【作者】 李曰辰；

【导师】 陈明祥；

【作者基本信息】 武汉大学 ， 岩土工程， 2013， 博士

【摘要】 PHC管桩即高强混凝土预应力管桩,由于其空心截面在刚度和抗剪强度等方面明显弱于等尺寸的实体桩型,导致其抗震能力也同样偏弱。而我国又是个多地震的国家,且高烈度地区范围很广,这制约着PHC管桩的推广应用。因此,对PHC管桩地震响应的研究,特别是对其在高烈度地区适用性的研究就显得十分必要。针对这个课题,本文开展了考虑土-桩-上部结构相互作用的PHC管桩地震响应研究工作。(一)、采用以振动台模型试验为主,有限元数值计算为辅,两者互相验证的技术路线,主要工作如下：1、在查阅大量国内外文献的基础上,对考虑土-桩-上部结构相互作用的桩基地震响应的理论研究、计算方法及试验进展等研究现状进行了一定的总结和分析。2、设计实现了PHC管桩-土-上部结构相互作用体系的振动台试验。选定了层状剪变形土箱作为乘土容器；地基土共有粘土、粉土、砂土三层；桩体模型有单桩、三桩、六桩三种,且六桩模型上部结构两次增加不同配重；输入地震波有El Centro波、Taft波和人工波三种,且每种地震波有五种大小不同的加速度峰值强度。另外,每个模型还进行了土体液化试验。3、运用大型计算软件ABAQUS建立了PHC管桩-土-上部结构相互作用体系的三维有限元计算模型,并进行动力计算分析。(二)、对振动台模型试验数据进行了综合整理与分析,并和有限元计算结果进行对比和验证。主要得到以下结论：1、单桩以及三桩模型应变均为桩顶最大,并沿桩体向下快速衰减,到距桩顶约6倍桩径处,单桩应变衰减了约80%-90%,三桩应变衰减了55%-75%,再向下继续逐步衰减直到桩底。2、六桩模型在弱震作用下应变在桩顶最大,沿桩体向下较快衰减,到桩顶向下约6倍桩径处,应变衰减了35%-50%,再向下逐步衰减直至桩底,沿桩体存在2-3处应变局部增大的突变点,随着震动强度的增大,各突变点应变快速增大,逐步超过桩顶,特别是桩顶向下约11倍桩径处增大最突出,到强震工况,该处应变成为最大。3、随着模型桩数增多,动力响应逐步减弱,桩体应变及弯矩逐步降低,应变与弯矩沿桩体分布更加线性,最大值与最小值之差逐步减小。三桩、六桩模型桩体最大拉应变峰值分别比单桩模型下降10%-50%和40%-80%,最大弯矩峰值分别下降30%-55%和70%-80%,桩-土界面最大压力分别下降约20%-70%和30%-80%,上部结构横向最大位移分别下降约6%-25%和15%～-40%。4、单桩、三桩、六桩模型各桩体两侧应变峰值分布规律并不对称,特别是六桩模型桩体两侧应变分布规律差异巨大。5、随着振动持续,土体自振频率降低,阻尼增大；随着震级增加,土-桩-结构间的相互作用影响加强,土体的非线性性质增强,但桩间土非线性性质弱于桩侧土,桩侧土体非线性性质又弱于远桩土体；多桩体系的震动破坏现象远弱于少桩体系。6、上部结构重量逐步增大对结构体系功力响应、桩体应变和弯矩大小及分布规律以及结构横向位移大小等的影响不是单向的,而是有着复杂的相互作用。7、土体饱和状态下,震动造成砂土层液化,液化土体非线性性质增强,传递振动的能力减弱,有一定的减震和隔震作用；土体液化后,桩体应变和弯矩峰值总体普遍增大,沿桩体分布更线性；在液化土层,桩土界而接触压力大幅度降低；部分弱震工况,结构横向位移稍有减小,强震工况,结构横向位移普遍增大。8、通过振动台模型试验结果与有限元计算结果的对比分析,验证了计算模型的合理性和振动台试验结果的可靠性。9、初步确定PHC管桩在8度设防高烈度地区是可行的,值得进一步研究。更多还原

