In recent years, a modified method to strengthen reinforced concrete (RC) structures has emerged involving application of fibre reinforced polymers (FRPs) in the ‘near surface’ of a member. The near surface mounted (NSM) method entails placing a pre-cured FRP bar, rod, strip, or plate, along with an adhesive into a pre-cut groove or slot in the cover of a member. Advantages of the NSM technique over externally bonded (EB) systems include minimal surface preparation and installation time, the ability to anchor the FRP into an adjacent member, superior protection from mechanical and environmental damage, and superior bond properties. Although a number of laboratory studies, field applications, and experimental field projects have employed the NSM FRP strengthening technique, none of these have been performed in a climate where cold environments and freeze-thaw cycling could cause adverse effects. This thesis presents the results of an experimental program to investigate the flexural and bond performance and freeze-thaw durability of a specific NSM carbon/vinylester FRP tape strengthening system through a series of tests on strengthened slab strips and a series of pull-out bond tests. The effects of adhesive type (cementitious or epoxy) and exposure condition (room temperature, freeze-thaw, sustained load, or freeze-thaw under sustained load) are examined. The results indicate no discernable negative impacts on the performance of the grout strengthened members after exposure to freeze-thaw cycles and/or sustained load. The slab strips strengthened with epoxy adhesive displayed minor changes in ultimate load (less than three percent) after exposure to freeze-thaw cycles or a period of sustained load, while the combined effect of freeze-thaw cycles and sustained load produced an average reduction in ultimate load of eight percent. The epoxy adhesive strengthened pull-out bond tests experienced a 27% average drop in ultimate load after 150 freeze-thaw cycles. These results suggest that additional research on the combined effects of sustained load and freeze-thaw cycling are warranted, particularly for NSM strengthening applications using epoxy adhesives. / Thesis (Master, Civil Engineering) -- Queen's University, 2010-04-30 18:11:56.424

Thesis (Ph. D.)--Ohio State University, 2006. / Available online via OhioLINK's ETD Center; full text release delayed at author's request until 2007 Mar 24

Indivíduos com Síndrome do Impacto apresentam alterações nos movimentos da escápula em relação ao tórax como uma diminuição da rotação superior, inclinação posterior e aumento da rotação medial, que associada a diminuição do controle e do recrutamento da musculatura estabilizadora podem causar pinçamento dos tecidos moles. O objetivo deste estudo foi determinar o efeito de um protocolo de fortalecimento com carga e complexidade progressivas e aumento da percepção cinestésica na cinemática escapular de indivíduos com síndrome do impacto, enfatizando os músculos serrátil anterior, romboides e porções superior, média e inferior do trapézio. Vinte e cinco indivíduos com diagnóstico da síndrome foram submetidos ao programa de fortalecimento muscular e aumento do controle motor que teve duração de oito semanas, realizados três vezes por semana. O sistema eletromagnético de aquisição de dados foi utilizado para avaliar a cinemática em três planos antes e após o protocolo. A dor e a função do ombro foram avaliadas pelo Shoulder Pain and Disability Index (SPADI-Brasil). O modelo linear de efeitos mistos foi utilizado para as comparações. A escápula apresentou alterações pós-intervenção com redução da rotação interna no repouso, plano sagital e frontal, diminuição da inclinação anterior nos três planos e redução da rotação superior no plano frontal e escapular . Houve diminuição da dor e melhora da função avaliada pelo SPADI-Br. O protocolo de controle motor e fortalecimento muscular altera a cinemática da articulação escapulotorácica e gera diminuição da dor e melhora da qualidade de vida. / Patients with subacromial impingement syndrome have changes in the scapula relative to the thorax movements with decreased upward rotation, posterior tilt and increased medial rotation that if associated with control and recruitment of stabilizer muscles decrease, could result on soft tissues impingement. The aim of this study is to determine the effect of a strengthening and kinesthetic awareness protocol with progressive and complexity load in scapular kinematics of individuals with impingement syndrome, emphasizing the serratus anterior, rhomboids and upper, middle and lower trapezius. Twenty-five diagnosed patients with the syndrome did undergo to the muscle strengthening and increased motor control program during eight weeks, three times a week. The electromagnetic data acquisition system was used to evaluate the kinematic at three planes before and after the protocol. The shoulder pain and function were evaluated by Shoulder Pain and Disability Index (SPADI-Brazil). The linear mixed-effects model was used for comparisons pre- and post-intervention. The scapula showed post-intervention changes with reduced internal rotation at rest, sagittal and frontal plane, decreased anterior tilt in three planes and reducing the upward rotation on the frontal and the scapular planes, decreased pain and improvement in function assessed by SPADI-Br. The motor control and strengthening protocol changes the kinematics scapulothoracic joint and results in decreased pain and improved quality of life.

