桥梁H型钢桩抗震性能研究
发布时间：2018-08-16 07:38
【摘要】：目前,H型钢桩基础,因其截面积相对较小、贯穿力强、对土体的扰动小、易改变长度等优点,而被广泛应用于桥梁工程中。尤其在美国,有上千座桥梁采用H型钢桩基础。在正常使用阶段,相对桩基所受的巨大的轴向力,水平力对H型钢群桩基础的影响似乎很小。但是,对于一些极端情况,如地震、船撞,此时,H型钢桩基础将经历非常大的水平变形,水平力对桩基的影响就显得至关重要。众所周知,单桩的水平受荷反应是群桩水平受荷分析的基础,而单桩的动力特性研究往往需要其静力性能作支撑,因而有必要研究在水平荷载作用下桥梁H型钢单桩的相关静力性能。基于以上所述,本文开展了桥梁H型钢桩抗震性能试验和理论性研究。本文首先对六十多年来水平受荷桩的试验研究进行了详细汇总和分类,为今后的相关理论研究提供全面性的试验数据基础。同时作者对水平受荷桩的分析方法进行了总结和归类,并详细阐述了各自优缺点。这些理论分析方法为将来出现的新型桩基础在水平荷载作用下的特性研究提供了全面详实的分析基础,同时也为将来进一步研究极端动力水平荷载下的桩基特性提供了一个全面的静力方法分析基础。而后本文制定了水平受荷H型钢桩的试验规划。试验分为四个单桩试验,H型钢桩单调强轴、弱轴方向水平加载试验,以及H型钢桩循环往复强轴、弱轴水平方向加载试验。试验中,H型钢桩为模型桩,缩尺比例为1/3,采用事先预埋方式,砂土采用夯实方式填埋。从试验结果看出,无论是强轴还是弱轴加载,H型钢桩在大变形下都具有较为稳定的性能。在水平加载的初始阶段,即小变形条件下,H钢桩-土体的滞回曲线呈现捏拢状,整体特性主要由土体所控制;而在大变形条件下,H钢桩-土体的滞回曲线较为饱满,其整体特性主要由H型钢桩所控制。单调、循环往复加载试验中,弯矩分布形态较为相似,循环往复加载试验中最大弯矩所对应的深度,要大于单调加载试验中的对应深度,这种差别在强轴方向加载时表现的尤为明显,这主要是因为循环往复加载方式会导致更深的桩土空隙出现。强、弱轴方向加载下的桩身最大弯矩所对应的位置差别较大,由于桩土相对刚度的差异,强轴方向的最大弯矩对应深度要大于弱轴方向相应深度4倍桩截面边长左右。试验中最大土压力分布位置与最大弯矩对应位置较为一致,土压力随加载点位移的曲线变化呈现抛物线型,土体呈现高度非线性。从刚度退化曲线可以看出,对于强轴方向循环加载试验,其整体刚度最大值所对应的水平位移要大于弱轴方向加载的相应值,这主要是由于强轴循环加载会使砂土密实性更好,从而会使其峰值刚度所对应的水平位移偏大。在试验研究的基础之上,本文通过建立有限元模型来探讨砂土中H型钢桩的抗震性能。从分析结果看出,尽管API模型和Reese模型会低估桩土的抗侧刚度和极限承载力,但从整体来讲,两者都能较为合理的预测水平力—位移反应。从水平力-位移反应和桩身弯矩沿深度分布曲线可以看出,Reese模型对地基反力模量变化系数不敏感。考虑到土体的离散性,本文对API规范中推荐的p-y曲线进行了适当修正。修正后的有限元模型能很好的预测桩土侧向刚度和极限承载力,同时运用修正后的有限元模型进行了一系列的参数化分析。通过砂土摩擦角、桩头距离地面高度、桩头嵌固形态(自由或固结)、以及轴压比的变化,探讨了其对水平受荷H型钢桩性能的影响。最后,本文从桩土相互作用的基本方程出发,引入不同轴压比下的H型钢桩截面弯矩-曲率关系公式,求解得到不同轴压比下的水平受荷H型钢桩的反应,给出了强、弱轴方向加载下,H型钢桩在砂土中的位移延性系数和曲率延性系数的关系,为今后土体中H型钢桩的抗震性能研究提供了理论性的参考。
[Abstract]:At present, H-shaped steel pile foundation is widely used in bridge engineering because of its relatively small cross-sectional area, strong penetration force, small disturbance to soil, easy to change the length and so on. Especially in the United States, there are thousands of bridges using H-shaped steel pile foundation. However, for some extreme cases, such as earthquake and ship collision, the H-shaped steel pile foundation will undergo very large horizontal deformation, and the influence of horizontal force on pile foundation is very important. It is necessary to study the related static performance of H-shaped steel single piles under horizontal loads. Based on the above, the seismic performance test and theoretical research of H-shaped steel piles are carried out in this paper. Firstly, the experimental research of horizontal loaded piles over the past sixty years is summarized and classified in detail for the future. At the same time, the author summarizes and classifies the analysis methods of the horizontal loaded piles, and elaborates their respective advantages and disadvantages. These theoretical analysis methods provide a comprehensive and detailed analysis basis for the future research on the characteristics of the new pile foundation under horizontal load. It also provides a comprehensive static analysis foundation for further study of pile foundation characteristics under extreme dynamic horizontal loads in the future. Then the test plan of H-shaped steel piles under horizontal loading is formulated. In the test, H-shaped steel piles are model piles with a scale of 1/3, pre-buried and compacted in sand. It is shown from the test results that H-shaped steel piles have relatively stable performance under large deformation, whether under strong or weak axial loading. The hysteretic curves of H-steel piles and soil are pinched, and the overall characteristics are mainly controlled by the soil. Under the condition of large deformation, the hysteretic curves of H-steel piles and soil are full, and the overall characteristics are mainly controlled by H-steel piles. The depth corresponding to the bending moment is greater than that corresponding to the monotonic loading test. This difference is especially evident when the pile is loaded in the direction of strong axis. This is mainly because the cyclic reciprocating loading will lead to deeper voids in the pile and soil. The maximum bending moment in the strong axis direction corresponds to about 4 times the length of the cross section of the pile in the weak axis direction. It can be seen from the chemical curve that the horizontal displacement corresponding to the maximum global stiffness is greater than that corresponding to the weak axial direction in the cyclic loading test. This is mainly due to the better compactness of the sand under the cyclic loading of the strong axial direction, which makes the horizontal displacement corresponding to the peak stiffness larger. The results show that although API model and Reese model can underestimate the lateral stiffness and ultimate bearing capacity of pile and soil, both of them can reasonably predict the horizontal force-displacement response as a whole. Depth distribution curves show that Reese model is insensitive to the variation coefficient of foundation reaction modulus. Considering the discreteness of soil, the p-y curve recommended in API code is corrected appropriately. The modified finite element model can predict the lateral stiffness and ultimate bearing capacity of pile and soil very well. At the same time, the modified finite element model is used to predict the lateral stiffness and ultimate bearing capacity of pile and soil. A series of parameterized analyses are carried out. The effects of sand friction angle, pile head height from the ground, pile head embedding form (free or consolidated), and axial compression ratio on the performance of H-shaped steel piles under horizontal loading are discussed. Finally, the bending of H-shaped steel piles under different axial compression ratios is introduced from the basic equation of pile-soil interaction. The moment-curvature relation formula is used to calculate the response of H-shaped steel piles under different axial compression ratios. The relationship between the displacement ductility coefficient and the curvature ductility coefficient of H-shaped steel piles in sandy soil under strong and weak axial loading is given, which provides a theoretical reference for the future study of seismic behavior of H-shaped steel piles in soil.
