Benedikt Weber

Damage Identification in a Truss Tower by Regularized Model Updating

This paper presents a sensitivity-based damage identification of a three-dimensional truss tower tested in the laboratory. A finite-element model is updated by modal parameters obtained from ambient vibration measurements. The paper focuses on details of modeling and model updating. To get a realistic model, it was necessary to include eccentric connections, bending stiffness in truss members, and foundation flexibility. For model updating, a number of mathematical techniques are combined in a consistent way, including regularization of the nonlinear updating problem and its linearization. Considering all these details correctly, damage in the truss has been successfully identified. However, it is also demonstrated how neglecting some of these algorithmic details can lead to incorrect results. It is also shown how static condensation can lead to a model that is valid for the undamaged case but cannot adequately represent the damaged case.

Nonlinear Stay Cable – Bridge Deck Interaction

Nonlinear coupling between stay cables and bridge deck can cause internal resonance. This coupling is due to the length change of the cables when vibrating. During one cycle of transverse motion, the cable length is reduced twice, once for the positive and once for negative displacement. This internal resonance occurs when the natural frequency of the deck is twice the natural frequency of the cable. It is thus also called 2:1 resonance.