Super Tech ‘Super’ Structures

From idea to ribbon cutting and beyond, technological breakthroughs are revolutionizing bridge superstructures.

By Tom Kuennen, Contributing Editor

New technologies – both active and passive, mechanical and electronic, as-built or retrofitted – are revolutionizing how bridge superstructures are designed, built, protected and maintained.

Bridges have almost nothing in common with roadways, except they abut each other, are used by vehicles, and have the same ownership. It’s the same with conventional bridge superstructures as opposed to bridge piers and footings; they are joined to each other but largely function independently, with their own design, maintenance and rehab needs.

That’s why new “super” technologies for superstructures deserve an independent look, as bridge superstructure life-cycle performance is impacted by the quality and implementation of bearings, deck surfaces, monitoring systems, sealants, coatings, abutment and joint systems, reinforcing steel, drainage systems, seismic reinforcement, and much more.

Managing Superstructure Life Cycles

The life-cycle management of bridges and superstructures is so important that the Federal Highway Administration (FHWA) has launched an Exploratory Advanced Research (EAR) program project, Development and Demonstration of Systems-Based Monitoring Approaches for Improved Infrastructure Management Under Uncertainty. It describes a next-generation, integrated, structural-monitoring framework to boost reliability of bridge assessments, and is now underway at the University of Central Florida and Lehigh University.

Effectively managing bridge maintenance, repair and replacement requires a deeper understanding of how these complex structures and their components respond to environmental conditions, increasing traffic loads, and to events such as earthquakes, floods, fires and collisions.

FHWA’s EAR program focuses on long-term, high-risk research with a high payoff potential.

“Our knowledge of how structures behave over time under a wide range of environmental and load conditions is broad but incomplete,” says Hamid Ghasemi, of FHWA’s Office of Infrastructure Research and Development. “This research is pursuing a structural monitoring framework that can accommodate the collection, integration and analysis of monitoring data to better predict bridge performance. The goal is to provide the best information possible to inform decisions about further testing, repairs and reconstructions.”

The project is unique: in the variety, location and number of sensors it utilizes; in its “global” approach to monitoring structural, mechanical and electrical components; in the sheer amount of data that could be collected, integrated and effectively analyzed; and finally, in new methods of quantifying uncertainties in making decisions about a structure’s reliability and load-carrying capacity.

The framework project will integrate bridge and superstructure data from a broad array of sources for analysis and future research, including historical data. In an attempt to characterize a bridge’s reliability, it will define safety and serviceability performance expectations for individual structural components and structural systems. And it will develop reliable 3D finite element models that can be constantly updated with new data.

Sensors Generate Data

In this project, using state-of-the-art data mining and analysis techniques, bridge superstructure information generated during the design, construction and maintenance of structures can be integrated with continuously updated data from a network of monitoring sensors.

Common monitoring technologies (e.g., sensors for strain, temperature, displacement, tilt, vibration) are being used, as well as technologies that are newer or not traditionally used in bridge monitoring (e.g., video imaging, infrared sensing, pressure gauges and microphones).

In particular, the use of sensor data in structural health monitoring shows great promise in the laboratory and in real-life implementation for predicting the load-carrying capacity of bridges, says FHWA.

A precast, prestressed panel is placed on I-287 ramp in New Jersey.

The project’s technologies, algorithms and methods have been tested in physical test beds in laboratories and now are being implemented on a mid-size steel bridge near Ft. Lauderdale, Fla., with support from the Florida DOT, District 4. This one-year demonstration under real-world conditions will allow investigators to evaluate and refine the framework under a full annual cycle of weather and traffic conditions.