Assessment of Load Sharing Members in an Anti-ram Bollard System Subjected to Vehicle Impacts

Open Access
Author:
Kinney, Scott Allen
Graduate Program:
Civil Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
May 06, 2013
Committee Members:
  • Dan Linzell, Thesis Advisor
Keywords:
  • Finite Element Modeling
  • Anti-ram
  • Bollard
  • Load Sharing
  • Steel Member Design
  • Parametric Study
  • Crash Testing
Abstract:
Due to the increased frequency, scale, and danger of malicious attacks carried out by Vehicle Borne Improvised Explosive Devices (VBIEDs), the need to adequately protect critical structures from these types of attacks continues to increase. Anti-ram bollards, which typically consist of vertical steel members embedded in concrete, have proven to be an effective and somewhat unobtrusive solution for protecting buildings and their occupants from vehicle impacts. However, there is still room to improve anti-ram bollard systems, and make them more efficient structural systems. One way to address these issues in urban areas is to utilize above-grade load sharing between the vertical steel bollards. Therefore, this study focused on the evaluation of above grade load sharing members in a steel anti-ram bollard system in an attempt to develop efficient load sharing mechanisms that improve the structure’s ability to resist vehicle impacts, while concurrently remaining aesthetically unobtrusive. The anti-ram system that was examined consists of two vertical, hollow structural shapes (HSS) embedded in a foundation consisting of HSS members embedded in reinforced concrete. The vertical HSS bollards were connected above grade using steel load sharing members that were intended to engage the non-impacted bollard to assist with energy dissipation. A computational study was completed using calibrated LS-DYNA finite element models to determine if effective, above grade, load sharing member configurations and designs could be established so that further optimization of the entire anti-ram system could be possible. It was found that effective above-grade load sharing could improve the crashworthiness of the anti-ram bollard systems that were studied. Of the designs that were investigated, the most efficient load sharing member design was a single HSS member connecting the vertical bollards near their tops.