PSI - Issue 62

Annarosa Lettieri et al. / Procedia Structural Integrity 62 (2024) 789–795 Author name / Structural Integrity Procedia 00 (2019) 000 – 000 = ∑ (log 10 ∆ −log 10 ∆ ̅̅̅̅̅̅̅̅̅̅̅)(log 10 −log 10 ̅̅̅̅̅̅̅̅̅) = 1 ∑ (log 10 ∆ −log 10 ∆ ̅̅̅̅̅̅̅̅̅̅̅) 2 = 1 log 10 = log 10 ̅̅̅̅̅̅̅̅̅ + log 10 ∆ ̅̅̅̅̅̅̅̅̅̅̅

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3

(2)

(3) where log 10 Δ  i and log 10 N i are the logarithms of the stress range and number of cycles to failure for the i-th experimental collected result; log 10 Δ  and log 10 N are mean values of the experimental data; n is the number of considered data. Additionally, if the slope of the linear regression model is fixed, the procedure implementation requires the determination of only log 10 Δ  i based on Eqn. 3. Finally, the linear confidence bands of the S - N curves have been determined according to the following relationship: log 10 = (log 10 ±  )+mlog 10 ∆ (4) where  is the standard variance and  is an integer assumed equal to 2 and 3 to estimate the 95% and 99% confidence intervals, respectively. 3. Fatigue test data 3.1. Experimental investigation Aiming to investigate the fatigue behaviour of riveted connections, six different types of lap shear riveted connections have been tested within the activities envisaged by the Agreement between the High Council of Public Works (CSLLPP) and the ReLUIS Consortium implementing Ministerial Decree 578/2020 and Ministerial Decree 240/2022. The specimens were manufactured by experts working for the Italian Railway Network Agency (RFI) using old plates and rivets as part of a previous experimental campaign performed by D’Aniello et al . (2011), during which attention was mainly given to their static shear behaviour. Both plates and rivets were sandblasted to eliminate external layers damaged by corrosion. Holes in the plates were obtained by drilling, and successively, the joints were assembled with hot-driven rivets. Additional information on the manufacturing process and material employed can be found in D’Aniello et al . (2011). Fig. 1 shows the schematic representation of the investigated typology and the pictures of some tested specimens, whereas Table 1 lists all the considered specimens, indicating their main characteristics. The geometrical properties have been selected in such a way as to include typical details of existing railway bridges. All the experimental tests were performed by adopting a stress ratio R equal to 0. The stress ranges applied during the tests have been selected to investigate the high-cycle fatigue regime, that, according to the Eurocode 8 – Part 1.9, is when normal and tangential shear stresses do not exceed respectively 1.5 f y and 1.5 f y  3, where f y is the nominal yield stress of the base material. The average f y values of the specimens are 291 and 315 MPa, respectively for plate and rivets (D’Aniello et al ., 2011). The experimental results are reported in Fig. 2.

Single rivet

Double rivet

Fig. 1. The riveted details experimentally investigated.