Behaviour of knife plate connections for tubular bracing

Twelve full-scale knife plate bracing connections were tested to destruction under cyclic tension loading between zero and a prescribed maximum stress level. As expected, fatigue life decreased as the maximum tension stress level increased. It was found that the length of gap between the forward edge of the knife plate and the end of the HSS slot had little or no effect on the fatigue life. The length of weld attaching the knife plate to the slot in the HSS did not affect the fatigue life of the connection as long as it was adequate to develop the required static strength of a specimen. Specimens tested with different HSS wall thicknesses and knife plate thicknesses followed the trend of the other specimens. Cracks formed in the walls of the HSS at the forward edge of the knife plate in the slot at a relatively low number of cycles. This number varied from as low as 200 at a member maximum average stress of 260 MPa to a high value of 8 000 at a member maximum average stress of 101 MPa. The number of cycles causing ultimate fracture varied from 4 061 at a member maximum average stress of 227 MPa to 184 591 at a maximum average stress of 101 MPa.