Seismic Behavior Of Reinforcement Concrete Columns After Earthquake Fire

In recent years, frequent building fire accidents have caused enormous loss of property and lives. In order to reduce the possibility of such tragedy or even prevent it from happening, concrete structures are most widely used structural forms at present, it is important to investigate the fire resistance of reinforced concrete (RC) columns which serve as main bearing members in concrete structures.Based on extensive published research, a comprehensive review is made with regard to the fire performance of RC columns in terms of fire endurance and residual structural performance after fire. A statistical analysis of 526 specimens is carried out with the aim of identifying different factors, including:(1) temperature and exposure time; (2) number of heated faces; (3) area and shape of cross-section; (4) strength of concrete and aggregate type; (5) axial load ratio and load eccentricity; (6) longitudinal reinforcing steel; (7) concrete cover, reinforcement stirrup, slenderness ratio and restraint level of the end of column.A few researchers proposed simplified analytical methods in an attempt to calculate the fire resistance of RC columns. A brief summary of these methods are provided in this thesis. In order to evaluate the accuracy and applicability of these methods, test data were compared with analytically calculated results. And the feasibility of these methods is verified through calculating the fire resistance of specimens in the experiment of this paper. It shows that in terms of fire endurance, Kodur and Raut's method can make a conservative estimation whereas Wu et.al's method yields high coefficient of variation (COV) and can only be used in approximate calculation. In terms of residual compressive capacity of RC columns after fire, calculated values of Dotreppe et.al's method can be regarded as lower limit. For Kodur et al's method, though the mean value of the ratios between test data and analytically calculated values is closer to unity, the corresponding high COV may lead to unreliable prediction.From the earthquake occurred in history, studies show that fire is one of the main disasters after earthquake. As there's no published paper about research on fire resistance of RC columns after earthquake, this paper investigated the residual seismic performance of RC columns after earthquake fire, four RC columns under normal temperature and four RC columns that sustained simulated earthquake loading and fire processing were tested cyclically. Given that the diameter of longitudinal rebar and volumetric percentages of stirrups vary from each RC column specimen, their effect on the shear capacity, ductility and ability of energy dissipation of the tested RC columns were also carefully studied. Test results indicate that earthquake fire weakens the shear capacity, shear stiffness and ductility of RC columns but strengthen the ability of energy dissipation. The increase in shear capacity and shear stiffness of RC columns benefits from the increase in diameter of longitudinal rebars and volumetric percentages of stirrups. For specimens with small diameter of longitudinal rebar, increase in volumetric percentages of stirrups can improve the ductility of RC columns after earthquake fire, however impair the ability to dissipate energy.