Seismic control of multi-degrees-of-freedom structures by vertical mass isolation method using MR dampers

Vertical mass isolation(VMI)is one of the novel methods for the seismic control of structures.In this method,the entire structure is assumed to consist of two mass and stiffness subsystems,and an isolated layer is located among them.In this study,the magnetorheological damper in three modes:passive-off,passive-on,and semi-active mode with variable voltage between zero and 9 volts was used as an isolated layer between two subsystems.Multi-degrees-of-freedom structures with 5,10,and 15 floors in two dimensions were examined under 11 pairs of near field earthquakes.On each level,the displacement of MR dampers was taken into account.The responses of maximum displacement,maximum inter-story drift,and maximum base shear in controlled and uncontrolled buildings were compared to assess the suggested approach for seismic control of the structures.According to the results,the semi-active control method can reduce the response by more than 12%compared to the uncontrolled mode in terms of maximum displacement of the mass subsystem of the structures.This method can reduce more than 16%and 20%of the responses compared to the uncontrolled mode in terms of maximum inter-story drift and base shear of the structure,respectively.

Control of seismic and operational vibrations of rotating machines using semi-active mounts

A dual isolation problem for rotating machines consists of isolation of housing structures from the machine vibrations and protection of machines during an earthquake to maintain their functionality. Desirable characteristics of machine mounts for the above two purposes can differ significantly due to difference in nature of the excitation and performance criteria in the two situations. In this paper, relevant response quantities are identified that may be used to quantify performance and simplified models of rotating machines are presented using which these relevant response quantities may be calculated. Using random vibration approach with a stationary excitation, it is shown that significant improvement in seismic performance is achievable by proper mount design. Results of shaking table experiments performed with a realistic setup using a centrifugal pump are presented. It is concluded that a solution to this dual isolation problem lies in a semi-active mount capable switching its properties from ‘operation-optimum’ to ‘seismic-optimum’ at the onset of a seismic event.

Seismic structural control using semi-active tuned mass dampers

This paper focuses on how to determine the instantaneous damping of the semi-active tuned mass damper (SATMD) with continuously variable damping.An off-and-towards-equilibrium (OTE) algorithm is employed to examine the control performance of the structure/SATMD system by considering the damping as an assumptive control action.The damping modification of the SATMD is carried out according to the proposed OTE algorithm,which is formulated based on analysis of the structural movement under external excitations,and the measured responses of the structure at every time instant. As examples two numerical simulations of a five-storey and a ten-storey shear structures with a SATMD on the roof are conducted.The effectiveness on vibration reduction of MDOF systems subjected to seismic excitations is discussed.Analysis results show that the behavior of the structure with a SATMD is significantly improved and the feasibility of applying the OTE algorithm to the structural control design of SATMD is also verified.

Damper placement for seismic control of super-long-span suspension bridges based on the first-order optimization method

To ensure the anti-earthquake performances of super-long-span suspension bridges, effective devices should be employed to control the seismic response of key sections. In this paper, four kinds of assessment functions for seismic response control effect are formulated based on the mechanism of seismic response control with dampers and the seismic response characteristics of long-span suspension bridges. A new optimal placement method of dampers using penalty function and first-order optimization theory is then proposed. Runyang suspension bridge (RSB) with a main span of 1490 m is then taken as an example. After seismic response time-history analyses on RSB using different placements of dampers, the analysis results are optimized by employing the optimal placement method and the optimal placements of dampers with the four assessment functions are then achieved respectively. Comparison of the four optimal control effects show that different assessment functions can lead to different optimal placements when the number of dampers is certain, but all placements of dampers can reduce the seismic response of RSB significantly. The selection of assessment functions and damper optimal placement should be determined by the structural characteristics and by what is considered in the structures. Results also show that the first-order optimization is an effective method on determining the optimal placement of dampers.

