Fatigue Testing of Stiffened Traffic Signal Structures

Abstract

Based on in-service inspection of poles with traditional designs, the inventory of Wyoming Department of Transportation (WYDOT) exhibited approximately a one-third cracking rate. A ring-stiffened connection is presently used. Sixteen fatigue tests were performed on 12 ring-stiffened cantilevered traffic signal pole connections to quantify the fatigue resistance. Two pole sizes were tested in three loading configurations: in plane, out of plane, and diagonal. Cyclic loading was applied to produce stress ranges (SRs) at several levels up to 16 ksi in the main member, more than six times the SR observed during monitoring an in-service pole. The WYDOT stiffened connection appears to be adequate to resist Wyoming’s sustained winds that average approximately 12 mph in many locations. The possibility of using this connection with longer mast arms exists. Connection bolt fatigue failures were observed and may be the limiting fatigue design feature and important for inspection.