FALL 2017

ASPIRE is a quarterly magazine published by PCI in cooperation with the associations of the National Concrete Bridge Council. The editorial content focuses on the latest technology and key issues in the Concrete Bridge Industry.

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Page 55 of 63

SAFETY AND SERVICEABILITYCTION Active Monitoring of the Transport of Long-Span Precast Concrete Girders by Richard E. Lindenberg and Jonathan C. McGormley, Wiss, Janney, Elstner Associates Inc. The recently released PCI Recommended Practice for Lateral Stability of Precast, Prestressed Concrete Bridge Girders serves as a reminder of a particularly challenging problem for long-span bridge girder designers. What design forces should girders be required to resist prior to their installation and incorporation into the permanent structure? A particular issue lacking definition from available research is the behavior of girders during transportation. Very little real-world data have been gathered on this issue and yet there are reports of instances where girders were damaged during transport outside of lifting or accidents. Research In 2011, the Louisiana Department of Transportation and Development (LaDOTD) awarded Wiss, Janney, Elstner Associates Inc. (WJE) a research study to examine the transportation of precast concrete long-span girders to the jobsite. As a part of this research, WJE instrumented two 130-ft-long precast, prestressed concrete girders. One girder was an American Association of State Highway and Transportation Officials (AASHTO) Type IV and the other was a 72-in.-deep bulb tee (BT72). Monitoring occurred from moving the girders from storage to the truck through transport to the site and lifting from the truck. The girders traveled similar routes that exceeded seven hours in transit across Mississippi and Louisiana, and included a variety of roadway geometries commonly identified as possible contributing factors to girder damage during shipping (such as non-horizontal grades, railroad crossings, superelevation, bridge expansion joints, and the like). Supplementing the research were material testing and analytical modeling to better understand girder behavior. The girders were instrumented with a variety of dynamic strain, temperature, and inertial sensors (comprising threedimensional rotation displacement sensors with rate of rotation, along with translational triaxial acceleration sensors) to measure the behavior of each girder during transport. Additionally, geolocation of the girders was recorded to correlate significant events of the transport to measured readings. Both girders were supported in similar fashion, with a three-axle tractor pulling a fifth-wheel three-axle trailer supporting the front end of the girder that was positioned on a rotating bunk and a Hydra Steer six-axle rear jeep supporting the back end of the girder. The rear jeep provided considerable maneuverability, permitting the single driver/operator to efficiently steer the girder through a variety of maneuvers. The rear jeep was capable of operating in different steering configurations based on the navigation circumstances required. A single driver both drove and operated the rear jeep steering during transport of both girders. Data Collected Both girders traveled from Pass Christian, Miss., through Louisiana on Interstate 10 into Baton Rouge, La. From there, the transports deviated with one girder traveling to Alexandria, La., and the other to Lake Charles, La. For each girder, over 40 channels of instrumentation were collected at 100 Hz to record individual events along the route. Time-lapse video correlated with geolocation data allowed the research team to review events along the shipping route. The data were fused to correlate time lapse, geolocation, traditional time versus strain response, and sensor mapped imagery. A significant challenge of this research was to efficiently investigate many hours of collected data. The fused data was not intended to accurately identify critical stresses and girder position, but (cont. next page)

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