立式储液罐橡胶基底隔震模型实验研究

针对立式储液罐地震响应问题,引伸土木结构控制思想,建立了立式储液罐橡胶基底隔震体系的试验模型,进行了地震动试验,试验结果表明,隔震体系对减轻短周期的地震影响是有效的,但对长周期的地震影响是无效的。     

夹层橡胶支座参数对大型LNG储罐地震响应的影响

利用ADINA软件建立董家口16万立方米LNG储罐的有限元模型,在模型中分别设置不同水平刚度、不同隔震频率和阻尼比的夹层橡胶垫作为储罐的隔震装置。对比了隔震前后储罐的位移和加速度反应的变化,同时分析了采用不同隔震参数支座的储罐在液固耦合作用下,储罐内部液面晃动的变化情况。结果表明:夹层橡胶支座的水平刚度对储罐隔震效果的作用不明显,但夹层橡胶支座的隔震频率和阻尼比对储罐隔震效果的影响显著。隔震频率和阻尼比越大,对内外罐位移和加速度的控制效果越明显。因为基底剪力、基底倾覆弯矩和动液压力会增大,而且隔震装置会放大储罐的晃动波高,所以在选取隔震支座时,要综合考虑储罐高径比、隔震支座的隔震频率和阻尼比等参数,选取最优组合,从而达到最佳的减震效果。     

非线性隔震立式浮顶储罐双向地震作用分析

研究浮顶振动对立式储罐地震响应的影响时,假定浮顶运动为均质刚性圆板振动,其波高沿半径方向线性变化,建立了含有波高参量的运动方程、基底剪力和倾覆力矩表达式.同时,在Park恢复力模型的基础上,给出了铅芯橡胶支座的双向耦合恢复力计算模型,并用该模型模拟了铅芯橡胶支座的力-变形非线性行为.采用时程分析方法对双向地震作用下的浮顶储罐地震响应进行分析,并与未考虑浮顶作用以及单向地震作用的储罐地震响应进行对比.数值结果表明,考虑浮顶作用具有降低地震响应的效果;特定工况下,地震响应峰值可能出现在非主震方向.     

地震资料约束下大地电磁资料反演

应用地震资料约束下大地电磁资料反演古潜山或基底内部结构的新方法. 首先利用地震及井资料,反演得到古潜山或基底之上各层的厚度及电阻率,建立了古潜山或基底以上的地电模型;并利用大地电磁一维反演资料,建立了古潜山或基底及其以下的地电模型. 在初始模型建立的基础上,应用高效快速的二维大地电磁正演算法——模式匹配方法,进行正演计算. 利用共扼梯度迭代方法,进行正反演迭代计算. 通过对胜利油田南北618剖面反演, 基底以下在地震资料没有显示的构造信息,在反演结果中得到了较好地反映.      

橡胶砂垫层在不同类别场地上的减震效应研究

橡胶砂(RSM)垫层减震是一种适用于低层房屋的低成本减震方法,关于场地类别对其减震效应影响的研究尚未开展。采用简化的层间剪切模型模拟减震垫层-上部结构动力相互作用体系,建立了RSM垫层"减震地基"分析模型。针对30%配比的橡胶砂,考虑3种垫层厚度200 mm/300 mm/500 mm、4种基底压力50 kPa～300 kPa,基于对取自于不同场地类别的195条地震波的刚性地基反应谱和RSM垫层"减震地基"反应谱的分析对比,得到以下结论:(1)RSM垫层的减震效应受场地类别的影响,场地卓越周期越短,减震效应越好;(2)RSM垫层厚度越大,减震效应越好,但当垫层厚度达到500 mm时,减震性能鲁棒性变差,且这种鲁棒性的劣化与场地类别无关;(3)各种场地类别地震波作用下,RSM垫层减震效应均随输入地震加速度和基底应力的增大而增加,但随着前者的增加,后者的影响减小。     

