Framing for Steel Buildings

STEELBUILDING.COM designs and supplies pre-engineered "rigid frame" steel building systems, which offer owners and builders a number of advantages. They are relatively inexpensive yet incredibly strong. The simple bolt-together design can be assembled quickly without any specialized carpentry, masonry or welding skills. Best of all, the versatile rigid-frame design can be adapted to serve a variety of needs from standard metal buildings to metal agricultural buildings and more.

The defining feature of a rigid-frame steel building is its steel backbone of I-beam main frames. Each frame is made up of two or more columns supporting a rafter that runs laterally from one side of the building to the other. Spaced at intervals between the two endwalls, the main frames bear most of the load of the building. Depending on design considerations, STEELBUILDING.COM's main-frame components may be "hot-rolled" (made by extruding molten steel through a mold) or "built up" (made by welding plate steel), depending on what you need for your metal building package.

In most steel building designs, endwall frames only support half the load of a main frame. In such cases, we use lighter, less expensive "bearing" or "half-load" frames. Depending on engineering and economic considerations, our endwall rafters and columns may be either hot-rolled or "cold-formed" (shaped by running coils of steel through a former). At times, it is advisable to use a full-load rigid frame on an endwall. For example, an "expandable" endwall is designed to function as an interior frame if the steel building is extended beyond it.

Each space or interval between the frames of a steel building is a "bay." In the illustration below, a 100' long building has been divided into four bays by spacing the frames 25' apart (4 x 25' = 100'). This configuration is described as "four bays at 25." A 100' building could just as easily be configured with five bays at 20 (5 x 20' = 100') by adding another main frame. Often, using fewer frames reduces the weight and, hence, the cost of a metal building, but this is not always the case. It depends on the size of the building, the width of the bays, the load requirements and many other factors. Our online design and pricing system offers only symmetrical bay spacings; however, you can request a special quote for mixed bay configurations.

The spacing of endwall columns is also important because it determines the possible sizes and locations of framed openings on the endwalls. Note: Bays should not be confused with framed openings (see features page). A bay can have more than one opening in it or none at all.

Secondary framing includes the wall girts, roof purlins and eave struts. Although these cold-formed components carry little of the overall load of the building, they do support the wall and roof panels, transfer loading to the frames and help stabilize the steel building. In most cases, we determine the size, shape and placement of individual components based on engineering requirements, but we can often adjust a design to accommodate specific needs. For example, on endwalls, the girts normally run flush with the columns ("inset" or "flush mount"), but on sidewalls they overlap on the outside ("outset" or "bypass"). However, we can usually change either or both of these conditions to suit the buyer.