Application of spherical tuned liquid damper in vibration control of wind turbine due to earthquake excitations

A spherical tuned liquid damper (TLD) is proposed as a cost‐effective method to reduce the earthquake‐induced vibration of wind turbines. A 1/20‐scale test model was designed to investigate its performance of controlling the structural vibration. A series of free and forced vibration experiments with different water depths in hemispherical containers were performed on the shaking table. Three measured ground acceleration‐time histories, including El Centro NS, El Centro EW and Tianjin EW, were selected to verify the effectiveness of spherical TLD in suppressing the earthquake‐induced vibration. The experimental results showed that the spherical TLD could effectively improve the damping capacity of the test model. The standard deviation of the dynamic response could be effectively reduced when the excitation frequency was approximately equal to its fundamental frequency. The liquid sloshing motion in containers was characterized by a highly nonlinear and complex nature. The effectiveness of spherical TLDs does not increase linearly as the mass of water in containers and is influenced greatly by the frequency components of earthquake excitations. For El Centro EW excitation, the standard deviations of the dynamic responses could be reduced more than 40% when the liquid mass was about 2% of the generalized mass. Copyright © 2015 John Wiley & Sons, Ltd.     

Seismic vulnerability assessment of reinforced concrete silo considering granular material‐structure interaction

As a special shell structure, silos are used in storing a wide range of multitudinous granular materials. However, seldom have researchers assessed seismic vulnerability of the reinforced concrete (RC) silo. This paper aims at studying the seismic vulnerability assessment of a silo, which is located in Zhoushan, China. Prior to assessing the seismic vulnerability of the selected RC silo, the validation of the hypoplastic constitutive model, which is used to simulate granular materials, is studied. After discussing the validation of the hypoplastic theory, the numerical model considering granular material‐structure interaction is developed by means of the ABAQUS software. And the numerical simulation results are compared with the experimental data obtained from a shaking table test discussed in order to confirm the validation of the numerical model, which is used to study the seismic vulnerability of the RC silo. Then the seismic fragility assessment of the selected RC silo is performed using the incremental dynamic analysis. The analytical results showed that the hypoplastic theory can be used to simulate the stored materials in the silo considering the collapse property before entering plastic state of granular materials. For the design basic acceleration, the fragility curves of the selected RC silo showed that the probability of exceeding the no or light damage state was about 2.12%. For the maximum considered earthquake, the exceeding probability of no or slight and the moderate damage states was 17.63% and 1.31%, respectively. With respect of the severe and total damage state, the exceeding probabilities were almost zero. Therefore, the selected RC silo structure has enough safety stock to withstand strong earthquakes in the future. Finally, a general design procedure considering seismic fragility assessment was presented in order to provide references for other structure design. Copyright © 2016 John Wiley & Sons, Ltd.     

梁端铰型受控摇摆式钢筋混凝土框架抗震性能振动台试验研究

受控摇摆式钢筋混凝土框架(CR-RCF)采用梁柱铰接节点,后张预应力钢筋提供结构整体恢复力,并采用层间阻尼器耗散地震能量、控制结构整体位移。通过模拟地震振动台对比试验,研究受控摇摆式钢筋混凝土框架的抗震性能。介绍了CR-RCF结构的摇摆机制及摇摆节点的构造形式,设计了受控摇摆式钢筋混凝土框架和常规框架两个振动台试验模型,输入El Centro地震波,得到了不同地震动峰值加速度下结构的动力响应,对比分析了两个模型的振动台试验结果。结果表明：CR-RCF结构较常规框架具有更小的抗侧刚度,故其地震加速度响应更小;CR-RCF结构设置了层间阻尼器耗能装置,地震作用下的结构整体位移得到有效控制;在经历罕遇地震作用后,仅层间阻尼器进入屈服状态,主体框架承重构件保持完好,无任何损伤,表现出优异的“免损伤”特征。     

结构-群桩基础地震响应离心振动台模型试验

为研究桥梁群桩基础的大质量承台和外露桩基对桩-土动力相互作用效应的影响,分别对低承台（与土接触）和高承台群桩基础进行了离心振动台模型试验。试验中地基土采用了黏质粉土,上部结构简化为质点和杆构件,基础形式包括单桩和群桩。为模拟地震剪切波作用下土层运动效应,采用叠环式层状剪切箱实现土体的层状自由剪切,箱内壁设置橡胶膜以消除边界反射效应。在加速度为5.0g的离心环境中,选取Chi-Chi地震波作为基底激励输入,在不同输入峰值加速度下,分析了结构-群桩基础的地震响应。试验结果表明：与低承台群桩基础相比,高承台形成的群桩外露会增加上部结构和承台的惯性效应,改变桩身峰值弯矩的分布,表现为承台与桩接触处的桩身峰值弯矩下降,但桩身最大峰值弯矩改变较小。     

