A Study On Damage Detection Of RC Simple Supported Beam Based On Modal Analysis

Engineering structures serving in various environment and service conditions often suffer different kinds of damages, the purpose of structural damage detection is to identify the appearance, location and the degree of structural damages which are based on the character -istics represented by structures. Many scholars in the domestic and abroad have done a large amount of work, presenting a series of method of discerning structure damage, however, the damage discern method based on mode analysis is still the most general and basic method.In this paper, research is carried on dynamic identification of damage of RC simple-supported beam, through loading and unloading tests step by step of nine RC simply-supported beams, an experimental dynamic monitoring is performed on the beam with the system of Data Acquisition Signal Process after each step of unloading. It obtains the variation law of first three orders frequencies of experiment beams by means of mode analysis technique. It analyses the modal frequency of simply supported beams in difference damage by ANSYS, the result shows that the finite element method is familiar to the experiment under smaller damage state.By caculating the relative change rate of mode shape from mode shape, it indicates that the relative change rate of mode shape can apply on damage identification of RC beam. However, the result of experimental and finite element analysis shows that, the change characteristics of small damage are easily concealled by the big damage if the two locations are quite closely, and which leads to the low efficiency to identify the small damage.The curvature modal is derived from the displacement modal with second order differentiation method, curvature modal can identify the damage of RC simple-supported beam more accurately, it is sensitive to tiny damage of RC beam. Moreover, it can identify damage without the initial modal parameters of intact structure and can apply on the identification of multiple damages of structure. The noise is introduced into mode shape, then the author analyses the effect on damage identification under different noise with ANSYS software.