Abstract: A diaphragm for use in a building structure includes a fluted deck supported by horizontal support beams and includes a contoured shear resisting member disposed internally from an end of the fluted deck for stiffening the fluted deck against horizontal shear loads imposed upon the diaphragm. The bottom flutes of the fluted deck overlie at least one horizontal support beam with which the shear resisting member is associated. Both the shear resisting member and the associated support beam extend perpendicular to the flutes within the fluted deck. The shear resisting member includes a substantially planar horizontal flange which spans a number of the top flutes of the fluted deck, and a first series of welds secures the upper flange of the shear resisting member to the underlying top flutes. A series of spaced tabs extend downwardly from a side edge of the upper flanged, each spaced tab lying within a trough of the fluted deck.