Confidence intervals of prediction and synthesis of prediction estimates for deformability of expanded polystyrene in long-term compression

The paper presents an experimental and numerical study of expanded polystyrene (EPS) with density ranging from 14.5 to 33 kg/m3, which was subjected to long-term compression of σc = 0.35σ10% to verify the suggested methods of predicting compressive strain development in EPS products. The total time of testing was 608 days. Interval prediction of creep strain development for the period of 50 years was made by extrapolation based on power and exponential regression equations applied to approximate creep formation. These equations were reduced to a linear form by using logarithms. An additional factor K, depending on the number of retrospective test results and non-dimensional intervals in the range of prediction is used for a linear trend to correct for the expansion of confidence interval due to discounting of prediction information. Predictions obtained by using power and exponential equations were synthesised and the results were discussed.