PSI - Issue 62

Gallipoli Maria Rosaria et al. / Procedia Structural Integrity 62 (2024) 940–945 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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3. The Monticello bridge The Monticello is a multi-span truss viaduct that was built in the 1970s. It consists of eleven spans, each consisting of four main girders connected by four transverse tie beams (two at the pier supports and two in the intermediate deck area). Each beam is supported on neoprene supports on both sides so that it can be traced back to a simply supported beam scheme. In addition, each beam has a different degree of degradation (see color scheme in Fig. 3c). Figure 3a shows the locations of the 4.5 Hz velocimeter sensor array (SARA-Electronic Instruments SR04DA) along the edge beam. The sensors were placed in the center and at the supports of each deck (Fig. 3b,d) to evaluate the main structural parameters of each deck with different degrees of degradation (no degradation on the edge decks and medium to high degradation on the midline decks). Seismic noise was recorded for twenty minutes without interrupting the traffic and thus the operation of the viaduct. This data was processed using the FAS, FDD, ANDI and NonPaDan techniques. Of all the results, only the 1 st and 2 nd vertical bending mode shapes are shown (Fig. 3e). As can be seen from Fig. 3c, the 1 st eigenfrequency values are higher for the end decks (1-2-10-11), while they decrease for the intermediate decks (deck 3 to 9); probably this behaviour could be related to the different state of health of each span, which is reflected in the degree of degradation.

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Fig. 3: (a) Geographical location of the Monticello viaduct; (b) Location of the sensors for the different configurations; (c) Map of the degree of corrosion of the Monticello Viaduct with the estimated eigenfrequencies of the eleven spans; (d) Experimental setup for deck 9; (e) Mode shapes corresponding to the first two vertical eigenfrequencies of deck 9. The red, blue and green lines refer to the X (transverse), Y (longitudinal) and Z (vertical) directions, respectively.