基于DIC与应变测试的混凝土中钢筋锈胀应力分析
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摘要
钢筋锈胀应力超过混凝土抗拉强度将导致混凝土开裂,直接测试钢筋锈胀应力有助于预测混凝土的开裂时间。本工作对钢筋混凝土外渗海水并进行恒电位加速腐蚀,采用数字图像相关(DIC)技术测试混凝土表面应变,利用空心钢筋测试钢筋内表面应变,基于弹性力学推导钢筋锈胀应力模型。结果表明:利用DIC和空心钢筋可以测试混凝土表面及钢筋表面的应变随时间的演变规律;混凝土上表面凹槽边缘存在应力集中,钢筋上表面产生压应力并导致混凝土保护层开裂;外渗海水的恒电位加速腐蚀导致混凝土中钢筋出现非均匀锈蚀,混凝土开裂的锈胀应力在3 MPa,开裂时间在25 h。
It is universally known that concrete would crack when expansion stress induced by corrosion of reinforcing bar exceeds the tensile strength of concrete. And directly measuring the corrosion stress of rebar contributes to predicting the cracking time of concrete. In this paper, acce-lerated corrosion of reinforced concrete was carried out by constant potential corrosion and seawater penetration. The digital image correlation(DIC) was employed to test the surface strain of concrete, and the hollow reinforcing bar was adopted to test its internal surface strain. And the corroding stress model of reinforcing bar was derived based on the elastic mechanics theory. The results indicated that DIC and hollow reinforcing bar were effective for measuring the surface strain evolution of concrete and reinforcing bar. It could be observed by DIC that there was stress concentration on the groove edge of the concrete surface. And compressive stress occurred on the upper surface of the reinforcing bar, which leaded to the cracking of concrete cover. The constant potential accelerated corrosion with seawater penetration caused the non-uniform corrosion of the reinforcing bar in the concrete, resulting in the cracking of concrete at the corrosion stress of 3 MPa, and corrosion duration of 25 h.
It is universally known that concrete would crack when expansion stress induced by corrosion of reinforcing bar exceeds the tensile strength of concrete. And directly measuring the corrosion stress of rebar contributes to predicting the cracking time of concrete. In this paper, acce-lerated corrosion of reinforced concrete was carried out by constant potential corrosion and seawater penetration. The digital image correlation(DIC) was employed to test the surface strain of concrete, and the hollow reinforcing bar was adopted to test its internal surface strain. And the corroding stress model of reinforcing bar was derived based on the elastic mechanics theory. The results indicated that DIC and hollow reinforcing bar were effective for measuring the surface strain evolution of concrete and reinforcing bar. It could be observed by DIC that there was stress concentration on the groove edge of the concrete surface. And compressive stress occurred on the upper surface of the reinforcing bar, which leaded to the cracking of concrete cover. The constant potential accelerated corrosion with seawater penetration caused the non-uniform corrosion of the reinforcing bar in the concrete, resulting in the cracking of concrete at the corrosion stress of 3 MPa, and corrosion duration of 25 h.
引文
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3 Niu D T,Wang Q L.Industrial Construction,1996,26(4),8(in Chinese).牛荻涛,王庆霖.工业建筑,1996,26(4),8.
4 Liu Y.ACI Materials Journal,1998,95(6),675.
5 Shen Y,Wang L F,Zhang C J.Value Engineering,2016,35(32),134(in Chinese).沈阳,王丽芬,张昌进.价值工程,2016,35(32),134.
6 Destrebecq J F,Toussaint E,Ferrier E.Experimental Mechanics,2011,51(6),879.
7 Yamaguchi I.Journal of Physics E Scientific Instruments,2000,14(11),1270.
8 Peters W H,Ranson W F.Optical Engineering,1982,21(3),213427.
9 Iskander M.Materials Today,2010,13(12),52.
10 Gencturk B,Hossain K,Kapadia A,et al.Measurement,2014,47(1),505.
11 Han Y Y,Liu N S,Cai Y C.Journal of Civil and Enviromental Enginee-ring,2015(s2),51 (in Chinese).韩依颖,刘乃盛,蔡永昌.土木建筑与环境工程,2015(s2),51.
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15 Xu Z L.Elastic mechanics theory,Higher Education Press,China,2013(in Chinese).徐芝纶.弹性力学简明教程,高等教育出版社,2013.