experimental data and analytical estimations. Concrete slab crushing and cracking, tension stiffening effects, interface friction, and the elasto-plastic behavior of the shear connectors were all taken under consideration.

Textile reinforced concrete (TRC) is an innovative composite material, which is being intensely and practice-oriented investigated on national and international level. In the last few years this material has gained increasing importance in the field of civil engineering. In the context of the collaborative research project SFB 532 at the RWTH Aachen University, research was carried out to understand and to predict the behaviour of different yarn structures in fine grained concrete. Based on the results, innovative commingling yarns were made of alkali-resistant glass fibres and water soluble PVA. These hybrid yarns have an open structure, which improves the penetration of the textile reinforcement by the concrete matrix. Hence, the load bearing capacity of TRC structural elements was significantly improved. This paper presents a technique for the production of such commingling yarns for concrete applications. The mechanical properties of the new yarns are determined due to tensile stress tests. The bond behaviour of the commingling yarns was investigated by pull-out- and tensile stress tests on TRC-specimens. The results of the different tests are being presented and briefly discussed.

This thesis presents the results of a research program examining the effects of macro-synthetic fibers on the shear and flexural behaviour of high-strength concrete (HSC) beams subjected to static and blast loads. As part of the study, a series of seventeen fiber-reinforced HSC beams are built and tested under either quasi-static four-point bending or simulated blast loads using a shock-tube. The investigated test parameters include the effects of: macro-synthetic fibers, fiber hybridization, combined use of fibers and stirrups and longitudinal steel ratio and type. The results show that under slowly applied loads, the provision of synthetic fibers improves the shear capacity of the beams by allowing for the development of yield stresses in the longitudinal reinforcement, while the combined use of synthetic fibers and stirrups is found to improve flexural ductility and cracking behaviour. The results also show that the provision of synthetic fibers delays shear failure in beams tested under blast pressures, with improved control of blast-induced displacements and increased damage tolerance in beams designed with combined fibers and stirrups. The study also shows that the use of hybrid fibers was capable of effectively replacing transverse reinforcement under both loading types, allowing for ductile flexural failure. Moreover, the use of synthetic fibers was effective in better controlling crushing and spalling in beams designed with Grade 690 MPa high-strength reinforcement. Furthermore, the results demonstrate that synthetic fibers can possibly be used to relax the stringent detailing required by modern blast codes by increasing the transverse reinforcement hoop spacing without compromising performance. As part of the analytical study, the load-deflection responses (resistance functions) of the beams are predicted using sectional (moment-curvature) analysis, as well as more advanced 2D finite element modelling. Dynamic resistance functions developed using both approaches, and incorporating material strain-rate effects, are then used to conduct non-linear single-degree-of-freedom (SDOF) analyses of the blast-tested beams. In general, the results show that both methods resulted in reasonably accurate predictions of the static and dynamic experimental results.

