Editorial

摘要

Ponding of flat roofs is the phenomenon that a roof deflects under rainwater loading, which means that additional rainwater runs to the deflected spot, giving more loading and thus more deflection, etc. For well-constructed roofs, equilibrium is reached and the roof is able to carry the loading. Collapse may occur for roof structures which are too flexible, have too high emergency overflows or insufficient slope. Collapse of flat roof structures under heavy rainfall and subsequent rainwater loading due to ponding of the roof has frequently happened in The Netherlands.