United States Department of Transportation
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Remote sensing for bridge scour projects : final report, July 31, 2009.
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2009-07-31
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Alternative Title:Remote sensing for bridge scour projects.
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Abstract:large percentage of bridges within the state of Pennsylvania are located over waterways. For such bridges, much of the supporting structure is positioned within the river or stream bed of the waterway. As a result, these bridges are susceptible to bridge scour, the washing away of fill around structures, which compromises the safety of the bridge. Bridge inspections have a limited frequency at which they can occur. In between these inspections, unmonitored and difficult to detect events may happen that create an immediate danger to the general public. The purpose of Work Order #18 (this research) was to create a prototype system for bridge scour monitoring that would provide continuous monitoring.
The technique utilized for this particular bridge scour monitoring was detection using float out devices. The float out device concept is to bury transmitters at various locations around a bridge structure. These devices would then be released due to the scour’s removal of material around the device. A receiver on the bridge would receive the transmission and perform an action. A float out device system would provide an initial indication of scour severity for further investigation.
To realize this technique, a prototype remote sensing system was designed to have three main components that work together to indicate bridge scour. The first component is a transmitter coupled with circuitry and encased such that it is watertight and can be buried under the materials surrounding the bridge structure. It is able to be armed such that it will remain dormant while buried and become active upon its release and rise to the surface of the water. Lastly, the communication link and time it takes the unit to rise are such that transmission of a message can consistently occur. This component in its entirety is referred to as the Sensor Unit within this document.
The second component is a receiver coupled with circuitry that will be encased and installed on the bridge overpass. The receiver is able to store and interpret the RF messages sent by the Sensor Unit. Given this interpretation it is able to provide a visual indication of scour severity by interfacing with the third component described shortly. The receiver circuitry will have the capability to be powered continually. This component in its entirety is referred to as the Receiver Unit.
The third component is a set of lights (LEDs) encased with its supporting circuitry. The purpose of these lights is to correspond to a particular Sensor Unit. This will allow for immediate comprehension by the inspector without having to be on the bridge. This component must be able to interface with the Receiver Unit as the light that will be lit is controlled by the Receiver Unit. This component in its entirety is referred to as the Light Indicator.
This document contains documentation of the work done for Work Order #18. This document contains all analysis leading up to the system design as well as the rationale behind design decisions made. An initial assessment of what the Scour Monitoring System would be composed of and its functionality is found in the requirements section. A less technical overview of the system designed to meet those requirements can be found in the specifications section.
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