预应力高强混凝土预制桩承台节点抗震性能研究

发布时间：2018-03-15 08:07

本文选题：桩承台节点　切入点：拟静力试验　出处：《清华大学》2015年硕士论文　论文类型：学位论文

【摘要】：相比灌注桩,预制桩有着桩身质量高,经济环保等优点,随着建筑工业化进程推进,预制桩越来越多地被推广使用。然而,国内预制桩抗震理论研究仍有欠缺,使其在高抗震烈度地区应用受限,这方面研究急需补充。在预制桩抗震性能研究中,桩-承台后浇节点尤为关键,国外相关研究多采用理论分析、试验研究以及数值仿真来评估预制桩承台节点抗震性能。现阶段国内建筑预制桩承台后浇节点常采用桩端钢筋锚固、桩身填芯、桩顶浅嵌固节点构造形式,这一构造设计意在通过锚固保证抗弯承载力,通过填芯提供截面抗剪及避免局部破坏并保证一定的节点变形能力。本文首先利用足尺拟静力试验,对采用这一构造形式的离心成型高强混凝土空心方桩-承台节点进行抗震性能评估,对轴压水平、加载方向、嵌固深度和桩身配筋率等参数进行试验分析。试验节点最终破坏形式为2倍桩径以下的桩身塑性铰破坏,试验表明,从抗震设计角度,该构造下空心方桩轴压比不宜超过0.5,建议工程使用控制轴向荷载上限。本文对采用相同构造方式的复合配筋管桩承台节点进行拟静力试验研究,研究了轴压变化、填芯构造、复合配筋等参数对承压节点性能影响,同时评估了抗拔构造节点性能,另外还设计了一类简化的半刚性节点构造形式,并对其进行节点抗震性能评估。试验结果表明,该节点主要破坏形式为桩头嵌固深度内承台保护层破坏,嵌固失效后承载力由填芯和锚固提供。这一模式下,承压节点表现出了较好的承载力和变形性能,但抗拔节点则表现出了承载力的突然下降和节点脆性破坏。建议工程使用保证一定轴压,并对承台保护层进行配筋加强。结合空心方桩试验,说明桩身和承台性能差异是节点最终破坏模式的决定性因素,同时轴压也是重要因素,大轴压下桩身承担更多损伤。试验结果同时还说明,本研究设计的半刚性节点构造在标准轴压水平下表现出较好的抗震性能,延性较好,耗能指标优异。本文最后利用Abaqus对空心方桩嵌固节点进行数值建模,采用预应力场还原了预制桩后浇节点的施工工艺,利用非线性弹簧模拟锚固钢筋的粘结滑移。通过和试验数据的比对,论证了模型单调加载结果的可靠性,并且指出了模型不适合往复加载的原因。结合数值模型单调加载,本文探讨了轴压、填芯和桩身配筋的影响,其中,轴压对节点最终破坏模式影响最大,单调加载下填芯摩擦系数对性能无显著影响,桩身塑性铰破坏模式下增加配箍能有效改善节点力学性能。
[Abstract]:Compared with cast-in-place piles, prefabricated piles have the advantages of high quality, economic and environmental protection, etc. With the development of construction industrialization, prefabricated piles are more and more widely used. However, the theoretical research on earthquake resistance of prefabricated piles in China is still deficient. It is very important to study the seismic behavior of prefabricated piles, especially in post-cast-in-place joints of pile-cap. Experimental research and numerical simulation are used to evaluate the seismic behavior of prefabricated pile cap joints. At present, the post-cast-in-place joints of prefabricated pile caps are usually constructed in the form of reinforcement anchoring at the end of piles, core filling of piles and shallow embedded joints at the top of piles. The purpose of this structural design is to ensure flexural bearing capacity by anchoring, to provide shear resistance of cross-section through core filling, to avoid local damage and to guarantee certain deformation capacity of joints. In this paper, first of all, full-scale quasi-static test is used. The seismic behavior of hollow square pile-cap joints with centrifugally formed high strength concrete with this structure is evaluated, and the axial compression level and loading direction are evaluated. The test results show that the ultimate failure of the test joint is the plastic hinge failure of the pile body under 2 times the diameter of the pile. The test results show that, from the point of view of seismic design, Under this structure, the axial compression ratio of hollow square pile should not exceed 0.5. It is suggested that the upper limit of axial load should be controlled in engineering. In this paper, the pseudostatic test of composite reinforced pipe pile cap joints with the same structure is carried out, and the variation of axial pressure and the core-filling structure are studied. The effects of composite reinforcement and other parameters on the performance of bearing joints are also evaluated. In addition, a simplified structure of semi-rigid joints is designed, and the seismic behavior of joints is evaluated. The main failure form of the joint is the failure of the protective layer of the pile cap in the depth of the embedded pile head, and the bearing capacity after the embedded failure is provided by the core filling and the anchoring. In this mode, the bearing capacity and deformation performance of the bearing joint are better. However, the anti-jointing point shows a sudden drop in bearing capacity and brittle failure of the joints. It is suggested that certain axial compression should be guaranteed in the engineering, and reinforcement of the protective layer of the cap should be strengthened, and combined with the test of hollow square pile, It shows that the difference between pile body and pile cap performance is the decisive factor of the ultimate failure mode of the joint, and axial compression is also an important factor, and the pile body bears more damage under large axial compression. The test results also show that, The semi-rigid joint structure designed in this paper shows good seismic performance, good ductility and excellent energy consumption index at the standard axial compression level. Finally, numerical modeling of hollow square pile embedded joints is carried out by using Abaqus. The prestress field is used to reduce the construction technology of prefabricated post-pouring joint, and the bond-slip of anchor bar is simulated by nonlinear spring. The reliability of the monotonic loading result of the model is proved by comparing with the test data. The reason why the model is not suitable for reciprocating loading is pointed out. Combined with the monotonic loading of numerical model, the effects of axial compression, core filling and pile body reinforcement are discussed in this paper, in which axial compression has the greatest influence on the ultimate failure mode of joints. The friction coefficient of the core under monotonic loading has no significant effect on the performance, and the mechanical properties of the joints can be effectively improved by increasing the hoop under the failure mode of plastic hinge of the pile body.
【学位授予单位】：清华大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU473.1

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