PSI - Issue 62

Laura Ierimonti et al. / Procedia Structural Integrity 62 (2024) 832–839 Ierimonti etal. / Structural Integrity Procedia 00 (2019) 000 – 000

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9) Decision making. Decisions, i.e., do nothing or repair, can be updated on the evidence unveiled from the network at time t . 10) Update damage probabilities in the Decision-Making process; if a repair action is performed, restore the health condition to an undamaged state. Otherwise, maintain conditional probabilities equal to those of the previous time step. 4. Description of the case study The analyzed case study involves a simply supported, post-tensioned single-span concrete bridge. The deck comprises a concrete slab with a thickness of 0.2 m and is supported by three longitudinal post-tensioned I-shaped beams. The total span of the bridge is 32 m. The post-tensioning system (Figure 2b) comprises 5 tendons with varying numbers of strands, each characterized by a diameter of 7 mm. Specifically, cables number 1 and 2, positioned at the beam intradox, are composed of 32 strands, while the remaining tendons (number 3, 4, and 5) consist of 42 strands. The SHM system is composed by 5 inclinometers, equally distributed along the exterior beam (Figure 2a).

Fig. 2. The case study: a) SHM system and reconstructed deflection.; b) Beam’s sections with the indication of tendons T1-T5.

For the numerical application, 9 months of data are artificially simulated, taking into account measurement uncertainties associated with sensor precision and daily traffic flow. Data are recorded with a frequency of one data point every 30 minutes. The deflection of the exterior beam, evaluated according to Eq. 1, is depicted in Fig. 2. For the numerical application, potential losses in the prestress system are selected as DS and 4 different models are considered and associated with node DM: 1) N0, undamaged model; 2) MP1, malfunctioning of cable T5; 3) MP3, malfunctioning of cables T3, T4, T5; 4) MP5, malfunctioning of alle the cables. 5. Main results This section offers an overview of the primary research findings. The main objective is to assess the impact of prestress losses on deflection. In Fig. 3a), the results of a parametric analysis of normalized maximum deflection concerning the undamaged case are presented. This analysis considers the intensity of the damage, ranging from 0.2 to 1. For instance, a value of 1 signifies the absence of a cable, indicating a prestress loss of 100%. The figure highlights that Model MP3 is the most influential, demonstrating a substantial increase in maximum deflection. Subsequently, a damage is simulated based on Model MP3, with an intensity set at 0.5. Fig. 3b) illustrates the Hotelling’s control Chart evaluated within the monitored period, including both undamaged and damaged states. The presence of outliers, i.e., novelty detection, implies the evidence in NY node, as can be depicted from the figure. Fig. 3c) illustrates the results of BMCS in terms of BIC relative differences, i.e., ∆ ൌ ሺ ℳ ሻ − ‹ ሺ ሺ ℳ ͳ ǡ Ǥ Ǥ ǡ ℳ ሻሻ , where the term ‹ ሺ ሺ ℳ ͳ ǡ Ǥ Ǥ ǡ ℳ ሻሻ ൌ ሺ ͵ሻ , which implies an evidence in node DM-SHM. Finally, Fig. 4 provides a summary of the DBN results, drawing inferences on: (i) Novelty detection; (ii) possible DM identified through the simulated model-based SHM and VI; (iii) severity of damage based on VI results; and (iv) repair action.