O presente trabalho apresenta os resultados obtidos na pesquisa sobre o uso de revestimentos resistentes de argamassas de cimento e areia na reabilitação de paredes de alvenaria, quando solicitadas à compressão axial, compressão diagonal e flexão de painéis. Os ensaios foram baseados nas normas NBR 8949, ASTM 519 e NBR 14322 respectivamente. O objetivo dos ensaios realizados foi observar o comportamento estrutural de paredes de blocos de concreto revestidas com diversos tipos de argamassa de cimento e areia, os quais resultaram de combinações de argamassa de resistência baixa ou mais elevada, telas de aço soldadas, fibras de aço, fibras de polipropileno e conectores de cisalhamento. Os modelos dos ensaios de compressão axial tinham dimensões de 39 x 81 cm e foram confeccionados em gabaritos de aço para uma maior precisão durante o assentamento. Para os ensaios de compressão diagonal foram idealizados gabaritos de madeira para confecção e transporte dos modelos cujas dimensões eram de 80 x 80 cm. Nos ensaios de flexão as paredes (80 x 1,60) foram ensaiadas com a face maior na posição horizontal com duas situações de carregamento. Depois de terminados estes ensaios e analisados os resultados foi realizada também uma série de ensaios sobre painéis de alvenaria, submetidos a forças distribuídas numa região pequena do topo da parede e ensaiados em três situações diferentes: paredes íntegras, reabilitadas e reforçadas. A decisão de ensaiar painéis com aberturas se deu pela intenção de criar situações de desvio de tensões no plano da parede, provocando esforços de compressão, tração e cisalhamento. Todos os ensaios foram realizados com uso de equipamento hidráulico servo-controlado INSTRON, controlando-se a velocidade de deslocamento, o que permitiu observar o comportamento das paredes após à sua resistência de pico. Pode-se dizer que a técnica em estudo apresenta diversos aspectos interessantes, que podem ser explorados tanto na reabilitação (reforço ou reparo) de estruturas de alvenaria, como na execução de estruturas novas com exigências especiais de desempenho. / This paper reports on the results of a study about the use of resistant overlays of cement and sands mortars in the rehabilitation of masonry walls subjected to axial and diagonal compression and flexure. The tests were carried out according to the NBR8949, ASTM 519 and NBR 14322 codes. The purpose of the tests was to observe the structural behavior of concrete block walls covered with several combinations of materials: plain mortar with two different strengths, welded steel mesh, steel fibers, polypropylene fibers and shear connectors. The dimensions of the specimens subjected to axial compression tests were 390 x 810 mm. They were built inside steel templates for a better precision during their construction. Wooden templates were set up for the diagonal compression tests to build and transport the 800 x 800 mm specimens. In the flexure tests, the walls (800 x 1600 mm) were tested with the larger side in the horizontal position, using two loading situations. After the conclusion of these tests and an analysis of the results, a series of tests was carried out on masonry panels subjected to loads distributed over a small area at the top of the wall. Three different situations were tested, i.e., undamaged walls, rehabilitated walls and reinforced walls. The decision to test panels with openings was based on the idea of creating situations to deviate the stresses in the plane of the wall, thereby inducing compression, tension and shear. All the tests were performed using an universal servo-controlled INSTRON machine to control the displacement speed, allowing the observation of the behavior of the walls after their peak resistance. Based on this study, it can be stated that this technique offers several interesting aspects that may be applied both in the rehabilitation (strengthening or repair) of masonry structures and in the construction of new structures with special performance requirements.

CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / The reinforced concrete structures, when properly designed and performed, have prolonged its life. However, the lack of proper maintenance, acting loads greater than the design ones, pathological manifestations due to aggressive environment and accidents can impair the performance of the structure requiring the need for repair or structural strengthening. The technique of structural strengthening with application of carbon fiber reinforced polymer (CFRP), bonded externally to the reinforced concrete has advantages such as fast execution, which added to the characteristics of the composite as a high modulus of elasticity make wide its use. The aim of this study is to analyze through an experimental program the structural behavior of reinforced concrete beams strengthened in bending with CFRP. The methodology used was the production of three groups of five RC beams each one, with the same dimension of rectangular cross section, for bending test. The first group of beams was called VA. The second and third groups, called VB and VC and had different ratio of reinforcement. In each group of five beams, one beam was not strengthened (reference beam) and the remaining beams were strengthened with two, three, four and five layers of carbon fiber. The experimental results indicate the efficiency of strengthening, noting an increase in stiffness in all strengthened beams. The increase of load capacity was also observed in all groups of beams varying between 9,11% and 16,69%, 55,14% and 86,83%, 89,46% and 126,18%, of the beams of group VA, VB and VC, respectively in relation to the reference beam of each group. Of the carried through study was observed the excellent performance of strengthening in bending with carbon fiber especially in beams with the lowest ratios of reinforcement (group C), besides gathering a lot of information that can be useful for design criteria of the recovered and strengthened structures. / As estruturas de concreto armado, quando convenientemente projetadas e executadas tÃm sua vida Ãtil prolongada, porÃm, a falta de manutenÃÃo adequada, as solicitaÃÃes de cargas superiores Ãs de projeto, as manifestaÃÃes patolÃgicas devido ao meio ambiente agressivo e a ocorrÃncia de acidentes podem comprometer o desempenho da estrutura exigindo a necessidade de uma recuperaÃÃo ou reforÃo estrutural. A tÃcnica de reforÃo estrutural com a aplicaÃÃo de polÃmeros reforÃados com fibra de carbono (PRFC) colados externamente a peÃas de concreto armado apresenta vantagens como a rÃpida execuÃÃo que, somada a caracterÃsticas do compÃsito como alto mÃdulo de elasticidade fazem largo o seu uso. O objetivo desse trabalho à analisar atravÃs de um programa experimental o comportamento estrutural de vigas de concreto armado reforÃadas à flexÃo com PRFC. A metodologia utilizada foi a produÃÃo de trÃs grupos de vigas de concreto armado, com a mesma dimensÃo de seÃÃo transversal retangular para ensaio à flexÃo. O primeiro grupo, denominado grupo VA, foi dimensionado com seÃÃo normalmente armada. O segundo e terceiro grupo de vigas, aqui denominados grupo VB e grupo VC, respectivamente, foram dimensionados com seÃÃo subarmada, com taxas de armaduras distintas. Cada grupo possuÃa cinco vigas, sendo que, uma viga nÃo foi reforÃada (de referÃncia) e as demais vigas foram reforÃadas com duas, trÃs, quatro e cinco camadas de fibra de carbono. Os ensaios experimentais comprovaram a eficiÃncia do reforÃo, constatando-se um aumento de rigidez de todas as vigas reforÃadas. Observou-se tambÃm o aumento da capacidade resistente em todos os grupos de vigas, variando entre 9,11% e 16,69%, 55,14% e 86,83%, 89,46% e 126,18%, das vigas dos grupos VA, VB e VC, respectivamente, em relaÃÃo à viga de referÃncia de cada grupo. O estudo demonstrou o excelente desempenho do reforÃo à flexÃo com fibra de carbono, especialmente nas vigas com menores taxas de armadura (grupo VC), alÃm de reunir uma sÃrie de informaÃÃes que podem ser Ãteis para critÃrios de projeto de estruturas recuperadas e reforÃadas.

Microalloyed steels are widely used in oil and gas pipelines. They are a class of high strength, low carbon steels containing small additions (in amounts less than 0.1 wt%) of Nb, Ti and/or V. The steels may contain other alloying elements, such as Mo, in amounts exceeding 0.1wt%. Microalloyed steels have good strength, good toughness and excellent weldability, which are attributed in part to the presence of precipitates, especially nano-precipitates with sizes less than 10nm. Nano-precipitates have an important strengthening contribution, i.e. precipitation strengthening. In order to fully understand steel strengthening mechanisms, it is necessary to determine the precipitation strengthening contribution. Because of the fine sizes and low volume fraction, conventional microscopic methods are not satisfactory for quantifying the nano-precipitates. Matrix dissolution is a promising alternative to extract the precipitates for quantification. Relatively large volumes of material can be analyzed, so that statistically significant quantities of precipitates of different sizes are collected. In this thesis, the microstructure features of a series of microalloyed steels are characterized using optical microscopy (OM) and scanning electron microscopy (SEM). Matrix dissolution techniques have been developed to extract the precipitates from the above microalloyed steels. Transmission electron microscopy (TEM) and x-ray diffraction (XRD) are combined to analyze the chemical speciation of these precipitates. Rietveld refinement of the XRD pattern is used to fully quantify the relative amounts of the precipitates. The size distribution of the nano-precipitates (mostly 10 nm) is quantified using dark field imaging (DF) in the TEM. The effects of steel chemistry and processing parameters on grain microstructure and the amount of nano-precipitates are discussed. Individual strengthening contributions due to grain size effect, solid solution strengthening and precipitation strengthening are quantified to fully understand the strengthening mechanisms of the steels. / Materials Engineering

Recently, the use of Mechanically Fastened Fiber-Reinforced Polymer (MF-FRP) systems has emerged as a viable means for flexural strengthening of reinforced concrete members. The technique is suitable for emergency repairs where constructability and speed of installation are critical requirements. The MF-FRP system consists of pre-cured FRP laminates with enhanced longitudinal bearing strength that are attached to the concrete substrate by means of mechanical steel anchors. This research project presents an experimental investigation comprising a series of flexural tests on scaled one-way RC slabs. The test matrix includes MF-FRP strengthened specimens, a counterpart with the externally bonded (EB) FRP reinforcement, and a control specimen. The effects of fastener layout and laminate length on strength increase and failure mode were studied. It is shown that with proper selection of fastener layout the MF-FRP system results in a significant deformability and strength increase, where the latter is comparable to that attained using EB-FRP sheets. Specific gaps on the existing analytical procedures for flexural strengthening with MF-FRP systems are finally discussed.