液化土层中桩基抗震性能研究

通过振动台试验，研究了饱和砂土中桩基的振动特性，对桩土振动过程中的动力相互作用有了初步的认识。根据试验结果，得到距模型桩不同位置处的砂土的动力p-y曲线与API推荐做法得到的静力p-y曲线，并对两者进行了比较，说明了饱和砂土液化降低了模型桩的横向承载能力，但并没有使模型桩的横向承载能力完全丧失。提示工程设计人员在对可液化砂层的横向承载能力进行考虑时，完全不考虑可液化砂层的横向承载能力是偏于保守的。     

带阻尼器高层方钢管混凝土框架结构模拟地震振动台试验研究

对一幢带阻尼器高层方钢管混凝土框架结构的1/15缩尺模型进行了模拟地震振动台试验,深入研究了该结构的动力特性和地震反应特征,并通过比较考察了阻尼器的作用效果.结果表明：该结构未出现明显的薄弱层,结构整体扭转反应相对较小,阻尼器发挥了较好的消能减震作用,但结构抗侧刚度较小,层间弹塑性位移角未能满足规范对消能减震结构所规定的宜采用的限值（1/80）,结构设计中已根据试验结果进行了改进,满足了规范要求.     

钢结构住宅体系加气混凝土外墙板抗震性能试验研究

介绍了一钢结构住宅体系的外墙板足尺模型振动台试验,并通过试验结果分析,研究了钢结构住宅体系外墙板以及墙板与结构构件连接节点处的抗震性能,了解了节点和墙板的破坏特征及墙板对结构动力特性与抗震性能的影响。得出了对带墙板钢结构抗震设计有益的结论。     

配筋砌体单层房屋模型振动台试验研究

配筋砌体以其受力性能好,施工便捷,节省建筑材料,在防止房屋开裂方面有显著效果等诸多优点而正在逐步成为我国小高层住宅房屋的主导型新型墙体材料之一。通过一个混凝土小型空心砌块配筋砌体单层房屋模型的振动台试验,探讨了配筋砌体房屋的动力性能、墙体内钢筋的应变变化、配筋剪力墙和非配筋隔墙的相互作用以及在试验过程中模型房屋的刚度、阻尼的变化等,考察了配筋砌体模型房屋的受力情况和破坏过程。试验表明配筋砌体房屋有良好的抗震性能。     

偏心结构自复位复合摩擦阻尼器平扭耦联震动控制振动台试验研究

研制开发了一种新型自复位形状记忆合金复合摩擦阻尼器（HSMAFD）,该新型阻尼器由超弹性形状记忆合金丝和摩擦装置复合而成,并通过模型试验研究了新型阻尼器在循环荷载作用下的力学性能。制作了一个三层两跨单向偏心钢框架缩尺模型,进行了新型阻尼器偏心结构平动及扭转耦联震动反应振动台试验。考虑了不同考虑场地条件对结构地震反应的影响,对比分析了无控结构和装有新型阻尼器有控结构的震动反应。研究结果表明,新型超弹性形状记忆合金复合摩擦阻尼器对结构的平动及扭转角位移均有一定的控制效果,但场地条件对控制效果有较大的影响。     

穿越断层破碎带隧道动力响应特性分析

 通过数值分析和振动台模型试验相结合的方法,研究穿越断层破碎带隧道在地震荷载作用下横向内力分布和纵向动力响应特性。结果表明：围岩条件是影响衬砌地震内力的重要因素,围岩越差,地震作用产生的内力越大,其抗震性能越差;在横断面方向,不同围岩条件下衬砌内力均在共轭45°方向最大,为隧道抗震最不利位置;在纵断面方向,隧道位于围岩与断层破碎带接触面时,衬砌地震内力急剧增大;当隧道断面沿纵向远离断层破碎带一定距离后,其内力趋于一个稳定值。研究结果可为穿越断层破碎带隧道结构抗震设防提供参考。