Analysis and optimization of a Safety Line under dynamic loads

In the construction and maintenance of civil and industrial buildings there is an high risk for the worker to fall from high places. The worker has to be protect with a proper fall protection device able to prevent the human damage but, at the same time, which permits all the movements of the worker. Very effective protection systems are the Safety Lines. These systems are based on the positioning of fixed cables to which the user can be connected with a moving cable. In this way the safety of the worker is assured if the cables systems are dimensioned to resist to the worker weight increased by the dynamical effect, with a proper safety coefficient. However, the cable systems have a structural behaviour with a very low damping and the oscillations of the attached mass can be very large. Clearly, these systems have to arrest the fall minimizing the pendulum effect, therefore one or more dissipative devices have to be installed. In this paper a Safety Line installed by the Italian Society “Nuovo Modulo S.p.A.” (BG) on its new buildings is investigated with the intention to show the importance of a proper design of the dissipation devices. Using a finite element program the authors investigated the dynamical behaviour of the installed safety system. The design of the mechanical properties of the dissipation devices was performed using a genetic algorithms approach.