High-Mast Tower Foundation

High-Mast Tower (HMT) foundations have been traditionally designed and constructed using cast-in-place foundation with anchor bolts that are used to secure the tower to the foundation. This type of design requires a base plate that is welded to the tower shaft. The Nebraska Department of Transportation (NDOT) has recently experienced issues with stresses that this type of design presents at the anchor bolt/foundation or base plate/tower shaft interface. This issue in worst cases may lead to a premature failure due to high-cycle fatigue as one of the towers at Milford, Nebraska that fell down during a winter snow storm event in 2018. This research project objective was to develop an alternative design for HMT foundations with direct embedment of HMT which can eliminate fatigue-prone details associated with the pole-to-base plate connection which is the primary location of failure. First, the literature that includes research from academia and industry, current and proposed state of practice from industry, examples of design specifications and guidelines, and corrosion for buried structures were reviewed. Secondly, structural loads for the typical 120- and 140-ft HMTs constructed in Nebraska and the soil resistance for them were calculated. The structural loads were computed using the AASHTO LRFD Specifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals, with a spreadsheet based on the fundamental principles of structural analysis. The geotechnical foundation resistance calculations were made to check the vertical and horizontal soil capacity for the typical HMTs used in Nebraska. In addition, further parametric study was conducted using two numerical software: LPILE and COMSOL for varying soil conditions and foundation systems with different embedment length and backfill diameter for the service level base moment and shear. Required embedment length and backfill diameter are provided as a matrix using the LPILE analysis results. Finally, based on the site considerations and constructability, a draft design and construction specification for soil parameters that can be used for Nebraska soil conditions are provided.

  • Record URL:
  • Corporate Authors:

    University of Nebraska, Lincoln

    Durham School of Architectural Engineering and Construction
    1110 S. 67th Street
    Omaha, NE  United States  68182

    University of Nebraska, Lincoln

    Department of Civil and Environmental Engineering
    Lincoln, NE  United States  68588

    Nebraska Department of Transportation

    Research Section, 1400 Highway 2
    Lincoln, NE  United States  68509

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Authors:
  • Publication Date: 2020-12-31

Language

  • English

Media Info

  • Media Type: Digital/other
  • Edition: Final Report
  • Features: Appendices; Figures; Maps; Photos; References; Tables;
  • Pagination: 108p

Subject/Index Terms

Filing Info

  • Accession Number: 01765566
  • Record Type: Publication
  • Report/Paper Numbers: SPR-P1(20), M111, 48952
  • Files: TRIS, ATRI, USDOT, STATEDOT
  • Created Date: Feb 1 2021 12:13PM