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Fibre-Reinforced Polymer (FRP) Composites
Abstract
The first part of this chapter focuses on the constituent materials (fibres and polymeric matrices), manufacturing processes, general properties and field of application of fibre reinforced polymer (FRP) composites used in civil engineering applications. Subsequently, detailed information is provided about the following three main types of FRP shapes used in structural applications: (1) glass fibre-reinforced polymer (GFRP) pultruded profiles; (2) FRP rebars and (3) FRP strengthening systems. For each of these three main FRP typologies, the following aspects are discussed: geometries, typical physical and mechanical properties, advantages and difficulties compared to more traditional construction materials, field of application, application process and connection technology, and regulation.
... The main characteristics of pGFRP are high mechanical strength, low specific mass and great durability, which lead to resistant, light and easily assembled structures. Civil engineering applications of pGFRP go from secondary structures like ladders, handrails and walkways to main elements of bridges, footbridges and cooling towers (Correia, 2015;Qureshi, 2022). ...
Cooling towers are industrial equipment characterized by heavy components, large wind obstruction area and elevated humidity. High mechanical strength, low specific mass and great durability of pGFRP make it suitable for this type of structures, but little is found in scientific literature about their structural performance. The low modulus of elasticity of pGFRP makes the structures more flexible, susceptible to large displacements and vibration. This work assesses the contribution of two bracing systems to the free vibration behavior of a pGFRP cooling tower, aiming to increase its stiffness and avoid resonance due to low frequency loads such as wind fluctuation.
... Indeed, when sandwich panels are exposed to high temperatures (300-500 • C), polymeric foams decompose, releasing heat, smoke and toxic gases. Additionally, when exposed to moderate temperatures (60-200 • C), the mechanical performance of sandwich panels (strength and stiffness) undergoes significant reductions [5][6][7][8]. For this reason, legitimate concerns have been raised about the fire performance of foam-filled sandwich panels, which hinder their application in buildings, where strict fire safety requirements must be met. ...
Polymeric foams used as core materials of sandwich panels undergo severe degradation under high temperatures, making the experimental measurement of their thermophysical properties (thermal conductivity and specific heat) possible only up to 150 °C–200 °C. However, their knowledge at higher temperatures is needed to fully understand their behaviour and to develop advanced numerical models for analysis and design of sandwich structures subjected to fire. This work presents a numerical inverse analysis procedure to determine such effective properties for rigid polyurethane (PUR) and polyethylene terephthalate (PET) foams. Firstly, the campaign used to obtain experimental results is presented and then the proposed numerical inverse analysis procedure is described. This is based on the minimization of a least squares functional and a nonlinear finite element thermal analysis. Next, the numerical results and the effective thermophysical properties obtained for both foams are presented and discussed, and are validated by extending their use to the simulation of the thermal response of a sandwich panel subjected to a standard fire. It is concluded that the numerical procedure is capable of estimating the temperature-dependent effective thermal conductivity and specific heat of PUR and PET foams for temperatures well above those corresponding to their decomposition.
... Among thermoset matrices, unsaturated polyesters are the most often used, due to their lower cost when compared to epoxies and vinylester [49]. Although unsaturated polyesters are most suited for structural applications subjected to less aggressive exposure conditions, they are versatile and their processing, mechanical and thermomechanical properties are suitable to produce glass fibre reinforced polymer (GFRP) profiles, laminates, strips, and other composite structural parts [50]. Unsaturated polyesters are typically used to impregnate glass fibre reinforcement [51]; however, they are also compatible with several other types of reinforcing fibres, such as basalt and (although less commonly) carbon [52][53][54][55]. ...
This paper presents the manufacturing and the mechanical and thermomechanical properties of a bio-based glass fibre-reinforced polymer (GFRP) composite, produced by vacuum infusion, using an in-house high-performance bio-based unsaturated polyester resin (UPR) with more than 50 wt.% of its content derived from renewable raw materials. Specimens were successfully produced, and their mechanical and thermomechanical properties was compared to an equivalent GFRP composite produced with conventional petroleum-based UPR and the same fibre architecture. The bio-based GFRP composite presented 538 MPa, 210 MPa, and 52 MPa of tensile, compressive, and shear strengths; 20 GPa, 24 GPa, and 2.5 GPa of tensile, compressive, and shear moduli; and 3.0%, 0.8%, and 14.8% of tensile, compressive, and shear strain at failure, meeting or exceeding the mechanical properties of the conventional counterpart. Furthermore, the bio-based GFRP composite presented a Tg of 64 °C (defined from onset of the storage modulus decay), enabling its outdoors use.
... During the second half of the twentieth century, glass fibre reinforced polymer (GFRP) materials found increasing use in civil engineering applications, either in the rehabilitation of degraded structures or in new construction, owing to their advantages over traditional materials, such as high strength-to-weight ratio, lightness, corrosion resistance and low life cycle costs [1,2]. In spite of such advantages, there are major concerns about the behaviour of GFRP materials when subjected to elevated temperature or fire, which have been hindering their widespread use in several civil engineering applications, namely in buildings, where the fire action has to be considered in design. ...
