High-Strain-Rate Response of Reinforced Concrete Lap-Spliced Beams

The experimental behavior of lap-spliced reinforced concrete beams subjected to high strain rates on the order of 1.0 s−1 was studied. Eleven companion pairs of beams, each consisting of two nominally identical specimens, were designed, built, and tested under low and high strain rates. The physical and material properties of the companion pairs were selected based on a range of design parameters known to significantly influence bond strength (i.e., the size of the spliced reinforcement, cover depth, concrete strength, and 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 reinforced concrete beams was significantly improved when subjected to blast loading. Part of this increase was attributed to improvements in the load carrying capacity of the lap splices due to high strain rate effects. An average dynamic increase factor (DIF) applied to a bond of 1.28 was measured. Regardless of the strain rate, it was found that the bond strength of splices with and without transverse reinforcement increased in proportion to the ratios of the minimum cover depth and the splice length to bar diameter, respectively.