PSI - Issue 35

Kai Friebertshauser et al. / Procedia Structural Integrity 35 (2022) 159–167 K. Friebertsha¨user and M. Werner and K. Weinberg / Structural Integrity Procedia 00 (2021) 000–000

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Fig. 3. Test setup of the concrete cylinders with (i) horizontal, (ii) inclined, and (iii) curved pad configurations; the expected crack paths are indicated by yellow dots

Fig. 4. Upper and lower part of cracked specimen obtained from di ff erent pad configurations: (i) horizontal, (ii) inclined, and (iii) curved; see Fig. 3

Fig. 5. Upper fragment of cracked specimen from Fig. 3 (iii) with D cyl = 250 mm and approximating function (16) with parameters a = 0 . 21 and b = 13 . 5

pad configuration, especially at the top surface where they follow a straight line. In the curved configuration (iii), the cracks and the resulting fragments have a certain curvature. To confirm the latter, we repeated the curved pad configuration (iii) with a larger vessel of diameter D cyl = 250 mm. The aim was to reduce boundary e ff ects; the inserted pads are the same as before. A typical resulting fragment of these experiments is shown in Fig. 5. From the specimens’ side view, the cracked surface can well be approximated by a (mirrored) bell curve. Such bell-curved shape clearly deviates from the conical structure which one would expect from static calculations related to punching shear, see Zilch and Zehetmaier (2010). We approximate the crack shape by f ( r ) = a · D cyl · exp   − b r 2 D cyl 2   (16)

where r is the radius, see Fig. 5, and the parameters are a = 0 . 21 and b = 13 . 5. All dimensions are given in mm.