Strengthening with FRP composite materials of structures that are subjected to dynamic loads generated by an earthquake, strong winds and/or explosions represents a recent innovative solution of the construction industry. FRP guarantee increase in strength thanks to their linear elastic up to failure ultimate strength (i.e. up to ten times the one of conventional structural steel) and energy absorption thanks to improved ultimate deformations with respect to un-reinforced masonry. There are though several drawbacks in such type of application that have induced researchers to investigate alternative and even more efficient solutions:

• FRP, as commonly used in this type of application, consist of fibers that need to be impregnated by hand in field using mostly epoxy resins (using a roll after having carefully prepared the substrate), that at the same time impregnate and bond the composite on the substrate; in such type of application generally FRP create a grid which does not cover the entire wall surface, with consequent difficulty to catch all flying debris;
• when the FRP system reaches its ultimate strength the rupture is sudden leading to a complete collapse of the member since the structure has no residual capacity.

TEC.INN. S.r.l., with over 20 years experience in the retrofitting of concrete and masonry structures using innovative materials, has investgated a new strengthening system for structures that are subjected to dynamic loads (wind, earthquake...), that couples the use of FRP with a material which is well known in the civil industry but never before used for this type of purposes: “polyurea”, a polyurethane resin with an incredible toughness and deformability.

By combining FRP and polyurea, TEC.INN. S.r.l. has patented a retrofitting system called: Elastic Systems for Dynamic Retrofitting.

The E.S.D.R.® system is a modular strengthening package, consisting of 3 layers realized with different stacking of materials, that can be tailored for any loading scenario depending on the level of mitigation that needs to be achieved for the building.