Determination of the redistribution shock load in climbing double rope systems

Dynamic ropes for climbing and mountaineering are considered to be safe. However, there are still accidents happening with breaking ropes, usually under the influence of sharp edges and with lethal consequences [Schubert P. Sicherheit und Risiko in Fels und Eis. Munchen: Verlag Rother; 1994]. It is obvious that a higher safety against rope failure can be achieved by using two redundant ropes, which are handled simultaneously. The falls with failure of both ropes have been investigated by Schubert[1]. However, up to date it is not clear, how much the safety against total failure (failing from a height) is really increased when using so called "double rope systems" in climbing. The case in which in a fall one of the ropes fails and the second rope holds the climber, has not been investigated. The most relevant factor for answering the problem of the survival probability of the double rope system is the determination of the acting forces before, during and after the failure of one of the two ropes and the ability of the remaining rope to absorb further dynamic loading. It has been found by Feyrer [Feyrer K. Sicherheitszuwachs dutch zwei parallele Seile. Fordern und Heben 1989:39(10):820-6] that in case of failure of one of the ropes the remaining rope has to absorb significantly more than twice the load. This process can be described as "dynamic redistribution shock loading" of the remaining rope. This article presents a scientific approach to dynamically loaded double rope systems and the dynamic redistribution shock load that occurs, should one of the two ropes fail. The analytic findings are complemented by a sample calculation and experimental results. The experimental results were attained by performing multiple drop testing series. Advice is given in order to attain optimum safety when handling double rope systems in climbing. (C) 2008 Elsevier Ltd. All rights reserved.