Dissertations / Theses on the topic 'FRP-confined concrete'

It is well recognized that the technique of strengthening reinforced concrete (RC) using fiber-reinforced polymer (FRP) jackets is more effective for circular sections, but less effective for rectangular sections. Indeed the presence of angular corners does not permit a uniform confinement to be provided by the FRP jackets to the columns. While rounded corners can enhance the effectiveness of FRP confinement, it will be more efficient to modify the rectangular section into an elliptical section. In addition to the better confinement effectiveness, from an aesthetical point of view, the shape modification would be a surprise to the built environment. This paper presents an experimental study on the behavior of FRP-confined concrete columns with elliptical section. Thirty-two short columns, divided in eight batches, were tested under axial compression. Each batch presents four specimens with different elliptical sections, determined by the aspect ratio a/b, that is the ratio between the minor and mayor axis. By varying this value from 1.0 to 2.0 (1.0, 1.3., 1.7, 2.0), the section becomes more and more elliptical starting from a circular shape. In this way it is possible to study the trend of effectiveness of FRP confinement for different section geometries. It is also interesting to study how the confinement effectiveness may vary by changing the cylinder strength of concrete and the number of the layers of CFRP. For this reason, a cylinder strength of concrete of 25 and 45 MPa have been used for the present research work, and half of the specimens were wrapped by one layer of CFRP, while the remaining specimens were wrapped with two layers. A simple analysis of the results has been carried out for evaluating the experimental work described in the present document. Further studies and analysis on this work should help to achieve a new and more accurate stress-strain model for CFRP-confined concrete columns with an elliptical section.

In recent earthquakes, structures have not performed as well as expected resulting in a need for better means of retrofitting and improvements in seismic design. Fiber Reinforced Polymers (FRP), as a material with potential to increase strength and ductility of columns in conjunction with capacity design methodology, has promise for seismic design. By investigating the displacement, ductility, and flexural strength properties of FRP confined reinforced concrete circular cross sections, this study analyzes the seismic applications of FRP confinement. The study is performed by incorporating an FRP confined concrete stress-strain model into a developed Moment-Curvature and PM Interaction software. This software conducts a comparison between traditional steel and FRP confined sections while performing parameter studies on the 28-day unconfined concrete compressive strength, longitudinal reinforcing ratio, cross section diameter, FRP confinement jacket thickness-cross section diameter ratio, and FRP confinement system design variables. These studies validate FRP’s performance for seismic applications resulting in several design recommendations to increase displacement capacity, ductility, and flexural strength and, thus, seismic performance.

Thesis (Ph. D.)--University of Missouri--Rolla, 2007.
Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed February 12, 2008) Includes bibliographical references.

The steel-concrete bond and the cracking behaviour of concrete affect the performance of reinforced concrete structures. This is due to the fact that the transfer of forces between the steel and the concrete are accomplished through the bond. The bond between the steel and the concrete is affected by many factors such as corrosion of reinforcement, type of applied loading, and the confinement level. Reinforcement corrosion is one of the primary causes of the loss of steel-concrete bond. On the other hand, an accumulation of bond damage occurs due to the application of fatigue cyclic loading, as in the case of bridges and marine structures. It is known that fibre reinforced polymer (FRP) confinement improves the bond strength, even in the case of corroded reinforcing steel bars. The objective of this thesis was to develop an analytical tool for structural engineers to evaluate the corroded steel-FRP confined concrete bond under fatigue cyclic loading. Two models have been developed; 1) slip-fatigue model; and 2) bond stress-slip model. These models considered the effect of corrosion of reinforcement, the external confinement provided by the FRP sheets, and the fatigue cyclic loading. Slip after ‘N’ number of cycles for unwrapped and FRP wrapped cases were developed as a function of the initial slip, the final slip, and the fatigue bond life. These models were capable of capturing the experimental behaviour reported in the literature. Slip-life models for unwrapped and FRP wrapped beam specimens were developed using non linear regression analysis. Harajli et al. (2004) static bond stress-slip law was modified in order to model the bond stress-slip behaviour for the unwrapped and FRP wrapped beam specimen under monotonic and cyclic loading. The proposed cyclic bond stress-slip behaviour followed the monotonic bond stress-slip envelope and satisfactorily modeled the experimental behaviour. From the principles of statics of bond and using the derived cyclic bond stress-slip envelope, an equation to calculate the required development length of steel reinforcement was derived. The proposed equation is dependent on the material and the geometrical properties of a structural member. The derived equation was able to satisfactory predict the fatigue bond life.

