– [Article provided by the Structural Building Components Association] –
The truss industry maintains that the design of truss roof and floor system permanent restraint/bracing is the responsibility of the building designer.
System permanent bracing covers the entire structure and all reinforcing/bracing element interactions. An exception to this is identifying the locations of compression web restraint. Compression web restraint is different because, as designers and manufacturers, we are taking responsibility for the design and structural performance of the individual components. We must make certain that each truss is designed and built to support the loads stated on the truss design drawing.
Compression web restraint generally takes the form of continuous lateral web restraint. If it is required on a truss, the Truss Designer will point out the location on the Truss Design Drawing. To avoid this from being overlooked in the field, manufacturers may also indicate the location of the restraint directly on the truss by using a SBCA/TPI PERMANENT LATERAL RESTRAINT tag (Figure 1). This lateral restraint stabilizes the web, decreases its tendency to buckle under compression forces and allows the web to reach its full design capacity.
What happens when permanent lateral restraint is not possible to use for the given truss system or individual truss type? The following question deals with alternatives to continuous lateral restraint for webs.
QUESTION: What is T-Reinforcement? What is it used for?
ANSWER: T-reinforcement takes the place of continuous lateral restraint (Figure 2). With T-reinforcement, the web in question must be reinforced along approximately 90 percent of its length or extend to within 6 inches of the end of the member, whichever is greater. The reinforcing material is applied to the web such that in cross section it forms a “T” with the web (Figure 3). Other variations on this type of reinforcement are I-reinforcement (Figure 3), L-reinforcement (Figure 4), U-reinforcement (Figure 4) and scab reinforcement (Figure 5).
The end result of continuous lateral web restraint or T-reinforcement is to stabilize the web so that it will be able to transfer the compression loads for which it was designed. Refer to Building Component Safety Information (BCSI-B3) or standard details from the Truss Designer or Building Designer for minimum attachment of the required restraint/reinforcement to the truss member (see Table 1).
Article Source: SBCA has been the voice of the structural building components industry since 1983, providing educational programs and technical information, disseminating industry news, and facilitating networking opportunities for manufacturers of roof trusses, wall panels and floor trusses. SBCA endeavors to expand component manufacturers’ market share and enhance the professionalism of the component manufacturing industry. Visit online at sbcindustry.com. RB
READ THIS ARTICLE for a simplified explanation of T-reinforcement (or T-bracing) and its benefits.