碳化混凝土单调及重复荷载作用下本构关系试验研究

发布时间：2018-06-19 06:00

本文选题：碳化混凝土 + 单调压荷载　；参考：《西安建筑科技大学》2013年硕士论文

【摘要】：当今，全球大气中二氧化碳浓度在持续上升，碳化已成为混凝土结构耐久性劣化的主要因素之一。碳化改变了混凝土内部孔隙结构及化学组分，对混凝土力学性能影响极大。混凝土应力应变关系是混凝土结构抗震性能研究的主要材性依据。本文开展碳化混凝土在单调及重复压荷载作用下的应力应变关系研究，可以进一步完善既有钢筋混凝土结构抗震性能评估理论及对其防灾减灾具有重要的理论研究价值。为探究碳化混凝土在单调及重复压荷载作用下的应力应变关系，本文首先设计了三种强度等级混凝土圆柱体试件，对其中一部分试件进行完全碳化试验，得到六组碳化及未碳化试验试件。对每组试件分别以等应变速率施加单调及重复压荷载，得出试验试件在单调及重复压荷载作用下的应力应变曲线。其次，通过比较碳化混凝土与未碳化混凝土在单调压荷载作用下的应力应变全曲线及重复压荷载作用下的应力应变曲线包络线，分析碳化对混凝土应力应变关系的影响。结果均显示混凝土碳化后峰值应变、极限应变有所减小，且极限应变减小的幅度较大，即混凝土碳化后脆性增加尤其曲线下降段；碳化后峰值应力均得到一定程度的提高，且提高的幅度与混凝土强度成反比关系。再次，本文比较了碳化混凝土在重复压荷载下应力应变加卸载曲线的包络线与单调压荷载下应力应变全曲线，结果显示两者基本一致。最后，本文采用过镇海建议的方程对碳化混凝土在单调压荷载作用下得出的应力应变全曲线及重复压荷载作用下得出的加卸载曲线进行拟合。得到碳化混凝土在单调压荷载作用下应力应变全曲线表达式中参数a、 b的取值，，重复压荷载作用下卸载曲线表达式中参数n及再加载曲线表达式中参数n、 α的取值。初步建立了碳化混凝土的本构方程，可用于既有混凝土结构的非线性分析。
[Abstract]:Nowadays, the concentration of carbon dioxide in the global atmosphere is increasing, carbonation has become one of the main factors of durability deterioration of concrete structures. Carbonation changes the pore structure and chemical composition of concrete, which has a great influence on the mechanical properties of concrete. The stress-strain relationship of concrete is the main material basis for the study of seismic behavior of concrete structures. In this paper, the stress-strain relationship of carbonated concrete under monotone and repeated compression loads is studied, which can further improve the seismic performance evaluation theory of existing reinforced concrete structures and has important theoretical research value for its disaster prevention and mitigation. In order to investigate the stress-strain relationship of carbonated concrete under monotone and repeated compression loads, three kinds of concrete cylindrical specimens with different strength grades were designed firstly, and some of them were carbonized completely. Six groups of carbonized and uncarbonized specimens were obtained. The stress and strain curves of each group of specimens under monotone and repeated compression are obtained by applying monotone and repeated compression loads at the same strain rate. Secondly, by comparing the stress-strain curve of carbonized concrete and uncarbonated concrete under monotonic compressive load and the envelope of stress-strain curve under repeated compression load, The effect of carbonation on stress and strain relationship of concrete is analyzed. The results show that the peak strain and limit strain of concrete after carbonization decrease, and the limit strain decreases greatly, that is, the brittleness of concrete increases, especially the curve decreases after carbonization, and the peak stress increases to a certain extent after carbonization. And the amplitude of the increase is inversely proportional to the strength of the concrete. Thirdly, the envelopes of stress-strain loading and unloading curves of carbonized concrete under repeated loading and unloading are compared with those of stress-strain curves under monotonic compressive loading. The results show that the two curves are basically consistent. Finally, the proposed equation is used to fit the full stress-strain curve of carbonized concrete under monotone compression and the loading and unloading curve under repeated compressive load. The values of parameters a, b in the expression of stress and strain of carbonized concrete under monotone compression load, parameter n in the expression of unloading curve under repeated compression load and parameter n, 伪 in the expression of reloading curve are obtained. The constitutive equation of carbonized concrete is established, which can be used for nonlinear analysis of existing concrete structures.
【学位授予单位】：西安建筑科技大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU375;TU317

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