基于NEESgrid网络的子结构拟动力实验:Mini-MOST实验

美国国家科学基金(US National Sc ience Foundation,简称NSF)资助研制开发的地震工程模拟网络(Network for Earthquake Engineering S imu lation,简称NEES)包括15个分布在不同地点的设备站点,并使用NEESgrid网络相互连接。NEESgrid是一个先进的网络设施,它为地震工程研究,尤其是多地点的子结构拟动力实验(Mu lti-site Substructure Pseudo-dynam ic,缩写为MS-PSD)提供了丰富的工具。本文首先简单地介绍了NEES和NEESgrid,然后使用了一个小尺寸的模型实验(M in i-MOST)演示了利用NEESgrid进行MS-PSD实验的过程。实验原型为一个单层二跨的框架结构,实验将该结构划分为两个实验子结构和一个模拟子结构。实验中,这三个子模块使用一个基于M atlab仿真协调程序SIMCOR进行协调,实验的每一步,SIMCOR发送位移请求给各个子模块并接收各子模块恢复力反馈,同时使用a-OS方法计算结构反应以及下一步的位移。实验结果与分析结果吻合相当好,展示了NEESgrid在多地点远程拟动力实验方面的能力。     

基于多尺度混合有限元模型的钢框架地震时程分析

为了研究建筑结构在强震作用下的微观破坏机理以及提高建筑结构地震反应分析的精确性和可靠性,将多尺度有限元分析方法引入抗震混合试验中。根据经验将复杂结构在地震作用下表现出来的特性划分为线性,非线性以及强非线性部分,形成由宏观有限元模型模拟线性部位,微观有限元模型模拟非线性部位以及试验单元模拟用有限元单元难以模拟的强非线性部位的多尺度混合有限元模型。本文基于3层4跨Benchmark钢框架模型建立多尺度混合有限元模型进行地震反应分析。通过多尺度混合有限元模型与相应普通有限元模型之间的地震时程对比分析,验证了多尺度模型在抗震混合模拟试验中与普通有限元模型相比具有耗时相对较小同时能够得到较高精度的优越性。     

多点地震动输入下的拟动力实验方法

本文将拟动力实验方法应用于多点地震输入下的结构响应研究中,采用子结构技术解决了结构在多点地震输入下的实验问题。针对不同类型结构和不同方向的地震动输入,文中给出了相应的似动力实验的数值积分方法。最后采用两点地震动输入对所提出的方法进行了实验验证,证明该方法的有效性。     

带粘弹性阻尼器的斜拉索动力混合仿真

利用MATLAB程序编写了针对带粘弹性阻尼器的斜拉索结构地震响应的计算软件,同时利用Visual C++语言开发了PCS8000控制器与计算软件之间的接口通讯软件(PMI),建立起了数值子结构与试验子结构之间数据传输的桥梁。通过MATLAB程序纯理论计算与混合仿真实验的比较,证明实验结果与纯数值计算的一致性,从而验证了斜拉索结构混合仿真的可靠性。     

采用消能连梁的高层结构整体分析与试验研究

消能连梁采用阻尼器耗能,保护混凝土主体结构,是近年来发展出来的一种有效的高层结构消能减震体系。本文针对带消能连梁的框架剪力墙结构体系进行整体有限元分析,研究了具有不同层数的框架剪力墙结构地震响应,分析消能连梁的能量耗散情况和对整体结构动力响应的控制效果,研究表明消能连梁能够分别降低首层墙肢和框架的能量耗散的65.5%和39.0%,同时可降低结构35.4%~42.0%的层间位移角和41.0%~44.4%的基底剪力。随后对某一18层高层建筑进行了子结构混合试验研究,试验体底部为6层联肢墙,采用1/3缩尺,其余结构分为上部剪力墙数值子结构和框架数值子结构,分别采用ABAQUS软件进行分析,三者协同工作,共同完成大震响应模拟。子结构混合试验结果表明,消能连梁可有效降低结构的整体响应,层间位移角降低16%、基底剪力降低21%。同时可控制连梁损伤,提高结构耗能能力。     

