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Mid-America Transportation Center

Performance Characteristics of Posts Embedded in Soil

Final Report
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Researchers

  • Principal Investigator: Karla Lechtenberg (kpolivka2@unl.edu 402-472-9070)
  • Co-Principal Investigator: John Reid (jreid1@unl.edu 402-472-3084)
  • Co-Principal Investigator: Ronald Faller (rfaller1@unl.edu 402-472-6864)
  • Project Status
    Complete
    About this Project
    Brief Project Description & Background
    Temporary concrete barriers (TCBs) are connected and transitioned to many types of barriers. Unfortunately, little effort has been devoted to this issue. The only transitions previously developed have been between TCBs and safety shaped concrete barriers and TCBs and permanent concrete median barriers. Transitions between TCBs and guardrails have typically not been full-scale crash tested and may pose a serious hazard to motorists during an impact, Transitions between two barrier types generally are designed with the assumption that it is more critical to transition from a less stiff barrier to a stiffer barrier due to concerns for pocketing and snag on the stiffer barrier system. However, in the case of a TCB system, design of the transition can be more complex.
    Research Objective
    The objective of this research is to determine the post characteristics of post commonly used in transions through the use of physical dynamic testing for use during simulation modeling effort.
    Potential Benefits
    The research study will aid in the development of a transition design between TCBs and Midwest Guardrail System. This research will help determine post characteristics for use in concept development through simulation with LS-DYNA, evaluating the performance of various posts to be used in the new system. Additionally, the data and knowledge gained from this project will be used by the roadside design and research community for other guardrail systems and in other guardrail projects.
    Abstract
    The primary objective of this research study was to determine the post-soil impact reaction of W6x8.5 (W150x12.6) steel posts and 6-in. x 8-in. (152-mm x 203-mm) Southern Yellow Pine (SYP) posts, specifically along the weak axis. Five bogie tests were conducted on W6x8.5 (W150x12.6) A992 steel posts with a length of 72 in. with embedment depths ranging between of 24 and 40 in. (610 and 1,016 mm). Four bogies tests were conducted on 6-in. x 8-in. (152 mm x 203 mm) SYP posts embedded at depths ranging between 30 and 40 in. (735 and 1,016 mm). The target impact conditions were an impact speed of 20 mph (32.2 km/h) and an impact angle of 0 degrees creating weak-axis bending. The posts were impacted 24⅞ in. (632 mm) above the groundline and perpendicular to the web of the post. A compacted, coarse crushed limestone material as recommended by the Manual for Assessing Safety Hardware (MASH) was utilized for all tests. For each test, acceleration data was used to determine force vs. displacement and energy vs. displacement and failure mechanisms of the post-soil system were noted. Conclusions and recommendations were made that pertain to the embedment depth of posts impacted along the weak axis.
    Project Amount
    $ 60,000