Damage identification in structural joints using generic joint elements

This paper considers the identification of damage in joints for a structure where no baseline model is available. Linear equations are formulated to relate the joint parameter variations caused by damage to the measured or simulated responses in the frequency domain. Generic joint elements with only translational degrees of freedom are defined to model the structure with damage at the joints. For a particular type of joint, the generic joint element stiffness matrices are formed by using only the translational components of the mode shapes, which can be approximated intuitively or by a detailed FE analysis of the joint. The modeling with generic joint elements also makes the consideration of the rotation coupling more natural. In addition, using generic joint elements can avoid the geometric complexity involved in defining structural joints in the traditional way. With the assumption that the damage appears only in the joints, the other parts of the structure such as beam-like and plate-like components do not need to be modeled in the formulation. The methods are illustrated by a plane portal frame with both L-shape and T-shape joints. The results show that the method is effective in locating the damage in these joints.