建筑物偏心结构对其抗震性能的影响

偏心对建筑物的抗震效果有很大的影响。在对三种常见建筑物框架结构在偏心扭矩作用下的受震反应进行数值模拟时,采用6层建筑物模型,通过三维非线性模拟偏心结构对建筑物抗震性能影响的分析,采用最大层间位移作为衡量标准,绘制易损曲线来进行结果分析。结果显示:若忽略意外扭矩的影响,可能会高估钢结构体系的抗震性能,而影响安全评估结果;如果采用全层5%质量偏心来考虑意外偏心扭矩的话,会低估钢结构建筑物的抗震性能。     

基于多层框架的子结构远程协同试验方法研究

将互联网技术应用到子结构混合试验方法中,便形成了基于网络的远程协同试验方法。建立了一套基于OpenFresco试验平台的远程协同试验系统,以一个局部单层的三层多跨偏心支撑组合钢框架结构为原型,取左边跨带有K形偏心支撑的三层钢框架作为试验子结构1,取右边跨带有Y形偏心支撑的单层钢框架作为试验子结构2,进行了缩尺比例为1/2结构模型的局域网协同试验和互联网远程协同试验。根据试验结果,分析了试验子结构的位移加载精度,作动器加载时差,并将混合模型的命令位移与全结构的纯数值模型模拟结果进行了比较。结果表明:在局域网协同试验中,绝大多数工况下的反馈位移峰值与命令位移峰值接近,个别超过了20%,作动器平均每步的加载时差在0.349 s左右,这个时差主要由有限元分析、作动器逼近加载和稳定产生,在7度设防地震作用下,混合模型分析结果与全结构数值模拟结果基本吻合;在互联网远程协同试验中,随着地震波加速度峰值的增大,位移峰值误差有明显的减小趋势并逐渐趋于平稳,作动器平均每步的加载时差比局域网大0.035 s,这个差值主要由网络通讯产生,在8度罕遇地震作用下,混合模型分析结果与全结构模拟结果仍然比较接近。综上,基于OpenFresco建立的远程协同试验系统,具有良好的稳定性和精度,能够有效地对多层框架子结构混合模型进行抗震性能试验。     

高层钢结构建筑横向支撑地震动力响应分析

为测试高层钢结构建筑抗震性能,在有限元模型中以某高层钢框架结构办公大厦作为研究对象,测试其横向支撑地震动力响应状况。选取地震峰值加速度为200 cm/s^2的El-Centro波作为地震波输入,采用瞬态动力方法分析不同楼板厚度下建筑地震模拟响应,得到建筑顶层位移时程曲线;在SAP2000结构软件中分析建筑工程添加横向支撑前后的反应谱,记录各楼层垂直与水平方向位移与层间位移角。得到如下结果:高层钢结构建筑在地震响应下产生的位移不随楼板厚度的增加而增大,楼板厚度为100 mm、170 mm时位移波动显著;添加横向支撑后,建筑水平刚度显著提升,同理,添加横向支撑后横向层间位移角的最大值变化较大,且低于1/250,符合相关建筑标准。     

楼板及其配筋在RC框架结构实现抗震延性机制中的作用分析

总结采用梁有效翼缘来考虑楼板及配筋对“强柱弱梁”机制形成的影响的实验和数值仿真研究。基于SAP2000采用三种侧向加载模式对RC框架结构不带楼板、不带楼板考虑梁刚度放大、带楼板的三个模型进行pushover分析,对力与位移的关系曲线、塑性铰的出铰顺序以及顶点位移与层间位移等方面进行探讨。结果表明:三个模型的“强柱弱梁”现象不带楼板的纯框架结构最明显,考虑梁刚度放大的模型次之,带楼板结构最不明显,证明负弯矩承载力和刚度等反映“强柱弱梁”的参数及塑性铰的出现顺序与楼板、板内配筋存在明显的对应关系;楼板及配筋影响框架结构的整体变形性能和塑性耗能能力,是抗震延性机制实现的重要影响因素。在后续的结构设计中,建议考虑实际楼板和钢筋建模进行计算分析。     

