城市隔震高架桥梁地震反应的半主动控制

研究应用磁流变(MR)阻尼器对隔震连续梁桥邻联相对位移的半主动控制,并采用离线优化与在线自调整相结合进行模糊控制(FLC)。以邻联最大相对位移最小化为目标函数,对基本模糊控制器的隶属函数、量化因子、比例因子进行离线遗传优化;对优化后的模糊控制器的量化因子和比例因子进行在线自调整;数值仿真分析一多跨隔震连续梁桥的简化四自由度体系的半主动控制,比较不同控制方案的控制效果。结果表明,将MR阻尼器安装在上部结构与桥墩之间对桥梁邻联相对位移的控制效果优于将其安装在邻联之间;半主动控制能同时有效控制邻联最大相对位移与支座变形;与普通模糊控制以及仅采用遗传优化的模糊控制相比,具有在线自调整功能的模糊控制具有更好的控制效果和鲁棒性。     

Seismic response analysis of structures with velocity-dependent dampers

This paper is concerned with seismic response analysis of structures with velocity-dependent passive energy dissipation devices, such as viscous and viscoelastic dampers. The modeling of a damper-brace component composed of a viscous or viscoelastic damper connecting with braces in series is presented. Several key parameters influencing the energy dissipation efficiency of such dampers in the damper-brace component are investigated and the relationships of the parameters and efficiency of the dampers are established. An equivalent model for the passive energy dissipation system is developed, which can significantly simplify the dynamic analysis of structures with the velocity-dependent dampers. The seismic responses of a single-story structure and a multi-story structure with the viscous and viscoelastic dampers are analyzed to verify the effectiveness of the passive energy dissipation devices for suppression of dynamic responses of structures and the reliability of the proposed simplified computational methods.     

带铅阻尼器冷弯薄壁型钢组合墙抗震性能试验

锁铆或自攻螺钉连接的冷弯薄壁型钢组合墙在低周往复加载试验中,滞回曲线“捏拢”现象较为严重、耗能能力较差.为减轻地震作用下冷弯薄壁型钢组合墙的破坏,提高结构体系的耗能能力,提出了一种带有铅阻尼器的冷弯薄壁型钢组合墙结构体系,并基于冷弯薄壁型钢组合墙的角部连接方式、面板铆钉间距及种类3种变量对其进行抗震性能试验研究.试验结果表明:加入铅阻尼器后,基于锁铆或自攻螺钉连接的冷弯薄壁型钢组合墙结构体系在低周往复荷载作用下,变形能力和耗能能力均有大幅度提升,刚度退化趋于平缓,损伤指数有较明显的降低,破坏形态也得到优化,但屈服荷载及峰值荷载略有降低;其次减小铆钉间距后,组合墙的屈服荷载、峰值荷载、峰值位移、抗剪强度得到一定程度的提高,但能量耗散系数差别不大;同时基于锁铆连接的冷弯薄壁型钢组合墙的屈服位移、屈服荷载、峰值位移、峰值荷载也明显高于基于自攻螺钉连接的冷弯薄壁型钢组合墙,延性及能量耗散系数相差不大.     

基于主动控制优化被动黏滞阻尼器及混合隔震研究

针对隔震结构在超防烈度下隔震层位移响应过大问题,提出了基于主动控制算法优化被动粘滞阻尼器的策略。并将被动粘滞阻尼器安装于基础隔震结构形成被动混合控制结构,采用此被动混合控制能够基本实现主动混合控制的控制效果,实现以更加经济简便的方式解决隔震结构在超防烈度下隔震层位移响应过大问题。首先将主动控制装置设置于隔震层形成主动混合隔震控制体系,采用主动控制算法获取隔震层主动控制力与速度特性,其次,利用主动控制力与速度关系曲线,通过最小二乘法拟合被动粘滞阻尼器的最优阻尼系数与速度指数,最后将设计出的被动粘滞阻尼器安装于隔震层,形成被动混合隔震控制体系。以一栋七层基础隔震结构为受控模型,通过对主动混合隔震控制体系与被动混合隔震控制体系的仿真分析可知：主动混合隔震控制对隔震层位移的减震率分别为39.41%,45.04%及55.54%;被动混合隔震控制对隔震层位移的减震率分别为36.40%,44.30%及52.51%;被动混合隔震控制对于隔震层位移的减震率能够达到主动混合隔震控制效果的90%以上,被动混合隔震控制对于隔震层加速度响应的减震率能够达到主动混合隔震控制的60%以上,被动混合控制也同样实现了减小隔震层地震响应的同时不增加上部结构的响应,依据主动控制算法设计的被动粘滞阻尼器形成的被动混合控制结构能够基本实现主动控制的效果。说明依据主动控制设计被动粘滞阻尼器实现主动控制效果的思想的可行性。     

