Static and Dynamic Behavior of 'Tri-Chord Truss'Overhead Sign Support Structures.

摘要

This report presents the results of a three part research effort on the experimental,static,and dynamic behavior of tri-chord overhead sign support structures. The experimental effort was primarily concerned with the degree of fixity of the column to truss connection required for analytic modeling. Repeated load tests of the chord splice are also included to provide information regarding fatigue strength. Analysis of dynamic response to extreme wind loads indicate that the AASHO Specifications are adequate. It is also shown that Stockbridge dampers are effective in reducing vibrations due to wind excitation. Finally, a computerized and highly reliable approximate method of analysis is devised for this type of structure. The method accounts for tapered chord tubes and permits the columns to be either one tube or two tubes trussed together. The U-bolt connections are assumed not to slip and no consideration is given to precambering or buckling instability. Comparison of approximate and 'exact'methods shows close agreement. The computer program is listed in the Appendix.