PSI - Issue 64

Donatella de Silva et al. / Procedia Structural Integrity 64 (2024) 1806–1814 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

1809

4

Concrete compressive strength (MPa)

40

Steel bars

Feb44k/ B450C

To determine the tensile strength of the strands used for prestressing beams and to determine the cross-sectional area of the bridge deck, average value from structures of similar dimensions were considered. In particular the tensile strength of the strands are 1820 MPa. The geometry of the cross-section is shown below in Figure 1 and in Figure 2.

Figure 1. R.C. bridge deck cross-section

Figure 2. Steel bridge deck cross-section For the prestressed reinforced concrete bridge, the cross-section consists of 8 simply supported straight beams equally spaced. The beams are reinforced with 12 bars and 3/8 stands. At the ends of the section, there are two curb beams with a base width of 0.5m and height of 0.25m, while the deck slab has a thickness of 0.2m. As for the piers, there are 42 24 bars present. The concrete cover for both the beams and piers is 0.05m. Regarding the loads acting on the bridges, these have been determined according to the combination of exceptional load specified by the Italian code. The moving loads, typical of the bridge loads, wasn’t considered in according with this combination in case of fire. These loads are shown in Table 4.

Table 4. Distribution load of the analysed bridges

Concrete bridge

Steel bridge

G 1,k [kN/m G 2,k [kN/m

2 ]

12.5 5.24

G G

1,k [kN/m 2,k [kN/m

2 ] 2 ]

6

2 ]

14.15

4. Fire scenarios In this study, various fire scenarios have been considered. The selection of potential fire scenarios for a structure is important for accurately assessing the structure’s response in fire situations. Real vehicles that can catch fire following accidents have been considered, each characterized by a specific Heat Release Rate (HRR) curve, which represents the thermal power produced by the fire source. These potential fire scenarios have also been characterized by flame diameter. In particular, the vehicles HRR curves by Wright et al. (2012), SFPE Handbook of Fire Protection Engineering (2016) and Chen et al. (2005) adopted were: HGV: semi-trailer with palletized flammable cargo (S1); BUS: a large passenger bus (S2); CAR: (S3); TANKER: standard semi-trailer fuel truck full of gasoline (S4); ½ HGV: this is a semi-trailer truck that is half full of palletized flammable cargo (S5); Motorcycle: (S6); CAR: (S7). Furthermore, scenarios involving two or more vehicles catching fire simultaneously were also considered. Thes