Over the life span of a structure it may become necessary to retrofit, or strengthen certain components or elements. This may be due to construction errors, changes in use and occupancy, or changes due to material deterioration or damage. Slab-column connections in flat slab structures might need to be strengthened for punching shear. Using steel shear bolts to strengthen connections for punching shear is a new technique used for retrofit that was developed at the University of Waterloo. If the retrofitted part of the structure is exposed to the atmosphere, or to chemicals such as deicing salts, the steel can corrode, thus furthering to damage the structure. Non-corrosive materials that can replace the steel shear bolts can be a good practical alternative to steel. Reported in this thesis are the results of research on the development and use of non-corrosive shear bolts for reinforced concrete interior slab-column connections. Externally applied shear reinforcing bolts provide the punching shear reinforcement strength, while allowing the flexibility and ease of installation of an external application after construction. By providing a bearing area against both sides of the slab surface, the formation of punching shear cracks can be restrained, and the connection can become strengthened against punching shear failure. Three different types of non-corrosive shear bolts were developed and tested. The first was an off-the-shelf glass fiber reinforced polymer (GFRP) bolt / nut product. The two others used two different GFRP core rods with aluminum fittings crimped to their ends. A total of six specimens were tested, four were tested under an increasing static load, while two were tested with an unbalanced pseudo-dynamic lateral load. All six specimens were designed to fail in punching shear before reaching their flexural capacity. The results are compared against previous test results of specimens both unreinforced and reinforced with steel shear bolts to determine their effectiveness. From the test results it was found that the GFRP shear bolts did strengthen the connections for punching shear. The GFRP nut and bolt did not strengthen the connection, and, in fact, decreased its overall strength when compared to the unreinforced specimen. The presence of the GFRP shear bolts also increased the connection ductility and the deflection capability. In the pseudo-dynamic tests the GFRP shear bolts significantly increased the amount of energy dissipated by the connection under reverse cyclic loading. The results of the testing appeared to be depended on the proper application of the crimping technique to place the bolts in the slab.

No description available.

Double-nut anchor bolt systems are used in the erection of traffic signal poles, high-mast luminaries, and other highway appurtenances. An absence of a tightening standard for such systems decreases the confidence in their performance under fatigue loading. Past research has shown that a tightening standard should include the development of preload in the anchor bolt sufficient to provide adequate resistance to fatigue failure. Preload should be measured by a turn-of-the-nut method. Laboratory progressive tightening tests were performed in order to monitor the stress ranges occurring in the bolt at various locations of interest at various degrees of turn-of-the-nut tightness. Tests were performed on six diameters of anchor bolt ranging from 1 to 2-1/4 inches in diameter and two different categories of thread pitch: UNC and 8UN. Plots of stress range versus degree of tightness were developed for each test and evaluated to find the minimum degree of turn-of-the-nut at which stress range inside the nuts dropped below that outside the nuts. This shift was considered to be the principle theoretical indication of adequate performance. A fatigue test which saw failure outside the double-nut connection was set down as the practical indicator of adequate fatigue performance. The 2 inch 8UN bolt was chosen as the critical specimen due to its overall low generation of preload during tightening tests. Theoretical testing showed that 1/24 turn-of-the-nut would guarantee sufficient fatigue performance. Two practical fatigue tests of the bolt at that tightness saw one positive and one negative failure. After actual lab tests, finite element modeling was used to investigate the behavior of the bolt. It was found that performance did not see improvement until 1/12 turn-of-the-nut. After all results were considered, a standard of 1/6 turn-of-the-nut or refusal of tightening by specified methods was recommended, provided a minimum of 1/12 turn-of-the-nut was achieved. This value allows for ease of measurement, sufficient tightness, degree of safety, and has been shown in past testing not to cause failure through over-tightening. However, tightening to only 1/12 turn-of-the-nut still provided adequate performance.

No description available.

Thesis (Ph. D.)--University of Nevada, Reno, 2008. / "May, 2008." Includes bibliographical references (leaves 136-142). Online version available on the World Wide Web.

