UBC Theses and Dissertations

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UBC Theses and Dissertations

Reliability of floors under impact vibration Gupta, Ashwani


Floor vibration is a serviceability limit state problem as opposed to limit state of collapse. People find excessive vibrations annoying and it leads to unacceptable floor performance. Improvements in design techniques and use of higher strength materials have made floors lighter and more sensitive to vibrations. The existing code" criteria for limiting floor deflection are not satisfactory as they do not relate to human perception of vibrations. A finite element computer program is developed for a rational analysis of floor vibrations due to human footfall impact. The approach followed in the solution is to use a Fourier series expansion of displacement functions along the span and a finite element approximation in the transverse direction. A time step analysis is followed to obtain the floor's dynamic response at any point on the floor due to footfall impact elsewhere. A sensitivity analysis is done to study the effect of various floor parameters on floor performance. A reliability study of floor performance as affected by variability of joist stiffness is made by simulation. Floors simulated by randomly selecting joists from a population are analyzed and vibration response ratings are obtained by relating the response to human perception criteria. The probability of people rating the floor as of a certain performance level is predicted. Based on the reliability analysis, allowable spans and allowable deflections for a certain level of floor performance and a target reliability are proposed.

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