Abstract: A girder-like runner for use with fire-rated suspended ceiling structure is disclosed. The runner is provided with a bottom flange, an interrupted top bead, and a web including a diamond-shaped expansion member. A lower web portion adjacent the flange is formed with two opposed lipped ledges. Buckling forces caused by first-induced thermal expansion force the web expansion member to deform outwardly into a foreshortened diamond shape. The forces also cause the ledge web portion and the flange downwardly in a controlled, predetermined manner which retains runner strength.