Evaluation of Redesigned Slipbase Sign Support Using Crash Simulation

Improvement in computer hardware and Finite Element (FE) software have made it possible to simulate complex phenomenon such as the behavior of automobiles and roadside hardware during crashes. In this paper, the performance of a modified 3"x3" slipbase sign support system is evaluated using Finite Element simulations. The first task of the study consisted of developing an accurate finite element model of the new 3"x3" slipbase. This is achieved by using full-scale tests that were conducted on an 8"x8" slipbase at 32 and 96 km/hr (20 and 60 mph) to validate an 8"x8" slipbase FE model. Once an accurate model of the 8"x8" slipbase is obtained, the exact modeling techniques used in developing this slipbase are used to construct a FE model of the 3"x3" slipbase. The second task of this study involved using the 3"x3" slipbase model to predict its behavior in a 32 and 96 km/hr (20 and 60 mph) impacts. The predictions showed that modified 3"x3" slipbase passes the NCHRP 350 safety criteria. These predictions were compared to full-scale tests that were conducted subsequent to the simulations. It was found that the FE model accurately predicted the full-scale test results. The final task of this study consisted of conducting a parametric FE analysis to determine the maximum clamping force that can be applied to the 3"x3" slipbase without causing it to fail the NCHRP 350 safety criteria. The computer simulation parametric study revealed that the bolts can be clamped up to their yielding point and the slipbase will still pass the safety criteria of acceptable vehicle velocity change. Working Paper NCAC 2003-W-002 November 2003