Structural behaviour of ski safety barriers during impacts of an instrumented dummy

Aim of the work was the development of a full scale test method for performing impact tests under controlled conditions on the safety barriers usually adopted during the ski world cup events at the arrival arena. A tower pendulum was designed in order to accelerate a wooden dummy of the total mass of 70 kg up to a maximum speed of about 60 km/h. The dummy was instrumented at the centre of mass with three accelerometers in the X,Y,Z directions, connected to a IMC Cronos data acquisition system and sampled at 50 kHz each. From the measure of AccX (parallel to the suspension cable), AccY (lateral) and AccZ (parallel to the impact direction), a resultant acceleration AccR was defined for the analysis. The impacts were filmed from three different locations via commercial video cameras and subsequently analysed with Dartfish® SW to measure each impact speed. Tests were performed on the ground at a suitable location next to Cortina-Italy with soil properties similar to the snow properties: the tower can be used also in winter. Different safety barriers underwent the tests: types A (air), B and C (foam). Type B were parts of a modular system composed of foam mattresses stitched together. Tests were performed both with the barriers placed against a wooden wall fixed to the ground and with the typical poles and cables used in the snow. The peak values recorded for the decelerations were greater than 20 g with the fixed wall and around 14 g with the poles, showing in some cases a tendency of the dummy to jump over the pole barriers. The method successfully allowed to compare the absorbed kinetic energy of the foam mattresses with some air mattress as those used in competitions.