桩与土非线性耦合扭转振动特性分析
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摘要
在Novak边界层模型基础上,将桩周土分为非线性粘弹性内域和线弹性外域,采用随内域平均应变减小的等效剪切模量和增长的等效材料阻尼比近似考虑桩周土的非线性,并采用等效线性法对桩与土层耦合扭转振动进行了研究,得到了考虑桩-土动力相互作用的单桩桩顶扭转角及其扭转动力阻抗函数,然后通过算例对桩-土体系进行了扭转振动特性的参数分析。结果表明:桩顶激振扭转荷载的频率和幅值、外域土与桩的剪切波速比、内域土非线性范围以及桩长径比等因素对非线性土中单桩扭转动刚度和阻尼具有较大影响,所得结论为进一步研究桩-土-桥梁结构非线性动力相互作用机理提供了理论基础。
Based on the boundary model presented by Novak,the soil around the single pile was divided into two regions: the inner zone on nonlinear viscoelastic field and the outer zone on linear viscoelastic region.The soil nonlinearity can be considered approximately by using a reduced equivalent shear modulus and an increased equivalent material damping ratio with decrease of the average strain in the inner zone.By means of equivalent linearization method,torsional angle and torsional dynamic impedance function of single pile head with consideration of pile-soil interaction were deduced from studying pile-soil coupling torsional vibration.Parameters of dynamic behaviors of pile-soil system under torsional vibration were analyzed through an example.Results show that torsional dynamic stiffness and damping of single pile embedded in nonlinear soil depend on the frequency and amplitude of dynamic load on the pile head,shear wave velocity ratio of pile and outer soil,inner nonlinear soil area and slenderness ratio of the pile.It provides theoretical foundation for mechanism of pile-soil-bridge structure nonlinear dynamic interaction.
Based on the boundary model presented by Novak,the soil around the single pile was divided into two regions: the inner zone on nonlinear viscoelastic field and the outer zone on linear viscoelastic region.The soil nonlinearity can be considered approximately by using a reduced equivalent shear modulus and an increased equivalent material damping ratio with decrease of the average strain in the inner zone.By means of equivalent linearization method,torsional angle and torsional dynamic impedance function of single pile head with consideration of pile-soil interaction were deduced from studying pile-soil coupling torsional vibration.Parameters of dynamic behaviors of pile-soil system under torsional vibration were analyzed through an example.Results show that torsional dynamic stiffness and damping of single pile embedded in nonlinear soil depend on the frequency and amplitude of dynamic load on the pile head,shear wave velocity ratio of pile and outer soil,inner nonlinear soil area and slenderness ratio of the pile.It provides theoretical foundation for mechanism of pile-soil-bridge structure nonlinear dynamic interaction.
引文
[1]NOVAK M,SHETA M.Approximate Approach toContact Effects of Piles[C]//ASCE.Dynamic Re-sponse of Structures:Experimentation,Observation,Pre-diction and Control.New York:ASCE,1980:53-79.
[2]VELETSOS A S,DOTSON K W.Impedances of SoilLayer with Disturbed Boundary Zone[J].Journal ofGeotechnical Engineering,1986,112(3):363-368.
[3]HAN Y C,SABIN G C W.Impedances for RadiallyInhomogeneous Viscoelastic Soil Media[J].Journal ofEngineering Mechanics,1995,121(9):939-947.
[4]NOVAK M,HOWELL J F.Torsional Vibration ofPile Foundations[J].Journal of the Geotechnical En-gineering,1977,103(4):271-285.
[5]刘宗贤.单桩基础在层土中的扭转振动分析[J].世界地震工程,1993(1):37-42.LIU Zong-xian.The Torsional Vibration Analysis forthe Single Pile Foundation in Layer Foundation[J].World Earthquake Engineering,1993(1):37-42.
[6]刘东甲,周安,刘煜洲.有限长完整桩中的扭转波[J].应用力学学报,2005,22(2):258-262.LIU Dong-jia,ZHOU An,LIU Yu-zhou.TorsionalWave in Finite Length Intact Pile[J].Chinese Journalof Applied Mechanics,2005,22(2):258-262.
[7]胡昌斌,张涛.桩与粘性阻尼土耦合扭转振动时域响应研究[J].振动工程学报,2006,19(3):404-410.HU Chang-bin,ZHANG Tao.Time Domain Tor-sional Response of Dynamically Loaded Pile in Vis-cous Damping Soil Layer[J].Journal of VibrationEngineering,2006,19(3):404-410.
