On July 29, 2020, a hook broke out at a top rope stand on the Ammerthaler Wand in the Franconian Jura. The IG Climbing Frankenjura, Fichtelgebirge and Bavarian Forest eV is now publishing the results of an investigation.
Summary of the bolt investigation of the safety research (SiFo) of the DAV on the Ammerthaler Wand
The focus of the investigation was on hooks, which, similar to the accident hook, were set with standoff - i.e. not flush with the rock. Both intermediate and deflection hooks were tested.
All hooks that were set with protrusion that were tested achieved maximum tensile forces in the radial load tests that were above the standard requirements DIN EN 959. (radial 25 kN). It should be noted in this regard, however, that the accident hook as a common deflection point of several very popular routes was heavily used and frequented and the tested hooks were probably exposed to less load changes or loads.
After the police had informed SiFo, a metallurgical report was able to rule out a material defect as the cause of the hook breakage.
Salewa, the manufacturer of the accident hook, carried out simulation tests with hooks of the same type. A load model with values between 0,6 and 1,6 kN was selected for the continuous load tests. This corresponds to a load that occurs when abseiling. Higher levels of exposure, such as in the case of a topline falls, were not considered.
The hook protrusion was ~ 12 mm in this test, the lever arm was ~ 32 mm. The simulation tests showed that a correctly set flush with the rock is in the area of an infinite life expectancy. In contrast, a hook set with a protrusion is clearly in the range of the finite durability. A rough calculation with all the imponderables shows that a hook set with a standstill can break after approx. 3100 abseiling processes. In relation to the accident hook that was set when the wall was opened in 2002, this equates to an abseil load every other day.
In addition, three other hooks were tested; two due to questionable rock quality and one due to critical positioning. The hook, classified as incorrectly positioned, was placed horizontally at a heavily overhanging point, not perpendicular to the rock surface. These three hooks broke out due to rock failure. Pull-out values between 6 kN and 10 kN were determined, i.e. values that are far below the standard requirement of 25 kN.
In the opinion of SiFo, there is an urgent need for renovation on very popular and thus frequently climbed tours, the diversion point of which consists only of a composite hook set with a protrusion. In addition, the quality of the rock must always be taken into account when setting hooks. In addition, the correct positioning of composite hooks must be observed. These must be set perpendicular to the rock surface, even in heavily overhanging terrain.
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Actiontalk TV about the accident
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Credits: picture and text IG Climbing Frankenjura, Fichtelgebirge and Bavarian Forest eV