一种钢筋混凝土框架式涵洞破坏形态与承载力分析

发布时间：2018-10-20 07:15

【摘要】：一种具有独特端部配筋的钢筋混凝土框架式涵洞结构在美国部分地区应用广泛,该类结构主要承受车辆轮压等荷载。这些涵洞使用近半个世纪以来,虽然在涵洞结构的底部出现轻微的纵向裂缝,但涵洞结构却从未出现过重大的损伤和性能退化现象。为进一步明确这类涵洞结构的破坏形态和承载力,为后续该类结构的维护或加固工作提供技术支持,本课题组与美国特拉华大学合作,对该类结构的破坏形态和承载力进行研究。在试验研究的基础上,对四个典型试件的破坏全过程、破坏形态和承载力进行了有限元模拟分析。通过选取合适的材料本构关系,与ABAQUS提供的混凝土损伤塑性模型结合起来,对混凝土损伤塑性本构关系参数的确定方法进行研究,并将试验和有限元模拟结果进行对比,验证所选参数的合理性。在对试件有限元模拟的基础上,分析四个典型试件的破坏全过程,结果表明,在跨中集中加载、两点对称加载和两点非对称加载三种加载方式下,试件的破坏形态均为剪压破坏,在两点对称加载下的承载力约达到跨中集中加载下承载力的两倍。在此基础上,对大宽度试件进行有限元模拟,结果表明:大宽度试件的破坏形态由剪压破坏转变为冲切破坏,试件的竖向位移变化较小,而承载力大大提高。分析表明,对于四个典型试件,当荷载值约达到破坏荷载的一半时,试件端部弯起钢筋才出现较明显的拉力,即弯起钢筋的存在延缓了试件端部混凝土的破坏,与端部不配筋情况相比,对提高试件承载力有一定贡献。分别利用中美欧加四国规范和基于塑性铰假定的框架计算理论,对试件的承载力进行计算分析,结果表明:对于试件的受弯承载力,各国规范得到的计算结果均偏保守,而框架计算理论的计算结果与试验结果符合较好。对于试件的受剪承载力,AASHTO MCFT采用基于修正压力场理论的受剪模型得到的计算结果精度较好。最后,对大宽度试件有效宽度的取值进行了研究,提出了改进方法,并基于改进后的有效宽度值,建立试件的承载力计算公式。
[Abstract]:A reinforced concrete frame culvert structure with unique end reinforcement is widely used in some parts of the United States. Since the use of these culverts for nearly half a century, although there have been slight longitudinal cracks at the bottom of culverts, there has never been any significant damage and performance degradation in culverts. In order to further clarify the failure form and bearing capacity of this kind of culvert structure and provide technical support for the subsequent maintenance or reinforcement of this kind of structure, our team cooperated with the University of Delaware in the United States. The failure mode and bearing capacity of this kind of structure are studied. On the basis of experimental study, the failure process, failure form and bearing capacity of four typical specimens were simulated by finite element method. By selecting appropriate material constitutive relation and combining with the concrete damage plastic model provided by ABAQUS, the method of determining the parameters of concrete damage plastic constitutive relation is studied, and the results of test and finite element simulation are compared. Verify the rationality of the selected parameters. Based on the finite element simulation of the specimen, the failure process of the four typical specimens is analyzed. The results show that, under the three loading modes of concentrated span loading, two point symmetric loading and two point asymmetric loading, The failure modes of the specimens are shear compression failure, and the bearing capacity of the specimens under two-point symmetrical loading is about twice as high as that under concentrated strain-and-span loading. On this basis, the finite element simulation of the large-width specimen is carried out. The results show that the failure mode of the large-width specimen is changed from shear-compression failure to punch-shear failure, the vertical displacement of the specimen is small and the bearing capacity is greatly improved. The analysis shows that for the four typical specimens, when the load value is about half of the failure load, the bending steel bar at the end of the specimen appears more obvious tensile force, that is, the existence of the bending steel bar delays the destruction of concrete at the end of the specimen. Compared with the non-reinforcement at the end, it has a certain contribution to improve the bearing capacity of the specimens. By using the code of China, America, Europe and Canada and the theory of frame calculation based on plastic hinge assumption, the bearing capacity of the specimens is calculated and analyzed. The results show that the calculation results of the flexural capacity of the specimens are conservative. The calculated results of the frame calculation theory are in good agreement with the experimental results. For the shear bearing capacity of the specimen, the shear model based on the modified pressure field theory is used to calculate the shear capacity of the specimen, and the accuracy of the calculation results is good. Finally, the effective width of large width specimen is studied, and an improved method is put forward. Based on the improved effective width value, the bearing capacity calculation formula of the specimen is established.
【学位授予单位】：西安建筑科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U449

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