Comprehensive concrete fracture tests: Size effects of Types 1 & 2, crack length effect and postpeak

The comprehensive fracture tests of notched and unnotched beams presented in the preceding paper are evaluated to clarify the size effects and fracture energy dissipation. The test results for beams with notches of various lengths agree closely with Bažant's Type 2 size effect law and yield the value of the initial fracture energy Gf. Since nearly complete post-peak softening load-displacement curves have been obtained, the total energy dissipation by fracture can be accurately evaluated and used to determine the RILEM total fracture energy GF. For the present concrete, GF/Gf ≈ 2. The transition between the Type 1 and 2 size effects are determined and is found to be very different from that assumed in Hu and Duan's boundary effect model. Determination of a universal size effect law fitting the beam strengths for all the sizes and all notch depths is relegated to a subsequent paper.