Fatigue Life Investigation of High Performance Mast Arm Base Plate Connections

Mast arm poles are typically connected to base plates using a structural fillet weld in a socket style connection. Previous research has shown that the fatigue performance of this connection is greatly dependent on the base plate thickness. Previous research has also indicated that the fatigue performance of a pole – to – base plate connection can be improved if a full penetration or external collar detail is used. This study was established to confirm these findings and to determine what variables affect the fatigue life of these higher performance details. Experimental tests were complimented with parametric studies using finite element models.

Results indicate that full penetration details can achieve excellent fatigue performance, and that both full penetration and external collar details perform better than a standard socket connection. It was found that the stiffness of the base plate played a role in the fatigue performance of the full penetration connection. Local bending in the pole occurs because of deflection of the base plate. This local bending creates high stresses in the pole near to the base plate, amplifying hot spot stresses at the weld toe of the full penetration connection, but not the hot spot stress in details that shift the hot spot stress away from the base plate.