Many structures are assembled by welding smaller components: a steel frame by
joining smaller bars of different shapes, a pipe by folding a metal sheet over and
welding along the joint. After manufacture, some minor cracks may have remained
in the welds, and either escaped detection or were not considered serious enough to
Fig. 20.2 Incipient Failure. (a) How road surfaces get damaged. (b) Tyres ‘drop’ into defect and
climb. (c) The ‘drop’ energy damages the road further
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567
joining smaller bars of different shapes, a pipe by folding a metal sheet over and
welding along the joint. After manufacture, some minor cracks may have remained
in the welds, and either escaped detection or were not considered serious enough to
Fig. 20.2 Incipient Failure. (a) How road surfaces get damaged. (b) Tyres ‘drop’ into defect and
climb. (c) The ‘drop’ energy damages the road further
20.1 Infrastructure and Its Design Requirements
567