Residual Seismic Capacity of UHPC Columns After Fire Exposure

Abstract

This study experimentally investigated the seismic behavior of Ultra-High-Performance Concrete (UHPC) columns after fire exposure. The experimental program included six concrete column specimens reinforced with high-strength reinforcing bars, comprising of two normal-strength concrete (NSC) columns, two high-strength concrete (HSC) columns, and two UHPC columns containing steel and polypropylene fibers at volume fractions of 1.5% and 1.0%, respectively. One column of each type was subjected to a 2-hour fire exposure according to standard heating conditions, while the remaining columns were used as control specimens and not exposed to fire.To assess the fire effect on the seismic performance, all column specimens were subjected to lateral displacement reversals with a constant axial load. The results showed that the lateral strengths of NSC, HSC, and UHPC columns were reduced by 8.0%, 12.0%, and 6.9%, respectively, after fire exposure. Moreover, the effective stiffnesses degraded by 48%, 55%, and 52%, respectively. While the 2-hour fire exposure had a relatively minor effect on the lateral strength of the concrete columns, it considerably reduced the stiffness of the columns irrespective of the concrete material. The use of steel and polypropylene fibers in UHPC was found to be effective in restraining spalling due to fire exposure.