Length of Need and Minimum System Length for F-Shape Portable Concrete Barrier

Portable concrete barrier (PCB) systems are often used to redirect errant vehicles through a combination of inertial resistance, lateral friction loads, and tensile loads developed from the mass and friction of the barrier segments. State departments of transportation (DOTs) and other end users may wish to utilize minimal length PCB installations to shield a hazard or work zone or limit the number of barriers required on the upstream and downstream ends to reduce overall system length. However, concerns with the performance of shorter PCB installations include increased lateral deflections and working widths and barrier pocketing. Additionally, no impact testing has been performed near the upstream or downstream ends of the free-standing PCB system to determine the limits of the length of need (LON) of the system. These impacts may increase the potential for gating through the system, pocketing, rapid deceleration, and/or vehicle instability. The objective of this research study was to investigate and evaluate the safety performance of a previously developed F-shape PCB system to determine minimum system length and the number of barriers required for the beginning and end of the LON. LS-DYNA simulation modeling was applied to determine potential beginning and end of LON points on reduced system lengths to select a configuration for full-scale testing and evaluation of a minimum length PCB system. A 100-ft long PCB installation was selected, and full-scale crash testing was conducted on the beginning and end of LON of the reduced length system. Test no. NELON-1 was conducted to MASH test designation 3-35 criteria on the beginning of LON of the 100-ft long PCB installation, and the vehicle was safely redirected. Test no. NELON-2 was conducted to modified MASH test designation no. 3-37 criteria on the end of LON of the 100-ft long PCB installation, but the test was deemed a failure as the vehicle demonstrated a roll angle in excess of 75 degrees. Review of the crash test results suggested that a nine barrier or 112.5-ft long PCB installation would perform acceptably.