Feasibility of Knots to Reduce the Maximum Dynamic Arresting Load in Rope Systems

Abstract

Impact loads to the human body due to falls from height can be mitigated by well-designed and characterized fall protection systems. While energy absorption methods using rope deformation and/or accessory components have previously been evaluated, the ability for simple knots tied in the system to alter impact loads has not been studied in detail. We quantify the effectiveness of various common knots to reduce dynamic loads in typical fall scenarios for which the systems are designed, and interpret this change in the context of rope strength reduction due to the knot. Knots are shown to significantly (45-60 %) reduce the quasistatic strength of rope when compared to a manufactured sewn-eye (40 %). A single exception to this outcome is with the quadruple overhand on a bite (30-35 %). Knots significantly reduce the maximum arresting load due to a dynamic impact event when compared to ropes without knots, providing significantly more energy absorption than the sewn-eye alone. In nearly all rope/knot combinations, the ratio of maximum arrest load (MAL) to breaking strength was lower with the knotted ropes when compared to the sewn-eye terminations. In particular, the quadruple overhand on a bite tied in the Technora-Technora rope resulted in MALs that were only 33 % of the minimum breaking strength (MBS). Ropes with sewn-eye terminations resulted in MALs that were 80 % of the MBS. From the scenarios investigated, the quadruple overhand on a bite provides a favorable reduction in arrest loads with the smallest associated loss of strength.

An Analytical Review of Figure Eight Loops and Bowlines as Harness Tie-in and Anchoring Knots

“…Based on these structural algorithms, the Figure Eight is more secure and stable than the Bowline, as Table 2 indicates. Further, each knots' ability to absorb energy and reduce impact forces is linked to its sinuosity, concatenation and crossing number (Martin et al, 2015;Sry et al, 2018). Energy absorption, of course, is related to the linear modulus of elasticity for ropes, so "elastic" knots are more important in rescue and rope-access contexts where low stretch or static lines are employed (Sry et al, 2018).…”

Yan Bends Kisa Bir Inceleme: Uygulama, Mantigi, Kazalar ve Test

“…Strength has been the default test parameter. It may be more appropriate to explore structural security by also performing harmonic and nonharmonic excitation tests, dynamic arrest tests, and inertial loading to evaluate knots tied in materials exhibiting poor friction and knottability characteristics (Chisnall, 1995a(Chisnall, , 1995b(Chisnall, , 1995c(Chisnall, , 2020DailyDiamond, 2017;Evans, 2016;Martin et al, 2015;Moyer, 1999a;Weller et al, 2015). Clearly more research of a standardized nature is required.…”

Ultra-High-Molecular-Weight Polyethylene Rods as an Effective Design Solution for the Suspensions of a Cruiser-Class Solar Vehicle

“…Following these considerations, the possibility of using a commercial polymeric element was investigated. Kevlar ropes with a 12 mm diameter and nominal resistance of 20 kN were tested, but crimping had the same problems found in the case of metal wires and making knots lead to a sharp (and difficult to foresee) reduction of the nominal resistance [27], eliminating in this way the advantage of the commercial component. In Figure 6, the effect of different types of knots on the quasistatic behavior of the rope is shown.…”