Fatigue Tests of Beams with Rectangular Web Holes

Fatigue tests on ASTM A36 steel wide-flange beams with rectangular web holes demonstrated the effect of stress concentrations at the hole corners on the fatigue strength of the beams. Under combined cyclic bending and shear forces at the hole, fatigue lives greater than 2,000,000 cycles were achieved without corner cracks when the corner radii were sufficiently large so that the cyclic stress range of the maximum elasticity boundary stress did not exceed 24 ksi. Good quality machine-burned hole surfaces were found to be sufficiently smooth to achieve lives of 2,000,000 cycles with no cracks at the boundary. Although additional work is required before detailed design provisions can be suggested, the tests indicated that for fatigue lives of 2,000,000 cycles, the corner radii of rectangular web holes in A36 steel beams should not be less than about 1 inch.