PSI - Issue 84

Fabio Mazza et al. / Procedia Structural Integrity 84 (2026) 944–951

951

(a) Points in proximity of the end steel plates.

(b) Points at half isolator height.

Fig. 10. Fire fragility curves of a central HDRB.

5. Conclusions An extensive FE thermal analysis of a composite bridge, seismically isolated at the top of piers and placed at road intersections above a road where vehicle incidents occur, is carried out in order to evaluate its residual load capacity following hydrocarbon fires. The fire response has resulted in the exceedance of the service limit state of PC beams, due to the degradation of prestressing steel and the overall loss of prestressing on the deck, and ultimate limit state of HDRBs, characterized by a significant degradation when a critical temperature was exceeded. The effects of the FE discretization in thermal computations are analysed by carrying out both 2D and 3D modelling of HDRBs, observing a significant temperature increase at the middle height of 3D isolators, with an almost constant profile along the central vertical axis, differently from 2D isolators whose temperature increases moving away from the centre. Finally, fire fragility curves of HDRBs highlight their vulnerability to most of the fire scenarios at least up to one third of their diameter, and this behaviour is more evident for the points placed at half isolator height. References Chen, C.J., Tsai, M.J., Ji, B.C., Wu. C.W., Pu. J.Y., Lin. T.H., 2005. Burning analysis of motor scooters. Fire Safety Science 8, 671-680. de Silva, D., Miano, A., De Rosa. G., Di Meglio, F., Prota, A., Nigro, E., 2025. Analitycal fire fragility assessment for bridges considering fire scenarios variability. Engineering Structures 325, 119442. DM6792, 2001. Norme funzionali e geometriche per la costruzione delle strade. D.M. 11-01-2001, Italian Ministry of the Infrastructures and Transports, Rome, Italy (in Italian). Eurocode 2, 2004. Design of concrete structures - Part 1-2: General rules, structural fire design. C.E.N., European Committee for Standardization. Gernay, T., Franssen, J.M., 2017. Modeling structures in fire with SAFIR ® : theoretical background and capabilities. Journal of Structural Fire Engineering 8(3), 300-323. Jalayer, F., De Risi, R., Manfredi, G., 2015. Bayesian Cloud Analysis: efficient structural fragility assessment using linear regression. Bulletin of Earthquake Engineering, 13, 1183-1203. Lecocq, A., Bertana, M., Truchot, B., Marlair, G., 2012. Comparison of the fire consequences of an electric vehicle and an internal combustion engine vehicle. 2. International Conference on Fires in Vehicles - FIVE 2012, Chicago, United States, 183-194. Lucon, M., Baragatti, P., Possidente, L., Tondini, N. 2022. Experimental fire response of seismic elastomeric bearings. Engineering Structures 254, 13806. Mazza, F., Alesina, A. 2019. Fragility analysis of R.C. seismically-isolated structures with residual mechanical properties after fire exposure. Soil Dynamics and Earthquake Engineering 121, 383-398. NTC18, 2018. Norme tecniche per le costruzioni e relative istruzioni. D.M. 17-01-2018 and C.M. 11-02-2019, Italian Ministry of the Infrastructures and Transports, Rome, Italy (in Italian). Peacock, R.D., Jones, W.W., Reneke, P.A., Forney, G.P. 2008. CFAST-consolidated model of fire growth and smoke transport (version 7), User ’ s Guide, NIST Special Publication 1041. Wright, W., Lattimer, B., Woodworth, M., Nahid, M., Sotelino, E., 2013. Highway Bridge Fire Hazard Assessment - Draft Final Report. NCHRP Program Transportation Research Board of the National Academies. Virginia Polytechnic Institute and State University, Virginia, USA. Shakya, A.M., Kodur, V.K.R. 2016. Effect of temperature on the mechanical properties of low relaxation seven-wire prestressing strand. Construction and Building Materials 124, 74-84. Zhang, G., Zhao, X., Lu, Z., Song, C., Li, X., Tang, C. 2022. Review and discussion on fire behavior of bridge girders. Journal of Traffic and Transportation Engineering 9(3), 422-446.