An investigation into the achievable gain in axial strength capacity of FRP-confined prismatic reinforced concrete columns compared to unconfined columns when subject to axial and axial-flexural loading has been performed. An experimental test matrix of small-, medium-, and large-scale specimens addressed; size effect, load eccentricity and cross-sectional aspect ratio, allowing for detailed study of the cross-sectional behavioural mechanics and generation of an analytical model capturing the evolution of the cross-sectional behaviour. Experimental results demonstrated that an increase in axial capacity of 48% was achievable in axially loaded specimens, but was limited by cross-sectional geometry, and inevitable second order effects, that were more extensive with increasing load eccentricity. There was a corresponding reduction in confinement effectiveness, thus more FRP plies or straps are required when subject to large bending. Furthermore, with increasing load eccentricity, there is a beneficial increase in lateral deformation capacity. All specimens of rectangular cross-section benefit from FRP-confinement but this decreases with increasing aspect ratio. Lastly, experimental testing highlighted the importance of debonding, as the side length of the specimen between corners increases, small areas to the whole side of the specimen detached. Confinement of prismatic columns is achieved using the resistance generated in the FRP jacket as the concrete laterally expands, generating confining stresses at the convex corners under axial loading. Analysis of FRP strains at mid-height of the specimen show the formation of a cruciform shape originating at the corners, along the diagonals of the cross-section. As eccentric load is applied, the strains evolve into the higher compressive region, moving the effectively confined area over into this compressive region. Variation of the cross-sectional aspect ratio also dictates a change in effectively confined area, with higher strains generated next to the shorter side lengths. This complex behaviour necessitates research into large-scale specimens as the size effect does not encourage scaling of results from small-scale testing.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2006.
Includes bibliographical references (p. 197-205).
Increase in the use of fiber-reinforced polymer (FRP) composite materials for strengthening and retrofitting of concrete columns and bridge piers has urged the development of' an effective non-destructive evaluation (NDE) methodology. Radar technologies have shown great potential for assessing the structural and material integrity of FRP-confined concrete systems. In developing such technology, an interdisciplinary approach must be pursued by integrating contributions of various engineering fields. Under this framework, this thesis aims at establishing fundamental knowledge in two particular research areas: the mechanics and damage behavior of FRP-confined concrete and the characterization of electromagnetic (EM) properties for concrete and FRP materials. Research on mechanics and damage behavior of FRP-confined concrete involved a thorough literature survey on the state-of-the-art understanding of the subject and the execution of an experimental program for load-deformation characterization of FRP-confined concrete cylindrical specimens subjected to monotonic axial compressive loads. Based on the experimental results and comparative studies with recent analytical models, the experimental program was extended to the characterization of specific damage levels using a volumetric deformation metric. Visual inspection of the concrete core of specimens previously loaded to levels close to ultimate failure revealed the existence of significant residual volumetric strains, which upon the removal of the FRP jacket could provoke severe concrete cracking and catastrophic failure.
(cont.) Research on dielectric property characterization of concrete and FRP materials led to the development of an integrated methodology for estimating the complex permittivity of low-loss materials in general using free-space measurements of EM wave transmission. Such development required theoretical modeling of EM wave propagation through dielectric media and experimental measurements of transmission coefficients. Validation studies were performed using Teflon, Lexan, and Bakelite materials whose dielectric properties are established in literature. The methodology was then applied to concrete and FRP materials. Establishing minimum criteria for specimen dimensions and optimal frequency bandwidths is still required before the proposed methodology can be used in field applications. Additionally, exploratory research on the assessment of FRP-confined concrete using radar technologies was conducted. Preliminary results indicate potential of such technologies for detecting features related to the presence of rebar, air cavities, delaminations, and mechanical damage in FRP-confined concrete columns.
by José Alberto Ortega.
S.M.

Strengthening of reinforced columns confining by modern composite materials is effective method, allows quickly realized strengthening, without increase dimension of strengthening columns. Just like using reinforcing bars, is the mainly assumption for this method the multi-axis state tension and deducing confining pressure, which will increase strength of concrete. Improved of properties of confining concrete can be determined by using relationships, but there are considerably differences. This diploma theses, dealing with strengthening of circular reinforced columns confinement by external FRP fabric, compared approaches to design of reinforced concrete by confining and using the results of an analytical and numerical study to describe problem of confining concrete and compare factors influencing the final properties of the wrapped concrete.

