Comparative analysis of the fire performance of columns made of normal concrete and high strength concrete

Abstract

Considering the use of High strength concrete (HSC) when designing concrete buildings has nowadays become a widespread practice. Choosing HSC as opposed to a normal strength concrete (NSC) becomes relevant when parameters such as cross section reductions, layout modification or self-weight gains are considered.

Plausible issues are met when reducing cross sections towards dimensions where fire resistance problems can occur. Indeed, using smaller HSC cross sections undeniably leads to a faster element’s heating. In addition, HSC encounters higher strength losses and explosive spalling, both not working to its benefit. Explosive spalling resulting from the development of internal pore pressures has not been taken into account for this project. Preventing concrete spalling has been accomplished considering a sufficient amount of polypropylene fibers within the initial mixtures.

This master thesis considers the Eurocode design of a parking garage structure where circular columns have been designed using NSC and HSC, pointing out the plausible cross section reductions. Numerical simulations have then been conducted with the software SAFIR® for the propotype columns related to 5, 10 and 15 stories. Time-resistance curves have been plotted indicating fire resistances RF exceeding three hours for every column. Theoretical modifications have moreover been conducted in order to pursue the limits of the HSC use. The former showed that parameters such as height or support conditions do not significantly aggravate HSC’s fire properties.