共查询到19条相似文献，搜索用时 718 毫秒
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理论计算及实测资料表明,反射波法基桩动测激振信号近似为半周期正弦波,不同激振方式产生的桩顶速度脉冲信号宽度不同,相应频率成分也就不同。桩身内阻尼对不同频率谐波的幅值衰减及频散规律不同,使得不同激振方式产生的复合脉冲在同一桩中会有不同变化规律,为了使不同激振方式测试资料具有可比性,应采用相同频带进行对比。为此利用小波分析的时-频特性,通过对测试信号进行时频分解,就桩身内阻尼对不同频带信号的吸收系数及波速的影响规律进行了研究。对实测资料分析的结果表明,预制桩不同频带信号波速变化不大,但衰减系数随频率增大近似线性增加。 相似文献
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建立现浇X形桩(XCC桩)桩-土体系三维有限元模型,对XCC桩低应变检测动力响应进行数值模拟,得到完整桩和缺陷桩的桩顶速度响应结果,并分析完整桩及缺陷XCC桩桩顶速度响应特性及规律。计算结果表明:XCC桩低应变瞬态动测时桩顶速度响应存在明显的三维效应,桩心(激振点)附近点的入射波峰值较大,且到达时间较早;距离桩心越远点的入射波峰到达时间越滞后,入射波峰值从桩心到尖角边界先减小后增大。桩顶距桩心距离相同的环向上各点的入射波和反射波区别不大,而各点所受的高频干扰情况并不相同。变模量桩的入射波和完整桩相同,反射波峰值较完整桩小,反射波峰对应时间较完整桩滞后。局部缺陷桩桩顶距桩心距离相同环向各点的第一个缺陷反射波有微小差别,而第二个缺陷反射波有较大差别。 相似文献
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低应变反射波法在桩基完整性检测技术中愈来愈占有重要的地位,但简便易行的优点也造成了检测结果精确性的不足,本文结合反射波法在实践中的应用,就球面波、人为造成波阻抗变化在检测中的影响等几方面和读者进行探讨。 相似文献
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液化土体中桩基侧向动力响应一直是目前岩土工程界和地震工程领域关注的热点研究问题之一.本文基于振动台实验,首次将光纤布拉格光栅(FBG)技术应用到液化土体桩基侧向动力响应分析方法中.实验结果表明:采用FBG传感系统可以测得桩身侧向动力响应,与传统电阻式应变片法相比简洁方便;FBG测量土体位移同样有效可行,可代替以往加速度积分求解土体位移;后处理得到的桩基侧向动力p-y滞回曲线能更好地反映桩土之间真实的动力本构关系,并与干砂动力p-y曲线相比,探讨两种不同场地条件下桩基侧向动力响应机制与p-y曲线的发展变化模式,为以后液化土中桩基侧向动力响应问题的研究奠定了理论基础. 相似文献
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中日规范中关于液化和侧向扩流场地桥梁桩基抗震设计考虑之比较 总被引：1，自引：0，他引：1
评述了我国液化场地和侧向扩流场地桥梁桩基抗震设计规范。总结了中日两国液化场地和侧向扩流场地桥梁桩基的抗震设计方法与技术细节,阐述了日本规范中液化场地和侧向扩流场地桥梁桩基抗震设计中的液化地基土反力折减系数的确定方法,以及土体液化侧向扩流对桩作用力的计算模式。指出我国规范中在液化和侧向扩流场地桩的抗震分析方法、不同土层分界处桩的抗震措施、桩的竖向承载力及桩的屈曲稳定性分析等方面存在的主要问题,据此给出了亟待改进的初步建议。这对我国桥梁工程的抗震安全性具有重要意义,可供我国工程技术人员参考借鉴。 相似文献
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This paper presents theoretical analysis of the parallel seismic (PS) method for evaluating existing piles using the flexural mode wave exited by a horizontal impact on the lateral surface of a pile. A simplified theoretical model of the flexural wave for PS method was established to elaborate the theoretical basis. A correction factor was then obtained and proposed to correct the pile depth obtained from the PS method, thus providing a more accurate estimation. A three dimension (3-D) finite element (FE) model was developed and the existence of the flexural waves on branch F(1, 1) in the pile shaft has been verified. Two time domain methods were used to calculate the flexural wave velocity in the pile. One was based on the pile tip reflection signal using a model where pile head reflection was minimized, and another method used the slope of the upper fitted line in the PS test. The flexural wave velocities from both methods match well with the predicted flexural wave group velocity determined from the dispersion curve of a 1-D rod embedded in the soil. The accuracy in estimation of pile tip depth is improved by applying the correction factor. A series of parametric studies were carried out to demonstrate the effectiveness of using flexural wave for PS test and the correction factor proposed in this study. 相似文献
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Based on the theory of tube wave propagation in a fluid-filled borehole, this paper proposes a new method for detecting the integrity of pile foundation and overcomes some limitations of the existing pile integrity tests. The basic principle of detecting the pile integrity by the tube wave, testing equipment and concrete quality evaluation of piles are introduced. The feasibility of the tube wave detection for geological exploration of a bridge pile in a karst development area is verified by field tests. Through some test cases of prestressed high strength concrete pipe piles, cast-in-place piles and rock-socketed piles with defects, the accuracy of the tube wave detection and other methods is compared. Then, some issues of the application of the tube wave for detecting pile defects are discussed. Finally, the content of this paper is summarized, and some suggestions on further research are put forward. 相似文献
