The table below is based on damage resulting from the impact of Cyclone Tracy on Darwin in 1974.
|
Damage class |
Worst damage feature |
Damage repair index |
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|
Elevated houses |
Low-set houses |
One-storey non-residential buildings |
Top-floor of multi-storey buildings |
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|
Brick walls |
Asbestos cement walls |
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|
1 |
Negligible |
0.00 |
0.00 |
0.00 |
0.00 |
0.00 |
|
2 |
Missile damage to cladding or windows |
0.05 |
0.05 |
0.05 |
0.05 |
0.05 |
|
3 |
Loss of half roof sheeting |
0.10 |
0.10 |
0.10 |
0.10 |
0.10 |
|
4 |
Loss of all roof sheeting |
0.20 |
0.20 |
0.15 |
0.15 |
0.20 |
|
5 |
Loss of roof structure |
0.25 |
0.25 |
0.20 |
0.20 |
0.25 |
|
6 |
Loss of half walls |
0.50 |
0.65 |
0.60 |
0.60 |
0.55 |
|
7 |
Loss of all walls |
0.75 |
0.90 |
0.90 |
0.90 |
0.80 |
|
8 |
Loss of half floor |
0.85 |
- | - | - | - |
|
9 |
Loss of all floor |
0.95 |
- | - | - | - |
|
10 |
Collapse of floor support piers |
1.00 |
- | - | - | - |
Damage repair index = cost to repair damage/ initial cost of building
This scale is particularly applicable to cyclone damage. Henderson et al. [1999] produced a more generalised version with damage in eight categories [below]
|
Category |
Description |
|
|
1 |
Negligible/Non-structural |
Includes damage to elements that are not part of the main structural framework, such as guttering, soffit lining, fascias, garage doors and the like |
|
2 |
Impact |
Where a house has obviously been impacted by flying debris, but which has not led to consequential damage. Examples would be a bent debris screen or indentations of external cladding. |
|
3 |
Roofing |
Loss of some roofing, but where battens and roof structures are left substantially intact. For HC houses roofing that had peeled back to the overbatten, but not beyond, was included in this category. This was so even if the edge batten was still attached to the roofing that had peeled back. |
|
4 |
Roof battens |
Failure caused by inadequate fixing of roof battens to rafters, so roofing and battens were blown off. The rest of the roof structure is in place. |
|
5 |
Half-roof |
A significant portion of the roof structure has been blown away. |
|
6 |
All roof |
All the roof structure would need to be replaced. |
|
7 |
Half walls |
Loss of most of the roof structure and loss of some walls. |
|
8 |
All walls |
Loss of most of the walls and roof structure. |
References
Henderson D, Reardon G and Ginger J, 1999, effects of Cyclone Vance on the strength of houses in Exmouth, W.A., in Disaster Prevention in the 21st Century, Proceedings of the Australian disaster Conference, 1-3 November 1999, Canberra, Emergency Management Australia, 47-52.
Leicester R H and Reardon G F, 1976, A statistical analysis of the structural damage by Cyclone Tracy, Annual Conference, Institution of Engineers, Australia, Townsville, 242-247.
