PSI - Issue 64

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

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Figure 4. a) temperature in the most fire-exposed reinforcement bar in the prestressed reinforced concrete bridge; b) the mean temperature of the steel beam for the steel-concrete composite bridge.

In Figure 5 and in Figure 6, the evolution of temperature within the cross-section of the prestressed reinforced concrete bridge and the composite bridge, respectively, is depicted at different moment: at t=0min; at the HRR peak t=15min; at the end of the HRR t=100min for the HRR curve of scenario 2.

b)

c)

a)

Figure 5. Evolution of the temperature inside the main beam for the steel-concrete bridge at different time step: a) t=0 min; b) t=15 min; c) t=100 min.

a)

b)

c)

Figure 6. Evolution of the temperature inside the main beam for the stell-concrete bridge at different time step: a) t=0 min; b) t=15 min; c) t=100 min.

After the thermal analyses were completed, mechanical analyses of the analyzed structures were carried out. The model assumptions, such as material properties, boundary conditions, and load scenarios, were carefully defined based on realistic bridge design specifications and fire characteristics. The response parameters considered were the maximum vertical displacement at the midspan of the bridge deck and the residual vertical displacement. These displacement values were normalized with respect to limit displacements based on the considered performance level. Using the obtained values, a fragility analysis was performed, determining fragility curves based on data analysis through Cloud Analysis. 6. Results and discussion An example of the Cloud Analysis results is reported in the Figure 7 for the prestressed reinforced concrete bridge, considering the peak of heat release rate for characterized fire scenarios. In this case, once the fire scenarios are applied to the structure, the maximum demand-to-capacity ratio for the chosen performance level is determined.

b=0.58 a=0.07 β (DCR|IM) = 0.19 b=1.72 a=0.00 β (DCR|IM) = 0.78

PL III

PL IV Res