Critical Load and Ideal Brace Stiffness of Howe Trusses Fabricated from Opened and Closed-Section Truss Members

Abstract

Truss structures are susceptible to lateral deflection and torsion similar to column and beam. This research studied the critical load and brace stiffness of Howe trusses fabricated from opened and closedsection members and subjected to point load at midspan with and without bracing at midspan top chord. The mathematical models of the trusses were created and Eigenvalue Buckling Analysis was performed. According to the study, it was found that critical load has nonlinear relationship with brace stiffness and factors affecting the buckling load and brace stiffness include span length, equivalent out-of-plane moment of inertia, size and type of the cross-sections. Increasing of span-to-depth ratio results in decreasing of critical load and ideal brace stiffness, and number of panel and angle of diagonal members slightly affect the buckling capacity. Increasing of chord sizes is more effective than increasing size of web of truss members in both opened and closed-section trusses. Additionally, the critical load increases with the increase of equivalent out-of-plane moment of inertia and has linear relationship with PcrLb 2. The truss with closed-section members has higher critical load than opened-member truss at the same equivalent out-of-plane moment of inertia.