Rozprawy doktorskie na temat „RCC BEAMS”

The structural behaviour of simply supported reinforced concrete (R.C.) beams strengthened in flexure by externally bonded steel or fibre reinforced plastic (FRP) plates has been investigated. A novel theoretical model coupled with simple (hence, practical) procedure(s) for designing such beams against premature plate peeling failure has been developed. The theoretical model and the design procedures have been validated by an extensive number (169) of mainly large-scale test data (using steel or FRP plates) from other sources. The effects of variations in the magnitude of Young's modulus for FRP plates on the potential changes in the flexural ultimate load of R. C. beams with externally bonded FRP plates, in the absence and/or presence of plate peeling, have been investigated in some detail with the theoretical predictions of various failure loads and associated modes of failure supported by an extensive number of test results from other sources. Moreover, brief theoretical parametric studies for other first order composite beam design parameters have also been carried out in order to clarify the effects of variations in such parameters on the predicted modes of failure. It has been shown (both, theoretically and by using large scale experimental data) that the load bearing capacity for a plated beam could (under certain circumstances) be significantly lower than even that for the corresponding unplated beam with the mode of failure being of an undesirable brittle nature. Such brittle failures can obviously have serious implications in practice, where this method has been used extensively for upgrading both bridges and buildings in a number of countries, with the design calculations very often not having properly accounted for the possible occurrence of premature plate peeling phenomenon, especially when FRP plates have been used. Further work in this area included a quantitative theoretical insight into the effect of pre-cracking of the beams (under service conditions) on the ultimate plate peeling load. A critical quantitative examination of a number of previously available theoretical models, as proposed by others, has also been carried out, and some of these models for predicting the plate peeling failure of R. C. beams have been shown to suffer from rather serious shortcomings.

The objective of this research program is to further evaluate the performance and constructability of reinforced concrete (RC) column-steel beam-slab systems (RCS) for use in low- to mid-rise space frame buildings located in regions of high wind loads and/or moderate seismicity. To better understand these systems, two full scale RCS cruciform specimens were tested under bidirectional quasi-static reversed cyclic loading. The experimental portion of this research program included the construction and testing of two full-scale cruciform specimens with identical overall dimensions but with different joint detailing. The two joint details evaluated were joint cover plates and face bearing plates with localized transverse ties. The construction process was recorded in detail and related to actual field construction practices. The specimens were tested experimentally in quasi-static reversed cyclic loading in both orthogonal loading directions while a constant axial force was applied to the column, to simulate the wind loads in a subassembly of a prototype building. To compliment the experimental work, nonlinear analyses were performed to evaluate the specimen strength and hysteretic degradation parameters for RCS systems. In addition, current recommendations in the literature on the design of RCS joints were used to estimate specimen joint strength and were compared with the experimental findings.

