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新型复式钢管混凝土墩柱轴压性能试验研究

Axial Compressive Test of a New Composite Cfst Pier Column

【作者】 张燕

【导师】 张玉芬;

【作者基本信息】 河北工业大学 , 建筑与土木工程(专业学位), 2022, 硕士

【摘要】 为了满足现代结构向大跨度、超高层及重载等方面发展的需求,研究人员不断对新型墩柱的受力性能进行研究。本文提出在矩形钢管内置异心双圆钢管的新型复式钢管混凝土墩柱截面形式。该新型构件形式与普通钢管混凝土构件相比对管内混凝土的约束效果更好,拥有更高的承载能力和更好的延性特性。本文首先总结了国内外各种截面形式的钢管混凝土试验成果与理论分析结果,然后采用轴压试验与有限元分析相结合的方法对该类新型墩柱的受力机理与承载力特征进行了分析,并提出新型墩柱轴压承载力计算方法,主要研究内容包括:(1)设计7个钢管混凝土复合墩柱试件,将是否内置圆钢管、混凝土的浇筑截面、试件高度作为考察变量,通过轴压试验研究新型墩柱在上述变量条件下的轴压性能,并分析各个试件在弹性阶段、弹塑性阶段以及下降阶段的变形特征。(2)钢管混凝土复合墩柱的轴压破坏形态有鼓曲破坏、剪切破坏和空钢管破坏这三种。产生这几种不同的破坏形态是因为管内混凝土受到内外钢管的约束后应力状态发生变化。混凝土处于三向受力状态,混凝土的破坏将由“主应力面”的抗压强度和“危险斜面”的压剪强度决定。(3)在矩形钢管内置异心双圆钢管后,其用钢量和极限承载力分别提高约4.69%和22.42%,加载后期轴压延性系数提高约19%,可见内钢管的布置对墩柱整体受力方式有较大影响;混凝土浇筑截面对初始刚度的影响较小但是对极限承载力有一定影响。双圆钢管对混凝土产生套箍作用提高了抗压强度,从而保证墩柱在加载后期能够保持稳定的承载能力;降低墩柱高度会受到端部效应的影响,提高试件的初始刚度,但是对极限承载力以及延性性能的提高不明显。(4)加载初期时钢管与混凝土处于单独工作状态,钢管对混凝土的套箍效应较弱。当构件屈服后,内外钢管的竖向压应变急剧增大,横向应变也迅速发展,这时钢管对混凝土横向变形的套箍约束逐渐明显。因此,提出强度因子系数SI和混凝土贡献率系数CCR来进一步反映钢管和混凝土之间的轴压工作机理。(5)在试验基础上建立了有限元模型,所得模型结果与试验破坏形态基本一致。以墩柱RC88-L为基准,通过应力云图分析混凝土、内外钢管在三个阶段的工作机理并进行轴压性能参数化分析。基于双剪统一强度理论提出新型墩柱的轴压承载力计算方法,所有墩柱Num/Nuj的平均值为0.992,均方差为0.003,说明本文提出的新型墩柱轴压承载力计算方法可为工程应用提出可靠性建议。

【Abstract】 In order to meet the needs of modern structures for long-span,super-high-rise and heavy-load development,researchers continue to study the mechanical properties of new piers.In this paper,a new type of cross-section of compound concrete filled steel tubular pier column with eccentric double circular steel tubes in rectangular steel tubes is proposed.Compared with ordinary concrete-filled steel tubular members,this new type of member has better confinement effect on concrete in the tube,higher bearing capacity and better ductility.Firstly,this paper summarizes the test results and theoretical analysis results of various cross-sections of concrete-filled steel tubes at home and abroad,and then analyzes the mechanical mechanism and bearing capacity characteristics of this new type of pier by combining axial compression test with finite element analysis.The main research contents include:(1)Seven specimens of concrete-filled steel tubular composite pier columns are designed,and whether or not circular steel tubes are built in,the pouring section of concrete and the height of the specimens are taken as investigation variables.Through axial compression tests,the axial compression performance of the new pier columns under the above variables is studied,and the deformation characteristics of each specimen in elastic stage,elastic-plastic stage and descending stage are analyzed.(2)There are three kinds of axial compression failure modes of concrete-filled steel tube composite pier columns:drum failure,shear failure and empty steel tube failure.The reason for these different failure modes is that the stress state of the concrete in the tube changes after it is restrained by the inner and outer steel pipes.Concrete is in a three-dimensional stress state,and its failure will be determined by the compressive strength of the"principal stress surface"and the compressive and shear strength of the"dangerous slope".(3)The steel consumption and ultimate bearing capacity of rectangular steel tubes with eccentric double circular steel tubes are increased by about 4.69%and 22.42%respectively,and the axial ability coefficient is increased by 19%at the late stage of loading.It can be seen that the layout of inner steel tubes has a great influence on the overall bearing mode of piers and columns.The concrete section has little influence on the initial stiffness,but has some influence on the ultimate bearing capacity.The hoop effect of double round steel tubes on concrete improves the compressive strength,thus ensuring that the pier column can maintain a stable bearing capacity at the later stage of loading;Decreasing the pier height will be affected by the end effect and increase the initial stiffness of the specimen,but the ultimate bearing capacity and ductility are not obviously improved.(4)At the initial stage of loading,steel pipe and concrete are in a cooperative state,and the hoop effect of steel pipe on concrete is weak.When the members yield,the vertical compressive strain of the inner and outer steel tubes increases sharply,and the lateral strain also develops rapidly.At this time,the hoop constraint of steel tubes on the lateral deformation of concrete is gradually obvious.Therefore,the strength factor coefficient SI and concrete contribution rate coefficient CCR are proposed to further reflect the working mechanism of axial compression between steel tube and concrete.(5)Based on the test,the finite element model is established,and the model results are consistent with the test failure mode.Based on the pier column RC88-L,the working mechanism of concrete and inner and outer steel pipes in three stages is analyzed through stress nephogram,and the parametric analysis of axial compression performance is carried out.Based on the double shear unified strength theory,the calculation method of the axial compression bearing capacity of the new pier column is proposed.The average value of Num/Nujof all pier columns is 0.992 and the variance is 0.003,which shows that the research on the axial compression bearing capacity of the new pier column in this paper can put forward reliable suggestions for engineering application.

  • 【分类号】TU398.9
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