One of the main concerns about the use of fibre reinforced polymer (FRP) materials in civil engineering is their behaviour when subjected to elevated temperatures and under fire exposure. In fact, considerable reductions in the mechanical properties of FRP materials have been reported even at moderately elevated temperatures (e.g. 50–150 °C), due to the glass transition of their polymeric matrices. Most previous studies on this topic have focused on the mechanical characterization at elevated temperatures of quasi-unidirectional pultruded FRP composites, namely profiles, rebars and strips; much less data is available about FRP materials produced with different methods with more balanced fibre architectures. This paper aims at contributing to fulfil this knowledge gap by presenting experimental and analytical investigations about the effects of elevated temperatures on the mechanical properties of glass-FRP (GFRP) laminates produced by vacuum infusion, with a balanced fibre architecture, representative of typical GFRP face sheets of sandwich panels used in civil engineering structures. The experimental programme included (i) tensile tests up to 300 °C, (ii) compressive tests up to 250 °C, and (iii) shear tests up to 200 °C, all under steady state conditions, as well as dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA). The results obtained confirm that the mechanical properties of the GFRP laminates are severely affected by the temperature increase, especially those that are matrix-dependent: compared to room temperature, at 200 °C, the shear modulus was reduced by 88%, whereas the compressive strength and modulus were reduced by 96% and 67%, respectively. The tensile properties (fibre-dominated) were much less affected - at 200 °C, the tensile strength and modulus were reduced by 40% and 48%, respectively. Finally, the suitability of four empirical models and of a design-oriented temperature conversion factor to take into account the variation of the GFRP mechanical properties with temperature was assessed. Overall, the empirical models presented good agreement with the test data, and the temperature conversion factor provided conservative estimates of the material properties, attesting its suitability for design purposes.
... This process is extensively used in every field of engineering -from the automotive industry, through the aviation and maritime industries [17,18], to civil engineering [12,14]. All abovementioned industries have in common one more thing: the rapidly increasing popularity of the usage of composite materials [7]. ...
Experimental tests and numerical simulations of a full-scale segment of a foot and cycle bridge made of polymer composites are presented in the paper. The analysed structure is made of sandwich panels, which consist of glass fibre reinforced polymer (GFRP) multi-layered laminate faces and a PET foam (obtained from recycling) core. The dimensions of the segment cross-section are the same as for the target footbridge; however, span length was reduced to 3 m.
The experimental tests were conducted in a laboratory of the Faculty of Ocean Engineering and Ship Technology at Gdansk University of Technology. A single vertical force was generated by a hydraulic cylinder and was applied to the platform of the structure. The experimental tests were supported by numerical analyses performed in Femap with NX Nastran software by means of the finite element method (FEM). Results obtained in the computational model were compared with results from experiments. Thus, the numerical model was validated and the obtained conclusions were used in the next step of the design process of a composite footbridge with a span length of 14.5 m.
... To reach this level of performance, the fibers are produced through complex processes (Chawla, 2012) that are very energy-consuming. This, of course, increases the cost and the environmental footprint considerably (Correia, 2015). When a composite product reaches its end-of-life, it can be either landfilled, incinerated, or recycled. ...
Environmental issues such as climate change are leading to sustainability challenges for the aerospace industry. New materials such as composites allow significant weight reduction, which leads to a lower fuel consumption. However, composites involve complex processes and there is a lack of knowledge on their social and environmental consequences. Through two cases based on real aero-engines components, this paper shows that the weight savings provided by composites reduce significantly the CO2 emissions during flight which compensates the environmental drawbacks from production and recycling.
... FRP is a composite material consisting of small longitudinal fibres embedded in a polymeric resin matrix. 4 The fibres come in various forms (Glass, Carbon, Aramid and Basalt) and provide the strength and stiffness in the longitudinal direction, while the epoxy resin transfers load to the fibres and protects them from environmental degradation. Of the available fibre types, Glass Fibre-Reinforced Polymer (GFRP) proves to be the most economically viable. ...
FRP materials, though having been around for several decades, are seeing increasing uptake in the structural engineering domain. In New Zealand, the use of FRP sheets is especially common in the seismic retrofit of buildings and bridges, though there is still minimal use of FRP bars as internal reinforcement. A number of typical uses of FRP materials are shown, highlighting the different solutions offered by the material as well as the developing familiarity of engineers and contractors of the material. Then, the direction of research into the use of FRP is touched on, showcasing the progress made in understanding FRP-reinforced and retrofitted structures and what could be next in terms of potential applications of the material. The applications discussed showcase that versatility of the material allows it to be used in a variety of areas in construction, provided more standardised manufacturing techniques are developed and key research questions on their behaviour are answered. Overall, there is a growing awareness of the properties of FRP as a structural material within the construction industry and there is ongoing research to further investigate where and how it can be used in concrete structures in pursuit of improved durability, performance and resilience.
... On the one hand structures are desired to be greater, more durable and reliable together with decreasing cost, but on the other hand requirements for material itself are more demanding -its strength has to be higher together with decreasing mass. To fulfill this needs Fiber Reinforcement Polymers (FRP) with their properties are becoming more and more attractive for architects and designers [1][2][3][4][5], especially in bridge applications [6][7][8]. ...
The paper contains analysis of full-scaled three meters long segment of a novel composite footbridge. Both numerical modeling and experimental validation were performed. Analyzed object is a shell type sandwich channel-like structure made of composite sandwich with GFRP laminates as a skin and PET foam as a core. Several static load schemes were performed including vertical and horizontal forces. In FEM analysis multilayered laminate was modeled by means of Equivalent Single Layer (ESL) method while the foam was assumed as three-dimensional continuum. Results were compared with the ones obtained from experiments. Good agreement in comparison showed the correctness of conducted assumption what was a great support in designing process of fourteen-and-half meters long footbridge.
This paper presents the development and industrial manufacturing of a pultruded high-performance carbon fibre (CF) reinforced polymer (CFRP) composite strip using a bio-based unsaturated polyester (UP) resin containing more than 50% of its weight derived from renewable raw materials. The bio-based CF/UP strengthening strip, comprising unidirectional CF strands, was successfully produced and its mechanical and thermomechanical behaviours were assessed, and compared to an equivalent carbon fibre reinforced epoxy-vinyl ester (CF/VE) strip produced with conventional petroleum-based high-performance epoxy-vinyl ester resin and the same fibre architecture. The bio-based CF/UP composite strip presented 2095 MPa, 167 GPa, and 1.4% of tensile strength, modulus of elasticity, and strain at failure, respectively. These figures met or exceeded the mechanical properties of its equivalent conventional CF/VE counterpart tested under the same conditions. Furthermore, the bio-based CF/UP composite strip presented a glass transition temperature of 78 °C (defined from the onset of the storage modulus decay), enabling a maximum service temperature of ∼60 °C, which will not likely be exceeded in most climates, highlighting its potential for structural strengthening applications, and offering a key advantage in terms of sustainability.
