Criterion of stability and implementation issues of hybrid frequency-time-domain procedure for non-linear dynamic analysis

A criterion of stability pertaining to the hybrid frequency-time-domain procedure is derived. It stems from the initial-value theorem on one side and from the condition of convergence which applies to the harmonic counterpart of the procedure on the other side. The criterion depends on the dynamic stiffnesses of both the original non-linear system and the pseudo-linear system evaluated at the Nyquist frequency. Since at this frequency both stiffnesses are usually controlle by the mass, the criterion of stability is satisfied for most structural systems. The procedure must, however, be applie sequentially to individual time segments. The validity of this criterion is confirmed by a numerical investigation performe for a SDOF system. The solution of non-linear dynamic problems requires consideration of implementation issues which are also discusse in the paper. The analysis of a non-linear soil-structure-interaction system in which the soil's stiffness coefficients an directly defined in the frequency domain also demonstrates the accuracy of the hybrid frequency-time-domain procedure.     

Seismic response of the superstructure and attached equipment in a base-isolated building

Base isolation can be used both to protect the structure and simultaneously to reduce the response of internal equipment. The seismic response of a base-isolated structure has been studied through the shaking table test or numerical calculation before. The object of this paper is to analyse a base-isolated structure by a different analytical approach—perturbation analysis. Recognizing that the horizontal stiffness of an isolation system is much smaller than that of the superstructure, the mathematical expressions of the modal properties of base-isolated structures are derived by the perturbation method in terms of the modal properties of the superstructure and used to study the dynamic response of superstructure and attached equipment in the base-isolated building. This study shows that the first base-isolated mode not only controls the superstructural response but also dominates the response of high-frequency attachment. The contribution of higher modes to the response of base-isolated structures, which is proportional to the horizontal stiffness of isolation system, is very small.     

考虑土-结构相互作用的框架结构抗震性能分析

目前结构的抗震分析主要是采用刚性地基假定,忽略了土-结构相互作用,而在实际情况中结构的地震破坏与刚性地基假定的预期结果并不相同。为了对比差异,本文以一6层混凝土框架结构为例,分别进行了Pushover分析和非线性时程分析。结果表明:当考虑土-结构相互作用时,结构的基底剪力减小,周期增大,顶点位移增大且结构的破坏主要集中在首层,柱端出现了塑性铰,更符合实际的震害情况。并将Pushover分析与非线性时程分析的结果进行对比,验证了Pushover分析的可靠性。     

基础隔震高层建筑地震响应的理论分析

本文对某高层隔震框架－剪力墙结构的三维地震响应进行了有限元分析计算，对比了隔震结构及其相应非隔震结构的动力特性，给出了在多遇地震和罕遇地震作用下结构的最大层间剪力，层间位移等，得到一些有意义的结论。     

A modal procedure for seismic analysis of non-linear base-isolated multistorey structures

A modal procedure for non-linear analysis of multistorey structures with high-damping base-isolation systems was proposed. Two different isolation devices were considered in the analysis: an high-damping laminated rubber bearing and a lead-rubber bearing. Starting from deformational properties verified by tests, the isolation systems were characterized using three different analytical models (an Elastic Viscous, a Bilinear Hysteretic and a Wen's Model) with parameters depending from maximum lateral strain. After non-linear modelling of isolation and lateral-force-resisting systems, the effects of material non-linearities were considered as pseudo-forces applied to the equivalent linear system (Pseudo-Force Method) and the formally linearized equations of motion were uncoupled by the transformation defined by the complex mode shapes. The modal responses were finally obtained with an extension of Nigam–Jennings technique to non-linear and non-classically damped systems, in conjunction with an iterative technique searching for non-linear contributions satisfying equations of motion and constitutive laws. Since the properties of the isolated structure usually change with maximun lateral strain of isolation bearings, the integration of a new set of governing equations was required for each design-displacement value. The procedure proposed was described in detail and then applied for the determination of modal and total seismic responses in some real cases. At first, a very good agreement between non-linear responses obtained with the proposed mode superposition and with a direct integration method was observed. Then a comparison of results obtained with the three different analytical models of the isolation bearings was carried out. At last, the exact modal response obtained with analytical models depending from the design displacement of the isolation bearings was compared with two different approximated solutions, evaluated using mode shapes and isolation properties, respectively, calculated under simplified hypothesis.© 1998 John Wiley & Sons, Ltd.     

