Fatigue behaviour of a PET-Geogrid under cyclic loading

The lines of ‘damage-begin’ and ‘specimen-break’ for dynamic loading of a geogrid were determined in a series of laboratory testing. The cyclic load ratio was set to R = 0.5, loading frequency f = 10 Hz and f = 3 Hz. The test results show clearly that the chosen procedure for the determination and analysis of the beginning of damage and break is reproducible and allow for safe extrapolation for lower load levels. Furthermore the method chosen enables explicit decrease of the required testing time. The assumption of linear damage accumulation was examined in two-step-trials. The number of load cycles to ‘break’ evaluated in ‘one-step-tests’ compared with those of ‘two-step-loading’ are practically the same. The existence of ‘damage-lines’ for the examined geogrid under a dynamic pulsating load of 10 Hz and 3 Hz and a R-value of 0.5 could be verified. Damage of the specimens occurs only for load-cycles lying between the ‘damage-line’ and the ‘stress-cycle-diagram’ (‘Woehler-curve’). When it comes to dimensioning against ‘damage-beginning’ or ‘break’, higher loading frequencies present the critical case.