Rainwater Ponding on Beam-Girder Roof Systems

An analytical study of the phenomenon of rainwater ponding on beam-girder roof systems has been performed. For roof systems with nondeforming boundaries and no interior columns, formulas are presented for determining maximum moments in the system due to both live and dead loads and ponding loads. These formulas are in a form suitable for design office use and offer the advantage of enabling the designer to directly check stresses instead of the awkward procedure of comparing stress index parameters as now commonly done in practice. The consideration of a dish deflected shape in many cases will more accurately model the actual configuration and is treated for the first time in this paper. The use of the formulas presented herein will generally lead to more economical designs than heretofore available for ponding of two-way roof systems.