Tackling the storm

CYCLONE RESISTANT BUILDING CONSTRUCTION

Cyclones have been an inescapable situation in India, especially in the eastern states of Odisha, West Bengal, and Andhra Pradesh. This calls for the construction of cyclone-resistant buildings in cyclone-prone areas to avoid loss of life and property.

Low-lying coast areas, river floodplains, and sea-shore areas are highly vulnerable to cyclones. Certain settlement pattern even causes "funnel effect" which results in greater damage.

While it's a common belief that heavier buildings are safer, in reality, a well built and engineered house provides better safety. Minimum standards for the design, construction, and performance of buildings to withstand extreme climate-related natural hazard events depending upon their locations should be set.

We know cyclones are beyond human control but measures can be taken to reduce the loss of lives like evacuating people to safe areas, quick recovery of important facilities, etc. Although the main focus should be a modification in the design of building in cyclone-prone areas to minimize materialistic loss also. Some of them are discussed below : 

Roofs:

Probably the most common area of failure during cyclones is roofs. The ways of protecting roofs are: 

• Patio roofs and verandahs to be built as a separate structure from the roof; 
• Securing the main ridge using gussets, collar ties, and metal straps; 
• Use of proper drive screws which go at least 50 mm in the purlin 

Foundation:

Foundation of any structure needs to be strong enough so that it can prevent the structure from blowing away.

The ways of protecting foundations are: 

• Know-how of the type of soil so that the foundation is laid at a proper depth; 
• Knee bracing to be adopted over full diagonal bracing as it allows the flow of debris; 
• Proper bracing to be done in both the principal directions of the stilts.

Doors and windows:

The openings for light or ventilation acts as a stress concentration due to the erratic distribution of winds. Ways to reduce it are 

• Opening on the windward side to be compensated by opening on the leeward side.
• The sum of the length of the opening should be less than half of the width of the structure.
• The distance of the opening from the inner corner should be greater than the one-sixth length of the height of the structure.

Walls:

Walls face the utmost load from all sides during a cyclonic storm and the whole structure depends on the strength of walls. The ways to reduce damage are :

• Walls reinforced with concrete bands, vertical reinforcing bars, and lateral ties.
• Buttresses should be provided for lateral load resistance of long walls 
• Roofs and foundation should be properly braced and anchored with the walls 

Planning of settlements:

• Row arrangements of houses to be avoided to avoid extreme wind pressures on the windward side of outward houses.
• Trees should be arranged in a zigzag manner to reduce wind pressure.
• Houses should be built on stilts or artificial earth mounds in the high-velocity wind region.
• Symmetrical designs of houses should be preferred mostly rectangular to avoid unequal pressure of the wind.
• Strong trees like coconut trees are often preferred in the direction of sea to reduce the wind pressure of cyclones.

A destructive cyclone leads to huge storm surge and high-speed wind gusts. Under these actions buildings designed incorrectly will not perform well and surrenders. Some new technology like cloud-seeding and Dyn-o-gel can be used to reduce the strength of the storm to a considerable extent.

WRITTEN BY - Mohit Kumar Sahu