PSI - Issue 62

Rossella Venezia et al. / Procedia Structural Integrity 62 (2024) 796–808 Rossella Venezia and Alessio Lupoi / Structural Integrity Procedia 00 (2019) 000 – 000

804

9

lead to the full loss of support from the pier head. Flexural capacity threshold for RC piers, given by Eq. (5), is obtained from a model specified for assessment in the Italian design code (Circular NTCs 2018, 2019). = 3 +[ − ] (1− 0.5 ) (5) The shear span L V is taken equal to L in the longitudinal direction of multiple stem piers and L/2 in the transverse direction of multiple stem piers. The plastic hinge length L P , calculated as 0.1 L V , is taken equal to the medium value between the longitudinal and the transverse directions lengths, i.e. 0.075 L . As described before, yield and ultimate curvatures are determined automatically. While shear capacity threshold for RC piers, given by Eq. (6), is obtained from a model specified for assessment in the Italian design code (Circular NTCs 2018, 2019), which considers contributions to shear strength from concrete, axial force, and transverse steel. = + + (6) =0.8 √ (7) = ℎ2− (8) = (9) The results of pushover analyses are illustrated in next paragraphs. They are compared with those obained by the inelastic time-history analysis (ITHA), in which three artificially generated accelerograms have been used. They are generated based on the elastic spectrum for soil type B. The same spectrum has been used as the basis for all the pushover analyses. 4.1. Load distributions The analysis has been performed in both longitudinal and transverse directions subjecting the structure to two different load distributions. First load distribution is constant along the deck. Second load distribution is one that considers the contribution of the modes according to the response spectrum analysis. In both longitudinal and transverse directions, due to bridge asymmetry, other two load distributions, that are specular to the previous one, has been considered. In this study analysis and results are presented only for the longitudinal direction. To sum up, the analysis has been performed subjecting the structure to the following load distributions: uniform shape in x direction “+” ( concordant to x axis orientation) (see Fig. 9) , uniform shape in direction “ - ” ( discordant to x axis orientation) (see Fig. 10), modal shape in x direction “+” (concordant to a is orientation) (see Fig. 11), modal shape in x direction “ - ” (discordant to a is orientation) (see Fig. 12).

Fig. 9. Assumed uniform shape in x direction “+” .

Fig. 10. Assumed uniform shape in x direction “ - ” .