Effects of Accident Thermal Loading on Shear Behavior of Reinforced Concrete Members

This paper presents the findings from an experimental research project comprised of six full-scale reinforced concrete (RC) beam specimens that were subjected to combination of thermal and mechanical loads. The specimens were designed to represent typical structural members in nuclear structures. These specimens were subjected to accident thermal condition followed by mechanical loading up to failure. The parameters included in the investigation were: 1) maximum accident temperature (300 and 450 degrees F [148.9 and 232.2 degrees C]); 2) concrete clear cover (0.75 and 1.5 in. [19 and 38.1 mm]); and 3) one- or two-sided heating. The experimental results were used to evaluate the flexural and shear stiffness and strength of the tested specimens. The results indicate that accident thermal conditions reduce the shear strength and stiffness of RC beam specimens relative to the ambient values. The nominal shear strength calculated using ACI provisions conservatively estimated the strength of most RC beam specimens at elevated temperatures, but unconservatively estimated the strength of beams with severe heating (450 degrees F [232.2 degrees C ]) and reduced clear cover of 0.75 in. (19 mm).