La thèse décrit avec beaucoup de détails les efforts déployés pour comprendre les processus physiques à l’intérieur du Booster de Charge SPIRAL1 (SP1 CB). Cet appareil accepte les faisceaux d’ions mono-chargés de différentes masses et augmente leur charge vers des états plus élevés. Dans le cadre de la mise à niveau de SPIRAL1, la R&D autour de la technique 1+/N+ présente un intérêt primordial pour optimiser les rendements des faisceaux d’ions radioactifs (RIB). Dans ce contexte, la thèse commence par une présentation théorique des ensembles cible-source de l’installations SPIRAL1, de la ligne de transport de faisceaux à basse énergie et des principes de la physique des plasmas pour la production d’ions fortement chargés dans les plasmas de source d’ions RCE (Résonance Cyclotronique Electronique). Ensuite, il y a une description des enjeux technologiques concernant la technique d’augmentation de charge 1+/ N+. Dans le chapitre suivant, les effets du gradient de champ magnétique axial, de la position du tube de décélération et de l’émittance du faisceau1+ ont été étudiés pour comprendre leur influence sur les performances du SP1 CB (efficacité de la transformation). Il a été également déduit des observations que l’efficacité de la transformation s’améliore lorsque l’émittance du faisceau 1+ est faible et que la position du tube de décélération est proche de l’entrée du SP1 CB. En parallèle, les temps de la transformation 1+/N+ pour le potassium (1 +, 2+, 4 + et 9+) ont été mesurés en pulsant le faisceau de K^1+ injecté. Les résultats de cette campagne expérimentale ont permis d’extraire les paramètres de réglage optimaux du SP1 CB qui permettent de minimiser la valeur du temps de la transformation tout en maximisant son efficacité.Afin d’étudier le transport du faisceau d’ions 1+ à travers le SP1 CB et les mécanismes physiques fondamentaux impliqués dans le processus d’augmentation de charges, plusieurs expériences ont été menées dans le cadre de cette thèse : interaction de faisceaux d’ions 1+ de différentes masses (Na^+ et K^+) dans deux plasmas RCE fait d’He et d’O_2. Les données de ces expériences (potentiels, émittance du faisceau 1+, position du tube de décélération, champ magnétique et pressions) ont été collectées et utilisées en tant que données d’entrée dans les outils de simulations numériques suivants :SIMION 3D, TraceWin et MCBC. Les simulations ont été effectuées en trois étapes: i) simulation de la transmission du faisceau 1+ à travers le SP1 CB pour chercher les lieux des pertes des ions, elle a montré un bon accord avec les résultats expérimentaux. ii) simulation de la transmission du faisceau1+ à travers une carte de potentiel reflétant la présence du plasma RCE (sans collisions) ; ça a permis de reproduire les courbes DeltaV pour les états de charge 1+ et 2+. Elle a également révélé le rôle important joué par les collisions coulombiennes dans le processus d’augmentation de charge, concluant à une analyse plus détaillée nécessaire à l’aide d’un code type Monte-Carlo (MCBC). iii) Code MCBC incluant les collisions coulombiennes du faisceau d’ions 1+ injecté dans un plasma RCE et les processus atomiques incluant l’ionisation simple et l’échange de charge. Le modèle peut reproduire les courbes expérimentales impliquant les faibles états de charge (1+ et 2+) en faisant varier chaque paramètre du plasma de manière indépendante. Une nouvelle stratégie de simulation a été développée pour estimer les paramètres du plasma à partir de ce code et des comparaisons avec les mesures expérimentales. Le résultat de ces simulations a démontré que la température des ions, la densité du plasma et la qualité du faisceau d’ions 1+ sont les paramètres critiques influant fortement sur la capture des ions 1+ et ils expliquent les différentes efficacités mesurées de la transformation 1+/N+ des Na^q+ et K^q+ dans le SP1 CB
The thesis describes with a great deal of details the efforts done to understand the physical processes inside the SPIRAL1 ECR charge breeder. This device accepts the mono-charged ion beams of different masses and charge bred them to higher charge states. In the framework of the SPIRAL1 upgrade, the R&D of charge breeding technique is of primary interest for optimizing the yields of radioactive ion beams (RIBs). In this context, the thesis begins with a theoretical discussion dealing with the different Target Ion Sources (TIS) at upgraded SPIRAL1 facility, Low Energy Beam Transport system and fundamentals of plasma physics relevant for the production of highly charged ions in ECR ion source plasmas. This is followed by description of the technological issues affecting the 1+/N+ charge breeding technique. In the final chapter, the effect of axial magnetic field gradient, position of deceleration tube and 1+ beam emittance were studied to understand their influence on the performance of the SP1 CB (charge breeding efficiency). The optimization of axial magnetic field gradient shows that the charge breeding efficiency is strongly influenced by the variation of the two soft iron rings positions around the permanent magnet hexapole. It has been deduced from the observations that the charge breeding efficiency improves when the emittance of 1+ beam is smaller and the position of deceleration tube is close to the entrance of SP1 CB. At the same time, the charge breeding times of K charge states (1+,2+,4+ and 9+) were estimated by pulsing the injected K^1+ beam. The results from these investigations revealed the optimum SP1 CB tuning parameters that can minimize the value of charge breeding time and maximize the charge breeding efficiency of the high charge states of K.In order to investigate the 1+ ion beam transport (shooting through mode) through the SP1 ECR charge breeder and the fundamental physical mechanisms involved in charge breeding process, several experiments were carried out in the framework of this thesis (the interaction of 1+ ion beam of different masses (Na^+ and K^+) in different background plasma species (He and O_2)). The data from these experiments (potentials, emittance of 1+ beam, deceleration tube position, magnetic field and pressures) were collected and given as inputs to the numerical simulation tools (SIMION, TraceWin and MCBC). The simulations were performed in three steps: i) simulation of the 1+ beam transmission through the breeder to verify the ion losses and showed good agreement with the experimental results. ii) simulation of 1+ beam transmission through a potential map that reflects the presence of the ECR plasma (without collisions) and reproduced the DeltaV curves of 1+ and 2+. It also revealed the role of Coulomb collisions in the charge breeding process leading to a necessary detailed analysis using Monte-Carlo Charge Breeding code (MCBC). iii) MCBC models Coulomb collisions of the injected 1+ ion beam in an ECR plasma and atomic processes which includes ionization and charge exchange. The code finally able to reproduce the low charge state (1+ and 2+) experimental trends by varying each plasma parameter (plasma density, ion temperature and electron temperature) independently. A novel simulation strategy has been developed to estimate the plasma parameters from charge breeding simulations. Finally, Simulations demonstrated that the ion temperature, the plasma density and 1+ ion beam quality as critical parameters influencing the 1+ ion capture and the reasons for the difference in charge breeding efficiencies between Na (in Helium plasma) and K (in Helium and Oxygen plasma) species were discussed