近断层脉冲型地震动作用下隔震结构地震反应分析

隔震结构在远震场地减震效果良好，但是近断层地震动的明显的长周期速度和位移脉冲运动可能对隔震建筑等长周期结构的抗震性能和设计带来不利影响，需要深入探讨。本文首先讨论近断层地震动的长周期脉冲运动特征，然后以台湾集集地震8条典型近震记录和其它4条常用近震记录以及4条远震记录作为地震动输入，对两幢安装铅芯橡胶隔震支座的钢筋混凝土框架隔震结构进行非线性地震反应时程分析，通过比较探讨了算例计算结果，定量说明隔震结构的近震脉冲效应显著，是隔震设计不容忽视的问题。     

考虑土-结构相互作用的西安钟楼地震反应分析

为探讨土-结构相互作用对西安钟楼地震反应的影响,建立了钟楼上部木结构-台基-地基三维有限元模型,基于粘-弹性人工边界条件,利用振型分解反应谱法进行了地震反应分析。结果表明,考虑相互作用木结构2层相对位移反应增大了2.12倍,台基相对于地面间的相对位移增大了44%。因此,在对钟楼结构进行地震反应分析时必须考虑土-结构相互作用。     

双塔连体高层混合结构抗震性能研究

外钢框架-混凝土核心筒结构体系被认为是适合我国国情的高层建筑结构体系之一,我国已有多个采用这种结构体系的单塔楼工程实例,但对双塔连体高层混合结构的研究较少。本文针对上海国际设计中心不等高双塔连体混合结构,进行了7度多遇地震、基本烈度、罕遇地震和8度罕遇地震阶段的模拟地震振动台试验研究,得到了结构的破坏模式,并对模型结构和原型结构的动力反应进行了详细的分析,最后提出了此类结构设计的一些建议。研究表明,高位连体的竖向地震反应比较明显,设计中应适当考虑动力放大效应;在各水准地震作用下结构整体变形均呈现弯曲型;主塔楼核心筒在中震下可以保证"不坏",但结构小震下的层间位移略超过规范限值。     

Seismic analysis of a building block

This paper reports on the study of the seismic response of an urban building block located in Faial, a town of the Horta Island of the Azores, Portugal. The work fits within the framework of studying strengthening schemes suitable for the reconstruction process of a town damaged by an earthquake action and includes numerical modelling of all the building blocks with calibration of material and structural parameters based on ambient vibration tests. The study aims at understanding a number of issues that are likely to influence the global behaviour of the block and the local response of individual buildings, namely the group effect of adjacent constructions, the in-plane stiffness of floors and/or roofs and the presence of possible localized strengthening interventions in selected parts of the block.     

Seismic response reduction analysis of large chassis base-isolated structure under long-period ground motions

Long-period structures(e.g. Isolated structures) tend to produce pseudo-resonance with low frequency components of long-period ground motions, resulting in the increase in damage. Stiffness mutation occurs due to the setback in the upper body of the large chassis structure. In the parts with stiffness mutation, the torsion effect caused by the tower is far greater than that of the chassis itself. In this study, a total of 273 ground motions are collected and then filtered into four types, including the near-field ordinary, near-field pulse, far-field ordinary, and farfield harmonic. An 8-degree(0.2 g) fortified large chassis base-isolated structure is established. Furthermore,ETABS program software is used to conduct nonlinear time history analysis on the isolation and seismic model under bi-directional earthquake ground motions. The comparison results show that the seismic isolation effect of the base-isolated structure under long-period ground motions is worse than that associated with ordinary ground motions when the seismic response reduction rate of the large base floor significantly decreases compared with that of the tower. When the inter-story displacement angle and the displacement of isolation layer of the chassis exceeds the limit of Code for Seismic Design of Buildings(GB 50011-2010), it is recommended to adopt composite seismic isolation technology or add limit devices. Under the condition of long-period ground motions, the baseisolated structure reduces the lateral-torsional coupling effect of the large chassis structure, while the torsion response of large chassis' top layer increases. Under long-period ground motions with the same acceleration peak,the response of the base-isolated structure increases much more than that of the seismic structure and the consideration of this impact is suggested to be added to the Code.     

节能住宅地震反应分析

为研究节能房屋的抗震能力,本文基于墙体试验研究成果,建立了墙体的恢复力模型及其抗震抗剪强度公式,并对内砖外加气混凝土砌块墙体节能房屋进行了地震反应分析.本项研究为节能住宅的推广应用提供了抗震设计依据.     

Seismic analysis of two‐way asymmetric building systems under bi‐directional seismic ground motions

An approximation approach of seismic analysis of two‐way asymmetric building systems under bi‐directional seismic ground motions is proposed. The procedures of uncoupled modal response history analysis (UMRHA) are extended to two‐way asymmetric buildings simultaneously excited by two horizontal components of ground motion. Constructing the relationships of two‐way base shears versus two‐way roof translations and base torque versus roof rotation in ADRS format for a two‐way asymmetric building, each modal pushover curve bifurcates into three curves in an inelastic state. A three‐degree‐of‐freedom (3DOF) modal stick is developed to simulate the modal pushover curve with the stated bifurcating characteristic. It requires the calculation of the synthetic earthquake and angle β. It is confirmed that the 3DOF modal stick is consistent with single‐degree‐of‐freedom modal stick in an elastic state. A two‐way asymmetric three‐story building was analyzed by UMRHA procedure incorporating the proposed 3DOF modal sticks. The analytical results are compared with those obtained from nonlinear response history analysis. It is shown that the 3DOF modal sticks are more rational and effective in dealing with the assessment of two‐way asymmetric building systems under two‐directional seismic ground motions. Copyright © 2007 John Wiley & Sons, Ltd.     