Recent progress and application on seismic isolation energy dissipation and control for structures in China

China is a country where 100% of the territory is located in a seismic zone. Most of the strong earthquakes are over prediction. Most fatalities are caused by structural collapse. Earthquakes not only cause severe damage to structures, but can also damage non-structural elements on and inside of facilities. This can halt city life, and disrupt hospitals, airports, bridges, power plants, and other infrastructure. Designers need to use new techniques to protect structures and facilities inside. Isolation, energy dissipation and, control systems are more and more widely used in recent years in China. Currently, there are nearly 6,500 structures with isolation and about 3,000 structures with passive energy dissipation or hybrid control in China. The mitigation techniques are applied to structures like residential buildings, large or complex structures, bridges, underwater tunnels, historical or cultural relic sites, and industrial facilities, and are used for retrofitting of existed structures. This paper introduces design rules and some new and innovative devices for seismic isolation, energy dissipation and hybrid control for civil and industrial structures. This paper also discusses the development trends for seismic resistance, seismic isolation, passive and active control techniques for the future in China and in the world.

Ground motion spatial variability effects on seismic response control of cable-stayed bridges

The spatial variability of input ground motion at supporting foundations plays a key role in the structural response of cable-stayed bridges （CSBs）; therefore, spatial variation effects should be included in the analysis and design of effective vibration control systems. The control of CSBs represents a challenging and unique problem, with many complexities in modeling, control design and implementation, since the control system should be designed not only to mitigate the dynamic component of the structural response but also to counteract the effects of the pseudo-static component of the response. The spatial variability effects on the feasibility and efficiency of seismic control systems for the vibration control of CSBs are investigated in this paper. The assumption of uniform earthquake motion along the entire bridge may result in quantitative and qualitative differences in seismic response as compared with those produced by uniform motion at all supports. A systematic comparison of passive and active system performance in reducing the structural responses is performed, focusing on the effect of the spatially varying earthquake ground motion on the seismic response of a benchmark CSB model with different control strategies, and demonstrates the importance of accounting for the spatial variability of excitations.

Seismic Response Control of Offshore Platform Structures with Shape Memory Alloy Dampers

In this study, the seismic response control of offshore platform structures with Shape Memory Alloy (SMA) dampers is investigated. A new SMA damper and its restoring force model are introduced for the calculation of seismic response reduction. Based on an actual platform structure and its mechanical model, the parameters which may affect the rate of shock absorption are analyzed, such as the number, position and characteristics of the SMA dampers and the condition of the site where the platform is located. The results show that the SMA damper is an effective control device for offshore platforms and satisfactory control can be achieved by proper selection of the parameters.

Seismic Data Quality Control and Interpolation Using Principal Component Analysis

Commonly, seismic data processing procedures, such as stacking and prestack migration, require the ability to detect bad traces/shots and restore or replace them by interpolation, particularly when the seismic observations are noisy or there are malfunctioned components in the recording system. However, currently available trace/shot interpolation methods in the spatial or Fourier domain must deal with requirements such as evenly sampled traces/shots, infinite bandwidth of the signals, and linear seismic events. In this paper, we present a novel method, termed the E-S (eigenspace seismic) method, using principal component analysis (PCA) of the seismic signal to address the issue of reliable detection or interpolation of bad traces/shots. The E-S method assumes the existence of a correlation between the observed seismic entities, such as trace or shot gathers, making it possible to estimate one of these entities from all others for interpolation or seismic quality control. It first transforms a trace (or shot) gather into an eigenspace using PCA. Then in the eigenspace, it treats every trace as a point with its loading scores of PCA as its coordinates. Simple linear, bilinear, or cubic spline 1 dimensional (1D) interpolation is used to determine PCA loading scores for any arbitrary coordinate in the eigenspace, which are then used to construct an interpolated trace for the desired position in physical space. This E-S method works with either regular or irregular sampling and, unlike various other published methods, it is well-suited for band-limited seismic records with curvilinear reflection events. We developed related algorithms and applied these to processed synthetic and offshore seismic survey data with or without simulated noises to demonstrate their performance. By comparing the interpolated and observed seismic traces, we find that the E-S method can effectively assess the quality of the trace, and restore poor quality data by interpolation. The successful processing of synthetic and real data using the E-S method presented in this approach will be widely applicable to seismic trace/shot interpolation and seismic quality control.

