Experimental Study of Crack Identification in Thick Beams with a Cracked Beam Element Model

Abstract

Model-based crack identification in beam-like structures has been a classic problem. The authors have recently developed a framework to identify crack damage in beams based on a cracked beam element model, which stems from the local flexibility and fracture mechanics principles. This paper presents an experimental study on the cracked beam element model for crack damage identification in a physical testing environment. Five solid beam specimens were prepared with different numbers of cracks, and they were subjected to a modal testing and analysis procedure to extract the natural frequencies and mode shapes. The extracted modal data were then compared with the predicted counterparts using the cracked beam element model to verify the accuracy of the model. The extracted modal data were also employed to inversely identify the cracks with the cracked beam element model through a model updating procedure. Results indicate that all the cracks can be identified correctly with accurate crack depth and location information. To enhance the modal dataset for finite-element (FE) model updating, the artificial boundary condition (ABC) technique has also been applied on the test beams, and the incorporation of such frequencies proves to enhance the identification of cracks from the FE model updating.