爆炸地震波作用下地下结构动力响应数值分析

爆炸地震波荷载类似于天然地震波荷载，但又不完全相同。基于有效应力动力分析法，运用二维显式有限差分程序FLAC对地下结构在竖向和水平爆炸地震波荷载作用下的动力响应进行数值分析。编制了周围土体介质分析模型的程序模块并与FLAC接口。考虑了水平和竖向爆炸地震波荷载对地下结构的耦合效应，得出了一些定性的结论。     

水平地震作用下建筑顶层重力荷载能力研究

地震灾害的发生给人们的生命财产安全带来了极大的威胁,为了保障在地震发生时建筑的安全,需要时刻对试件的荷载、初始刚度、延性系数、建筑模型的竖向位移等信息进行检测,一旦重力荷载高于峰值荷载,建筑安全将不能得到保障。为分析水平地震作用下建筑的顶层重力荷载能力,首先建立用于实验的一榀三层三跨式的房屋建筑模型,检测这种模型处于重力荷载作用情况下的侧向刚度,用来了解在建筑顶层结构在处于水平地震作用情况下重力荷载对其检测刚度的影响程度。然后从模型中选取5个试件,对这些试件的材料属性、实验结果、荷载位移进行分析,再通过实验模型的重力荷载位移曲线确定建筑的峰值荷载为700 kN,即当建筑顶层的峰值荷载超过700 kN时,建筑的安全性将难以保证。     

基础隔震结构在竖向荷载作用下的内力分布特点

以一个3跨4排柱建筑为例,对非隔震结构和隔震结构在竖向荷载作用下的内力分布特点进行了对比研究,其中考虑了隔震层顶部梁板结构的荷载、刚度以及结构的梁柱刚度比等因素的影响.研究中发现,与非隔震结构相比,隔震结构一层柱子的柱端弯矩明显增大,隔震层顶部梁的梁端弯矩与其倚载成正比等规律.同时提出了基于非隔震结构的隔震结构在竖向荷载作用下内力的计算方法和“隔震影响系数”的概念.即,隔震结构的内力等于非隔震结构的内力乘以“隔震影响系数”.其中还进一步对“隔震影响系数”的影响因素进行了定量研究,得出了“隔震影响系数”的计算公式.本文所提出的计算方法与隔震结构在水平地震荷载作用下的内力计算方法思路一致,因此,该方法也进一步完善了隔震结构的设计理论.     

波浪与地震对小尺度桩柱的共同作用研究

本文以某一实际平台桩柱为例,对其进行波浪作用以及波浪与地震共同作用研究。依据我国海港水文规范JTJ213-98、DNV的环境条件和环境荷载规范以及API的相关规范[1-3],对波浪荷载的计算采取不同的简化处理方式,从而分析流体的附加质量效应和流固耦合效应在不同工况下对桩柱结构响应的影响,并分析了该影响随工作水深和波浪参数的变化规律。结果表明,两种工况下流体的附加质量效应和流固耦合效应对桩柱响应的影响趋势并不相同,当进行波浪与地震共同作用分析时,有必要考虑流体附加质量效应和流固耦合效应对结构响应的影响。     

考虑竖向地震作用的拱式廊桥的地震响应分析

本文以某大型商业拱式廊桥工程实例为依托,利用有限元软件分别建立了整桥模型和不考虑上部建筑结构的桥梁模型以及不考虑下部桥梁结构的建筑模型,并计算了各自的自振动力特性,在此基础上通过反应谱方法分析了同时考虑水平地震作用和竖向地震作用的廊桥主拱圈和上部建筑结构柱的地震响应以及不同模型计算结果的差异,以此研究桥梁结构与建筑结构的耦合作用,为廊桥的抗震设计或分析提供一定的参考依据。     

考虑轴压作用下钢板剪力墙结构边框柱稳定性研究

在钢板剪力墙结构边框柱的柔度系数ωt的推导过程中未考虑稳定理论,最小惯性矩要求仅能控制边柱平面内的稳定性,而平面外的稳定性很难得到保证,并且推导未考虑结构自重等传递的竖向荷载对框架的不利作用。本文结合等效负刚度和拉力场机制份额的概念,研究了同时考虑轴压和剪切作用下结构边框柱平面内的柱柔度限值要求。同时结合稳定等效的方法给出了钢板剪力墙结构边框柱平面内、平面外稳定性的校核方法。研究表明,当考虑框架柱承担竖向荷载时,建议框架柱轴压比控制在0.3以下,柱柔度限值小于等于2.1,框架柱平面内的稳定性可以得到保证,但平面外的稳定性要重新校核。     

