Development of cyclic bending torsion testing equipment for fatigue strength evaluation of steel pole

To achieve reliable logistics, the construction of transportation infrastructure is essential, and the safety guarantees of various types of poles are required as well. A cyclic bending loading test is commonly conducted to investigate the fatigue strength of lighting poles. In the actual service environment, the loading mode may be not only simple bending but also torsion or a mixture of both. In addition, the base plate of the lighting pole is strengthened by a rib weld, and it is essential to understand the cracking from the stress concentrated point at that section and to obtain the fatigue property data. In the present work, we designed and developed a fatigue testing system that can conduct cyclic loading using two hydraulic actuators in a desired loading mode to the actual lighting pole. The fatigue strength property investigation in an arbitrary loading mode was made possible by controlling the movement of the two hydraulic actuators. The effect of the shape of the strengthening ribs on the fatigue strength of the base of lighting poles was investigated using two different rib shapes, and it was confirmed that the U-shaped ribs had a better fatigue life than the triangular-shaped ribs.