Damping characteristics of friction damped braced frame and its effectiveness in the mega-sub controlled structure system

Based on energy dissipation and structural control principle, a new structural configuration, called the megasub controlled structure （MSCS） with friction damped braces （FDBs）, is first presented. Meanwhile, to calculate the damping coefficient in the slipping state a new analytical method is proposed. The damping characteristics of one-storey friction damped braced frame （FDBF） are investigated, and the influence of the structural parameters on the energy dissipation and the practical engineering design are discussed. The nonlinear dynamic equations and the analytical model of the MSCS with FDBs are established. Three building structures with different structural configurations, which were designed with reference to the conventional mega-sub structures such as used in Tokyo City Hall, are comparatively investigated. The results illustrate that the structure presented in the paper has excellent dynamic properties and satisfactory control effectiveness.

Effect of Low Content Chlorophyll on Distribution Properties of Absorbed Light Energy in Leaves of Mutant Rice

This paper reported the diurnal variations of photochemical efficiency of PSII, thermaldissipation rate and other physiology process in the low content chlorophyll mutant rice andits wild type under field conditions, and analyzed the difference of absorbed light distributionbetween the two rice varieties in a day. The results showed that the mutant had poor absorbedlight because of its little light absorption coefficient, but higher electron transportg ratecould partly reduce the disadvantageous effect of deficient absorbed light in mutant. Comparedwith wild-type rice, the mutant had less excess excitation energy and the fraction of absorbedlight allocated to photochemical process was more.

Decentralization of a Multi Data Source Distributed Processing System Using a Distributed Hash Table

A distributed processing system (DPS) contains many autonomous nodes, which contribute their own computing power. DPS is considered a unified logical structure, operating in a distributed manner;the processing tasks are divided into fragments and assigned to various nodes for processing. That type of operation requires and involves a great deal of communication. We propose to use the decentralized approach, based on a distributed hash table, to reduce the communication overhead and remove the server unit, thus avoiding having a single point of failure in the system. This paper proposes a mathematical model and algorithms that are implemented in a dedicated experimental system. Using the decentralized approach, this study demonstrates the efficient operation of a decentralized system which results in a reduced energy emission.

Numerical Solutions of the Improved Boussinesq Equation with Stokes Damping

In this paper, we propose new finite volume element schemes to numerically solve the improved Boussinesq equation with Stokes damping. The new schemes can inherit characteristic properties of the conservation of mass and the decrease of total energy from the improved Boussinesq equation with Stokes damping. Numerical experiments illustrate that the proposed schemes are second-order accuracy in space and time.

A Review on Methods for Determining the Vibratory Damping Ratio

This article aims to popularize the methods for determining the vibratory damping ratio, to explain the various mathematical and physical theorems related to the establishment of literal expressions. Vibration damping is an essential parameter to reduce the dynamic responses of structures. The study aimed at its determination is necessary and essential for the safeguard of buildings and human lives during the earthquake. Among the main methods studied in this article, the free vibration attenuation method seems to be easy to implement but requires a state-of-the-art device to capture the responses. In addition to this device, the other methods require other equipment for the vibration of the system and the transformation of the responses in the frequency domain.

Dynamic characteristics of a novel damped outrigger system

This paper presents exact analytical solutions for a novel damped outrigger system, in which viscous dampers are vertically installed between perimeter columns and the core of a high-rise building. An improved analytical model is developed by modeling the effect of the damped outrigger as a general rotational spring acting on a Bernoulli-Euler beam. The equivalent rotational spring stiffness incorporating the combined effects of dampers and axial stiffness of perimeter columns is derived. The dynamic stiffness method(DSM) is applied to formulate the governing equation of the damped outrigger system. The accuracy and effi ciency are verifi ed in comparison with those obtained from compatibility equations and boundary equations. Parametric analysis of three non-dimensional factors is conducted to evaluate the infl uences of various factors, such as the stiffness ratio of the core to the beam, position of the damped outrigger, and the installed damping coeffi cient. Results show that the modal damping ratio is signifi cantly infl uenced by the stiffness ratio of the core to the column, and is more sensitive to damping than the position of the damped outrigger. The proposed analytical model in combination with DSM can be extended to the study of structures with more outriggers.

