CFRP加固局部薄弱柱抗震性能研究

发布时间：2018-06-20 01:05

  本文选题：CFRP加固 + 局部薄弱　； 参考：《大连理工大学》2015年博士论文

【摘要】：钢筋混凝土柱的质量受施工及环境因素影响较大,如施工期间混凝土振捣和养护不足、服役期间经受冻融循环等情况都可能造成柱中局部混凝土的劣化。在实际工程中,上述因素导致的局部薄弱柱较为常见,且不易被人们直观地察觉,这会给整体结构安全埋下隐患,甚至可能在地震中发生严重的事故。现代建筑检测技术的发展,使得人们可以更容易通过检测设备发现柱中局部薄弱混凝土的存在并及时采取措施进行加固。碳纤维增强复合材料(CFRP)以其轻质高强、防腐等优势,近年来成为钢筋混凝土加固领域主要的材料之一。各国研究人员已经对FRP加固钢筋混凝土柱的抗震性能进行了大量的试验与理论研究,并取得了诸多成果。本文在前人研究的基础上,对CFRP加固局部薄弱柱的抗震性能进行了试验、有限元及理论分析,并研究了局部薄弱混凝土对柱承载力及延性的影响,以及CFRP对局部薄弱柱抗震性能的修复效果,进而提出了加固局部薄弱柱所需CFRP用量的计算方法。本文主要的研究内容如下：(1)首先分别对1个方截面薄弱柱及非薄弱对比柱、2个圆截面薄弱柱、1个圆截面非薄弱对比柱以及3个圆截面加固薄弱柱进行了拟静力试验。试验结果表明：当局部薄弱混凝土位于柱根时,会对柱的极限承载力、延性造成不利的影响。CFRP加固可以有效地改变局部薄弱柱的破坏形态,显著提高局部薄弱柱的延性及耗能能力,并且可基本恢复薄弱柱的极限承载力,延缓局部薄弱柱纵向钢筋的屈服及刚度的衰减；(2)基于有限元软件OpenSees,采用纤维有限元模型,对上述试件的滞回曲线进行了预测,并通过参数分析,对48种不同工况局部薄弱柱的滞回曲线进行了模拟分析,研究了当局部薄弱混凝土位于柱根时,轴压比、长细比以及CFRP厚度对局部薄弱柱抗震性能的影响。研究表明：CFRP对局部薄弱柱的抗震加固效果随轴压比及CFRP厚度的增大而逐渐增大,随长细比的增加而逐渐减小；(3)基于有限元软件ABAQUS,采用三维有限元模型,对试件进行了数值模拟,预测了各试件的滞回曲线、破坏位置及破坏形态,并通过对42种不同工况的局部薄弱柱的破坏形态及滞回曲线进行预测,研究了不同位置的薄弱混凝土对局部薄弱柱的影响,进而提出了地震中局部薄弱柱破坏位置的判别方法。研究表明：地震作用下局部薄弱柱的破坏发生在柱根及薄弱区两个区域之一,其发生初始破坏的位置同局部薄弱柱的级差率、轴压比以及薄弱区位置有关。CFRP对局部薄弱柱承载力的加固效果与薄弱区混凝土强度、CFRP厚度及拉伸强度有关；(4)基于文献中实测的FRP约束混凝土应力-应变曲线,提出了一个新的FRP约束混凝土应力-应变关系分析模型,并基于平截面假定,采用该模型以及约束混凝土轴压设计模型、约束混凝土偏压设计模型,对压弯状态下CFRP加固局部薄弱柱的荷载-位移曲线进行了预测。研究表明：本文所提的FRP约束混凝土分析模型计算简便、且精度较高。当轴压比、长细比较大、约束混凝土强度较低、CFRP厚度较大时,使用偏压应力-应变关系预测的荷载-位移曲线更为准确。
[Abstract]:The quality of reinforced concrete columns is greatly influenced by the construction and environmental factors. For example, concrete vibration and maintenance are insufficient during construction, and the conditions of freezing and thawing during service may cause the deterioration of the concrete in the column. In practical engineering, the local weak columns caused by these factors are more common and are not easily detected by people. The development of modern building detection technology makes it easier for people to detect the existence of weak concrete in the column and take measures to reinforce it in time. Carbon fiber reinforced composites (CFRP), with its lightweight, high strength and anticorrosion, can be found more easily. In recent years, it has become one of the main materials in the field of reinforced concrete reinforcement. Many researchers have done a lot of experiments and theoretical studies on the seismic performance of reinforced concrete columns reinforced by FRP, and have made many achievements. On the basis of previous studies, this paper tries to test the seismic performance of a local weak column reinforced by CFRP. The effect of the local weak concrete on the bearing capacity and the ductility of the column and the effect of CFRP on the seismic performance of the local weak columns are studied, and the calculation method of the amount of CFRP for strengthening the local weak columns is proposed. The main contents of this paper are as follows: (1) first of all 1 square columns and weak columns respectively. Non weak contrast column, 2 circular cross section weak column, 1 circular cross section non weak contrast column and 3 circular cross section reinforced weak column are tested. The test results show that when the local weak concrete is located at the root of the column, the ultimate bearing capacity of the column, the ductility caused by the adverse effect of.CFRP reinforcement can effectively change the local weak column. The failure mode can significantly improve the ductility and energy dissipation capacity of the local weak column, and can basically restore the ultimate bearing capacity of the weak column, postpone the yield and stiffness attenuation of the longitudinal reinforcement of the local weak column. (2) based on the finite element software OpenSees, the fiber finite element model is used to predict the hysteresis curve of the above specimens and through the parameters. The hysteretic curves of local weak columns in 48 different working conditions are simulated and analyzed. The effects of axial compression ratio, length to length ratio and CFRP thickness on the seismic performance of local weak columns are studied when the local weak concrete is located at the root of the column. The study shows that the effect of CFRP on the local weak columns increases with the ratio of axial pressure and the thickness of CFRP to the local weak columns. Gradually, it gradually decreases with the increase of slenderness ratio; (3) based on the finite element software ABAQUS, the three-dimensional finite element model is used to simulate the specimen, the hysteretic curve, the failure position and the failure form of the specimens are predicted, and the failure mode and hysteresis curve of the weak columns in the 42 different working conditions are predicted. The influence of the weak concrete in different positions on the local weak column is investigated, and the method of judging the failure position of the local weak column in the earthquake is put forward. The study shows that the damage of the local weak column is one of the two regions of the column root and the weak area under the earthquake action, and the initial broken position is the same as the difference of the local weak column and the axial pressure. The reinforcement effect of.CFRP on the bearing capacity of the local weak column is related to the strength of concrete in the weak zone, the thickness of CFRP and the tensile strength of the weak region. (4) a new stress strain relationship analysis model of the concrete constrained concrete is proposed based on the measured FRP stress strain curve in the literature, and it is based on the assumption of the flat section. By using the model and constrained concrete axial compression design model, the load displacement curve of the local weak column strengthened by CFRP is predicted by constrained concrete bias design model. The study shows that the FRP constrained concrete analysis model proposed in this paper is simple and accurate. When the strength of the aggregate is low and the thickness of CFRP is large, the load displacement curve predicted by using the biaxial stress-strain relationship is more accurate.
【学位授予单位】：大连理工大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TU375.3;TU352.11
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本文编号：2042188