装有铅橡胶复合阻尼器结构的减震研究

本文在普通铅芯橡胶垫的基础上,提出了一种新型阻尼器－铅橡胶复合阻尼器,并介绍了其构造与工作原理,建立了铅橡胶复合阻尼器结构的分析模型,并对铅橡胶复合阻尼器的减震效果进行了初步分析。结果表明,铅橡胶复合阻尼器具有很好的减震效果具有广阔的应用前景。     

近场地震下立式隔震储罐试验研究及理论分析

针对近场地震激励下隔震储罐响应的问题,采用简化后的三质点力学模型,分别对铅芯橡胶支座隔震储罐模型在近、远场地震作用下的响应进行了对比分析,并将理论分析结果和振动台试验结果进行了对比。对比结果显示,理论分析得出的加速度响应与振动台试验结果相近,但理论分析结果会略微偏小。进一步的理论分析结果表明:近场地震下基础隔震能有效降低储罐的基底剪力和基底弯矩,而晃动波高有所增大;隔震后储罐加速度峰值位于液固耦合质点附近。     

SMA-叠层橡胶复合隔震支座耗能能力的影响因素研究

为研究SMA丝-叠层橡胶支座和SMA绞线-叠层橡胶支座力学性能,基于AuricchioSacco本构模型分析形状记忆合金材料的超弹性特性,采用有限元方法分别建立这两种橡胶支座模型,在此基础上以位移幅值和竖向荷载作为主要影响因素,数值模拟分析得出两种橡胶支座的恢复力-位移滞回曲线,建立了位移和荷载变量对支座的等效水平刚度、等效阻尼比和单位循环耗能的关系,进而分析两种橡胶支座的性能差异,为该支座的工程设计和使用提供理论依据。     

恢复力—摩擦基底隔震结构的地震可靠性分析

本文建立了恢复力-摩擦基底隔震结构在地震作用下的运动微分方程。地震地面运动被模拟成随机过程。利用等效线性化方法,获得了这种基底隔震结构在地震作用下的均方位移和均方速度反应。根据最大位侈反应的概率分布函数,求得了这种基底隔震结构和与它相应的基底固定结构在给定地震作用下的破坏概率。计算结果表明,这种基底隔震结构在地震作用下有较高的可靠性。     

基底隔震储罐频率特征与减震机理分析研究

研究不同高径比橡胶基底隔震储罐的频率特征,探讨储罐隔震体系3种不同振动频率随支座隔震频率变化规律.分析在不同频谱特性地震波激励下,隔震体系各振型组分对地震响应(基底剪力、支座位移和晃动波高)的影响,以及响应峰值随支座隔震频率和阻尼比的变化特点.研究表明,基底剪力峰值与场地地震波频谱特性密切相关.支座隔震频率不能完全反映减震机理的实质,隔震振型频率是影响基底剪力的重要参数.在软弱场地上隔震储罐的减震效率低,有效隔震频率范围窄.晃动波高峰值是储罐自振特性和地震波频谱特性等多种因素导致的结果,隔震系统设计时需特别考虑晃动波高增大的影响.     

Assessing the digital filter method for base flow estimation in glacier melt dominated basins

Base flow is an important component of streamflow. Although the simple digital filter method is widely used for base flow separation, the applicability in alpine rivers mainly dominated by glacier melt has not been described in detail. To assess and improve the performance of base flow estimates using the filter method for catchments dominated by glacier melt, the enhanced Soil Water Assessment Tool (SWAT) is used to obtain the estimates of streamflow and base flow for three catchments with different glacier melt contribution in arid and cold Northwestern China. The digital filter is then applied to the simulated streamflow to separate base flow and assess how well the base flow by the filter method matches these obtained using the SWAT model. In order to obtain the best match between the base flow by the filter method and those using the SWAT model, the linear regression model is used to estimate the relation between the filtered base flow and the glacier melt. It was found that the filtered base flow was matched well with base flow using the SWAT model during the low‐flow period. However, the base flow based on the digital filter method was overestimated during the high‐flow period, especially for the Manas River and Kumarik River. The base flow indexes by the digital filter estimates were 2.9%, 33.3% and 100% larger than those of the model method for the Gongnaisi River, Manas River and Kumarik River, respectively. The differences are larger with bigger glacier melt contribution. The performance of the digital filter is affected by the glacier melt, and it can be improved significantly by the combination of filtered base flow and the glacier melt. The base flow indexes by the improved filter are 1.5%, 4.4% and 10.7% larger than those of the model method for the Gongnaisi River, Manas River and Kumarik River, respectively. Copyright © 2015 John Wiley & Sons, Ltd.     

