Why is connection detailing a critical aspect of retrofitting steel structures for seismic resistance?

Connection detailing is a critical aspect of retrofitting steel structures for seismic resistance because connections are often the weakest link in a steel frame and can be prone to premature failure during an earthquake. Connections must be designed and detailed to have sufficient strength, ductility, and toughness to transfer forces between members and to accommodate the large deformations that can occur during seismic events. Poorly detailed connections can fail in a brittle manner, such as through weld fractures or bolt shear, which can lead to a sudden loss of load-carrying capacity and potentially trigger a progressive collapse of the structure. Retrofitting connection details often involves strengthening existing welds, adding supplemental plates or angles, increasing the number or size of bolts, or modifying the connection geometry to improve its load path and reduce stress concentrations. Proper connection detailing ensures that the connections can develop the full strength and ductility of the connected members, allowing the structure to dissipate energy effectively through yielding of the steel and preventing brittle failures that could compromise its seismic performance.