Comprendre et modéliser le comportement des matériaux sous irradiation électronique est un enjeu important pour l’industrie spatiale. La fiabilité des satellites nécessite de maîtriser et prédire les potentiels de surface s'établissant sur les diélectriques. Ce travail de doctorat a donc pour objectif de caractériser et de modéliser les différents mécanismes physiques (en surface et en volume) gouvernant le potentiel de charges dans les matériaux polymères spatiaux tels que le Téflon® FEP et le Kapton® HN. La mise au point d'un nouveau dispositif et d'un protocole expérimental a permis de corroborer l'existence d’une conductivité latérale des charges, souvent négligée dans les modèles physiques et numériques. Les études paramétriques, révélant l’influence de l’énergie et le flux des électrons incidents, ont permis de brosser un portrait des processus mis en jeu pour le transport (par saut ou par piégeage/dépiégeage) de charges en surface. A la lumière de cette étude, une conductivité équivalente est extraite, assimilant le matériau à un système prenant en compte les mécanismes de transport volumique et surfacique. L'analyse des évolutions non-monotones de potentiel mesurées sur les polymères spatiaux en condition spatiale a permis de révéler une dépendance de la conductivité volumique induite sous irradiation avec la dose reçue. L'étude paramétrique réalisée sur les mécanismes de transport en volume révèle une influence minoritaire du déplacement du barycentre de charges et du vieillissement physicochimique. Un modèle «0D» à un seul niveau de pièges, prenant en compte les mécanismes de piégeage/dépiégeage et recombinaison entre les porteurs de charges, a été développé. Ce modèle simplifié permet de reproduire qualitativement les évolutions de potentiel expérimentales en fonction du débit de dose et lors d'irradiations successives
Charging behaviours of space dielectric materials, under electron beam irradiation, is of special interest for future spacecraft needs, since this mechanism could induce electrostatic discharges and consequently damages on the sensitive systems on board. In order to assess the risks of charging and discharging, this work aims at understanding the overall charge transport mechanisms and predicting the electrical behaviour of the insulator materials, especially Teflon® FEP and Kapton® HN. For an optimized prediction, the first part of our work is thus to check whether lateral conduction process can take place in the overall charge transport mechanism. Through the definition of a new experimental set-up and protocol, we have been able to discriminate between lateral and bulk conductivity and to reveal the presence of lateral conductivity that is enhanced by radiation ionization processes. We have been able to demonstrate as well that lateral intrinsic conductivity is enhanced with the increase current density and when approaching the sample surface. The second part of our work deals with the characterization of the electrical charging behaviour of Teflon® FEP under multi-energetic electron beam irradiation and the modelling of the overall bulk charge transport mechanisms. An experimental study on charge potential evolution as a function of electron spectrum, electric field, relaxation time, dose and dose rate, was performed. A numerical model has been developed to describe the effect of the different abovementioned mechanisms on the evolution of the surface potential. This model agrees correctly with the experimental phenomenology at qualitative level and therefore allows understanding the physical mechanisms steering charge transport in Teflon® and Kapton®

