Numerical modelling, parametric analysis and design of UHPFRC beams exposed to fire

A non-linear sequentially-coupled thermal–mechanical finite element (FE) paradigm that reasonably tracks the coupled fire-structure response of ultra-high performance fibre reinforced concrete (UHPFRC) beams subjected to the ISO 834 fire is established and presented. A fire resistance parameter study is conducted on UHPFRC beams via the developed FE paradigm, and then flexural based fire-structural assessment is demonstrated, as an avenue to substantiate the viability of numerical performance-based structural fire design. The parameter study considered two variables, notably heating mechanism and load levels. Comparison of results revealed that the fire-structure response was more severe under the hydrocarbon than the ISO 834 heating mechanism and hydrocarbon fire resistance ratings estimation were found to be 30 minutes lower than those determined using the ISO 834 fire. Predicted failure of the beams under the ISO 834 and hydrocarbon fires was observed at load ratios exceeding 0.6 and 0.4, respectively. By reposing on ACI544’s analytical model for UHPFRC beams in flexure, and numerically acquired heat-transfer response, the time-variant reduced nominal moment capacities of UHPFRC beams were computed. Failure predicted via computed residual moment capacities was somewhat consistent with that reckoned by load ratio parameter study.