隔震立式储罐地震反应谱分析

基于反应谱理论,研究了的基底隔震储罐的地震响应问题.将储罐简化为三质点体系力学模型,罐内连续液体质量等效为对流质量、脉冲质量和刚性质量,并引入隔震刚度.与时程分析对比,验证反应谱法的适用性,分析隔震立式储罐的地震响应并研究主要参数对隔震储液罐地震响应的影响,主要考虑的参数有:(1)场地类别;(2)隔震周期;(3)高径比.结果表明:反应谱法计算隔震立式储罐地震响应是偏于安全的;随着场地类别和隔震周期的增大,基底剪力减震率逐渐降低,晃动波高变化不明显,隔震后,液动压力呈线性变化,液动压力随着场地类别和高径比的增大而增大,随着隔震周期的增大而减小;高径比存在一定的优化段,在优化段内,基底剪力减震率较大,隔震效果较好.     

基于概率-非概率混合可靠性模型的结构地震易损性分析

在易损性分析中,存在对结构阈值的不确定性研究较少,对阈值的选择通常为规范中的数值,得到的破坏概率仅为固定数值等问题,文中同时考虑结构响应和阈值不确定性,建立一种基于概率-非概率混合模型的结构地震易损性分析方法.基于Opensees建立桥梁有限元模型,选择最大支座纵向位移、最大桥墩柱弯曲延性作为衡量结构性能的工程需求参数...     

大连地区地震活动性分析及地震概率背景估计

根据统计计算大连地区１９９１年１１月至 １９９９年１月发生的２９９个ＭL≥２．０地震,得出目前该地区的地震活动规律,并对这期间的地震变化趋势进行了理论分析和概率背景估计,认为其间所发生的地震属于１９９３年３月１８日的大连满家滩南海ＭＬ４．３地震序列,从理论值和实测值的结果判断,该地震序列发生 ＭＬ≥５．０的可能性不大, 但不能排除该地震序列仍然存在着发生４．０≤ＭＬ＜５．０地震的概率背景．目前的地震平静期属于该地震序列活动期的尾声和下一地震活动期能量积累的初级阶段．     

基于地震易损性的框架结构的优化方法

给出了一种框架结构地震易损性优化的准则算法．根据优化准则构造了一种修改设计变量的格式,提出了设计方案可行性调整的方法并推导了计算公式,给出了优化算法的计算步骤,并通过一个算例阐述了这种算法的应用。     

立式钢制储罐隔震抗震设计的工程化方法

针对立式钢制圆柱储罐隔震抗震设计的工程化方法进行了研究,提出了一种利用规范化设计用反应谱法进行隔震抗震设计的思想。     

液压阻尼系统（HDS）控制立式钢制储罐地震响应分析

本文采用液压阻尼系统（HDS）控制立式圆柱钢制储罐的地震反应，建立了安装HDS储罐的力学分析模型，并进行了数值计算，从频域对安装HDS后储罐的地震响应进行了分析，研究了HDS的减震效果和HDS和HDS参数对储罐地震反应的影响。     

基于能量方法设计的RC框架结构易损性分析

基于“强柱弱梁”的屈服机制,依据能量平衡方法设计了某6层RC框架结构,采用震级-震中距条带地震动记录选取方法,选取12条随机地震动,利用Perform-3D有限元分析软件对结构进行增量动力（IDA）分析,得到了结构的地震易损性曲线、破坏状态概率曲线以及结构破坏概率矩阵。分析结果表明:该方法设计的结构能够形成预设的“强柱弱梁”屈服机制,可以保证结构中梁充分参与耗能,同时结构具有较强的抗倒塌能力,可以满足“小震不坏,中震可修,大震不倒”的性能要求。     

地震易损性分析方法研究综述

结构的地震易损性分析对于预测结构的抗震性能、进行结构的抗震设计、加固和维修决策具有重要的应用价值。本文将对近几十年来地震易损性评估方法领域内的重大发展做全面综述,并对易损性分析方法的类别和优缺点及其应用作了总结和讨论。     

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.     

