補強量の違いが耐爆補強効果に及ぼす影響: 連続繊維補強材を用いた鉄筋コンクリート版の耐爆補強に関する実験的研究

摘要

本研究では，前報で得られた知見を発展させるため，補強層数を2,4,6層の3水準で，繊維方向を1,2(直交)方向の2水準でそれぞれ変化させた連続繊維シート補強RC版を対象に接触爆発試験(爆薬量：200g)を実施し，上記因子の違いがRC版に対する耐爆補強効果に及ぼす影響について実験的検討を行った。また，目付量の違いが連続繊維3軸メッシュ補強RC版の耐爆性能に及ぼす影響についても併せて検討した。本研究の範囲内で得られた知見を要約すると，以下のようになる。%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/m~2, 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/m~2 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.