Aseismic performances of constrained damping lining structures made of rubber-sand-concrete

Flexible damping technology considering aseismic materials and aseismic structures seems be a good solution for engineering structures.In this study,a constrained damping structure for underground tunnel lining,using a rubber-sand-concrete(RSC)as the aseismic material,is proposed.The aseismic performances of constrained damping structure were investigated by a series of hammer impact tests.The damping layer thickness and shape effects on the aseismic performance such as effective duration and acceleration amplitude of time-domain analysis,composite loss factor and damping ratio of the transfer function analysis,and total vibration level of octave spectrum analysis were discussed.The hammer impact tests revealed that the relationship between the aseismic performance and damping layer thickness was not linear,and that the hollow damping layer had a better aseismic performance than the flat damping layer one.The aseismic performances of constrained damping structure under different seismicity magnitudes and geological conditions were investigated.The effects of the peak ground acceleration(PGA)and tunnel overburden depth on the aseismic performances such as the maximum principal stress and equivalent plastic strain(PEEQ)were discussed.The numerical results show the constrained damping structure proposed in this paper has a good aseismic performance,with PGA in the range(0.2-1.2)g and tunnel overburden depth in the range of 0-300 m.

COMPARISON OF VIBRATION PERFORMANCE OF A SANDWICH CLAMPED-CLAMPED BEAM WITH MAGNETS VERSUS CONVENTIONAL CONSTRAINED DAMPING TREATMENTS

This paper investigates how the magnetic constrained layer damping (MCLD) treat- ment suppresses the displacement and acceleration resonant peak of a clamped-clamped beam. Because MCLD treatment reduces input work and gives more dissipation energy, the vibration from external excitation can be e?ectively suppressed.The vibration reduction e?ects of MCLD and other conventional constrained damping treatments are also evaluated. In many cases, using MCLD treatments can yield smaller displacement and acceleration resonant peak especially in mode 1 compared to the other treatments without greatly changing the natural frequencies of the base beam.

Importance Measure Analysis for Use in Dynamic Performance Design of a Co-cured Composite Damping Instrument Panel

For the best dynamic performance of a co-cured composite damping instrument panel with light weight and high strength, a multilayer sandwich structure with polymethaerylimide （PMI） foam combined with embedded and co-cured composite damping structure is proposed. The struetue can maintain the excellent mechanical properties of composite materials, and achieve the damping and light effect at the same time. Input variables which may affect the dynamic performance of the instrument panel were selected and variance based importance measure was analyzed through multi- finite element method （FEM） analysis. Using the results of the importance measure analysis, with other design requirements, the important design variable was optimized and an instrument panel with the best dynamic performance under the requirements of light weight and high strength was obtained. The structure of the instrument panel can provide reference for the design of precision, high speed, and dynamic composite component. The importance measure analysis of dynamic performance of the instrument panel can provide a reference for relative design.

SEMI-ACTIVE CONTROL OF VEHICLE SUSPENSION WITH MAGNETO-RHEOLOGICAL DAMPERS PARTⅡ——EVALUATION OF SUSPENSION PERFORMANCE

The design and analysis of an intelligent vehicle suspension with MR dampers should address hybrid semi-active control goals, such as rejection of current-switching discontinuity and MR-damper hysteresis, asymmetric damping from the symmetric MR-damper design, robustness on the vehicle operation parameter uncertainties and consideration of essential multiple suspension goals. Following the proposed skyhook-based asymmetric semi-active controller （Part I ） for achieving the above goals, herein, a set of suspension performance measures and three kinds of varying amplitude harmonic, rounded pulse and really measured random excitations are systematically defined, and the sensitivity of quarter-vehicle MR-suspension performance to variations in operating conditions is thoroughly analyzed. The results illustrate that the proposed skyhook-based semi-active MR-suspension in the asymmetric mode yields relatively superior dynamic responses to meet the multiple suspension performances of ride, rattle space, road-holding and dynamic tire force transmitted to the pavement, and has desirable robustness on variations in operating conditions of vehicle load and speed and the road roughness.

