长期荷载作用下CFRP约束混凝土的力学性能研究

发布时间：2018-06-11 18:29

本文选题：CFRP约束混凝土 + 混凝土徐变和收缩　；参考：《西南交通大学》2015年硕士论文

【摘要】：FRP (Fiber Reinforced Plastics)约束混凝土可以有效的提高混凝土柱的强度和延性,在过去的几十年中,虽然国内外学者对短期荷载作用下FRP约束混凝土的力学性能展开了较为深入的研究,但实际工程中的混凝土柱在进行FRP约束加固之前已经产生了较大的变形,在加固之后又要经历长期荷载作用,故要更好的预测实际工程中FRP约束混凝土的长期使用性能,有必要对长期荷载作用下FRP约束混凝土的力学性能进行研究。混凝土和FRP在长期荷载作用下会发生徐变现象,想要较为准确的对长期荷载作用下FRP约束混凝土的力学性能进行模拟,有必要对：(1)混凝土的徐变、收缩性能；(2)FRP的徐变性能；(3)短期荷载作用下FRP约束混凝土的力学性能进行研究,本文按照以上思路,主要研究了以下几点内容：首先,根据RILEM试验数据库,对四种常见的混凝土徐变、收缩预测模型进行了对比,发现GL2000模型与B3模型具有相对较高的准确性,其中GL2000模型更加适用于数值模拟分析；根据收集到的CFRP (Carbon Fiber Reinforced Plastics)徐变数据,对Findley模型进行了修正,得到了适用于CFRP片材的徐变模型。其次,对短期荷载作用下CFRP约束混凝土进行了数值模拟,将模拟结果与试验结果对比后发现：(1)文中使用的增量迭代法能够较为准确的模拟CFRP约束混凝土的应力—应变曲线关系；(2)CFRP约束混凝土的轴向—侧向应变关系对模拟结果影响较大,在收集到的轴向—侧向应变关系计算表达式中,Teng J G公式具有相对较高的准确性。最后,将混凝土徐变、收缩模型,CFRP徐变模型以及短期荷载作用下CFRP约束混凝土的数值模拟程序结合到一起,可以完成长期荷载作用下CFRP约束混凝土的MATLAB编程模拟,模拟结果表明：(1)在不提高轴向持荷水平的前提下,实际加固中FRP片材的使用效率较低,CFRP片材所能提供的侧向约束力通常只有极限侧向约束力的20%到30%左右；(2)由于侧向约束力较小,长期荷载作用下CFRP约束混凝土的轴向应变—时间关系与普通混凝土构件的轴向应变—时间关系相差不大,基本上符合GL2000模型的预测结果；(3)徐变会造成CFRP片材的弹性模量增加,但极限拉应变降低,这会对长期荷载作用后CFRP约束混凝土的力学性能造成一定影响,通过数值模拟可以发现,在长期荷载作用后CFRP约束混凝土的峰值应力基本没有发生变化,但峰值应变降低较为明显,这会影响到CFRP约束混凝土的在长期使用过程中的延性。
[Abstract]:FRP fiber reinforced plastic (FRP) confined concrete can effectively improve the strength and ductility of concrete columns. In the past few decades, although the mechanical properties of FRP confined concrete under short term loads have been studied deeply by domestic and foreign scholars. However, concrete columns in practical engineering have already produced large deformation before FRP restrained reinforcement and have to undergo long-term load after strengthening. Therefore, it is necessary to better predict the long-term performance of FRP confined concrete in practical engineering. It is necessary to study the mechanical properties of FRP confined concrete under long-term load. The creep of concrete and FRP will occur under long term load. In order to simulate the mechanical behavior of FRP confined concrete under long term load, it is necessary to study the creep of concrete. The mechanical properties of FRP confined concrete under short term load are studied. According to the above ideas, the following contents are mainly studied in this paper: firstly, according to the RILEM test database, the mechanical properties of FRP confined concrete are studied. Four kinds of common concrete creep and shrinkage prediction models are compared. It is found that GL2000 model and B3 model have relatively high accuracy, and GL2000 model is more suitable for numerical simulation analysis, and according to the collected CFRP carbon fiber reinforced plastic data, Findley model is modified and a creep model suitable for CFRP sheet is obtained. Secondly, the CFRP confined concrete is numerically simulated under short term load. Comparing the simulation results with the experimental results, it is found that the incremental iterative method used in this paper can simulate the stress-strain curve relationship of CFRP-confined concrete accurately. The axial to lateral strain relationship of CFRP-confined concrete has a great influence on the simulation results. Teng J G formula is relatively accurate in the collected expressions of axial lateral strain relationship. Finally, by combining concrete creep, shrinkage model with CFRP creep model and numerical simulation program of CFRP confined concrete under short term load, MATLAB programming simulation of CFRP confined concrete under long term load can be completed. The simulation results show that: 1) without increasing the axial load holding level, In practical reinforcement, FRP sheets can provide only about 20% to 30% of the ultimate lateral binding force due to the low efficiency of using CFRP sheets) because of the smaller lateral binding force, the FRP sheet can provide only about 20% to 30% of the ultimate lateral binding force. The axial strain-time relationship of CFRP-confined concrete under long-term loading is not different from that of ordinary concrete members. The creep of CFRP-confined concrete will increase the elastic modulus of CFRP sheets, which is basically consistent with the prediction result of GL2000 model. However, the reduction of ultimate tensile strain will have a certain effect on the mechanical properties of CFRP-confined concrete after long term load. Through numerical simulation, it can be found that the peak stress of CFRP-confined concrete basically does not change after long term load. However, the decrease of peak strain is obvious, which will affect the ductility of CFRP-confined concrete during long term service.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528

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