A simplified method for determining the double-K fracture parameters Kini Ic and Kun Ic for three-point bending tests is proposed. Two empirical formulae are used to describe the crack mouth opening displacement CMOD and the stress intensity factor Kc I caused by the cohesive force σ(x) on the fictitious crack zone for threepoint bending beams. It has been found that the two empirical formulae are accurate for a large practical region of a/D. Experiments carried out by many researchers showed that the new formula of CMOD for three-point bending beams can be directly used to predict the initial crack length for precracked beams, the notch depth and the critical effective crack length, as well as the crack length in the post-critical situation with a satisfactory accuracy. Further verification is demonstrated to determine the double-K parameters Kini Ic and Kun Ic. They are very close to those determined by the method proposed in our previous work. Using the simplified procedure, the experiments can be performed even without a closed-loop testing facility and the calculation can be carried out on a pocket calculator.

This paper shows how the double-K fracture parameters Kini Ic and Kun Ic can be determined for concrete using CT-specimens and wedge splitting specimens. The experimental results collected from the fracture tests on the very large size CT-specimens and small size wedge splitting specimens carried out by many researchers are utilized to investigate the characters of the obtained double-K fracture parameters Kini Ic and Kun Ic. It was found that the double-K fracture parameters Kini Ic and Kun Ic determined from fracture tests on the large size CT-specimens are size-independent. And the values of Kini Ic and Kun Ic determined from small size wedge splitting specimens with same dimensions are independent of the relative preformed notch length a0=D. However, when the dimensions of small size wedge splitting specimens change from 150

Based on the complete fracture process in concrete, the crack extension resistance associated with the cohesive force on the fictitious crack is investigated in detail for standard three-point bending notched beams. Five concrete materials are speci

The edoubIe-e notched no: ched specimen made of normal s: rengrh tin, crete has been stlbsected to compressive loads, kis shown that a shear crack develops at the notch tip. Visual observation and evaluation of displacement measurements have proven that this specimen allows pure mode I testing, It was possible to determine fracture toughness KIIc, Recommendations for the testing are made.

Many attempts have been focused on the textile reinforced mortar structures. The advantages of textiles are mainly a very good load bearing capacity, excellent ductility, thin size and light weight of components, resistance to corrosion, and no magnetic disturbances. Such structures are expected to have wide application foregrounds. The transfer of forces from reinforcement to mortar is accomplished through a bond. Therefore, understanding and further improving bond properties of textiles in mortar are important. In the paper, bond characteristics of various textiles in mortar obtained from pull-out tests and numerical simulations are shown and compared. The textiles used include carbon, alkali resistant glass and aramid. They were plain and impregnated with epoxy resin. Prestressed and nonprestressed specimens were tested. The experimental results show that epoxy resin impregnating and prestressing can strongly enhance the bond strength. Numerical simulations show good agreement with the experimental results and significantly contribute to a better understanding of the bond characteristics of textiles in mortar.