CYCLONE RESISTANT STRUCTURE
Traditionally in our country individuals depending on their status, environmental conditions and local practices of the region are constructing different type of houses. the type of houses vary from non engineered houses such as huts with thatched roofs and mud walls, semi engineered houses such as buildings with tiles or asbestos cement sheets and bricks and stone masonary walls. and fully engineered buildings such as houses with reinforced cement concreate roofs and brick masonary walls. The construction techniques vary from place to place depending upon the conventional methods and local practices and available materials.
The uplift forces from cyclone winds can sometimes pull buildings completely out of the ground. In contrast to designing for gravity loads, the lighter the building the larger (or heavier) the foundation needs to be in cyclone resistant design. Ignoring this precept has led to some dramatic failure of long-span,
A common misconception is that the loss of cladding relieves the loads from building frameworks. There are several circumstances where the opposite is the case and where the wind loads on the structural frame increases substantially with the loss of cladding. Usually the weakness in steel frames is in the connections. Thus economising on minor items (bolts) has led to the overall failure of
the major items (columns, beams and rafters).
These are usually regarded as being safe in cyclones. There are countless examples where the loss of roofs has triggered the total destruction of un-reinforced masonry walls.
The key to safe construction of timber houses is the connection details. The inherent vulnerability of light-weight timber houses coupled with poor connections is a dangerous combination which
has often led to disaster.
3.5 Reinforced Concrete Frames