Study of Nonlinear Seismic Response and TMD Primary Control of the Cable-Stayed Bridge Section of the Third Macao-Taipa Bridge

The practical design of the cable-stayed bridge of the 3rd Macao-Taipa bridge is investigated by the finite element analysis program ANSYS, and 3-D elements BEAM188 and BEAM4 are adopted to create a dynamic calculation model. In order to analyze the material nonlinear seismic response of the cable-stayed bridge, the nonlinear behaviors of the ductile plastic hinges of the bridge towers are taken into account by employing the nonlinear rotational spring element COMBIN40. To simulate a major earthquake, three earthquake records were chosen using a wave-choosing program and input into the bridge structure along longitudinal and transversal directions. Comparisons of the linear and nonlinear seismic responses of the cable-stayed bridge are performed. In addition, a study of TMD primary control is carried out using element MASS21 and element COMBIN14, and it is indicated that the effects of mitigation monitoring are evident.

Seismic protection of frame structures via semi-active control:modeling and implementation issues

Theoretical and practical issues concerning the multi-faceted task of mitigating the latero-torsional seismic response of a prototypal frame structure with asymmetric mass distribution are approached, Chevron braces with embedded magnetorheological dampers acting on the interstory drift are used to ensure additional energy dissipation. The semi-active control strategy employed to govern the modification of the damper characteristics via feedback is based on the selection of optimal forces according to a H2/LQG criterion, with respect to which the actual forces are regulated by a clipped-optimal logic. A dynamic observer is used to estimate the state through a non-collocated placement of the acceleration sensors. Several aspects to be addressed throughout the complex process including the design, modelization, and implementation phases of semi-active protection systems are discussed. Finally, experimental results obtained to mitigate the motion induced by ground excitation in a large-scale laboratory prototype, simulating the seismic response of a two-story building, are summarized.

Seismic response control of a complex structure using multiple MR dampers: experimental investigation

This paper presents an experimental investigation on semi-active seismic response control of a multi- story building with a podium structure using multiple magnetorheological (MR) dampers manipulated by a logic control algorithm.The experiments are performed in three phases on a seismic simulator with a slender 12-story building model representing a multi-story building and a relatively stiff 3-story building model typifying a podium structure.The first phase of the investigation is to assess control performance of using three MR dampers to link the 3-story building to the 12-story building,in which seismic responses of the controlled two buildings are compared with those of the two buildings without any connection and with rigid connection.The second phase is to investigate reliability of the semi-active control system and robustness of the logic control algorithm when 2 out of 3 MR dampers fail and when the electricity supply to MR dampers is completely stopped.The last phase is to examine sensitivity of semi-active control performance of two buildings to change in ground excitation.The experimental results show that multiple MR dampers with the logic control algorithm can achieve a significant reduction in seismic responses of both buildings.The proposed semi-active control system is of high reliability and good robustness.

大跨度索穹顶结构半主动振动控制分析

为了实现大跨空间结构半主动振动控制,提出了一种基于模糊控制算法的半主动振动控制方法.以某体育馆大跨度索穹顶屋盖为分析对象,建立了基于台站与地震信息的地震动记录选择集,采用研发的新型压电摩擦阻尼器,开展索穹顶结构被动控制研究.将地面加速度和结构变形量2个指标作为控制参数,进行索穹顶结构半主动振动控制分析.结果表明:被动控制时不同地震动强度下结构峰值加速度、最大相对变形量的最小减振率平均值仅分别为3.7%和-1.6%;半主动控制下的压电摩擦阻尼器能够适应不同强度地震动,有效降低结构的峰值加速度和峰值位移,且峰值加速度减振率平均值为20.0%~41.9%,最大相对变形量减振率平均值为12.0%~19.0%.