基于数值解与解析解耦合的SSI体系地震反应分析方法

基于子结构分析方法,提出了土-结构相互作用体系中数值解和解析解耦合的地震反应分析方法。此方法中,数值解是用有限元方法来模拟上部结构的非线性动力行为;而弹性结构-刚性基础-半无限大弹性地基中频域内的解析解,是通过离散时间递归滤波方法得到时域内的解来等效,且在整个体系中,利用土、结构两个子结构边界上的力和位移协调求解。本文提出的方法用有限元程序Opensees来实现,并用于一个线弹性单层框架结构的动力分析中。这种耦合的分析方法得到的结果,与土-结构相互作用单自由度体系的解析解进行了比较,验证此方法的精度、稳定性和工程实用性。     

子结构地震模拟振动台混合试验原理与实现

为了解决地震模拟振动台承载能力及台面尺寸对大型结构试验的限制,扩展振动台的功能,本文提出了子结构地震模拟振动台混合试验方法、试验过程及实时数值积分方法,并给出了试验子结构边界条件的两种模拟形式.通过一个简单框架结构的地震模拟振动台试验和子结构混合加载试验验证了该方法的可行性,并指出了该试验方法的主要技术问题.混合试验方法通过子结构技术和振动台试验相结合,解决了目前的地震模拟振动台试验和拟动力试验在设备规模和加载速度上的局限性.     

位移控制的子结构地震模拟振动台混合试验方法

为了解决地震模拟振动台承载能力及台面尺寸对大型结构试验的限制,扩展振动台的功能,提出了位移控制子结构地震模拟振动台混合试验方法,包括试验原理、试验过程及数值积分方法,并给出了2种子结构边界条件的模拟形式.通过1个简单框架结构的地震模拟振动台试验和子结构混合加载试验验证了该方法的可行性,并指出了该试验方法的主要技术问题.混合试验方法通过子结构技术和振动台试验相结合,解决了目前的地震模拟振动台试验和拟动力试验在设备规模和加载速度上的局限性.     

TMD多点控制体系随机地震响应分析的虚拟激励法

对于频率分布密集或受频带较宽的地震激励的结构，其响应不再以某一单一振型为主，须考虑采用多点控制。本文对受TMD多点控制的结构进行了研究。文中建立了带有多个子结构系统的以模态坐标和子结构自由度为未知量的统一运动方程。针对所得方程为非对称质量、非对称刚度、非经典阻尼的情况，本文给出了使用直接法求解的格式。地震随机响应分析采用了虚拟激励法，可以考虑各振型之间的耦合项，计算量小且精度高。本文的方法适用于带有多个子结构的系统的一般性问题，具有广泛的应用价值。     

大空间地下结构地震响应混合试验研究

基于OpenSees-OpenFresco-MTS混合试验系统,选取关键构件底层中柱,进行大空间地下结构地震响应混合试验研究。在混合试验过程中,取结构底层中柱为试验子结构,取结构剩余部分与土体为数值子结构。为了满足试验要求,开发了一种专用于混合试验的可变刚度钢构件。通过更换柱脚螺杆改变试验装置侧向刚度。在混合试验前,根据数值模型中对应单元侧向刚度确定钢构件侧向刚度;根据幅值比和相位差等频域指标评价混合试验结果。试验结果显示:在上海人工波工况、El Centro波工况和Kobe波工况中,理论结果与试验结果匹配良好。在以大空间地下结构地震响应为研究对象时,基于OpenSees-OpenFresco-MTS的混合试验系统具有良好的稳定性与精确性。     

Numerical characteristics of peer‐to‐peer (P2P) internet online hybrid test system and its application to seismic simulation of SRC structure

