Cold-Formed Framing Procedures

The primary steel frame intervals of steel structures are fortified by ancillary framing components. They can act as flange bracing for the major structure assembly and, in reality, are secondary structures. An important support role of any building’s roof and walls is accomplished by these framing components and they aid in most all movement of the loading of any main frame. Secondary roof members, also known as purlins, help arrange the diaphragm of the roof. Secondary wall members, or girts, perform a critical role in buttressing the walls of the pre-engineered steel building. Eave struts, eave girts, or eave purlins perform the same task of both purlins and girts–the wall siding is provided by the webs and the roof panels by the top flange. Episodes of local buckling can befall cold-formed steel. This results when a segment of the compression flange and web may break under certain stresses. Distortional buckling, which comprises movement of the compression flange and nearby lip away from its planned position, may also demean the general support characteristics in this area. Supporting its portion of the load is impossible, therefore, for any part that fails. Careful thought should be given to cold-formed steel designing in order to avoid any buckling.

Also unfavorably exhibited in any web crippling process is the implementation of thin gauge component scheme. This normally occurs where the maximum pressures exist, along the support attachments. Bearing stiffeners near the supports help in remedying this problem by channeling the reaction force to the primary steel framework. These stiffeners are usually made up of channel pieces, clip angles, or plates. Any distortion of the purlin under stress on the rafter will occur as a web crippling event. Because of the reinforcing qualities of the particular clip angle attached to the purlin (including a bearing clip angle to operate as a web stiffener) the purlin will be prevented from distorting. By way of screws or bolts fixed directly to the stiffener, and from the stiffener into the rafter, the load is dispersed from the “Z” purlin web. Further stabilization of the purlin horizontally, if called for, is likely using alternative design styles.

The secondary segments prepared in steel structure erection are largely formed through a cold-formed steel framing approach. This form of steel design takes time to finish. Because the ingredients used are very flexible, deformations under load can occur. This usually will not happen, however, with its deeper hot-rolled steel equal.

By altering stress distribution during the cold-formed steel framework course, torsional integrity can also be affected. The result of even minimal amounts of stress can result in the buckling, bending and twisting loss of certain structural components. This problem can be avoided, however, with consistent minimal compressive stresses established in the system or with the adjoining of collateral buttressing.

With cold-formed processes where only certain locations of the shoring up members are necessary to endure compressive stresses, the concept of effective design width is employed. With satisfactory planning and fabrication objectives, this effective design width computation should have the highest degree of stress compiled in the calculation.