Dr. Jacques gave a well-attended talk at the Fall 2018 American Concrete Institute Concrete Convention and Exposition in Las Vegas, Nevada. The topic was the effect of high strain rates on reinforced concrete bond as part of a technical session on Blast Resistance of Precast Panels. The talk was recorded and made available on YouTube by ACI’s education department.

Abstract: This presentation will highlight recent research on the effect of high strain rates on the bond strength of reinforcing steel and concrete. To evaluate dynamic bond characteristics, lap spliced reinforced concrete beams were constructed and subjected to blast loading using a shock tube. The physical and material properties of the spliced beams were selected based on a range of design parameters known to significantly influence bond strength (i.e., size of spliced reinforcement, cover depth, concrete strength, presence of transverse reinforcement). Results of the experiments demonstrated that although the underlying flexural response and nature of bond splitting failure was not affected by dynamic loads, the strength and stiffness of the splices was significantly improved. Without exception, high strain rate bond strength was always greater than corresponding low strain rate values, yielding an average dynamic increase factor (DIF) applied to bond of 1.28. A descriptive expression for the dynamic bond strength of reinforced concrete was developed to account for the observed strain rate sensitivity of splice strength based on member and material properties. Finally, the implications of this research on the design and assessment of structures subjected to blast loads will be discussed.

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