Critical Imperfections for Beam Bracing Systems

Establishing the strength requirements for stability bracing generally requires large displacement analyses on imperfect systems. In computational studies on stability bracing, choosing the critical shape of the imperfection can be a difficult decision, particularly for beam bracing systems. There are a number of factors that affect the stability brace forces including the shape and magnitude of the imperfection, the distribution of the imperfection along the length, and the value of the moment at the location of the brace. To develop suitable bracing design provisions, it is necessary to determine the maximum brace forces that are likely to occur in typical applications. However, determining the shape and distribution of the imperfection that produces the largest brace forces can be complicated. This paper studies the effect of different imperfection schemes on the magnitude of the stability brace forces. Results are presented that demonstrate the impact of several imperfection parameters on the bracing behavior and recommendations are made for selecting the critical imperfection shape that maximizes the stability brace forces for beam bracing systems.