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Browsing by Author "Lucas, Jeremy L."

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    Determination of remaining fatigue life of welded stud details on overhead aluminum sign panels in Virginia
    Cousins, Thomas E.; Lucas, Jeremy L. (Virginia Center for Transportation Innovation and Research, 2005-03-01)
    Some overhead highways signs in Virginia using a specific welded threaded stud and clip connection have failed while in service. From inspection of the signs it was determined that the failure was caused by fatigue of the weld connecting the threaded stud to the back of the sign panel. It was also observed that lower edge connections failed first and the failures progressed upwards in an unzipping pattern. A combination of natural and truck-induced wind gusts is the cause for the fatigue failure. Although signs with these connections are no longer produced by VDOT and all production was halted in early 2004, there are still approximately 4,000 signs in Virginia with this connection detail. The objective of the research project described here in was to determine priorities for an inspection and retrofitting plan for the remainder of the signs in Virginia. Specifically an S-N curve, which is a plot of stress range versus the number of cycles to failure, was to be developed to aid in predicting the remaining service life of sign panels using this connection detail. The authors opted to test single connections instead of multiple connection systems (i.e., an entire sign or portion thereof) because of material availability, the timeliness of testing, and the readily available equipment for testing. Connections simulating interior and exterior connections were tested under a pseudo-static load as well as for fatigue. Fatigue tests of interior and exterior sign connections developed failures of the aluminum panel instead of the expected weld fracture. Because the failure and fatigue threshold were not representative of failures found in the field, a proper S-N curve to help develop retrofitting priorities could not be developed. Recommendations from this program include increasing retrofit and inspection efforts, gauging and monitoring full-scale signs in service to understand loading conditions, and testing full-scale signs.
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    Structural load testing and flexure analysis of the Route 701 Bridge in Louisa County, Virginia
    Cousins, Thomas E.; Lucas, Jeremy L.; Brown, Michael C.; Stephen R. Sharp; Lane, D. Stephen (Virginia Center for Transportation Innovation and Research, 2004-06-01)
    A continuous slab bridge in Louisa County, Virginia, on Route 701 developed a planar horizontal crack along the length of all three spans. This project was designed to determine if the current load rating of the bridge could be raised and to document the behavior and stiffness of the bridge to serve as a benchmark for possible future tests, which may determine if there is progressive damage attributable to crack growth. These objectives were accomplished through field tests performed in November 2003. One truck (loaded to three different weights) was used to perform static and dynamic tests on the bridge, and the truck was oriented in three test lanes. Vertical displacement gages (deflectometers) attached to the underside of the bridge slab were used to measure deflections during the truck passes. The recorded deflections were analyzed and normalized to document the behavior of the bridge. The values were also compared to estimated design values in accordance with the AASHTO Standard Specifications for Highway Bridges. Under the testing loads, the bridge behaved elastically, and thus raising the load rating of the bridge was considered safe. The deflections and process are presented to allow comparisons with future tests to determine if there is progressive damage to the bridge attributable to crack growth.
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    Structural Load Testing and Flexure Analysis of the Route 701 Bridge in Louisa County, Virginia: Supplemental Report
    Lucas, Jeremy L.; Cousins, Thomas E.; Brown, Michael C. (Virginia Center for Transportation Innovation and Research, 2006-02-01)
    A continuous slab bridge in Louisa County, Virginia, on Route 701 developed a planar horizontal crack along the length of all three spans. This project was designed to determine if the current 12-ton posted load restriction of the bridge (instituted in January 2002) could be raised and to determine if the horizontal crack causes degradation in the structural integrity, specifically stiffness, over time. These objectives were accomplished through field tests performed in November 2003 and October 2004. One truck (loaded to three different weights) was used to perform static and dynamic tests on the bridge, and the truck was oriented in three test lanes. Vertical displacement sensors, or deflectometers, attached to the underside of the bridge slab were used to measure deflections during truck passes. The recorded deflections were analyzed and normalized to document the current behavior of the bridge. The 2003 values were compared to estimated design values in accordance with the AASHTO Standard Specifications for Highway Bridges. Under the testing loads, the bridge behaved elastically, and thus raising the load rating of the bridge to 27 tons was considered safe. Normalized deflections from both years were compared to determine if there was progressive damage to the bridge attributable to crack growth. The researchers concluded that no degradation of the stiffness of the bridge occurred over the last year of service. Carrying out the recommendation of this report to remove the posting that restricts loading of the structure will not incur any significant cost. The benefit of removing the posting would be that trucks weighing more than 12 tons, but not exceeding the legal limit, could cross the structure. This would allow the Virginia Department of Transportation to defer superstructure replacement, at an estimated cost of $350,000, thus freeing up funds to address more pressing needs.