Initiation of motion of a free‐standing body to base excitation

This study is concerned with the conditions for the initiation of various modes of response of a free‐standing rigid body, initially at rest, placed on a frictional horizontal base which undergoes earthquake‐like accelerations in both the horizontal and vertical directions. These conditions are derived using equations of motion appropriate for each mode of motion. The analysis shows that an equivalent horizontal base acceleration may be constructed by dividing the time history of horizontal base acceleration by the sum of gravitational acceleration and the time history of vertical base acceleration. The criteria governing each mode of response of a body of given aspect ratio are then presented graphically with the magnitude of the equivalent base acceleration as abscissa and the coefficient of friction between the body and the base as ordinate. The study shows that a body is more stable while the vertical base acceleration is upwards than when it is absent as expected. When the vertical base acceleration is downwards, although the body is very likely to be lifted off the base, it is nevertheless possible to rock, and slide and rock simultaneously provided the value of coefficient of friction is sufficiently high and the downward vertical base acceleration is not too different from gravitational acceleration. Copyright © 2007 John Wiley & Sons, Ltd.     

滚动FPS和MR阻尼器混合基础动力学模型及仿真

本文中作者将新型双磙子FPS系统的动力学方程推广到由滚动FPS和MR阻尼器组成的混合隔震基础系统,得到了更便于应用的水平分量形式的运动微分方程,并将与FPS有关的力和MR阻尼力处理成力源项,构造了可以方便地考虑不同上部结构形式的MATLAB/SIMULINK仿真模型。采用RD-1005型MR阻尼器和模糊逻辑控制器,在两个典型的地震输入情况下对混合系统进行了振动控制仿真。仿真结果表明,本文建立的混合隔震基础系统的动力学模型是正确和精确的,直接利用动力学模型进行前向计算可避免附加的模型误差且计算效率高,而仿真模型中将不同的力源由分开的块组成,使得仿真设计非常方便快捷。     

四川宜宾6.0级地震对北斗地基增强基准站稳定性的短期影响

通过收集2019年6月17日宜宾长宁6.0级地震震源附近北斗地基增强系统基准站前后一个月的观测数据,研究探讨短时间内地震对北斗地基增强基准站坐标稳定性的影响。通过数据对比发现宜宾地震对基准站坐标影响与基准站和震源断裂带的相对方位有较大关联。震源周围基准站间基线的变化说明基准站稳定性在较短时间跨度内受到较为明显的地震影响,对北斗地基增强框架网整体稳定性具有一定的扰动,进一步论证了建立北斗地基增强框架网基准站稳定性监控系统的必要性。     

动力相互作用分析中无质量地基的应用研究

关于结构-地基的动力相互作用分析已经提出了很多方法，但由于方法复杂而没有得到广泛应用，无质量地基模型仍然是应用最为广泛的近似方法。本文通过结构-地基的动力相互作用分析公式的推导，详细阐明了考虑无限地基影响的动力相互作用分析中无质量地基的概念和应用范围，并通过算例进行了说明。     

Criteria for initiation of motion of rigid bodies to base excitation

It is known that when an unanchored rigid body is placed on a horizontal base which oscillates horizontally, it may undergo one of four modes of motion: rest, slide, slide–rock and rock. Initiation of a rigid body into these modes depends on the slenderness ratio of the body, the coefficient of friction between the body and the base and the acceleration of the base. In this study, the coefficient of friction and the base acceleration are considered random. For specific probability distributions of the coefficient of friction and the peak base acceleration, and for various values of the mean and standard deviation of the two random variables, the probabilities of occurrence of these modes of motion are obtained for a body of given slenderness ratio. It is shown that randomness of the coefficient of friction and base peak acceleration should not be ignored. Copyright © 2005 John Wiley & Sons, Ltd.     