Rubber effect on metallic dampers used on the supports of steel cross members

There are many strengthening methods made with steel cross members for strengthening the structures with inadequate earthquake behavior. This type of strengthening methods is also effective in buckling of the cross members in the behavior of the structural frames. This buckling may cause partial or complete collapse of the structure. Thus, it is quite important to prevent and limit the formation of buckling in steel crosses. At the TEC 2018, the insulation unit is defined as the elements that can exhibit flexible behavior on the horizontal direction and rigid behavior on the vertical direction under the effect of earthquake loads. The basic principle of using insulation units is that these members can dissipate energy in the carrier system. The originality of this study is to experimentally investigate the damper behavior created by using cylindrical rubber wedges, which can be easily found in the automotive industry, in combination with steel plates and bolts. In this experimental study, the contribution of seismic insulators to the structural element to be strengthened was investigated. The insulators used in this study are considered by analogy with lead-core rubber insulators. As such seismic lead-core rubber insulators move under the influence of lateral loads, the lead core inside makes plastic deformation, thus increasing the damping rate. In this insulator study, it is aimed to use U plates or bolts instead of lead core. While vertical loads are covered by rubber support, horizontal loads will be damped due to plastic deformation of U plates or bolts. The five types of seismic dampers were used as 10 B-type rubber wedge mounted damper (SR), 2 U-type steel plates damper (SP), 10 M6 steel bolted damper (SB), 2 U-type steel plates and 10 B-type rubber wedge mounted damper (SPR), 10 M6 steel bolted, and 10 C-type rubber wedge mounted damper (SBR). These specimens were tested under lateral loading and constant vertical loading. The results obtained at the end of the tests shall be compared considering the strength, stiffness, and dissipated energy capacities of the specimens.     

Study on self‐adjustable variable pendulum tuned mass damper

Pendulum tuned mass damper (PTMD) is usually used to control the horizontal vibration of a tall building. However, traditional PTMD is highly sensitive to frequency deviation and difficult to adjust its frequency. In order to improve this problem of traditional PTMD and protect a tall building more effectively, a novel PTMD, called self‐adjustable variable pendulum tuned mass damper (SAVP‐TMD), is proposed in this paper. On the basis of the acceleration ratio between TMD and primary structure, the SAVP‐TMD can retune itself by varying the length of the pendulum according to the improved acceleration ratio‐based adjustment algorithm. PTMD and primary structural accelerations are obtained from two accelerometers respectively, and the acceleration ratio is calculated in a microcontroller, then, the stepper motor will adjust the pendulum under the guidance of the microcontroller under a specific harmonic excitation. The improved acceleration ratio‐based adjustment algorithm is proposed and compared to solve the nonconvergent retuning problem. The SAVP‐TMD can be regarded as a passive damper including a frequency adjustment device. A single‐degree‐of‐freedom structure model is used to verify the effectiveness of SAVP‐TMD through both experimental study and numerical simulation. In order to further verify the effect of SAVP‐TMD in the MDOF structure, a five‐storey structure coupled with an SAVP‐TMD is proposed as a case study. The results of experiment, simulation, and case study all show that SAVP‐TMD can retune itself to the primary structural dominant frequency robustly, and the retuned PTMD has a better vibration control effect than the mistuned one.     

