Performance of Concrete-Filled FRP Tubes under Field Close-in Blast Loading

Blasts, whether deliberate or accidental, are a great concern for a society's critical infrastructure as well as expeditionary military installations. Improvement to existing construction methods that enhance blast resilience can ultimately save lives and property. Concrete-filled FRP tubes (CFFTs) are known to improve a conventional reinforced concrete member's resistance to traditional loads by strengthening, protecting, and confining the reinforced concrete core. Glass fibre reinforced polymer (GFRP) tubes are readily available in a variety of sizes suitable for use as a stay-in-place structural formwork for midsized reinforced concrete members, which can simplify and expedite construction. These advantages point to CFFTs' great potential in resisting blast loads. This study aimed to quantify the advantages of encasing a reinforced concrete member with a GFRP tube subjected to close-in blast loading and to investigate the effects of the presence of the tube, the internal steel reinforcement ratio, and the blast scaled distance on CFFTs' behavior under blast loading. This was accomplished by testing four CFFT and reinforced concrete specimen pairs under blast and monotonic loading. The specimens were tested in pairs to facilitate comparisons. The CFFT specimens performed significantly better than the conventional reinforced specimens, showing greater robustness with decreased localized damage and reduced residual displacements. This indicated the need for developing analysis and design procedures for this system. Therefore, a procedure for developing Pressure-Impulse diagrams for the tested CFFT specimens was outlined and their use for the design of CFFTs under close-in blast loads was explained. A numerical procedure for developing equivalent close-in blast forcing functions was also outlined. (C) 2014 American Society of Civil Engineers.