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The assessment of the severity of structural damage is based on several criteria such as crack width, differential settlement, and angular rotation of foundation.

The extents of damages in a building can be divided into six different categories, namely, negligible, very slight, slight, moderate, severe, and very severe. Engineers can use these categories to specify proper repair techniques if needed.

How to Assess the Severity of Damage for an Existing Structure?

1. Negligible Damage

Buildings with hairline cracks (crack-width less than 0.1mm) and differential settlement less than 3cm fall under the negligible damage category. Additionally, the angular rotation of the negligible damage category of building is less than 1/300.

2. Very Slight Damage

Buildings with isolated slight fractures and cracks on bricks visible under close visual inspection fall under the very slight damage category. The maximum width of cracks is 1mm, which can be treated during normal decoration. The differential settlement in very slightly damaged building ranges from 3 to 4cm and angular rotation is between 1/300 to 1/240.

Very Slight Damage
Fig. 1: Very Slightly Damaged Building

3. Slight Damage

Buildings with a maximum crack width of 3mm, differential settlement range of 4-5cm, and angular rotation between 1/140 to 1/175 fall under slight damage category.

External cracks need repointing and internal fractures require filing, after which redecoration should be followed. Doors and windows may be installed after this.

4. Moderate Damage  

Typical moderate damage includes cracks with 5-15mm width or several cracks with a width greater than 3mm, differential settlement of 5-8cm, and angular rotation of 1/175 to 1/120. Cracks may need to be opened up and cleaned before patching.

If it is a masonry wall, some bricks may need to be replaced, and the repointing of wall needs to be conducted properly. Windows and doors of moderately damaged buildings stick out, have fractured service pipes, and damaged weather-tightness.

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Moderate Damage Building
Fig. 2: Moderate Damage Building

 5. Severe Damage

A building is considered to be severely damaged if it suffers from large cracks with 15-25mm width. Additionally, leaning of walls, sloping of floors, and distortion of door and window frames is noticeable. The building may also have disrupted pipes and beams with low bearings.

The differential settlement is between 8-13cm and angular rotation ranges from 1/120 to 1/70. Cracks need great repair works, and part of walls, especially above windows and doors need to be replaced.

6. Very Severe Damage

Buildings falling under very severe damage category need extensive repair work that may involve partial or complete rebuilding. The differential settlement is greater than 13mm, and angular rotation surpasses 1/70; cracks exceed a width of 25mm.

The beams of very severely damaged building lose bearing, and its walls lean in a manner that requires shoring. Additionally, windows and doors are damaged with distortion. In summary, the overall stability of the building is in danger.  

Very Severe Damage Building
Fig. 3: Very Severe Damage Building

FAQs on assessment of existing building damage

What is structural damage to a building?

It is a type of damage that influences the integrity of the building.

What is negligible damage category of building?

Buildings with hairline cracks (crack width less than 0.1mm) and differential settlement less than 3cm fall under negligible damage category. Additionally, the angular rotation of the negligible damage category building is less than 1/300.

How can you tell if a crack is structural?

Structural cracks are accompanied by other indicators such as sloping floors, sticking doors and windows, and slanted doors. Continuous horizontal cracks along walls and vertical cracks that wider at bottom or top are examples of structural cracks.

What does structural failure mean?

It is the loss of load-carrying capacity of a structure or members within the structure.

Madeh Izat Hamakareem

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