立式钢制储罐基于地震损伤性能的抗震设计方法

针对立式钢制储罐在强烈地震作用下会产生不同程度的损伤的特点，遵循抗震设计规范的“小震不坏，中震可修，大震不倒”的抗震设计原则，结合三水准烈度，提出了储罐的地震损伤性能目标，并给出了基于地震损伤性能的抗震设计方法。所提出抗震设计方法，更加准确地考虑了储罐的提离问题。     

Response of tanks to vertical seismic excitations

A method for analyzing the earthquake response of elastic, cylindrical liquid storage tanks under vertical excitations is presented. The method is based on superposition of the free axisymmetrical vibrational modes obtained numerically by the finite element method. The validity of these modes has been checked analytically and the formulation of the load vector has been confirmed by a static analysis. Two forms of ground excitations have been used: step functions and recorded seismic components. The radial and axial displacements are computed and the corresponding stresses are presented. Both fixed and partly fixed tanks are considered to evaluate the effect of base fixation on tank behaviour. Finally, tank response under the simultaneous action of both vertical and lateral excitations is calculated to evaluate the relative importance of the vertical component of ground acceleration on the overall seismic behaviour of liquid storage tanks.     

A simplified seismic analysis of rigid base liquid storage tanks under vertical exicitation with soil-structure interaction

A study is carried out to evaluate dynamic response of an elastic circular cylindrical tank having a rigid base under a vertical excitation taking into consideration the interaction with the foundation soil. At first, the soil is represented by frequency-independent parameters. Two coupled differential equations, governing the motion of the shell and the base, are solved using a step by step integration technique. The hydrodynamic pressures, acting on the shell and on the base, are derived from a velocity potential function which satisfies the Laplace equation and the appropriate boundary conditions. The response of the simplified model of a tank having a rigid base on a stiff foundation soil is compated to that obtained elsewhere to check the accuracy of the present model. Reasonable agreement is found between the maximum wall displacement and the associated stresses with those found by a more elaborate model. The interaction of the tank and the soil reduces the response than that calculated under the assumption of a rigid foundation soil. A parametric study to examine the effects of the height-to-radius ratio of the tank, and the effects of the shear wave velocity of the soil on the response is conducted. Varieties of foundation models are used to assess the sensitivity of the response to the variation in the soil parameters. Finally, a more representative solution for the problem in the frequency domain is obtained where the soil is appropriately modelled by frequency-dependent parameters. The transfer functions of the response of the tank wall and of the relative base motion are evaluated, and a comparison between the frequency-dependent and the frequency-independent solutions is made.     

Assessing the seismic torsional vulnerability of elevated tanks with RC frame-type staging

Recurrence of torsional failure of elevated water tanks in past earthquakes (including 1952 Kern County and recent 1993 Killari earthquakes) has highlighted the importance of this problem. It is established that these structures may have amplified torsion-induced rotation if their torsional-to-lateral natural period ratio τ is close to 1 and amplified displacement of structural elements due to the coupled lateral-torsional vibration if τ is within the critical range 0.7<τ<1.25. The present study aims to estimate the range of variation of τ for usually constructed reinforced concrete elevated water tanks with frame-type stagings for assessing their torsional vulnerability. Closed-form expressions for torsional and lateral stiffness of tank stagings are derived and verified by standard finite element software. These expressions are used for studying the variation of τ for feasible ranges of influencing parameters. It is seen that a very large number of such tanks may have τ within the said critical range. Closed-form expressions for moments and shear forces of columns and beams under torsion and that under lateral force are also derived. It is also seen with the help of these expressions that the frame stagings of these tanks normally designed for seismic lateral force, may yield through formation of plastic hinges simultaneously in all columns instead of in beams if they are subjected to large rotational response for having τ possibly very close to 1. Such a pattern of yielding generally converts the whole system suddenly into a mechanism causing immediate collapse. Therefore, torsional coupling seems to be a potential cause of failure for these structures.     

基于概率密度演化的隔震结构随机地震响应

本文考虑地震动的随机性,运用概率密度演化方法对基础隔震结构的随机响应进行研究.上部结构与隔震层分别采用刚度退化的Bouc-Wen模型与Bouc-Wen模型,建立隔震结构的概率密度演化方程,直接应用四阶龙格-库塔方法迭代求解隔震结构的非线性的响应,得出隔震结构在8度罕遇地震下每层的位移概率.结果显示隔震结构较非隔震结构上部结构的位移大大地减小了,上部结构具有足够的安全性.结构整个概率密度演化过程显示了隔震结构的响应信息,概率密度演化方法能够有效评估隔震结构的抗震性能.     