[8]NOVAK M,SACHS K.Torsional and Coupled Vi-brations of Embedded Footings[J].EarthquakeEngineering&Structural Dynamics,1973,2(1):11-33.
[9]HARDIN B O,DRNEVICH V P.Shear Modulus andDamping in Soils:Design Equations and Curves[J].Journal of the Soil Mechanics and Foundations,1972,98(7):667-692.
[10]任慧.场地动力反应的理论分析与场地土动力特性试验研究[D].长沙:湖南大学,2005.REN Hui.Theoretic Analysis of Dynamic Site Re-sponse and Experimental Study of Cyclic Soil Behav-ior[D].Changsha:Hunan University,2005.
[11]冯忠居,冯瑞玲,赵占厂,等.黄土湿陷性对桥梁桩基承载力的影响[J].交通运输工程学报,2005,5(3):60-63.FENG Zhong-ju,FENG Rui-ling,ZHAO Zhan-chang,et al.Effect of Collapsible Loess on Pile Foun-dation Bearing Capacity[J].Journal of Traffic andTransportation Engineering,2005,5(3):60-63.
[12]方磊,谢永利.柔性基础下复合地基桩土应力比模型试验[J].长安大学学报:自然科学版,2005,25(2):30-32.FANG Lei,XIE Yong-li.Model Experiment of Pile-soil Stress Ratio of Composite Ground Under FlexibleFoundation[J].Journal of Chang an University:Nat-ural Science Edition,2005,25(2):30-32.
[2]VELETSOS A S,DOTSON K W.Impedances of SoilLayer with Disturbed Boundary Zone[J].Journal ofGeotechnical Engineering,1986,112(3):363-368.
[3]HAN Y C,SABIN G C W.Impedances for RadiallyInhomogeneous Viscoelastic Soil Media[J].Journal ofEngineering Mechanics,1995,121(9):939-947.
[4]NOVAK M,HOWELL J F.Torsional Vibration ofPile Foundations[J].Journal of the Geotechnical En-gineering,1977,103(4):271-285.
[5]刘宗贤.单桩基础在层土中的扭转振动分析[J].世界地震工程,1993(1):37-42.LIU Zong-xian.The Torsional Vibration Analysis forthe Single Pile Foundation in Layer Foundation[J].World Earthquake Engineering,1993(1):37-42.
[6]刘东甲,周安,刘煜洲.有限长完整桩中的扭转波[J].应用力学学报,2005,22(2):258-262.LIU Dong-jia,ZHOU An,LIU Yu-zhou.TorsionalWave in Finite Length Intact Pile[J].Chinese Journalof Applied Mechanics,2005,22(2):258-262.
[7]胡昌斌,张涛.桩与粘性阻尼土耦合扭转振动时域响应研究[J].振动工程学报,2006,19(3):404-410.HU Chang-bin,ZHANG Tao.Time Domain Tor-sional Response of Dynamically Loaded Pile in Vis-cous Damping Soil Layer[J].Journal of VibrationEngineering,2006,19(3):404-410.
[8]NOVAK M,SACHS K.Torsional and Coupled Vi-brations of Embedded Footings[J].EarthquakeEngineering&Structural Dynamics,1973,2(1):11-33.
[9]HARDIN B O,DRNEVICH V P.Shear Modulus andDamping in Soils:Design Equations and Curves[J].Journal of the Soil Mechanics and Foundations,1972,98(7):667-692.
[10]任慧.场地动力反应的理论分析与场地土动力特性试验研究[D].长沙:湖南大学,2005.REN Hui.Theoretic Analysis of Dynamic Site Re-sponse and Experimental Study of Cyclic Soil Behav-ior[D].Changsha:Hunan University,2005.
[11]冯忠居,冯瑞玲,赵占厂,等.黄土湿陷性对桥梁桩基承载力的影响[J].交通运输工程学报,2005,5(3):60-63.FENG Zhong-ju,FENG Rui-ling,ZHAO Zhan-chang,et al.Effect of Collapsible Loess on Pile Foun-dation Bearing Capacity[J].Journal of Traffic andTransportation Engineering,2005,5(3):60-63.
[12]方磊,谢永利.柔性基础下复合地基桩土应力比模型试验[J].长安大学学报:自然科学版,2005,25(2):30-32.FANG Lei,XIE Yong-li.Model Experiment of Pile-soil Stress Ratio of Composite Ground Under FlexibleFoundation[J].Journal of Chang an University:Nat-ural Science Edition,2005,25(2):30-32.
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