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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M.S.

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

Modern lightweight floor systems are susceptible to annoying vibrations induced by the forcing action of human locomotion. This investigation considered several experimental methods to reduce unwanted floor motion as well as analytical procedures aimed at a better understanding of the phenomenon. A series of test floors were designed and constructed expressly for vibration experiments. Various viscoelastic treatments and second mass damper devices were applied to each test floor and the resulting reduction of vibration tendency was measured. These results are compared and the best-performing treatments and devices are discussed and investigated in detail. The relationship of frequency ratios of structural components was investigated analytically and reasonable design precautions necessary to avoid beating vibrations are discussed. A mathematical model of the forcing function of human locomotion is presented, as well as its implications for statistically-based design criterion. Finally, recommendations for future research are discussed based on the experimental and analytical results of the investigation. / Master of Science

Several different aspects of floor vibrations were studied during this research. The focus of the research was on developing a computer modeling technique that will predict the fundamental frequency of vibration and the peak acceleration due to walking excitation as given in AISC Design Guide 11, Floor Vibrations Due to Human Activity (Murray, et al., 1997). For this research several test floors were constructed and tested, and this data was supplemented with test data from actual floors. A verification of the modeling techniques is presented first. Using classical results, an example from the Design Guide and the results of some previous research, the modeling techniques are shown to accurately predict the necessary results. Next the techniques were used on a series of floors and the results were compared to measured data and the predictions of the current design standard. Finally, conclusions are drawn concerning the success of the finite element modeling techniques, and recommendations for future research are discussed. In general, the finite element modeling techniques can reliably predict the fundamental frequency of a floor, but are unable to accurately predict the acceleration response of the floor to a given dynamic load. / Master of Science

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