BLAST TESTING OF PRESTRESSED CONCRETE UNDER IMPULSIVE LOADING
|Publication Date:||30 June 2017|
Considering the properties of prestressing steel and the level of compression in concrete, prestressed concrete members should respond with lower deflections under blast loading than similarly-sized, conventionally reinforced members. However, the available acceptance criteria for prestressed concrete in typical structures, provided in CSA standard S850-12, "Design and Assessment of Buildings Subjected to Blast Loads," ASCE standard 59-11, "Blast Protection of Buildings," and the Precast/Prestressed Concrete Institute ("PCI") Blast-Resistant Design Manual, First Edition are significantly more stringent than for conventionally reinforced concrete. The technical basis for the difference is unclear.
Therefore, given the number of existing prestressed concrete containment structures and new builds of similar construction anticipated in Canada, the U.S.A., and worldwide, there is a need to define design provisions for prestressed concrete elements with all specificities of nuclear structures (e.g., reinforcement ratio and detailing, prestressing level) which could potentially use more relaxed acceptance criteria than for typical structures, if warranted. This information would be beneficial for vendors, designers, regulators, and standards development organizations worldwide. This research project proposal originated from a joint task group of three different standards committees: Joint ACI-ASME Committee on Concrete Components for Nuclear Service (BPVC Section III Division 2/ACI 359), ACI 349 (Concrete Nuclear Structures), and ACI 370 (Blast and Impact Load Effects).
Toward that objective, sponsors from industry, regulatory agencies, and standards developing organizations, which have a direct interest in nuclear structures, provided the sponsorship funds for this research project to test prestressed concrete slabs under blast loading. This research project was managed by ASME ST-LLC.
ASME ST-LLC tasked SSE to perform a series of blast tests on simply supported, two‐way prestressed concrete slabs to achieve a range of responses based on the research proposal from the ASME Special Working Group of Modernization reporting to the Joint ACI-ASME Committee on Concrete Components for Nuclear Service (BPV III).
The eight slab specimens were 10-5/8 inches (270 millimeters (mm)) × 16 feet (ft) (4880 mm) × 16 feet (4880 mm) in dimensions. Two layers of conventional flexural reinforcement and local shear reinforcement around lifting points were included in each slab. Prestressing in the concrete was introduced using posttensioned (PT) tendons. The parameters that varied were the pressure loading, conventional reinforcement ratio, and level of prestressing.
This publication provides the background for the open-air blast testing of the precast, prestressed slabs, and summarizes results for a total of nine blast tests performed on the eight slabs. An overview of the testing facility is provided in Section 2. A description of the test specimen and supporting steel frame construction is provided in Section 3. The open-air testing procedure, including instrumentation, explosive material and quantities used, and documentation recorded, and relevant prestressed concrete slab response limits are discussed in Section 4. Results are presented in Section 5. Some conclusions are noted in Section 6. Slab specimen calculations and drawings, relevant certifications, and pre-test and post-test documentation information are provided as appendices