The impulsive loads are rare events that may occur in the lifetime of the structures and products, such as impacts and blasts, which induce different high strain-rates in the materials (collision of vehicles or vessels with bridge piers or superstructures, explosions near or inside structures, impact of projectiles, blast caused by near or far explosions, etc.). During such loading, high strain-rates are imposed on the structures. The range of strain rates caused by such accidents, may be very large: 3 or 4 order of magnitude. As results, it is necessary that the rate effects in the materials on structural responses must be taken into account in order to predict the actual structural response.

The behaviour of the materials differs a lot when is loaded dynamically instead of statically. In fact, for example in the case of concrete, under low strain rate loading the fracture process starts from existing micro-cracks and macro-cracks and has the time to choose and develop along the path of least energy requirements (i.e., around aggregate particles and through the weakest zones of the matrix). Due to low overall stress level and relaxation of material, the extension of micro-cracks in other areas of higher strength is rather limited. Under impact loading conditions much energy is introduced into the structure in a short time, and cracks as concentration points are forced to develop also along a shorter path of higher resistance - through stronger matrix zones and some aggregate particles. The very rapidly increasing overall tensile stress causes extensive micro-cracking in other areas, since relaxation cannot occur in the extremely short time of fracture.

In the design process, the material characteristics and the consequent structural behaviour should be known in a large range of strain rates, in particular the assessment tools used (computer code for example) should be validated for the same strain rate range.

The seminar presents the advances in the field of dynamic material testing methodologies in particular for what concerns the brittle materials.

Ezio Cadoni is professor at the University of Applied Sciences and Arts of Southern Switzerland, where he founded the DynaMat Interdipartimental laboratory. His research is focused on dynamic behaviour of materials, structural mechanics and experimental mechanics. He is author of more than hundred papers in reviewed International journals and conferences. Presently he is the President of the European association for the promotion of research into the dynamic behaviour of materials and its applications - DYMAT.