Determining Friction of Safety Web Lashings For Load Securing In Round Wood Transportation

In round wood transportation the load is usually secured sideways by stanchions and gets piled up with a crowned shape with a maximum of 25% of the width to the end wall. It is additionally tied down by a safety lashing, using web lashings, but chain- or rope-lashings are also permitted. The downforce is applied onto the load through the lashing by a suitable tensioning device e.g. a ratchet. This raises the friction between vehicle and load as well as the friction between single logs and thus reduces the chance of slipping. Frictional losses occur with every deflection of the lashing on round wood and reduce the preloading force on the opposite side of the tensioning device. Currently this effect is covered by a safety coefficient, but these frictional losses may vary highly depending on characteristics of lashings and logs. To determine the frictional coefficient in static friction, we compare safety web lashings, specified by standard EN 12195-2, of different manufacturers with a lashing capacity LC of 2500 daN and a standard tension force STF of 500 N. These were tested on different wood species (Norway Spruce and European Beech), with and without bark using different wrapping angles from 0 to 100°. A test stand for frictional performance of ropes and cables was adapted to gather data on the frictional behavior of safety web lashings on round wood. This presentation deals with the influence of logs in different conditions on the frictional performance of different web lashing materials. Furthermore the conclusions and guidelines for securing loads will be discussed.