Assessment of the ultimate actual strength of rock-climbing protection devices: Extraction tests in the field and the human capability to predict the ultimate strength

Abstract

Background. Rock climbing protection devices are crucial for climbing practice safety and for mountaineering in general. The use of these devices, together with appropriate tech-niques, reduces injuries in the critical event of a climber’s fall. Although European stan-dards and rules support the manufacturer in the design, production and laboratory test-ing, a thorough investigation of their behaviour in a real environment and during an actual placement has not yet been performed. Methods. The aim of this work is to present an insight into the strength of such devices through the application of a monitored, quasi-static, increasing force in a field environ-ment. Results from several types of devices (pitons, nuts and cams) are presented and crit-ically evaluated with respect to the values of the loads acting on the anchors due to the fall of the climber. Results. As far as the piton actual strength is concerned, the present activities show that the characteristics requested by EN specifications and rules are functional for product qualification purposes, but of very little use when defining the load holding capabilities once the devices are in place. However, even if the actual strength does not match the requirement of the standard, the comparison with the actual load applied is fairly encour-aging. With regards to nuts and cams, it is worth underlining the importance of a correct placement: when placed correctly, the actual strength achieved by the device in the field complies and is higher than the classification of the EN standard. Moreover, an investigation of human capability to predict the ultimate strength of rock-climbing protection devices placed in the field has been carried out, with the aim of verifying the reliability of the climber’s judgement, and, possibly, improve the safety of the in-field decision-making process. Conclusions. The lesson learned from the experiments is that modern equipment shows one step better behaviour and, similarly to pitons, the device-rock coupling dictates the pairs actual strength, assuming of course a sound placement. To the author’s best knowl-edge, the present work represents the first attempt to investigate the human capabilities to assess the reliability of a protection placement in-field.