Les techniques de renforcement de structures en béton armé (BA) par collage de polymères renforcés de fibres (PRF) trouvent un important champ d'applications dans le renforcement des poteaux en BA. Le chemisage par PRF confine le noyau du poteau et permet d'augmenter sa résistance et sa ductilité. Bien que de nombreux travaux expérimentaux aient été consacrés à l'étude de l'effet de confinement du PRF sur le comportement des poteaux en BA, la réalisation d'une simulation réaliste de la réponse structurelle de tels éléments présente de nombreuses difficultés liées aux modèles de comportement peu appropriés à reproduire précisément la réponse mécanique du béton confiné. Dans cette recherche, un modèle de comportement élasto-plastique endommageable est développé pour reproduire la réponse mécanique du béton sollicité suivant un chemin triaxial de contraintes. Ce modèle prend en compte différents mécanismes de comportement du béton tels que les déformations irréversibles, l'endommagement dû à la microfissuration, la sensibilité au confinement et les caractéristiques de dilatation. Un processus d'identification des paramètres du modèle est proposé sur la base d'essais classiques. La validation de ce modèle est ensuite démontrée en comparant des résultats de simulations à des données expérimentales de la littérature sur des bétons confinés activement puis des bétons confinés par des PRF présentant une large gamme de rigidité. Le modèle proposé est également comparé à différentes modélisations de la littérature. Les capacités du modèle sont illustrées et analysées sur des applications tridimensionnelles de poteaux en BA de taille réelle, non confinés et confinés par PRF
For the past two decades, externally bonded Fiber Reinforced Polymers (FRP) has gained much popularity for seismic rehabilitation of reinforced concrete (RC) columns. In this technique, FRP wrap installed on the surface of a column acts as lateral confinement and enhance the strength and deformation capacity of the concrete element. Although many experimental works have been devoted to the study of confining effect of FRP on the behavior of RC columns, the numerical simulation of FRP-jacketed RC columns remains a challenging issue due to the lack of appropriate constitutive model for confined concrete. In this study, a damage plastic model is developed to predict the behavior of concrete under triaxial stress states. The proposed model takes into account different material behavior such as irreversible strain, damage due to microcracking, confinement sensitivity and dilation characteristic. A straightforward identification process of all model’s parameters is then presented. The identification process is applied to different normal strength concrete. The validity of the model is then demonstrated through confrontation of experimental data with simulations considering active confined concrete and FRP confined concrete with a wide range of confinement stiffness. The proposed constitutive model is also compared with other models from the literature and the distinguishing features of this new model are discussed. Furthermore, the capacity of the model in the three-dimensional finite element analysis of full-scale RC columns is demonstrate and discussed

碩士
國立中央大學
土木工程研究所
97
What we called “Fiber Reinforced Polymer Bars” is made from carbon or glass fibers mixed with polymer resin to a shape similar to steel reinforcing bars, initial as FRP bars. Nowadays, FRP bars are widely adopted in newly constructed RC structures in many countries. With respect to the highly corrosive environment as Taiwan, FRP bars as reinforcement can be considered to the new or green RC structures for sustaining their service lives. ACI committee 440 has published a new design guideline for FRP concrete members in 2006. However, the content is limited to the specifications on how to design FRP RC beams, such as moment, shear, and bond strength designs. There is no other design guide for RC columns, especially for the confined effectiveness of FRP hoops. Therefore, the research is to investigate the confining effectiveness of RC columns using FRP hoops. Ten short column specimens with rectangular section were manufactured from a local FRP industrial firm. The FRP tie bars are used as the transverse reinforcement instead of steel tie bars to confine the column. The FRP longitudinal reinforcement in some concrete columns is used. The columns were subjected to monotonically axial loading. Deformations of concrete, rebars and tie bars were measured electronically. Main results showed that the compressively carried capacity of FRP rebars cannot be ignored. The GFRP tie bars performed better behavior of confinement than the CFRP tie bars.

