Wind-driven rain on building faces and the driving-rain index

In areas of wind and rain, building faces are subjected to the wetting by wind-driven rain. In recent years, there is a growing concern on the amount of damage on buildings due to rain water. Unfortunately, unlike other civil and structural engineering problems, it has not been possible to quantify the design data. Driving-rain index (DRI) is available in some countries to give an indication regarding the wetness of a place. However, it does not give any information on the actual amount of rain water impinging onto a building. It was not until quite recently that a systematic method was established using computational fluid dynamics technique to calculate the amount of wind-driven rain (w.d.r.) on building faces. This paper first gives an outline of the method. Then the method is applied to a rectangular building where, together with the wind and rain data of the building site, the amount of w.d.r, on the building face is calculated. Thirdly, analysis is also carried out on the wind and rain data to obtain the DRI. Statistical relationships between w.d.r. and the DRI are investigated. Simplified expressions are proposed in the paper for w.d.r. prediction. The method is first applied to a building in Sydney, Australia for parameter evaluation. Validation of the method using data from Brisbane and Melbourne is then carried out. Application of the result to other places is also demonstrated. (C) 1999 Elsevier Science Ltd. All rights reserved.