Residual behavior of reinforced concrete corbels after exposure to elevated temperatures

Abstract

AbstractMany precast concrete structures make use of corbels, which are small cantilevers that transfer eccentric point loads to columns or walls. When such structures experience a fire event, the residual strength of their corbels may need to be evaluated. This paper examines the residual behavior of reinforced concrete corbels exposed to elevated temperatures. Sixteen full‐scale double‐corbel specimens with two shear span‐to‐depth (a/d) ratios and different reinforcement layouts were fabricated and tested in ambient conditions or after exposure to temperatures of 550°C and 780°C. The load–displacement behavior, failure mode, and load‐carrying capacity of the specimens were investigated. Exposure to 550°C and 780°C reduced the strength of the specimens by up to 22% and 51%, respectively and increased the displacement at failure between 100% and 150%. The strut‐and‐tie method in ACI 318‐19 provided conservative estimates of the residual capacities of heat‐affected corbels if calculations are based on residual mechanical properties at the surface or average mechanical properties between surface and core of the specimens. When exposed to heat, corbels with smaller a/d ratios showed better strength retention if horizontal distributed reinforcement is used while corbels with larger a/d ratios better retained their strength if employing bidirectionally distributed reinforcement.