In den letzten Jahren gewinnt der Leichtbau im Bauwesen im Zuge der Ressourceneinsparung wieder stärker an Bedeutung, denn ohne eine deutliche Steigerung der Effizienz ist zukunfts-fähiges Bauen und Wohnen nur schwer zu bewerkstelligen. Optimiertes Bauen, im Sinne der Errichtung und Unterhaltung von Bauwerken mit geringem Einsatz an Material, Energie und Fläche über den gesamten Lebenszyklus eines Gebäudes hinweg, bedarf des Leichtbaus in punkto Material, Struktur und Technologie. In der vorliegenden Arbeit wird ein wissenschaftlicher Überblick zum aktuellen Stand der eigenen Forschungen in Bezug auf funktionsintegrativen Leichtbau im Bauwesen gegeben sowie erweiterte Methoden und Ansätze abgeleitet, die eine Konzeption, Bemessung und Erprobung von neuartigen Hochleistungs-Tragstrukturen in Leichtbauweise gestatten. Dabei steht die Entwicklung leistungs-starker und zugleich multifunktionaler Werkstoffkombinatio-nen und belastungsgerecht dimensionierter Strukturkomponenten unter dem Aspekt der Gewichtsminimalität in Material und Konstruktion im Fokus. Ein breit gefächertes Eigen-schaftsprofil für \"maßgeschneiderte\" Leichtbauanwendungen besitzen textilverstärkte Ver-bundbauteile, denn sowohl die Fadenarchitektur als auch die Matrix können in weiten Berei-chen variiert und an die im Bauwesen vorliegenden komplexen Anforderungen angepasst werden. In der vorliegenden Arbeit werden hierzu vor allem Methoden und Lösungen anhand von Beispielen zu: multifunktionalen Faser-Kunststoff-Verbunden (FKV), funktionsintegrier-ten faserverstärkten mineralischen Tragelemente und Verbundstrukturen in textilbewehrter Beton-GFK-Hybridbauweise betrachtet. Von zentraler Bedeutung ist dabei die Schaffung von materialtechnischen, konstruktiven und technologischen Grundlagen entlang der gesamten Wertschöpfungskette – von der Leichtbauidee über Demonstrator und Referenzobjekt bis hin zur technologischen Umsetzung zur Überführung der Forschungsergebnisse in die Praxis
In the last few years, lightweight construction in the building sector has gained more and more importance in the course of resource saving. Without a significant increase in efficiency, future-oriented construction and resource-conserving living is difficult to achieve. Optimized building, in the sense of the erection and maintenance of buildings with little use of material, energy and surface over the entire life time cycle of a building, requires lightweight design in terms of material, structure and technology. In this thesis, a scientific overview of the current state of research on function-integrative light-weight construction in architecture is presented. Furthermore, advanced methods and research approaches were developed and applied, that allows the design, dimensioning and testing of novel high-performance supporting structures in lightweight design. The focus is on the development of high-performance, multi-functional material combinations and load-adapted structural elements, under the aspect of weight minimization in material and construction. Textile-reinforced composites have a broad range of material properties for optimized \"tailor-made\" lightweight design applications, since the thread architecture as well as the matrix can be varied within wide ranges and can adapted to the complex requirements in the building industry. Within the scope of this thesis, methods and solutions are examined in the field of: multifunc-tional fiber-reinforced plastics (FRP), function-integrated fiber-reinforced composites with mineral matrix (TRC) and textile-reinforced hybrid composites (BetoTexG: combination of TRC and FRP). In this connection the creation of material, structural and technological foundations along the entire value chain is of central importance: From the lightweight design idea to the demonstrator and reference object, to the technological implementation for the transfer of the research results into practice

In den letzten Jahren gewinnt der Leichtbau im Bauwesen im Zuge der Ressourceneinsparung wieder stärker an Bedeutung, denn ohne eine deutliche Steigerung der Effizienz ist zukunfts-fähiges Bauen und Wohnen nur schwer zu bewerkstelligen. Optimiertes Bauen, im Sinne der Errichtung und Unterhaltung von Bauwerken mit geringem Einsatz an Material, Energie und Fläche über den gesamten Lebenszyklus eines Gebäudes hinweg, bedarf des Leichtbaus in punkto Material, Struktur und Technologie. In der vorliegenden Arbeit wird ein wissenschaftlicher Überblick zum aktuellen Stand der eigenen Forschungen in Bezug auf funktionsintegrativen Leichtbau im Bauwesen gegeben sowie erweiterte Methoden und Ansätze abgeleitet, die eine Konzeption, Bemessung und Erprobung von neuartigen Hochleistungs-Tragstrukturen in Leichtbauweise gestatten. Dabei steht die Entwicklung leistungs-starker und zugleich multifunktionaler Werkstoffkombinatio-nen und belastungsgerecht dimensionierter Strukturkomponenten unter dem Aspekt der Gewichtsminimalität in Material und Konstruktion im Fokus. Ein breit gefächertes Eigen-schaftsprofil für \"maßgeschneiderte\" Leichtbauanwendungen besitzen textilverstärkte Ver-bundbauteile, denn sowohl die Fadenarchitektur als auch die Matrix können in weiten Berei-chen variiert und an die im Bauwesen vorliegenden komplexen Anforderungen angepasst werden. In der vorliegenden Arbeit werden hierzu vor allem Methoden und Lösungen anhand von Beispielen zu: multifunktionalen Faser-Kunststoff-Verbunden (FKV), funktionsintegrier-ten faserverstärkten mineralischen Tragelemente und Verbundstrukturen in textilbewehrter Beton-GFK-Hybridbauweise betrachtet. Von zentraler Bedeutung ist dabei die Schaffung von materialtechnischen, konstruktiven und technologischen Grundlagen entlang der gesamten Wertschöpfungskette – von der Leichtbauidee über Demonstrator und Referenzobjekt bis hin zur technologischen Umsetzung zur Überführung der Forschungsergebnisse in die Praxis.
In the last few years, lightweight construction in the building sector has gained more and more importance in the course of resource saving. Without a significant increase in efficiency, future-oriented construction and resource-conserving living is difficult to achieve. Optimized building, in the sense of the erection and maintenance of buildings with little use of material, energy and surface over the entire life time cycle of a building, requires lightweight design in terms of material, structure and technology. In this thesis, a scientific overview of the current state of research on function-integrative light-weight construction in architecture is presented. Furthermore, advanced methods and research approaches were developed and applied, that allows the design, dimensioning and testing of novel high-performance supporting structures in lightweight design. The focus is on the development of high-performance, multi-functional material combinations and load-adapted structural elements, under the aspect of weight minimization in material and construction. Textile-reinforced composites have a broad range of material properties for optimized \"tailor-made\" lightweight design applications, since the thread architecture as well as the matrix can be varied within wide ranges and can adapted to the complex requirements in the building industry. Within the scope of this thesis, methods and solutions are examined in the field of: multifunc-tional fiber-reinforced plastics (FRP), function-integrated fiber-reinforced composites with mineral matrix (TRC) and textile-reinforced hybrid composites (BetoTexG: combination of TRC and FRP). In this connection the creation of material, structural and technological foundations along the entire value chain is of central importance: From the lightweight design idea to the demonstrator and reference object, to the technological implementation for the transfer of the research results into practice.