Experimental Study on Suspended Sediment Concentration and Its Vertical Distribution under Spilling Breaking Wave Actions in Silty Coast

In this paper, flume experiments are focused on sediment transport inside and outside the surf zone. According to the energy dissipation balance principle of sediment-laden flow and the similarity between energy dissipation of spilling breaking wave and hydraulic jump, formulas are proposed to predict time averaged suspended sediment concentration under both non-breaking and breaking waves. Assuming that the sediment diffusion coefficient, which is related with energy dissipation, is proportional to water depth, formulas are proposed to predict close-to-bed suspended sediment concentration and vertical distribution of suspended sediment under spilling breaking waves, and the prediction shows a good agreement with the measurement.

Numerical Investigation of Constructal Distributors with Different Configurations

Seven distributors with different configurations are designed and optimized by constructal approach. Their flow distribution performance and energy dissipation are investigated and compared by computational fluid dynamics （CFD） simulation. The reliability of CFD simulation is verified by experiments on the distributor that has all distributing rectangle channels on a plate. The results show that the symmetry of the distributing channels has decisive influence on the performance of flow distribution. Increasing the generations of channel branching will improve the flow distribution uniformity, but on the other hand increase the energy dissipation. Among all the seven constructal distributors, the distributor that has dichotomy configuration, Y-type junctions and straight interconnecting channels, is recommended for its better flow distribution performance and less energy dissipation.

A Clustering-tree Topology Control Based on the Energy Forecast for Heterogeneous Wireless Sensor Networks

How to design an energy-efficient algorithm to maximize the network lifetime in complicated scenarios is a critical problem for heterogeneous wireless sensor networks (HWSN). In this paper, a clustering-tree topology control algorithm based on the energy forecast (CTEF) is proposed for saving energy and ensuring network load balancing, while considering the link quality, packet loss rate, etc. In CTEF, the average energy of the network is accurately predicted per round (the lifetime of the network is denoted by rounds) in terms of the difference between the ideal and actual average residual energy using central limit theorem and normal distribution mechanism, simultaneously. On this basis, cluster heads are selected by cost function (including the energy, link quality and packet loss rate) and their distance. The non-cluster heads are determined to join the cluster through the energy, distance and link quality. Furthermore, several non-cluster heads in each cluster are chosen as the relay nodes for transmitting data through multi-hop communication to decrease the load of each cluster-head and prolong the lifetime of the network. The simulation results show the efficiency of CTEF. Compared with low-energy adaptive clustering hierarchy (LEACH), energy dissipation forecast and clustering management (EDFCM) and efficient and dynamic clustering scheme (EDCS) protocols, CTEF has longer network lifetime and receives more data packets at base station. © 2014 Chinese Association of Automation.

Dry friction damping mechanism of flexible microporous metal rubber based on cell group energy dissipation mechanism

Flexible microporous metal rubber (FMP-MR) is a high-damping material that dissipates energy by dry friction through internal spiral metal wires in contact with each other. However, the FMP-MR energy dissipation mechanism is not fully understood owing to its disordered grid interpenetrating structure. In this work, computer-aided preparation technology is used to accurately reconstruct the complex spiral network structure of FMP-MR multipoint random contact, and a cell group model with an energy dissipation mechanism is proposed to obtain the dynamic energy distribution of the contact friction in both space and time dimensions. By judging the effective contact point, a global displacement ablation phenomenon of hooked staggered porous materials is induced. The macro- and micro-equivalent frictions are introduced to effectively explain the characteristics of the strong energy dissipation in FMP-MR under fretting excitation. A real and effective damping hysteresis constitutive model is then constructed to dynamically capture the mapping relationship between the complex nonlinear topological structure effect of the materials and spatial random contact dry friction in real time. The results indicate that the contact behavior between turns of the FMP-MR wire follows a clear quasi-Gaussian distribution under an external load, forcing the topological results to change. The energy dissipation of the materials revealed peak energy consumption lagging behind the loading limit for a certain distance, which can be determined by the effective contact point and contact dry friction slip. The consistency between the quasi-static compression tests and constitutive curves of the model was quantitatively verified through residual analysis. The data demonstrated the differential behavior of the FMP-MR meso-structure to follow a phased growth law during loading with different action mechanisms in the guiding, main growth, and relaxation stages of the energy consumption displacement curve. In summary, these findings provide an acceptable theoretical basis for the damping energy consumption mechanism and lifetime prediction of FMP-MR.

