PITA Fiscal Year 2008 Projects - Innovative Infrastructure System
   Assessment Technology

Fatigue Evaluation Of Arm To Mast-Arm Connections In Highway Sign And Signal Structures

The current AASHTO Specification for Highway Signs, Luminaires and Signal Structures include two variations of arm to pole connections in cantilevered sign/signal structures namely, gusseted and ring stiffened box connections. While limited fatigue test results indicate that the ring stiffened box connection can improve performance by reducing the out of plane distortion the pole wall, this connection involves costly fabrication. Data on field performance of the gusseted connection is sparse and the fatigue resistance of this connection was never established by fatigue tests. Preliminary fatigue tests indicate that the AASHTO design provisions for these connections are extremely unrealistic. As such, pre-emptive choice of the ring stiffened connection irrespective of the fatigue demand is not cost effective, particularly for the sheer volume of these structures in the inventory. It is proposed to establish the fatigue resistance of both type of connections by conducting fatigue tests on full size specimens and develop reliable and consistent design method for these connections. Pennsylvania Department of Transportation is developing standard connection details in sign/signal structures and establishing cost effective fatigue resistant armt to tube connections is important for effective utiliztion of state's limited transportaion resources. The research will develop new knowledge base in providing cost effective solution to Pennsylvania infrastructure, will promote student education by graduate student participation, and will help Pennsylvania to be in the forefront of engineering research and education.