Do you often utilize chevron braced frames in your steel building designs? The flexible geometry of a chevron brace makes these configurations very common because of the ability to shift the workpoint of the bracing connection along the length of the frame beam; thus allowing for wall openings in the structural wall. However, the Chevron Effect was more recently identified as an issue in the design of frame beams in a chevron braced frame, and, if not considered, can result in an unconservative beam design when the connection is designed in isolation from the frame.
In May 2017, Patrick Fortney, PE, SE, from the University of Cincinnati, gave an SE University presentation on The Chevron Effect – A Paradigm Shift in Approach to Analysis. During his talk, Patrick referred to previous published research which discusses the topic and derives useful formulas for EORs and connection designers.
The two papers which formed the basis of the presentation were developed by Patrick Fortney and William Thornton, and published in 2015 and 2017. The first publication was released in 2015 entitled The Chevron Effect – Not an Isolated Problem. This paper reviews the basics of the chevron effect and gives useful rules of thumb and example problems. Since the final geometry of the chevron brace is not always known during the design process, some rules of thumb were provided to help EORs to help consider the brace forces when designing the frame beam. Click on the following video to hear Patrick explain some rules of thumb to estimate the gusset plate length and beam depth for chevron braced frames.
The second paper was released in 2017 and was intended as a follow-up to the previous paper to provide the EOR and connection designers a consistent design method to use with relatively straight forward closed form equations based on first principles. The Chevron Effect and Analysis of Chevron Beams – A Paradigm Shift provides the complete design process and formulas necessary to effectively consider the chevron effect in the design of chevron beams.
Using these two papers as a reference, engineers and connection designers now have a consistent method for the design of chevron braced frame beams and their connections. The formulas presented in these papers are a straightforward method for considering both the global and local effects the brace force can induce in the chevron braced frame.