| Abstrakt: |
Working in trees is an inherently dangerous profession, with a higher than average fatality rate. Climbers secure themselves with a rope and harness to a tie-in point to ascend into and work in a tree, but it can be difficult—if not impossible—to assess the safety of a tie-in point from the ground. Very little experimental work has described the loads associated with ascending into and working in trees, but it is critical to understand them to assess safety. We measured loads induced by competitors in the ascent event at the International Tree Climbing Competition and analyzed their amplitude and frequency. We also measured the sway frequency of a small sample of tie-in points. Load time histories revealed repeated cycling between maximal and minimal impulse loads at a particular frequency as competitors ascended. After accounting for competitors’ weight, ascending using a single foot ascender induced greater loads than footlocking or using two foot ascenders. Footlocking induced loads at a lower frequency than using two foot ascenders. Although the loading frequency for all techniques was higher than the first natural sway frequency of tie-in points, the atypically large tie-in point used during the ascent event precludes extrapolation to tie-in points of typical size. Since there are very few data to quantify loads during an ascent, and many other relevant aspects to quantify in order to estimate the likelihood of failure of a tie-in point, the results will be useful to future studies. [ABSTRACT FROM AUTHOR] |
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