Yes
A numerical method for estimating the curvature, deflection and moment capacity of reinforced concrete beams strengthened with prestressed near-surface-mounted (NSM) FRP bars/strips is presented. A sectional analysis is carried out to predict the moment–curvature relationship from which beam deflections and moment capacity are then calculated. Based on the amount of FRP bars, different failure modes were identified, namely tensile rupture of prestressed FRP bars and concrete crushing before or after yielding of steel reinforcement. Comparisons between experimental results available in the literature and predicted curvature, moment capacity and deflection of reinforced concrete beams with prestressed NSM FRP reinforcements show good agreement. A parametric study concluded that higher prestressing levels improved the cracking and yielding loads, but decreased the beam ductility compared with beams strengthened with nonprestressed NSM FRP bars/strips.

Over the years we have been able to overcome the inherent weaknesses of concrete thereby making it more suitable for a wide variety of applications. One major development has been reinforcement by short randomly distributed fibers that remedy weaknesses of concrete such as low crack growth resistance, high shrinkage cracking, low durability, etc. In fiber reinforced concrete, the use of one type of fiber alone helps to eliminate or reduce the effects of only a few specific undesirable properties. It is believed that the use of two or more types of fibers in a suitable combination would not only help improve more properties of concrete, but would also help provide synergy amongst the fibers. This aspect of combining the fibers, i.e. hybridizing the fibers in a rational manner to derive maximum benefits, was studied in this thesis. High performance fiber reinforced concrete, with a matrix strength of about 85 MPa was used. An attempt was made to make the concrete suitable for practical use, with the required workability, air content, density, etc. This was achieved by making use of proper admixtures including silica fume, superplasticizers and an air entraining agent. The amount and type of fibers to be used in the hybrid composites were planned such that the synergistic behavior of the fibers could be evaluated. The basic property of the hybridized material that was evaluated and analyzed extensively was the flexural toughness of the material. The various fiber types used in diverse combinations included macro and micro fibers of steel, polypropylene and carbon. Control mixes, single fiber reinforced concrete mixes, double fiber hybrids and triple fiber hybrids were investigated. Along with flexural toughness, the size effect of micro fibers, plastic shrinkage resistance, pull-out response of a single macro fiber, impact and shear were also studied. Research clearly indicated that there was synergy associated with many fiber types. In particular 2 denier micro polypropylene fibers, when hybridized with the polypropylene macro fibers (HPP) and carbon micro fibers demonstrated maximum synergy. Although significant synergy was observed, it is believed that the synergy is underpredicted in our tests. The minimum volume fraction of macro fibers used for any of the mixes was 0.5% and it appears that this macro fiber volume fraction is too high to observe maximized synergy in the hybrids. This amount of fiber appears to be high enough to make the post peak response of the matrix insensitive to the addition of small dosages of other fibers, such as micro fibers.

