Study On The Flexibility Sensitivity Method For Structural Damage Detection Of Bridge Under Ambient Excitation

The identification of bridge structure damage is crucial for the structure safe, and how to identify the injury extent and location accurately in the process of injury identifying become a hot topic. This paper presents a damage identification method which is a sensitivity-based environmental compliance incentive as the theoretical basis. Through the modal matrix get in dynamic testing site after the structure damaging and analysis modal matrix get in it is not damage by establishing its original finite element model, then can calculate the unit damaging degree with the theoretical derivation formula. The main contents of this article are:1. Introduces a method named flexibility sensitivity under ambient excitation which using modal data to monitor the structural damage.And since the environment resulting excitation is not normalized, so make a introduction of modal normalization coefficients which will used be as the new unknown amount. With the proper deformed and straightened using matrix operations and generalized inverse, can calculate these unknown coefficients.2.Making a simple model with charpy, establish the model according the rules of the finite element theory, and simulate the damage situation with modifying the elastic modulus of one unite. With the matrix obtained modal analysis of before and after damage, calculate with using the formula of mathematical deriving aiming at verifying the scientific and practical of this theory.In this paper, make a comparing of the single injury and multiple injury situations with the charpy model.3. Put the Chengde bridge as a example,then establish the finite element model based on the original drawings,resulting modal mass normalization matrix; In addition, according to its actual modal testing conducted to obtain the environment of the bridge structure excitation non-mass-normalized modal data; Then use the non-mass-normalized modal mass coefficient under ambient excitation normalized data into a normalized data; Finally, put the modal normalization coefficient and damage parameters as unknown quantity,and solve these coefficient by appropriate modification of the flexibility sensitivity equation.