Crashworthy Foundations for Soil-Embedded Roadside Safety Hardware

Run-off-road crashes with soil-embedded safety hardware, such as luminaire poles and guardrail posts, are not well-understood for soil conditions other than MASH strong soil. The selection of an appropriate foundation depends on several factors including support structure type, structural stiffness, transmitted loads, soil properties, soil-structure interaction, groundwater conditions, and depth to bedrock. This project will primarily focus on the specific application of luminaire pole foundations. Current luminaire pole foundation designs commonly implemented by state DOTs rely on guidance from the American Association of State Highway and Transportation Officials (AASHTO) LRFD Bridge Design Specifications and AASHTO Standard Specifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals. These AASHTO guidelines are based on Broms’ method (1964) which relies on static analysis. Designs typically follow static load-based methods (i.e., Brom’s method), which has led to overdesigned foundations. Furthermore, there are no guidelines for design of crashworthy foundations embedded in soils other than medium to dense, dry soil. AASHTO guidelines do not address crashworthy foundation design for sites with “weak” soil (i.e., silts, soft clay, peat, organic soil) and/or soil with high moisture content. Geographic soil variability as well as seasonal variations in groundwater conditions across the country call for research to enable cost-effective and safe soil-embedded safety hardware for an extended array of specific site conditions (i.e., weak, and/or saturated soil) considering more realistic and accurate dynamic loads rather than static loads. The objectives of this research project are to (1) evaluate adequacy of state DOTs’ existing practices, (2) enhance existing modeling methods for soil behavior during vehicle impact events, and (3) develop preliminary guidelines for luminaire foundation depth accounting for soft and/or saturated soil. This project will complement a current project at Midwest Roadside Safety Facility (MwRSF) which aims to develop design guidance for crashworthy luminaire pole foundations in the state of Alaska, satisfying Manual for Assessing Safety Hardware (MASH) safety criteria.

Language

• English

Project

• Status: Active
• Funding: $351788
• Contract Numbers:

  69A3551747107

• Sponsor Organizations:

  Office of the Assistant Secretary for Research and Technology

  University Transportation Centers Program
  Department of Transportation
  Washington, DC  United States  20590
• Managing Organizations:

  Mid-America Transportation Center

  University of Nebraska-Lincoln
  2200 Vine Street, PO Box 830851
  Lincoln, NE  United States  68583-0851

  University of Nebraska, Lincoln

  Midwest Roadside Safety Facility
  2200 Vine Street, Whittier Building
  Lincoln, NE  United States  68583-0853
• Performing Organizations:

  University of Nebraska, Lincoln

  Midwest Roadside Safety Facility
  2200 Vine Street, Whittier Building
  Lincoln, NE  United States  68583-0853
• Principal Investigators:

  Steelman, Joshua

• Start Date: 20200901
• Expected Completion Date: 20220228
• Actual Completion Date: 0
• USDOT Program: University Transportation Centers Program
• Source Data: RiP Project 91994-74

Subject/Index Terms

• TRT Terms: Crashworthiness; Depth; Foundation soils; Guidelines; Luminaires; Ran off road crashes; Roadside; State departments of transportation; State of the practice; Support poles
• Identifier Terms: AASHTO Manual for Assessing Safety Hardware
• Geographic Terms: Alaska
• Subject Areas: Design; Geotechnology; Highways; Safety and Human Factors; Terminals and Facilities;

Filing Info

• Accession Number: 01766143
• Record Type: Research project
• Source Agency: Mid-America Transportation Center
• Contract Numbers: 69A3551747107
• Files: UTC, RIP
• Created Date: Feb 26 2021 10:53AM