The acceleration data of a simple supported steel beam model are collected separately under the conditions intact and injury, then data processed by using EMD and shape factor, the damage locations are found by comparing.

A simulated beam example and an experimental beam example show that the method can detect damage location with satisfactory precision.

Contrast to the experimental results, the finite element analysis and simulation have been carried out to study the relation of frequency and damage degree ,damage location of the beam.

So the key to the problem is to recognize structure damage position and damage regulation accurately and timely.

The results of damage detection for hydro-pipe show the effectiveness and predominance to detect the damage positions.

Through elaborating theoretical basis of modal analysis, the value is researched about standard simple-supported damaged beam so as to find out the influence of different damage position on beam vibration modal and their correlation.

The results show that the method of canceling noise is better,and this grounds for the bug detection and location of damage identification.

An analysis method of structural damage identification is presented based on.

Vibration_based damage identification is one of the few methods that detect changes in the structure on a global basis.

An improved crack detection method using modal frequencies of jacket platforms;

And the newest development in the area of crack detection is also summarized.

The lowest ten natural frequencies and modal shapes of the jacket models are calculated by finite element method,The evaluated modal parameters of the models with a crack at different location or of different depth in the underwater structure are calculated numerically for crack detection.