Numerical Modeling on Hydrodynamic Performance of A Bottom-Hinged Flap Wave Energy Converter

The hydrodynamic performance of a bottom-hinged flap wave energy converter （WEC） is investigated through a frequency domain numerical model. The numerical model is verified through a two-dimensional analytic solution, as well as the qualitative analysis on the dynamic response of avibrating system. The concept of ＂optimum density＂ of the bottom-hinged flap is proposed, and its analytic expression is derived as well. The frequency interval in which the optimum density exists is also obtained. The analytic expression of the optimum linear damping coefficient is obtained by a bottom-hinged WEC. Some basic dynamic properties involving natural period, excitation moment, pitch amplitude, and optimum damping coefficient are analyzed and discussed in detail. In addition, this paper highlights the analysis of effects on the conversion performance of the device exerted by some important parameters. The results indicate that ＂the optimum linear damping period of 5.0 s＂ is the most ideal option in the short wave sea states with the wave period below 6.0 s. Shallow water depth, large flap thickness and low flap density are advised in the practical design of the device in short wave sea states in order to maximize power capture. In the sea state with water depth of 5.0 m and wave period of 5.0 s, the results of parametric optimization suggest a flap with the width of 8.0 m, thickness of 1.6 m, and with the density as little as possible when the optimum power take-off （PTO） damping coefficient is adopted.

Adaptive base-isolation of civil structures using variable amplification

Semi-active dampers are used in base-isolation to reduce the seismic response of civil engineering structures. In the present study, a new semi-active damping system using variable amplification will be investigated for adaptive baseisolation. It uses a novel variable amplification device （VAD） connected in series with a passive damper. The VAD is capable of producing multiple amplification factors, each corresponding to a different amplification state. Forces from the damper are amplified to the structure according to the current amplification state, which is selected via a semi-active control algorithm specifically tailored to the system＇s tmique damping characteristics. To demonstrate the effectiveness of the VAD-damper system for adaptive base-isolation, numerical simulations are conducted for three and seven-story base-isolated buildings subject to both far and near-field ground motions. The results indicate that the system can achieve significant reductions in response compared to the base-isolated buildings with no damper. The proposed system is also found to perform well compared to a typical semi-active damper.

Comparison of the vibration isolation performance of a seat suspension with various design modes

Three design modes of seat suspension,i.e.,negative stiffness elements(NSEs),damping elements(DEs),and negative stiffness-damping elements(NSDEs),are proposed to evaluate the ride performance of a vehicle.Based on a dynamic model of a seat suspension and indexes of the root mean square deformation and acceleration of the seat suspension(x RMS)and driver s seat(a RMS),the influence of the design parameters of the NSEs,DEs,and NSDEs on the driver s ride comfort is evaluated.A genetic algorithm is then applied to optimize the parameters of the NSEs,DEs,and NSDEs.The study results indicate that the design parameters of the NSEs and NSDEs remarkably influence x RMS and a RMS,whereas those of the DEs insignificantly influence x RMS and a RMS.Based on the optimal results of the NSEs,DEs,and NSDEs,the damping force of the DEs is 98.3%lower than the restoring force of the NSEs.Therefore,the DEs are ineffective in decreasing x RMS and a RMS.Conversely,the NSEs combined with the damping coefficient of the seat suspension strongly reduce x RMS and a RMS.Consequently,the NSEs can be added to the seat suspension,and the damping coefficient of the seat suspension can also be optimized or controlled to further enhance the vehicle s ride performance.

水性环氧树脂-聚丙烯纤维改性水泥基快速修补砂浆性能研究

为改善机场道面修补砂浆脆性大和粘结性能差等问题,本文利用水性环氧树脂(WER)、聚丙烯(PP)纤维和硫铝酸盐水泥(SAC)制备出一种快速修补砂浆,并对其工作性能、力学性能、阻尼性能和耐硫酸盐腐蚀性能进行研究。结果表明,PP纤维和WER可显著提高快速修补砂浆韧性和粘结性能,使得快速修补砂浆2 h抗压、抗折强度和粘结强度分别达到22.3,5.1和3.7MPa,满足民用机场规范要求,同时可改善快速修补砂浆的阻尼性能和抗硫酸盐侵蚀性能。

钢管混凝土双块式轨枕无砟轨道结构疲劳性能试验研究

新型钢管混凝土(CFT)双块式轨枕克服了桁架钢筋双块式轨枕存在的生产制造复杂、存放易锈蚀、运营阶段易开裂等问题,可广泛应用于高速铁路和城市轨道交通无砟轨道结构。为检验CFT双块式轨枕无砟轨道结构的疲劳性能,采用11根预制CFT双块式轨枕现浇制作足尺无砟轨道结构节段模型,开展橡胶隔振垫式减振轨道和现浇整体式轨道节段的疲劳试验,揭示其疲劳损伤特性,分析典型疲劳加载循环次数后静载作用下轨道结构应变和变形分布及其演化规律。研究结果表明:1.5倍静轴重的疲劳荷载累计作用500万次后,减振节段及整浇节段CFT双块式轨枕无砟轨道结构混凝土均未出现肉眼可见的裂缝,轨枕与现浇道床整体工作性能良好,疲劳性能满足规范要求;停机开展静载试验过程中轨道结构各测点混凝土横向应变值随荷载增大而近似线性增大,最大拉压应变值均远小于混凝土的极限应变值,工作状态良好;轨道整浇节段道床板中处于整体受拉的状态,可见设置层间连接钢筋实现了道床与底座的共同工作;疲劳试验过程中轨道结构测点竖向位移值总体随着静载的增大而逐渐增大,位移量级较小,满足规范要求,减振轨道节段竖向位移值及其变化率大于整浇轨道节段。研究结果可供类似研究及钢管混凝土双块式轨枕无砟轨道结构工程应用参考。

