Bracing Requirements for Lateral Stability

Abstract

The forces induced in braces depend on the magnitude of initial imperfections (lateral bending and twist) and magnitude of applied loads. A method for calculating these forces is presented here. Shear stiffness of attached deck is taken into account. Calculations show that, for beams which derive their lateral stability mainly from the stiffness of the attached deck, additional bracing against rotation or lateral deflection is not able to achieve an important increase in the load capacity of the systems. In those cases, bracings employed merely to straighten the initial imperfections need not be very strong. In cases where decking cannot be counted on to stabilize the roof system, bracings should be designed for stiffness (sufficient to enforce a higher buckling mode) and checked by the methods presented here for required strength. The results are of value to designers of large flat wood roof systems;