Left: At the Leslie Dan Faculty of Pharmacy in Toronto, ON, Canada, a coped connection provides a level surface for the installation of the floor deck in spite of the difference in size of the beams that are framing into the girder. The variation in the number of bolts in the connections is a clear indication of the differences in shear forces to be transferred. Right: Framing infers a clear hierarchy for the transfer of loads through the building. The addition to the Art Gallery of Ontario in Toronto, ON, Canada by Frank Gehry, uses steel framing for the extension to the gallery. The very deep beam is a transfer beam that is permitting a large clear-span exhibit and gathering space. Holes are cut into the beam to permit the passage of services. Additional steel is welded around the cutouts for reinforcement of the web of the beam. Major steel floor beams frame into the transfer beam using coped connections. Smaller beams carry the future floor loads into these. This type of framing makes it possible to apply simple structural analysis in spite of its complexity.
Framed connections using standard wide-flange sections are commonly used in structural steel that is not intended to be architecturally exposed. Architecturally exposing the steel will add extra detailing requirements for alignment as well as precision. Aesthetics might require that both the top and bottom chords align or that the range of steel sections be standardized, to create a more uniform appearance – even if this means that the sections might be larger or heavier than required for loading purposes.
Left: The large brise soleil at the Las Vegas Courthouse, NV, USA, designed by Cannon Design uses deep wide-flange sections to create the structure for the grid. Smaller steel sections are used as infill to provide shading. Exposing the steel places the priority on a uniform appearance. Right: The grid requires that the deep beams be given coped connections for both the top and bottom chord to achieve the appearance of a uniform, non-directional grid.
GIRDER- OR BEAM-TO-COLUMN CONNECTIONS Girders and beams transfer the loads that they have received from the floor to the columns. The connection can be made either to the flange of the column or to the web, depending on the orientation of the column, which is a function of the structural layout. Columns are generally oriented so that the dominant wind load strikes perpendicular to the flange of the column. Connecting to the flange provides easier access for the ironworkers to tighten bolts. Beams and girders will be lifted into position by a crane, the matching holes in the angle connectors are aligned with a slug wrench, and the bolts inserted. For some projects temporary angle “seats” will be attached to the column to provide a ledge upon which to sit the beam, allowing the crane to detach earlier and to speed up erection. These seats can be removed after the connection is complete, or remain in place to stiffen the connection.
– STEEL CONNECTIONS AND FRAMING TECHNIQUES