Influence of Base Plate Flexibility on the Fatigue Performance of Welded Socket Connections

Abstract

This study investigates the effect of base plate flexibility on the behavior and fatigue performance of welded socket connections commonly used in sign support structures. The results of a three specimen static load testing program, extensive finite-element analysis, and parametric study are discussed. Results clearly show that base plate flexibility, primarily base plate thickness, has a major influence on the stress distribution in the tube wall adjacent to the welded socket connection. Currently, AASHTO gives no specific guidance on the design of the base plates for sign support structures that explicitly address flexibility. Increasing base plate thickness is shown to be a very effective method to improve the fatigue resistance of this detail. Based on this trend, a simple procedure that incorporates the influence of base plate flexibility into the infinite life, nominal stress approach to fatigue design is proposed.