Development and Implementation of Monitoring and Damage Detection Methods for Large Civil Structures

Washington University, Saint Louis MO

Investigators

Abstract

Development and Implementation of Monitoring and Damage Detection Methods for Large Civil Structures, CMS proposal 0245402 PI: Dyke, Washington University This proposal focuses on a research effort to develop, verify, and implement structural health monitoring (SHM) strategies to detect, locate, and quantify structural damage in large civil structures. The objective is on the development of methodologies appropriate for damage resulting from significant natural events, such as earthquakes, wind, blasts, as well as age/environmental deterioration. Strategies that are appropriate for large structures (long-span bridges, tall buildings, etc.) require special consideration due to the fact that these structures have closely-spaced vibration modes. Other characteristics of these structures include: they are continuous structures that are not well-represented with lumped masses; lateral and torsional motions can be highly coupled; using a limited number of sensors is feasible; and they have closely-spaced modes. Methods traditionally used for identification of the modal parameters are not necessarily appropriate for structures with closely-spaced modes, especially in a SHM situation where automation of the algorithms is needed. The focus is on the development of SHM methodologies that use rates of change of the eigenvalues, eigenvectors and static parameters (deformed shape, for a cable-stayed bridge) to locate and quantify damage (i.e., sensitivity-based). Additionally, using sensitivity-based analysis techniques, the capabilities and limitations of SHM techniques to detect various classes of damage will be examined for realistic damage scenarios. Numerical and experimental verification of the methodology is planned using existing models of and data obtained from cable stayed and suspension bridges (Emerson bridge spanning the Mississippi, and the Hakucho bridge in Japan). Furthermore, full-scale testing will be performed on the Pereira-Dos Quebradas bridge (a cable-stayed bridge constructed in 1995) which has a fully operational, ~300-sensor response acquisition system (sensors and data acquisition). This bridge has experienced several earthquakes since construction (including the Armenia earthquake in 1999) and response records are available. The advantages of using this particular bridge include: a full response acquisition system is already in place; the bridge is located in a seismically active area and response records are available; the temperature is also quite constant in this region of the world (fluctuating only 20F year-round) indicating variations in the modal parameters with temperature are expected to be small (daily changes will probably dominate temperature effects); the mass of long-span bridges is relatively constant; numerical models of the bridge have been already developed; and, the project has a broadly international perspective, providing an opportunity to consider hazard mitigation needs in several countries. The proposed research is linked to current research at Tokyo University (Japan, Prof. Masato Abe) and the Universidad del Valle (Colombia, Prof. Peter Thomson), facilitating a strategic collaboration between the three institutions and enhancing the research activities of the individuals. Significant efforts have been made to encourage prior student and faculty exchanges between these investigators, and these activities are being expanded. Prof. Abe has data from bridges in Japan, and is conducting research to examine realistic damage scenarios. He will share previously obtained data obtained from long-span bridges in Japan, collaborate on the development of these techniques, and offer his expertise in the area of long-span bridges. Prof. Thomson has a cooperative agreement and funding to implement a SHM system on the Colombian bridge. He has committed to examining temperature effects with his experience in this area using other bridges, verifying the existing finite element model, and hosting a multilingual web page for worldwide access/education (with mirror sites at Washington University and Tokyo University). The activities proposed will result in a better understanding of the effect of damage in the static and dynamic properties of large scale civil structures, as well as the training of a group of researchers that have a broad international perspective.