Date of Award
Master of Engineering Science
Civil and Environmental Engineering
Dr. Maged Ali Youssef
Concrete and steel mechanical properties experience significant deterioration during fire events. Following a fire event, these properties were found to improve with time towards their original values. As a result, the overall capacity of the fire-damaged structure increases after the end of fire exposure. A review of the available models to predict concrete and steel mechanical properties during heating, cooling, and post-cooling stages is conducted in this study. When needed, new models are developed based on the available experimental data. Investigated mechanical properties include concrete compressive strength, tensile strength, initial modulus of elasticity, bond strength, and strains. Yield strength of steel reinforcement is also reviewed to account for their confining effect and contribution to axial and flexural capacities of concrete sections. The study proposes a general stress-strain relationship for concrete that can be used during or after a fire event. This relationship provides an improved knowledge of the safety of concrete structures during or after being exposed to a fire. A heat transfer model based on the Finite Difference Method (FDM) is programmed. The temperature gradient through siliceous square sections is therefore estimated at different heating periods for a standard ASTM-E119 fire. The representative models for concrete thermal properties are given. The temperature distribution obtained using the developed program is validated using available experimental work. Only normal strength concrete is assumed in this study such that spalling problems are less susceptible to occur during the heating period. m A fibrous sectional analysis that can utilize utilizing the proposed material models and the results of the heat transfer model is developed. The predictions of the developed analysis method are compared with other experimental and analytical work for different concrete sections. A good agreement is found between the experimental data and the proposed analysis methodology. The validation includes both deformation and strength criteria. Using the proposed sectional analysis methodology, a total of 24 columns are analyzed to study the effect of different parameters on the axial and flexural capacities of fire- damaged concrete sections. The studied factors are concrete compressive strength, reinforcement ratio, section dimensions, and fire duration. Two columns are added to investigate the effect of the post-cooling age on the overall section capacity. The considered ages are one month and one year after extinguishing the fire. Original axial and flexural capacities are partially recovered after one year due to the continuous regain of concrete and steel mechanical properties during the Post-Cooling stage.
El-Fitianv, Salah El-Din Farouk, "ASSESSING THE CAPACITY OF FIRE-DAMAGED CONCRETE ELEMENTS USING SECTIONAL ANALYSIS" (2008). Digitized Theses. 4247.