大跨度钢桁架转换层结构的竖向地震反应分析

对某一带钢桁架转换层的复杂高层结构进行了有限元建模,分别采用振型分解反应谱法、时程分析法和《建筑抗震设计规范》(GB50011-2001)的设计反应谱法对大跨高位钢桁架转换层结构的竖向地震响应进行了分析.对采用振型分解反应谱法计算此类结构响应时所要选取的振型数及振型组合方法进行了探讨,并对规范采用10％的重力荷载代表值...     

框架结构水平和竖向地震耦合作用时程分析

一般情况下,地震波分量中的水平分量和竖向分量是造成框架结构破坏的重要因素。本文中以框架结构为研究对象,将空间框架结构简化为平面框架结构,基于平面杆系模型并忽略平面框架体系的水平杆件——梁的轴向变形,建立体系水平和竖向耦合振动的运动微分方程,并对结构进行了水平和竖向地震波耦合激励下的弹性动力时程计算。与体系单维输入竖向地震波之弹性动力响应进行对比后,发现耦合激励下框架边柱竖向响应变大而中柱竖向响应变小,在结构抗震设计中宜适当考虑地震的耦合影响。     

隔震层竖向刚度对高层基础隔震结构的影响

高层隔震建筑的隔震层在罕遇地震作用下会产生拉应力。本文通过对一栋20层的高层隔震结构,分别采用等拉压刚度模型和不等拉压刚度模型进行动力非线性时程分析,研究叠层橡胶隔震支座竖向刚度模型对高层基础隔震结构动力响应的影响。研究表明,超出线弹性工作范围后,竖向等拉压刚度模型将会低估隔震层的竖向位移量,低估上部结构的动力响应。     

双向地震波作用下巨子型有控结构建筑的隔震设计

为了增强巨子型有控结构建筑的动力特性,提升其稳定性,设计双向地震波作用下建筑有控结构。采用3种磁流变阻尼器(MRD)与滑移隔震混合控制结构构成单体建筑有控结构,其包括巨结构和子结构,并建立该有控结构的动力分析模型。在动力分析模型中输入水平和竖向地震,得到模型的竖向和水平滑动状态运动微分方程,依据这两个方程采用自适应模糊神经网络优化动力分析模型,构建优化模型。从优化模型出发,通过实例实验分析得出,优化设计双向地震波作用下建筑有控结构时,在其上部结构层间和隔离层各安装一个MRD,可确保优化设计后的有控结构在不同双向地震工况下的地震反应控制效果最佳,且有控结构在双向地震工况2下,结构第一层、中间三层以及顶层的加速度和位移的时程曲线走向一致,且差距微小;同时有控结构的巨结构顶层侧移响应随着子结构刚度增加而提高,动力特性没有明显的变化,子结构随着其自身刚度增加顶层侧移响应表现稳定,子结构动力特性增强。     

钢筋混凝土框架顶部钢结构加层的抗震性能分析

采用钢结构加层后,结构的整体质量、刚度、周期、阻尼比等都发生较大的变化。仅对加层部分结构进行计算分析是不安全的,应进行结构的整体分析。本文采用有限元软件ANSYS,对某4层钢筋混凝土框架结构办公楼顶部加2层纯钢框架的抗震性能进行分析,并在此基础上讨论了不同加层层数的整体框架模型、不同阻尼比ζ和有侧移及无侧移框架形式对结构整体抗震性能的影响分析。计算表明,由于加层后结构周期加长,整体框架的底层层剪力变化较小。     

日本兵库县南部地震强地震动的传播特性

依据神户海洋气象台、大阪气象台、神户港岛、神户大学、神户本山小学、尼崎及大阪福岛的强震记录，分析了强地震的走时和传播特性，指出大阪盆地的厚沉积层是造成Ｓｔ波在神户和大阪到时发生延迟的原因，由于断层在空间上的分布造成一些强震记录的波形差异。     

