PSI - Issue 68

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Koji Uenishi et al. / Procedia Structural Integrity 68 (2025) 547–553 Uenishi et al. / Structural Integrity Procedia 00 (2025) 000–000

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Table 1. Material properties evaluated from the field experiments and employed in the numerical simulations. Property Concrete material Reinforcing steel bars Density 2,320 kg/m 3 7,800 kg/m 3 Young’s modulus 34.2 GPa 200 GPa Poisson’s ratio 0.25 0.3

sources and rebars for the RC block shown in Fig. 2. The snapshots in Fig. 3(b-d) numerically obtained after the simultaneous application of EDI to the three blast holes show that the compressive waves initially produced by the action of EDI to the blast holes are propagated, quickly reflected at the front free surface and turned into tensile waves. This is rather similar to the case of a cylindrical concrete specimen without rebars subjected to a single EDI at center (Uenishi et al. 2014) where the reflection at the outer free surface and the compression to tension transition at the free surface play an important role in dynamic fracture development. Furthermore, if reinforced, as shown in Fig. 3(d), rebars can “capture and maintain” tension along the rebars, this time along the vertical foremost rebars, and may form a vertical virtual interface. In Fig. 3(e), due to the vertical “virtual interface” effect induced by these foremost rebars, a region of relatively larger tension exists in front of the vertical virtual interface indicated by the broken lines and thus the concrete in that region can be fragmented, to result in the exposure of the vertical virtual interface or the foremost rebars as desired. 4. Conclusions We have shown the mechanical “virtual interface” effect of reinforcing steel bars (rebars) on dynamic fracture development in RC structures, which can be induced by the waves due to electric discharge impulses (EDI). Through experimental and numerical observations, we have found that specific geometrical combinations of blast holes and rebars with/without empty dummy holes can cause horizontal “slicing” along a horizontal virtual interface formed by the topmost rebars as well as vertical cutoff along a vertical virtual interface consisting of the foremost rebars in a RC structure. By the selection of the appropriate geometrical combination, only the topmost or foremost rebars can be exposed efficiently. Once exposed, the rebars can be cut without difficulty, e.g. by an electric sander, and (relatively small but possibly complex) RC structures can be disintegrated without unnecessary damage. The mechanical effects found through this series of experiments and numerical simulations for controlled dynamic disintegration are wave-induced, and therefore, the developed basic concepts can be applied also to conventional blasting using explosives. Acknowledgements The authors would like to sincerely acknowledge the technical support provided by Kanadevia Engineering Che, L., Gu, X., Li, H., 2021. Numerical Analysis and Experimental Research on Hard Rock Fragmentation by High Voltage Pulse Discharge. Minerals Engineering 168, 106942. Peng, J., Wang, X., Zhang, F., Yang, X., Gao, J., 2022. Influences of the Burden on the Fracture Behaviour of Rocks by Using Electric Explosion of Wires. Theoretical and Applied Fracture Mechanics 118, 103270. Shi, H., Hu, Y., Li, T., Tao, Z., Li, X., Wu, J., Murphy, A. B., Qiu, A., 2022. Detonation of a Nitromethane-Based Energetic Mixture Driven by Electrical Wire Explosion. Journal of Physics D: Applied Physics 55, 05LT01 (7pp). Uenishi, K., Sakaguchi, S., Shigeno, N., Yamachi, H., Nakamori, J., 2018. Controlled Fracture of Brittle Solid Materials Based on Wave Dynamics. Procedia Structural Integrity 13, 652–657. Uenishi, K., Yamachi, H., Nakamori, J., 2024. On Typical Inhomogeneities Controlling Dynamic Disintegration of Concrete Structures. Engineering Fracture Mechanics 298, Article Number 109945, 11 pages. Corporation. References