Strength and Design of Open Web Steel Joists with Crimped-End Web Members

Open web steel joists are prefabricated truss-type members economical for use in floor and roof support systems for lightly loaded structures. Joists are designed in accordance with the specifications and standard load tables published by the Steel Joist Institute. An experimental study was conducted to determine strength and general flexural behavior of open web steel joists having L1 in.×1 in.×1/8 in. single angles with crimped ends for web members. Crimping the ends of the web members allows them to be aligned symmetrically with respect to the centerline of the joist, thereby eliminating the effects of eccentric loading in the web members. The purpose of the tests was to observe overall flexural behavior based on failure loads, deflections, and strains in the top and bottom chords. Outcomes from the study show that there is considerable rotational restraint in the web members at the panel points. Based on the parameters tested, an effective length factor is recommended that is less than that corresponding to a pin ended column. Finally, using the more accurate measure of rotational stiffness at the joints, revised service loads are recommended.