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:
  https://dot.nebraska.gov/media/4k5p10op/m111-final-report_submission.pdf
• 
• Record URL:
  https://rosap.ntl.bts.gov/view/dot/56424
• 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:
  • Sim, Chungwook
  • Song, Chung Rak
  • Kreiling, Brandon
  • Puckett, Jay A
  • 0000-0002-0834-7549
• 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

• TRT Terms: Anchoring; Backfilling; Foundations; Literature reviews; Parametric analysis; Soil structure interaction; Structural supports
• Identifier Terms: COMSOL (Computer program); LPILE (Computer program); LRFD
• Geographic Terms: Nebraska
• Subject Areas: Bridges and other structures; Geotechnology; Highways;

Filing Info

• Accession Number: 01765566
• Record Type: Publication
• Report/Paper Numbers: SPR-P1(20), M111, 48952
• Files: NTL, TRIS, ATRI, USDOT, STATEDOT
• Created Date: Feb 22 2021 10:21AM