Fibre-reinforced-polymer (FRP) composites have been widely used for the flexural strengthening of reinforced concrete (RC) structures. Flexural strengthening methods with FRP include external bonding of FRP composites (EB system) and insertion of FRP strips or bars into grooves cut into the concrete (near-surface-mounted or NSM system). Recently, a prestressed FRP strengthening system has been developed and investigated, whereby the FRP reinforcement is pretensioned prior to attachment to the concrete to maximize the use of the high tensile strength of the FRP reinforcement. Existing studies have shown that the ultimate load carrying capacity and serviceability were greatly improved in FRP flexural strengthened beams. However, the only disadvantage of the FRP strengthening system is the reduction of deformability compared to that of unstrengthened structures due to the limited strain capacity of the FRP reinforcement and premature debonding failure. Structures with low deformability may fail suddenly without warning to evacuate, resulting in catastrophic failure. Therefore, a study on the improvement of deformability is critical for the effective use of FRP strengthening systems. In this study, a partially bonded concept is introduced and applied to various FRP strengthening methods, with the specific objective of increasing deformability in FRP strengthened beams. The FRP reinforcement is usually completely bonded to the concrete tensile surface, while a portion of the FRP length is intentionally unbonded in the partially bonded system in order to improve deformability while sustaining high load carrying capacity. To investigate the general behaviour of the partially bonded system, a new analytical model has been developed because conventional section analysis used for analysis of the fully bonded system is not applicable due to strain incompatibility at the FRP reinforcement level within the unbonded length. The analysis shows that a partially bonded system has a high potential to improve deformability without the loss of strength capacity. An extensive experimental program was conducted to verify the analytical model and to investigate the actual behaviour of the partially bonded beams. A total of seventeen, 3.5m long, RC T-beams were constructed and tested. One of them is an unstrengthened control beam, while the other 16 beams consist of four test groups that were strengthened by different strengthening methods: non-prestressed EB, non-prestressed NSM, 40% prestressed NSM, and 60% prestressed NSM. To allow investigation of the effect of partially unbonding, each group has different unbonded lengths and includes a fully bonded beam. For the non-prestressed EB strengthened beams, the failure mode of all beams was premature FRP debonding failure without regard to the bond condition. The ultimate strength and the ultimate deformability of the partially bonded beams were improved compared to the fully bonded beam. This was because the typical intermediate debonding failure that occurred in the fully bonded beam was avoided due to intentional unbonding in the partially bonded beams. The analytical model predicted the general behaviour of the EB strengthened beams well except at the ultimate response due to the premature debonding failure. A three-dimensional nonlinear finite element (FE) analysis was performed utilizing interfacial elements and contact modeling to investigate the debonding failure of this system. The FE analysis represented the behaviour of the debonding failure and bond stress distributions at FRP-concrete interface of both the fully bonded and partially bonded beams well. For the non-prestressed NSM strengthened beams, the premature debonding failure that occurred in the EB strengthened beams was not observed, and almost the full capacity of FRP was exhibited. Prominent stiffness reduction was observed in terms of load-deflection diagrams at the post-yielding stage with the increase of the unbonded length. This stiffness reduction increased the deformability of the partially bonded beams for a given applied load after steel yielding in comparison to the fully bonded beam. The FRP started to slip at high load levels and the concrete crushed gradually with a gradual loss of the beam’s cross-section, inducing nonlinear behaviour near the ultimate state of the beams. To address this behaviour, an advanced analytical model utilizing idealized section model and slip model is proposed to consider the FRP slip and concrete gradual failure. Prestressed NSM strengthened beams were very effective to improve the cracking load, to decrease the deflection at service load, and to increase the ultimate load compared to non-prestressed NSM strengthened beams. This improvement was greater as the prestressing level increased. The partially bonded prestressed beams showed an improvement in deformability compared to the fully bonded prestressed beams while minimizing the reduction of the ultimate load carrying capacity and serviceability. The partially bonded system was more effective to improve the deformability at higher levels of prestressing force. Based on the model developed, a parametric study was performed varying the main parameters. This showed that the FRP strengthened beam that has an FRP area (Af) less than the balanced FRP area (Af,b) of the beam has a high potential to improve the deformability as the unbonded length increases. The balanced FRP area is increased as the concrete strength and the FRP prestressing force are increased, or as the area of the steel reinforcement decreases. Finally, design recommendations and procedures are proposed for the effective use of the partially bonded system to improve the deformability of FRP strengthened concrete beams.

