Calculation of Thermal Fields of Cracked Concrete at Elevated Temperatures
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pISSN 1226-7988, eISSN 1976-3808 www.springer.com/12205
DOI 10.1007/s12205-020-2057-z
Structural Engineering
Calculation of Thermal Fields of Cracked Concrete at Elevated Temperatures Yanchun Liua, Jijun Miaoa, Jialiang Liua, Guangzhong Bab, and Caiwei Liua a
School of Civil Engineering, Qingdao University of Technology, Qingdao 266033, China College of Ocean Science and Engineering, Shanghai Maritime University, Shanghai 201306, China
b
ARTICLE HISTORY
ABSTRACT
Received 3 December 2019 Revised 17 June 2020 Accepted 6 August 2020 Published Online 30 October 2020
This paper analyzes the effects of cracking on the thermal field of concrete at elevated temperatures. In four concrete specimens with pre-made cracks, fire tests were performed. Then finite element analysis and theoretical analysis were conducted, which have indicated that heat conduction was the primary source of heat transfer in cracked concrete. At last mathematical software MATLAB was used to calculate the temperatures distributions of a simplified model based on theoretical analysis, which were compared with the test results. The results show that as the thermal diffusion of air is far greater than that of concrete, there is an increase in the thermal propagation through the cracked regions in comparison with undamaged regions, and the temperatures increase with the increase of cracks’ widths. The temperature of concrete farther away from a crack was less affected because concrete has a lower thermal diffusion coefficient. The water content of concrete has an impact on the temperature distributions, which should be considered at the early stage of fire when determining the concrete temperature distributions.
KEYWORDS Concrete Cracking Thermal field Fire tests Finite element analysis
1. Introduction Concrete is typically a brittle material vulnerable to cracking under shrinkage and applied loads due to its low tensile strength. After cracking, concrete turns into a discrete material, which provides effective passages for the transport of heat, water, chloride and carbon dioxide into concrete, which accelerates the deterioration of material performance (Zhou et al., 2012; Ye et al., 2013; Liang et al., 2020). The mechanical properties of steel and concrete are closely related to temperature (Xiao et al., 2016; Li et al., 2018; Liu et al., 2019). The concrete’s temperature field should be determined before researching its fire resistance (Chen et al., 2018). In a fire, the heat transfers to the concrete surface by means of three main mechanisms, namely conduction, convection and radiation; then, the heat transfers inward by conduction. However, existing studies regarding the effect of cracks on heat propagation are limited. Ervine et al. (2011) studied the temperature distribution of reinforced concrete (RC) beams with tensile cracks under a constant load in fire. He concluded that the effect of a crack on CORRESPONDENCE Jijun Miao
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ⓒ 2020 Korean Society of Civil Engineers
the temperature field was not significant if the
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