基于推覆分析的RC框架地震倒塌易损性预测

基于倒塌率的结构倒塌易损性分析是目前评价结构抗倒塌能力最合理的方法.但是,目前基于增量动力分析(IDA)的倒塌率分析方法,工作量和实施难度大,很难直接用于工程设计,因此有必要研究便于工程应用的新方法.本文基于18个典型多层RC框架结构的IDA倒塌率分析和静力推覆分析,发现RC框架在大震下的倒塌率及抗倒塌安全储备(CMR)与静力推覆得到的结构位移安全储备之间存在较好的相关关系.依据此关系,建议了保证大震倒塌率的推覆位移安全储备,并通过9个RC框架结构算例进行了验证.本文方法简单易行,可供规则多层RC框架结构抗倒塌设计参考.     

立式储油罐地震作用下的抗提离可靠度分析

储油罐在水平地震作用下会出现罐底提离而导致储油罐发生提离破坏,影响储油罐的可靠性。为了研究立式储油罐在地震作用下的抗提离可靠度情况,文中总结建立了在储油罐抗提离可靠度分析中涉及的随机变量的概率模型,运用可靠性分析的JC法对不同工况下的储油罐进行了抗提离可靠度计算,得出了储油罐在地震作用下的提离破坏规律。通过计算实例可以看出,对大型储油罐在地震作用下的抗提离可靠度分析是切实可行的。     

大型立式浮顶储罐基础隔震数值研究

强震作用下,立式浮顶储罐破坏严重。为了降低浮顶储罐的地震响应,选取15×104m3大型立式浮顶储罐,引入基础隔震措施,并考虑浮顶的影响,应用势流体理论,采用ADINA建立有限元模型。研究在不同隔震层阻尼比、不同隔震周期、不同烈度及不同场地条件影响下,基础隔震浮顶储罐的地震响应并进行对比分析。结果表明:当隔震层阻尼比为0.2～0.3时减震效果较好,阻尼比存在合理优化区间;随着隔震周期、地震烈度的增加,基础隔震浮顶储罐的减震率增加;基础隔震浮顶储罐的减震效应受场地条件影响较大;基础隔震措施不能有效控制浮顶储罐的晃动波高。浮顶储罐隔震设计时需要综合考虑多种因素,选取最佳隔震设计参数。     

中美欧储罐抗震规范中地震作用的比较研究

对比分析了中国、美国和欧州国家储罐抗震设计规范在抗震设防基准、设防目标、设计参数、储罐简化模型、设计反应谱和地震力降低系数等方面的不同特点,比较各规范设计地震作用的大小.研究表明:我国鉴定标准、美国API650和欧洲EC-8的抗震设防水准基本相当,而欧洲EC-8的抗震设防目标偏低.对于中等类型场地上的低自振周期储罐,我国鉴定标准设计地震作用与美国API650相当,但低于欧洲EC-8设计值,鉴定标准的晃动波高大于欧洲EC-8.另外以我国常用系列浮顶罐和大型浮顶罐为研究对象,比较储罐频率、液体等效质量、晃动波高等参数的不同.研究得到一些结论和建议,对修订我国储罐抗震设计规范有借鉴意义.     

Finite locally resonant Metafoundations for the seismic protection of fuel storage tanks

This paper introduces a novel seismic isolation system based on metamaterial concepts for the reduction of ground motion-induced vibrations in fuel storage tanks. In recent years, the advance of seismic metamaterials has led to various new concepts for the attenuation of seismic waves. Of particular interest for the present work is the concept of locally resonant materials, which are able to attenuate seismic waves at wavelengths much greater than the dimensions of their unit cells. Based on this concept, we propose a finite locally resonant Metafoundation, the so-called Metafoundation, which is able to shield fuel storage tanks from earthquakes. To crystallize the ideas, the Metafoundation is designed according to the Italian standards with conservatism and optimized under the consideration of its interaction with both superstructure and ground. To accomplish this, we developed two optimization procedures that are able to compute the response of the coupled foundation-tank system subjected to site-specific ground motion spectra. They are carried out in the frequency domain, and both the optimal damping and the frequency parameters of the Metafoundation-embedded resonators are evaluated. As case studies for the superstructure, we consider one slender and one broad tank characterized by different geometries and eigenproperties. Furthermore, the expected site-specific ground motion is taken into account with filtered Gaussian white noise processes modeled with a modified Kanai-Tajimi filter. Both the effectiveness of the optimization procedures and the resulting systems are evaluated through time history analyses with two sets of natural accelerograms corresponding to operating basis and safe shutdown earthquakes, respectively.