Studies on Mooring Energy Based on Finite Element Method

To understand the mooring energy during Fositioning, the expressions of four items concerning mooring line energy are presented based on a finite element model, including gravitational and elastic potential energy, kinetic energy and dissipated energy due to mooting-induced damping. In a static case, the force calculated from the derivative of potential energy with respect to distance is compared with that of direct calculation. The results are tbund fit well, which indicates the law of conservation of energy and also shows the correctness of the potential energy results. For the cases of a single mooring line with the attaclunent point oscillating with different amplitudes in horizontal or vertical direction （corresponding to surge and roll motions respectively）, and the case of the mooring line with a horizontal bicbromatic oscillation on the attachment point, the time history of the first three items are calculated and analyzed, also, the indicator diagram tbr mooring-induced damping are given. These results reveal the energy state of the mooring line and can provide a better understanding of how the mooring line works.

RC Frame-Prefabricated HPFRCC Energy Wall Structure System Energy Distribution Research

The weak layer of steel concrete (RC) frame structure is easy to destroy under the action of the earthquake, the damage mechanism is more difficult to control. Severe damage to the building structure after the earthquake, resulting in too high repair costs or having to dismantle and rebuild. In order to improve and enhance the anti-seismic performance of the RC framework structure, energy consumption devices are added between the frame columns to achieve the effect of reducing the RC frame structure damage and improving the seismic performance of the RC frame structure. In this article, high-performance fiber-enhanced cement base composite materials fabricated energy consumption walls are prepared in the RC frame structure to form a new type of seismic structure system of RC frame-prefabricated HPFRCC energy consumption wall. This article uses the power timing analysis of the ABAQUS finite element software to study the anti-seismic performance, influencing factors and energy consumption distribution of the RC frame-prefabricated HPFRCC energy wall structural system.

Calculation of multi-layer plate damper under one-axial load

A multi-layer damper with waved plates under one-axial load is considered. A method of theoretical calculation of its energy dissipation coefficient is proposed. An experimental research of own frequencies and vibration transfer ratios for different parameters of damper structure, harmonic vibration load and random load is performed. Results of this research are approximated by functions; it is possible to use these functions for the calculation of the damper too.

新型全域屈服固接耗能钢棒阻尼器数值模拟及分析

为改善现有金属阻尼器受力不均、延展性小、震后难以更换等问题,提出一种新型全域屈服耗能钢棒阻尼器,用于提高建筑结构的抗震性能。阻尼器采用耗能钢棒作为耗能元件,耗能钢棒经过截面设计后能实现全截面同时屈服,且方便震后更换。通过有限元数值模拟表明全域屈服耗能钢棒阻尼器滞回曲线饱满,耗能能力强,验证了全域耗能钢棒阻尼器设计合理性,可有效提升钢棒的耗能能力和延性性能,最后探究了钢棒半径、数量、长度对阻尼器力学性能的影响。分析结果表明:耗能钢棒能实现全截面屈服,滞回曲线饱满,性能稳定优越。耗能钢棒半径、长度、数量对阻尼器性能影响显著。阻尼器的耗能性能与钢棒半径、数量成正比,与钢棒长度成反比。

三星堆古蜀文化遗址博物馆结构设计与减震分析

三星堆古蜀文化遗址博物馆采用钢框架结构,展厅区域屋面采用组合网架结构,结构平、立面及空间关系较为复杂。为改善结构抗震性能,达到预期的抗震性能目标,本项目进行了消能减震设计,设置了屈曲约束支撑及黏滞阻尼器。简要介绍了该项目的结构体系及设计重难点,并重点论述了该项目结构减震设计思路,对各水准地震作用下结构附加有效阻尼比与能量耗散情况、减震结构与非减震结构的地震响应,罕遇地震下结构弹塑性损伤情况等进行考察。结果表明:罕遇地震作用下,减震结构的楼层剪力、层间位移角等结构整体指标明显减小,屈曲约束支撑及黏滞阻尼器滞回曲线饱满,耗散了较多地震能量,结构的抗震性能与安全储备得到提高,达到了预期的减震设计目标与抗震性能目标。

