Selected results The results presented here are preliminary and may be expanded on during presentation of the paper next year. In Figure 5 the typical time response histories are shown for vertical and horizontal accelerometers attached to upper main chord near mid span. The data indicate that the range of vertical accelerations at mid span is lower than the horizontal accelerations. The horizontal accelerations also exhibit a delayed low frequency response. Both traces range between +/-0.010 gs. and exhibit similar frequency content. The horizontal acceleration levels of the upper chord shows a similar response. Horizontal acceleration levels near the base of the DMS cabinet are approximately five times larger than other mid span acceleration levels. The horizontal accelerations of the top of the north east support pole are shown in Figure 7. These accelerations appear to have a range two or three times larger than the mid span accelerations. References 1. American Association of State Highway and Transportation Officials. Subcommittee on Bridges and Structures., "Standard specifications for structural supports for highway signs, luminaires, and traffic signals," 5th ed, American Association of State Highway and Transportation Officials, Washington, D.C., p., 2009. 2. Fouad, F.H., "Structural supports for highway signs, luminaires, and traffic signals. NCHRP report,, National Academy Press, Washington, D.C., 2003. 3. Pantelides, C.P., J. Nadauld, and L. Cercone, "Repair of cracked aluminum overhead sign structures with glass fiber reinforced polymer composites," Journal of Composites for Construction, 7(2), p. 118126, 2003. 4. Wipf, T.J. and B.M. Phares, "EVALUATION OF INTERSTATE 80 SIGN TRUSS," Iowa State University Iowa Department of Transportation, Ames, IA, p. 14 , 2002. 5. Huckelbridge, A.A. and A.T. Metzger, "Investigation of the dayton, Ohio, IR 75 sign truss failure of september 11, 2006," Journal of Performance of Constructed Facilities, 23(5), p. 372-378, 2009. 6. Park, J. and J. Stallings, "Fatigue evaluations of variable message sign structures based on AASHTO specifications," KSCE Journal of Civil Engineering, 10(3), p. 207-217, 2006. 7. Park, J.S., W. McLean, and J.M. Stallings. "Wind-induced fatigue of VMS sign structures," Proceedings of the 2004 Structures Congress - Building on the Past: Securing the Future Nashville, TN, p. 407-411, American Society of Civil Engineers, 2004. Fig 5 Accelerometer and BDI gage installations near mid span on lower truss chords and connecting struts BDI Paired gage installations Bi-axial accelerometer installation 0 2 4 6 8 -0.015 -0.010 -0.005 0.000 0.005 0.010 0.015 Time (s) Acceleration (gs) Vertical accel. Horiz. accel. Fig 7 Time history of vertical and horizontal acceleration of top chord at mid span 0 1 2 3 4 5 6 7 8 -0.05 -0.04 -0.03 -0.02 -0.01 0.00 0.01 0.02 0.03 0.04 0.05 Time (s) Acceleration (gs) North pole sway East pole sway Fig 7Acceleration of top of north-east support pole 415
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