土-箱形基础-框架结构相互作用的顶部小幅激振试验研究
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摘要
设计并完成了野外大比例(1∶2)土-箱形基础-框架结构相互作用系统顶部小幅激振试验。通过改变上部结构质量和基础侧限埋深,激振试验得到了同一基础不同上部结构质量与同一上部结构不同基础侧限埋深等5种工况下相互作用对系统自振频率及箱形基础阻抗函数的影响。由试验结果分析可知,当上部结构质量增加时,上部结构与土体间的相对刚度降低,相互作用对系统自振频率的影响减弱;同时由于上部结构和基础间惯性相互作用的影响,基础阻抗函数随上部结构质量的增加而增加。随着基础侧限埋深的减小,基础刚度降低,相互作用体现得更加明显。与理论结果相比,无侧限埋深基础的平动和转动基础阻抗值和理论值吻合较好。由于基础侧边回填土剪切模量小于基础底部土体剪切模量,所以同理论值相比试验得到的基础侧限埋深对基础阻抗影响系数相对较小。
Small amplitude forced vibration tests(FVT) for a field large-scale soil-box foundation-structure interaction system were designed and carried out.By changing the mass of superstructure and foundation embedment,FVT included five cases: the different superstructure's weights with the same foundation embedment and the same superstructure's weight with different foundation embedment.The effects of interaction on the system modal frequencies and foundation impedances were tested.When the structure mass is increased,the relative stiffness of soil to structure is decreased and the effect of interaction on system modal frequencies is weakened.Due to the effect of kinematic interaction,the foundation impedance values are increased with the increase of superstructure weight.With the decrease of foundation embedment,the foundation stiffness is decreased,and the interaction become more evidently.Compared to theoretical values,the translatory and rocking impedances for the unembedded case are found to be in agreement with the values obtained from analytical formulation.Because the shear modulus of backfilled soil is less than that of the supporting soil,the experimentally obtained embedment factors are much little than that predicted by theory.
Small amplitude forced vibration tests(FVT) for a field large-scale soil-box foundation-structure interaction system were designed and carried out.By changing the mass of superstructure and foundation embedment,FVT included five cases: the different superstructure's weights with the same foundation embedment and the same superstructure's weight with different foundation embedment.The effects of interaction on the system modal frequencies and foundation impedances were tested.When the structure mass is increased,the relative stiffness of soil to structure is decreased and the effect of interaction on system modal frequencies is weakened.Due to the effect of kinematic interaction,the foundation impedance values are increased with the increase of superstructure weight.With the decrease of foundation embedment,the foundation stiffness is decreased,and the interaction become more evidently.Compared to theoretical values,the translatory and rocking impedances for the unembedded case are found to be in agreement with the values obtained from analytical formulation.Because the shear modulus of backfilled soil is less than that of the supporting soil,the experimentally obtained embedment factors are much little than that predicted by theory.
引文
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[2]陈国兴,王志华,等.土与结构动力相互作用体系振动台模型试验研究[J].世界地震工程,2002,18(4):47~54.
[3]尚守平,朱志辉,等.土-箱形基础-结构动力相互作用的模态试验分析[J].湖南大学学报,2004,5:66~73.
[4]Francisco C P,D e Barros,Luco J E.Identification of foundation impedance functions and soil properties from vibration tests of the Hualien con-tainm entmodel[J].Journal of Soil Dynam ics and Earthquake Engineering,1995,14:229~248.
[5]L in A lbertN,Jenn ings P C.E ffect of embedm ent on foundation-soil impedances[J].Journal of Engineering M echan ic,1984,110(7):1060~1075.
[6]W ong H L,Trifunac M D,Luco J E.A comparison of soil-structure interaction calcu lations w ith resu lts of fu ll-scale forced vibration tests[J].Journal of Soil Dynam ics and Earthquake Engineering,1988,7(1):22~31.
[7]W ong H L,Luco J E.Tabels of impedance functions for square foundations on layered m ed ia[J].Journal of SoilDynam ics and Earthquake Engi-neering,1985,4(2):64~81.
[8]M ita A,Luco E.Impedance functions and input motions for embedded square foundations[J].Journal of Geotechn ical Engineering D ivision,1989,115(4):491~503.
[9]W olf J P,Somain i D R.Approximate dynam ic model of embedded foundation in tim e domain[J].Earthquake Engineering and Structure Dynam-ic,1986,14:683~703.
[10]Luco J E,Trifunac M D,W ong H L.Isolation of soil-structure interaction effects by fu ll-scale forced vibration tests[J].Earthquake Engineeringand Structure Dynam ics,1988,16:1~21.
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