胶层厚度和初始应力对预应力CFRP片材加固梁界面温度应力的影响研究

发布时间：2018-06-19 14:56

  本文选题：预应力 + CFRP片材　； 参考：《长沙理工大学》2015年硕士论文

【摘要】：研究表明由于CFRP片材与混凝土、钢筋的热膨胀系数存在差异,当环境温度发生变化时在加固结构的粘结界面将不可避免地产生温度应力。而针对在温度变化条件下不同厚度的粘结胶层和不同大小的初始应力对预应力CFRP片材加固混凝土梁界面温度应力影响的研究较少。本试验对粘结胶层厚度为2mm、4mm、6mm和初始应力为CFRP片材抗拉强度的10%、20%、30%的试验梁进行温度试验,通过对试验所测数据进行数值拟合与分析,同时结合理想粘结状态下对加固试验梁的微元段的理论受力分析,寻求在温度变化作用下构件的界面温度应力的分布规律以及粘结胶层的厚度、初始应力大小对加固结构界面温度应力的影响。研究结果表明:1.对于不同的初始应力,相同粘结胶层厚度的试验梁,初始应力越大,试验梁的CFRP片材的应变沿梁分布的数值越大。而对于不同厚度的粘结胶层,相同初始应力的试验梁,粘结胶层厚度越大,应变沿梁分布的数值越小。同时对于厚度为2mm、4mm的粘结胶层的试验梁,其初始应力越大,试验梁的CFRP片材的应变发生急剧变化的区域越大。而胶层厚度为6mm的试验梁CFRP片材应变沿梁变化相对稳定,并无应变急剧变化区域。其应变变化速率也基本保持不变。2.通过数值拟合得到了梁端的预应力CFRP片材应变与温度变化关系式。关系曲线表明,在相同粘结胶层厚度的条件下,初始应力越小,试验梁梁端CFRP片材应变数值越小,应变变化速率发生改变时对应的温度则越高。在相同初始应力的条件下,粘结胶层厚度为4mm的试验梁端CFRP片材的应变变化速率发生改变时所对应的温度最高。3.由试验结果与理论分析结果可知,同一初始应力条件下,粘结胶层的厚度越小,试验梁的锚固端与跨中处的最大界面温度应力越大。同一厚度的粘结胶层的条件下,初始预应力越大的试验梁锚固端与跨中处所对应的最大界面温度应力也越大。因而采用相同的粘结胶层厚度时,建议使用0.1P的初始应力来开展预应力CFRP片材对结构的加固。4.在同一初始应力条件下,当温度在0℃~20℃范围内变化时,粘结胶层厚度为4mm的试验梁的界面温度应力最小;当温度变化在20℃~47℃范围内变化时,粘结胶层厚度为6mm的试验梁的界面温度应力最小。建议在温度较低的寒冷采用4mm的粘结胶层进行预应力CFRP片材加固结构。而在温度相对高的地区采用6mm的粘结胶层进行结构的加固更合适。
[Abstract]:The results show that the thermal expansion coefficient of steel bar is different between CFRP sheet and concrete. When the ambient temperature changes, the thermal stress will inevitably occur at the bond interface of the strengthened structure. However, there is little research on the effect of different thickness adhesive layer and different initial stress on the interface temperature stress of prestressed CFRP sheet reinforced concrete beam under the condition of temperature change. In this experiment, the temperature of the test beam with the thickness of 2 mm and 4 mm / 6 mm and the tensile strength of CFRP sheet with the initial stress of 10% and 20% was tested, and the experimental data were fitted and analyzed numerically. At the same time, combining with the theoretical analysis of the micro-element section of the strengthened test beam under the ideal bond state, the distribution law of the interfacial temperature stress and the thickness of the adhesive layer are sought under the influence of the temperature change. The effect of the initial stress on the temperature stress at the interface of the strengthened structure. The results of the study show that 1: 1. For different initial stress, the larger the initial stress is, the larger the strain distribution of CFRP sheet is along the beam. For different thickness of adhesive layer, the larger the thickness of adhesive layer, the smaller the value of strain distribution along the beam with the same initial stress. At the same time, the larger the initial stress, the larger the area where the strain of CFRP sheet material changes sharply for the test beam with a thickness of 2 mm or 4 mm. However, the strain of CFRP-sheet with thickness of 6mm is relatively stable along the beam, and there is no sharp change region of strain. The strain change rate also remained unchanged basically. 2. The relationship between strain and temperature of prestressed CFRP sheet at beam end is obtained by numerical fitting. The relationship curve shows that the smaller the initial stress is, the smaller the strain value of CFRP sheet at the end of beam is, and the higher the temperature is when the strain rate changes. Under the same initial stress condition, the maximum temperature corresponding to the change of strain rate at the end of the beam when the thickness of the adhesive layer is 4mm is changed. 3. From the experimental results and theoretical analysis results, it can be seen that under the same initial stress condition, the larger the thickness of adhesive layer is, the greater the maximum interfacial temperature stress between the anchoring end and the middle span of the test beam is. Under the condition of the same thickness of adhesive layer, the maximum interfacial temperature stress corresponding to the Anchorage end and the middle of the span of the test beam with larger initial prestress is also greater. Therefore, when the thickness of adhesive layer is the same, it is suggested that the initial stress of 0.1P should be used to strengthen the structure with prestressed CFRP sheet. Under the same initial stress condition, when the temperature varies from 0 鈩，

本文编号：2040263