考虑土—桩—结构相互作用的PHC管桩地震响应研究

发布时间：2018-01-25 19:27

本文关键词： PHC管桩土-桩-上部结构动力相互作用振动台试验地震响应傅立叶谱有限元分析液化　出处：《武汉大学》2013年博士论文　论文类型：学位论文

【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。
[Abstract]:PHC pipe pile is a high - strength concrete pre - stressed pipe pile , because its hollow cross section is obviously weaker than the entity pile type of equal size in terms of rigidity and shear strength , the seismic capacity of PHC pipe pile is too weak . Therefore , the research on seismic response of PHC pipe pile is very necessary . Therefore , it is necessary to study the application of PHC pipe pile in high intensity area . In view of this subject , the research work of PHC pipe pile seismic response considering soil - pile - superstructure interaction is carried out . ( 1 ) adopting the technical scheme that the vibration table model test is main and the numerical calculation of the finite element is auxiliary , and the two are mutually authenticated , and the main work is as follows : 1 . Based on a large number of domestic and foreign literatures , this paper summarizes and analyzes the theoretical research , calculation method and experimental progress of pile foundation seismic response considering soil - pile - superstructure interaction . 2 . The design realizes the vibration table test of the interaction system of PHC pipe pile - soil - upper structure . The layered shear deformation soil box is selected as the soil taking container ; the foundation soil has three layers of clay , silt and sand ; the pile body model has three kinds of clay , silt and sandy soil ; the pile body model has three kinds of single pile , three piles and six piles , and the upper structure of the six pile model increases the different weights twice ; 3 . The three - dimensional finite element calculation model of PHC pipe pile - soil - upper structure interaction system is established by using the large - scale software of software , and the dynamic calculation analysis is carried out . ( 2 ) The vibration table model test data is comprehensively collated and analyzed , and compared and verified with the finite element calculation results . The following conclusions are mainly obtained : 1 . The strain of the single pile and the three pile models is the maximum of the pile top , and is rapidly attenuated along the pile body , the strain of the single pile is attenuated by about 80 % -90 % at the pile diameter of about 6 times from the top of the pile , the strain of the pile is attenuated by 55 % -75 % , and then the pile bottom is gradually attenuated downwards . 2 . Under the action of weak earthquake , the strain of the six pile model is maximum at the top of the pile , and the strain is attenuated by 35 % -50 % along the pile top down about 6 times the pile diameter . As the strength of the pile increases , the strain of each mutation point increases rapidly , which gradually exceeds the pile top , especially the pile top down about 11 times the pile diameter . 3 . With the increase of the number of piles , the dynamic response gradually decreases , the strain and bending moment of the pile body gradually decrease , the difference between the maximum value and the minimum value of the pile body decreases by 10 % -50 % and 40 % -80 % respectively , the maximum bending moment peak value decreases by 30 % -55 % and 70 % -80 % , the maximum pressure of the pile - soil interface decreases by about 20 % -70 % and 30 % -80 % , respectively , and the lateral maximum displacement of the upper structure is reduced by about 6 % -25 % and 15 % -40 % respectively . 4 . The distribution law of strain peak at both sides of the pile body of single pile , three pile and six pile model is not symmetrical , especially the difference of the strain distribution law on both sides of the pile body of the six pile model . 5 . As the vibration continues , the self - vibration frequency of the soil decreases and the damping increases . As the magnitude of the vibration increases , the interaction between the soil - pile - structure is strengthened , the non - linear nature of the soil is enhanced , but the nonlinear property of the soil between the piles is weaker than that of the pile - side soil , and the nonlinear property of the soil - side soil is weaker than that of the far - pile soil ; and the vibration damage phenomenon of the multi - pile system is far weaker than that of the less - pile system . 6 . The weight of the upper structure gradually increases the response of the structure system , the strain and bending moment of the pile body and the distribution law and the magnitude of the transverse displacement of the structure are not one - way , but have complex interaction . 7 . Under the saturated condition of the soil , the vibration causes liquefaction of the sand layer , the nonlinear property of the liquefaction soil is enhanced , the capacity of the transmission vibration is weakened , the distribution of the pile body is more linear , the strain and the bending moment peak of the pile body are generally increased along the distribution of the pile body , the contact pressure is greatly reduced along the liquefaction soil layer and the pile soil boundary , and the transverse displacement of the structure is slightly reduced , and the transverse displacement of the structure is generally increased . 8 . The rationality of the calculation model and the reliability of the vibration table test result are verified by comparing the results of the vibration table model test with the finite element calculation results . 9 . It is feasible to preliminarily determine the high intensity of PHC pipe pile in 8 - degree fortification intensity , and it is worth further study .

【学位授予单位】：武汉大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：TU473.1

【参考文献】