大跨度斜拉桥复杂条件下地震反应分析

本文围绕大跨度斜拉桥结构的地震动输入方式、土-结相互作用以及桥梁动水作用问题展开了如下研究:(1)固定地基地震动输入方式下,采用引入一个‘时差’的方式考虑了行波效应对一座七跨全漂浮结构体系斜拉桥结构的影响,比较了地震行波激励与一致激励作用下桥梁结构关键部位动力响应,分析了两种激励方式下桥梁结构关键部位动力响应的差异,阐明了行波激励作用对桥梁结构动力响应的影响规律,给出了相应抗震措施的建议和方法。(2)针对多跨径大跨度斜拉桥等多波源问题,分别基于刘晶波考虑柱面衰减波和杜修力考虑平面波与远场散射波叠加的单点源粘弹性人工边界,利用波场叠加原理推导出一种多源加权集中粘弹性人工边界条件,给出了其弹簧系数、阻尼系数的计算公式,并通过二维偏心单点源、偏心多点源以及多散射源算例讨论了本文多源加权集中粘弹性人工边界的计算精度     

行波激励下考虑结构碰撞的非规则桥梁抗震性能研究

基于动力学基本原理,建立非规则桥梁的多自由度动力简化模型,根据拉格朗日方程推导简化模型的动力方程,结合龙格—库塔方法,采用自编程序研究行波激励下非规则桥梁综合考虑支座摩擦滑移、结构碰撞等非线性因素作用时的抗震性能。结果表明,行波效应和碰撞效应的共同作用可使矮墩的弯矩需求增大;行波激励可使板式橡胶支座位移增大,地震波最后到达的桥墩其上方支座位移峰值增加最为明显;相比高墩,地震作用下矮墩上部的板式橡胶支座易发生滑动。因此非规则桥梁进行防碰撞设计时应考虑行波激励及支座摩擦,找出相邻结构的最大碰撞力,以指导设计。     

超长混凝土框架梁弹性内力行波效应研究

鉴于超长混凝土框架结构行波效应规律尚缺乏系统研究,借助建筑结构通用有限元软件MI-DAS/GEN,采用一致与非一致两种激励方式对165～1100m/s地震波速作用下长度为33～264m的3层钢筋混凝土框架结构进行弹性时程分析。通过对比一致与非一致激励下的梁弯矩、剪力和轴力,详细讨论了其随波速、长度以及不同部位的变化规律。研究表明:波速越慢,模型越长,行波效应越明显。框架梁弯矩的增大作用主要集中在264m模型第1层两端,减小作用表现在各模型第1层中部和第2、3层的梁上;剪力与弯矩有相似的变化规律;梁中存在拉力与压力,中部各梁的拉力和压力较两端的梁要大。     

大跨曲线桥多点激励下的地震响应分析

用相位谱表征地震动频率的非平稳特性,用相干函数表征地震动空间变化的不相干效应,采用随频率变化的等效相速度代替随意给定的视波速表征地震动的行波效应,生成了具有强度和频率非平稳特性的多点地震动。将这种考虑时间和空间变化的地震动在水平方向作用于5跨高墩连续刚构曲线桥桥墩基础处,计算了墩顶位移及墩底内力,分析了大跨曲线桥多点输入中不相干效应和行波效应对结构响应的影响。结果表明考虑地震动空间变化特性的墩顶位移峰值多数显著大于一致激励。相干性显著增大了激励方向墩底的动内力,但对拟静力位移差动产生的内力有时增大有时减小,两者叠加后的总内力峰值多数大于一致激励。     

某首层柱顶隔震结构动力特性测试研究

为了达到隔震设计的目的并检验隔震层的工作性能,测试分析了采用首层柱顶隔震技术的某五层框架结构在环境激励和初位移条件下的动力特性,得到了结构的前3阶自振特性如自振频率、振型和阻尼比;分析了初位移条件下隔震层的自由衰减曲线和滞回性能.结果表明:环境激励条件下,隔震结构与非隔震结构动力特性相近,隔震结构在正常使用状态下具有足...     