The peer‐to‐peer (P2P) Internet online hybrid test system has been developed for the seismic simulation of a structure. In this study, the stability and accuracy of the system are investigated analytically by studying the spectral radius of the recursive matrix of the test scheme featuring a two‐round quasi‐Newton test scheme. The applicability of the system is further examined by exploring the seismic responses of a complex structure, a steel‐encased reinforced concrete (SRC) structure with a steel tower on the top. The structure is divided into two numerical substructures and one tested part for hybrid test. The numerical substructures are simulated by sophisticated finite element method (FEM) models with material nonlinearities to capture local plastifications. Two types of FEM programs, namely OpenSEES and ABAQUS, which are suitable for the SRC part and the steel tower, respectively, are employed. The results demonstrate that the P2P system is able to simulate complex structures with significant nonlinearities. As compared with the previous study in which two elastic numerical substructures were considered, increase in the number of iterations in this study is not significant, because the associated nonlinearities are limited due to the small time interval adopted in the test. Copyright © 2007 John Wiley & Sons, Ltd.     

Large‐scale real‐time hybrid simulation involving multiple experimental substructures and adaptive actuator delay compensation

Real‐time hybrid simulation provides a viable method to experimentally evaluate the performance of structural systems subjected to earthquakes. The structural system is divided into substructures, where part of the system is modeled by experimental substructures, whereas the remaining part is modeled analytically. The displacements in a real‐time hybrid simulation are imposed by servo‐hydraulic actuators to the experimental substructures. Actuator delay compensation has been shown by numerous researchers to vitally achieve reliable real‐time hybrid simulation results. Several studies have been performed on servo‐hydraulic actuator delay compensation involving single experimental substructure with single actuator. Research on real‐time hybrid simulation involving multiple experimental substructures, however, is limited. The effect of actuator delay during a real‐time hybrid simulation with multiple experimental substructures presents challenges. The restoring forces from experimental substructures may be coupled to two or more degrees of freedom (DOF) of the structural system, and the delay in each actuator must be adequately compensated. This paper first presents a stability analysis of actuator delay for real‐time hybrid simulation of a multiple‐DOF linear elastic structure to illustrate the effect of coupled DOFs on the stability of the simulation. An adaptive compensation method then proposed for the stable and accurate control of multiple actuators for a real‐time hybrid simulation. Real‐time hybrid simulation of a two‐story four‐bay steel moment‐resisting frame with large‐scale magneto‐rheological dampers in passive‐on mode subjected to the design basis earthquake is used to experimentally demonstrate the effectiveness of the compensation method in minimizing actuator delay in multiple experimental substructures. Copyright © 2011 John Wiley & Sons, Ltd.     

Accurate real‐time hybrid earthquake simulations on large‐scale MDOF steel structure with nonlinear viscous dampers

This paper presents real‐time hybrid earthquake simulation (RTHS) on a large‐scale steel structure with nonlinear viscous dampers. The test structure includes a three‐story, single‐bay moment‐resisting frame (MRF), a three‐story, single‐bay frame with a nonlinear viscous damper and associated bracing in each story (called damped braced frame (DBF)), and gravity load system with associated seismic mass and gravity loads. To achieve the accurate RTHS results presented in this paper, several factors were considered comprehensively: (1) different arrangements of substructures for the RTHS; (2) dynamic characteristics of the test setup; (3) accurate integration of the equations of motion; (4) continuous movement of the servo‐controlled hydraulic actuators; (5) appropriate feedback signals to control the RTHS; and (6) adaptive compensation for potential control errors. Unlike most previous RTHS studies, where the actuator stroke was used as the feedback to control the RTHS, the present study uses the measured displacements of the experimental substructure as the feedback for the RTHS, to enable accurate displacements to be imposed on the experimental substructure. This improvement in approach was needed because of compliance and other dynamic characteristics of the test setup, which will be present in most large‐scale RTHS. RTHS with ground motions at the design basis earthquake and maximum considered earthquake levels were successfully performed, resulting in significant nonlinear response of the test structure, which makes accurate RTHS more challenging. Two phases of RTHS were conducted: in the first phase, the DBF is the experimental substructure, and in the second phase, the DBF together with the MRF is the experimental substructure. The results from the two phases of RTHS are presented and compared with numerical simulation results. An evaluation of the results shows that the RTHS approach used in this study provides a realistic and accurate simulation of the seismic response of a large‐scale structure with rate‐dependent energy dissipating devices. Copyright © 2015 John Wiley & Sons, Ltd.     