External confinement of concrete columns with fibre-reinforced polymer (FRP) sheets has been shown to lead to significant improvements on the axial compressive behaviour of these columns. This application of FRP composites is effective as a confinement material for concrete, in both the seismic retrofit of existing reinforced concrete columns and in the construction of concrete-filled FRP tubes (CFFTs) as earthquake-resistant columns in new construction. However, experimental studies on the axial compressive behaviour of FRP-confined concrete columns manufactured with high strength concrete (HSC) remain very limited. This thesis presents the results from a Ph.D. study at the University of Adelaide that was aimed at undertaking a comprehensive review on the axial compressive behaviour of monotonically-loaded circular FRP-confined HSC columns. The 10 journal articles developed as part of this thesis present the findings from experimental tests on a total of 282 FRP-concrete composite specimens. The effects of amount of confinement, concrete strength, confinement method, specimen size, fibre type, manufacturing method, fibre orientation, specimen end condition, specimen slenderness, concrete shrinkage, strain measurement method, FRP overlap and lateral prestress were investigated. The test specimens were manufactured with aramid FRP (AFRP), carbon FRP (CFRP) or high-modulus CFRP (HMCFRP) and their unconfined concrete strengths ranged from 34.0 to 119.3 MPa. Specimens were manufactured as either FRP-wrapped or concrete-filled FRP tubes (CFFTs), with all specimens cylindrical in shape and the majority 152 mm in diameter and 305 mm in height. The large quantity of the results presented in this thesis allows for a number of significant conclusions to be drawn. The experimental results presented in this thesis provide a performance comparison between FRP-confined normal-strength concrete (NSC) and the experimentally limited area of FRP-confined HSC. The results from this thesis indicate that, above a certain confinement threshold, FRP-confined HSC columns exhibit highly ductile behaviour. However, for the same normalised confinement pressures, axial performance of FRP-confined concrete reduces as concrete strength increases. The results also indicate that the behaviour of FRP-confined concrete is significantly influenced by the manufacturing method, with specimens manufactured through an automated filament winding technique exhibiting improved compressive behaviour over companion specimens manufactured through a manual wet layup technique. In addition to this, the influence of fibre type was examined with an improvement in compressive behaviour linked to an increase in fibre rupture strain. Further experimental testing on the influence of specimen size, confinement method and end condition found these parameters to have negligible effect for the range of parameters tested in this study. Experimental testing on specimens with inclined fibres revealed specimen performance is optimised when fibres are aligned in the hoop direction and the performance diminishes with decreasing fibre angle with respect to the longitudinal axis. The influence of height-to-diameter ratio (H/D) on axial compressive behaviour revealed specimens with H/D of 1 outperform companion specimens with a H/D ratio of 2 to 5, with significantly increased strength and strain enhancements. The influence of slenderness on specimens with a H/D ratio between 2 and 5 was found to be significant in regards to axial strain enhancement, with a decrease observed as specimen slenderness increased. Conversely, the influence of slenderness on axial strength enhancement was found to be negligible. The strain results indicate that hoop rupture strains along the height of FRP-confined concrete become more uniform for specimens with higher amounts of confinement. On the other hand, the variation of hoop strains around the perimeter was not observed to be significantly influenced by slenderness, concrete strength or amount of confinement. An examination on the effect of FRP overlap length revealed no significant influence exists for the amount of overlap length on strain enhancement ratio. On the other hand, an increase in overlap length leads to a slight increase in strength enhancement, with these observations equally applicable to both continuously and discontinuously wrapped specimens. The results also indicate that continuity of the FRP sheet in the overlap region has some influence on the effectiveness of FRP confinement. Furthermore, it was observed that the distribution of FRP overlap regions for discontinuously wrapped specimens can influence the axial compressive behaviour of these specimens in certain overlap configurations. Finally, it is found that the distribution of lateral confining pressure around specimen perimeter becomes less uniform for specimens with higher concrete strengths and those manufactured with overlap regions that are not evenly distributed. The results from experimental testing of specimens with FRP-to-interface gap revealed that the influence of gap on axial strain enhancement is significant, with an increase observed as the gap increased. Conversely, the influence of interface gap on axial strength enhancement is found to be small with a slight reduction observed with increased gap. The results also indicate that an increase in gap causes an increase in strength loss during the transition region of the stress-strain curve, as a result of the delayed activation of the FRP shell. The results from experimental study on FRP-confined concrete with lateral prestressing indicates that the influence of prestress on compressive strength is significant, with an increase in ultimate strength observed in all prestressed specimens compared to that of non-prestressed specimens. On the other hand, the influence of prestress on axial strain was found to be dependent on the amount of confinement, with lightly-confined and well-confined prestressed specimens displaying a decrease and increase in ultimate strain, respectively, compared to their non-prestressed counterparts. The results also indicate that prestressing the FRP shell prevents the sudden drop in strength, typically observed in FRP-confined HSC specimens, that initiates at the transition point that connects the first and second branches of the stress-strain curves. Finally, it was observed that prestressing the FRP tube results in a significant increase in the specimen toughness as well as in the hoop strain efficiency of the FRP shell. In addition to the summarised experimental findings, an analysis of the experimental databases for specimens manufactured with an interface gap and lateral prestress led to the development of a lateral strain-to-axial strain model. A comparison of the proposed model with the experimental results of specimens prepared with an interface gap or prestressed FRP tubes showed good agreement.
Thesis (Ph.D.) (Research by Publication) -- University of Adelaide, School of Civil, Environmental and Mining Engineering, 2015.

碩士
逢甲大學
土木及水利工程所
91
ABSTRACT Strengthening of reinforced concrete structures with external bonded carbon fiber reinforced plastics (CFRP) comes into notice recently. In this paper, a series of experimental investigations are conducted to study the behavior of fire-damaged concrete cylindrical specimens confined by carbon fiber. In order to study the performance enhancement of concrete confined by carbon fiber composite , a total 130 concrete cylindrical specimens with different strength were confined by different layers of carbon fiber cloth. Some of them were heated in the furnance to model concrete exposed to different fire-damaged environment. All specimens were tested under uni-axial compresson test to examine the effects of various conditions. The study indicates that CFRP confinement can significantly increase both strength and ductility of concrete, whether under high temperature environments or not. Based on the experimental data, analytical models are presented to predict compressive strength, strain corresponding to compressive strength, and stress-strain relation of concrete confined by CFRP. Keywords : fire-damaged ; carbon fiber composites ; compressive strength ; stress-strain relation

