Blast Tests on Pre-Stressed Concrete Slabs

Abstract

The behaviour of reinforced concrete under blast loading is well understood. However, the behaviour of pre-stressed concrete under higher levels of pre-stressing, subjected to blast loading, has not been studied extensively. A blast testing program on pre-stressed, concrete slabs was established to define design acceptance criteria for pre-stressed concrete elements for nuclear structures. The American Society of Mechanical Engineers (ASME) testing program is a part of a code provision update put in place under the Joint Task Group ASME BPVC Section III Division 2 (Nuclear Concrete Containment) and ACI 349 (Nuclear Safety Related Structures). The paper presents six tests on pre-stressed concrete slabs with the same geometry (4.88m x 4.88m x 0.27 m) but with three different designs of the reinforcement and pre- stressing. The reinforcement ratio as well as the pre-stressing levels was chosen to reflect the design of existing nuclear containment buildings as well as the design of new builds currently under construction, or to be constructed in the near future. The pre-stressing for all slabs was introduced using post tensioning with grouted tendons. Two different levels of pre-stressing were introduced in the slabs: 5 MPa and 10 MPa, typical for nuclear containments. The slabs were reinforced with two different amounts of reinforcement: 95 kg/m3 and 220 kg/m3. The amount of distant ANFO explosive charge was defined to obtain different target levels of support rotations for each slab design. The main response mode observed in the tests was a flexural mode with brittle failure of the concrete under compression.