Composite Reinforcement to Strengthen Existing Concrete Structures against Air Blast

The Wright Laboratory Air Base Survivability Section has been studying the development, application, and effects of externally applied composite reinforcing materials. The strengthened facilities would be capable of surviving an air-blast load at relatively short stand-off distances (11–15 m). An agreement was reached with the Israeli officials to conduct full-scale explosive tests in Israel using 860 kg of TNT on structures that had been reinforced externally with composite reinforcing materials. The strengthening procedure employed in this study involved two types of material: (1) an autoclave-cured, three-ply, carbon fiber-epoxy laminate; and (2) a knitted biaxial E-glass fabric. The Air Base Survivability Section applied the composite materials in Israel after the facilities had been constructed using an epoxy adhesive to bond the composite materials to the concrete substrate. This provided a simple, effective, and quick method of retrofitting an existing structure. The free-field and reflected pressures and accelerations on the walls were measured. The results of these tests were considered successful, considering the fact that the externally reinforced walls suffered high displacements, yet did not fail. The pressure and impulse data indicate that both structures would have failed catastrophically without the externally applied composite reinforcing materials.