The effectiveness of a new structural material, namely textilereinforced mortar (TRM), was investigated experimentally in this study as a means of confining old-type reinforced concrete columns with limited capacity due to bar buckling or due to bond failure at lap splice regions. Comparisons with equal stiffness and strength fiber-reinforced polymer (FRP) jackets allow for the evaluation of the effectiveness of TRM versus FRP. Tests were carried out on full scale non-seismically detailed RC columns subjected to cyclic uniaxial flexure under constant axial load. Thirteen cantilever-type specimens with either continuous longitudinal reinforcement (smooth or deformed) or lap splicing of longitudinal bars at the floor level were constructed and tested. Experimental results indicated that TRM jacketing is quite effective as a means of increasing the cyclic deformation capacity of old-type RC columns with poor detailing, by delaying bar buckling and by preventing splitting bond failures in columns with lap spliced bars. Compared with their FRP counterparts, TRM jackets used in this study were found to be equally effective in terms of increasing both the strength and deformation capacity of the retrofitted columns. From the response of specimens tested in this study, it can be concluded that TRM jacketing is an extremely promising solution for the confinement of reinforced concrete columns, including poorly detailed ones with or without lap splices in seismic regions.

published_or_final_version / Architecture / Master / Master of Landscape Architecture

Regulatory T cells represent a specialized subpopulation of T lymphocytes that may modulate spontaneous HIV-1 disease progression by suppressing immune activation or inhibiting antiviral T cell immune responses. While effects of classical \(CD25^{hi}FoxP3^+CD4^+\) regulatory T cells during HIV-1 infection have been analyzed in a series of recent investigations, very little is known about the role of non-classical regulatory T cells that do not express intracellular FoxP3. Here I evaluated two groups of non-classical Treg cells. One is phenotypically identified by the surface expression of HLA-G, an HLA class Ib molecule. The other Treg cell population is characterized by the surface expression of latency-associated peptide (LAP), a membrane-bound form of \(TGF-\beta\). Both HLA-G and LAP-expressing T cells are present in small proportions in peripheral blood of healthy individuals. I performed a systematic study on the phenotypic and functional profile of HLAG- and LAP- expressing regulatory T (Treg) cells in patients with different stages of HIV-1 infection. I found that HLA-G-expressing Treg cells were highly susceptible to HIV-1 infection, and were significantly reduced in individuals with progressive HIV-1 disease courses. Moreover, the proportion of \(HLA-G^+\) CD4 and CD8 T cells was positively correlated with CD4 T cell count and inversely correlated with markers of HIV-1 associated immune activation. Mechanistically, this correlation corresponded to a substantially increased ability of \(HLA-G^+\) Treg cells to inhibit bystander immune activation, while only minimally affecting functional properties of HIV-1-specific T cells. In contrast, no significant change in \(LAP^+\) Treg cell frequencies was found in progressive HIV-1 infection, and these frequencies were not correlated with immune activation. This observation was consistent with functional analysis, which indicated that \(LAP^+\) Treg cells did not suppress bystander activation. These investigations indicate an important role of \(HLA-G^+\) Treg cells for balancing bystander immune activation and anti-viral immune activity in HIV-1 infection, and suggest that the loss of these cells during advanced HIV-1 infection may contribute to immune dysregulation and HIV-1 disease progression. In the meantime, \(LAP^+\) Treg cells do not appear to play an important role in determining HIV-1 disease outcome.

