Experimental study of through diaphragm connection types under a column removal scenario

• Two through diaphragm connection types were tested in a column removal scenario.
• The modified bolted connection has a better load-carrying capacity.
• The failure modes at bottom flanges depend on the connection method.
• The modified bolted connection can delay the fracture occurrence at the bottom flange.

The beam-to-column connection has been identified as a key element for steel frame structures to maintain structural integrity under progressive collapse loading conditions. This paper presents full-scale laboratory tests of two steel frame assemblies with different connection details under a column removal scenario. One adopts a traditional field-welded through diaphragm connection, and the other uses a modified bolted through diaphragm connection. Test results demonstrate that the modified bolted connection can delay the fracture occurrence at the bottom flange; therefore the catenary action can be fully developed without completely losing the flexural resistance. For that reason, the beam-to-column assemblies can provide greater vertical resistance owing to combined flexural action with catenary action under large deformations. In this respect, the modified bolted through diaphragm connection is proved to have a better load-carrying capacity than the traditional field-welded connection and can be used to enhance the collapse resistance of steel frame structures.