碩士
國立臺灣大學
工程科學與海洋工程學系
92
ABSTRACT The purpose of this thesis is to understand the following mechanical properties by Finite Element Analysis method：stress-strain relationships, elements stresses distribution fields and effects of designing parameters (fiber-wrapped layers, corner radius) in static axial loading test. However, physic, failure and 「fiber-concrete」 coupling behavior can be observed by experiment, which helps us checking the exactness and reality of numerical modeling. Refer to experiment, changing confinement layers and corner radius in fixed profile geometry of confined square concrete columns shows that not only non-uniform lateral confining pressures and axial stress concentration phenomenon have been happened, but there is also a high decay occurred in stress descending portion after specimen failure. When increasing confinement layers and corner radius, axial stress will be promoted and lowered the trend of stress decay in confined specimens. Therefore, we learn that retrofitting advantages of square concrete columns are depended on these above two designing parameters. For the numerical analyses, there are good simulation results with experimental data in stress-strain compatibility. The error variations are under 10 percent. Moreover, contour of axial stress distribution on concrete model is almost the same as the references suggested in the past and stress concentration phenomenon is clearly softened on four corners, but lateral confining effect is improved quickly after increasing confinement layers and corner radius. In addition, uplift trends of stress-strain curves and excellent retrofitting advantages of square concrete columns can be induced by increasing corner radius.

碩士
逢甲大學
土木及水利工程所
90
In this research, a series of experimental investigations are conducted to study the behavior of fire-damaged tied concrete cylindrical specimens confined by fiber reinforced plastic（FRP）. The dimension of tested specimen is 12cm in diameter and 24cm in height. A total of 264 cylindrical concrete specimens are made with 4 kinds of design strength and 5 tied spacing. Two types of FRP confinement and 6 sets of temperatures are considered. The purposes of tests are to investigate confined effects of spiral reinforcements and carbon fiber composites on fire-damaged concrete. The results show that either for plain concrete or spirally reinforced concrete, the strength reduction and the strain increment in concrete increases with the increase of the fire-damaged temperature. Furthermore, the fire-damaged effects in high strength concrete are more obvious than those in low strength concrete. Whether the specimens suffer the fire-damage or not, the confined effects are always better in low strength concrete, either with spiral reinforcement or FRP confinement. In addition, under room temperature the compressive strength of the concrete with large spacing of lateral reinforcement is lower than that of the plain concrete but the peak strain is still increased；Nevertheless, under high temperatures the strength is lower in plain concrete. The FRP confined effects of plain or spirally reinforced concrete are better with the increasing of fire-damaged temperature, regardless of the concrete strength or spiral spacing. Based on the experimental data, analytical models are presented to predict compressive strength, strain corresponding to compressive strength and stress-strain relationship of fire-damaged concrete with confinements.

碩士
國立屏東科技大學
土木工程系碩士班
89
Recently, fiber reinforced plate (FRP) composite wrap has been used as an effective method for the strengthening and rehabilitation of concrete structures. The models for transverse steel reinforcement are used in most work. But, the mechanical behavior is different between FRP confined and steel confined concrete column. Present paper discusses the mechanical behavior of the FRP confined concrete column by using the endrochronic plastic theory. Present model is base on the endrochronic model for concrete by Lu and Wu. The deviatoric hardening function has been modified. The strain increment transformation rate is defined. The present model is used to describe the mechanical behaviors of the FRP confined concrete column. The composite materials investigated include GFRP and CFRP. Also, several different conditions of confinement are discussed. The theoretical results are compared with experimental data. The results are satisfactory.

碩士
國立屏東科技大學
土木工程系碩士班
90
Present paper discusses the mechanical behavior of the FRP confined concrete column. The model of Lu and Chen is used in this paper. The behavior of lateral strain is discussed by modifying the strain increment transformation rate. Also the ultimate strength functions are defined. The FRP confined concrete column discussed includes GFRP confined concrete column and CFRP confined concrete column. Different conditions of confinement are considered in this paper. The theoretical results are compared with experimental data. The results are satisfied.

碩士
國立臺北科技大學
土木與防災研究所
96
In the techniques of structural retrofitting, FRP jacket using epoxy as the cohesive material is quite popular. Epoxy has good cohesive property, and displays pretty good strengthening effect under room temperature. However, its cohesion may gradually reduce while the temperature arising, and sequentially lose the strengthening effect. Furthermore, the structural elements even may burst during high temperature state due to the surface is sealed. In the preceding researches, a newly developed material, namely geopolymer, was used to replace epoxy as the cohesive material. Preliminary result indicated that the effect of confinement indeed exists, and the property of temperature resistance is better than that of using epoxy. In the present research that the FRP confined concrete cylinders are prepared to investigate the confined effect under different temperature, as well as the size effect. In this study, the experimental parameters includes strength of concrete, specimen, covered layers, fiber used and heat temperature. The results indicate that the effectiveness of confinement is considerably retained under high temperature. Moreover, since geopolymer is a porous material so that the vapor pressure from the moisture of the specimens produced by high temperature may be released, and then reduce the possibility of bursting.

