PSI - Issue 62

Giulia Rossini et al. / Procedia Structural Integrity 62 (2024) 347–354 Giulia Rossini et al. / Structural Integrity Procedia 00 (2019) 000 – 000 5 In Fig. 2 – left, the same ratio , , ⁄ is presented as a function of each individual test. Tests employing the Blunt Pyramidal specimen method result in an overestimation of the actual concrete stress value by 40%. As a result, this method does not seem to be conservative. Conversely, the Saw-Cut method - Web, proposed in this study, appears to approach the predicted values more closely. Additionally, as a general observation, it tends to underestimate the actual stress value. 351

Fig. 2 (left) , , ⁄ results of blunt pyramidal specimen and saw cut – web tests. (Right) Dispersion of results obtained by the Saw Cut method-Web tests divided by geometric configurations. In summary, the Saw-Cut - Web method proved to be the most reliable test. In particular, the tests conducted in the geometric configuration GC_6_3 showed the closest approximation to the actual prestress value. The average ratio , , ⁄ for the eight tests in this configuration is 0.91, with a standard deviation of 0.19 MPa and a Coefficient of Variation (CoV) of 21% (see Table 1 and Fig. 2- left and right). Regarding the Saw-Cut method - Web, the following observations can be made: • GC_10_2 and GC_6_2: These tests were conducted at an insufficient depth, resulting in inadequate isolation of the monitored point on the surface. On the other hand, however, the depth of 2 cm is comparable to the cover, especially for older PRC elements and thus avoids cutting the longitudinal reinforcement in the web; • GC_10_3: Although this test is considered more convenient to perform than GC_6_3 due to the availability of a large space beyond the dimensions of the SG to make cuts without risking to damage them, it does not allow for complete isolation of the monitored area. As a result, the measurement is considered unreliable; • GC_6_3: This geometric configuration proves to be the most representative to obtain complete stress release. The experimental results of GC_6_3 are closer to the expected values. However, one should note that this configuration is also the riskiest to perform, as the cuts were performed very close to the measuring instrument using a 30-mm SG. These observations highlight the compromise between convenience and reliability in the choice of geometric configuration for the Saw-Cut - Web method, with GC_6_3 being identified as the most representative, but also presenting higher risks during the testing process.