Design of autoclaved aerated concrete (AAC) masonry in the United States is currently based on Appendix A of the 2008 Masonry Standards Joint Committee (MSJC) Code. Those provisions include the design of lap splices, and equations for the nominal capacity in interface shear transfer between grout and AAC. The provisions for lap splices are an extension of the provisions for concrete or clay masonry, modified to neglect the contribution of AAC to splice capacity. This thesis describes a testing program aimed at verifying the current provisions using tests of lap splices in grouted AAC masonry. Based on the results of those tests, the provisions are shown to be appropriate. The provisions on interface shear transfer between grout and AAC require that the transferred shear be checked against a nominal capacity based on limited test results. This thesis describes a testing program aimed at verifying and refining this nominal capacity using pullout tests of grout cores in AAC masonry units. Based on the results of those tests, the currently used nominal capacity is shown to be conservative, and a recommendation is made to increase it. / text

published_or_final_version / Architecture / Master / Master of Landscape Architecture

Precision optics can be accurately fabricated by computer controlled optical surfacing (CCOS) that uses well characterized polishing tools driven by numerically controlled machines. The CCOS process is optimized to vary the dwell time of the tool on the workpiece according to the desired removal and the calibrated tool influence function (TIF), which is the shape of the wear function by the tool. This study investigates four major topics to improve current CCOS processes, and provides new solutions and approaches for the next generation CCOS processes.The first topic is to develop a tool for highly aspheric optics fabrication. Both the TIF stability and surface finish rely on the tool maintaining intimate contact with the workpiece. Rigid tools smooth the surface, but do not maintain intimate contacts for aspheric surfaces. Flexible tools conform to the surface, but lack smoothing. A rigid conformal (RC) lap using a visco-elastic non-Newtonian medium was developed. It conforms to the aspheric shape, yet maintains stability to provide natural smoothing.The second topic is a smoothing model for the RC lap. The smoothing naturally removes mid-to-high frequency errors while a large tool runs over the workpiece to remove low frequency errors efficiently. The CCOS process convergence rate can be significantly improved by predicting the smoothing effects. A parametric smoothing model was introduced and verified.The third topic is establishing a TIF model to represent measured TIFs. While the linear Preston's model works for most cases, non-linear removal behavior as the tool overhangs the workpiece edge introduces a difficulty in modeling. A parametric model for the edge TIFs was introduced and demonstrated. Various TIFs based on the model are provided as a library.The last topic is an enhanced process optimization technique. A non-sequential optimization technique using multiple TIFs was developed. Operating a CCOS with a small and well characterized TIF achieves excellent performance, but takes a long time. Sequential polishing runs using large and small tools can reduce this polishing time. The non-sequential approach performs multiple dwell time optimizations for the entire CCOS runs simultaneously. The actual runs will be sequential, but the optimization is comprehensive.

The effects of high loading rates (HLR), and nano reinforcement on the mechanical response of adhesively-bonded SLJs with composite adherends, subjected to different loading (strain) rates are systematically investigated. The results are then compared to those of neat thermoset resin and thermo-plastic adhesive. More specifically, nano-reinforced and neat resin bonded joints mating carbon/epoxy and glass/epoxy adherends were subjected to tensile loadings under 1.5 and 3 mm/min and tensile impacts at a loading rate of 2.04E+5 mm/min. In some cases, additional tests were conducted under 15, 150, and 1500 mm/min to obtain additional properties gained using the nano-reinforcements for use in the further numerical investigations. The HLR tests were conducted, using a modified instrumented pendulum equipped with a specially designed impact load transfer apparatus. The dispersion of nanoparticles was facilitated using a mechanical stirrer and a three-roll mill machine. The failure mechanisms were studied with a scanning electron microscope.