考虑楼板作用的SRC柱-钢梁混合框架动力时程分析

为了解楼板空间作用对型钢混凝土(SRC)柱-钢梁混合框架抗震性能的影响,利用有限元软件ABAQUS分别建立带有楼板和不带楼板的两跨三层SRC柱-钢梁框架,选取2组天然波和1组人工波对其进行弹塑性分析,对比2种框架结构的型钢应力分布、混凝土板损伤、层间相对位移角以及框架基底剪力,分析楼板在结构抗震中的影响规律。结果表明:增加楼板可以有效增加框架抗侧刚度,最大可使层间位移角降低38.7%;同时可以减小核心区梁端塑性区域的面积,减缓型钢上翼缘应力发展速度;而且楼板的存在可使最大基底剪力提升60.7%,有利于减小结构损伤和提高抗震性能。     

Torsional response of symmetric buildings to incoherent and phase‐delayed earthquake ground motion

This paper studies the effect of coherency loss and wave passage on the seismic torsional response of three‐dimensional, multi‐storey, multi‐span, symmetric, linear elastic buildings. A model calibrated against statistical analyses of ground motion records in Mexico City is used for the coherency function. The structural response is assessed in terms of shear forces in structural elements. Incoherence and wave passage effects are found to be significant only for columns in the ground level of stiff systems. The increase of column shears in the ground level is much higher for soft than for firm soil conditions. For the torsionally stiff systems considered, it is found that incoherent and phase‐delayed ground motions do not induce a significant rotational response of the structure. The use of a code eccentricity to account for torsion due to ground motion spatial variation is assessed. On firm soil, the use of a base shear along with an accidental eccentricity results in highly overestimated shear forces; however, for soft soil conditions, code formulations may result in underestimated shear forces. Copyright © 2003 John Wiley & Sons, Ltd.     

不对称大底板多塔楼隔震结构的地震响应分析

针对不对称大底板多塔楼隔震结构体系,通过建立地震响应的动力分析简化模型,推导出不对称大底板多塔楼隔震结构体系地震作用下的运动方程。对一实际的不对称大底板多塔楼隔震结构进行地震响应仿真分析,探讨塔楼质量偏心率和塔楼质量比对结构周期比、位移比和层剪力比的影响。结果显示,不对称大底板多塔楼隔震结构扭转角主要由隔震层产生;与不隔震结构相比,不对称大底板多塔楼隔震体系的扭转角减小,可取得较好的减震效果;塔楼与底板的位置分布和质量分布会影响体系的扭转效应和减震效果,应尽量使塔楼的质心与底板质心重合,塔楼质量分布均匀,以减小结构的扭转效应,提高减震效果。     

含偏心钻铤充液井孔中正交偶极子声波测井的数值模拟研究

采用三维有限差分方法模拟了正交偶极子声源在含偏心钻铤的充液井孔中激发的声场,研究了钻铤偏心对模式波的种类、激发幅度、以及频散特征的影响.研究结果表明,钻铤偏心导致偶极子声源激发的声场的模式不唯一,观察到了除偶极模式外的单极模式波和四极模式波;钻铤偏心导致偶极模式波出现分裂现象,尤其是快速地层F2模式和慢速地层弯曲波的稍高频率的部分,且快、慢波所对应的两个方位为偏心的方位和与偏心方位垂直的方向;井孔折射横波以及快速地层F2模式的低频部分的慢度基本未受到钻铤偏心的影响,仍然能够正确反映地层的横波慢度及各向异性;对于本文研究的慢速地层井孔模型,当偏心距离l小于等于0.01 m时,弯曲波的慢度和激发幅度受钻铤偏心的影响很小,从快、慢弯曲波中提取的快、慢横波慢度基本能够反映地层的各向异性特征.     

Accidental eccentricity in symmetric buildings due to wave passage effects arising from near‐fault pulse‐like ground motions

This article investigates the characteristics of the accidental eccentricity in symmetric buildings due to torsional response arising from wave passage effects in the near‐fault region. The soil–foundation–structure system is modeled as a symmetric cylinder placed on a rigid circular foundation supported on an elastic halfspace and subjected to obliquely incident plane SH waves simulating the action of near‐fault pulse‐like ground motions. The translational response is computed assuming that the superstructure behaves as a shear beam under the action of translational and rocking base excitations, whereas the torsional response is calculated using the mathematical formulation proposed in a previous study. A broad range of properties of the soil–foundation–structure system and ground motion input are considered in the analysis, thus facilitating a detailed parametric investigation of the structural response. It is demonstrated that the normalized accidental eccentricity is most sensitive to the pulse period (T_P) of the near‐fault ground motions and to the uncoupled torsional‐to‐translational fundamental frequency ratio (Ω) of the structure. Furthermore, the normalized accidental eccentricities due to simplified pulse‐like and broadband ground motions in the near‐fault region are computed and compared against each other. The results show that the normalized accidental eccentricity due to the broadband ground motion is well approximated by the simplified pulse for longer period buildings, while it is underestimated for shorter period buildings. For symmetric buildings with values of Ω commonly used in design practice, the normalized accidental eccentricity due to wave passage effects is less than the typical code‐prescribed value of 5%, except for buildings with very large foundation radius. Copyright © 2017 John Wiley & Sons, Ltd.     

