Post-fire behaviour of eccentrically loaded reinforced concrete columns confined by circular steel tubes

Abstract

Abstract:The post-fire behaviour of eccentrically loaded reinforced concrete columns confined by circular steel tubes, also known as circular steel tube confined reinforced concrete (STCRC) columns, is investigated in this paper. A total of 12 experiments were conducted on eccentrically loaded circular STCRC stub columns after exposure to the ISO 834 standard fire, including both the heating and cooling phases. The temperatures across the tested sections, the axial load versus lateral displacement responses and the strains in the steel tubes were all measured and discussed. A finite element (FE) model was developed using the program ABAQUS, and validated against the test results from the present study, as well as related studies. Parametric studies were then performed to identify the influences of key parameters on the residual capacity of the eccentrically loaded STCRC columns, including eccentricity ratio, heating time, cross-sectional diameter, slenderness ratio, material strengths, steel tube to concrete area ratio and reinforcement ratio. Finally, a simplified method was proposed for predicting the residual load-bearing capacity of the eccentrically loaded STCRC columns after fire exposure.

Experimental and Numerical Studies of Reinforced Concrete Columns Confined by Circular Steel Tubes Exposed to Fire

“…Hence, the fire and post-fire behavior of STCRC columns is the focus of ongoing research by the authors. The post-fire response of STCRC columns, including their cross-sectional behavior, buckling behavior and behavior under combined compression and bending, were experimentally and numerically studied by the authors and presented by Liu et al (2014), Yang et al (2015) and Liu et al (2016), respectively. The present paper focuses on the performance of STCRC columns subjected to standard fire conditions, in order to evaluate the fundamental behavior of these columns in fire and to obtain essential information to underpin their fire safety design.…”

Fire and post-fire performance of circular steel tube confined reinforced concrete columns

“…Comparisons between predicted and test fire resistance is shown in Fig.11. The design method for predicting residual load-bearing capacity of the circular STCRC columns can be found in [16][17][18]. Comparisons between predicted and test load-bearing capacities of the circular STCRC columns are illustrated in Fig.12.…”

“…A total of 47 circular STCRC columns after exposure to ISO 834 standard fire were tested, including 21 axially loaded stub columns [16], 12 eccentrically loaded stub columns [17] and 14 axially loaded slender columns [18]. The considered parameters were heating time (0, 30min, 60min), length to diameter ratio (3,6,10), concrete strength (C30, C50), cross section dimension (200mm, 250mm) and load eccentricity (0, 25mm, 50mm).…”

“…The considered parameters were heating time (0, 30min, 60min), length to diameter ratio (3,6,10), concrete strength (C30, C50), cross section dimension (200mm, 250mm) and load eccentricity (0, 25mm, 50mm). More details can be found in [16][17][18]. The specimens were heated in an unstressed condition, which is considered to be more conservative than under load in terms of evaluating the residual strength of concrete after fire [19][20][21][22].…”

“…(c) axially loaded slender column [18] (a) axially loaded stub column [16] (b) eccentrically loaded stub column [17] The finite element model was then employed to conducted parametric studies to investigate influences of key parameters on the fire resistance or residual load-bearing capacities of the STCRC columns. Parametric study results are not presented herein for the limited paper length.…”