Thesis (Ph. D.)--University of Nevada, Reno, 2006. / "December, 2006." Includes bibliographical references. Online version available on the World Wide Web.

The mining industry is a major consumer of rock bolts in the United States. Due to the high humidity in the underground mining environment, the rock bolts corrode and loose their load bearing capacity which in turn reduces the life expectancy of the ground support and, thus, creates operational difficulties and number of safety concerns [1]. Research on rock anchor corrosion has not been adequately extensive in the past and the effects of several factors in the mine atmosphere and waters are not clearly understood. One of the probable reasons for this lack of research may be attributed to the time required for gathering meaningful data that makes the study of corrosion quite challenging. In this particular work underground water samples from different mines in the Illinois coal basin were collected and the major chemical content was analyzed and used for the laboratory testing. The corrosion performance of the different commercial rock anchors was investigated by techniques such as laboratory immersion tests in five different corrosion chambers, and potentiodynamic polarization tests in simulated ground waters based on the Illinois coal basin. The experiments were conducted with simulate underground mining conditions (corrosive). The tensile strengths were measured for the selected rock anchors taken every 3 months from the salt spray corrosion chambers maintained at different pH values and temperatures. The corrosion potential (Ecorr), corrosion current (Icorr) and the corresponding corrosion rates (CR) of the selected commercial rock bolts: #5, #6, #6 epoxy coated and #7 forged head rebar steels, #6 and #7 threaded head rebar steels were measured at the solution pH values of 5 and 8 at room temperature. The open circuit potential (OCP) values of the different rock anchors were recorded in 3 selected underground coal mines (A, B & C) in the Illinois coal basin and the data compared with the laboratory electrochemical tests for analyzing the life of the rock anchors installed in the mines with respect to corrosion potential and corrosion current measured. The results of this research were statistically validated. This research will have direct consequence to the rock related safety. The results of this research indicate that certain corrosive conditions are commonly found in mines but uniform corrosion (around 0.01-0.03mm loss per year across the diameter) is generally not considered a serious issue. From this study, longer term research for long-term excavation support is recommended that could quantify the problem depending on the rock anchor used and specific strata conditions.

Um dos tipos de ligação mais comum em estruturas de madeira é aquele feito por meio de parafusos solicitados transversalmente (pino metálico). A revisão da ABNT NBR:7190 de 1997, que introduziu os conceitos do Método dos Estados Limites, apresentou alteração nos critérios de dimensionamento dessas ligações, levando a resultados diferentes em relação à norma anterior, de 1982, de acordo com o meio técnico-científico. Nesse contexto, o objetivo deste trabalho foi realizar uma comparação dos critérios de dimensionamento das normas ABNT NBR:7190, versões 1997 e 1982, com as normas EUROCODE 5: 2004, LRFD: 1996, AS: 1994, que possuem grande tradição na utilização de estruturas de madeira. Após a realização da comparação teórica entre os critérios, foi realizada experimentação em modelos de ligação, para a situação com maior divergência. Para pequenas relações entre a espessura da peça de madeira e o diâmetro do pino, os resultados obtidos na comparação teórica indicaram que os valores de resistência calculados pela ABNT NBR7190: 1997 são inferiores aos calculados pelas outras normas, enquanto que, para valores elevados dessa relação e com madeira de maior resistência, os valores obtidos pela norma brasileira podem ser superiores. / Bolts laterally loaded (metal dowel-type) are the most commonly used connectors in timber structures. The review of the NBR: 7190 1997 standard that introduced the concepts of the states limit method showed changes in design criteria of bolts, reaching different results compared to the previous standard, 1982, according to the scientific technician staff. In this context, the aim of this study was to compare the design criteria of NBR standards: 7190, versions 1997 and 1982, and standards of other countries with great tradition in the use of timber structures. After the theoretical comparison of the criteria, an experimental evaluation in connections was done considering the case with greater divergence. For small relationships between the thickness of the timber member and the bolt diameter, theoretical results indicated that the strength values calculated by ABNT NBR7190: 1997 are lower than those calculated by other standards, while for high values of this relationship and wood of higher strength classes, the values obtained by Brazilian standards may be higher.

No description available.

No description available.