13th International Conference on Fracture June 16–21, 2013, Beijing, China -9- Table 2. Parameters used for diagonal compression test. Ebrick 11141.67 MPa vbrick 0.25 Emortar 37000 MPa vmortar 0.14 c0 5.0 MPa φ 35° σ0 1.0 MPa hp 0.04 ζ0 1·10 -5 MPa h d 0.001 MPa The test has been run with 400 steps under displacement control. At each step the values of the total vertical load F and the displacement discontinuities h h h δ δ δ + − = + and v v v δ δ δ + − = + , in horizontal and vertical direction respectively, have been evaluated and reported in the load-displacement curves of Fig. 6. A good agreement has been obtained with experimental results. -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5 displacement [mm] 0 4000 8000 12000 16000 Load [daN] exper V1 exper V2 numeric δv ++δ v - exper H1 exper H2 numeric δh -+δ h + Figure 6. Load-displacement curves: comparison between numerical and experimental results. Fig. 7 finally shows a comparison between the collapse experimental and numerical configurations. A very good agreement can be observed, even if the numerical model is not able to simulate the fracture inside the blocks because an elastic behavior was chosen for bricks. Figure 7. Comparison between numerical and experimental collapse configurations. 5. Conclusions. The present paper deals with the mesomodelling of heterogeneous structures by means of interphase elements, that can be considered as an enhancement of the common interface elements. The possibility to distinguish internal and external contact stresses and strains permits to introduce separate failure conditions for the bulk material and for contact tractions. In particular an isotropic
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