Issue 30

A. Fernández-Canteli et al., Frattura ed Integrità Strutturale, 30 (2014) 383-393; DOI: 10.3221/IGF-ESIS.30.46 392 0 0.5 1 1.5 2 2.5 3 0 0.5 1 1.5 2 2.5 3 COD (mm) Load (kN) Experimental Numerical simulation 0 0.5 1 1.5 2 0 0.5 1 1.5 2 2.5 3 3.5 COD (mm) Load (kN) Experimental Numerical simulation a) b) Figure 14 : Direct comparison for the experimental and numerical energy curves once corrected. (a) Specimen 1; (b) Specimen 2. C ONCLUSIONS he principal conclusions derived from this work are the following: - The 2D simulation implies considering hypothetical bars in which the opening process during testing is achieved by means of prescribing a progressive horizontal displacement of the pulling bars. As a matter of fact, the calculations do not facilitate a reliable reproduction of the real pulling bars bending during testing. - As a consequence of the inadequate boundary conditions imposed, two effects not occurring during execution of the real test are introduced: a) a parallel opening of the notch lips is enforced so that the factual bending of the pulling bars during testing is not adequately modeled, and b) the transversal free movement of the specimen, necessary for maintaining the geometrical compatibility notch-bar under equilibrium conditions during testing is impeded. - Both effects implying stiffer solutions lead to an overestimation of the fracture energy in the test simulation compared to the experimental results the first effect having greater influence on the result of the fracture energy. - Accordingly, 3D calculations are unavoidable to an adequate numerical simulation of the real testing conditions is intended aiming at to facilitate a true value of the fracture energy of the concrete. - A reasonable agreement between the experimental results and the numerical simulation of the fracture curve is achieved. - A conversion between the modified compact tension test (MCT) and the standard procedures, i.e. wedge-splitting (WST) and three point (3PB) or four point bending test (4PB) can be now envisaged and justified numerically. A CKNOWLEDGEMENTS he investigation reported in this paper was supported by grants M100411204, CZ. 107/2.3.00/20.0214 and FAST- S-14-2532 and projects BIA2010-19920 of the Spanish Ministry of Science and Innovation MICINN and SV-PA- 11-012 of the Dept. of Education and Sciences of the Asturias Regional Government. R EFERENCES [1] Karihaloo, B.L., Fracture Mechanics & Structural Concrete, Longman Scientific & Technical, New York (1995). [2] Cifuentes, H., Alcalde, M., Medina, F., Comparison of the size-independent fracture energy of concrete obtained by two test methods. VIII International Conference on Fracture Mechanics of Concrete and Concrete Structures. FraMCoS-8. Toledo (2013) 1–6. [3] Cifuentes, H., Alcalde, M., Medina, F., Measuring the Size-Independent Fracture Energy of Concrete. STRAIN: An International Journal For Experimental Mechanics. 49(1) (2013) 54–59. T T