基于钢筋锈胀力的混凝土碳化裂缝宽度计算

发布时间：2018-04-14 16:26

本文选题：碳化 + 锈胀力　；参考：《西北农林科技大学》2017年硕士论文

【摘要】：对西北地区渡槽工程进行质量检测发现大部分工程混凝土碳化现象严重,钢筋锈胀导致混凝土开裂,影响到结构承载力,降低了结构的安全性。针对裂缝问题,各国学者相继提出了控制裂缝的要求,裂缝宽度计算至今仍是研究的重点,但由于影响混凝土开裂的原因复杂,普遍适用的裂缝宽度计算公式仍然在研究中。随着计算机技术的飞速发展,有限元软件逐渐被学者们所接受。ANSYS有限元中SOLID65单元特有的属性为模拟混凝土开裂提供了便利。本文应用有限元软件ANSYS建立了单根钢筋均匀锈蚀导致混凝土开裂的数值模型,并通过热-结构耦合作用,模拟了混凝土碳化后钢筋锈胀导致混凝土开裂的锈胀力,并将碳化深度模拟值与试验值进行对比。通过给模型施加不同的荷载,计算了裂缝宽度模拟值,并与经典公式以及实际工程测量值对比,研究了混凝土碳化深度对裂缝宽度的影响规律。结果如下:(1)本文根据热传导原理数值模拟混凝土碳化作用的可行性,通过应用大型通用有限元软件ANSYS较好的模拟了单根钢筋均匀锈蚀导致混凝土开裂的钢筋锈胀力,与理论值对比表明误差在允许范围内。通过给模型施加碳化场,模拟了混凝土碳化后单根钢筋均匀锈蚀导致混凝土开裂的锈胀力,分析了碳化对混凝土开裂的影响规律,发现增加碳化因素后,混凝土开裂所需的钢筋锈胀力减小。(2)本文模拟了混凝土的碳化深度值,并与相同条件下的试验值对比发现结果相近。建立了钢筋锈胀力与混凝土碳化深度的线性回归方程,且相关性较好。利用ANSYS强大的耦合功能,将碳化场与应力场耦合,模拟结果更接近工程实际,为后期模拟混凝土碳化后的开裂变形及计算裂缝宽度提供了理论依据。(3)在热-结构耦合模型的基础上,通过给模型施加不同的荷载,观察钢筋混凝土的裂缝扩展情况,发现荷载在某一范围内,荷载越大,裂缝宽度越大,裂缝条数也增多。施加相同的荷载,模拟不同碳化深度下混凝土的开裂情况,发现碳化深度较小时,对裂缝宽度的影响不明显,当碳化深度超过某一范围时,对裂缝宽度的影响明显。(4)将裂缝宽度模拟值与理论值对比,发现数值模拟得到的裂缝宽度精度满足要求;将模拟值与实际测量值对比,结果表明混凝土碳化深度与裂缝宽度的关系曲线近似相同;根据实际测量值,本文建立了裂缝宽度和碳化深度的关系曲线,近似成二次函数关系;根据数值模拟值,应用MATLAB软件拟合了裂缝宽度和碳化深度以及荷载的二元一次函数关系式,为日后对工程进行耐久性评价奠定了基础。
[Abstract]:The quality test of aqueduct projects in Northwest China shows that the carbonation phenomenon of concrete is serious in most of the projects, and the corrosion expansion of steel bar leads to the cracking of concrete, which affects the bearing capacity of the structure and reduces the safety of the structure.To solve the problem of crack, scholars from all over the world have put forward the requirement of crack control. The calculation of crack width is still the focus of the research. However, due to the complexity of the reasons that affect the crack of concrete, the widely applicable formula for calculating the width of crack is still under study.With the rapid development of computer technology, finite element software has been gradually accepted by scholars. The unique properties of SOLID65 element in the finite element of. ANSYS provide convenience for the simulation of concrete cracking.In this paper, a numerical model of concrete cracking caused by uniform corrosion of a single reinforcing bar is established by using finite element software ANSYS, and the corrosion expansion force of concrete after carbonization is simulated by thermal-structural coupling.The carbonation depth simulation value is compared with the experimental value.By applying different loads to the model, the simulated values of crack width are calculated, and compared with the classical formula and the actual engineering measurements, the influence of carbonation depth of concrete on the crack width is studied.The results are as follows: (1) according to the feasibility of numerical simulation of concrete carbonation based on the heat conduction principle, the corrosion expansion force of concrete cracking caused by uniform corrosion of a single reinforcing bar is well simulated by using a large universal finite element software ANSYS.The comparison with the theoretical values shows that the error is within the allowable range.By applying carbonation field to the model, the corrosion expansion force of concrete cracking caused by uniform corrosion of a single reinforced bar after carbonization is simulated, and the influence of carbonation on concrete cracking is analyzed.In this paper, the carbonation depth of concrete is simulated, and the results are similar to the experimental results under the same conditions.The linear regression equation between the corrosion expansion force and the carbonation depth of concrete is established, and the correlation is good.With the powerful coupling function of ANSYS, the carbonation field and the stress field are coupled. The simulation results are closer to the engineering practice.This paper provides a theoretical basis for simulating cracking and deformation of concrete after carbonization and calculating crack width. On the basis of thermal-structural coupling model, the crack propagation of reinforced concrete is observed by applying different loads to the model.It is found that the larger the load, the wider the crack width and the more the number of cracks.Under the same load, the cracking of concrete under different carbonation depth is simulated. It is found that the crack width is not affected obviously when the carbonation depth is small, and when the carbonization depth exceeds a certain range,The effect on crack width is obvious. (4) comparing the simulated value of fracture width with the theoretical value, it is found that the accuracy of the crack width obtained by numerical simulation meets the requirement, and the simulated value is compared with the actual measured value.The results show that the relationship curve between the carbonation depth and the crack width is approximately the same, the curve of the relationship between the crack width and the carbonation depth is established according to the actual measured value, and the relation between the crack width and the carbonation depth is approximate to the quadratic function, and according to the numerical simulation value,The relationship between crack width, carbonation depth and load is fitted by MATLAB software, which lays a foundation for the durability evaluation of engineering in the future.
【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TV332

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