附加不同形式调谐质量惯容系统的高耸烟囱轻量化减震控制

附加调谐质量阻尼器是烟囱结构的一种传统减震控制方法,然而其通常需要较大的附加质量及额外的安装空间,这为施工安装带来不便。本文提出附加调谐质量惯容系统(TMIS)控制高耸烟囱的地震响应,以利用惯容元件的表观质量效果实现轻量化减震目标。同时,考虑烟囱高阶模态对其地震响应不容忽视的影响,提出沿烟囱高度布置的分布式TMIS以实现多模态控制效果。建立了基于两种不同惯容子系统的TMIS力学模型及相应的附加分布式TMIS烟囱运动方程。以金井清谱为随机地震激励输入,并基于改进的定点理论提出了分布式TMIS的部分设计参数简化假设,提出了基于需求的分布式TMIS烟囱结构多模态优化设计方法。通过实例验证了所建议设计方法的有效性,并对比检验了分布式TMIS的轻量化及多模态控制效果,通过参数分析检验了所采用的改进定点理论简化的合理性。结果表明:所建议的设计方法可以按照预定目标发挥两种分布式TMIS的减震性能,两种分布式TMIS均显示了明显的轻量化减震效果。

The Ultimate Anti-Seismic Design Method

The design mechanisms and methods of the invention are intended to minimize problems related to the safety of structures in the event of natural phenomena such as earthquakes, tornadoes, and strong winds. It is achieved by controlling the deformations of the structure. Damage and deformation are closely related concepts since the control of deformations also controls the damage. The design method of applying artificial compression to the ends of all longitudinal reinforced concrete walls and, at the same time, connecting the ends of the walls to the ground using ground anchors placed at the depths of the boreholes, transfers the inertial stresses of the structure in the ground, which reacts as an external force in the structure’s response to seismic displacements. The wall with the artificial compression acquires dynamic, larger active cross-section and high axial and torsional stiffness, preventing all failures caused by inelastic deformation. By connecting the ends of all walls to the ground, we control the eigenfrequency of the structure and the ground during each seismic loading cycle, preventing inelastic displacements. At the same time, we ensure the strong bearing capacity of the foundation soil and the structure. By designing the walls correctly and placing them in proper locations, we prevent the torsional flexural buckling that occurs in asymmetrical floor plans, and metal and tall structures. Compression of the wall sections at the ends and their anchoring to the ground mitigates the transfer of deformations to the connection nodes, strengthens the wall section in terms of base shear force and shear stress of the sections, and increases the strength of the cross-sections to the tensile at the ends of the walls by introducing counteractive forces. The use of tendons within the ducts prevents longitudinal shear in the overlay concrete, while anchoring the walls to the foundation not only dissipates inertial forces to the ground but also prevents rotation of the walls, thus maintaining the structural integrity of the beams. The prestressing at the bilateral ends of the walls restores the structure to its original position even inelastic displacements by closing the opening of the developing cracks.

Robust H_∞ control for aseismic structures with uncertainties in model parameters

This paper presents a robust H∞ output feedback control approach for structural systems with uncertainties in model parameters by using available acceleration measurements and proposes conditions for the existence of such a robust output feedback controller. The uncertainties of structural stiffness, damping and mass parameters are assumed to be norm-bounded. The proposed control approach is formulated within the framework of linear matrix inequalities, for which existing convex optimization techniques, such as the LM1 toolbox in MATLAB, can be used effectively and conveniently. To illustrate the effectiveness of the proposed robust H∞ strategy, a six-story building was subjected both to the 1940 E1 Centro earthquake record and to a suddenly applied Kanai-Tajimi filtered white noise random excitation. The results show that the proposed robust H∞ controller provides satisfactory results with or without variation of the structural stiffness, damping and mass parameters.

积石山Ms6.2级和泸定Ms6.8级地震地质灾害发育规律对比

2023年积石山Ms6.2级地震是继2022年泸定Ms6.8级地震后在青藏高原东缘—东北缘地区发生的又一次强震事件。2次地震均诱发大量地震地质灾害,但由于发震断层类型、地质和地貌等条件的差异,2次地震地质灾害发育分布规律呈现显著的差异性。为揭示不同震区地震地质灾害发育规律,本研究采用地面调查、遥感解译和空间叠加统计等方法,对比分析了积石山和泸定地震地质灾害发育分布特征和控灾因子。结果表明:断层类型控制了同震地质灾害的发育优势坡向和垂向空间展布,即“背向坡效应”和“上下盘效应”;地貌条件是影响同震地质空间分布的主要因子,即川西高山峡谷地貌中“线状”分布和陇西黄土地貌中“面状”分布;特殊土体类型、气候、植被覆盖等差异性是同震地质灾害调查与应急处置中需要重点关注的因子。本次研究可为不同断层类型和不同地貌区同震地质灾害重点防范区范围划定、趋势预测和灾后重建提供科学参考。