Effect of gusset connection configurations on frame–gusset interaction in steel buckling‐restrained braced frame

Although buckling restrained braces (BRBs) are commonly applied in seismic buildings to mitigate structural damage, their performance was often limited by rupture of the corner gusset connections due to additional frame action. This issue may be resolved by alternative gusset connections to mitigate the frame–gusset interaction. In this study, commonly used procedures for design of the traditional gusset connection are reviewed, followed by a case study on the effect of frame action on the structural behavior of these gusset connections in steel frames with BRBs. Inspired by these analysis, two different strategies, aiming at releasing frame–gusset shear interaction using sliding gusset connection or reducing normal interaction using dual gusset plates, are tried to mitigate the frame action effects. Finite element analysis is conducted on steel frame subassemblages with/without BRBs to examine the effect of different gusset connections on the structural behavior of these framing systems. It shows that the sliding gusset connection shows beneficial effect in reducing the frame action, having much smaller stress responses on the gusset interfaces, as well as smaller shear force and plastic responses on the framing system. Thus, it becomes a promising gusset connection for improved seismic performance of the steel framing system with brace‐type dampers.     

Optimal placement of metallic dampers for seismic upgrading of multistory buildings based on a cost‐effectiveness criterion using genetic algorithm

In this paper, an optimal placement methodology for metallic dampers is proposed to upgrade the seismic performance of multistory buildings. Most previous studies on optimal damper placement (ODP) problems have been focused on minimizing the seismic responses, whereas the present study aims to utilize the minimum total cost of dampers to achieve a prescribed level of seismic response. To this end, the optimization objective is constructed based on a cost‐effectiveness criterion, and the optimization constraint is defined based on a desired level of seismic response. An improved integer‐coded genetic algorithm is presented for solving the ODP problem. A 16‐story shear building is illustrated to verify the proposed optimal placement methodology. It is shown that the proposed methodology can be used to achieve the predetermined performance level while minimizing the retrofitting cost. Moreover, different algorithms, objective functions, and levels of accuracy on the optimization are also compared. Finally, a two‐step optimization approach is proposed for achieving better placement schemes with less computational efforts.     

Seismic response of self‐centering precast concrete frames with hysteretic dampers

With the rapid development of cities and the invasion of major natural disasters such as earthquakes, the resilience city as a new design concept has been paid more and more attention. As an important branch of self‐centering seismic resisting system, self‐centering concrete frame system has been studied by many scholars. These studies prove that self‐centering concrete frame structure has excellent self‐centering ability but poor energy dissipation capacity. Adhering to the working principle of self‐centering structure and considering the development concepts of building industrialization and modularization, this paper proposed a kind of self‐centering precast concrete frame with hysteretic damper (SCPCHD). In order to verify its energy dissipation capacity and seismic performance, elaborate finite element models were established and elastoplastic dynamic time history analyses were carried out. The results showed that the SCPCHD frame has a similar interstory displacement response to the reinforced concrete (RC) frame and the energy dissipation performance of its joint is obviously superior to the RC frame under rare earthquake because the SCPCHD frame has low damage characteristics and excellent damping device. In summary, this paper proves the feasibility and superiority of the SCPCHD frame, providing reliable support for further research.     

Active tuned mass damper for damping of offshore wind turbine vibrations

An active tuned mass damper (ATMD) is employed for damping of tower vibrations of fixed offshore wind turbines, where the additional actuator force is controlled using feedback from the tower displacement and the relative velocity of the damper mass. An optimum tuning procedure equivalent to the tuning procedure of the passive tuned mass damper combined with a simple procedure for minimizing the control force is employed for determination of optimum damper parameters and feedback gain values. By time domain simulations conducted in an aeroelastic code, it is demonstrated that the ATMD can be used to further reduce the structural response of the wind turbine compared with the passive tuned mass damper and this without an increase in damper mass. A limiting factor of the design of the ATMD is the displacement of the damper mass, which for the ATMD, increases to compensate for the reduction in mass. Copyright © 2016 John Wiley & Sons, Ltd.