反向消磁条件下磁流变脂隔震模拟试验研究

采用电磁线圈及永磁体共同控制磁场,自主设计一种可反向消磁的磁流变脂(MRG)剪切试验装置。利用ANSYS Electronics软件对该试验装置磁场分布进行仿真分析,并制备不同羰基铁粉质量分数的MRG,采用振动台对反向消磁条件下MRG的动态剪切性能开展试验测试,分别研究励磁电流、激振幅值和激励频率对MRG动态性能的影响。结果表明:羰基铁粉质量分数对MRG的动态性能影响显著;MRG的剪切应力随励磁电流的增大先快速增大后趋于平缓,阻尼力则逐渐减小;MRG的耗能能力随位移幅值的增加而增强;随着加载频率的增大,其阻尼力略有增加。

山岭隧道衬砌-减震层体系动力响应研究

为了探寻隧道设置减震层时影响减震层减震性能的关键因素,建立了设置减震层的隧道有限元数值模型,将数值模型与振动台试验进行对比,验证了数值模型的可靠性。改变减震层设计参数和围岩条件,通过对隧道结构的主应变、相对变形率以及围岩的塑性区进行分析,研究不同参数条件下减震层的减震效果。结果表明:设置减震层后隧道加速度响应的传递函数在15~30 Hz频段范围内减小,说明减震层通过吸收地震波中的高频成分,减小地震波能量向隧道的传递,进而减小隧道的地震响应。参数分析结果表明:减震层弹性模量越小厚度越大,减震层的减震效果越加明显,但隧道结构的相对变形率也随之上升。相比于增加减震层厚度,降低减震层弹性模量对减震效果的提升更为显著。在坚硬围岩中的设置减震层相比于软弱围岩减震效果更显著。

自复位复合阻尼耗能支撑滞回性能研究

为解决自复位支撑耗能能力不足且来源单一、耗能材料成本高昂的问题,提出了一种新型自复位复合阻尼耗能支撑。支撑由金属屈服阻尼装置、黏弹阻尼装置并联预压碟簧自复位装置组成。对其基本构造和工作原理进行阐述,通过精细化模拟研究了支撑的耗能、复位、承载和变形能力。结果表明,在往复荷载作用下,支撑的滞回响应具有稳定饱满的旗形特征,拉压对称、无残余变形,能够兼顾不同加载频率下的性能需求。揭示了支撑加载制度和设计参数对其滞回性能的影响规律,结果表明:加载频率从0.3 Hz增加到2.0 Hz,黏弹阻尼装置提供的阻尼力增大,支撑耗能量由8.32 kJ增加到11.93 kJ;随着碟簧预压力的增加,支撑激活力从378.98 kN增加到562.67 kN,复位性能始终得到充分发挥;支撑耗能能力主要受三角形钢板个数和黏弹材料剪切面面积影响,增加4个三角形钢板或将黏弹材料剪切面面积从140 mm×140 mm增加到300 mm×140 mm,支撑的等效黏滞阻尼比分别同比增长39.93%和16.09%。

基于虚拟同步机的风-光-储并网系统自适应功频控制策略

风-光-储系统通过虚拟同步发电机(virtual synchronous generator,VSG)并网时,其运行工况变化将引起系统功频波动。针对这一问题,提出一种VSG自适应惯量阻尼功频控制策略。首先,建立VSG的数学模型及功率小信号模型,分析虚拟参数变化对系统稳定性的影响;然后,依据系统受扰时的功角曲线分析惯量阻尼的动态特性,设计了一种分段线性调整函数,并给出参数选取原则;最后,在Matlab/simulink平台中搭建仿真模型验证。结果表明,在工况变化情况下,采用VSG自适应控制的风光储并网系统功频响应得到了改善,相比传统VSG控制具有更好的动态调节性能。

《临证指南医案》以通为用论治风湿痹思想浅析

从风湿痹的定义、病因病机、治法方药等多个方面对《临证指南医案》中诊治风湿痹的医案进行总结分析,认为风湿痹的病因为风湿阻络或夹杂寒、热、瘀等因素,治法主要有通表利湿、散寒通脉、清热通下、祛瘀通经等,强调以通为用、启闭通痹。以通为用思想贯穿于《临证指南医案》的遣方用药之中。

