University of Cincinnati Infrastructure Institute

Research:

The University of Cincinnati Infrastructure Institute (UCII) has over ten years of experience in the research of assessment technologies for structures, including:

Loads and natural hazards (service, fatigue, strength, and extreme-event limit states)

Nondestructive evaluation via controlled truckload and modal testing

Long-term monitoring and on-line prediction of needed maintenance

Advanced on-site instrumentation systems and smart materials

Destructive testing, damage process mechanisms and evaluation of remaining service life

Characterization of performance under extreme events and acceptable risk

Interdependence and collocation of infrastructure systems

Geographical information systems

Social and economic effects

Three instrumented, steel-stringer bridges in Cincinnati have served as an on-going test bed for UCII research since 1995. Each has been fitted with a custom on-site monitoring system in order to record the effects of the environment, traffic, and our annual regimen of bridge tests. Moreover, one has been subjected to controlled damage and will permit evaluation of different hypotheses on damage detection. Together, they represent the birth, life, and demise of a typical steel-stringer bridge in Ohio.

Steel-stringer bridges, the most common bridges in Ohio, have and will continue to be an important bridge type for UCII. We have examined the before, during, and after effects of the largest truckload in Ohio history (352 ton) as it crossed three critical steel-stringer bridges in Toledo. Several of these bridges were tested and/or monitored during the recent construction of Fort Washington Way along the riverfront in downtown Cincinnati. Six specimens of a thirty bridge project have been truckload and modal impact tested for the beginnings of a statistical database for these bridge types in order to facilitate their general rating, overload routing, maintenance planning, and inventory management by the Ohio Department of Transportation (ODOT).

Other bridge types have also come under our investigation in recent years. A fiber-reinforced polymer (FRP) composite bridge in Dayton is currently being evaluated for its long-term and reliable application for the Infrastructure. A cantilever truss bridge in Ironton, built in 1922 over the Ohio River, is presently under our microscope due to concerns regarding its present load and fatigue capacity.

Given the synergy of the on-going research and test specimens, the expressed objective for UCII research is the systematic and integrated development of an optimal field testing regimen and a long-term on-site health monitor for highway bridges with a major emphasis on steel-stringer bridges. While the concept of an intelligent structure is not new, many of the issues that need to be resolved are not all recognized. Further, real-life implementation of well-researched concepts is still a major challenge.

Research difficulties...

The basic issues that are obstructing this research goal include:

Limitations in sensor and data-acquisition technologies

Limitations in state-of-the-art field experimentation

Optimal integration of human and machine intelligence, specifically:

Accumulated heuristic know-how and experience on bridge engineering

Structural testing results and on-line instrumented monitoring data

The final product is envisioned as an on-site continuous health monitor which:

Acquires sensor data at variable sampling speeds,

Communicates with peripheral devices such as a video camera or traffic scale,

Provides a graphical interface via Internet and phone line with a remote engineer,

Performs simple range and other checks for sensor faults,

Identifies parameters for a simple beam or grid model of the bridge,

Detects any structural degradation or damage via thresholds,

Has an open architecture for future expansion or connection.

This research is meant to complement and extend the work currently funded by the Ohio Department of Transportation, the Federal Highway Administration, the National Science Foundation and other agencies. The UCII researchers have developed a rational, global condition assessment technique that addresses the conceptualization and measurement of several unknowns for bridges, which include:

A lack of quantitative knowledge on the as-built state parameters (e.g., initial stresses, strains and displacements, local and global stiffness) and their variation over time;

A lack of clear and quantitative definitions for the performance parameters (e.g., reliability, functionality, serviceability, safety, lifecycle cost, etc.) and relationships between the state and performance parameters;

A lack of a clear and complete understanding of the phenomena which influence the state-of-force in a bridge; which lead to changes in state parameters; and/or which lead to a decrease in performance.

This research has and will be conducted collaboratively by a multi-disciplinary team of electrical, mechanical, and civil engineers bringing together knowledge and experience from the areas of space system health monitoring, mechanical modal testing and control, and bridge structural behavior and performance.