In this project Meshless local Petrov Galerkin (MLPG) method is utilized for the flexural analysis of simply supported RCC beams strengthened with FRP laminates. This method uses the moving least-squares (MLS) approximation with different weight functions to interpolate the field variables and uses a local symmetric weak form (LSWF). The beams under consideration are rectangular and T-beams reinforced either on tension face or on both faces as per IS 456:2000. The proposed method is first applied to unstrengthened beam to check its applicability. The computed displacements are in good accord with the displacements attained using code formula. Then, it is extended to beams strengthened with FRP laminate. A parametric study is carried out to study the effect of disparity of field nodes in the global domain, integration cells in the sub domain and young`s modulus on the displacement. The efficiency of the algorithm developed is verified.

Wind is a phenomenon of great complexity because of the many flow situations arising from the interaction of wind with structures. Wind is of the most significant forces of nature that must be considered in design of buildings. The characteristics of wind-induced loads on buildings continuously vary in temporal and spatial dimensions. Adequate design of buildings depends on the success in predicting the actual effects of turbulent wind forces to account for the most critical design scenarios which may occur during a certain design period. Under the action of lateral load, a tall building can subjected to lateral or torsional deflection. Due to this lateral stiffness is a major criterion in the design of high rise building. From the past studies, it is found that to resist the lateral force, bracing system in a frame model is highly economical and efficient method. Wind loading computed from wind tunnel test carried out on square shape of frame model. This thesis is composed of two major parts (1) Experimental study and (2) Response study. In the first part of thesis, square shape model is tested in wind tunnel in order to find differential pressure on the surface of model at 140 pressure points under isolated condition with three different wind incidence angle named as 00, 300 and 600. In the second part of thesis, study is carried out to investigate the behaviour of building under wind load obtained experimentally in first part of thesis. A G+17 frame model having RCC beams and columns of plan area 20m X 20m and first storey height is 4.75m and remaining storey’s height is 3.25m, is subjected to wind speed of 47m/s. And the same model is reinforced with X-bracing system at each corner of the building with an angle of size ISA 200X200X25mm. STAAD PRO software is used to analyze the building model subjected to wind load. The response study includes axial force, moment about both axes and displacement under various wind incidence angle. Behaviour of frame with and without bracings is also compared.

Concrete is the most widely used material in the world for construction of infrastructures and there are quite a few gaps in understanding its behaviour under different loads. Fracture in concrete occurs at pre-existing crack tip upon the formation of a fracture process zone (FPZ) with several toughening mechanisms such as micro-cracking, aggregate bridging, crack branching etc., taking place resulting in energy dissipation, which resists further crack propagation. This FPZ is responsible for the post-peak softening response under tension and size effect. The behaviour of reinforced concrete depends on the combined action of concrete and its embedded longitudinal reinforcement. The study of fracture in reinforced concrete is much more complex due to micro-structural changes in concrete, interaction between the concrete and steel and bond between them. There may be other failure mechanisms involved, such as yielding and slippage of steel, and de-lamination between steel and concrete. Under inadequate provision of stirrups or in the case of deep beams, a beam subjected to transverse loads tends to fail by shear. There is a need to develop analytical models which can address failure under shear using the fracture mechanics theory in order to reflect the size effect and the failure mechanisms. In addition, combined flexural and shear mode of failure in reinforced concrete structures also needs to be studied by considering the internal microcracking mechanisms and the effect of size. Bridge decks, highway pavements, airport pavements and offshore structures made of reinforced concrete are subjected to variable amplitude fatigue loading. The mechanism of fatigue in concrete is not yet clearly understood when compared to metallic materials. Hence, it is important to characterize the behaviour of concrete structures subjected to fatigue loading and understand the fracture mechanisms. In this research work, the problems listed above are addressed through experimental investigations into fracture and fatigue behavior of plain and reinforced concrete using the acoustic emission technique. Important elastic and fracture properties of plain concrete including the size independent fracture energy, fracture toughness, critical crack tip opening displacements, critical crack length and size of process zone are determined. These serve as input parameters in the finite element based fracture mechanics models for analysis of concrete structures. Furthermore, the mechanisms of micro-crack formation, their coalescence, macrocrack formation and eventual failure under monotonically increasing and fatigue loading are determined. The evolution of damage under different loading are studied. The effect of varying beam size (depth) and reinforcement ratios are studied in order to understand the fracture mechanisms for failure under flexure, shear, combined flexure-shear and fatigue. It is seen that the acoustic emission technique could provide vital information on the micro-cracking characteristics in concrete.