采用粘滞阻尼器的某超高层建筑消能减震设计与分析

以珠海市某框架–核心筒建筑为例,运用分析程序ETABS建立有限元模型,并设置多组粘滞阻尼器布置方案,采用最大层间位移角与基底剪力双关键指标,对比各方案减震效果并择优选出布置方案。对所得方案进行多遇地震下弹性分析及罕遇地震下动力弹塑性分析。多遇地震分析结果表明,采用粘滞阻尼器的结构双向指标均大幅降低,提供附加阻尼比达4.1%。罕遇地震分析结果表明,结构的层间位移角及整体屈服机制均满足要求。该方案下减震效果与结构抗震性能均良好,可为同类工程提供参考。

基于VMD-HHT的井下预裂爆破振动效应分析

云南玉溪大红山铜矿现有采矿方法为分段空场嗣后充填法,采用大爆破工艺,由于一次爆破的药量过大导致对保留岩体的损伤较大,影响采场的稳定性。为解决此问题,按照多打孔少装药的原则,在距保留岩体一定距离处布置一排较为密集的炮孔,并减小单孔装药量,在主爆区起爆之前先起爆该排炮孔,形成一条具有一定宽度的缝隙,以减弱对保留岩体的损伤。基于变分模态分解和希尔伯特黄变换(VMDHHT)方法对现场实测的爆破振动信号进行分析。结果表明:本次预裂爆破振动信号的瞬时能量分布区间主要集中在0~0.5 s内,频率分布的区间主要集中在40 Hz以内;采用3个测点的合速度进行减振率计算,得到3个测点减振率分别为21.0%、30.1%和38.5%,有效减小了爆破振动对保留岩体的损伤和破坏。

铰接阻尼支吊架设计与分析

为了防止管道结构在地震工况下的破坏,在传统抗震支吊架基础上,将U型软钢阻尼器加入其中,提出了一种铰接阻尼支吊架。以目前常用的消防管道为例,利用ANSYS软件建立数值模型,对设置铰接阻尼支吊架的结构进行了力学分析,并与传统抗震支吊架减振效果进行了对比,结果表明:铰接阻尼支吊架刚度小,受力更加均匀。随着地震烈度的提高,铰接阻尼支吊架对管道的位移和加速度的减振效果明显优于传统抗震支吊架,其中,抗震设防烈度为7和8度时,位移和加速度减振率均可以达到40%以上。从提出的滞回曲线可以看出,铰接阻尼支吊架耗能能力优良。

三星堆古蜀文化遗址博物馆大型螺旋坡道结构减震设计与舒适度分析

三星堆古蜀文化遗址博物馆中庭的螺旋坡道采用钢箱梁结构体系,其最大半径为28.7m,水平投影长度为118.5m,宽度为4.5~14.5m。介绍了螺旋坡道结构减震(振)设计过程,通过设置黏滞阻尼器和调谐质量阻尼器减小坡道在地震作用和人行激励作用下的结构响应,采用MIDAS Gen和ANSYS软件建立多尺度整体模型考虑螺旋坡道和主体结构的相互作用,进行了地震作用时程分析和人行激励舒适度分析。结果表明,各水准地震下黏滞阻尼器对螺旋坡道水平加速度减震效率约为45%~50%,水平位移的减震效率约为55%~70%。设置调谐质量阻尼器对螺旋坡道竖向振动加速度减振效率约为55%~60%,有效减小了坡道在人行激励作用下的结构响应。

基于时程分析方法的黏滞阻尼减震结构附加阻尼比计算研究

附设黏滞阻尼器后结构的附加阻尼比是进行减震结构设计的关键。基于目前计算附加阻尼比时应用得十分广泛的时程分析方法进行研究,首先从基本理论出发,分析基于特征向量法的快速非线性分析(FNA)方法、Ritz向量法的FNA方法、直接积分方法以及与3种计算方法对应的能量比法在附加阻尼比计算时所面临的主要问题及重要参数设置;然后通过一单自由度体系的振动台试验测试结果与各种计算方法的数值模拟结果进行对比分析,得到较为适合的附加阻尼比计算方法;最后将研究成果应用于实际工程结构,进一步验证所推荐方法和参数设置的正确合理性。研究旨在为今后广大一线减震设计工程师计算较为真实的附加阻尼比提供重要参考。