In the recent years, structural health monitoring for civil structures using experimental modal analysis has been developed. Experimental modal analysis is the process of determining the dynamic parameters (frequencies, damping factors, modal vectors and modal scaling) of a linear, time invariant system by way of an experimental approach. It began in 1940’s in aircraft then it used in civil structures since the advent of the digital mini-computers and the digital Fast Fourier Transformation (FFT) spectrum analyzer in the early 1970’s. In this paper, the damage in ferrocement tank is detected experimentally by changing in its dynamic parameters due to two damages that were manufactured in its wall. Also in the current paper, theoretical models using ANSYS finite element software were developed to find the modal parameters of the healthy and damage tank. The current results showed that the theoretical models give accurate results in comparing with the theoretical results. Also the experimental modal analysis is quick, easy and inexpensive method to detect the damage in the ferrocement tank
