Stability of Trusses Subjected to Ponding Loads

by Ta Chao, (A.M.ASCE), Asst. Prof.; Dept. of Arch., Carnegie-Mellon Univ., Pittsburgh, PA,

Serial Information: Journal of the Structural Division, 1973, Vol. 99, Issue 6, Pg. 1327-1332

Document Type: Journal Paper


It has been observed that flat roofs may fail due to ponding loads during rain storms. Since the load due to the weight of the ponded rain water increases as the deflection of the roof increases, roof structures without sufficient rigidity may be unstable and deflect progressively and finally collapse during a sustained rain storm. Flat roofs supported by one-way beams subjected to ponding loads have been studied by several investigators. However, roofs supported by flat trusses such as open web joists were not treated in those studies. The purpose herein is to obtain the stability conditions for one-way truss roofs under ponding loads and to examine their general characteristics. The analysis makes use of a difference formulation introduced by Dean and Tauber for the study of uniformly loaded trusses.

Subject Headings: Roofs | Rain loads | Trusses | Load factors | Failure loads | Storms | Rain water | Structural deflection

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