Over the last decade it has become increasingly popular to provide large public areas with gracefully designed 'flexible' staircases. One inherent characteristic of this type of construction is a low stiffness to mass ratio and hence a low natural frequency when compared to more traditional designs. A number of staircases have been found to be dynamically responsive to pedestrian traffic resulting in costly repairs. The objective of this thesis was to investigate the differences between human induced loading on floors with that on stairs. Experimental work carried out on a purpose built staircase showed that forces up to 3 times the static body weight were generated during fast descents while forces up to 2.5 times the static body weight were generated during fast ascents. The work also showed that first harmonic values generated while ascending were slightly higher than for descending whilst second harmonic values were up to 3 times greater for fast descents than for fast ascents. When compared with floor testing, stair testing produced first harmonic values nearly 2.5 times greater with second, third and fourth harmonic values nearly 3 times greater. The harmonic results for the flat testing were also incorporated into a new mathematical expression to predict peak accelerations on simply supported floors and footbridges. The experimental results were duplicated analytically by developing a computer program to calculate the vertical ground reaction forces from body segment positional data. Following a Newtonian approach, the predicted first harmonic values were 20% to 30% lower than actual while the second harmonic values were approximately the same. Monte Carlo simulation techniques were also used to model the effects of group loading on stairs. The simulations predicted enhancement factors (a multiplier on single subject loading) of 3 to 6 for smaller groups(< 9 people) and 4 for larger groups(> 25 people). If the experimental/analytical results are combined with the group loading predictions, the harmonic values for groups ascending or descending flexible staircase could be substantially increased. These results demonstrate that loading data from floors is highly inappropriate for staircase design.

Thesis (M.S.)--West Virginia University, 2006. / Title from document title page. Document formatted into pages; contains vi, 76 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 60-61).

M.Ing. (Civil Engineering) / Please refer to full text to view abstract

QC 20110620

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The search for a better method of analyzing skew arches and rigid frames has gone on for years. During that time many theories were presented, most of which were an improvement or a simplification of previous methods. However, no exact analytical solution, based on classical plate theory, for the analysis of skewed plates as found in rigid-frame bridges had been developed prior to this thesis. As previously mentioned, the complete solution is being presented in three separate theses. This thesis contains all the equations needed for the analysis that arise from considering the extensional forces acting in the skewed slab. All the equations have been given in the form of an infinite series. These equations, together with the ones for the other parts of this problem, must be expanded for a few terms, combined and solved. Due to the size and number of equations involved, the only practical solution would involve the use of a modern high-speed computer. Since Virginia Polytechnic Institute has a computer of this type, the entire analysis could he completed at the college. Once the results are obtained, a comparison can be made with the experimental analysis referred to in the thesis. / Master of Science

The focus of this research was primarily on corrosion of the reinforcing steel (rebars) in bridge decks. It has been estimated that over $20 billion is required to repair or rehabilitate corrosion induced deficient bridge decks and that the cost is rising at the rate of $0.5 billion annually. Corrosion occurs when there is a sufficiently high concentration of chloride ions at the top rebar mat. The principal source of chloride ions is from the deicing salts applied on the decks during winter. More than 9 million tons of deicing salts are consumed each year in the U.S.A. As corrosion products have a larger volume than steel, corrosion causes cracking and spalling of the deck. Concrete laboratory specimens with rebars were cast and subjected to a chloride environment. The corrosion potential and rate were monitored with Cu-CuSO₄ half-cell and the 3LP device, respectively. When active corrosion had been initiated, the specimens were treated in six ways, one being the 'control'. Two overlay types and polymer impregnation were used in all combinations as treatment methods. The specimens which were impregnated were grooved and dried to 230 °F prior to impregnation and polymerization. The post-treatment corrosion rates were appreciably reduced. Mortar cubes were made, dried to different temperatures between room temperature and 600 °F, impregnated and polymerized. The cubes were then vacuum saturated and their resistivity obtained. They were then cut, dried to 220 °F and the effects of drying temperature was evaluated using a Mercury Porosimeter and a Scanning Electron Microscope. The cubes were subjected to a chloride environment and subsequent chloride content was determined. The results suggested that a lower drying temperature was sufficient for effective impregnation. Other laboratory specimens were dried to 150 °F and 180 °F and impregnated as before. The post treatment corrosion rates supported the conclusions determined in the cube study. / Master of Science

This thesis describes the effects of coefficient of variation (COV) of joist modulus of elasticity (MOE), floor mass and stiffness, imposed load, and boundary conditions on the floor vibrational performance. Three main parameters used to describe the vibration are resonant frequency, damping ratio, and root mean square (RMS) acceleration. The results showed that COV of joist MOE affected the fundamental frequency, and had no significant effect on damping ratio and RMS acceleration. The floor mass and stiffness affected all the three parameters to different degrees. Imposed load affected most of the vibrational parameters. The boundary conditions investigated affect the mode 2 resonant frequency, but have no significant effect on the damping ratio and RMS acceleration. In addition, the load sharing capacity was evaluated in terms of the percentage of load carried by each joist within a floor. / Master of Science

A lightweight floor system consisting of a concrete slab on steel joists or beams is susceptible to annoying vibrations caused by walking. This investigation considers a criterion developed by Allen (1991) that indicates whether a proposed structural floor system is acceptable for walking vibrations. The proposed vibration criterion is evaluated using the Murray vibration criterion as a basis for comparison. Both criteria are used to determine the acceptability of existing office floors, shopping malls, and pedestrian bridges. The evaluation results for each criteria are compared and the strengths and weaknesses of both criteria are discussed in detail. A derivation is presented for the proposed criterion and the calculations involved in utilizing the criterion are described. Finally, recommendations for future research are discussed based on the evaluation results of the investigation. / Master of Science

M.S.