PSI - Issue 84

Francesco Mariani et al. / Procedia Structural Integrity 84 (2026) 773–780

775

The concrete class of the precast beams is C45/55 and the concrete of the slab is C30/40. The steel for ordinary reinforcement is B450C and the steel for prestress has characteristic tensile yield strength equal to f pk 1860 N/mm 2 .

b)

c)

a)

Fig. 1. Overview of the case study bridge: (a) top view; (b) lateral view; (c) view of the girder ends.

Each girder is reinforced with five prestressing strands and one post-tensioned tendon, each strand having a cross sectional area of 1.39 cm². The single post-tensioned tendon, composed of 12 strands each one with 1.39 cm 2 area, is placed approximately 12.5 cm above the intrados to counteract tensile stresses under service loads. At this stage, the post-tensioning cables are not injected in order to investigate the structure's behaviour under different levels of prestressing load. The prestressing strands are arranged in two layers: one strand at 30 cm from the bottom of the beam and four strands at 6 cm from the bottom, horizontally distributed at distances of 7 cm, 13 cm, 37 cm, and 43 cm from the external edge. The areas of the different types of reinforcement are reported in Table 1.

Table 1. Description of passive and prestressing reinforcement for each beam. Reinforcement type Area Longitudinal rebars 13.06 cm 2 Stirrups (averaged over the beam’s length) 8.24 cm 2 /m Pre-tensioning reinforcement 6.95 cm 2 Post-tensioning reinforcement 16.68 cm 2

The experimental monitoring system implemented on the bridge deck is based on a comprehensive sensor network distributed along both the deck and the girder system, as shown in Figure 2. Overall, the monitoring system comprises a total of 68 acquisition channels. The instrumentation layout was specifically designed to capture both the global and local structural response under operational and environmental conditions. The monitoring system includes ten triaxial MEMS accelerometers (Dewesoft IOLITEiw 3xMEMS-ACC-INC, outdoor version), providing a total of 30 acceleration channels, used to record structural vibrations in both vertical and horizontal directions at a sampling rate of 200 Hz. These sensors are characterized by a noise density of 25 μ g/ √ Hz and a dynamic range of ± 2 g. The same devices are also used as inclinometers, supplying measurements of roll and pitch rotations. In total, 20 inclination channels are acquired at a sampling rate of 20 Hz, allowing the assessment of quasi-static deformations and low-frequency rotational behavior of the structure. Local strain measurements are obtained through five foil strain gauges bonded to selected locations on girders 2 and 3 at mid-span, installed at different heights along the girder depth in order to capture the longitudinal strain distribution. These five strain channels, sampled at 50 Hz, allow monitoring of strain variations associated with bending, thermal effects, and load redistribution. The gauges are connected to dedicated signal-conditioning modules to ensure stable and reliable acquisition. The post-tensioning forces are monitored by means of three load cells, sampled at 50 Hz.