【Abstract】 PHC pipe pile (Prestressed high-strength concrete pipe pile) due to its hollow sections in terms of stiffness and shear strength was significantly weaker than the same size entity pile, and its seismic capacity is also weak. China is earthquake country, there are wide high seismicity regions, and it restricts the popularization and application of PHC piles. Therefore, the study of the earthquake response of PHC pile, especially its applicability in high seismicity region is essential. In this paper, the study of earthquake response of PHC pile considering Soil-Pile-Structure interaction is presented. A. In this paper, study works include a shake table model test mainly and finite element analysis supplemented is presented.1. On the basis of access to a large number of domestic and foreign literatures, theoretical study and calculation methods and test progress of the earthquake response of pile research considering soil-pile-structure interaction is summaried and analysis.2. A PHC Pile-Soil-Structure Interaction shake table test is design and implementation. A layer shear deformation soil box container is selected used. There are three layers foundation soil:clay and silt and sand. There are three pile models:single pile and three piles and six piles, and the six piles model superstructure twice increase different counterweight. There are three input seismic waves:El Centro wave and Taft wave and artificial wave, and there are five different sizes of peak acceleration for each seismic wave. In addition, liquefaction test also carried out for each model.3. Use of large-scale finite element software ABAQUS, PHC Pile-Soil-Structure Interaction three-dimensional computational model is established, dynamic calculation and analysis is carried out. B. Shaking table model test data is comprehensive collection and analysis, and compared with finite element results, some important conclusions are obtained:1. To single-pile model and three-pile model, the maximum strain occurr in the top of pile, and down fast decay along the pile, at about6times pile diameter from the top of pile, strain of single pile reduced by80%-90%, strain of three piles reduced by55%-75%, and continue down gradually decay until the bottom of the pile.2. To six-pile model, the maximum strain occurr in the top of pile in weak earthquakes, and down fast decay along the pile, at about6times pile diameter from top of pile, strain reduced by35%-50%, and continue down gradually decay until the bottom of the pile. There are2-3strain mutation point along the pile, with the increase in vibration intensity, strain of each mutant point increases rapidly, exceed the strain in top of pile gradually. Especially the strain of point about11times pile diameter from top of pile increases the most prominent, and become the largest strain point when the conditions of strong earthquakes.3. With increase in the number of pile, model dynamic response gradually weakened, the strain and bending moment of the pile reduce gradually, distribution of strain and bending moment more linear along the pile, the maximum and minimum differential is gradually reduced. It is shown that compared to the single-pile model, the maximum tensile strains of the three-pile model and six-pile model drop by10%-50%and40%-80%respectively, whereas the maximum bending moment drop by30%-55%and70%-80%respectively, the soil-pile interface pressure reduces by20%-70%and30%-80%respectively, superstructure lateral displacement reduces by6%-25%and15%-40%respectively.4. To the single-pile and three-pile and six-pile models, the peak strain distribution on both sides of every pile is asymmetry. Especially to six-pile model, the strain distribution on both sides of pile is huge difference.5. With the vibration continued, model system natural frequency decreases, damping increases. With the increase in vibration intensity, soil-pile-structure interaction effects increase, nonlinearity effects of soil enhancement. The nonlinearity effects of soil between piles is weaker than soil beside pile, the nonlinearity effects of soil beside pile are weaker than soil far from pile. The damage behaviors for systems with more piles are less severe than those with fewer piles.6. The affect of superstructure weight gradually increased to structural system is complex interactions; include the dynamic response of structural system, the size and distribution of pile strain and bending moment, the upper structure displacement.7.With the saturation of the soil, vibration caused by the liquefaction of the sand layer, the nonlinearity effects of liquefied soil enhancement, transmitted vibration diminished capacity, and the liquefied soil lead to a certain amount of shock absorption and isolation. After soil liquefaction, strain and bending moment of the piles overall generally increases, the distribution are more linear along the pile. In liquefied soil, pile-soil interface contact pressure significantly reduced. In a amount of weak shock conditions, the lateral displacement of structure is slightly smaller, but in the rest conditions, the lateral displacement of structure generally increases.8. The results of the shaking table model test and finite element analysis is compared, and the reasonable of calculation and the reliability of shaking table test is verified.9. The results of this preliminary investigation further indicate the feasibility of exploiting PHC piles in8degree high seismicity regions. It is also suggested that more research efforts are required for extensive application of PHC piles in such areas.更多还原