Boundary Conditions for Water Tightness Testing Based on Pareto-Front Analysis

The predominant boundary conditions for evaluating watertightness of a wall are pressure difference across and water spray rate on the wall. However, the relation between these key climatic effects as defined in standards or actual weathering conditions remain, as yet, undefined. A comprehensive calculation method to define correct boundary conditions based on extreme value analysis of wind and rain events has been developed, however, the method relies, to an extent, on the statistical independence of these events. Hence, the calculation of the return period for wind-driven rain loads on buildings has up to now required unverified and perhaps uncertain assumptions concerning the co-occurrence of wind and rain events; this necessarily affects the calculation of results for wind-driven loads. In this paper a new methodology is presented that was developed to derive boundary conditions for watertightness testing based on Pareto-front analysis of meteorological data. The method takes into account actual combinations of rain and wind without making assumptions regarding the co-occurrence of wind and rain events, and thereby allows calculating realistic boundary conditions for different return periods. This method was developed based on only one climate database, and necessarily should be validated for a broader range of climates and return periods. As well, the Pareto-based methodology only offers information for the specific averaging period of a given climate database. The conversion to shorter time periods for both wind and rain again introduces assumptions on the co-occurrence of extremes.