This paper reviews Fibre Reinforced Polymer (FRP) composites in Civil Engineering applications. Three FRP types are used in Structural Engineering: FRP profiles for new construction, FRP rebars and FRP strengthening systems. Basic materials (fibres and resins), manufacturing processes and material properties are discussed. The focus of the paper is on all-FRP new-build structures and their joints. All-FRP structures use pultruded FRP profiles. Their connections and joints use bolting, bonding or a combination of both. For plate-to-pate connections, effects of geometry, fibre direction, type and rate of loading, bolt torque and bolt hole clearance, and washers on failure modes and strength are reviewed. FRP beam-columns joints are also reviewed. The joints are divided into five categories: web cleated, web and flange cleated, high strength, plate bolted and box profile joints. The effect of both static and cyclic loading on joints is studied. The joints’ failure modes are also discussed.
Ultra-high-performance concrete (UHPC) is one of the contemporary overlay materials for repairing and retrofitting of reinforced concrete (RC) members. It possesses excellent compressive and tensile strength, as well as long durability. Nevertheless, the bonding performance between the overlay interface (UHPC) and the substrate concrete must be adequate under various loading, curing, and exposure circumstances. Therefore, this research examined, experimentally, the interfacial bonding behavior of UHPC overlay and two distinct substrates, namely concrete screed (CS) and self-compacted concrete (SCC). Four parameters impacting bond strength behavior, including three different substrate surface preparations, curing conditions, exposure environments, and testing techniques, were used to fulfill the goal of this study. The tests findings revealed that the substrate surface preparation and the exposure conditions had significant effects on the bond behavior of both UHPC-SC and UHPC-SCC while curing conditions seemed not to have any significant effects. The highest bond strength was obtained for specimens having sandblasted substrate preparation technique regardless of the bond test method. However, specimens tested under the bi-surface shear strength technique exhibited high bonding strength with the drill holes substrate preparation technique due to the presence of drilled holes that were being filled with UHPC. The splitting tensile test is a reliable test technique to examine the impact of repeated cyclic exposure samples. As a result of this, a substantial reduction in bond strength of nearly 32%, 55%, and 26% of the UHPC-SCC and 31.84%, 51.5%, and 41.42% for UHPC-SC interfaces for as-cast (AC), drilling hole (DH), and sandblasting (SB) substrate surface preparations, respectively, were obtained. ANOVA was carried out and found to be aligned with the experimental findings.
This paper presents an experimental study about the fire behaviour of reinforced concrete (RC) slabs strengthened with carbon fibre reinforced polymer (CFRP) strips, applied according to three different techniques: externally bonded reinforcement (EBR); near-surface mounted (NSM), and continuous reinforcement embedded at the ends (CREatE), a new technique that prevents premature CFRP debonding. The main goals of this study were three-fold: to understand and compare the fire behaviour of the strengthening techniques, namely the CREatE technique (yet to be studied); to assess the efficiency of the fire protection schemes (constant thickness vs. increased thickness at the CFRP anchorage zones) in extending the fire resistance of the CFRP systems; and, based on the experimental results and data available in the literature, to propose “critical” temperatures for the fire design of CFRP-strengthened RC members. The results obtained show that: (i) without protection, the CREatE technique presented higher fire resistance than the alternative NSM and EBR techniques (24 min vs. 16 min and 2 min); (ii) with fire protection, regardless of its geometry, the NSM and CREatE techniques presented a similar fire resistance (both above 120 min), higher than the EBR technique (less than 60 min); and (iii) the “critical” temperatures for each technique were defined as 1.0Tg, 2.5Tg and 3.0Tg for EBR, NSM and CREatE, respectively, with Tg being the glass transition temperature of the adhesive, defined based on the onset of the storage modulus curve decay from dynamic mechanical analysis.
Parametric optimization of sandwich composite footbridge was presented in the paper. Composite footbridge has 14,5 meters long and has U-shaped cross-section with inner dimensions 2,6 x 1,3 meters. The aim of analysis was to minimize the mass of the new footbridge that can lead to minimize the cost of structure. After optimization was conducted, the new structure was compare with the realized one. The results show that while mass can be decreased the state variables of structure like maximum displacement, strain or natural frequency do not change significantly. Moreover, results show that, although the mass is decreased, stiffness of the new structure is even higher.
Optimization and sensitivity analysis, the divisions of theory of designing, provide the designer a significant support. Despite presented optimization, also sensitivity analysis can additionally be effectively used in issues related to strengthening or modernizing structures as well as in the process of identifying quantities describing the computational model.
Glass-fiber reinforced concrete (GRC) is a material made of a cementitious matrix composed of cement, sand, water and admixtures, in which short length glass fibers are dispersed. It has been widely used in the construction industry for non-structural elements, like façade panels, piping and channels. In this paper, the results of a research project are presented where this material was applied to the fabrication of structural elements, namely 30m high telecommunication towers. Here, the lightness and tensile strength advantages of the GRC were associated with carbon and stainless steel reinforcement, leading to an innovative material with high durability.
The lack of a comprehensive, validated, and easily accessible data base for the durability of fiber-reinforced polymer FRP composites as related to civil infrastructure applications has been identified as a critical barrier to widespread acceptance of these materials by structural designers and civil engineers. This concern is emphasized since the structures of interest are primarily load bearing and are expected to remain in service over extended periods of time without significant inspection or maintenance. This paper presents a synopsis of a gap analysis study undertaken under the aegis of the Civil Engineering Research Foundation and the Federal Highway Administration to identify and prioritize critical gaps in durability data. The study focuses on the use of FRP in internal reinforcement, external strengthening, seismic retrofit, bridge decks, structural profiles, and panels. Environments of interest are moisture/solution, alkalinity, creep/relaxation, fatigue, fire, thermal effects including freeze-thaw, and ultraviolet exposure.
