A “Toolbox” for Forensic Engineers

Establishing the Load Transfer Path 65
Figure 3.3 Position of the steps when the leg was bent, after they had become
unstable.
of their anatomy struck the projecting foot of the left stile as the right stile
lay nearly flat on the ground. The full weight of their falling body was applied
to the foot of the left stile, producing exactly the form of damage shown in
Figure 3.1.
Sometimes the falling body may land on the back frame and bend the
leg in a similar manner and the back cross brace may be buckled. In one
particular accident where the user’s body landed directly above the cross
brace the back leg was pushed down over the brace and penetrated the user’s
buttock, causing severe injury. He was a large man weighing some 130 kg
(280 lb), and stated he had stood tiptoe on the very top of a set of steps to
remove a suitcase from his attic and, as he pulled it out, the steps “suddenly
collapsed.”
Such damage as described following an accident is invariably the result
of some kind of instability while the person injured was climbing or working
from the steps near the top. Sometimes the instability is caused by overreaching,
possibly to lift something heavy off a shelf, and other times by the steps
not being opened fully and locked in position to prevent them folding forward,
or if the feet were not set on a firm, level surface. With tall ladders it
is essential to have a second person standing on the bottom rung (“footing”
the ladder) so that no rocking movement is possible while the user is working
near the top. In fact, the stiles of ladders are usually so strong that the
maximum recommended static weight of a user acting at any angle will not
bend a stile. Dynamic forces are necessary that are generated only when the