Instructional model for understanding roof ponding
Professor emeritus of Delft University of Technology
Volume 51 (2006), issue 2/3, of HERON was a Special Issue 'Ponding of Roof Structures' with contributions from the universities in Delft and Eindhoven and parties from the business community. It appeared that a major difference occurs between very flexible flat roof systems and stiffer ones, and also behaviour differs between flat roofs with and without slopes. At that time, the present author discussed the matter of slope-less flat roofs with the aid of a simple model, but applied a rather complicated model for sloping roofs. Lecturers need a simple instructional model that covers all possible roof systems, with or without slope, both very flexible and rather stiff ones. Such an instructional model can be devised as an extension of the simple model in the 2006 issue. In addition, it is discussed how to prevent unstable computations for roof structures not failing by strength, but by stability. The proposed solution is to perform the analysis volume-controlled instead of control by water level.
Key words: Education, instructional model, ponding, water accumulation, roof safety