Results of an experimental research into the physical, chemical, mechanical, and aesthetical changes suffered by pultruded
glass-fiber-reinforced polyester profiles during their testing for accelerated aging under the action of moisture, temperature,
and ultraviolet (UV) radiation are presented. The profiles were submitted to the influence of four different exposure environments:
(i) in an immersion chamber, (ii) in a condensation chamber, (iii) in a QUV accelerated weathering apparatus, and (iv) in
a xenon-arc accelerated weathering apparatus. The results obtained were analyzed regarding the changes in their weight, sorption
ability, tensile and flexural strength characteristics, color, and gloss; the chemical changes were investigated by means
of Fourier-transform infrared spectroscopy. Considerable chromatic changes were observed, especially owing to the UV radiation.
Although some reduction in the mechanical properties was observed, particularly in the immersion and condensation chambers,
the durability tests proved a generally good behavior of this material under the aggressive conditions considered.
p>The aim of the present Structural Engineering Document, a state-of-the-art report, is to review the progress made worldwide in the use of fibre reinforced polymers as structural components in bridges until the end of the year 2000.
Due to their advantageous material properties such as high specific strength, a large tolerance for frost and de-icing salts and, furthermore, short installation times with minimum traffic interference, fibre reinforced polymers have matured to become valuable alternative building materials for bridge structures. Today, fibre reinforced polymers are manufactured industrially to semi-finished products and ccimplete structural components, which can be easily and quickly installed or erected on site.
Examples of semi-finished products and structural components available are flexible tension elements, profiles stiff in bending and sandwich panels. As tension elements, especially for the purpose of strengthening, strips and sheets are available, as weil as reinforcing bars for concrete reinforcement and prestressing members for internal prestressing or external use. Profiles are available for beams and columns, and sandwich constructions especially for bridge decks. During the manufacture of the structural components fibre-optic sensors for continuous monitoring can be integrated in the materials. Adhesives are being used more and more for joining components.
Fibre reinforced polymers have been used in bridge construction since the mid-1980s, mostly for the strengthening of existing structures, and increasingly since the mid-1990s as pilot projects for new structures. In the case of new structures, three basic types of applications can be distinguished: concrete reinforcement, new hybrid structures in combination with traditional construction materials, and all-composite applications, in which the new materials are used exclusively.
This Structural Engineering Document also includes application and research recommendations with particular reference to Switzerland.
This book is aimed at both students and practising engineers, working in the field of fibre reinforced polymers, bridge design, construction, repair and strengthening.
Understanding the performance of fiber-reinforred polymer (FRP)-strengthened members in fire is critical to the widespread application of FRPs as repair materials for infrastructure. An investigation was undertaken to examine and document the performance of FRP-strengthened reinforced concrete T-beams under standard fire conditions. Two full-scale reinforced concrete T-beams were strengthened in flexure with FRP sheets and insulated with a patented two-component fire insulation system. The specimens were subsequently exposed to a standard fire under full sustained service load. Member deflections, strain in the steel reinforcement, and temperatures throughout the section were measured and recorded throughout the tests. A numerical heat transfer model was used to predict temperatures within the section at any time during the fire. The predicted temperatures are compared with those observed during the fire tests and are shown to agree satisfactorily. The results indicate that appropriately designed and insulated FRP-strengthened reinforced concrete T-beams can achieve fire endurances of more than 4 hours.
Glass fiber-reinforced polymer (GFRP) composites have been increasingly used in the construction of civil structures because of their light weight and high strength, tailored flexibility, and corrosion resistance. Such structural materials also present potential for a multifunctional design where functions other than load-carrying capacity, such as thermal insulation, energy supply, and intelligent inspection can be incorporated into one GFRP structural component. This paper further extends this concept by the development of the self-luminous function. In this application, a translucent resin modified with self-luminous powders, together with the nature of glass fibers, is able to illuminate the resulting GFRP composite in darkness and therefore provide the structural members with new architectural and aesthetic features or other service signatures. Mechanical experiments, luminance measurements, and scanning electron microscopy (SEM) imaging have been conducted to examine the self-luminous GFRP composites, and the results are reported in this paper.
This paper presents an experimental and analytical study about the mechanical response at elevated temperature of glass fibre reinforced polymer (GFRP) pultruded profiles. The paper first describes results of DMA and DSC tests that were used to evaluate the glass transition and decomposition processes of the GFRP pultruded material. The paper then describes an extensive study about the tensile, shear and compressive responses of the GFRP material at temperatures varying from 20 °C to 250 °C. In these tests the mechanical responses of the GFRP material as a function of temperature were assessed, namely the load–deflection curves, the stiffness, the failure modes and the ultimate strength. Results obtained in these experiments confirmed that the mechanical performance of GFRP is severely deteriorated at moderately high temperatures, particularly when loaded in shear and compression, owing to the glass transition of the resin. The final part of this paper assesses the accuracy of different empirical models and one phenomenological model to estimate the tensile, shear and compressive strengths of GFRP pultruded material as a function of temperature. All empirical models, including a function based on Gompertz statistical distribution suggested in the present paper, provided accurate estimates of tensile, shear and compressive strengths as a function of temperature. The phenomenological model was less accurate and in general provided non conservative estimates of material strength.
FRP-strengthened reinforced concrete (RC) members experience significant loss of strength and stiffness properties when exposed to fire. At elevated temperatures, the rate of loss of such properties is influenced considerably by the bond degradation at the FRP–concrete interface. This paper presents a numerical approach for modeling the bond degradation in fire exposed FRP-strengthened RC beams. The numerical procedure is incorporated into a macroscopic finite element model which is capable of accounting high temperature material properties, different fire scenarios, and failure limit states in evaluating fire response of FRP-strengthened RC beams. The validity of the model is established by comparing predictions from the program with data from full scale fire resistance tests on FRP-strengthened RC beams. The validated model is applied to evaluate the effect of bond degradation on fire response of FRP-strengthened beams. Results from the analysis indicate that significant bond degradation occurs close to glass transition temperature of the adhesive leading to initiation of FRP delamination. The time at which bond degradation occurs depend on the fire insulation thickness and glass transition temperature of the adhesive. However, variation of adhesive thickness does not significantly influence fire resistance of FRP-strengthened RC beams.
