STATISTICAL ANALYSIS OF FRAGMENT SIZE DISTRIBUTION FROM SPALLATION OF RC SLABS UNDER AIRBLAST LOADS

摘要

RC slabs can be used as barricades against terrorist bombing attacks. When an explosion occurs close to an RC slab, even though the slab itself may not suffer general failure, it generates concrete fragments due to concrete spallation on the opposite side of the slab. These could become projectile threats to life safety and equipment,depending on the size of the fragments. Therefore, it is important to analyze the size distributions of the concrete fragments from spallation. In this paper, blast testing was conducted for investigation of fragment size distributions of a plain RC slab and another RC slab retrofitted with near surface mounted (NSM) carbon fibre reinforced polymer(CFRP) plates from spallation. Both slabs were subjected to the equivalent 2.1kg of TNT at a standoff distance of 0.6m, resulting in significant scabbing of the concrete. All fragments resulted from the blast tests were collected. A sieve analysis was conducted to derive the size distributions of the fragments for the slabs. The fragment shape factor distributions were also studied. It was found that the fragment size distributions follow the Weibull-distributions and that the fragment shape factors are distributed according to the Log-normal distributions.