There has been much enthusiasm for hybrid fiber reinforced concrete systems, in which two or more types of fibers are combined in the same concrete matrix. On the other hand, the use of self-compacting concrete (SCC), due to its unique fresh properties and social and environmental benefits, is gaining popularity worldwide. Hence, knowledge on the use of hybrid fibers in SCC deserves attention. The scope of this study encompasses two major research focuses. The first involves the production and evaluation of the fresh properties of high strength fiber reinforced self-compacting concrete and a discussion of its key attributes in the fresh state. The second involves the assessment of the mechanical properties and potential synergistic effects of various fibers in SCC. In this study, 23 mixes containing mono, double, and triple blended fibers were made. The hybrid systems were different combinations of micro fibers (carbon, polypropylene, and steel) and macro fibers (steel and polypropylene). For each mix, six 100x100x350 mm beam specimens for flexural toughness tests and six 100x200 mm cylindrical specimens for compression tests were made. Fresh properties of concrete were measured by a slump flow test. On the flowability aspects, it was found that carbon and micro-polypropylene fibers, even at low volume fractions, caused significant reduction in the flowability of SCC. However, introduction of macro fibers of steel and polypropylene in SCC did not reduce the flowability of concrete as much as micro-fibers did. The maximum amount of microfibers in the hybrid system to retain the self-compacting properties of the fresh mix was 0.25% for carbon fibers and 0.15% for micro-polypropylene fibers provided that they were used individually in the hybrid system. When hardened properties of hybrid fiber SCC where considered the study focused on flexural toughness improvements due to the presence of hybrid fibers in the SCC. Micropolypropylene fibers in combination with all types of steel fibers showed a synergistic effect, while carbon fibers were efficient only in one combination with the steel fiber. According to the results of this study, in a hybrid fiber composite, micro fibers improve the ductility of the matrix. This enhanced the performance of the macro fibers in the pullout process, and the hybrid fiber SCC showed higher flexural toughness as compared to SCC with only one fiber.

碩士
逢甲大學
土木工程所
100
In this thesis, the experimental and theoretical results of circular section reinforced concrete (RC) bridge columns retrofitted by Hybrid Carbon Fiber Composites preformed jacketing were introduced. The design of the RC circular bridge columns was based on the old (before 1995) bridge seismic design codes in Taiwan (MOTC, 1987).The benchmark tests of bridge column with flexural failure modes as tested in the National Center for Research on Earthquake Engineering (NCREE). A scale down concrete column with a diameter of 0.6 m and 2.2 m in height incorporated with insufficient axial reinforcement was designed as the prototype to test its seismic resistance during cyclic lateral loadings. Concrete column was laterally cyclic loaded till the main bar reached the initial yielding, and then retrofitted with hybrid CFRP preformed jacket was laterally pushed to evaluate its seismic resistance. In addition, an undamaged concrete column same as the prototype was retrofitted directly to upgrade its ductility during the earthquake. From the cyclic lateral push-over test, it shows that the hybrid CFRP preformed jacket can increase the peak lateral forces by 12.9 % and 18.9 %, respectively for the pre-damaged and upgraded concrete columns. The seismic ductility can increase 54.3 % and 153.9 %, respectively. This hybrid CFRP preformed jacket can improve the ductility of bridge columns without changing their original structural behaviors. The preformed hybrid CFRP jacket can also save the time of rehabilitation and have good control of the material properties in the factory.

Yes
This paper presents the experimental results of five large-scale hybrid glass fiber reinforced polymer (GFRP)-steel reinforced concrete continuous beams compared with two concrete continuous beams reinforced with either steel or GFRP bars as reference beams. In addition, two simply supported concrete beams reinforced with hybrid GFRP/steel were tested. The amount of longitudinal GFRP, steel reinforcements and area of steel bars to GFRP bars were the main investigated parameter in this study. The experimental results showed that increasing the GFRP reinforcement ratio simultaneously at the sagging and hogging zones resulted in an increase in the load capacity, however, less ductile behaviour. On the other hand, increasing the steel reinforcement ratio at critical sections resulted in more ductile behaviour, however, less load capacity increase after yielding of steel. The test results were compared with code equations and available theoretical models for predicting the beam load capacity and load-deflection response. It was concluded that Yoon's model reasonably predicted the deflection of the hybrid beams tested, whereas, the ACI.440.1R-15 equation underestimated the hybrid beam deflections. It was also shown that the load capacity prediction for hybrid reinforced concrete continuous beams based on a collapse mechanism with plastic hinges at mid-span and central support sections was reasonably close to the experimental failure load.
Higher Education of Libya (972/2007).

