Can Sagrods be Regarded as Lateral Supports of Purlins

Function of sagrods in parallel purlin system is studied. Due to the small thickness of the cold-formed purlin, its web deforms locally at the sagrod point, slacking occurs in the sagrod, leading to noneffective sagrod. The zigzag arrangement of sagrods in the adjacent bays weakens dramatically the tensile stiffness of the sagrods further. On the other hand, the stiffness demand on the sagrod increases parabolically with the number of the purlins. Combining these factors, it can be concluded that the sagrods in purlin system have negligible effect of the strength and buckling capacity of the purlins. Proposals are presented on the layout of sagrod systems and cold-formed C sections shall be used as sagrods.