RESIDUAL CAPACITY OF FIRE EXPOSED REINFORCED CONCRETE COLUMNS

Event Date/Time: 
August 28, 2017 - 1:00pm
Event Location: 
3546D Engineering
Speaker: 
Derek Hibner
Master's Thesis Defense

Abstract

Fire represents one of the most severe environmental loading conditions that a structure may experience during its design lifetime. Reinforced Concrete (RC) structural members can experience some level of damage following moderate or severe fire exposure. To ensure safe future use of the structure, and to develop adequate retrofitting measures for fire damaged concrete members, it is essential to evaluate the residual capacity of RC members following fire exposure and prior to re-occupancy. A limited number of experimental studies and approaches exist today that accounts for the residual capacity of fire exposed RC columns. Therefore, experimental studies have been undertaken as part of this research to understand the post-fire behavior of RC columns exposed to realistic fire scenarios. Two full-scale normal strength concrete (NSC) columns have been cast and subjected to realistic restraint, loading and fire exposure conditions. The experimental studies conducted indicate that peak rebar temperatures can occur up to 100 minutes and 80 minutes after the end of the heating phase of a 90-minute and 120-minute fire exposure, respectively. The post fire residual capacity testing indicated that the RC columns can retain up to 34% of its real nominal capacity for a 90-minute exposure and up to 29% for a 120-minute exposure. However, much of the design capacity of columns is retained after exposure to fire. In addition to the experimental studies undertaken, a numerical model developed using the commercially available finite element (FE) software, ABAQUS, is used to predict the thermal and mechanical response of RC columns before, during and after realistic fire exposure. This FE model accounts for realistic material behavior at elevated temperatures, load conditions and fire exposure scenarios. The two tested columns were analyzed using the developed model and predictions from the model are compared against data for fire tests in all three stages of analysis. The comparisons showed a good correlation between the predicted and experimental values of fire resistance, pre-fire capacity, post-fire residual capacity and axial displacements during heating, cooling and residual phases.