Date of Award
Doctor of Philosophy
Civil, Construction, and Environmental Engineering
Terry J Wipf
Brent M Phares
The evolution of structural materials and sensor technology has impacted the bridge industry by improving the robustness of the highway network and providing behavior based condition assessments. During the last decades, conventional materials have been supplemented with state-of-the-art materials (e.g., carbon and fiber based, ultra-high performance concrete, etc.). The evolution of smart or intelligent structures by incorporating systems to quantify performance will continue to revolutionize the bridge industry. While laboratory and field applications have indicated that smart materials are appropriate for bridge applications, additional investigations regarding sensor installation, deployment and data reduction are still needed. The work described herein is a collection of field and laboratory tests in which sensors were applied to verify structural and material behavior and develop smart members for integration as part of a structural health monitoring system for bridge superstructures.
Three projects are presented in which new materials and unique structures were evaluated using specialized sensors and monitoring techniques. Two basket-handle arch pedestrian bridges with high-strength steel hanger rods supporting a pre-cast, post-tensioned concrete panel deck system were monitored to prevent deck cracks in the vicinity of the hanger rods. Fiber optic sensors and externally mounted accelerometers were attached to the hanger rods to indirectly determine the tensile forces during incremental construction stages and in service conditions. For the second project, a three-span prestressed concrete (PC) girder, composite deck bridge was monitored and evaluated. One end span consisted of composite FRP deck panels and was compared to the opposite cast-in-place reinforced concrete deck end span. Strategically placed transducers measured strain levels on the PC girders and the FRR panels from controlled live and ambient traffic loadings to determine the degree of composite action, load distribution, and maximum in-service strains. A FRP panel temporary bypass bridge was evaluated as a replacement to typical steel temporary bridges as part of the third project. The research focused on the design, fabrication, construction and load testing of this state-of-the-art bridge. This bridge was instrumented with transducers for measuring deflections and loaded with a static truck at pertinent locations to evaluate its performance.
A five year research plan was established to develop a conceptual smart timber bridge made of glued laminated (glulam) stringers and a transverse glulam deck. Both stock and custom fiber optic sensor packages were implemented to quantify the structural response. The first of multiple phases of this national five year plan includes the development of an efficient structural health monitoring system and a smart timber bridge field demonstration. To support these goals, two types of FBG sensors packages were developed, the first evaluated the structural strain response and the second isolated the sensor from mechanical strain for detecting deterioration parameters (e.g., moisture content, corrosion, wood deterioration, etc.). Techniques were developed for embedding and attaching the FBG sensor packages to glulam specimens. Small scale specimens were instrumented with the custom FBG sensor packages and tested under a range of temperature and loading conditions to determine sensor viability. A full scale glulam beam was instrumented with similar FBG sensor packages to demonstrate applicability and evaluate performance at service level proportions.
From this work, the following contributions in structural bridge monitoring were added to the state-of-the-art:
* Application of FBG sensors and accelerometers to monitor the structural behavior of a bridge during construction.
* Applied testing of non-traditional FRP deck panels to validate composite action.
* Initial development of a smart timber bridge structural health monitoring system.
* Development of FBG sensor packages for implementation in glulam members as part of a smart timber bridge.
Ursula Mercedes Deza
Deza, Ursula Mercedes, "Development, Evaluation and Implementation of Sensor Techniques for Bridges Critical to the National Transportation System" (2011). Graduate Theses and Dissertations. 12313.