Louisiana Transportation Research Center, Baton Rouge, LA
A procedure for extrapolating creep strains to longer time intervals was developed. The procedure was based on applying time-shift factors to creep strain curves at elevated temperatures to establish a master strain curve for longer time intervals. The procedure was applied to creep test results on high density polyethylene (HDPE) geogrid tested at creep loads up to 40% of its maximum tensile strength Tmax and at temperatures up to 72°C (160°F). Temperature creep curves of 1000-h tests were shifted along the log-time scale to create 10 000-h master strain curves at each loading level. The established master curves were compared with experimental results of 10 000-h creep tests at room temperature and at the same loading levels. The shift factors were then applied to the creep curves to predict creep response for a duration of more than 100 000-h (about two cycles shift on the log-time scale from the initial 1000-h tests).
The analysis demonstrated the applicability of applying shift factors to elevated-temperature creep test results to predict the response at longer times for this type of geogrid. The analysis was applicable to creep loads up to 40% Tmax. The procedure, however, did not accurately estimate creep response at higher loading levels and temperatures where accelerated creep failure occurred.
Paper ID: GTJ10423J