Fatigue risks in the connections of sign support structures: phase I

Abstract

Wisconsin sought to assess the risk of fatigue-induced fracture in its existing sign support structures designed before the latest AASHTO specifications that included fatigue design. A framework for assessing fatigue-induced fracture risk is developed and detailed synthesis of fatigue testing of connections is conducted. Statistical analysis of tests conducted since 1970 is made and models for characterizing uncertainty in the fatigue life of these connections are proposed. Recommendations regarding further fatigue testing (specimen configuration, number and stress range) are given. Statistical models for wind speed and direction are developed using historical records obtained through the National Climatic Data Center for eight cities within the state of Wisconsin. Nonlinear finite element analysis of a typical mast-arm-to-plate connection with octagonal mast arm is conducted using various configurations of bolt pretension. Recommendations regarding the impact of loose bolts on the distribution of normal stress within octagonal mast arms are provided and comparison to AASHTO design specification procedures is made.