A Least-Squares Standard Deviation Method to Interpret Gravity Data due to Finite Vertical Cylinders and Sheets

We have developed a least-squares approach to determine simultaneously the depth to both the top and base of a buried finite vertical cylinder (vertical line element approximation) and a 2-D vertical thin sheet from moving average residual anomaly profiles obtained from gravity data using filters of successive window lengths. The method involves using a relationship between the depth to the top, and base of the source and a combination of windowed observations. The method is based on computing the standard deviation of the depths to the top, determined from all moving average residual anomalies for each value of the depth to the base. The standard deviation may generally be considered a criterion for determining the correct depth to the top and base of the buried structure. When the correct depth to the base value is used, the standard deviation of the depths to the top is less than the standard deviation using incorrect values of the depth to the base. This method can be applied to residuals as well as to the observed gravity data. The method is applied to synthetic examples with and without random errors and tested on two field examples from the USA and Canada.     

Base uplifting analysis of flexibly supported liquid-storage tanks

An approximate method is presented for the analysis of earthquake induced uplifting in base plates of unanchored liquid-storage tanks that are supported directly on flexible soil foundations. The method takes due account of the non-linearities arising from the continuous variation of base contact area, membrane action and plastic yielding in the base plate. First, an ‘exact’ solution is presented for a uniformly loaded flexibly supported prismatic beam, uplifted by a concentrated force applied at one end. A series of such beams are later used in an approximate model of the base plate. The method is highly efficient and believed to be accurate for the level of uplifts encountered in practice. The results are presented for a range of foundation stiffness, representing loose sandy soils to rigid concrete mat. It is shown that, for the same overturning base moment, the flexibly supported tanks, in comparison with the rigidly supported tanks, experience significantly smaller axial compressive stress, but larger base uplift, foundation penetration, plastic rotation at plate boundary and hoop compressive stress in the tank wall.     

Optimal instrumentation of structures on flexible base for system identification

A criterion previously developed by Heredia-Zavoni and Esteva for selecting optimal sensor locations is used to analyse the optimal instrumentation of structures on soft soils. The stochastic response of a linear structural system on a flexible base is formulated for use of the criterion. The case of MDOF shear systems on flexible base, with uncertain lateral stiffness and subjected to random earthquake ground motions, is studied. The optimal location of accelerometers, the reduction of prior uncertainty on the lateral stiffness, the effects of the base flexibility, the relative influence of translation and rocking of the base, and the influence of recording noise are assessed and discussed. Copyright © 1999 John Wiley & Sons, Ltd.     

Second‐mode tuned mass dampers in base‐isolated structures for reduction of floor acceleration

To reduce floor acceleration of base‐isolated structures under earthquakes, a tuned mass damper (TMD) system installed on the roof is studied. The optimal tuning parameters of the TMD are analyzed for linear base isolation under a generalized ground motion, and the performance of the TMD is validated using a suite of recorded ground motions. The simulation shows that a TMD tuned to the second mode of a base‐isolated structure reduces roof acceleration more effectively than a TMD tuned to the first mode. The reduction ratio, defined as the maximum roof acceleration with the TMD relative to that without the TMD, is approximately 0.9 with the second‐mode TMD. The higher effectiveness of the second‐mode TMD relative to the first‐mode TMD is attributed primarily to the unique characteristics of base isolation, ie, the relatively long first‐mode period and high base damping. The modal acceleration of the second mode is close to or even higher than that of the first mode in base‐isolated structures. The larger TMD mass ratio and lower modal damping ratio of the second‐mode TMD compared to the first‐mode TMD increases its effect on modal acceleration reduction. The reduction ratio with the second‐mode TMD improves to 0.8 for bilinear base isolation. Because of the detuning effect caused by the change in the first‐mode period in bilinear isolation, the first‐mode TMD is ineffective in reducing roof acceleration. Additionally, the displacement experienced by the second‐mode TMD is considerably smaller than that of the first‐mode TMD, thereby reducing the installation space for the TMD.