Fig. 13.
Panel a shows normalised secant stiffness K n over K 1 against number of cycles for present study C 4. Number of cycles ranges from 1 to 10000 and stiffness ranges from 1.0 to 2.0. Present study values increase gradually from about 1.0 at 1 cycle to about 1.7 near 10000 cycles. Equation 10 increases from 1.0 to about 1.65. Klinkvort and Hededal 2013 increases gradually to about 1.4, while Li et al. 2022 increases to about 1.5. Panel b shows normalised secant stiffness K n over K 1 against number of cycles for present study C 22. Number of cycles ranges from 1 to 100000 and stiffness ranges from 1.0 to 4.6. Present study values increase from about 1.0 at 1 cycle to about 2.7 near 100000 cycles. Equation 10 increases to about 2.7, Klinkvort and Hededal 2013 increases gradually to about 1.7, and Li et al. 2022 rises sharply to above 4.5 near 100000 cycles.Normalised secant stiffness (Kn/K1) data for tests C4 and C22 compared to equation (10) with cyclic load magnitude: (a) ζb = 0·5 and (b) ζb = 0·9