Effect of cracking and residual deformation on behavior of concrete beams with different scales under fire exposure
Effect of cracking and residual deformation on behavior of concrete beams with different scales under fire exposure
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DOI：
10.1016/j.engstruct.2021.112886
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发表时间：
2021-10
影响因子：
5.5
通讯作者：
H. Zhang;Qi Li;V. Kodur;Hao Lv
中科院分区：
文献类型：
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作者：
H. Zhang;Qi Li;V. Kodur;Hao Lv
本文给出了不同预损伤程度的钢筋混凝土梁的火灾试验结果，以评估预裂变形和残余变形对混凝土梁在火灾作用下的性能的影响。对两组几何尺寸比例为1：2、配筋率相同的钢筋混凝土梁进行了火灾试验。预损伤(裂缝和残余挠度)是在进行火灾试验之前通过在梁上施加不同程度的静载而引起的。记录了在燃烧试验之前和期间的开裂模式和偏转的进展。数据被用来比较有无预损伤的梁的温度场、结构反应和抗火性能。试验结果表明，在火灾暴露前形成的裂缝宽度(小于2 mm)、裂缝数量和长度对靠近火灾裸露表面的混凝土层的温度发展影响有限，而对混凝土内部层(包括梁中纵向钢筋的位置)的温升没有显著影响。在确定包括(或不包括)火灾暴露前形成的残余挠度的预损伤梁的抗火性能时，总挠度对抗火值没有显著影响。轻微的预损伤对梁的抗火性能影响不大，但较大的预损伤(如几乎达到钢筋屈服)会影响梁的抗火性能，特别是在较大尺寸梁的情况下。预损伤程度对较大尺寸梁的抗火性能影响较大，主要是由于尺寸效应的影响。
This paper presents results from fire tests on reinforced concrete beams (RC) with different levels of pre-damage, to evaluate the effect of pre-cracking and residual deformations on the behavior of concrete beams under fire exposure. Two groups of RC beams with proportional geometric dimensions (1:2) and same reinforcement ratio, were tested under fire exposure. The pre-damage (cracking and residual deflection) was induced by applying different levels of static loading on the beams prior to undertaking fire tests. The progression of cracking patterns and deflection prior to and during fire tests were recorded. Data is utilized to compare the thermal field, structural response and fire resistance of beams with and without pre-damage. Results from these tests show that the width (less than 2 mm), number and length of cracks, formed prior to the fire exposure, only have a limited effect on the temperature development in concrete layers closer to the fire exposed surface, but no significant influence on the temperature rise in the internal layers of concrete, including at the location of longitudinal reinforcement in the beam. When determining the fire resistance of a pre-damaged beams, including (or excluding) the residual deflection, formed prior to fire exposure, in the total deflection has no remarkable effect on the fire resistance values. And slight pre-damage has no significant effect on the fire resistance of beams, but major pre-damage (such as almost reaching the yielding of reinforcement) influences the fire resistance, especially in case of larger-scaled beams. The more predominant effect of pre-damage level on the fire resistance in larger-scaled beams is due to the influence of size effects.