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Critical Members of Aluminum Overhead Box Truss Sign Supports

Leduc, Paul D.
http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1431086791

Abstract Details

2015, Master of Science (MS), Ohio University, Civil Engineering (Engineering and Technology).
Overhead box truss sign supports on America’s freeways are exposed to fluctuating loads on a daily basis. Over time, welds connecting the diagonal cross frames to the main chords can fail causing the integrity of the structure to weaken. The aim of this study is to identify the members in an overhead truss support that are most critical to the strength of the system as a whole. Having knowledge of which member in a truss is the most essential in a frame can assist inspection crews to identify and prioritize damaged supports. Analysis of an overhead box truss sign support began with modeling on the finite element program, SAP2000. A 54’ aluminum truss overhead span was created using drawing TC-7.65 provided by the Office of Traffic Engineering. Simulated wind loads were applied to components of the structure to account for the lateral forces due to the drag of the signs as well as on any exposed frame surface. Once complete, elements from the truss frame were removed to mimic a failure of a welded joint. Four locations were chosen, with one joint removed from each of the four main chords. These four models were executed and the force-moment interaction ratio for each member in the frame was compared to their corresponding members in the control model. It was also hypothesized that ground displacements from traffic on a bridge could significantly alter the structural integrity of an overhead sign support. To determine whether a dynamic excitation of the supports could cause failure in the truss system, a bridge was modelled based off of the design of the I-70 Muskingum River Bridge in Zanesville, Ohio. The mid-span displacements due to a moving truck load were transferred to the SAP2000 overhead sign support model to mimic the behavior of a freeway sign on a bridge. The results show that failure occurred in one of the four cases, with the interaction ratio in critical members increasing significantly. With the weld severed on the top front chord under the wind loading specified by AASHTO, the demand/capacity ratio was 1.197 in two locations on the chord, suggesting failure would occur in this scenario. Lastly, adding a dynamic support excitation to the end supports of the overhead structure increased the stress in the chords. The top front and bottom chord exhibited demand/capacity ratios greater than one, indicating failure would occur. One member in the top front chord alone experienced a 34.22% increase in stress due to traffic-induced load displacements for a bridge mounted sign support structure.
Eric Steinberg, PhD (Advisor)
Ken Walsh, PhD (Committee Member)
Shad Sargand, PhD (Committee Member)
R. Damian Nance, PhD (Committee Member)
92 p.
Civil Engineering
Box Truss; Aluminum; Sign Supports; Overhead

Recommended Citations

Citations

  • Leduc, P. D. (2015). Critical Members of Aluminum Overhead Box Truss Sign Supports [Master's thesis, Ohio University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1431086791

    APA Style (7th edition)

  • Leduc, Paul. Critical Members of Aluminum Overhead Box Truss Sign Supports. 2015. Ohio University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1431086791.

    MLA Style (8th edition)

  • Leduc, Paul. "Critical Members of Aluminum Overhead Box Truss Sign Supports." Master's thesis, Ohio University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1431086791

    Chicago Manual of Style (17th edition)

ohiou1431086791
559
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This open access ETD is published by Ohio University and OhioLINK.