碩士
國立台灣工業技術學院
營建工程技術研究所
85
The flexural strength, flexural stiffness, and shear strength of RC beams reduce considerably after exposure to fire. The strength of concrete decreases after fire imposition and so is the balance steel ratio.This will decrease the ductility of a beam and the shear strength contribution of concrete.As a result, the failure mode of the beam will possibly be changed from flexural failure to shear failure. Twelve 30 cm×50 cm×340 cm RC beams, with several different stirrup spacings, have been made and conducted to fire simulation tests and loading tests. The results show that the flexural stiffness of RC beams reduce pronouncedly after fireexposure, and the reduction of shear strength of damaged beams is more evident than that of the flexural strength. Both the modified conventional RC beam model and the finite element model, account for the change of stress- strain curves of the reinforcement and the concrete, have been used to analyze the fire-damaged beams, Good agreements between the test results and the analytical ones are obtained. As a modified ACI shear strength equation for fire-damaged concrete is adopted to calculate the shear strength of the damaged beam, a reasonable however conservative result is achieved. An under- reinforcement design and an adequately increase of shear reinforcement, considering the weaker shear strength of damaged concrete, will avoid the beam to have the brittle failure either in compression or in shear, and enable the beam to retain a reasonable ductility after fire damage.

碩士
國立中興大學
土木工程學系
87
Up to the present, most the researches involving the influence of FRP sheet on the flexural strength mainly investigated the loading behavior and failure mechanism after strengthening by binding FRP fabric material on the tested beams. However, the tests carried out in this paper adhered the pre-stressed FRP sheets to the conventional R.C. beams to form new beams which act like pre-stressed beams. This paper mainly investigates the loading behavior and failure mechanism after this type of strengthening. In addition, the paper also studies the influence of various angles of shear strengthening sheets on the innovations of shear strength. The test results indicate that in the shear strengthening the FRP sheets at the angle of 45 degree can increase the strength more than those at a vertical angle. It is mainly due to that the diagonal tension caused by shear force can be resisted directly by the fabric direction of FRP material. Concerning the flexure strength of pre-stressed sheets, the pre-stressed GFRP arches the beam and increases R.C. beam''s flexure strength in some case. The deformations of the beams with pre-stressed GFRP sheets are smaller than those with regular sheets.

碩士
國立中興大學
土木工程學系
88
It is generally acknowledged that the bonding strength on the interface between fiber and concrete is the major problem in the research on the strengthening of R.C. beams using FRP. Since this paper conducts research regarding the strengthening using prestressed fiber, the interface problem is even more critical. One of the major topics of the study is to develop and propose a bonding way by which the bonding strength can be improved. Experiments show that the proposed way is effective. On the other hand, since the strengthening using prestressed fiber is still at the stage of testing in laboratories, the way to prestress the fiber used in the laboratories is actually not applicable on working sites. The other major topic of the study is to develop a prestressing method workable on working sites. According to this method, the prestressing and bonding work can be conducted under the bottom of the beams. The prestressed fiber can stick to the cambered beams through tying them together with cotton threads. Experiments indicate that the proposed method can camber up beams step by step and make them behave just like the traditional prestressed beams.

碩士
國立臺灣科技大學
營建工程技術學系
86
The purpose of this research work was to study the shear strengthening of R.C. beams using Carbon Fiber Sheet (CFS) composites. An additional experimental work was carried out to study the anchorage strength provided by out of plane contact surface. The test results indicated the anchorage strength per unit width of contact surface increased with out of plane angle and the contact length. Large increment in strength per unit contact length was observes when the contact length was short. When the CFS composites were used to strengthening the shear capacity of RC beams,the results were highly affected by the arrangement of CFS,including location, shape and direction of carbon fiber. Closely arranged strip type CFS will provide large contact surface and curtail the spread of separation between CFS and concrete at the same times.

