In terms of initial stiffness, specimen F2 was approximately six times higher than F1, thus implying an anticipated incipient yielding, which occurred at 0.75% drift cycles for lower actuator loads of about 270 kN (60.7 kip) as a consequence of major damage in the cladding system. The narrow thin-shaped cycles obtained in the case of specimen F1 are opposed to apparently more dissipative loops predicted for specimen F2. As in the case of specimen F1, energy dissipation estimates were conducted. Figure 17 shows both equivalent viscous damping and cumulative dissipated energy, respectively.Significantly higher values of ξ, ranging from pproximately 14% to 20%, were computed and much less decay was observed between the first and second cycles. A maximum decrease of 16%—three times lower than that obtained for specimen F1—was determined at 0.5% drift. Nevertheless, the cumulative dissipated energy roughly coincides if the last cycle is considered, thus revealing that the total energy absorption capabilities of
the two structures are fairly constant. In particular, 88.1 and 84.8 kN-m (65.0 and 62.5 kip ft) were obtained at failure for specimens F1 and F2, respectively. Neither specimen F1 nor F2 developed rationally controlled dissipation mechanisms because the equivalent viscous damping essentially decreased with increasing drift amplitudes. Therefore, when included in the lateral force-resisting system of the frame, the precast concrete cladding panels were observed to produce only a contraction of the hysteresis loops, largely decreasing the displacement capacity of the structure for roughly constant loads.