强震作用下机场高耸塔台结构抗震性能分析

为提升强震作用下机场高耸塔台结构的抗震性能及安全,采用非线性时程分析方法研究高耸塔台结构的强震损伤分布规律;基于性能化抗震设计方法确定塔台关键构件抗震性能水准,对高耸塔台结构进行性能化抗震设计和损伤控制;最后分析了竖向地震对高耸塔台结构强震损伤的影响.分析得到,采用多遇地震设计的塔台结构,在罕遇地震作用下塔台结构层间位...     

Performance evaluation of a distributed hybrid test framework to reproduce the collapse behavior of a structure

A hybrid numerical and experimental simulation to collapse was conducted on a one‐half scale moment‐resisting frame building with two experimental substructures at different locations. An extensible hybrid test framework was used that adopts a generalized interface to encapsulate each numerical or tested substructure, through which only boundary displacements and forces are exchanged. Equilibrium and compatibility between substructures are enforced by an iterative quasi‐Newton procedure, while adopting a predictor‐and‐corrector method to avoid loading reversals on physically tested substructures. To overcome difficulties in controlling stiff axial and rotational deformations at the boundaries, the flexible test scheme employs either open‐loop or closed‐loop control at the boundaries: enforcing either compatibility or equilibrium, or both requirements at critical boundaries. The effectiveness of the extensible framework and its capability to simulate structural behavior through collapse is demonstrated by a geographically distributed test that reproduced the collapse behavior of a four‐story, two‐bay, steel moment frame previously tested on an earthquake simulator. A comparison of both experiments highlights the viability of the hybrid test as an effective tool for the performance evaluation of structural systems from the onset of damage through collapse. Copyright © 2011 John Wiley & Sons, Ltd.     

Column restraint in post‐tensioned self‐centering moment frames

Gaps between beam‐to‐column interfaces in a post‐tensioned (PT) self‐centering frame with more than one column are constrained by columns, which causes beam compression force different from the applied PT force. This study proposes an analytical method for evaluating column bending stiffness and beam compression force by modeling column deformation according to gap‐openings at all stories. The predicted compression forces in the beams are validated by a cyclic analysis of a three‐story PT frame and by cyclic tests of a full‐scale, two‐bay by first‐story PT frame, which represents a substructure of the three‐story PT frame. The proposed method shows that compared with the strand tensile force, the beam compression force is increased at the 1st story but is decreased at the 2nd and 3rd stories due to column deformation compatibility. The PT frame tests show that the proposed method reasonably predicts beam compression force and strand force and that the beam compression force is 2 and 60% larger than the strand force with respect to a minor restraint and a pin‐supported boundary condition, respectively, at the tops of the columns. Therefore, the earlier method using a pin‐supported boundary condition at upper story columns represents an upper bound of the effect and is shown to be overly conservative for cases where a structure responds primarily in its first mode. The proposed method allows for more accurate prediction of the column restraint effects for structures that respond in a pre‐determined mode shape which is more typical of low and mid‐rise structures. Copyright © 2009 John Wiley & Sons, Ltd.     

某海底沉管隧道风塔及下部结构抗震性能分析

为研究某海底隧道风塔及下部结构体系在塑性阶段的损伤破坏形态及特点,探讨在多重荷载作用下弹塑性静动力响应对结构的影响,建立了沉管隧道风塔及下部结构的大型三维有限元模型。采用基于能量原理的混凝土塑性及损伤本构模型,借助大型有限元软件ANSYS及ABAQUS分别对结构进行不同地震条件下的动力时程分析,对比分析振型、层间位移角及较为完整的塑性损伤破坏系数曲线。结果表明:不同设防地震下,结构整体性良好,振型及层间位移角满足规范要求;不同罕遇地震下,该结构的混凝土塑性拉压损伤最大时刻均发生在20 s,主要破坏区域在风塔与人防井及下部立柱的接触位置,且拉伸破坏系数明显高于压缩破坏。本文的研究成果可以为类似近海沉管隧道工程抗震设计提供一定的依据与指导。     