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弹性波反射法在桩基检测中的理论与应用 总被引：1，自引：0，他引：1
根据波动理论探讨了弹性波在砼桩中的传播衰减规律及反射特征，提出了判断桩基质量的有关理论依据，并结合工程实例应用弹性波反射法讨论了时域、频域分析法的基本原理及存在问题． 相似文献
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Robb Eric S. Moss Joseph A. Caliendo Loren R. Anderson 《Soil Dynamics and Earthquake Engineering》1998,17(7-8):519-523
In certain regions of the world, designing deep foundations to withstand seismic loading is a reality. Seismic loading of structures and foundations reaches its most critical state as a cyclic lateral force. The response of soils and foundations to repetitive lateral forces is highly complex, relegating most design methods to be based upon overly conservative rules-of-thumb. The primary objective of this research was to analyze the mechanics of seismic loading on pile groups in clay soils. To achieve this a model testing facility was constructed to house a fully instrumented 1×5 model pile group that was subjected to cyclic lateral loading. An empirically based method for pile group design is suggested based upon the results generated from model pile group testing. 相似文献
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根据Ｗｉｎｋｌｅｒ地基模型，对桩基础通过特性分析建立了合理的力学模型。在动力分析的基础上，给出了桩基础横向自振特性及在常轴力与横向地震载荷作用下的强迫反应解析解。文中的解析公式为桩基础动力分析提供了一种新的解析方法。 相似文献
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通过进行大型模型槽足尺模型试验,根据桩身变形和柱身弯矩的试验结果,分析了水平荷载作用下现浇混凝土大直径管桩（以下简称PCC桩）的水平承栽特性和桩-土共同作用性状。采用大型通用有限元软件ABAQUS对PCC桩的水平承载特性进行了数值模拟,计算结果与试验结果符合得较好,并进一步探讨了PCC桩水平承载特性的主要影响因素。结果表明：表层土体的弹性模量对水平受力性状影响较大,表层土体的厚度对桩身水平位移也有较大影响,因此可以通过改良表层土体来控制桩身水平位移,以达到工程设计要求;土体强度参数对水平承载特性也有影响,尤其是内摩擦角和粘聚力较小时更为明显。 相似文献
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无损检测技术在桩基检测等方面应用广泛,但如果桩体存在多层缺陷,采用常规测试手段评价桩体质量往往有一定的局限性,难以满足工程的特殊需要.采用跨孔电磁层析技术对桩基础进行检测,是一种新的尝试.文中结合工程实例比较了这一新的检测方法与低应变桩基动力检测结果以说明其效果. 相似文献
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Modern seismic design codes stipulate that the response analysis should be conducted by considering the complete structural system including superstructure, foundation, and ground. However, for the development of seismic response analysis method for a complete structural system, it is first imperative to clarify the behavior of the soil and piles during earthquakes. In this study, full‐scale monotonic and reversed cyclic lateral loading tests were carried out on concrete piles embedded into the ground. The test piles were hollow, precast, prestressed concrete piles with an outer diameter of 300 mm and a thickness of 60 mm. The test piles were 26 m long. Three‐dimensional (3D) finite element analysis was then performed to study the behavior of the experimental specimens analytically. The study revealed that the lateral load‐carrying capacity of the piles degrades when subjected to cyclic loading compared with monotonic loading. The effect of the use of an interface element between the soil and pile surface in the analysis was also investigated. With proper consideration of the constitutive models of soil and pile, an interface element between the pile surface and the soil, and the degradation of soil stiffness under cyclic loading, a 3D analysis was found to simulate well the actual behavior of pile and soil. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献