Fatigue crack growth of high-strength concrete in wedge-splitting test

Abstract

In this study, a wedge-splitting testing was carried out for the investigation of fatigue crack growth behavior of high strength concrete. Selected test variables were concrete compressive strength (28, 60, and 118 MPa) and stress ratio (6, 13%). In order to apply the target stress ratio, the maximum acid the minimum fatigue loadings were 75-85 and 5-10% of ultimate static load, respectively. Fatigue testing was preceded by crack mouth opening displacement (CMOD) compliance calibration, acid then the fatigue crack growth was computed by crack length vs. the CMOD compliance relations acquired by the CMOD compliance calibration technique. In the fatigue test, the frequency of loading cycle was 1 Hz, and the initial notch length a(0) was 30% of specimen height. To verify the applicability of the CMOD compliance calibration technique to wedge-splitting testing, the crack lengths measured by this method were compared with those predicted by linear elastic fracture mechanics (LEFM) and dye penetration testing. On the basis of the experimental results, an LEFM-based empirical model for fatigue crack growth rate (da/dn - Delta K-I relationship) that takes strength into account was suggested. The fatigue crack growth rate increased with the strength of concrete. It appeared that the da/dN - Delta K-I relationship depended on stress ratio, and the effect was evaluated by the proposed equation. In addition, the comparisons between the CMOD compliance calibration technique and the other methods supported the validity of this technique in the wedge splitting test. (C) 1999 Elsevier Science Ltd. All rights reserved.