PSI - Issue 44

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Ciro Del Vecchio et al. / Procedia Structural Integrity 44 (2023) 1411–1418 Ciro Del Vecchio et al. / Structural Integrity Procedia 00 (2022) 000 – 000

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3. Experimental results The crack pattern of the wallet at the different anchors and the experimental results in terms of pull-out force vs. the total recorded displacement are depicted in Fig. 4 and Fig. 5, respectively. The results are grouped with reference to the bar diameter in Fig. 5a (  10 mm) and Fig. 5b (  14 mm). A summary of the main results in terms of peak strength, peak tangential stress (evaluated dividing the load by the embedded lateral surface of the rebar), slip at the peak strength and failure mode is reported in Table 4.

Table 4. Summary of main test results

Peak tangential stress [MPa]

Slip at peak strength [mm]

Label Peak strength [kN]

Failure mode

 10_center_0.15  10_edge_0.15

46.14 46.07

4.90 4.89

40.69

Bar rupture

5.28 Splitting after bar yielding

 14_center_0.15

48.13

3.65

0.61

Masonry cone detachment

 14_edge_0.15  14_edge_0.10  14_edge_0.20

42.17 38.20 46.15

3.20 2.90 4.90

0.68 0.48 0.78

Splitting Splitting Splitting

The two anchors realized with the  =10 mm steel bars failed due to bar rupture (i.e. achievement of the ultimate strain in the steel bar) and due to splitting of the masonry after the yielding of the bar in the test  10_center_0.15 and test  10_edge_0.15, respectively. A detachment of a small portion of tuff around the bar was observed in the  10_center_0.15 test (see Fig. 4a). The splitting failure with a vertical crack was observed during the test  10_edge_0.15 (see Fig. 4b). The same strength was recorded with a peak strength about 46.14 kN and 46.07 kN for the  10_center_0.15 and  10_edge_0.15 test, respectively. The total displacement at the peak strength in the first test was significantly larger than the second one, because in this case the splitting failure did not affect significantly the peak strength but limited the deformation development in the steel after yielding (see Fig. 5a). The experimental test  14_center_0.15 showed a failure of the masonry support with the typical masonry cone detachment (see Fig. 4c). In this case the maximum strength achieved during the test is 48.13 kN with a displacement of approximately 0.60 mm. The experimental tests on the 14 mm steel anchors located at the edge of the wall (  14_edge_0.15,  14_edge_0.10 and  14_edge_0.20) showed a brittle response with a splitting failure (see Fig. 4d,e,f). In all these tests a vertical crack typical of splitting failure separated the masonry block in two parts with spalling of the external portion. This resulted in a peak strength lower than the one recorded on the test  14_center_0.15. The increasing of the axial stress (from 0.10 MPa to 0.20 MPa) resulted in a marked increase in the peak strength and in the corresponding displacement (see Fig. 5b). In particular, the test  14_edge_0.15 showed a reduction in the peak strength of only 12% respect to the center rebar. The increase of the axial load from 0.15 MPa to 0.20 MPa gave an increase of the peak strength of 10%, while the decrease of the axial load with a stress from 0.15 MPa to 0.10MPa resulted in a decrease of the peak strength of about 10%. 5. Conclusions This paper reports and discusses the results of an experimental program consisting of pull-out tests on steel anchors injected in a tuff masonry wallet and tested under different axial load pressures. The experimental tests showed a different failure mode depending on the diameter of the steel bar and the position of the anchor (center or edge). Both the anchors realized with 10 mm bar yielded. The one realized in the center of the wall failed due to bar rupture, while the one on the edge failed in splitting after yielding. On the other side the anchors realized with 14