Several building codes are now available for the design of concrete structures reinforced with FRP even if no calculation model taking account of fire conditions has been suggested. Only the Canadian code (CAN/CSA 806-02) provides a design procedure in fire situations based on critical temperature. Furthermore, the literature provides some significant experimental results of failure tests performed on FRP–reinforced concrete members working in flexure that were exposed to conventional fire conditions.Tests recently performed by the authors allowed the behavior of six concrete slabs reinforced with GFRP bars exposed to fire action to be evaluated: four slabs were tested under typical design loads in fire situations (40% and 60% of design bending moment resistance at normal temperature) and two unloaded slabs were tested after the cooling phase in order to evaluate their residual resistance.In the present paper the experimental programme is extensively reported, giving detailed information on tests to highlight the practical significance of the experimental research. The results of investigations are discussed with particular reference to the structural behavior of concrete members once the glass transition temperature in the bars is attained and resin softening reduces adhesion at the FRP-to-concrete interface. Results are shown with the aim of providing suggestions for updating design codes. In a companion paper the pattern of temperatures recorded during the tests by means of thermocouples applied both on the surface of bars and in the concrete are presented in depth and compared with results of numerical simulations.
This paper presents experimental and numerical investigations about the fire behaviour of reinforced concrete (RC) beams flexurally strengthened with carbon fibre reinforced polymer (CFRP) laminates. The main objective was to assess the efficacy of different fire protection systems and to evaluate the viability of their use in floors of buildings. Fire resistance tests were conducted on an intermediate scale oven to investigate the behaviour under fire (ISO 834) of loaded CFRP-strengthened RC beams. The fire protection systems comprised calcium silicate boards and layers of vermiculite/perlite cement based mortar, with thicknesses of 25mm and 40mm, applied along the bottom soffit of the beams that was directly exposed to fire. In addition, the anchorage zones of the CFRP laminates were highly thermally insulated in order to evaluate the benefits of this particular constructive detail. Member deflection and temperatures throughout the midspan section were measured and recorded during the tests. When the strengthening system was left unprotected in the exposed length of the beam, the CFRP laminate anchorage debonded after about 23min. When the above mentioned fire protection materials were applied in the exposed length of the beams, the strengthening system debonded after between 60–89min (25mm thickness) and 137-167min (40mm). Two-dimensional finite element thermal models of all beams tested were also developed in order to predict the evolution of temperatures in the materials. The calculated temperatures compared reasonably well with those measured in the tests.
Mud‐brick is one of the most adaptable and versatile of building materials. Its early use in the Near East is discussed, with particular reference to its employment in elaborate façade decoration, for example in the spiral and palm‐trunk semi‐columns of the Great Temple at Tell al Rimah (c. 1800 BC) and in various types of vault. Evidence is discussed for the contemporary use of three techniques of sun‐dried mud‐brick vaulting ‐ radial, pitched‐brick and corbelled ‐ at least as early as the second half of the third millennium BC.
In June 1997, a fibre-reinforced plastic (FRP) bridge for pedestrians and cyclist was opened at Strandhuse near the Danish town of Kolding. As well as being the first advanced composite bridge in Scandinavia, it has the further distinction of being the first FRP bridge to cross a busy railway line. The cable-stayed bridge is constructed entirely of glass-fibre-reinforced plastic (GFRP). Although data on long-term performance are not yet available, the Kolding experience indicates that FRP is a viable material for minor bridges, for swift erection and minimal maintenance are desirable.
Advanced composite materials, or fiber-reinforced polymer (FRP) composites, have found wide application in recent years in the rehabilitation of structures. Most of the primary structure applications of FRP composites have been as direct replacements for existing structural components, which may not be economically viable due to higher material costs. Therefore, the advantages of FRP, such as their weight, low life-cycle maintenance costs and mechanical tailorability, can only be effectively utilized when the structural systems offer reduced material usage and simplified construction procedures. The Kings Stormwater Channel and I-5/Gilman bridges represent the implementation of state-of-the-art knowledge on the use of FRP composites for civil infrastructure. The designs implement a variety of structural systems developed through several stages of research and development.
Significant research on strengthening reinforced concrete (RC) structures with carbon fibre reinforced polymer (CFRP) laminates has been done in recent years. The interest in prestressing this material and the evaluation of the behaviour of the strengthened RC structures is the focus of this paper. A technique of strengthening RC slabs with prestressed CFRP laminates was tested on several Tcross-section large-scale RC beams. Comparisons are established between the reference RC beam and the strengthened beams with prestressed and non-prestressed CFRP laminates. To simulate the behaviour of the beams, a non-linear numerical model was used and validated by experimental results. This strengthening technique with prestressed CFRP laminates revealed a substantial improvement, both at serviceability and ultimate states, when compared with the reference beam and with the non-prestressed CFRP laminate strengthened beam.
Presented in this paper are results of an experimental investigation pertaining to the short-term behavior of concentrically loaded fiber-reinforced polymeric composite slender members. Tested members had box and I-shape cross sections and were pultruded using a vinylester matrix containing flame retardant additives reinforced with E-glass roving and nonwoven mats. Material properties for each tested member are used in a limit state predictor equation to correlate the experimental and the predicted results. Design guidelines and a step-by-step example are also presented.
A concise state-of-the-art survey of fiber-reinforced polymer (also known as fiber-reinforced plastic) composites for construction applications in civil engineering is presented. The paper is organized into separate sections on structural shapes, bridge decks, internal reinforcements, externally bonded reinforce ments, and standards and codes. Each section includes a historical review, the current state of the art, and future challenges.
