SLJ: ANCHORAGE OF THE LINE-LIFE SYSTEM
Description of the SLJ node
The SLJ node - Safety Line Joint - performs the anchoring function of the security system called "linea-vita" to the roof structure. The knot consists of three elements bolted together. The element A consists of a support plate and a bolt that connects the node with the elements B and C. The SLJ node prevents the rotation of the anchor in all directions and acts as a lock-in constraint.
The SLJ node is made in the workshop according to the UNI standards for the chemical composition of steels and welding processes (UNI EN ISO 4016: 2002, UNI 5592: 1968, UNI EN ISO 898-1: 2001, UNI EN 20898-2: 1994). The screws and bolts are made of high-strength steel class 8.8 and the rest of the elements are made of S355 steel. To guarantee greater durability, all the elements are subjected to a hot-dip galvanizing process.
Flexed bending joint: the bending moment is produced by a force F applied at a distance of 350 mm from the anchorage of the vertical upright from the plate, the cutting force is equal to T = F. The SLJ node is constrained in correspondence of the holes of the element C which connect the node to the underlying covering structure.
The results were obtained with a non-linear analysis of the stress / strain state and of the displacement / deformation behavior, performed with a finite element calculation program for incremental load values. The characteristics of the materials are as follows: S355 steel plates; high strength screws and bolts 8.8. The results of the tests carried out refer to the action of force F1 and F2 at a distance of the node equal to 350 mm. The forces F1 and F2 reach the following stress values:
Where: Se = Max stress at the elastic limit.
Ss = Max stress at the complete plasticization of the resistant section.
Results of the force F expressed in Newton (N) equal to 10 N = 1 Kg.