碩士
國立臺灣科技大學
營建工程技術學系
83
The ductility of beam sections in some existing earthquake resistant R.C. building may be insufficient due to insufficient compression stell , poor concrete quality , large stirrup spacing and inappropriate reiforcing bar details . In the study , curvature ductility of beam sections was evaluated analyticaly , and it is found that ： (1) a ductility factor of 7 is required for R.C. sections with f'' c=210kg/cm2 and Fy=2800kg/cm2 , (2) concrete strength has significant effect on curvature ductility and less effect on flexural strength , (3) the regulations on tensile and compressive steel of ACI Code are too brief to assure sufficient ductility . In addition to analytical investigation , 9 full scale beam tests were carried out to study the effect of concrete cover confinement on the ductility of R.C. beams . It is found from the tests that ：(1) confine mechanism A was able to confine concrete cover when stirrup spacing was not too large , (2) confine mechanism B was able to confine concrete cover effectively , (3) bond strength could be problem when concrete strength is too low .

碩士
國立臺灣科技大學
營建工程技術學系
84
The main purpose of the thesis is to develop an automatic design program for reinforced concrete beam , it can read all the necessary information from the ETABS input and output files automatically and do the beam reinforcement detail design for a whole building . Thus, it would not only save a lot of human efforts and time but also reduce the human mistakes . The main function of the program is to design the beam flexural reinforcement , shear reinforcement and cut points. It consider the whole disposition automatically, and there are three choices of design which includes strong seismic design,medium seismic design and ordinary design . It can also draw the moment diagram and the reinforcement arrangement diagram automatically . The results from this program were compared with the results from CONKER for several examples to verify the correctness and capability of this program .

碩士
國立中興大學
土木工程學系
87
When to remove the shoring beneath the slabs and beams depends on whether the beam and slab structures have developed into a status which they are able to take all the gravity loads or not. In this study, the timing to remove the shoring is studied by both developments of concrete strength and structure strength. The method of study includes numerical analysis and experiments. The research results indicate that in the first 28 days the development of the structure stiffness can be considered the development of the elasticity of the concrete numerical analysis. The values of the structure stiffness in experiments are a bit greater than those in numerical analysis but both developing rates are very similar. It is recommended that one more choice to decide the removal timing is to refer to the of the structure stiffness. A simple way to perform experiments to measure the stiffness value is suggested herein.

博士
國立中興大學
土木工程學系
93
ABSTRACT The main topic of this dissertation is to use prestressed glass fiber reinforced polymers (PGFRP) to strengthen beams and hollow circular specimens. In these years, carbon fiber- reinforced polymer (CFRP) material has been popular used to repair or rehabilitate in deteriorated reinforced concrete ( ) structures. However, the stiffness variation between CFRP and concrete material lowers the effort in transferring the prestress from CFRP sheets to member. The reason for why this study chose glass fiber- reinforced polymers (GFRP) material was the Young’s modulus of GFRP material being quite close to concrete material. This dissertation was divided into two parts, Part I to study the strengthening of reinforced concrete ( ) beams using prestessed glass fiber-reinforced polymer (PGFRP) and Part Ⅱ to study the strengthening of hollow circular specimens using PGFRP. The main subject of part Ⅰ of this dissertation is to compare the test and theoretical analysis strengthening results in using GFRP and PGFRP sheets for the load-carrying capacities (ultimate loads) and deflections of beams. Two beams shapes, T and -shaped, were used as the under-strengthened and over-strengthened beams. The GFRP sheets were prestressed to one-half their tensile capacities before bonded to the T and -shaped R. C. beams. The prestressed tensions in the PGFRP sheets caused cambers in R.C. beams without cracking on the tensile faces. The PGFRP sheets also enhanced the load-carrying capacities. The test results indicate that T-shaped beams with GFRP sheets exhibit an increase of load-carrying capacity by 55% while the same beams with PGFRP sheets can increase 100%. The -shaped beams with GFRP sheets can increase the load-carrying capacity by 97% while the same beams with PGFRP sheets increase the capacity by 117%. Under the same external loads, beams with GFRP sheets produce larger deflections than beams with PGFRP sheets. In the theoretical part, the equations obtained by theory match the test results quite well. It is suggested that this analytical method can be widely used for analyzing and designing beams strengthened using GFRP or PGFRP sheets. The main subject of part Ⅱ of this dissertation is to study the strengthening of hollow and solid circular specimens using PGFRP. The purpose of this study is to strengthen the damaged solid and hollow circular specimens which were used to simulate the structures of large hollow circular pipes. The test results show that GFRP can increase a great deal of strength for specimens, even for the broken specimens. For instance, the solid specimens wrapped by GFRP can increase the strength around 200% and the hollow specimens wrapped by GFRP can even increase 400%. The results also show that PGFRP can’t increase more strength than GFRP. But PGFRP can increase the lateral stiffness of the specimens. In the theoretical part, the equations obtained by theory match the test results very well. In this study, all the test results are greater than the theoretical results within a range of 10%.

