Nonlinear Model Updating in Concrete Structures based on Ambient Response Data

The detection of changes in vibrational behavior has long been applied as a potential means of Proceedings of the IMAC-XXVII February 9-12, 2009 Orlando, Florida USA ©2009 Society for Experimental Mechanics Inc. damage detection. However, existing damage diagnosis techniques are primarily limited to linear models in which the stiffness of some of the elements is reduced to represent damage. Although these methods appear to be adequate for locating and quantifying the present damage in the structure, they are not sufficient for determining future performance of the structure, which can only be determined using nonlinear models. This paper focuses on the challenging task of updating nonlinear models for concrete civil engineering structures. A nonlinear hysteretic material model is constructed to accurately portray the fundamental hysteretic behavior of concrete structures. A systematic methodology to perform damage detection and, more importantly, update the nonlinear model for prediction is proposed. This new method is designed to use low-level ambient vibration data to detect changes in the modal parameters. With the acquired modal information, the damage parameters which control the nonlinear material model are updated. The final updated nonlinear model may be utilized not only to evaluate structure’s current damage state but also to predict its future behavior. A concrete shear-wall is analyzed numerically to demonstrate the proposed method.