CFRP加固混凝土箱梁日照温度效应研究

发布时间：2018-11-22 10:10

【摘要】：在过去，国内外研究者对加固混凝土结构和构件的力学及使用性能进行了大量的试验研究与理论分析，已取得了丰硕的研究成果。由于应用广泛的箱形梁桥出现得较晚，其加固实例还比较少，随着时间的推移，早期修建的箱形梁桥将相继进入服役后期，加固问题必定会提到议事日程上来。混凝土为热的不良导体，当外部环境出现较大的温度变化时，混凝土结构内外会出现较大的温差，从而导致较大温差应力的出现。CFRP具有不同于混凝土的热物性参数，因此CFRP的外部粘贴使原混凝土箱梁温度场发生改变，同时当温度变化时，CFRP-混凝土组合结构中应力和变形等性能也将发生改变。故对CFRP加固混凝土箱梁的日照温度效应的研究是非常有必要的。本文进行了CFRP加固混凝土箱梁日照辐射作用下温度场及温度应力的试验研究。制作了三片试验梁，三片试验梁均为钢筋混凝土箱梁，具有相同的几何尺寸，梁长3200mm，，横截面高400mm，宽600mm，顶底板厚度均为80mm，腹板厚60mm。在梁体L/4截面布置温度传感器，在跨中截面布置应变片。第一片梁不进行CFRP加固，对其余两片梁进行不同方式的CFRP加固，分别为底面单层加固与U型加固。使用保温材料，采用不同的遮阴方式模拟出三种不同的日照工况，同种工况测试三天，分别获得了各试验梁在不同工况作用下的温度场及温度应力数据，进行了初步的分析和探讨。使用ANSYS软件对CFRP加固混凝土箱梁的日照温度试验进行有限元模拟，将实测数据作为初始条件，结合气象学及大气天文学的知识计算出边界条件，以数组的形式施加给有限元模型，求得各试验梁在不同时刻的温度场；直接将已求得的温度场施加给箱梁模型，计算出各试验梁的温度应力；将实测数据与有限元模拟的数据进行对比分析。经过对实测数据与有限元模拟数据的综合分析最终得出；日照辐射作用下，箱梁顶板测点温度最高值出现在下午15时~16时，而沿高度方向最大温差出现在下午14时~16时。在箱梁同一截面，随着高度的下降，温度场时变规律有明显的延迟现象，不同高度测点温度时变曲线每天有两次交叉点，此时基本不存在温度梯度，箱梁整体温度基本趋于一致；CFRP的粘贴改变了箱梁表面的太阳辐射吸收率，与同等条件下未粘贴CFRP的混凝土表面相比，其表面最高温度高出4~5℃，最终导致了箱梁截面竖向温差增大；不同日照辐射条件作用对CFRP加固混凝土箱梁的竖向温度梯度存在一定的影响，当箱梁腹板位置直接承受日照辐射作用时，其竖向温度梯度发生较大变化，尤其当腹板表面粘贴有CFRP时，这种影响体现的更加明显；未经CFRP加固的混凝土箱梁在日照温度荷载作用下，其顶板大部受拉应力作用，部分受压应力作用，底板基本受拉应力作用，最大拉应力出现在顶板下侧。在顶面粘贴CFRP后，顶板承受温度应力全为受压，底板拉应力大于未加固箱梁的底板拉应力。
[Abstract]:In the past, the research and theoretical analysis of the mechanics and performance of the reinforced concrete structures and components by the researchers at home and abroad have made great achievements. Because of the late appearance of the wide box-beam bridge, the reinforcement of the box-beam bridge is less, and with the passage of time, the early-built box-beam bridge will enter the later stage of service, and the reinforcement problem will certainly be put on the agenda. The concrete is a hot bad conductor, and when the external environment has a large temperature change, a large temperature difference occurs inside and outside the concrete structure, leading to the occurrence of large temperature difference stress. The CFRP has a different thermal physical property than that of the concrete, so the external bonding of the CFRP changes the temperature field of the original concrete box girder, and the stress and deformation in the CFRP-concrete composite structure will also change when the temperature is changed. Therefore, it is necessary to study the solar temperature effect of the CFRP-reinforced concrete box girder. The experiment of temperature field and temperature stress under the action of the solar radiation of CFRP-reinforced concrete box girder is carried out in this paper The three test beams are produced. The three test beams are reinforced concrete box beams with the same geometrical dimensions. The beam length is 3200mm, the cross section is 400mm, the width is 600mm, the thickness of the top base plate is 80mm, and the thickness of the web is 60. mm. The temperature sensor is arranged in the section of the beam body L/ 4, and the cross-section arrangement shall be The first beam is not reinforced with CFRP, and the other two beams are reinforced with CFRP in different ways, which are single-layer and U-shaped on the bottom surface, respectively. The temperature field and temperature stress data of each test beam under different working conditions were obtained by using different shading methods, and the preliminary analysis was carried out. In this paper, the method of ANSYS software is used to simulate the sunshine temperature of the reinforced concrete box girder with CFRP, and the measured data is used as the initial condition, and the boundary condition is calculated by the knowledge of meteorology and atmospheric astronomy, and is applied to the form of an array. The finite element model is used to obtain the temperature field of each test beam at different time points, and the temperature field obtained is directly applied to the box girder model, and the temperature stress of each test beam is calculated; and the measured data and the data of the finite element simulation are The results of the comprehensive analysis of the measured data and the finite element simulation data are as follows: the maximum temperature of the top plate of the box girder under the action of solar radiation is at 15: 15 to 16, while the maximum temperature difference in the height direction appears below In the same section of box girder, the time-varying curve of temperature field has obvious delay in the same section of box girder. The temperature-varying curve of different height measuring points has two cross points every day. At this time, there is basically no temperature gradient, and the whole box girder the temperature is basically consistent; the bonding of the CFRP changes the solar radiation absorption rate on the surface of the box girder, and the maximum temperature of the surface of the concrete is 4-5 DEG C compared with the surface of the concrete which is not pasted with the CFRP under the same conditions, and finally the box girder The vertical temperature difference of the cross-section is increased; the effect of different sunshine radiation conditions on the vertical temperature gradient of the CFRP-reinforced concrete box girder has a certain effect, and when the position of the box girder web is directly subjected to the solar radiation action, the vertical temperature gradient of the box girder is greatly changed, especially when the surface of the web plate The effect of this effect is more obvious when the CFRP is pasted; under the action of the sunshine temperature load, the top plate of the reinforced concrete box girder under the action of sunshine temperature is subjected to tensile stress, the part of the top plate is subjected to compressive stress, the bottom plate is basically subjected to tensile stress, and the maximum tensile stress The force appears on the lower side of the top plate. After the CFRP is attached to the top surface, the top plate is subjected to temperature stress all under pressure, and the tensile stress of the bottom plate is greater than that of the non-reinforcement.
【学位授予单位】：兰州交通大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U441.5;U445.72

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