ON ECCENTRIC SEISMIC POUNDING OF SYMMETRIC BUILDINGS

Results of a parameter study on eccentric pounding of two symmetric single storey systems under seismic excitation are presented. Linear behaviour is assumed, and pounding effect is considered using the restitution coefficient approach. The effect of impact eccentricity is studied on two sets of symmetric models symmetrically and asymmetrically aligned with respect to each other for several gap widths, period dependent gaps and three values of the torsional-to-lateral frequency ratio. Two time histories are used for input. On the whole it was found that impact eccentricity amplifies the response relative to symmetric impact but the effect is not proportional to first impact eccentricity. Also, increasing gap width is likely to be effective when the separation is sufficiently wide practically to eliminate contact. Larger torsional rigidity tends to lower response amplification. SRSS code-type gaps appear to be adequate, or even excessive, when the design spectrum is compatible with the expected earthquake record at the site.     

Response spectrum techniques for asymmetric buildings

A scheme is proposed to calculate the effect of torsion on each lateral load resisting element of asymmetrical buildings in the context of the response spectrum technique. The scheme consists of: (i) Obtain the modal shear and torque on the building by the response spectrum technique, (ii) Compute the total modal shear forces on each frame by resolving the modal shear and torque on the building according to principles of structural mechanics. The shears on each frame due to the lateral load effect and torsional effect are combined algebraically, (iii) Obtain the total shear force on each frame by combining the total modal shears on that frame in a root sum square manner. Since the proper phase relationship between the lateral load effect and torsional effect is accounted for on a modal basis, it is believed that the proposed scheme provides a more realistic load estimate on the frames than the conventional approach. An example of a simplified mono-symmetrical frame structure is chosen to illustrate the accuracy of the proposed scheme, using dynamic time-history analysis as a standard for comparison.     

双向速度脉冲地震下偏心重力柱核心筒结构的弹塑性地震响应研究

研究速度脉冲地震和结构质量偏心综合不利条件下新型重力柱-核心筒结构体系的弹塑性反应规律。选取速度脉冲和非速度脉冲地震加速度记录各10条,进行地震动双向输入,采用结构非线性分析软件CANNY进行有限元数值分析,研究脉冲型地震和结构质量偏心对新型体系弹塑性地震反应的影响。分析结果表明,速度脉冲型地震作用下各结构的层间位移角、层间剪力和层间扭转角显著高于非速度脉冲地震下的相应值。质量偏心对结构弹塑性抗震需求影响显著,层间位移角和层间扭转角都随着偏心率的增大而增大,而层间剪力则随偏心率的增大呈减小趋势。建议在重力柱-核心筒结构设计中应重视速度脉冲地震和结构偏心的耦合不利影响。     

建筑结构震害预测程序

本文介绍了建筑结构的震害预测程序PEEDS中的震害预测方法及程序的结构和功能。该程序根据目前结构的分类方法，包括多层砖混结构、单层砖平房、单层砖柱厂房、单层钢筋混凝土柱厂房、钢筋混凝土框架结构、独立烟囱和筒支水塔的震害预测。     

Seismic torsional provisions for dynamic eccentricity

A study is made of the dynamic torsional response of a single mass partially symmetric system to ground excitation. Using the response spectrum technique, the torsional response and dynamic eccentricity are determined as functions of the eccentricity of the system and its uncoupled frequency ratio. It is shown that the dynamic eccentricity can best be expressed as a bilinear function of eccentricity. For the critical condition which occurs when the uncoupled frequency ratio is unity, a comparison is made with the torsional provisions of five seismic codes (Canada, Mexico, New Zealand, ATC3 and Germany). It is shown that the first four codes underestimate the torsional moment, and also the edge displacement of the system, significantly when the eccentricity is small and the uncouped torsional and lateral frequencies are close.