補強量の違いが耐爆補強効果に及ぼす影響

Abstract

When designing blast-resistant reinforced concrete (RC) structures, it is important to reduce spall damage due to reflected tensile stress waves. In this study, to devise a blast-resistant strengthening method for existing RC slabs, contact detonation tests using 200 g of explosive charges were conducted on RC slabs with rear surfaces strengthened with continuous fiber sheets/meshes. High-strength carbon fiber (HSCF) and high-modulus carbon fiber (HMCF) sheets were employed to strengthen 75-mm-thick RC slabs, and the number of layers used for strengthening them was varied between 2, 4, and 6 layers. Two types of carbon fiber reinforced plastic (CFRP) meshes, in which the weight per unit area of carbon fibers was varied between 215 and 430 g/m2, were also used to strengthen 100-mm-thick RC slabs. The results showed that the spall failure of the 75-mm-thick RC slabs could be prevented by bonding more than four HSCF sheets onto the rear side of the slab; however, the HMCF sheets had no effect on the blast resistance of the slabs because of fiber rupture. Further, the spall failure of the 100-mm-thick RC slabs could be prevented by bonding the CFRP meshes with fibers 430 g/m2 in volume. On the basis of the test results, the criteria for fiber rupture in CF sheets due to detonation loading was discussed in terms of the fracture energy of the sheets and the modified-scaled concrete thickness of the slab. Furthermore, high-speed photography was employed to investigate the spall failure process of each strengthened slab.