Development of Optimal Experimental Design Parameters for Pseudo Ambient Vibration Testing of Bridges

The United States of America is facing an infrastructure crisis that is characterized by aging and deteriorating structures, a significant backlog of maintenance and upgrades for existing infrastructure, limited funding and lack of practical and effective tools for identifying and prioritizing the most pressing infrastructure needs. The American Association of Civil Engineers (ASCE) qualifies America’s infrastructure with a D+(ASCE Report Card). This rating reflects the general state of infrastructure that is unlikely to improve dramatically in the short-term, yet the situation costs the nation billions of dollars annually due to losses in economic efficiency and productivity, and in some cases can needlessly expose communities to safety risks that would be considered unacceptable for other industries. There is a clear need for the development of better tools for assessing the condition of existing aged and deteriorated structures to support more timely and effective infrastructure maintenance management and planning decisions. The focus of this research is to improve upon an existing test method that is widely used for characterizing the performance of in-service bridges and other civil infrastructure systems. The specific characterization method explored here is known as ambient vibration testing (AVT). It involves measuring a structure’s vibration responses due to environmental and/or operating loads in order to quantitatively identify its dynamic characteristics and to evaluate its structural properties, performance and condition. The identified dynamic properties are mathematically related to the physical characteristics of the structure can be compared to a baseline characterization to identify and evaluate structural damage and deterioration. In AVT, the structure vibrates due to unmeasured dynamic forces from natural sources and operating traffic, and because these inputs are unknown, their characteristics must be assumed. Researchers at the University of Arkansas are trying to improve upon ambient vibration testing by using multiple low-cost shakers to provide known and controlled dynamic forces to the structure thereby reducing the uncertainty in this approach. Establishing the optimal test design parameters for this new vibration testing approach represents a critical need for improving the cost, reliability, and testing time requirements for this novel experimental method.