# Design Wind Speeds for South Australia

### BASIC REGIONAL WIND SPEED

#### Typical Building/Structure

V[R] = 45 m/s [162 km/h]
mean return period 500 years
5% risk of exceedance for 25 year design life

#### Post Disaster Building/Structure

V[R] = 48 m/s [173 km/h]
mean return period 2000 years
1.25% risk of exceedance for 25 year design life

These wind speeds are typically as measured at an airfield 10m above the ground in terrain category 2. (M[z,cat]=1 by definition). These speeds are adjusted at a local site to allow for differences in terrain, and height, topography, shielding and direction. These differences are allowed for in AS1170.2 by multipliers: M[z,cat], Mt, Ms, Md.

Vzu = V[R] x M[z,cat] x Mt x Ms x Md

This is then converted into a site reference design pressure

qzu = 0.5 x density[air] x Vzu²

The site reference pressure is then multiplied by a pressure coefficient (Cp) to get the pressure experienced by a given surface of a building. These are the ultimate strength design loads. At ultimate strength, materials are permitted to deform but not fracture. When the load is removed the material remains deformed. Whilst do not expect a structure to collapse at the ultimate strength load, we do expect the building will no longer be suitable for purpose. The building will require major repair or replacing. At serviceability loads, the structure remains suitable for purpose. Expect a post-disaster facility to remain suitable for purpose when typical building is no longer functional. (eg. Hospital, CFS building) That is the serviceability load for a post disaster facility should at least be equal to the ultimate strength loads of normal buildings.