This paper reports a construction survey of steel roof structures in Tohoku Prefecture. The research is based on a basic database of the cross-sectional performance of beams and non-structural members from the total of 1345 steel roof structures in Tohoku. Also, this paper clarified the bracing effect performed by the non-structural members on lateral buckling strength of main beams using the relationship between the stiffening capacity of large beams and nonstructural members. The modified lateral buckling slenderness ratio considering the stiffening effect of nonstructural members may be in the range of 100 to 180.