An extensive amount of research has been reported in previous literature on the behaviour of FRP-confined concrete subjected to concentric axial compression. However, data on the behaviour of high strength concrete confined with various types and configurations of FRP systems is still lacking and no consensus exists on the complete response of FRP-confined concrete. In addition, no appropriate design guidelines are currently available. This thesis reports results from an experimental program involving 112 cylindrical concrete specimens, 88 of which were FRP-wrapped and the remaining 24 were control specimens. All the specimens were 152 mm in diameter and 305 mm in length. Test variables included: amount of FRP materials used, strength and stiffness of FRP materials, concrete strength, and the health of concrete at the time of strengthening. Experimental results indicated that a pre-repair load of up to 77% of the unconfined concrete strength had no appreciable effect on the stress-strain response of FRP-confined concrete. With an increase of the unconfined concrete strength, the strength enhancement, energy absorption capacity, ductility factor and work (energy) index at rupture of FRP jackets all decreased remarkably. A positive correlation was found between confined concrete ductility and FRP rupture strain. In addition, a gradual post-peak failure of the specimens, observed previously from FRP-confined concrete columns tested at the University of Toronto, was also observed in some of the current tests -- owing to the high speed data acquisition system. That ductile failure can be attributed to the gradual unzipping failure of FRP jacket, which in turn is related to specimen size. A new constitutive model was developed based on material properties, force equilibrium and strain compatibility. The size effect was taken into account in the model, which is able to accommodate concrete with a wide range of strength (25 MPa to 110 MPa) confined with various types and configurations FRP systems. Design equations from CSA S806-02 and CSA S6-06 provide reasonable and conservative estimates for the FRP-confined concrete strength. To calculate the peak strain for FRP-confined concrete, an equation based on the work by Berthet et al. (2006) is proposed.

碩士
國立臺北科技大學
土木與防災研究所
98
In practical, the bond material used in the FRP jacketing strengthened methods is mainly epoxy. Earlier researches indicated that the effect of confined strengthening at room temperature is indeed reliable. However, it would reduce tremendously while reaches a higher temperature. Previous studies have used geopolymer to replace epoxy as the bond material for sticking FRP onto concrete cylinders, both the effects of strengthening as well as the advantage of better heat resistance were classified. Additional studies have used a porous “geopolymer foam” as the fire resistant coating to cover the concrete cylinders jacket strengthened by FRP using geopolymer, the effect of fire-resistant insulation was considerably shown. The present study attempted to develop a light weight material with better performance in fire resistance and insulation. Perlite powder was added into geopolymer mortar, and made use as the fire resistant coating with different thickness to cover the concrete cylinders jacket strengthened by CFRP using epoxy as the bond material. The experiment results revealed that the perlite geopolymer coating did display effect in heat resistance. The heat insulation effect for 2.5 cm thickness coating was around 100 ℃, while the 4.5 cm thickness perlite geopolymer coating was 150 ℃.

碩士
國立臺北科技大學
土木與防災研究所
97
FRP jacket using epoxy as the cohesive material on structural confinement is very popular nowadays. Epoxy has good strengthening effect under temperature, but would lose the strengthening effect substantially while the temperature is arising. The preceding researches showed that the effect of confinement indeed exists on concrete cylinders covered by FRP using geopolymer, and the property of temperature resistance is better than that of using epoxy. In the present study, concrete cylinders covered by FRP with geopolymer foam are prepared in order to improve the fire resistance. Moreover, using geopolymer foam as the structural element, the problems of static load and high cost is expected to solved. The experimental parameters include strength of concrete, specimen, covered layers, fiber used, and temperature. The results indicate that the effectiveness of heat resistance and confinement are considerably for concrete cylinders confined by FRP with geopolymer foam.

碩士
逢甲大學
土木工程所
99
A series of experimental investigations were conducted to study the behaviors of fireproof material bonded CFRP (Carbon Fiber Reinforced Polymer) confining concretes exposed to fire. First, a total of 131 concrete cylindrical specimens, with size of Φ12cm×24cm and Φ15cm×30cm, were designed and cast. These concrete cylindrical specimens were pre-loaded and confined by CFRP. Some of these specimens were externally adhered by fireproof material with different thicknesses. Next, all the specimens were exposed to different fire temperatures (300, 400, 500, 600 and 700℃) with 30 or 60 minutes exposure time. All the specimens were then loaded by the loading test. The residual compressive strengths of concrete specimens were evaluated to see the fire resistance effects of fireproof material. The results show the confining effect of CFRP begins to lose gradually when the temperature is over 300℃. With the increase of temperature or exposure time, the effectiveness of CFRP is decreased and the strengths of confining concretes are also decreased. However, the fireproof material can really protect CFRP confining concretes from high temperatures and concrete specimens can still retain most of the original strengths. The fire resistance effect depends on the thicknesses of fireproof material and the fire environments. The fireproof material with 8 mm in thickness can protect CFRP confining concretes for the temperatures below 600℃. The fireproof material with 12 mm in thickness can protect specimens even when the temperatures are over 600℃. Besides, the strength of specimen with non-fireproof material at 300℃ and that with fireproof material at 700℃ are very close, which means the fireproof material can reduce the fire temperature around 300℃~400℃. It is also found that the residual strengths of fireproof specimens exposed at temperatures around 500℃~600℃ are slightly increased. The causes of this phenomenon are due to the water evaporating and the rehydration of concrete specimens. Based on the experimental data, analytical models are presented to predict compressive strength of FRP confined specimens with/without fireproof material.

