Assessment of the resistance to shock of building structures and of collective protective equipment using 50 kg spheroid-conical bags. Dynamic behaviour and absorption of shock-producing bodies

The shock resistance tests conducted on light-cover elements employed bags filled with sand or glass beads. The safety coefficients of these elements determined from these tests depend on the dynamic behaviour of the bag and on the energy absorbed by the latter during the shock. The authors carried out shock tests on a spring-mounted plate with two 50 kg spheroid-conical bags, one filled with glass beads, the other with sand.
The former was dropped from a height of between 0.05 m and 1 m and the latter from 0.05 m and 2 m. The relationships between the force of the shock acting on the springs of the test rig and the height of fall were recorded for each bag and for different levels of resistance to elastic deformations of the test rig. The tests demonstrated that the bags behave almost like masses that do not deform throughout the entire shock period, when the resistance to elastic deformations of the springs of the test rig is less than or equal to 98.5 kN/m, and during the load phase when the resistance is greater than or equal to 247 kn./m. During the load phase, as an initial approximation, the bags behave like an assembly of two masses coupled by a resistance to elastic deformations. In addition, it has been demonstrated that the energy absorbed during the shock, EA, varies in function of the maximum shock force RM in accordance with a law taking the form EA = EO (RM / RO) n , where EO = 1J and RO and n are constants with a value of 1.1 kN and 2 for the bag filled with glass beads and 1.25 kN and 1.85 for the sand-filled bag.