The footbridge presented in this paper is located about 3 km from the city of Lleida, in Spain, and was built to cross an already existing roadway, a railway line and the new projected high-speed rail-way line between Madrid and Barcelona. The owners required a new pedestrian structure with minimum maintenance and which would be easy to erect. The footbridge was completed in October 2001. The proposed and accepted construction solution resulted in an innovative design using GFRP pultruded profiles which have no magnetic interaction with the electrified railway line, minimum maintenance costs and was easy to build. Thanks to its lightness, it took only 3 hours to complete the erection of the bridge to its final position.
As building history demonstrates, significant progress in the building domain has always been linked to the arrival of new building materials. This also seems to be true with the emergence of new composite fibre materials, which has made possible a new building method for the future. When considering past developments of now traditional materials, another one or two decades must pass until this new building method has matured.
Composite materials have been considered for use in structures in Europe for many years. The materials used for structures are all characterised by low creep, as would be expected when the structures must resist significant permanent loads. For most applications, the higher stiffness fibres, i.e. carbon, aramid, glass and polyester, are used. Unfortunately, the high strength comes at the expense of high cost, and mistakes have been made in attempting to find one-for-one substitutes for steel on a material-cost basis. The successful applications have all made use of other properties of the materials, not least of which are the light weight and consequent ease of handling.
In recent years there has been a marked increase in the use of fibre-reinforced polymers (FRP) as structural elements in bridge construction. This is due to the advantageous properties of these materials, such as low self-weight combined with high strength, the possibility of producing any shape, their high resistance to corrosion and fatigue, and easy maintenance. With this background the Swiss Federal Roads Authority commissioned the Composite Construction Laboratory (CCLab) of the Swiss Federal Institute of Technology in Lausanne, with the preparation of a state-of-the-art report on the use of fibre-reinforced polymers in bridge construction and also to elaborate recommendations for application and research. This paper summarises the report which comprises the development until the end of the year 2000.
The research undertaken during the last two decades has shown that one of the potential solutions to the steel-corrosion-related problems in concrete is the use of fiber-reinforced composite (FRP) reinforcement as a replacement for traditional steel bars. Glass FRP (GFRP) reinforcement is gaining more popularity in construction of bridges and in other concrete structures because of its low cost compared to Carbon FRP reinforcement. The durability of these materials, especially under severe environmental conditions, is now recognized as the most critical topic of research. The lack of data on durability of the GFRP reinforcements is a major obstacle to their acceptance on a broader scale in civil engineering.
This paper summarizes the most significant research work published on the durability of FRP bars in the past two decades. A comprehensive review of the literature on the durability of FRP bars indicates a significant increase in the number of studies in this area in the last decade. The durability tests conducted by the authors and others on the latest generation of GFRP bars subjected to stresses higher than the design limits, combined with aggressive mediums at elevated temperatures, have concluded that the strength reduction factors adopted by current codes and guidelines are conservative. These factors were based on limited test results that were carried out on the early generations of the GFRP products, which have now substantially changed.
Bridge decks made from fiber reinforced polymer (FRP) composites have been increasingly used in rehabilitation and new construction of pedestrian and highway bridges. For each application, connections are inevitable due to limitations on shape size and the requirements of transportation. Connections for FRP bridge decks include primary and secondary load-carrying joints and non-structural joints. Primary and secondary load-carrying connections are most concerned in construction, which include component–component connection, panel–panel connection, and deck-to-support connection. Unfortunately, the technical background, development and design guides of FRP bridge deck connections have not been documented adequately in literature. This paper attempts to provide technical background, developed joining techniques, and design principles concerning the joining of FRP decks. Design requirements, characteristics, performances, advantages and disadvantages of developed FRP deck connection techniques are discussed. Design principles for adhesively bonded joints and mechanical fixing and hybrid joints involving cutouts are also provided.
In order to study the viability of using GFRP pultruded profiles in floors of buildings, as structural elements, experimental investigations were carried out to analyse their behaviour when exposed to fire. In particular, the feasibility and efficacy of using different protective coatings/layers (an intumescent coating, a vermiculite/perlite cement based mortar and a calcium silicate board) to provide fire protection to GFRP pultruded profiles was investigated. Previous experiments showed that the above mentioned passive fire protection systems allow fulfilling fire resistance requirements for the envisaged application. This paper presents the results of the investigations concerning the fulfilment of the fire reaction requirements of those solutions. The experimental programme included dynamic mechanical analyses (DMA) and thermogravimetric and differential scanning calorimetry (TGA/DSC) experiments on both the GFRP and the fire protection materials. Subsequently, fire reaction tests were carried out on GFRP pultruded laminates, both unprotected and protected with the different fire protection systems, using a cone calorimeter. Results of these experiments allowed defining the field of application of each investigated solution, according to building code requirements.
This paper presents results of experimental investigations on the behaviour of GFRP pultruded profiles exposed to fire, in order to study the viability of their structural use in floors of buildings, taking into account the fulfilment of fire resistance requirements. The feasibility and efficacy of using three different protective coatings/layers, often used to protect structural steel, and a water cooling system to provide fire protection to GFRP pultruded profiles were investigated. The experimental programme included dynamic mechanical analyses (DMA), thermogravimetric and differential scanning calorimetry (TGA/DSC) experiments and fire resistance tests on GFRP tubular loaded beams. The unprotected GFRP beam failed after about 38 min, the three different passive protection systems provided a fire resistance between 65–76 min and the water cooling system provided a fire resistance of at least 120 min. Failure occurred in the upper part of the beams, due to compression and shear stresses. Results of these experiments allowed defining the field of application of each investigated solution, according to building code requirements.
The technologies for recycling thermoset composite materials are reviewed. Mechanical recycling techniques involve the use of grinding techniques to comminute the scrap material and produce recyclate products in different size ranges suitable for reuse as fillers or partial reinforcement in new composite material. Thermal recycling processes involve the use of heat to break the scrap composite down and a range of processes are described in which there are various degrees of energy and material recovery. The prospects for commercially successful composites recycling operations are considered and a new initiative within the European composites industry to stimulate recycling is described.
