Determination of wind-driven-rain intensity on building faces

The weather resistance design of building facades requires adequate knowledge on the wind and rain environment around the building. It is important to know both the wind speed as well as the associated rainfall intensity impinging onto the building faces. However, wind-driven-rain around a building is complicated and it is a topic not well understood. Usually with speed and rain intensity are considered separately and their values for weather resistance design are just guesses based on engineering experience. A method is proposed in the present paper, where wind-driven-rain intensities impinging on building faces are calculated taking into account all the relevant factors such as the interactions between wind, rain and building, and also the joint probability of occurrence of wind and rain. The method comprises the following steps: (a) using computational fluid dynamics method to calculate the flow pattern around a building, (b) raindrop trajectories in the flow field are obtained by solving the force equations, (c) obtain the probability of joint occurrence of wind and rain from the analysis of meteorological records, (d) rainfall intensities on building faces are computed as a function of return period by coupling (b) and (c). The method is applied onto a rectangular building located in Sydney and the extreme wind-driven-rain intensities on various portion of its faces calculated.