Hysteretic behavior of existing and retrofitted concrete-encased riveted stiffened seat angle connections

Typical riveted stiffened seat angle connections taken from a 1910 building were tested to investigate their actual hysteretic behavior and potential moment resistance and to determine how they could be efficiently retrofitted with a minimum amount of structural modifications. In that building, columns had been embedded in low-strength concrete, as typically done at the turn of the century as a fireproofing measure, and connections were tested with that fireproofing concrete left in-place. This study shows that, in their as-is condition, these existing connections can develop a considerable moment resistance, but their pinched hysteretic curves indicate that they have a relatively low energy dissipation capability. Embedment of connections in the concrete is found to be of little benefit. A steel-band/fuse-plate retrofitting scheme is proposed to improve the connectionʹs hysteretic behavior. This retrofit technique permits the connection strength and ductility to be enhanced, without requiring removal of the column concrete cover. The effectiveness of this retrofit technique is experimentally demonstrated.