Fibre-reinforced-polymer (FRP) composites have been widely used for the flexural strengthening of reinforced concrete (RC) structures. Flexural strengthening methods with FRP include external bonding of FRP composites (EB system) and insertion of FRP strips or bars into grooves cut into the concrete (near-surface-mounted or NSM system). Recently, a prestressed FRP strengthening system has been developed and investigated, whereby the FRP reinforcement is pretensioned prior to attachment to the concrete to maximize the use of the high tensile strength of the FRP reinforcement. Existing studies have shown that the ultimate load carrying capacity and serviceability were greatly improved in FRP flexural strengthened beams. However, the only disadvantage of the FRP strengthening system is the reduction of deformability compared to that of unstrengthened structures due to the limited strain capacity of the FRP reinforcement and premature debonding failure. Structures with low deformability may fail suddenly without warning to evacuate, resulting in catastrophic failure. Therefore, a study on the improvement of deformability is critical for the effective use of FRP strengthening systems. In this study, a partially bonded concept is introduced and applied to various FRP strengthening methods, with the specific objective of increasing deformability in FRP strengthened beams. The FRP reinforcement is usually completely bonded to the concrete tensile surface, while a portion of the FRP length is intentionally unbonded in the partially bonded system in order to improve deformability while sustaining high load carrying capacity. To investigate the general behaviour of the partially bonded system, a new analytical model has been developed because conventional section analysis used for analysis of the fully bonded system is not applicable due to strain incompatibility at the FRP reinforcement level within the unbonded length. The analysis shows that a partially bonded system has a high potential to improve deformability without the loss of strength capacity. An extensive experimental program was conducted to verify the analytical model and to investigate the actual behaviour of the partially bonded beams. A total of seventeen, 3.5m long, RC T-beams were constructed and tested. One of them is an unstrengthened control beam, while the other 16 beams consist of four test groups that were strengthened by different strengthening methods: non-prestressed EB, non-prestressed NSM, 40% prestressed NSM, and 60% prestressed NSM. To allow investigation of the effect of partially unbonding, each group has different unbonded lengths and includes a fully bonded beam. For the non-prestressed EB strengthened beams, the failure mode of all beams was premature FRP debonding failure without regard to the bond condition. The ultimate strength and the ultimate deformability of the partially bonded beams were improved compared to the fully bonded beam. This was because the typical intermediate debonding failure that occurred in the fully bonded beam was avoided due to intentional unbonding in the partially bonded beams. The analytical model predicted the general behaviour of the EB strengthened beams well except at the ultimate response due to the premature debonding failure. A three-dimensional nonlinear finite element (FE) analysis was performed utilizing interfacial elements and contact modeling to investigate the debonding failure of this system. The FE analysis represented the behaviour of the debonding failure and bond stress distributions at FRP-concrete interface of both the fully bonded and partially bonded beams well. For the non-prestressed NSM strengthened beams, the premature debonding failure that occurred in the EB strengthened beams was not observed, and almost the full capacity of FRP was exhibited. Prominent stiffness reduction was observed in terms of load-deflection diagrams at the post-yielding stage with the increase of the unbonded length. This stiffness reduction increased the deformability of the partially bonded beams for a given applied load after steel yielding in comparison to the fully bonded beam. The FRP started to slip at high load levels and the concrete crushed gradually with a gradual loss of the beam’s cross-section, inducing nonlinear behaviour near the ultimate state of the beams. To address this behaviour, an advanced analytical model utilizing idealized section model and slip model is proposed to consider the FRP slip and concrete gradual failure. Prestressed NSM strengthened beams were very effective to improve the cracking load, to decrease the deflection at service load, and to increase the ultimate load compared to non-prestressed NSM strengthened beams. This improvement was greater as the prestressing level increased. The partially bonded prestressed beams showed an improvement in deformability compared to the fully bonded prestressed beams while minimizing the reduction of the ultimate load carrying capacity and serviceability. The partially bonded system was more effective to improve the deformability at higher levels of prestressing force. Based on the model developed, a parametric study was performed varying the main parameters. This showed that the FRP strengthened beam that has an FRP area (Af) less than the balanced FRP area (Af,b) of the beam has a high potential to improve the deformability as the unbonded length increases. The balanced FRP area is increased as the concrete strength and the FRP prestressing force are increased, or as the area of the steel reinforcement decreases. Finally, design recommendations and procedures are proposed for the effective use of the partially bonded system to improve the deformability of FRP strengthened concrete beams.