【学位授予单位】：湖南大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：U442.55
，
本文编号：2185315
[Abstract]:At present, H-shaped steel pile foundation is widely used in bridge engineering because of its relatively small cross-sectional area, strong penetration force, small disturbance to soil, easy to change the length and so on. Especially in the United States, there are thousands of bridges using H-shaped steel pile foundation. However, for some extreme cases, such as earthquake and ship collision, the H-shaped steel pile foundation will undergo very large horizontal deformation, and the influence of horizontal force on pile foundation is very important. It is necessary to study the related static performance of H-shaped steel single piles under horizontal loads. Based on the above, the seismic performance test and theoretical research of H-shaped steel piles are carried out in this paper. Firstly, the experimental research of horizontal loaded piles over the past sixty years is summarized and classified in detail for the future. At the same time, the author summarizes and classifies the analysis methods of the horizontal loaded piles, and elaborates their respective advantages and disadvantages. These theoretical analysis methods provide a comprehensive and detailed analysis basis for the future research on the characteristics of the new pile foundation under horizontal load. It also provides a comprehensive static analysis foundation for further study of pile foundation characteristics under extreme dynamic horizontal loads in the future. Then the test plan of H-shaped steel piles under horizontal loading is formulated. In the test, H-shaped steel piles are model piles with a scale of 1/3, pre-buried and compacted in sand. It is shown from the test results that H-shaped steel piles have relatively stable performance under large deformation, whether under strong or weak axial loading. The hysteretic curves of H-steel piles and soil are pinched, and the overall characteristics are mainly controlled by the soil. Under the condition of large deformation, the hysteretic curves of H-steel piles and soil are full, and the overall characteristics are mainly controlled by H-steel piles. The depth corresponding to the bending moment is greater than that corresponding to the monotonic loading test. This difference is especially evident when the pile is loaded in the direction of strong axis. This is mainly because the cyclic reciprocating loading will lead to deeper voids in the pile and soil. The maximum bending moment in the strong axis direction corresponds to about 4 times the length of the cross section of the pile in the weak axis direction. It can be seen from the chemical curve that the horizontal displacement corresponding to the maximum global stiffness is greater than that corresponding to the weak axial direction in the cyclic loading test. This is mainly due to the better compactness of the sand under the cyclic loading of the strong axial direction, which makes the horizontal displacement corresponding to the peak stiffness larger. The results show that although API model and Reese model can underestimate the lateral stiffness and ultimate bearing capacity of pile and soil, both of them can reasonably predict the horizontal force-displacement response as a whole. Depth distribution curves show that Reese model is insensitive to the variation coefficient of foundation reaction modulus. Considering the discreteness of soil, the p-y curve recommended in API code is corrected appropriately. The modified finite element model can predict the lateral stiffness and ultimate bearing capacity of pile and soil very well. At the same time, the modified finite element model is used to predict the lateral stiffness and ultimate bearing capacity of pile and soil. A series of parameterized analyses are carried out. The effects of sand friction angle, pile head height from the ground, pile head embedding form (free or consolidated), and axial compression ratio on the performance of H-shaped steel piles under horizontal loading are discussed. Finally, the bending of H-shaped steel piles under different axial compression ratios is introduced from the basic equation of pile-soil interaction. The moment-curvature relation formula is used to calculate the response of H-shaped steel piles under different axial compression ratios. The relationship between the displacement ductility coefficient and the curvature ductility coefficient of H-shaped steel piles in sandy soil under strong and weak axial loading is given, which provides a theoretical reference for the future study of seismic behavior of H-shaped steel piles in soil.
【学位授予单位】：湖南大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：U442.55
，
本文编号：2185315
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