Geoscience Reference
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significantly below these values shown. These cracks may be aesthetic and can
affect the market value of the property although the function of the building may
not be compromised.
23.7 Limiting angular distortion
•
The angular distortion is the ratio of the differential settlement to the length.
Table 23.7
Limiting angular distortion (Wahls, 1981).
Category of potential damage
δ
/
L
Machinery sensitive to movement
1/750
Danger to frames with diagonals
1/600
Safe limit for no cracking of buildings
1/500
First cracking of panel walls
1/300
Difficulties with overhead cranes
Tilting of high rigid building becomes visible
1/250
Considerable cracking of panel and brick walls
1/150
Danger of structural damage to general buildings
Safe limit for flexible brick walls L/H
4
>
23.8 Relationship of damage to angular distortion
and horizontal strain
•
The damage is usually a combination of different strains.
•
10
−
3
) and angular distor-
The relationship between horizontal strains,
h
(
×
ε
10
−
3
) is shown in Boscardin and Cording (1989) for different types of
construction and severity.
tion (
×
Table 23.8
Distortion factors (after Boscardin and Cording 1989).
Distortion factor
Type of construction
Upper limit of
Angular distortion (
10
−
3
)
Horizontal strains,
h
(
10
−
3
)
×
ε
×
Negligible
All
1.6
0
<
Slight
<
3.2
0
Moderate to severe
6.6
0
<
Severe to very severe
6.6
0
≥
Negligible
All
0
0.7
<
Slight
0
1.5
<
Moderate to severe
0
<
3.0
Severe to very severe
0
3.0
≥
Moderate to severe
Deep mines
0
3
2
2.7
Moderate to severe
Shallow mines
2
2.7
and tunnels,
4.5
1.5
Braced cuts
Moderate to severe
Building settlement
6.1
0.4
6.6
0.0
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