Cyclic Behaviour of Heat-Damaged Beam−Column Joints Modified with Nano-Silica, Nano-Titanium, and Nano-Alumina

Abstract

This research is designed to check the potential of modifying concrete with nanomaterials to enhance the cyclic behavior of beam−column joints. It also studies the effect of heat on the cyclic behavior of beam−column joints modified with nanomaterials. Experimental and numerical programs are carried out to explore the cyclic behavior of the heat-damaged and unheated RC joints modified with nanomaterials. Six half-scale exterior RC beam-to-column joints were prepared; two control specimens, two specimens were modified with nano-silica and nano-alumina, and two specimens were modified with nano-silica and nano-titanium. The cement was replaced by 1.33% nano-alumina and 0.67% nano-silica (by cement weight), and the other concrete mix was modified with 1.33% nano-silica and 0.67% nano-titanium, where the cement was replaced by a total of 2% nano-alumina and nano-silica in two specimens, and a total of 2% nano-silica and nano-titanium in the other two specimens. One specimen from each concrete mix was subjected to a temperature of 720 °C for 2 h. The joint specimens were subjected to lateral cyclic loading on the beam and axial loading on the column. Test results showed that the replacement of cement with 2% nano-alumina and nano-silica or 2% nano-silica and nano-titanium is recommended to enhance RC joints’ behavior. The nanomaterials changed the mode of failure of the joint specimens from brittle joint shear failure to a combined type of failure involving the ductile beam hinge and joint shear.