AMBIENT VIBRATION TESTING OF -STRUCTURES

Abstract

Ambient Vibration testing of structures is a:- experimental method of determining the periods, damping j-atios, mode-shape coefficients of the structures. These values can be used to validate/calibrate the mathematical model of the structure. This method does not require artificial excitation of the structures. Only natural excitation mechanisms are used. These are natural micro-tremors, wind or traffic induced excitations,. shortly known as "Environmental Noise" or "Ambient Vibration". This thesis deals with Ambient Vibration measurements and analytical studies of structures. The recently procured instruments, Solid State Recorder (SSR--1 ), Ranger seismometer (SS--I) and the associated software SWS'has been used for analysis of data. Two typical structures were chosen for ' Ambient Vibration testing namely (i) the Building of the Department o Earthquake Engineering, and (ii) Communication Tower of the Electronics Engineering Department. Observations were taken with suitable positioning of the sensors. Natural frequencies, damping ratios upto some extent and the response spectra (floor spectra) were obtained from the analysis of experimental dat-&.. These two buildingss were also modelled mathematically for determining dynamic characteristics. The thrnparisun between experimentally measured time periods an analytically computed values have also been made. The analytically obtained values of natural time periods are found to be'-'about &OY higher than experimentally measured values.