Numerical study of Ashiyahama residential building damage in the Kobe Earthquake

Studies are made on the structural damage at the Ashiyahama residential high‐rise steel building complex due to the Hyogo‐ken Nanbu Earthquake (Kobe Earthquake), which occurred on 17 January 1995. The axial breakage of very thick‐plated steel columns of the mega‐structure is unprecedented and has been attracting the special attention of structural engineers. The cause of the damage is first investigated from numerical computation with recourse to an explicit method of dynamic analysis based on a continuous medium. The numerical result is compared with that obtained from a conventional multi‐mass lumped stiffness model combined with an equivalent lateral‐force procedure. By comparing both the numerical results, the latter conventional method is shown to be inadequate for achieving earthquake‐resistant capability. The destructive power of the ground motion is found to have exceeded the horizontal earthquake‐resistant capacity that is prescribed in the structural design criteria. Great axial stresses are produced in columns by combined action of bending moment and axial force due to overturning moment. The fracture of heavy steel columns is caused from only the horizontal component of seismic ground motion. Actual locations of significant damage are closely related to the occurrence of plastic hinges in the analysis. It is emphasized as a warning to avoid yielding concentration in particular storeys. Lastly, recommendations to enhance earthquake‐resistant design are proposed from a practical point of view. Copyright © 2001 John Wiley & Sons, Ltd.     

On the coupled torsional and sway vibrations of a class of shear buildings

This paper is concerned with the free vibrations of a restricted class of multi-storey shear buildings in which inertial coupling exists between the torsional and the two sway vibrations. The restrictions imposed are that (a) the shear centres of all storeys lie on a vertical straight line, (b) the principal axes of shear are in the same directions in all storeys, (c) the centres of mass of all floors lie on another vertical straight line, (d) the radius of gyration about the shear centre of every floor mass is the same and (e) the ratios of the two shear stiffnesses to the torsional stiffness do not vary from storey to storey. In consequence of the last restriction it is proved that the 3n natural frequencies, normal modes and generalized masses, where n is the number of storeys, are expressible very simply in terms of products of the three natural frequencies, normal modes and generalized masses of the single-storey, three-dimensional building formed by removing everything above the first floor, with the n natural frequencies, normal modes and generalized masses of a certain n-storey, two-dimensional shear frame. In the special case of a uniform building, a simple closed form solution, valid for any number of storeys, is given.     

Collapse assessment of moment frame buildings,considering vertical ground shaking

While many cases of structural damage in past earthquakes have been attributed to strong vertical ground shaking, our understanding of vertical seismic load effects and their influence on collapse mechanisms of buildings is limited. This study quantifies ground motion parameters that are capable of predicting trends in building collapse because of vertical shaking, identifies the types of buildings that are most likely affected by strong vertical ground motions, and investigates the relationship between element level responses and structural collapse under multi‐directional shaking. To do so, two sets of incremental dynamic analyses (IDA) are run on five nonlinear building models of varying height, geometry, and design era. The first IDA is run using the horizontal component alone; the second IDA applies the vertical and horizontal motions simultaneously. When ground motion parameters are considered independently, acceleration‐based measures of the vertical shaking best predict trends in building collapse associated with vertical shaking. When multiple parameters are considered, Housner intensity (SI), computed as a ratio between vertical and horizontal components of a record (SI_V/SI_H), predicts the significance of vertical shaking for collapse. The building with extensive structural cantilevered members is the most influenced by vertical ground shaking, but all frame structures (with either flexural and shear critical columns) are impacted. In addition, the load effect from vertical ground motions is found to be significantly larger than the nominal value used in US building design. Copyright © 2016 John Wiley & Sons, Ltd.     

