Analysis and Evaluation of Slip Base Aluminum Single-Post Sign Supports under Manual for Assessing Safety Hardware Safety Performance Criteria

Abstract

Single-post sign supports are commonly used near to roadways. Signs can assume various configurations, yet few full-scale crash tests have been conducted to date to investigate crash performance of sign supports under current American Association of State Highway and Transportation Officials (AASHTO) Manual for Assessing Safety Hardware (MASH) criteria. This study investigated crash performance for aluminum, slip base, single-post signs under MASH criteria to determine critical configurations and develop prospective assessments of crashworthiness. These systems were supported by a four-bolt slip base and mounted on a 4 in. diameter aluminum post. Two full-scale crash tests were performed to evaluate performance of a system with a 4 × 4 ft sign panel under MASH test Nos. 3-61 and 3-62, in which the slip base activated and released the sign in a predictable manner. Safety concerns for the tested signs were raised by sign penetration through the rear window and excessive roof crush during MASH test No. 3-61. LS-DYNA models were developed and validated against test results. LS-DYNA simulations were conducted on four sign configurations to represent a range of sign panel sizes and design heights to analyze critical characteristics of single-post signs. Simulations were also conducted with increased design height to explore preliminary options for improving the performance of sign supports. Generally, signs with centroid heights at least 10 ft were deemed to have high potential of passing MASH Test Level 3 (TL-3) criteria, but it was recommended that the critical sign configuration be modified to raise the sign cluster centroid from a design height of 9 ft to 11.5 ft or greater.