Some persons with aphasia exhibit a selective verb deficit, which results in a reduced ability to produce verbs in most contexts. A functional level (Bock & Levelt, 1994) impairment may result in impaired sentence production because the verb serves as the semantic-syntactic interface of a sentence. This interface is related to a verb’s relationship with its arguments/thematics. Arguments fill the syntactic slots of subject and object, and those same words serve as thematic roles by referring to who does what to whom. The current study investigates the effect of Verb Network Strengthening Treatment (VNeST) on sentence production using a single subject experimental design across subjects in 4 participants, 2 with nonfluent aphasia and 2 with fluent aphasia. Participants received semantic treatment aimed at re-strengthening the connections between a verb (e.g., measure) and related thematic pairs that refer to the doer and receiver of the action (e.g., carpenter/lumber, chef/sugar). The ability to produce thematic role pairs for trained verbs was tested during treatment while generalization to the ability to produce sentences containing a subject, verb, and object in a picture description task with trained verbs (e.g., The carpenter is measuring the stairs.) and semantically related untrained verbs (e.g., The nurse is weighing the baby.) was monitored. In addition, pre- and post-treatment single word retrieval of verbs (The Northwestern Verb Production Battery (NVPB) (Thompson, 2002)) and nouns (The Boston Naming Test (Goodglass & Kaplan, 1983)) was examined as well as sentence production abilities in unrelated picture description (NVPB) and constrained connected speech tasks. All participants met treatment criteria and exhibited generalization to sentence production with sentences containing trained and semantically related untrained verbs. Participants 1, 2, and 3 exhibited improvements on all pre- and post-treatment measures, including connected speech. Participant 4 exhibited gains on multiple measures but did not show improvement in connected speech. These findings indicate that treatment aimed at strengthening the verb network results in improved word retrieval in naming and sentence production across multiple tasks. Theoretical and clinical implications regarding the impact of using VNeST on rehabilitation of sentence production deficits in aphasia are discussed. / text

In this thesis the researcher argues that churches in Africa are being planted rapidly but are not growing to maturity, which produces troubling consequences. The Baptist Union of Southern Africa (BUSA) is then given as a representative case study of church planting in Afiica, because from 1990 they have seen as many as 413 new churches started. Yet there is growing concern over the stability of many of these young churches and their leaders. Key leaders in the BUSA are calling for an analysis of the church planting and a greater emphasis on church strengthening and equipping. Next, the researcher lays the exegetical foundation for building mature churches, drawing from Acts and the Pauline epistles. In Acts, keys for the growth of the church are given. In Paul's writings, the researcher identifies the core principles and content used in establishing churches. Next come the field research findings that show the condition of churches and church planting in the BUSA The research was conducted through church leader surveys and key interviews, supplemented by observations of Christ Seminary faculty in their training of pastors from these churches. Some disturbing statistics and characteristics of these young churches emerge. The researcher then seeks to demonstrate how to analyse the health of churches and church planting in Africa by interacting with the field research in light of Scripture. An analysis is given of the strengths and weaknesses of the BUSA's younger churches, in the areas of their evangelism, their establishing of the members, and their entrusting of leadership. Cautions were given against unbiblical church growth trends. Finally, the researcher offers suggestions and strategies for building stronger churches in Africa. He states, "In order for the gospel to steadily advance through the BUSA or through any churches in Africa, mother churches and church planters must take responsibility for strengthening young churches until they have qualified elders and are mature, reproducing churches." / Thesis (Ph.D. (Pastoral))--North-West University, Potchefstroom Campus, 2004.

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