This study has identified two types of friction, referred to as non-classical, that are found when dealing with vinyl flooring tiles that are not well represented by the classical definition. One type of non-classical friction has a coefficient of static friction, μs, which increases the longer the body is at rest relative to its base. The other type of friction has a kinetic coefficient of friction, μk, which increases the faster the unanchored body is moving relative to its base. Techniques were developed to quantify these behaviors so they could be modeled accurately for seismic analysis. The experimental reconciliation between the predicted and the measured displacement time-histories were very good for both varieties of non-classical friction and were generally less than 10% different under uniaxial seismic accelerations. For the velocity dependent variety of friction, biaxial test results which incorporate vertical acceleration were also good.
Using these test results, analytical studies were conducted to derive a procedure which could possibly be used for the sliding analysis of unanchored objects. Several observations can be made from the results. First, there is no relationship between the peak displacement and the distance to the seismic source. Second, there is little relationship between the local geology and the peak displacement. Third, the influence of vertical motion on peak displacement is very small. Thus the risk should also be largely independent of these variables. In this study, 215 biaxial earthquake time-history records were used as a population to statistically characterize the effects of different strength earthquakes on peak slip. Using hazard curves from several sites and fragility curves developed from this earthquake population, probability of failure charts were generated and comparisons between classical and non-classical friction were conducted. It was observed that non-classical systems consistently have a lower probability of failure than classical systems. The procedure developed here may be utilized in future studies to design safe perimeters around unanchored bodies in a statistically sound and rational manner which is consistent with modern design.
|School:||North Carolina State University|
|School Location:||United States -- North Carolina|
|Source:||DAI-B 70/10, Dissertation Abstracts International|
|Keywords:||Earthquakes, Friction, Sliding|
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