地基阻尼比测试的一种计算方法
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摘要
基于规范[1-2],对某动力基础阻尼比进行了测试及计算。数值处理结果表明,在自由振动和强迫激励作用下,阻尼比测试数值与弹性半空间近似公式及规范推荐近似公式的结果存在较大差别。为此提出了利用基础表面若干测点的3向振动时程合成基础质心6自由度时程,并以该时程曲线作为地基动力参数的测试依据。在此基础上,建议相关规范应推荐在某些重要基础建造时,在基础底面适当位置预埋传感器,以基础底面振动测试数据作为地基阻尼比等动力参数的计算依据更为准确。
Damping ratio testing method of a foundation was studied theoretically and experimentally based on the corresponding Chinese measurement and design codes.It is shown that there is a relatively large difference between numerical results of codes and approximate formulae based on elastic half-space analytical solution.Therefore,six-degree-freedom time histories of the center of mass center of a foundation are calculated from three-component vibration curves of some points on the foundation surface to be selected as the analytical time-history of some dynamic parameters such as compressive stiffness,rotational stiffness,shearing stiffness,torsional stiffness,damping ratio and mass of vibration of subsoil.It is recommended that the vibration sensors should be pre-embedded in some proper positions of the foundation bottom surface to improve the precision of subsoil dynamic parameters measurement.
Damping ratio testing method of a foundation was studied theoretically and experimentally based on the corresponding Chinese measurement and design codes.It is shown that there is a relatively large difference between numerical results of codes and approximate formulae based on elastic half-space analytical solution.Therefore,six-degree-freedom time histories of the center of mass center of a foundation are calculated from three-component vibration curves of some points on the foundation surface to be selected as the analytical time-history of some dynamic parameters such as compressive stiffness,rotational stiffness,shearing stiffness,torsional stiffness,damping ratio and mass of vibration of subsoil.It is recommended that the vibration sensors should be pre-embedded in some proper positions of the foundation bottom surface to improve the precision of subsoil dynamic parameters measurement.
引文
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[2]中华人民共和国机械工业部.GB/T50269-97地基动力特性测试规范[S].北京:中国计划出版社,1999.
[3]王锡康.动力机器基础振动学科在我国的发展及需研究的若干问题[J].工业建筑,2007,37(6):83-90.WANG Xi-kang.Development of discipline for vibration of machinery foundation in China and some problems being studied[J].Industrial Construction,2007,37(6):83-90.
[4]RICHARD F E,WHITMAN R V.Comparison of footing vibration tests with theory[J].Journal of the Soil Mechanics and Foundations Division,ASCE,1967,93(6):143-168.
[5]李小军,廖振鹏,张克绪.考虑阻尼拟合的动态骨架曲线函数式[J].地震工程与工程振动,1994,14(1):30-35.LI Xiao-jun,LIAO Zhen-peng,ZHANG Ke-xu.A functional formula of dynamic skeleton curve taking account of damping effect[J].Earthquake Engineering and Engineering Vibration,1994,14(1):30-35.
[6]陈学良,金星,陶夏新,等.考虑试验阻尼效应的一种土体动力双型抛物线本构模型[J].岩土力学,2008,29(8):2102-2110.CHEN Xue-liang,JIN Xing,TAO Xia-xin,et al.A soil dynamic double-parabola constitutive model considering effect of soil test damping[J].Rock and Soil Mechanics,2008,29(8):2102-2110.
[7]尚守平,熊伟,杜运兴,等.饱和场地土动力特性试验研究[J].岩土力学,2008,29(1):23-27.SHANG Shou-ping,XIONG Wei,DU Yun-xing,et al.Experimental study on dynamic characteristics of saturated soils[J].Rock and Soil Mechanics,2008,29(1):23-27.
[8]庄海洋,刘雪珠,陈国兴.互层土的动参数试验研究及其地震反应分析[J].岩土力学,2005,26(9):1495-1498.ZHUANG Hai-yang,LIU Xue-zhu,CHEN Guo-xing.A study on dynamic parameters and seismic response of interbedded soil[J].Rock and Soil Mechanics,2008,26(9):1495-1498.
[9]韩英才.大型动力基础的设计研究[J].建筑结构学报,1986,6(5):61-69.HAN Ying-cai.Study on large dynamic foundation design[J].Journal of Building Structures,1986,6(5):61-69.
[10]王振宇,刘晶波,裴欲晓,等.大型动力机器基础防微振计算理论与实测研究[J].岩土工程学报,2002,24(3):363-366.WANG Zhen-yu,LIU Jing-bo,PEI Yu-xiao,et al.Theoretical and experimental study on micro-vibration reduction of large dynamic machine foundation[J].Chinese Journal of Geotechnical Engineering,2002,24(3):363-366.
[11]陈炯.动力基础的竖向振动分析[J].土木工程学报,2002,35(4):70-76.CHEN Jiong.The vertical vibration of dynamically loaded foundation[J].China Civil Engineering Journal,2002,35(4):70-76.
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