体外预应力CFRP混凝土薄壁箱梁抗弯性能数值分析

发布时间：2018-05-28 04:10

本文选题：混凝土薄壁箱梁 + 数值分析　；参考：《湖南科技大学》2013年硕士论文

【摘要】：体外预应力CFRP混凝土薄壁箱梁结合了体外预应力技术的优越性和CFRP材料的良好性能，符合环境保护和人类可持续发展要求。为其能推广应用于桥梁结构提供理论依据，本文在体外预应力CFRP混凝土薄壁箱梁抗弯性能试验研究的基础上，利用ANSYS软件对试验箱梁进行了全过程试验模拟和参数分析，主要研究成果如下： 1.利用ANSYS建立试验箱梁有限元分析模型，分析得到的荷载-挠度曲线、荷载-CFRP应力增量曲线以及跨中截面顶、底板混凝土应变分布规律均与试验实测值吻合较好。验证了利用ANSYS软件，选择合适的单元模型和材料本构关系可以较准确地模拟体外预应力CFRP混凝土箱梁受力-变形全过程。 2.通过对CFRP筋初始张拉预应力的参数分析得出：初始张拉预应力从0.3fptk增加到0.65fptk，箱梁的开裂荷载提高幅度达96.4%，虽然CFRP筋的极限应力增量有所降低，但其有效利用率在0.65fptk时达到97.5%，且反拱度满足要求，使得CFRP筋的应力得到了充分的发挥；且初始张拉预应力的提高对箱梁剪力滞效应有一定的抑制作用。建议试验箱梁初始张拉预应力控制在0.65fptk为宜。 3.通过对CFRP筋布置形式的参数分析得出：在初始张拉预应力为0.3fptk的情况下且采用横隔板式转向块时，单折线形式箱梁较双折线形式箱梁的CFRP筋有效利用率有所降低。结合本次试验箱梁的实际情况可知，，合理的转向块设置可以提高CFRP筋的有效利用率。 4.通过对跨高比的参数分析得出：跨高比增大使得开裂荷载、极限荷载均有所降低，相同变形情况下的CFRP筋的应力增量减小，但极限应力增量有所增加；跨高比增大，箱梁跨中截面剪力滞现象呈越弱趋势。 5.通过对配筋率的参数分析得出：增大底板受拉纵筋配筋率对箱梁的开裂能力无明显影响，可以提高箱梁的屈服荷载和极限荷载，但其极限挠度和CFRP筋的极限应力增量降低；弹性范围内受拉纵筋配筋率的改变对箱梁底板剪力滞效应的影响要大于顶板，但总体来说影响幅度都不是特别明显；增大CFRP筋的配筋率可以适当提高箱梁的开裂能力和极限承载能力，但CFRP筋的极限应力增量降低，不利于CFRP筋的有效利用。
[Abstract]:The externally prestressed CFRP concrete thin-walled box girder combines the advantages of external prestressing technology and the good performance of CFRP materials, and meets the requirements of environmental protection and human sustainable development. In order to provide the theoretical basis for its popularization and application in bridge structure, based on the experimental study of the flexural behavior of externally prestressed CFRP concrete thin-walled box girder, the full-process test simulation and parameter analysis of the test box girder are carried out by using ANSYS software. The main findings are as follows: 1. The finite element analysis model of test box girder is established by using ANSYS. The load-deflection curve, the load-CFRP stress increment curve and the strain distribution law of the top and bottom slab concrete are in good agreement with the measured values. It is verified that the whole process of stress and deformation of externally prestressed CFRP concrete box girder can be accurately simulated by choosing appropriate element model and material constitutive relation with ANSYS software. 2. By analyzing the parameters of the initial tensioning prestress of CFRP bars, it is concluded that when the initial tensioning prestress is increased from 0.3fptk to 0.65fptk, the crack load of box girder increases by 96.4m, although the ultimate stress increment of CFRP tendons decreases. However, the effective utilization ratio reaches 97.5 when 0.65fptk is used, and the inverse arch degree meets the requirements, which makes the stress of CFRP tendons fully play, and the increase of initial tensioning prestress can restrain the shear lag effect of box girder to a certain extent. It is suggested that the initial tensioning prestress of test box girder should be controlled in 0.65fptk. 3. By analyzing the parameters of CFRP tendons layout, it is concluded that when the initial tensioning prestress is 0.3fptk and the transversal plate steering block is adopted, the effective utilization ratio of CFRP tendons in single broken line box girder is lower than that in double broken line box girder. The reasonable setting of steering block can improve the effective utilization ratio of CFRP bars. 4. Through the parameter analysis of the ratio of span to height, it is concluded that the increase of the ratio of span to height makes the cracking load and ultimate load decrease, the stress increment of CFRP bars decreases under the same deformation condition, but the increment of ultimate stress increases, the ratio of span to height increases, and the ratio of span to height increases. The shear lag in the middle section of box girder is weaker. 5. Through the parameter analysis of the reinforcement ratio, it is concluded that increasing the reinforcement ratio of the tensile longitudinal reinforcement on the bottom plate has no obvious influence on the cracking ability of the box girder, which can increase the yield load and the ultimate load of the box girder, but the ultimate deflection and the limit stress increment of the CFRP steel bar decrease. The shear lag effect of box girder bottom plate is greater than that of roof plate when the reinforcement ratio of tensile longitudinal reinforcement is changed in elastic range, but the influence range is not especially obvious. The cracking capacity and ultimate bearing capacity of box girder can be improved by increasing the reinforcement ratio of CFRP bars, but the limit stress increment of CFRP bars is reduced, which is not conducive to the effective utilization of CFRP bars.
【学位授予单位】：湖南科技大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU378.2

【相似文献】