Velocity adjustable TMD and numerical simulation of seismic performance

A new type of velocity adjustable tuned mass damper （TMD） consisting of impulse generators and clutches is presented. The force impulse is generated by a joining operation of electromagnets and springs and MR dampers are used as clutches. Rules for velocity adjustment are established according to the working mechanism of TMD. The analysis program is developed on a VB platform. Seismic response of SDOF structures with both passive TMD and velocity adjustable TMD are analyzed. The results show that （l） the control effectiveness of passive TMDs is usually unstable; （2） the control effectiveness of the proposed semi-active TMDs is much better than passive TMDs under typical seismic ground motions; and （3） unlike the passive TMD system, the proposed velocity adjustable TMDs exhibit good control effectiveness even when the primary structure performance becomes inelastic during severe earthquakes.

连体高层大跨钢连廊设计关键技术分析

以实际工程项目为背景,针对多塔连体高层大跨钢连廊设计中存在的关键技术问题,对多塔弱连接体结构进行了整体弹性和弹塑性分析,研究了大跨钢连廊对塔楼受力和抗震性能的影响以及连廊自身振动特性和振动控制方案。结果表明,采用弱连接方案来降低大跨钢连廊对各塔楼的影响是合理可行的解决方案;对与连廊采用滑动支座连接一端的塔楼,其独立塔楼和整体模型的动力特性和地震响应基本一致,塔楼可按独立塔楼模型计算结果进行设计;对与连廊采用固定铰支座连接一端的塔楼,其独立塔楼和整体模型的动力特征和地震响应有较大差异,应考虑连廊对抗震性能的影响,按整体模型和独立塔楼模型计算结果进行包络设计;连廊支座布置方案和选取的抗震支座实现了预期弱连接设计理念,满足大震下变形需求;采用TMD减振控制的大跨钢连廊在人群荷载激励下的竖向振动加速度响应减小显著,减振率达到70%,减振后竖向振动加速度满足规范要求。

被动陆缘深水海底限制性水道三维地震表征及沉积演化——以纳米贝盆地为例

【目的】被动陆缘盆地深水浊积砂体已成为深海油气勘探突破及储量发现的新领域。【方法】以典型被动陆缘纳米贝盆地深水高分辨率三维地震资料为研究基础,以受构造活动和沉积压实影响较小而保持原始水道沉积构型的海底第四纪沉积地层为目标,精细描述和解析了目标层内限制性水道沉积的剖面和平面地震响应特征。【结果与结论】限制性浊积水道侵蚀作用总体大于沉积作用,单一水道的沉积模式以凹岸侵蚀、凸岸“S”型加积为主,该过程使“V”型河谷展宽并充填形成“U”型水道沉积;多期叠置水道沉积体系分为侧切叠置和垂切叠置的两种模式,以侧切叠置模式为主;窄陆架、宽缓陆坡的海底地形控制限制性水道的延伸方向及长度规模,陆缘盆地的沉降中心控制着各期水道的迁移方向,古气候事件发生频率控制着水道体系内部浊积砂体发育的期次。该研究成果能够给予限制性水道沉积构型认识及砂体储层预测启发。

常规岛汽机旁路调节阀抗震性能研究

为防止常规岛汽机旁路调节阀在地震期间发生共振,致使调节阀与连接管道受到破坏,使用ANSYS软件中Modal模块,对DN 300 Class900汽机旁路调节阀进行模态分析,得到调节阀各阶自振频率。当调节阀的基频高于33 Hz时,使用等效静力法。对调节阀进行抗震分析,得到阀门整体及各部件的等效应力和变形。根据ASME BPVC-Ⅲ中对核级设备抗震的规定,对调节阀在承受地震载荷时的应力强度进行评定,结果表明:阀体、阀盖、阀杆、支架最大应力分别为133.63、77.52、29.46、71.54 MPa,中法兰螺栓最大拉应力为183.23 MPa,最大剪应力为15.36 MPa,均满足抗震强度要求。