Evaluation of Texas Grid-Slot Portable Concrete Barrier System (0-4162-1)

The crash performance of the TxDOT Type 2 precast concrete traffic barrier (PCTB(1)-90) with joint type A is unproven with respect to the National Cooperative Highway Research Program (NCHRP) Report 350 guidelines. Under this project, TTI researchers and TxDOT engineers worked together to evaluate the crash performance of this barrier system and determine if cost effective modifications can be made to the barrier to meet NCHRP Report 350 criteria and limit dynamic deflections to practical levels. The research team performed various analyses to help assess the ability of the selected barrier systems to meet NCHRP Report 350 impact performance criteria prior to conducting the full-scale crashtesting. Computer simulation techniques were used to support the analysis efforts. The simulation provided a more detailed understanding of the three-dimensional impact response of the barrier design. The program utilized in the computer modeling efforts was LS-DYNA. LS-DYNA is a general-purpose, explicit finite element code used to analyze the nonlinear dynamic response of three-dimensional inelastic structures. This code is capable of capturing many of the complex interactions that occur when a vehicle impacts a roadside safety structure. Limitations in the ability of existing material models to accurately capture concrete fracture and failure led to some simplifying assumptions regarding the model of the grid-slot connection. Nonetheless, the simulations assisted in the impact performance evaluation of the existing and modified designs. During the project, several retrofit connection designs were conceptualized for the objective of reducing dynamic barrier deflections. TxDOT engineers and TTI researchers developed these design modifications jointly. When developing these retrofit design options, factors such as impact performance, cost, ease of field installation, and aesthetics were considered. Three full-scale crash tests were performed to evaluate the safety performance of the selected barrier systems. The purpose of the testing was to assess compliance of the "grid-slot" portable concrete barrier (PCB) with NCHRP Report 350 and examine alternatives for reducing dynamic deflection. The tests were performed in the order of the cost effectiveness of the barrier modifications to investigate the relative improvement in crash performance. All three crash tests satisfied NCHRP Report 350 evaluation criteria. Although each barrier configuration met NCHRP