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高地震烈度软土预应力管桩(PHC)桩基础的抗震特性研究

The Seismic Study of Property of Prestressed Pipe Pile (PHC) Foundations in High Seismic Intensity Area

【作者】 李光明

【导师】 刘春原;

【作者基本信息】 河北工业大学 , 结构工程, 2013, 博士

【摘要】 针对高地震烈度、软土强度等影响预应力混凝土管桩(PHC)抗震性能的技术难题,展开结构性能试验、振动台试验、现场试验、理论分析及仿真模拟硏究,在桩身弯矩变化规律、桩土变形机理、抗震稳定性与变形控制方法、压弯破坏特性与质量检测等方面取得了突破。为预应力混凝土管桩(PHC)抗震性能的经济合理设计、施工提供了科学依据,为在高地震烈度区(场地类别为Ⅲ、Ⅳ类)预应力混凝土管桩(PHC)基础的安全使用提供了有力保障。本文主要:1.证明了在水平力荷载作用正常使用状态下预应力混凝土管桩(PHC)的破坏形态是压弯破坏,而不是剪切破坏,预应力混凝土管桩(PHC)的抗剪破坏滞后于弯曲破坏。2.确定了在各工况中预应力混凝土管桩(PHC)桩身弯矩最大值的产生位置约为距离桩顶5~6倍的桩径,反推原型(PHC500-AB100)发现,在El-centro地震波作用下,桩身在El-0.2g波时尚未发生危险截面的破坏,但是到El-0.3g、El-0.4g时桩身最大弯矩值都超过了规范中规定的极限弯矩值,该危险截面直接决定了桩身是否处于正常工作状态,此处是预应力混凝土管桩在抗震设计时的危险截面。3.建立并验证了预应力混凝土管桩(PHC)时程分析的数值模型,仿真计算表明最大弯矩值出现在5倍的桩径处,已造成预应力混凝土管桩(PHC)的开裂,其值已经接近或超过预应力混凝土管桩(PHC)的极限弯矩值。4.在高地震烈度软土地基中软弱夹层的存在会增大地表位移,使桩土相对位移增加;管桩在软弱土体中的运动表现为剪切型特性,土体越软,桩体的水平相对位移越大。5.为了保证预应力混凝土管桩(PHC)在高地震烈度(场地类别为Ⅲ、Ⅳ类)的安全与稳定,首次提出了竖向承载力设计抗弯强度校核的设计原则;硏究发现通过抗弯强度校核的管桩基础抗震设计,可以排除地震风险隐患,这个原则推广应用后大大提高建筑物的安全性。

【Abstract】 Aiming at high seismic intensity, the strength of soft soil influence the seismicbehavior of prestressed concrete pipe pile (PHC) technical problems, a structureperformance test, shaking table test, field test, theoretical analysis and simulation studywere developed, and got breakthrough in bending moment variation law of pile, pile soildeformation mechanism, seismic stability, deformation control method, the bendingfailure characteristics and quality detection. The study provides a scientific basis for theeconomic and reasonable design and construction of seismic behavior of prestressedconcrete pipe pile (PHC), and provides a powerful guarantee for the safe use ofprestressed concrete pipe pile (PHC) in high seismic intensity area (site category Ⅲ, Ⅳclass).The paper follows:1. It’s the first time proved that under the normal use state of the horizontal forceloading, the damage form of prestressed concrete pipe pile (PHC) is bending damage,rather than the shear damage, and shear damage of prestressed concrete pipe pile (PHC)behind in bending damage.2. It’s the first time identified that maximum bending moment position of theprestressed concrete pipe pile (PHC) in the working condition is about distance of5~6times the pile diameter. Through pile head backstepping prototype (PHC500-AB100), itcan be found that under the effect of El centro-seismic wave, there is no destruction ofthe most dangerous section occurs in0.2g, but maximum bending moment value is morethan the limit bending moment value in0.3g and0.4g. The section directly determine ifthe prestressed concrete pipe pile (PHC) in normal work condition, and if the section isthe dangerous section of seismic design.3. The numerical model of time history analysis of the prestressed concrete pipepile (PHC) was established and verified. The simulation calculation showed thatmaximum bending moment occur in five times the pile diameter, and has caused theprestressed concrete pipe pile (PHC) crack, whose value is close to or exceed the limit ofthe prestressed concrete pipe pile (PHC) bending moment value;4.In the soft soil foundation of high earthquake intensity, the existence of the weakinterlayer increases the surface displacement and the pile-soil relative displacement; Pipepile’s movement in soft soil showed the shear properties, and showed that the softer thesoil is, the greater the relative displacement is.5.In order to ensure the security and stability of prestressed concrete pipe pile (PHC)in high seismic intensity(site category Ⅲ Ⅳclass), It’s the first time put forward that thedesign principles of bending strength checking of vertical bearing capacity design, which showed that through Bending strength checking of pipe pile foundation seismic design,the seismic risk hidden danger can be ruled out. If this principle applied, it will greatlyimproves the safety of the building.

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