碩士
逢甲大學
土木工程學系
102
Abstract This study investigates the loading behavior of carbon fiber reinforced plastics (CFRP) strengthening concrete specimens with different fire resistive coatings under high temperatures. The experimental analyses are divided into two parts, the first part is to continuously discuss the behavior of concrete cylindrical specimens confined by CFRP with different fire resistive coatings and exposed to fire environments, while the other part is to discuss the behavior of reinforced concrete beams confined by CFRP with fire resistive material and exposed to fire environments. There are a total of 24 concrete cylindrical specimens with dimensions of Ø12cm×24cm and 18 reinforced concrete beam specimens with dimensions of 17cm×22cm×120cm, all with concrete design strength of 280kg/cm2. All the concrete specimens are reinforced with CFRP and then fire resistive coatings of different kinds and thicknesses are applied to the specimens. Then, the fire exposure experiments with different temperatures (500oC, 600oC) and durations 30 minutes are conducted. The concrete cylindrical specimens then go through a compression test and reinforced concrete beam specimens are under the four-point bending test to observe the load bearing behavior of the specimen and fire protection effectiveness of the specimen by fire resistive coating. The results show that GREENPOWER and fire resistive material can protect concrete specimens and the strengths/loadings of concrete specimens reinforced by CFRP will not be obviously decreased under high temperatures. However, the strengthening effectiveness of CFRP will be reduced along with the increase of fire temperature even with fire resistive material protection. Besides, the increase in thickness of GREENPOWER and fire resistive material will have better fire protection to concrete specimens.

碩士
國立臺灣大學
土木工程學研究所
104
This study is conducted to investigate the shear strength of FRP-Wrapped Spiral Corrugated Tube (FWSCT) confined circular concrete columns. In order to study the shear strength of the Spiral Corrugated Tube and the FRP jacket, two shear strength models (UCSD shear model and residual shear model) are adopted in this analytical procedure. In this experimental program, two FRP-Wrapped Spiral Corrugated Tube (FWSCT) Circular Concrete Columns with different amount of FRP confinement were tested under cyclic lateral loading with a constant axial load level. The main variable was the confinement ratio of the FRP jacket, which can be controlled by wrapping different number of FRP sheets around the Spiral Corrugated Tube. Two columns, FWSCT-1 and FWSCT-3 were designed based on a reference column, FWSCT-0 (Wu 2015), which confined by only a spiral corrugated tube with 0.4 mm thick and 1940 mm tube length. FWSCT-1 and FWSCT-3 were wrapped by additional one-layer and three-layer of Glass Fiber-Reinforced Polymer (GFRP) jackets around a spiral corrugated tube, respectively. Test results showed that the brittle shear failure in specimen FWSCT-0 is improved by wrapping one-layer of the GFRP jacket as seen in the test of specimen FWSCT-1. Specimen FWSCT-1 failed at 4% story drift, resulting in flexural-shear failure of column, while specimen FWSCT-3 failed at 7% story drift, resulting in flexural failure of longitudinal bars.

