Dynamic response sensitivity for structural condition assessment

Abstract

Assessment of the condition of existing structures is vital for their maintenance and repair. Prestress force has been used widely with long span structure, and it is the most important factor to describe the load-carrying capacity of the structure. Besides, many structural systems are susceptible to damage in their useful lives due to many reasons. A change in the prestress force and structural damages will produce changes in the dynamic characteristics and the dynamic responses of the structure. This is the basis for the vibration-based damage and prestress force identification methods. In this dissertation, two methods for damage detection are developed. The first method is dynamic response sensitivity-based finite element model updating. Elemental damage is identified from the measured structural dynamic responses. The other approach is parameterization of crack in beam. The parameters of the crack, i.e. the location and the depth of the crack are identified from the measured dynamic structural responses in time domain. The contributions in this desertation are: 1. Time domain response sensitivity with respect to physical parameters of a structural system is obtained numerically and analytically, and it was used for structural damage detection; 2. Further applications of the dynamic response sensitivity for damage detection are developed, such as structural damage detection taking into account the temperature effect, differentiating different damage types in structures made of isotropic homogeneous material, prestress force identification and damage detection including the load environment. 3. A method for parameterization of crack in beam is proposed and a method for identifying the crack location and crack depth is developed in time domain using the measured dynamic response; 4. A method for prestress force identification in structures is developed based on modal superposition. The prestress force is identified from the measured dynamic responses of the structure.