Existing reinforced concrete (RC) bridges that were designed in the decades between 1950 and 1990 exhibit inadequate structural safety with reference to both traffic loads and hazard conditions. Competent authorities are planning extensive inspections to collect data about these structures and to address retrofit interventions. In this context, Remotely Piloted Aircraft Systems (RPASs) represent a prospect to facilitate in-situ inspections, reducing time, cost and risk for the operators. A practice-oriented methodology to perform RPAS-based surveys is described. After that, a workflow to perform an in-situ RPAS inspection oriented to a photogrammetric data extraction is discussed. With the aim to connect the advantages of the RPAS technologies to the seismic risk assessment of bridges, a simplified mechanic-based procedure is described, oriented to map the structural risk in road networks and support prioritization strategies. A six-span RC bridge of the Basilicata road network, representing a typical Italian bridge typology is selected to practically describe the operating steps of the RPAS inspection and of the simplified seismic risk assessment approach.
Seismic performance assessment of existing bridges, especially those designed without seismic criteria, is paramount in earthquake-prone countries. To perform this task, the Displacement-Based Assessment (DBA) represents a satisfactory trade-off between simplicity and accuracy. After describing the modal analysis-based DBA procedure, a static-based alternative is proposed in this paper, considering its strengths and limitations. Moreover, an extension of the procedure is proposed to derive the force-displacement curve of the bridge (pseudo-pushover capacity curve). The effectiveness of the DBA methodology, implemented via simplified mechanical models, is discussed through parametric analyses to address its practical applications. The DBA approach, both modal and static, is herein adopted for the transverse analysis of a set of 36 reinforced concrete continuous-deck bridges up to six spans, with pier height in the range 8-20m and two different values of the deck transverse stiffness. Additional sensitivity analyses (24 case studies) are conducted to investigate the accuracy of the two approaches considering: 1) the length of the bridge, 2) the amount of longitudinal reinforcement in the piers; 3) different pier typologies. The results are compared to numerical pushover and time-history analyses using three suites of 10 scaled, natural ground motions respectively consistent with low-, medium-and high-seismicity sites.For the majority of the case studies, the resulting performance assessments fall within one standard deviation of the results of the time-history analyses. For this reason, the displacement-based modal or static approaches can represent a valid alternative to numerical non-linear static analyses for continuous bridges with six spans or less.
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