Master of Science / Department of Civil Engineering / Hayder A. Rasheed / There is a high need to repair or replace many bridges in the state of Kansas. 23% of the bridges in Kansas are labeled structurally deficient or functionally obsolete. A majority of these bridges serve rural areas and are damaged due to overloading during harvest season. A state-of-the-art method of performing structural health monitoring on these bridges followed by an effective method of strengthening and repair was researched and presented in this thesis. The first phase of this research involved researching multiple devices to be used for state-of-the-art health monitoring. After deciding on an appropriate system, multiple tests were performed to determine the systems performance compared against conventional systems. The system was tested on a laboratory scale pre-stressed concrete T-beam. The system was tested on its ability to effectively record and transmit acceleration data. If this system were to be implemented on an actual bridge, KDOT could make a decision to repair or strengthen the bridge based on the results. The next phase of the research was to determine an effective strengthening procedure using carbon fiber reinforced polymer (CFRP). Reinforced concrete beam specimens were cast and tested in the lab. The specimens consisted of rectangular and T-shaped cross-sections to create different failure modes when tested in bending. The primary issue when strengthening with CFRP is the issue of early separation failure when using CFRP in the longitudinal direction only. In an effort to prove this, the specimens were strengthened with five layers of CFRP and tested in four-point bending until failure. In an effort to prevent early separation failure, CFRP “U-wraps” were applied to provide shear resistance and additional anchorage for the flexural CFRP. The beams were then tested in flexure until failure by FRP rupture or concrete crushing followed by FRP rupture. The test results indicate that the U-wraps allowed the FRP to reach full capacity and fail in FRP rupture. The use of CFRP provided a strength increase of about 220% over the control beam specimens while significantly reducing the ultimate deflection.

No description available.

Ein Ziel des Sonderforschungsbereiches 528 war, das Verbundsystem auf allen Skalenebenen so präzise beschreiben zu können, dass eine hinreichende Genauigkeit bei der Berechnung des Tragverhaltens von Stahlbetonbauteilen mit Textilbetonverstärkung nicht nur bei der Nachrechnung, sondern auch bei der Prognose erreicht wird. Die Vorhersagequalität von Tragfähigkeiten für die Biege-, Querkraft- und Normalkraftverstärkung wurde mit Hilfe von Großversuchen nachgewiesen, deren Ergebnisse vor der Berechnung nicht bekannt waren. Anhand der bereitgestellten Materialparameter und Geometriedaten wurde in den numerischen Teilprojekten sowie in einem experimentell orientierten Teilprojekt das Tragverhalten prognostiziert. Danach wurden die Versuche durchgeführt. Die prognostizierten Traglasten wurden durch die Experimente bestätigt. Der vorliegende Beitrag fokussiert auf die Querkraftverstärkung, da eine detaillierte Beschreibung aller Versuche den Rahmen sprengen würde. / One aim of the developments in the SFB 528 was the description of the compound system as precisely as possible at all scale levels that an adequate precision is not achieved by reinforced concrete components at the calculation of the load carrying behaviour with TRC reinforcements only at the historical calculation but also at the forecast. The forecast quality of load-capacities for the bend, shear and normal force strengthenings was proved with the help of large-scale experiments whose results were not confessed before the calculation. With the provided material parameters and geometry data the load carrying behaviour was forecast in the numeric subprojects as well as in an experimentally oriented subproject. After that the tests were carried out. The forecast loads were confirmed by the experiments. The paper on hand focuses on the shear strengthening since a detailed description of all tests would go beyond the scope.

No

No description available.

Rare-earth oxides used in oxide dispersion strengthening are known to provide excellent strength and deformability over ordinary dispersion strengthening. It has been suggested that this may be due to the development of molybdate compounds instead of pure dispersed oxide particles. These alloys are produced by dispersing particles of certain rare-earth oxides in a molybdenum matrix and forming the mixture into a composite ingot. During the high-temperature consolidation process, the oxides are converted into rare-earth molybdates. With subsequent processing, these molybdate phases undergo deformation to form high-surface-area ribbons that serve to inhibit dislocation movement, thus improving the mechanical properties of the molybdenum matrix. It is still unknown what specific compounds, phases, and crystal structures provide these metal-oxides with their high strength and deformability. Because the molybdate phases are formed at high temperatures and low oxygen partial pressures, little is also known of the high-temperature phase equilibria of the REO-Mo systems under these conditions. The primary goal of this study was to deifine phase equilibria on systems of Mo with rare-earth oxides. The project aimed to identify compounds, phases, and specific oxidation states of molybdenum at various processing conditions. Systems of LaO1.5-MoOx, YO1.5-MoOx, and ZrO2- MoOx were investigated at temperatures of 1000??nd 1200??and O2 partial pressures ranging from 10-4 Pa to 10-13 Pa. Samples were prepared using powder starting materials of Mo and rare-earth oxides were combined in stoichiometric ratios. The samples were then electrically heated in a ceramic tube furnace in which the oxygen partial pressure was controlled by means of a combined flow of H2 and CO2 gas. Characterization was performed using x-ray diffraction, with published powder diffraction files for phase identification.

There is a large building stock in seismic regions of Turkey that require seismic upgrades. In order to minimize the disturbance to occupants and not to intervene with the functioning of the building, external strengthening methods can be preferred among different alternatives. This study reports the experimental findings on the upgrading of deficient reinforced concrete frames with external installed structural components. Specimens strengthened with an externally reinforced concrete shear wall, external steel frames, steel plate shear wall and one as-built reference 1/3-scale portal frame specimens were tested under constant gravity load and increasing cyclic displacement excursions. The RC frames had deficiencies those mimic the existing deficient building stock in Turkey. The test results showed that the external upgrading can increase both the lateral stiffness and strength of deficient RC frames considerably. Finite element analyses were conducted to specimen models to investigate the behaviors numerically. Furthermore, corresponding single degree of freedom (SDOF) models of specimens were generated to perform dynamic analysis. Results show the importance of hysteretic response and enhancement of energy dissipation capability with drift control.