Development of fatigue loading and design methodology for high-mast lighting towers

Ryan J Sherman, Purdue University

Abstract

Although not often recognized as significant structures by the motoring public, ancillary structures, such as high-mast light towers (HMLTs) are important components of an efficient highway system. During extreme events, HMLTs greatly assist in ensuring safe travel for the public making the robust performance of these structures over the long-term critical for the smooth operation of daily traffic. Also, considering most HMLTs are located directly adjacent to the highway the impact a collapse presents to the safety of motorists is clear. Thus, recent failures of these structures have raised questions as to the robustness and safety of the existing HMLT inventory. Fatigue failures have occurred at the base plate to column weld, hand-hole detail, and anchor rods. Field observations and forensic studies of the failed HMLTs have indicated that wind-induced vibration has a significant impact in the fatigue life of these structures. Natural wind can produce significant stress cycles from loads due to simple wind gusts to more complex aero-elastic phenomena such as vortex shedding. Since neither the magnitude of the loads nor the frequency of application is understood research is needed to define a fatigue loading for the safe design of these structures. Additionally, a design methodology and specification with commentary must also be developed. The objectives of this research is to use data collected through field testing, laboratory wind tunnel testing, and analytical studies to develop: (1) loading and analysis criteria for use in the fatigue design of HMLTs; and (2) a design method and specifications for HMLTs.

Degree

M.S.C.E.

Advisors

Connor, Purdue University.

Subject Area

Civil engineering

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