t f
Time
t i
Road surface condiƟon
Perfect
Acceptable level for
Low speed light duty traffic
Acceptable level for
high speed heavy duty traffic
Y
X
Fig. 20.3 Incipiency interval
Metal
Metal
Weld
High stress
areas
Hairline
crack
Weld
G
r o w
t h
G
r o w
t h
Fig. 20.4 Crack propagation in a weld
568
20 Human Resources Management for Infrastructure