Systematic patterns and random fluctuations in time series of coefficients of friction measured on floor surfaces

Coefficients of friction were measured periodically over a period of 30 months on the surfaces of five types of floor coverings in a new sport complex. The resulting time series were analysed with regard to both systematic and random short- and long-term effects of wear and maintenance. For detailed information about the involved wear mechanisms, two test sites characterized by different levels of pedestrian traffic were investigated for each floor covering. The systematic trends observed in time series of mean coefficients of friction were consistent with measured surface roughness parameters and could be divided into three categories, depending on the predominant wear mechanisms: smoothing of rough surfaces was accompanied by average monthly reductions of 0.007-0.014 in the coefficients of friction, measured under wet conditions, while mechanical polishing combined with coating by care products caused average changes between 0.002 and 0.006 per month. Progressive scratching and roughening of an initially smooth floor surface continuously increased the measured coefficients of friction by 0.003 per month. The cumulative long-term effects of surface wear exceeded the random variations in time series of mean coefficients of friction, characterized by a repeatability standard deviation of 0.006 and a reproducibility standard deviation of 0.020, respectively. For one specific floor covering, seasonal variations with an amplitude of 0.015 were observed in the time series of measured coefficients of friction.