influenced by strain rates ranging from 100 to 101sec-1. In addition, it is recognized that there are some differences between the results obtained by the present measuring method using reflected tensile stress waves and by the impact splitting-tension test. 12 10 8 6 4 2 0 Stress σ [MPa] 10-6 10-5 10-4 10-3 10-2 10-1 100 101 Strain rate [sec-1] Impact tensile Impact splitting Static splitting -10 -5 0 5 10 Stress σ [MPa] 1200 1000 800 600 400 200 0 Time [µsec] -1.0 -0.5 0.0 0.5 1.0 Crack gage output [V] Crack gage Strain gage 2 Stress response at center C Figure 4: Responses of strain and crack gages. Figure 5: Strain rate effects on concrete strength. CONCLUDING REMARKS (1) In this paper the impact tensile strength and strain rate sensitivity of concrete was discussed by means of the measuring method using reflected tensile stress waves. The impact tensile experiment of concrete specimens was performed, together with the impact splitting-tension test. The experimental results were analyzed statistically by a Weibull distribution. (2) The strain rates were estimated by specifying the gage length of the tensile stress region developed until the initiation of tensile break in a specimen bar, which was measured by using crack gages. (3) The impact tensile strength of concrete used for the present study at the strain rate of 100 sec-1 was found to be approximately twice of the static tensile strength, and it was remarkably influenced by strain rates ranging from 100 to 101sec-1. REFERENCES 1. Goldsmith, W., (1960), Impact, Edward Arnold, London. 2. Johnson, W., (1972), Impact Strength of Materials, Edward Arnold, London. 3. Reinhart, H.W., (1986), In: Cement Based Composites Strain Effect on Fracture, pp.1-13. 4. Birkimer, D.L and Lindemann, R., (1971), J. American Concrete Institute, 68, pp.47-49. 5. Griner, G.R., Sierakowski, R.L. and Ross, C.A., (1975), Shock Vib. Bull., 45-4, pp.131-142. 6. Ross, C.A., Kuennen, S.T. and Tedesco, J.W., (1990), In: Micromechanics of Failure of Quasi-Brittle Materials, pp.353-363, Elsevier Applied Science. 7. Albertini, C. Cadoni, E. and Labibes, K., (1997), Journal de Physique IV, pp.C3- 915-920. 8. Brara A., Camborde F., Klepacko J.R., Mariotti C.(2001), Mechanics of Materials, 33, pp.33-45. 9. J.R. Klepaczko, A. Brara, (2001), Inter. J. Impact. Eng., 25, pp.387-409. 10. Japan Concrete Institute, Handbook of Concrete (2nd ed.), Gihoudo, 1996. 11. Daimaruya, M, Kobayashi, H. and Bustami, S., (1994), DYMAT Journal, 1-4, pp.289-305. 12. Daimaruya, M., Kobayashi, H., Bustami, S. and Chiba, M., (1996), J. Soc. Mat. Sci., Japan, 45-7, pp.823-828. 13. Daimaruya, M., Kobayashi, H. and Nonaka, T., (1997), EURODYMAT’97, J. de Physique III, pp.C3-253-257. 14. Daimaruya, M., et al., (1997), Trans. of Japan Society of Mech. Eng., 63-616, pp.2592-2597. 15. Daimaruya, M., Kobayashi, (2000), EURODYMAT 2000, J. de Physique IV, pp.Pr9-173-178.
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