Implementation of online model updating in hybrid simulation

Hybrid simulation combines numerical and experimental methods for cost‐effective, large‐scale testing of structures under simulated earthquake loading. Structural system level response can be obtained by expressing the equation of motion for the combined experimental and numerical substructures, and solved using time‐stepping integration similar to pure numerical simulations. It is often assumed that a reliable model exists for the numerical substructures while the experimental substructures correspond to parts of the structure that are difficult to model. A wealth of data becomes available during the simulation from the measured experiment response that can be used to improve upon the numerical models, particularly if a component with similar structural configuration and material properties is being tested and subjected to a comparable load pattern. To take advantage of experimental measurements, a new hybrid test framework is proposed with an updating scheme to update the initial modeling parameters of the numerical model based on the instantaneously‐measured response of the experimental substructures as the test progresses. Numerical simulations are first conducted to evaluate key algorithms for the selection and calibration of modeling parameters that can be updated. The framework is then expanded to conduct actual hybrid simulations of a structural frame model including a physical substructure in the laboratory and a numerical substructure that is updated during the tests. The effectiveness of the proposed framework is demonstrated for a simple frame structure but is extendable to more complex structural behavior and models. Copyright © 2013 John Wiley & Sons, Ltd.     

Hybrid simulation of steel frame structures with sectional model updating

Hybrid simulations that combine numerical computations and physical experiment represent an effective method of evaluating the dynamic response of structures. However, it is sometimes impossible to take all the uncertain or nonlinear parts of the structure as the physical substructure. Thus, the modeling errors of the numerical part can raise concerns. One method of solving this problem is to update the numerical model by estimating its parameters from experimental data online. In this paper, an online model updating method for the hybrid simulation of frame structures is proposed to reduce the errors of nonlinear modeling of numerical substructures. To obtain acceptable accuracy with acceptable extra computation efforts as a result of model parameter estimation, the sectional constitutive model is adopted, therein considering axial‐force and bending‐moment coupling; moreover, the unscented Kalman filter is used for parameter estimation of the sectional model. The effectiveness of the sectional model updating with the unscented Kalman filter is validated via numerical analyses and actual hybrid tests on a full‐scale steel frame structure, with one column as the experimental substructure loaded by three actuators to guarantee the consistency of the boundary conditions. Copyright © 2016 John Wiley & Sons, Ltd.     

Hybrid formulation of operator splitting (OS) and Newmark‐β methods for collaborative structural analysis (CSA)

A collaborative structural analysis (CSA) system is developed, which is capable of performing highly sophisticated structural analyses utilizing beneficial features of existing individual structural analysis programs. In the system, the global equations of motion for the overall structural system are formulated in the host program. Some substructures, whose behaviors are relatively simple, are directly solved in the host program, whereas those having complex behavior are analyzed by the station programs. A time‐consuming static condensation procedure is needed for the substructures analyzed by the station programs if adopting an implicit integration scheme. The operator splitting (OS) method, which does not require tangential stiffness, can be used to improve the system efficiency. To this end, a hybrid formulation of the Newmark‐β and OS methods is proposed, and a CSA scheme based on the hybrid formulation is developed. In the CSA system adopting the hybrid formulation, the degrees of freedom whose tangential stiffness are unavailable are formulated by the OS method, whereas the rest are still formulated by the commonly used Newmark‐β method. Using the system, analyses of a three‐story‐braced steel moment‐resisting frame are conducted. In the analyses, the column bases are analyzed using the commercial finite element method software ABAQUS, and the remaining structural elements are analyzed using a frame analysis program called NETLYS. Results suggest that the hybrid formulation is very effective for the CSA system. Copyright © 2008 John Wiley & Sons, Ltd.