Fibre-reinforced polymer (FRP)-confined high strength concrete (HSC) as a structural system, has received significant attention recently due to higher engineering profits compared to normal strength concrete (NSC). To use widely any new construction material or structural element in the construction industry, its mechanical behavior under different loading type should be accurately determined. Although numerous research was performed to predict the mechanical behavior of FRP-confined concrete, most of the models had a poor prediction for the ultimate axial strain which is a key reference parameter in designing procedure. This inaccuracy can be dependent or on experimental data which were used to develop/validate models, either on the understanding of mechanical response of FRP-confined concrete. Examination of existing experimental data needed for developing or validating a model in this study shows that the type of measurement method is one important factor affecting the obtained experimental axial stress-strain curve for FRP-confined HSC specimens. This indicates that a better measurement method should be used to obtain both local and overall deformation of specimens during the test procedure. Investigation on the performance of existing models showed that compressive strength of concrete and hoop rupture strain are two influential parameters in existing models which govern the accuracy of models compared to other parameters. However, hoop rupture strain had a large variability of recorded data in existing experiments, partly due to the use of contact measurement methods, i.e. strain gauges that measure local lateral deformation. In addition, this variability can be dependent on the understanding of mechanical behavior, confinement mechanism and localization characteristics of FRP-confined concrete. The confinement mechanism was examined in this study by investigation of FRP-confined HSC behavior under concentric and eccentric loading condition. A total of 31 specimens with circular and square cross-section were tested under different eccentricity ranging between 0 to 50 mm. The outcome showed that the load-displacement-curves are influenced significantly by eccentricity. The results also illustrated that the ultimate axial stress decreased by increasing eccentricity opposite to ultimate axial strain. The results also indicate the influence of eccentricity on the confinement mechanism. The mechanical behavior and localised failure of unconfined and FRP-confined concrete circular specimens for three structural systems, i.e. plain, ultra-high-strength steel and polyvinyl alcohol fibre-reinforced concrete-filled FRP tubes (CFFT), was investigated using Digital Image Correlation (DIC). A new approach also was developed to correlate the mechanical behavior of FRP-confined concrete with its localization characteristics. This approach is able to determine the onset of localization accurately and quantify the localization evolution. Furthermore, probability density function (PDF) was used in this approach to correlate localization characteristics to the mechanical response of FRP-confined concrete. The localization onset of FRP-confined NSC specimens was found to be earlier than in FRP-confined HSC specimens. Furthermore, the outcome indicated the existence of two types of localization evolution in tested specimens. The results showed that the unconfined and insufficiently confined specimens showed abrupt expansion of shear zone opposite to well-confined specimens by more gradual expansion. The results also indicated that the mechanical behavior of FRP-confined HSC is governed by naturally brittle behavior of HSC and the distribution of strain over specimens’ surface had similar behavior to probability density function. The analysis and quantification of strain evolution showed that Beta PDF function can be used to capture the distribution and evolution of Von Mises strain over specimens’ surface and to correlate localization characteristics to mechanical response of specimens under compression. The intrinsically brittle behavior of HSC influences negatively the mechanical performance of unconfined HSC and FRP-confined HSC. An abrupt behavior in the evolution of localization of HSC specimens and FRP-confined HSC compared to NSC was observed in this study, although FRP jackets limited this brittle behavior. In previous reports it has been found that adding fibers such as steel in concrete wet mix improves the performance of HSC and shows more ductile behavior compared to plain HSC. In this study, ultra-high-strength steel and polyvinyl alcohol fibers were used to improve brittle behavior of FRP-confined HSC. The results showed that these fibers improve the ductility of this structural element by disappearance of temporary lose of strength after transition zone in axial stress-strain curve and higher obtained ultimate axial strain. However, it was observed that ultimate axial stress had a marginal increase by adding used fibers in wet mix of concrete at same normalized lateral stiffness. Additionally, as shown in this study, the lateral behavior of these systems was not altered significantly by adding fibers and approximately similar lateral trend as FRP-confined plain concrete can be obtained. Although the more homogenous crack distribution and localization evolution were observed in these structural elements due to the bridging phenomenon, the characteristics of localization did not change intensively. Finally, to establish better engineering characteristics of studied systems, a correlation between bridging and mechanical performance of specimens was made which shows the detail of bridging occurrence under compressive loading.
Thesis (Ph.D.) -- University of Adelaide, School of Civil, Environment & Mining Engineering, 2020

In recent years, fibre reinforced polymer (FRP) materials have demonstrated enormous potential as materials for repairing and retrofitting concrete bridges that have deteriorated from factors such as electro-chemical corrosion and increased load requirements. However, concerns associated with fire remain an obstacle to applications of FRP materials in buildings and parking garages due to FRP’s sensitivity to high temperatures as compared with other structural materials and to limited knowledge on their thermal and mechanical behaviour in fire. This thesis presents results from an ongoing study on the fire performance of FRP materials, fire insulation materials and systems, and FRP wrapped reinforced concrete columns. The overall goal of the study is to understand the fire behaviour of FRP materials and FRP strengthened concrete columns and ultimately, provide rational fire safety design recommendations and guidelines for FRP strengthened concrete columns. A combined experimental and numerical investigation was conducted to achieve the goals of this research study. The experimental work consisted of both small-scale FRP material testing at elevated temperatures and full-scale fire tests on FRP strengthened columns. A numerical model was developed to simulate the behaviour of unwrapped reinforced concrete and FRP strengthened reinforced concrete square or rectangular columns in fire. After validating the numerical model against test data available in literature, it was determined that the numerical model can be used to analyze the behaviour of concrete axial compressive members in fire. Results from this study also demonstrated that although FRP materials experience considerable loss of their mechanical and bond properties at temperatures somewhat below the glass transition temperature of the resin matrix, externally-bonded FRP can be used in strengthening concrete structural members in buildings, if appropriate supplemental fire protection system is provided over the FRP strengthening system.
Thesis (Ph.D, Civil Engineering) -- Queen's University, 2009-12-17 14:11:27.931