Behavior of GFRP retrofitted reinforced concrete slabs subjected to conventional explosive blast

Majority of protective engineering in China has typically been designed to resist explosion of nuclear weapon instead of conventional explosive blast. This paper proposed a retrofitting method to improve the blast resistance of existing reinforced concrete (RC) slabs against conventional explosion using externally bonded glass fiber reinforced polymer (GFRP) strips. In order to assess the effectiveness of GFRP strips in enhancing the blast resistance of RC slabs, a series of underground blast tests for the first time were conducted. Five square RC slabs, including one companion control specimen and four GFRP retrofitted slabs, were subjected to blast loading generated from the detonation of high explosives ranging from 400 to 1400 g of trinitrotoluene (TNT). The reflected blast pressure, acceleration and central deflection of the slabs were measured and analyzed as well as the strains of steel bars, concrete and GFRP strips. The post-blast damage and failure mode of each slab were carefully investigated to determine the failure mechanism. The effects of charge burial and standoff distance on the blast pressure and structural response were analyzed in detail. The test results indicate that overall the GFRP retrofitted slabs performed much better and survived higher explosive blast than the control slab. Externally bonded GFRP strips strengthening can effectively increase the ultimate blast resistant capacity of RC slabs against conventional explosive blast.