槽形钢箱梁涡振性能及抑振措施试验研究

为提高槽形钢箱梁桥的抗风性能,对槽形钢箱梁的涡振性能及抑振措施进行试验研究。以某人行景观桥槽形钢箱梁为背景,通过主梁节段模型风洞试验,研究+3°、0°、-3°风攻角下均匀流与紊流风场中槽形钢箱梁的涡振性能,分析交替封闭栏杆、将栏杆楔形扶手改为圆形扶手、提高阻尼比等措施的抑振效果。结果表明:原槽形钢箱梁断面涡振性能不满足规范要求,均匀流风场中,3个风攻角下均出现了超限的竖弯涡振,+3°和-3°风攻角下出现了不同程度的扭转涡振,最不利风攻角为-3°;紊流风场中,最不利风攻角下原断面竖弯涡振振幅降低了23%,未见明显扭转涡振;楔形扶手栏杆交替封闭使结构竖弯涡振振幅增大,主梁涡振性能降低;单独改变栏杆扶手形状为圆形对主梁涡振性能影响不大,在此基础上交替封闭栏杆能够有效抑制主梁涡振;提高结构阻尼比能有效抑制主梁涡振,阻尼比为7‰时,主梁竖弯涡振振幅可降至规范限值的一半左右。

天然橡胶/反式-1,4-聚异戊二烯并用胶的制备及性能研究

制备减震制品用天然橡胶(NR)/反式1,4-聚异戊二烯(TPI)并用胶,并研究天然TPI(杜仲胶和古塔波胶)和合成TPI(牌号TPI-28,TPI-58,TPI-80)对NR/TPI并用胶性能的影响。结果表明:合成TPI的结晶度高于天然TPI;天然TPI和合成TPI对NR/TPI混炼胶的加工安全性和硫化速率的影响十分微小;与NR硫化胶相比,NR/TPI硫化胶的邵尔A型硬度和100%定伸应力提高,回弹值增大,压缩永久变形减小,阻尼性能提高,动态生热降低,耐热空气老化性能改善,耐疲劳性能显著提高,尤其是NR/TPI-28硫化胶的六级屈挠龟裂疲劳次数和伸张疲劳次数分别达到100万和近200万。NR/TPI并用胶可显著延长减震制品的使用寿命。

橡胶内嵌弹簧的复合型减振器性能研究

针对一种T型减振器,分别在其外圆柱与内圆柱区域嵌入弹簧,研制出两种新型复合减振器,开展了静态力学性能与减振性能的研究。试验表明:内圆柱嵌入弹簧后在3.6mm的压缩变形下刚度增大2.2%,阻尼比仅减小0.2%,说明其在变载荷条件下具备更稳定的静态刚度与阻尼比;外圆柱嵌入弹簧可使原本硬度较低的橡胶减振器获得与高硬度橡胶减振器相近的振动传递率与结构损耗因子,动静刚度比略有提升,表明其具备较好的减振性能。相比改良填料配比,通过向低硬度橡胶内部引入金属结构改良性能的方案具备更好的可设计性与应用前景。

丁基橡胶阻尼复合材料的研究进展

丁基橡胶(IIR)因分子链上具有较多的甲基,其阻尼性能优异,但IIR分子链中双键少、不含极性基团,导致IIR与填料的相容性差,且其阻尼复合材料的硫化时间长、与金属等其他材料的粘合性能较差,限制了IIR的进一步应用。本文介绍IIR的共混改性(与无机填料共混改性、与树脂或/和其他胶种共混改性)、与有机小分子杂化改性、结构改性和化学改性制备IIR阻尼复合材料的研究概况,采用这些改性方法制备的IIR阻尼复合材料的阻尼性能提高,阻尼温域拓宽。

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。

双级串联调谐质量阻尼器减振镗杆的设计与性能仿真分析

针对大长径比镗刀杆在加工大型复杂零件的孔及孔系结构中容易产生振动、加工效率低且加工质量不稳定等问题,提出了一种内置双级串联调谐质量阻尼器的新型减振镗杆,建立了减振镗杆的力学等效模型,通过求解和分析减振镗杆的振幅比,确定了减振镗杆最优的阻尼器长度及阻尼比。利用MATLAB/Simulink分别求解减振镗杆和普通镗杆的加速度响应信号,结果表明,减振镗杆的吸振性能显著提高,振动衰减时间大幅缩短。应用Workbench对两种镗杆进行模态分析和谐响应分析,得到固有频率和幅频曲线,发现减振镗杆的振幅远小于普通镗杆。本研究为减振刀具的研制与推广提供了一定的理论参考。