The RC frame (named onwards as \"bare frame \")was subjected to aseries of excitations as follows : white noise (to determine the natural frequencies of vibration of the newly cast concrete frame ). followed by four uniaxial seismic excitations ,applied in the X direction ,of maximum accelerations 0.10 g. 0.20 g, 0.30 g and 0.40 g. The natural frequencies of the bare frame obtained from the experimental testing ,corresponding to the first two modes of vibration ,are shown in Table l. Table 1. Experimental natural frequencies of vibration of the bare frame :ollowing the application of the four seismic excitations .the frame suffered an important level of damage which required strengthening .The selected strengthening technique was the confinement using Carbon Fibre Reinforced Polymers (CFRP },as shown in Figure 2. :ollowing strengthening with the CFRP material .the frame was again subjected to a series of excitations as follows: white noise {to determine the natural frequencies of vibration of the strengthened concrete frame), followed by three uniaxia] seismic excitations . applied in the X direction .of maximum accelerations 0.20 g. 0.40 g and 0.50 g. The natural frequencies of the strengthened frame obtained from the experimental testing, corresponding to the first two modes of vibration ,are presented in Table 2. Table 2. Experimental natural frequencies of vibration of the strengthened frame