强震观测建筑结构的地震反应分析

选择取得强震观测资料的建筑结构为研究对象，采用有限元法建立结构的动力反应分析模型，利用SAP2000程序分析了结构的地震反应，并同实际记录到的结构地震反应进行了对比分析，讨论了结构模型参数估计和一些不确定因素对模型精度的影响。     

基于土-结构相互作用的地铁车站抗震研究

以土—结构动力相互作用理论为基础,对于不考虑核爆炸荷载作用下地铁车站的抗震问题进行了探讨,提出了抗震设计建议。     

Seismic response of multistoried buildings including the effects of soil-structure interaction

A simplified response spectrum superposition method has been generalized for the dynamic analysis of the multistoried building-soil response to earthquake ground motions via Fourier-transformed frequency domain. It involves the “scaling” of the Fourier amplitudes of the freefield translational and rocking motions to account for the soil-structure interaction effects, and then analyzing the building as fixed at the base. Envelopes of peak displacements, shear forces and overturning moments in the building are illustrated in terms of the order statistics of the response peaks.     

SMA-压电半主动混合阻尼器减震控制分析

将形状记忆合金（Shape memory alloy,简称"SMA"）与压电摩擦阻尼器复合设计了一种半主动混合阻尼器,对SMA丝进行了材性试验,分析了循环圈数、加载速率和应变幅值对SMA丝力学性能的影响。基于试验数据,以速度方向和应变值作为神经元输入,建立了SMA的BP神经网络本构模型,并利用T-S模糊逻辑求解压电陶瓷驱动器输出电压,对1个2层的钢框架结构进行了无控、SMA被动控制和混合控制MATLAB仿真分析。结果表明:SMA的BP网络模型预测的应力误差大多集中在20 MPa以内,且误差较大点主要集中在加载的初始段和卸载的结束段等数值较小的点,BP神经网络能够较好地预测SMA丝的本构曲线。相比SMA被动控制,混合阻尼器可以更加有效地降低结构的动力反应。     

考虑土-结构相互作用双层柱面网壳在多点输入下的地震反应分析

目前对于网壳结构的地震反应研究大部分仍然采用一致输入,特别是没有考虑土-结构相互作用对网壳结构的影响。本文通过对大型有限元分析软件MSC.Nastran的二次开发,用等效线性化方法考虑土体的非线性,对土体采用三维实体单元建模,并对土体在基岩面上采用地震动的多点输入,计算分析了大跨度双层柱面网壳的动力反应,并且与一致地震动输入下网壳结构的地震反应进行了对比,考察了两者之间的差异,深入分析了考虑土-结构相互作用下,双层柱面网壳结构在多点输入和一致输入下的地震反应规律,并得出了一些重要结论。     

Seismic wave input method for three-dimensional soil-structure dynamic interaction analysis based on the substructure of artificial boundaries

Earthquake Engineering and Engineering Vibration - The method of inputting the seismic wave determines the accuracy of the simulation of soil-structure dynamic interaction. The wave method is a...     

Seismic analysis of base-isolated liquid storage tanks using the BE–FE–BE coupling technique

A three-dimensional soil–structure–liquid interaction problem is numerically simulated in order to analyze the dynamic behavior of a base-isolated liquid storage tank subjected to seismic ground motion. A dynamic analysis of a liquid storage tank is carried out using a hybrid formulation, which combines the finite shell elements for structures and the boundary elements for liquid and soil. The system is composed of three parts: the liquid–structure interaction part, the soil–foundation interaction part, and the base-isolation part. In the liquid–structure interaction part, the tank structure is modeled using the finite elements and the liquid is modeled using the internal boundary elements, which satisfy the free surface boundary condition. In the soil–foundation interaction part, the foundation is modeled using the finite elements and the half-space soil media are modeled using the external boundary elements, which satisfy the radiation condition in the infinite domain. Finally, above two parts are connected with the base-isolation system to solve the system's behavior. Numerical examples are presented to demonstrate the accuracy of the developed method, and an earthquake response analysis is carried out to demonstrate the applicability of the developed technique. The properties of a real LNG tank located in the west coast of Korea are used. The effects of the ground and the base-isolation system on the behavior of the tank are analyzed.