PSI - Issue 84

Fabio Mazza et al. / Procedia Structural Integrity 84 (2026) 944–951

946

The geometry of the pre-tensioned beam supporting the RC slab of 30 cm thickness is reported in Fig. 2, assuming 38 pretensioned strands with 6 mm diameter located in the bottom flange, at the mid span cross-section (Figs. 2a,c), with 6 strands draped towards the top flange, near the end cross-sections (Figs. 2b,c). A cylindrical compressive strength of 40 N/mm 2 and 25 N/mm 2 are assumed for PC beams and RC slab, respectively, while a strength at 1% elongationof 1670 N/mm 2 is considered for prestressing steel.Results of the normal stress verification at the tensioning and serviceability stages of the PC beam are also reported, in terms of Guyon’s zone and elastic core, with reference to the resultant tendon (Fig. 2d).

(a) End cross-section.

(b) Mid-span cross-section.

(c) Longitudinal section.

(d) Guyon’s zone and elastic core. Fig. 2. PC beam of the composite deck (unit in m).

The HDRBs are designed at the collapse prevention (CP) ultimate limit state considering horizontal (i.e. PGA H =0.351g) seismic loads, corresponding to a high-risk seismic zone and very dense subsoil (i.e. class B, site amplification factor S H =1.053) of the site, assuming for the bridge a life expectancy of 50 years and usage class II (NTC18, 2018). The HDRBs fulfil the following ultimate limit state verifications: i.e.  tot ≤5 and  s ≤2, where  tot and  s represent the total design shear strain and the shear strain of the elastomer due to seismic displacement, respectively; the maximum compression axial load (P max ) does not exceed the critical load (P cr ) divided by a safety coefficient equal to 2.0 (i.e. P max /P cr ≤ 0.5); the maximum normal stress of the interior steel shims (  s,max ) is less than the corresponding yielding value (  sy =2350 MPa). The following geometric properties of the HDRBs are reported in Table 1: diameter