Condition evaluation of large constructed structures has been widely researched over the last decade. In numerous studies dynamic testing has been used as the primary experimentation tool for measuring the dynamic characteristics and extracting various proposed indicators of structural condition. Despite these efforts, dynamic testing of constructed systems has not yet evolved to a point that it can be standardized as a tool for condition evaluation. Writers believe that two major sources of uncertainty in dynamic test based condition evaluation are the reasons for the gap between concepts and meaningful real-life applications. Most dynamic test methods are built on principles of observability, linearity and stationarity. The first major source of uncertainty is due to constructed systems and their loading environments’ inherent complexity leading to limitations in the application of the above tenets. The second category of uncertainty is related to the experiment, i.e. sensing, data acquisition, processing and analysis for different dynamic test methods. Ambient vibration (i.e. operational modal analysis) and impact testing are two different tools aiming to identify same parameters. Comparative evaluation of different test methods at the presence of different levels of uncertainty will enable us to assess the reliability of dynamic testing tools for condition evaluation. Writers designed a set of experiments on a laboratory physical model to investigate the effects of these two groups of uncertainties on modal parameter identification. Results will be discussed along with mitigation measures of uncertainties in dynamic testing of constructed systems.
In this paper a structural identification (St-Id) case study on a laboratory physical model is presented. The main objective is to understand the reliability of ambient monitoring as the principal global experimentation tool for St-Id and to address the issues related to the projection of the laboratory study to a bridge structure. Linear deterministic FE modeling, controlled static load tests, impact tests and ambient vibration tests are utilized as St-Id tools to supplement each other in the study. The results showed that even under controlled laboratory conditions, uncertainties in the St-Id process cannot be completely avoided and govern the reliability of an St-Id study. Issues regarding the successful application of ambient vibration testing on a real-life bridge structure based on laboratory model results are addressed.
Health monitoring of infrastructure systems for their proactive management to make the best use of limited resources for their optimum life-cycle performance, protection and preservation is a promising paradigm. Structural health monitoring (SHM) technologies have sufficiently evolved to accomplish real-time post-hazard evaluation of highway bridges. Solution of the pressing and critical problem of post-hazard bridge condition evaluation is possible by problem-focused, coordinated cross-disciplinary research. A newly initiated research program, which has been formulated for creating knowledge to construct an intelligent bridge SHM system, is presented in this paper. An overview of the state-of-the-art research in SHM is outlined.
Proc. SPIE. 4337, Health Monitoring and Management of Civil Infrastructure Systems
KEYWORDS: Statistical analysis, Data modeling, Databases, Inspection, Nondestructive evaluation, Optical inspection, Geographic information systems, Finite element methods, Bridges, Information technology
The importance of rational decision-making for optimum resource distribution of civil infrastructure systems management is well recognized. Bridges, serving as node points of the highway transportation system, are critical components of the nation's infrastructure. As the nation's bridge population is aging, management decisions must be based on an objective, complete, accurate and compatible information for maximum reliable bridge lifecycle. For bridges sharing common materials, similar geometric design attributes and behavior mechanisms, fleet-strategies for health monitoring would offer significant advantages. Improvements from fleet health monitoring would lead to objective engineering knowledge for optimal decision making. This paper provides an overview of fleet health monitoring concept, then summarizes an on-going research on re- qualification of reinforced concrete T-beam bridge population in Pennsylvania.
Structural identification (St-Id) of constructed systems is of interest to researchers as well as civil infrastructure systems owners and operators. St-Id offers an objective, quantitative evaluation of constructed systems through effective and integrated utilization of state-of-the-art experimental and analytical technologies. During the past five years two test beds were created at the University of Cincinnati and Drexel University for the exploration of analytical and experimental barriers obstructing successful St-Id applications. The two physical models are plane-grid structures with different controlled mechanisms of uncertainty. The objective of this paper is to present the St-Id studies to the two physical models. The principal mechanisms of uncertainty that governed the global structure behavior of the first physical model were nonlinear visco- elastic boundaries. The second model incorporated a fiber- reinforced polymer composite deck and its connection details to the grid. The impact of these different mechanisms of uncertainty on the success of St-Id will be addressed.