No
This paper presents a numerical method for estimating the curvature, deflection and moment capacity of hybrid FRP/steel reinforced concrete beams. A sectional analysis is first carried out to predict the moment-curvature relationship from which beam deflection and moment capacity are then calculated. Based on the amount of FRP bars, different failure modes were identified, namely tensile rupture of FRP bars and concrete crushing before or after yielding of steel reinforcement. Comparisons between theoretical and experimental results of tests conducted elsewhere show that the proposed numerical technique can accurately predict moment capacity, curvature and deflection of hybrid FRP/steel reinforced concrete beams. The numerical results also indicated that beam ductility and stiffness are improved when steel reinforcement is added to FRP reinforced concrete beams. (C) 2015 Elsevier Ltd. All rights reserved,

Fiber reinforcement is being widely used in concrete tunnel linings these days. Using fiber reinforcement can save not only cost, but also labor and time spent on construction. However, many owners hesitate to incorporate fiber reinforcement in tunnel lining due to lack of experience with and knowledge of the behavior of fiber reinforced concrete (FRC) In this study, fiber reinforced concrete was made with various kinds of fibers such as steel fiber, macro-synthetic fiber and hybrid fiber (a blend of macro-synthetic fiber and glass fiber). Many experimental tests were performed to investigate the compressive, flexural and shear behavior of fiber reinforced concrete. In addition to the structural capacity of FRC, the distribution of fiber reinforcement inside the concrete matrix was investigated. Test results of these experimental tests were thoroughly examined to compare and quantify the effects of fiber reinforcement. Next, the test results were used to generate axial force-bending moment interaction diagrams based on current design approaches. In addition, the current design approaches were modified to estimate the accurate and exact value of bending moment. Fiber reinforcement clearly improved the structural performance of tunnel lining. The post-peak flexural and shear strength was significantly influenced by the type and amount of fiber reinforcement.
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碩士
國立中興大學
土木工程學系所
104
At elevated temperatures, the microstructure and mechanical properties of concrete may significantly deteriorate and thus affect the bond between steel rebar and concrete. The review of literature indicates that little research has been undertaken to investigate the role of fibers in maintaining post-heating bond between concrete and reinforcing steel. In view of this, this study aims to investigate the residual mechanical properties of high performance fiber reinforced concrete (FRC) after exposure to different high temperatures. The parameters investigated include type of concrete and fiber, concrete strength, and temperature. The specimens were divided into two groups to study the effect of addition of various amounts of fiber on its residual mechanical properties (compressive strength, elastic modulus, flexural strength, and bond strength) and the bond strength-slip response after exposure to temperature levels of 400°C, 600°C and 800°C in addition to the room temperature and holding temperature for one hour. The test results showed that after exposure to 400 °C, 600 °C and 800 °C, the high strength FRC mixes retained, respectively, 88%, 69% and 23% of their compressive strength, on average. The results also show that after the high strength FRC was exposed to the elevated temperatures, the loss of elastic modulus was much quicker than the loss in compressive strength. The test results showed that both at room temperature or elevated temperature, the load deflection curve of FRC has better fracture toughness. In addition, the typical load–deflection response of FRC was a double-peak response. The first peak represented the properties of concrete matrix and the second peak represented the properties of the steel fibers used. At a temperature of 400 °C, the flexural load of each concrete significantly increased; in particular fiber concrete, its residual flexural load ratio reached 1.3 or more. However, a significant decrease in strength, toughness and load–deflection response was observed when the temperature approached 800 °C. On the other hand, after exposure to 400 °C, 600 °C and 800 °C, the hybrid fiber reinforced concrete mixes retained, respectively, 107%, 100% and 57% of their bond strength, which are better than that for control concrete.

