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Stances in mountaineering and climbing activities: an analysis and a proposal for an improved equalized anchoring

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Abstract

In climbing on a long rock or ice route, mountaineers are tied by means of a rope. The climb is subdivided into “pitches” by “stances”, i.e. places where anchoring points are available for security and for the mutual belay of the partners. In this paper, the problem of setting up a stance by connecting two or more anchor points is addressed. The methods for achieving the highest safety in this connection are discussed. In past work, this type of analysis is generally performed for cases where the free fall line is aligned to the stance midpoint; this paper shows that the best understanding of the phenomena is achieved by investigating falls with an “offset” from the stance midpoint. The two most important cases of the current best practice are compared: the mobile and the fixed connection of the anchor points. The analysis was conducted by means of experimental and analytical investigations, to a detail that was never achieved before. The assessments are based on the dynamics of the events, not on static tests as reported in the majority of the literature. The comparison of the two practices of connection is the major task of the paper. It was conducted to such a detail as to allow the readers to form their judgement on the issue. An improved stance arrangement, which increases the stance reliability of 20 % still keeping an easy arrangement, is proposed.

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Notes

  1. These four aspects are also known as the mnemonic SRENE, proposed by John Long, that stands for solid, redundant, equal tension, no extension. See also the publication http://www.rescuedynamics.ca/articles/pdfs/EarnestAnchors3.pdf.

  2. There is also the possibility of a “in series” connection (Fig. 1c): in this case only one anchor point is loaded, the other one acts as a backup (no equalization). This method is often used with solid anchor points (e.g. bolts).

  3. The “connection triangle” is the triangle formed by the branches (made by cord) connecting the anchors points and the point (vertex) where the load, due to a possible leader’s fall, is applied.

  4. The geometrical fall factor is defined as ff = H/L, where H is the free fall height and L is the rope length connecting the falling mass to a fixed point. The ff currently describes the fall severity and its maximum value is obviously 2. This classical concept is valid in principle only when the fall energy is totally absorbed by the rope. The word “geometrical” is used here because in practice the brake absorbs part of the fall energy; hence the ff simply describes the geometry of the fall.

  5. “fmf” is defined as the ratio between the downstream (Fd) and the upstream (Fu) forces straddling the friction point during the karabiner motion. The Coulomb low states that \(\frac{F_{\rm d}}{F_{\rm u}}=e^{\mu \theta}={\text{fmf}}\) where η is the friction coefficient and θ is the winding angle.

  6. The vertex trajectory would be elliptical (foci in the anchors point) if the elongation of the triangle cord were negligible (the sum of the triangle branches remains constant).

  7. The leader’s speed can be approximately calculated from the impulse law (FΔt = MΔv). Deducing the weight of the belayer (574 N) from the total load at the stance, it is possible to obtain the contribution due to the leader's fall. This can be estimated, from averaged values, as 2185 − 574 = 1611 N in the time interval 1.96–2.26 s. Considering the adopted brake “fmf” value and taking into account its definition, it is possible to calculate the force applied by the rope to the leader; it can be guessed as 1432 N. This force, reduced by the leader weight (657 N) and applied for 0.3 s, leads to a speed reduction of 3.48 m/s. This means that, at the anchor failure, the leader’s mass speed is approximately 8.6 − 3.48 = 5.12 m/s.

References

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Acknowledgments

The authors are grateful to all the members of the C.A.I. “Centro Studi Materiali e Tecniche” for their huge experimental work and to A. Manes for his suggestions in organizing the present paper. A special acknowledgement to S. Bavaresco for his continuous contribution in arranging the tests, and to the stuntmen and belayers M. Brunet, L. Calderone, A. Manes and M. Segat.

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Authors and Affiliations

  1. Club Alpino Italiano, Centro Studi Materiali e Tecniche, Via Petrella 19, 20124, Milan, Italy

    Vittorio Bedogni, Giuliano Bressan, Claudio Melchiorri & Carlo Zanantoni

  2. Alma Mater Studiorum Università di Bologna, Viale del Risorgimento 2, 40136, Bologna, Italy

    Claudio Melchiorri

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  1. Vittorio Bedogni
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  2. Giuliano Bressan
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  3. Claudio Melchiorri
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  4. Carlo Zanantoni
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Correspondence to Vittorio Bedogni.

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Bedogni, V., Bressan, G., Melchiorri, C. et al. Stances in mountaineering and climbing activities: an analysis and a proposal for an improved equalized anchoring. Sports Eng 18, 203–215 (2015). https://doi.org/10.1007/s12283-015-0177-3

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