Introduction to forensic engineering
Introduction to forensic engineering

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Introduction to forensic engineering

4.2 Circumstances of the accident

The accident occurred on a dry, summer morning, just after the home owner had erected a two-stage extension ladder, which had only been bought recently. He put it against the back wall of his house to clean the windows on the first floor of a two-storey detached house. The ladder was standing on the level concrete paving slabs of the patio adjacent to the back garden of the house.

Figure 43(a): Arrows show where the ladder tips made contact after the ladder slipped off the sill
Figure 43(b): Wall showing series of impacts made by the ladder tips after the first contact

According to the witness statement, the owner was at or near the top where he was washing the top window (Figure 43(a)). As he moved down the ladder to clean the pane below, the ladder suddenly slipped from the sill and ‘walked down’ the wall (Figure 14(b)). He fell and was seriously injured. The ladder ended up at right angles to the wall. One of the plastic tips at the top of the ladder's uprights – called stiles – had broken (Figures 44(a), (b) and (c)), but the feet were intact. There was no damage to the metal ladder or any visible defects.

It was thought the broken tip could have caused the fall, by allowing the ladder to slip down the wall. So the owner of the ladder, who was also the injured party, initiated action against the ladder manufacturer. The solicitor approached an expert for a report, following funding from the Legal Aid Board.

Figure 44(a): Broken tip still fitted to the ladder stile
Figure 44(b): Ladder tip's fracture surface
Figure 44(c): Section of the unbroken tip compared with the broken tip. Arrows show the sharp corner in the design.
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