PSI - Issue 42

Monika Středulová et al. / Procedia Structural Integrity 42 (2022) 1537– 1544 M. Strˇedulova´ et al. / Structural Integrity Procedia 00 (2019) 000–000

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fixed simulations free simulations experiments

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Fig. 2. Load–displacement curves of the experiments and the models using friction free and full friction boundary conditions.

Fig. 3. Experimental setup.

3. Concrete compressive test simulations

The aim of the analysis was to evaluate the friction coe ffi cient based on the comparison of experimental results with results of computational simulations. The experimental campaign was performed at the Institute of Building Testing of Faculty of the Civil Engineering at Brno University of Technology. The results of the experiments with emphasis on mechanical fracture parameters supported by a slenderness ratio study were published by Lisztwan et al. (2021). Set up of the experiment is shown in Fig. 3. In a series of experiments, three samples were tested for each slen derness ratio. The cylinder diameter was d = 50 mm, depth was di ff ering so that following slenderness ratios were tested: 1.0, 1.5, 2.0 and 2.5. The samples were loaded by a constant displacement rate of the upper platen of the testing machine, where also the applied force was measured. Displacement was obtained by two LVDT transducers placed on opposite sides, between the loading platens (also visible in Fig. 3). Series of simulations have been calculated by the mesoscale discrete model. To obtain results independent of the ag gregate placement (geometry generation), five di ff erent virtual samples with random placement of spherical aggregates were generated per each case. Calculations were done for the same slenderness ratios as the experiments were (1.0, 1.5, 2.0 and 2.5.), with additional ratios of 1.1, 1.2, 1.3 and 1.4 in the range where friction e ff ect is expected to be the most pronounced. The geometry of the model and used boundary conditions reflect the experimental settings in Fig. 3. On the level of individual particles, the bottom base of the cylinder is fixed in the vertical direction, while lateral movement is either free, partially restricted by the application of a frictional force or fixed depending on the tested scenario, respectively. The prescribed vertical displacement is applied at the top platen, where lateral movement is treated in the same way as at the bottom. No rotations are allowed to the rigid bodies adjacent to the top or bottom loading platens in all of the considered scenarios. In the first phase of the simulations, both friction free and full friction scenarios were run for each slenderness ratio. As in the experimental setting, a constant displacement rate was applied. The results have shown the same tendencies 3.1. Indirect determination of the friction coe ffi cient via simulations