This paper is addressing the current waste management options for composite waste in the UK. It outlines legislation that is having an impact on the composites industry. Covers ways of managing waste from the composite industry through the waste hierarchy. Presents findings of projects examining the potential for using composite recyclate to make new useful construction products.
The introduction of polymers and advanced polymer composites in the civil infrastructure has been a very rapid process in comparison to other civil engineering materials when they were in their infancy. Advanced polymer composite materials have hitherto been utilised predominately in the aerospace and marine industries, but for the last three decades there has been a growing awareness amongst civil/structural engineers of the importance of the unique mechanical and in-service properties of these materials together with their customised fabrication technologies. These extraordinary properties have enabled the design engineers to have greater confidence in the materials’ potential and consequently to use them in the renewal of civil infrastructure ranging from the strengthening of reinforced concrete, steel and cast iron, and the seismic retrofitting of bridges and columns for the use in replacement bridge decks and in the new bridge and building structures. This paper will outline the developing stages of this exciting material and will indicate future prospects for it.
Durability of glass-fiber/polymer composites is dictated by the durability of the components: glass fiber, matrix, and the interface. Environmental attack by moisture, for example, can degrade the strength of the glass fiber; plasticize, swell, or microcrack the resin; and degrade the fiber/ matrix interface by either chemical or mechanical attack. The relative rates of these degradation processes are a function of the chemistry of the resin, temperature, length of time of exposure, degree of stress (whether cyclic or static), chemistry and morphology of coating of coupling agent on the glass fiber, and type of glass fiber. Several examples illustrate how the chemistry and morphology of the coatings of coupling agents that are on the glass fiber influence the strength and durability of the interfacial region.
In the summer of 2005, after eight years of use as a temporary bridge during the winter, the Pontresina Bridge for pedestrians was transported to the Swiss Federal Institute of Technology Lausanne for a detailed assessment of the structural safety, serviceability, and long-term durability of the bridge. The assessment included a visual inspection, quasistatic testing identical to that performed in 1997, and detailed investigations of material degradation. The visual inspection showed a variety of different local defects and damage such as local crushing caused by impact, local cracks due to inappropriate storage and lifting of the structure, fiber blooming, degradation of cut surfaces, and damage due to vandalism. Comparisons between load tests performed in 1997 and 2005 showed, however, that the structural safety and serviceability of the bridge have not been affected by these local damages. The stiffness of the pultruded shapes remained unchanged, whereas a slight decrease in strength between 13 and 18% was measured, which, however, is not critical when taking into consideration the high effective safety factors. In view of a further service period of 5 years until the next inspection, the visible damages were repaired. This experience showed that the durability is primarily affected by inappropriate constructive detailing and that pultruded glass fiber-reinforced polymer shapes, if correctly manufactured and processed, can offer good long- term performance and durability. © 2007 ASCE.
Fiber-reinforced synthetic polymers (FRP) are the building materials that may permit both the improvement of long-term building performance and the simplification of the construction process. Thanks to their high specific strength, low thermal conductivity, good environmental resistance, and their ability to be formed into complex shapes, FRP materials are well-suited to fulfilling many building functions. By integrating traditionally separate building systems and layers into single function-integrated components and industrially fabricating those components, the amount of on-site labor can be greatly reduced and overall quality can be improved. In order to profit from the advantageous qualities of FRP, however, it is essential to address the unique weaknesses and disadvantages of the material. Most notably, the problems of poor fire safety and high material costs must be overcome. In response to these challenges, a new multiple-story building system employing FRP materials is proposed. Within this system, fire safety is ensured through the use of an internal liquid cooling system, which circulates a cooling medium through the load-bearing FRP elements to maintain their temperature within a safe operating range. This system is made cost-effective through the integration of the building's heating and cooling system. By controlling the temperature of the circulating liquid, the building's structural elements can serve as heating or cooling emitters (radiators). Further, the addition of the liquid within the cells of the FRP elements helps maintain a more constant interior climate through the "thermal flywheel" effect, which improves energy efficiency and comfort. Experimental investigations were performed to explore the fire safety aspects of the proposed system. An existing FRP cellular bridge deck material was adapted to incorporate an internal liquid cooling system. After several preliminary investigations, large-scale experiments involving structural and fire loading were conducted on both liquid-cooled and non-liquid cooled specimens. The experiments demonstrated the efficacy of the system in protecting load-bearing FRP elements from the weakening effects of high temperatures, especially those that are stressed in compression. Structural fire endurance times were improved from less than one hour to more than two hours (EC1 Part 1.2) through the implementation of the liquid cooling system. Alongside the experimental program, a series of mathematical models were developed. Numerical thermochemical and thermomechanical models simulate the response of loaded liquid-cooled FRP panels in fire, while analytical models predict the post-fire mechanical behavior of fire-damaged sections. All models provide predictions that are within 10% of experimentally measured values. Glasfaserverstärkte Kunststoffe (GFK), als Baumaterialien eingesetzt, sind in der Lage sowohl die Bauwerksfunktionen dauerhaft zu verbessern als auch den Konstruktionsprozess zu vereinfachen. Dank ihrer hohen spezifischen Festigkeit, geringen Wärmeleitfähigkeit, guten