Dynamic condition assessment of a cracked beam with the composite element model

Existing models of local damage in a beam element are usually formulated as a damage in a single element, and the coupling effect between adjacent damages is simply ignored. This coupling effect is larger in the case of a fine mesh of finite elements or when there is a high density of damage in the structure. This paper studies such effect from multiple cracks in a finite element in the dynamic analysis and local damage identification. The finite beam element is formulated using the composite element method [P. Zeng, Composite element method for vibration analysis of structure, Journal of Sound and Vibration 218 (1998) 619–696] with a one-member–one-element configuration with cracks where the interaction effect between cracks in the same element is automatically included. The accuracy and convergence speed of the proposed model in computation are compared with existing models and experimental results. The parameter of the Christides and Barr [One dimensional theory of cracked Bernoulli–Euler beams, International Journal of Mechanical Science 26 (1984) 639–648] crack model is found needing adjustment with the use of the proposed model. The response sensitivity-based approach of damage identification is then applied in the identification of single and multiple crack damages with both simulated and experimental data. Results obtained are found very accurate even under noisy environment.