How to Assess Extent of Damage in concrete Structures
Structural damage is the type of damage that affects the integrity of a building. It is different from structural failure which happens when a structure or its elements lose their load-bearing capacity. Damage assessment, on the other hand, is the process of investigating and evaluating the extent of damage to a structure.
Damage is often caused by environmental factors such as flooding, fire, earthquake and other natural disasters. With damage assessment, in depth inspection of the structural elements of a building is conducted from footing of roof attachment and engineering analysis to report on the building integrity.
The categorisation of structural damage depends on the level of severity. The categories are:
- Negligible damage;
- Very slight damage
- Slight damage;
- Moderate damage;
- Severe damage; and
- Very severe damage.
To assess the extent of the damage in a structure, the following criteria are often considered:
- the state of building history;
- environmental conditions;
- structural capacity;
- durability; and
- professional involvement in construction.
These criteria can be inspected by close visual inspections and simple measurements which don’t usually require special testing or long-term investigation.
Assessing Negligible Damage
This is caused by cracks with less than 0.1mm. Its differential settlement is less than 3cm while the angular rotation is less then 1/300.
Very Slight Damage
A building is said to be damaged very slightly if it has isolated fractures and cracks on bricks which are visible under close visual inspection. For this damage, the maximum width of cracks is 1mm. The differential settlement in this category ranges from 3 to 4cm while the angular rotation is between 1/300 to 1/240. This damage can be treated during normal decoration.
Slight damage is crack width of 3mm. The differential settlement is from 4-5cm while the angular rotation is between 1/140 to 1/175. This damage can be treated by repointing the cracks and filing the internal fractures. Decoration can follow afterwards.
Moderate damage includes cracks with 5-15mm width or other cracks with a width greater than 3mm. The differential settlement is from 3-8cm while the angular rotation is between 1/175 to 1/120. To treat this damage, the cracks may be opened up and cleaned.
If a building has severe damage, there are large cracks with 15-25mm width, alongside leaning of walls, sloping of floors and distortion of door and window frame on it. The building may also have disrupted pipes and beams with low bearings. The differential settlement for this damage falls between 8-13cm while the angular rotation is from 1/120 to 1/170. This damage will require more repair works on the cracks and the part of the walls.
Very Severe Damage
This is a damage with cracks of more than 25mm width. The overall stability of the building in this category is in serious danger as the beams are severely damaged while the building is losing its bearing. It requires partial or complete rebuilding. The differential settlement is more than 13mm while the angular rotation is also more than 1/170.
The categories described above are used by construction engineers to ascertain the appropriate techniques to be used for reparation. The repair method suggested for each category can be used after proper assessment is conducted.