太阳辐射下CFRP加固混凝土箱梁温度场及温度效应研究

发布时间：2018-09-11 20:16

【摘要】：由于碳纤维复合材料(Carbon Fiber Reinforced Polymer,以下简称CFRP)的优势,将碳纤维复合材料应用到箱梁结构的加固设计中已成为一种趋势,这种碳纤维复合箱形截面梁具有良好的力学性能,广泛地应用在国内外桥梁结构中。太阳辐射下CFRP加固混凝土箱梁周围的气象参数对其影响很大,如太阳辐射强度、环境温度及风速等,且外部粘贴的CFRP势必改变原混凝土箱梁温度场,进而影响温度效应。基于平截面假定推导的温度自应力及温度界面剪应力的解析式被应用于梁的工程设计中,但对于具有空间力学行为箱梁理论还需要继续研究。在太阳辐射作用下,建立可以适用于CFRP加固混凝土箱梁的温度自应力及温度界面剪应力分析理论和计算方法非常重要。本文在已有试验研究成果的基础上,针对太阳辐射作用下的CFRP加固混凝土简支箱梁,通过理论推导与数值模拟相结合的方法,系统的研究了CFRP加固混凝土简支箱梁的温度场及其温度效应,主要研究内容包括以下几个方面:(1)基于BP神经网络预测功能,根据太阳辐射下的CFRP加固混凝土箱梁的初始条件及边界条件,及自身热力学材料特点,确定CFRP加固箱梁的主要影响因素,建立其温度场神经网络预测模型,并与试验数据对比分析。(2)基于薄壁箱梁理论,对太阳辐射下的CFRP加固混凝土箱梁的温度自应力及界面温度剪应力,同时结合热弹性力学,复合材料力学等理论,运用能量变分原理建立CFRP加固箱梁的温度自应力及界面温度应力的控制微分方程。并对CFRP加固简支箱梁,在根据现行规范选取太阳辐射竖向温度梯度下,分别推导了CFRP加固简支箱梁温度自应力及其界面温度剪应力的计算公式。(3)只在现行规范规定的箱梁竖向非线性温度梯度作用下,采用共节点,粘结单元及接触单元三种界面处理方式相结合,利用大型通用软件ANSYS建立CFRP加固简支箱梁有限元模型,与理论公式对比分析温度自应力、温度界面应力及其剪力滞效应分布规律。通过本文的研究结果表明:满足一定精度的要求下,可以通过神经网络采用实测的太阳辐射强度、环境温度及风速等气象参数,简单快速地预测出CFRP加固箱梁温度场,本文的预测值与实测值吻合良好,最大误差仅为3.6%;只在竖向非线性温度梯度作用下,本文的温度自应力、界面温度应力及其剪力滞效应解析解与有限元解整体变化规律一致,吻合较好。且CFRP加固混凝土箱梁界面附近区域三种材料的最大值位置不统一,即分别为混凝土跨中边缘、CFRP粘结端部中线,而界面剪应力粘结端部边缘。对于剪力滞问题,通过均一混凝土材料与CFRP加固混凝土箱梁对比可知,粘贴的碳纤维布使纵向应力变化更均匀。
[Abstract]:Because of the advantage of (Carbon Fiber Reinforced Polymer, (CFRP), it has become a trend to apply CFRP to the design of box girder structure, and this kind of CFRP box-section beam has good mechanical properties. It is widely used in bridge structures at home and abroad. The meteorological parameters around the concrete box girder strengthened by CFRP under solar radiation have great influence on it, such as solar radiation intensity, ambient temperature and wind speed, and the external CFRP will change the temperature field of the original concrete box girder and then affect the temperature effect. The analytical expressions of temperature self-stress and temperature interface shear stress derived from the assumption of plane section are applied to the engineering design of the beam, but the theory of box girder with spatial mechanical behavior needs to be further studied. Under the action of solar radiation, it is very important to establish the theory and calculation method of temperature self-stress and temperature interface shear stress which can be applied to concrete box girder strengthened by CFRP. In this paper, based on the existing experimental results, the method of theoretical derivation and numerical simulation is used to strengthen the simply supported concrete box girder by CFRP under the action of solar radiation. The temperature field and temperature effect of simply supported concrete box girder strengthened by CFRP are studied systematically. The main research contents are as follows: (1) based on the prediction function of BP neural network, According to the initial and boundary conditions of CFRP strengthened concrete box girder under solar radiation, and the characteristics of its own thermodynamic materials, the main influencing factors of CFRP strengthened box girder are determined, and the neural network prediction model of temperature field is established. And compared with the experimental data. (2) based on the theory of thin-walled box girder, the temperature self-stress and interfacial temperature shear stress of concrete box girder strengthened by CFRP under solar radiation are combined with the theories of thermoelastic mechanics and composite mechanics, etc. The governing differential equations of temperature self-stress and interfacial temperature stress of box girder strengthened by CFRP are established by using the energy variational principle. For simply supported box girder strengthened by CFRP, the vertical temperature gradient of solar radiation is selected according to the current code. The calculation formulas of temperature self-stress and interface temperature shear stress of simply supported box girder strengthened by CFRP are derived respectively. (3) the common node is used only under the vertical nonlinear temperature gradient of box girder specified in the current code. The finite element model of simply supported box girder strengthened by CFRP is established by using the large scale general software ANSYS, and the temperature self stress is analyzed by comparing with the theoretical formula. Distribution of interfacial stress and shear lag effect. The results of this paper show that the temperature field of the box girder strengthened by CFRP can be predicted simply and quickly by using the measured meteorological parameters such as solar radiation intensity, ambient temperature and wind speed. The predicted value is in good agreement with the measured value, and the maximum error is only 3.6.The analytical solution of temperature self-stress, interfacial thermal stress and shear lag effect is consistent with that of finite element solution under the action of vertical nonlinear temperature gradient. The match is better. The maximum position of the three kinds of materials near the interface of concrete box girder strengthened by CFRP is not uniform, that is, the middle edge of concrete span is the middle line of CFRP bond end, and the boundary shear stress bond end edge. For the shear lag problem, by comparing homogeneous concrete material with CFRP strengthened concrete box girder, it can be seen that the longitudinal stress changes more evenly with the bonded carbon fiber sheet.
【学位授予单位】：兰州交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U441

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