碩士
國立中央大學
土木工程學系
85
ABSTRACT In this thesis, the mechanical behavior of the bonded patch method to strengthen the reinforced concrete structural elements is investigated. The reinforced concrete beams are strengthened with fiber composite plates epoxy bonded to the tension face of the beams to improve the yield strength, stiffness, flexural strength and ductility of the beam. In the analysis, the following assumptions are made :(1) concrete and steel are elastic-perfect plastic materials, no account of strain hardening ,(2) The fiber composite plate is an elastic material, no account of plastic behavior, The plate offer tension after steel yielding,(3) The interface between beam and plate is fully-composite, no slip between composite plate and concrete plate ,(4)no slip between steel and concrete. The finite element method is used to predict the elastic-plastic behavior of the beams strengthened with fiber composite plates. A parameter study is conducted to investigate the effect of design variables such as plate length, thickness, stiffness, end zone anchorage type, and concrete compression strength for specimens with a relatively low reinforcement ratio. The analysis shows good result for both shear failure and flexural failure, and the fiber composite plates are suggested as the best approach for beam strengthening.

碩士
國立中興大學
土木工程研究所
79
ACI 318-89規範對剪力強度之規定, 經前人研究發現, 應用高強度混凝土時, 有過於 保守之嫌, 并建議作若干修正。至於該規範及前人研究結果, 是否仍能適用大飛灰含 量高強度之RC梁, 則有待進一步研究。 本研究共制作11個試體進行試驗, 探討飛灰取代量達25% 之高強度混凝土RC梁之剪力 行為, 考慮之變化因子包括: 剪力跨度與有效深度比(a/s),混凝土抗壓強度(fc'') 及 縱向拉力鋼筋比(ρ)。結果顯示,ACI 318-89 規範及前人研究之建議式, 應用於大飛 灰含量高強度混凝土RC梁之剪力強度評估時, 均不甚理想, 與實測值之差異尚大。本 研究乃因而依據試驗結果, 以既有模式為基礎數值模擬處理后, 提出一更為合理之剪 力強度預測模式; 該模式亦經證實適用於一般高強度混凝土RC梁。

碩士
國立成功大學
建築學系碩博士班
94
The objectives of this paper were : 1.To establish the empirical equations for residual strength ; residual peak strain and the stress-strain curves of concrete after different temperature damages ; 2.To evaluate the residual shear capacities of RC short beams after fire damage. The method of research were as follows： 1.Concrete cylinders with dimension∮15cm×30cm; f’c=29.7to50.9MPa ; fire temperatures=room temperature,200℃,300℃,400℃,500℃,600℃,700℃,800℃were tested.The residual stress-strain curve for each cylinder was recorded ;2.Three rebars were picked up for each D10,D16,D25 dimension. The yield stress of reinforcements at room temperature were from 398 to 493MPa.The fire temperature of rebar were : room temperature,400℃,700℃and 800℃.The residual stress-strain curves were recorded for all the tested rebars ;3.26 Simply supported short RC beams with one concentrated load at mid-span were tested. The cross-sectional dimension of beams were 250mm×300mm and 250mm×400mm.The span of beams was 85cm. f’c =33.8 to 52MPa;ρ=1.8％andρ=2.6％.Beams without stirrup,with #3@12cm and #3@20cm stirrups were designed for test. The fire temperatures were : room temperature,400℃,700℃and 800℃.The cross-sections of all the tested beams were heated to the target temperature completely and uniformly.All the beams were tested under universal machine up to failure. The results of this paper were： 1. For concrete cylinder test－The empirical equations for the residual compression strength, the residual peak strain and the residual stress-strain curve were proposed. All the calculated values were compared to the tested values with reasonable errors : 10.7％ for residual strength and 7.0％ for residual peak strain. 2. For rebar test－It was found that the equations of residual yield strength and residual fracture strength of fire damaged rebars proposed by Yang et al(*7)were feasible for domestic fire damaged rebars. 3. For shear capacity test－A modified equation from the shear equation of the ACI code was proposed to calculate the residual shear capacities of RC short beams after fire damage.The calculated values were compared to the tested values with average error 12.9％.

