Experimental Snap Loading of Synthetic Ropes

Abstract

Large tensile forces, known as snap loads, can occur when a slack rope becomes taut. Such forces may damage the rope or masses connected to it. Experiments are described in which one end of a rope is attached to the top of a drop tower and the bottom end is attached to a weight. The weight is raised to a certain height and then released. The force at the top of the rope and the acceleration of the weight are recorded during the first snap load that occurs. Repeated drop tests are performed on each rope. The effects of the type of rope, drop height, drop weight, whether the rope has been subjected to static precycling, and the number of previous dynamic tests are examined. A mathematical model is proposed for the rope force as a function of the displacement and velocity of the weight.

An Approach for Quantifying Dynamic Properties and Simulated Deployment Loading of Fire Service Escape Rope Systems

“…Attempts have been made to improve the CI 1801 protocol with two charge-coupled device (CCD) cameras that automatically record the displacement of each marker on the rope as it is loaded. 15 These global measurements of system deformation are limited in their ability to accurately assess rope properties due to inclusion of external energy absorption mechanisms such as knot slippage and load frame compliance. Others have estimated dynamic load-displacement characteristics during a single drop experiment, either by integrating load-time data from load cell measurements 4,14 or from direct measurements of acceleration of the dynamic drop mass.…”

“…12,13 While adoption of this technique to dynamic loading is possible, the need for two high-speed cameras can be cost prohibitive. However, direct measurement of local rope deformation is challenging with ''snap loading''-a rapid loading in which a rope suddenly goes from a loose state to a tight state 15 -experiments due to the large elongation, the opportunity for out-of-plane sample motion during the drop, and slack in the rope prior to the experiment. 15 These global measurements of system deformation are limited in their ability to accurately assess rope properties due to inclusion of external energy absorption mechanisms such as knot slippage and load frame compliance.…”

“…Several models have been derived for a rope undergoing a single impact event using solutions based on (1) experimentally derived empirical relationships, 15 or energy balance approaches derived either (2) analytically 2,14 or (3) numerically, 5,6 some of which included intricate descriptions of properties and interactions between specific components of the rope. Several models have been derived for a rope undergoing a single impact event using solutions based on (1) experimentally derived empirical relationships, 15 or energy balance approaches derived either (2) analytically 2,14 or (3) numerically, 5,6 some of which included intricate descriptions of properties and interactions between specific components of the rope.…”

Three-dimensional analysis of the seismic response of guyed masts

“…Drop tests [35] and cyclic vibration tests [36] were conducted. The ropes stiffened nonlinearly as they extended, and the force was approximately proportional to the elongation raised to the power 1.3 (under conditions of no pre-tension).…”

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

“…In many applications, elastic deformation of dynamic ropes and/or secondary energy absorbers are employed to reduce the arresting load transferred to the user to reduce the risk & Gavin P. Horn ghorn@illinois.edu of injury from dynamic loading. A great deal of research has been conducted to characterize the quasistatic and dynamic strength and energy absorption characteristics of ropes used in the maritime industry [4][5][6][7][8], industrial fall protection [9,10], recreational sport climbing [11][12][13][14] and even in single polymer strands [15,16]. Secondary components (that remove energy from the system through controlled failure, friction, or deformation as they are loaded) have been shown to reduce the impact load on the individual to a safer range [17][18][19][20].…”