Witterungsbetändigkeit und der Möglichkeit sie in zusammengesetzten Formen auszuführen, eignen sich GFK Materialien, vielfältige Bauwerksfunktionen zu übernehmen. Das Zusammenführen traditionell getrennter Bausysteme und Abschnitte zu funktionsintegrierten, industriell vorgefertigten Bauelementen veringerte die Arbeiten vor Ort erheblich und verbesserte die Qualität insgesamt. Um jedoch aus den vorteilhaften Eigenschaften des GFK Nutzen zu ziehen, ist es unerlässlich sich mit den einzelnen Schwächen und Nachteilen dieses Materials auseinanderzusetzen. Insbesondere die Probleme hinsichtlich des geringen Feuerwiderstands und der hohen Materialkosten müssen überwunden werden. Als Antwort auf diese Herausforderungen schlagen wir ein neues mehrstöckiges Bausystem aus GFK Materialien vor. Als Bestandteil dieses Systems sorgt ein internes Kühlsystem, welches eine Kühlflüssigkeit durch die lasttragenden GFK Elemente strömen läßt um die Temperaturen innerhalb eines sicheren Betriebsbereiches zu halten, für den notwendigen Feuerwiderstand. Durch die Einbindung des Heiz- und Kühlsystems in die Konstruktion kann das System wirtschaftlich hergestellt werden. Durch Temperaturänderung der Kühlflüssigkeit können die tragenden Bauteile zum Heizen bzw. Kühlen eingesetzt werden. Darüber hinaus hilft die Flüssigkeit in den Zellen der GFK Elemente, ein konstanteres inneres Raumklima durch den so genannten "thermal flywheel" Effekt aufrecht zu erhalten wodurch die Energie effizienter genutzt und die Behaglichkeit gesteigert wird. Um die einzelnen Aspekte des Feuerwiderstands zu erforschen wurden versuchsgestützte Untersuchungen durchgeführt. Zu diesem Zweck wurde ein bereits bestehendes zellenförmiges Brückendeckelement so umgebaut, dass ein internes Füssigkeitskühlsystem installiert werden konnte. Nach mehreren Voruntersuchungen wurde ein Großversuch unter jeweils flüssigkeitsgekühlten und trockenen Bedingungen durchgeführt, der sowohl statische als auch Brandlasten einschloss. Die Versuche zeigten die Wirksamkeit des Systems, lasttragende GFK Elemente vor dem sie schwächenden Einfluss hoher Temperaturen, besonders im Druckbereich, zu schützen. Die Feuerwiderstandszeiten des Tragwerks konnten so durch den Einsatz des Flüssigkeitskühlsystems von weniger als einer auf bis zu zwei Stunden erhöht werden (EC1, Teil 1.2). Neben dem Versuchsprogramm wurde eine Reihe mathematischer Modelle entwickelt. Numerische thermochemische und thermomechanische Modelle simulieren die Antwort belasteter flüssigkeitsgekühlter GFK Profile unter hohen Temperaturen während analytische Modelle das mechanische Verhalten abgebrannter Teilprofile abschätzen. Die Abweichungen der von den Modellen gelieferten Prognosen lagen innerhalb 10% der versuchstechnisch ermittelten Werte. Les matériaux composites en polymères renforcés par des fibres (FRP) permettent d'améliorer les performances à long terme des bâtiments et de simplifier le processus de fabrication. Grâce à leur haute résistance spécifique, faible conductivité thermique, bonne résistance aux actions environnementales et à leur capacité à être produits sous des formes complexes, les matériaux en FRP sont adaptés pour une utilisation multifonctionnelle dans le bâtiment. L'intégration de systèmes et de couches du bâtiment traditionnellement séparés en un composant unique à fonctions intégrées ainsi que la fabrication industriellement de ce composant, permet de réduire de manière considérable le temps de travail in-situ et d'améliorer la qualité de l'intégralité des travaux. Afin d'exploiter les nombreux avantages des matériaux en FRP, il est cependant essentiel d'adresser les faiblesses et les inconvénients propres au matériau. Notamment, les problèmes liés à la faible sécurité à l'incendie et le coût élevé du matériau doivent être surmontés. En réponse à ces défis, un nouveau système en FRP de bâtiment à plusieurs étages est proposé. Dans ce système, la sécurité au feu est assurée par l'utilisation d'un système de liquide de refroidissement interne qui circule par les éléments porteurs en FRP afin de maintenir leur température dans une plage de fonctionnement sûre. Ce système devient rentable en intégrant le système de chauffage et de refroidissement du bâtiment. En commandant la température du liquide de circulation, les éléments structuraux du bâtiment peuvent fonctionner en tant que chauffage ou émetteurs de refroidissement (radiateurs). De plus, la présence du liquide dans les cellules des éléments en FRP permet d'entretenir un climat intérieur plus constant par l'effet de "volant thermique", ce qui améliore l'efficacité énergétique et le confort. Des études expérimentales ont été conduites afin d'examiner le comportement au feu du système proposé. Un matériau cellulaire existant en FRP, utilisé pour les tabliers de pont, a été adapté afin d'y incorporer un système de liquide de refroidissement interne. Suite aux études préliminaires, des expériences structurales et d'incendie à grande échelle ont été conduites sur des éprouvettes sans et avec liquide de refroidissement. Les expériences ont démontré l'efficacité du système de protection des éléments porteurs en FRP sur leur dégradation sous hautes températures, particulièrement ceux sollicités en compression. Les durées caractérisant la résistance au feu exigée ont été améliorées en augmentant de moins d'une heure à plus de deux heures (EC1 partie 1.2) par l'introduction du système de liquide de refroidissement. Simultanément au programme expérimental, plusieurs modèles mathématiques ont été développés. Les modèles numériques thermochimiques et thermomécaniques permettent de simuler la réponse des panneaux en FRP réfrigérés par un liquide et chargés pendant l'incendie, alors que les modèles analytiques permettent de prévoir le comportement mécanique des sections brûlées après l'incendie. Les différents modèles fournissent des prévisions entre 10% des résultats expérimentaux.
MBrace Composite system for structures strengthening
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EN 13706: Reinforced plastics composites — Specifications for pultruded profiles. Part 1: Designation; Part 2: Methods of test and general requirements; Part 3: Specific requirements
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GFRP pultruded profiles in civil engineering: hybrid solutions, bonded connections and fire behaviour
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Mechanical characterization of recycled thermoplastic polymers for infrastructure applications
- P V Vijay
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- L Juvandes
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MBrace composite system
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Composite materials and discrete steel fibres for the strengthening of thin concrete structures
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