As the construction industry is rapidly growing, the importance given to sustainable construction techniques has increased, to protect the environment and the limited reserves of natural resources. In order to reduce the negative environmental impact of the construction industry and to meet the increasing global demand for raw materials, the significance of recycling and reusing construction waste has increased over the years. Considering the wide applications of concrete and the large consumption of coarse aggregates used in concrete on a global scale, using Recycled Aggregate (RA) in concrete is an environment-friendly and sustainable construction alternative. However, Recycled Aggregate Concrete (RAC) does not exhibit adequate structural performance due to its inferior material properties compared to those of Natural Aggregate Concrete (NAC). At present, RAC is restricted to limited structural use and is extensively used only in pavements and as shotcrete in tunnels. Some previous studies have shown that RAC with adequate structural performance can be produced using various techniques. In this study, the particular technique of adding another material, Steel Fibre (SF), is investigated. SF improves the mechanical performance of RAC and makes it suitable for structural applications, especially under flexural load. This research aims to replace NAC with RAC that incorporates SF. The use of the new material, Steel Fibre Reinforced Recycled Aggregate Concrete (SFRRAC), in fabricating structural members subjected to flexure is proposed to gain advantages in terms of environmental effects, production costs and structural properties. Structural members fabricated using a new material such as SFRRAC should be designed according to proper design models and guidelines. The current design guidelines are limited to NAC and cannot be directly applied to SFRRAC due to the change in the material properties. This research proposes a design model for SFRRAC beam cross-sections under flexure, developed using a reliability based framework consisting of the following four parts: (i) a new theoretical model development for predicting the moment-capacities of SFRRAC beam cross-sections; (ii) experimental investigation of SFRRAC specimens at material-level and member level; (iii) numerical investigation on SFRRAC beams using Finite Element Analysis (FEA); and (iv) capacity factor calibration for a SFRRAC flexural capacity prediction model using the theoretical predictions and the adaptively combined database of experimental and FEA results.

碩士
國立臺灣大學
土木工程學研究所
90
A joint research effort among US, Japan and Taiwanese researchers on large scale frame testing of steel and concrete composite structures has been launched in 2001. It is the consensus that a 2-D full-scale three-story three-bay RCS moment resisting frame be constructed and tested in the NCREE to accelerate the world-wide implementation of RCS structural systems in real application. In this research, cyclic tests were conducted on the roof beam-to-RC column and the RC column to foundation subassemblage specimens. In this research, a total of six specimens have been fabricated and tested in order to investigate the effectiveness of three different kinds of connection details. It includes: (a) the splice location effects on the 1st floor RC column to the foundation joint (FF series specimens), (b) the axial load effects to the responses of RC column (FR series specimens), (c) the anchorage details of the roof interior RCS beam-to-column joint (R series specimens). FF series experimental results show that the performance of the one-meter high splice location is better than that on the top face of the foundation. FR series experimental results show that higher axial loads make higher column flexural strength. R series experimental results show that the proposed reinforcing anchorage end plate details can satisfactorily provide the needed anchorage for column bars. For FF and FR specimens, the analytical moment versus curvature relationships were computed. It assumes plane remains plane after bending and incorporates the low-cycle fatigue and the soften-branch model for the vertical reinforcement and the Mander’s confined concrete model. It is illustrated that the experimental cyclic cantilever column load versus displacement response skeleton curves can be accurately predicted by employing the Moment-Area Method. For R series specimens, the column end lateral displacements due to column deformations, beam deformations, panel zone bearing deformations and panel zone shear deformations can be separated by the proposed method. Good agreements with the subassemblage test results are also observed in the analytical cyclic responses simulated by using a general-purpose inelastic structural analysis software PISA2D. The complete three-story three-bay analytical RCS frame model is also constructed and calibrated based on the test results. Finally, nonlinear static and dynamic time-history analyses are performed in order to investigate the most possible ultimate lateral strength and the inelastic demands imposed on the frame specimen under the simulated earthquake effects.