STC加筋砂水平循环剪切与竖向激振特性试验研究

随着中国汽车工业的发展,大量废旧轮胎带来的"黑色污染"问题日益显著。提出一种采用废旧轮胎柱(Scrap tire columns,STC)的加筋土结构,并初步探究其作为基础减隔振材料的可行性。通过室内水平循环剪切试验和竖向激振试验研究STC加筋砂(STCRS)的水平循环剪切和竖向激振特性。结果表明,最大剪应变为1%时STCRS的等效阻尼比未加筋前增加约10%,等效动剪切模量减小20%~25%,水平向减振性能得以提高;STCRS的竖向加速度衰减呈现出速度快、幅值大的特点,竖向减振效果较未加筋砂显著提高。STC加筋砂作为基础减振材料是可行的,且为原形废旧轮胎的资源化利用提供新思路。     

Effects of near-fault ground motions on the nonlinear behaviour of reinforced concrete framed buildings

The design provisions of current seismic codes are generally not very accurate for assessing effects of near-fault ground motions on reinforced concrete(r.c.)spatial frames,because only far-fault ground motions are considered in the seismic codes.Strong near-fault earthquakes are characterized by long-duration(horizontal)pulses and high values of the ratio α_(PGA)of the peak value of the vertical acceleration,PGA_V,to the analogous value of the horizontal acceleration,PGA_H,which can become critical for girders and columns.In this work,six- and twelve-storey r.c.spatial frames are designed according to the provisions of the Italian seismic code,considering the horizontal seismic loads acting(besides the gravity loads)alone or in combination with the vertical ones.The nonlinear seismic analysis of the test structures is performed using a step-by-step procedure based on a two-parameter implicit integration scheme and an initial stress-like iterative procedure.A lumped plasticity model based on the Haar-Karman principle is adopted to model the inelastic behaviour of the frame members.For the numerical investigation,five near-fault ground motions with high values of the acceleration ratio α_(PGA) are considered.Moreover,following recent seismological studies,which allow the extraction of the largest(horizontal) pulse from a near-fault ground motion,five pulse-type(horizontal)ground motions are selected by comparing the original ground motion with the residual motion after the pulse has been extracted.The results of the nonlinear dynamic analysis carried out on the test structures highlighted that horizontal and vertical components of near-fault ground motions may require additional consideration in the seismic codes.     

底层带支撑异型柱框架非线性地震反应分析

本文利用ＤＲＡＩＮ－２Ｄ程序对底层带支撑异型柱框架进行了时程分析，并且与无支撑异型柱框架及通高设支撑异型柱框架进行了比较分析，结果表明，笔者提出的底层带支撑异型柱框架是一种良好的结构形式。     

NUMBER OF MODES FOR THE SEISMIC DESIGN OF BUILDINGS

The effect of higher modes on the maximum response of buildings subjected to one horizontal component of earthquake ground motion is discussed with the objective of developing better design formulas for use in building design. Ideal buildings of different numbers of storeys and structural systems are defined; their dynamic properties that define higher mode contribution are identified and are shown to be representative of real buildings. Design formulas that give the required number of modes to be used in a dynamic analysis are developed from parametric studies as a function of the admissible error, the number of storeys and the relation between the fundamental period and the corner spectrum period. The recommendations are simple to use and more rational and accurate than the ones actually in use in most seismic design codes.     

Seismic response of structures with coupled vertical stiffness–strength irregularities

Several seismic design codes around the world restrict the use of theit Equivalent Lateral Force analysis method to structures satisfying structural regularity limits. These regularity limits are based on engineering judgement and lack quantitative justification. One common irregularity is that of a change in vertical stiffness over the building height. This stiffness irregularity is almost always associated with a change in vertical strength over the building height. For this reason, the effect of various realistic combinations of stiffness–strength irregularity in shear‐type buildings is evaluated to quantify regularity limits. Structures analysed had 3, 5, 9 and 15 storeys, and the floor mass at all the levels were kept the same. Both regular and irregular structures were designed in accordance with the Equivalent Lateral Force procedure to produce the same engineering demand parameter. Structural ductility factors of 1, 2, 3, 4 and 6, and target (design) interstorey drift ratios ranging between 0.5 and 3%, were used in this study. The irregular structures were created by modifying specific storey lateral stiffnesses from that of the regular structure. Strengths at these storeys were also modified to ensure realistic relationships between stiffness and strength. The modified structures were then redesigned until the target interstorey drift ratio was achieved at the critical storey. Inelastic dynamic time‐history analysis was conducted to compare the maximum interstorey drift ratio demands of the regular and irregular structures. Simple equations were developed to estimate possible variations in demand due to vertical stiffness–strength irregularity applied at critical locations in structures. Copyright © 2011 John Wiley & Sons, Ltd.