Thermal analysis of reinforced concrete chimneys with fiberglass plastic liners in uncontrolled fires

• Calculation of fire duration and temperatures for RC chimneys with FRP liners.
• Implementation of the method for various chimney designs with 1–4 liners.
• Estimation of post-fire residual strength based on modified ACI 307 procedure.
• Identification of critical configurations within the practical design limits.

This paper presents a simple method to calculate fire duration and flue gas temperatures for reinforced concrete (RC) chimneys with fiberglass reinforced plastic (FRP) liners based on experimentally determined burning characteristics of the liner material. Implementation of the method to calculate fire durations and the transient heat transfer conditions is demonstrated for single- and four-liner chimneys. A parametric study is carried out for chimney designs and geometries ranging from 100 m to 300 m in height and 7 m to 40 m in diameter, with 1–4 liners and varying opening configurations. The results are used to identify a limited number of cases for which the RC chimney undergoes the most extreme reduction in its post-fire residual strength. Analytical estimations of the chimney residual strength after the fire are obtained using a method established based on the procedure outlined in the American Concrete Institute (ACI) 307 Standard for chimney strength calculations. Calculations for a series of critical configurations of RC chimneys, with FRP liner geometries within the practical design limits detailed in this paper, show that the post-fire structural capacity of the chimneys would not lead to catastrophic failures especially because the chimney is not expected to see other high design lateral loads such as wind or earthquake simultaneously.