A previously completed study in the field of concrete block construction by Ahmed and Feldman (2012) indicated that, on average, the reinforcing bars in non-contact lap splices, where the lapped bars are located in adjacent cells, only develop 71% of the tensile resistance of spliced bars which are in contact. An experimental program was therefore initiated to design and evaluate remedial measures which can potentially increase the tensile resistance of non-contact lap splices to that of contact lap splice of the same lap length. Implementation of the proposed measures in various field situations was also analyzed. Six unique remedial splice details, along with standard contact and unaltered non-contact lap splices were evaluated and compared. The mitigative details included providing additional confinement, installing knock-out webs, placing splice reinforcement between the lapped bars, and combinations of these aforementioned details. Three replicates of each splice detail were constructed for a total of 24 wall splice specimens. Each wall splice specimen was reinforced with No. 15 Grade 400 deformed steel reinforcing bars with 200 mm lap splice lengths at located the midspan. The specimens were tested in a horizontal position under a monotonic, four-point loading geometry. Load and deflection data were collected throughout testing and were subsequently used in an iterative moment-curvature analysis to calculate the maximum tensile resistance of the spliced reinforcement. This was then used to compare the structural performance of each remedial splice detail to the standard contact and non-contact lap splices. The wall splice specimens which contained non-contact lap splices with knock-out webs, s-shaped, and transverse reinforcement in the splice region achieved similar tensile capacities as the wall splice specimens with standard contact lap splices. Industry professionals have indicated that the installation of the remedial measures evaluated in this study would not affect the constructability of masonry assemblages in field situations. The splice detail with knock-out webs confined within the lap splice length was determined to be the most viable procedure as it can be installed to increase the resistance of non-contact lap splices in almost all construction situations. This remedial procedure was able to improve the tensile resistance of the lapped reinforcement by 63% compared to the wall splice specimens with standard non-contact lap splices.

Thesis (M.Sc.)--Acadia University, 1998. / Includes bibliographical references. (leaves 98-99). Also available on the Internet via the World Wide Web.

Adhesive bonding of graphite epoxy composite laminates to itself or traditional metal alloys in modern aerospace and aircraft structural applications offers an excellent opportunity to use the most efficient and intelligent combination of materials available thus providing an attractive package for efficient structural designs. However, one of the major issues of adhesive bonding is the occasional formation of interfacial defects such as kissing or weak bonds in the bondline interface. Also, there are shortcomings of existing non-destructive evaluation (NDE) methods to non-destructively detect/characterize these interfacial defects and reliably predicting the bond shear strength. As a result, adhesive bonding technology is still not solely implemented in primary structures of an aircraft. Therefore, there is a greater demand for a novel NDE tool that can meet the existing aerospace requirement for adhesive bondline characterization. This research implemented a novel Acoustography ultrasonic imaging and digital image correlation (DIC) technique to detect and characterize interfacial defects in the bondline and determine bond shear strength in adhesively bonded composite-metal joints. Adhesively bonded Carbon Fiber Reinforced Plastic (CFRP) laminate and 2024-T3 Aluminum single lap shear panels subjected to various implanted kissing/weak bond defects were the primary focus of this study. Kissing/weak bonds were prepared by controlled surface contamination in the composite bonding surface and also by improperly mixing the adhesive constituent. SEM analyses were also conducted to understand the surface morphology of substrates and their interaction with the contaminants. Morphological changes were observed in the microscopic scale and the chemical analysis confirmed the stability of the contaminant at or very close to the interface. In addition, it was also demonstrated that contaminants migrated during the curing of the adhesive from CFRP substrate which caused a decrease of bond shear strength in single lap shear test samples. Through-transmission ultrasonics (TTU) Acoustography at 3.8 MHz showed promising results on the detectability of bondline defects in adhesively bonded CFRP-Al lap shear test samples. A correlation between Acoustography ultrasonic attenuation and average bond shear strength in CFRP-Al lap shear panels demonstrated that differential attenuation increased with the reduction of the bond shear strength. Similarly, optical DIC tests were conducted to identify and quantify kissing bond defects in CFRP-Al single lap shear joints. DIC results demonstrated changes in the normal strain (εyy) contour map of the contaminated specimens at relatively lower load levels (15% ~ 30% of failure loads). Kissing bond regions were characterized by negative strains, and these were attributed to high compressive bending strains and the localized disbonding taking placed at the bondline interface as a result of the load application. It was also observed that contaminated samples suffered from more compressive strains (εyy) compared to the baseline sample along the loading direction and they suffered from less compressive strains (εxx) compared to the baseline sample perpendicular to the loading direction. This demonstrated the adverse effect of the kissing bond on the adhesive joint integrity. This was a very significant finding for the reason that hybrid ultrasonic DIC is being developed as a faster, more efficient, and more reliable NDE technique for determining bond quality and predicting bond shear strength in adhesively bonded structures.