博士
國立中興大學
土木工程學系所
100
This research contains four themes. Firstly, the research investigated the abrasion resistance of steel-polypropylene hybrid fiber-reinforced concrete (SPHFRC). Of the steel fiber (S) types, S1, S2, and S3 were hooked-end and S4 was crimped and additional fiber type was polypropylene (P). The L16 orthogonal array and analysis of variance (ANOVA) method were applied to analyze the interaction effects on the mechanical properties of SPHFRC. The analytical results demonstrate that P fibers contributed most to compressive strength, and S2 fibers contributed most to the modulus of rupture (MOR). For abrasion resistance, P fibers contributed most of abrasion resistance during the initial stage, while S2 fibers contributed most during the final stage. The R2 for accumulated abrasion resistance with compressive strength declined as abrasion increased. The R2 for accumulated abrasion resistance with MOR increased as abrasion increased. For interaction effects, P×S1 and P×S2 reached a significant level of compressive strength; S1×S3 and S2×S3 reached a significant level of MOR; P×S1 and P×S2 reached a significant level of abrasion resistance during the initial stage; and S1×S3 and S2×S3 reached a significant level of abrasion resistance during the final stage. Secondly, the nylon fibers (N) possess better engineering properties than polypropylene fibers. This study investigated the mechanical properties of steel-nylon hybrid fiber-reinforced concrete. The contents of nylon fibers were 0 kg/m3 and 0.6 kg/m3, the contents of polypropylene fibers were 0 kg/m3 and 0.6 kg/m3, and the contents of steel fibers were 0 kg/m3 and 15 kg/m3. The L8 orthogonal array and ANOVA method were adopted to analyze the interaction effects on the mechanical properties of hybrid fiber-reinforced concrete. The results showed the nylon fibers contributed the most to compressive strength, and the steel fibers contributed the most to splitting tensile strength and modulus of rupture. N×S1 reached a very significant level of compressive strength; P×S1 reached a significant level of compressive strength; N×S1 reached a very significant level of splitting tensile strength and MOR. Thirdly, steel fibers can easily result in balling while mixing with a high content and basset and rust for a long period working time. To overcome these disadvantages, coarse monofilament polypropylene fibers have been developed. This study investigated the mechanical properties of polypropylene hybrid fiber-reinforced concrete (PHFRC). Two types of polypropylene fibers, coarse monofilament fibers (P1) and fibrillated fibers (P4) were used in the experiment. Taguchi method was adopted to determine the optimal levels for PHFRC. The results have shown that P4 contributed more to compressive strength than P1 did, but P1 contributed much more to MOR than P4 did. During the initial stages, P4 contributed more to abrasion resistance than P1 did; however, during the middle and final stages, the contribution of P1 to abrasion resistance exceeded that of P4. During final stage, excessive content of P1 may lead to adverse effects to abrasion resistance. As the duration of abrasion increased, the relationship between abrasion resistance and compressive strength decreased, while the relationship between abrasion resistance and MOR increased. Last, this research uses three different aspect ratios of coarse polypropylene fibers and one type of fine polypropylene fibers adding into concrete, and employs three groups of L16 orthogonal arrays and the response surface method to investigate the optimal mechanical properties such as compressive strength, splitting tensile strength and MOR. The results shows the interaction effect of coarse fibers and fine fibers reach a significant level on compressive strength, splitting tensile strength and MOR. In summary, the nylon fibers can replace the polypropylene fibers to increase performances of concrete and the coarse monofilament polypropylene fibers can significantly increase MOR and splitting tensile strength of concrete. When the compressive strength of concrete is increased, the fibers still can reinforce the mechanical properties of concrete.

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

碩士
國立臺北科技大學
建築系建築與都市設計碩士班
107
In order to alleviate the global warming phenomenon, reduce the emission of carbon dioxide as a target and reduce the environmental burden caused by the building materials production process and construction process, the widespread use of timber structure is a better choice. There are many types of timber structure methods, including the traditional post and beam method, the wood frame construction method, two-by-four method and the emerging form of the new CLT(Cross-Laminated-Timber Cross-Laminated-Timber) method, etc.In recent years, on the use of timber structure, in addition to the use of wood for small-scale building, various countries are actively constructing medium and large-scale timber buildings. For the large-scale timber buildings are needed to be constructed, in addition to timber structure, Steel framed structure and Reinforced Concrete buildings are required to be constituted as a Timber-Concrete Hybrid Structures. While the mixed structures are divided into plan Hybrid Structures, vertical Hybrid Structures, and plan-vertical Hybrid Structures. The purpose of this study is to analyze and compare the similarities and differences in Building Standards Act and Timber-Concrete Hybrid Structures cases between China, Japan, the United States, and Austria, etc., further to investigate some strategies from their basis to help promoting indigenous Timber-Concrete Hybrid Structures in Taiwan. On the results of the study, construction of the CLT the combination of the Hybrid Structures will be considered for future construction, and should be based on the building reference method, fire resistance specifications and climate. The conditions are more consistent with the Japanese Hybrid Structures construction reference to the Taiwan Hybrid Structures construction.