09-10-2014, 03:56 PM
A full-scale ambient vibration survey has been carried out on 140 m high reinforced concrete stack at Narora Atomic Power Station, Narora. Two FBA-11 force balance accelerometers have been used to determine the dynamic characteristics in terms of natural frequencies, mode shapes and damping. For these, time history plots obtained from a strip-chart recorder and Fourier spectra obtained from a spectrum analyzer have been used. The stack has been theoretically analyzed by idealizing it as an Euler-Bernoulli cantilever beam. Lumped mass models have been developed and analyzed by SAP80 program, for fixed and flexible-base conditions. The results obtained in terms of frequencies and mode shapes have shown good agreement between the experimental results and theoretical results for the flexible-base conditions. This has indicated that during the dynamic vibrations, stack at Narora has significant interaction with the foundation