Experimental study on seismic behavior of circular RC columns strengthened with pre-stressed FRP strips

Bonding fiber reinforced polymer （FRP） has been commonly used to improve the seismic behavior of circular reinforced concrete （RC） columns in engineering practice. However, FRP jackets have a significant stress hysteresis effect in this strengthening method, and pre-tensioning the FRP can overcome this problem. This paper presents test results of 25 circular RC columns strengthened with pre-stressed FRP strips under low cyclic loading. The pre-stressing of the FRP strips, types of FRP strips and longitudinal reinforcement, axial load ratio, pre-damage degree and surface treatments of the specimens are considered as the primary factors in the tests. According to the failure modes and hysteresis curves of the specimens, these factors are analyzed to investigate their effect on bearing capacity, ductility, hysteretic behavior, energy dissipation capacity and other important seismic behaviors. The results show that the initial lateral confined stress provided by pre-stressed FRP strips can effectively inhibit the emergence and development of diagonal shear cracks, and change the failure modes of specimens from brittle shear failure to bending or bending-shear failure with better ductility. As a result, the bearing capacity, ductility, energy dissipation capacity and deformation capacity of the strengthened specimens are all significantly improved.

Seismic Behavor of RC Beam-Column Joint with Additional Bars under Cyclic Loading

The behavior of Beam-Column Joints in moment resisting frame structures are susceptible to damage caused by seismic effects due to poor performance of the joint.A good number of researches were carried out to understand the complex mechanism of RC joints which are considered in seismic design code practices presently adopted.The traditional construction detailing of transverse reinforcement have shown serious joint failure. This paper introduces a new design philosophy involving the use of additional diagonal bars within the joint particularly suitable for low to medium seismic effects in earthquake zones throughout the world.In lieu to this study,ten(10) full-scale interior beam-column specimens were constructed with various additional reinforcement details and configurations as will be discussed in the later.The experiment provided adequate results to proof the idea of additional bars as suitable approach in reinforced concrete structures where earthquake is eminent.While compared with overall cracking observation during the test,the specimen with additional bars (diagonal and straight) had shown few cracks on the column than the ones without.Furthermore,concrete confinement is certainly an important design method as recommended by certain international codes.

经血间充质干细胞外泌体对人卵巢癌细胞A2780生物学行为的影响

目的 探讨经血源性间充质干细胞(menstrual blood-derived mesenchymal stem cells,MenSCs)来源的外泌体(MenSCs-derived exosomes,MenSCs-Exos)对人卵巢癌细胞A2780增殖、迁移、侵袭能力和细胞周期分布的影响和机制。方法 分离纯化MenSCs,流式细胞术鉴定其细胞表型,油红O染色观察其成脂分化能力;超速离心法分离MenSCs-Exos,电子显微镜观察外泌体形态,纳米颗粒追踪分析其大小及分布,蛋白免疫印迹法检测外泌体标志性蛋白分子CD9、TSG101、calnexin的表达。采用CCK-8实验、划痕实验、Transwell细胞体外侵袭实验、流式细胞仪检测MenSCs-Exos对A2780细胞增殖、迁移、侵袭能力和细胞周期分布的影响;蛋白免疫印迹法检测Wnt/β-catenin信号通路相关蛋白和迁移相关蛋白的表达。结果 成功分离具有干细胞表型和成脂分化潜能的MenSCs,同时检测发现MenSCs-Exos为边缘清晰、大小分布均匀的膜性囊泡,粒径为30~150 nm,平均为72.89 nm,膜表面标志性蛋白CD9、TSG101表达呈阳性,calnexin表达呈阴性。与对照组相比,MenSCs-Exos能增强A2780细胞增殖、迁移和侵袭能力,影响其细胞周期分布,并且可上调β-catenin、c-Myc、TCF4、Cyclin D1、Vimentin、N-cadherin的表达,下调E-cadherin的表达。结论 MenSCs-Exos可能是通过激活Wnt/β-catenin信号通路促进A2780细胞增殖,并通过下调E-cadherin的表达促进A2780细胞的迁移和侵袭。

考虑可再生能源出力不确定性与碳排放成本的台区运行优化策略研究

随着电网公司市场化改革的进行,电力市场将逐渐吸引各类社会资本的投入。配电网下辖的台区和配电网本身将成为隶属于不同利益主体的竞争场所,形成相互竞争的博弈格局。与此同时,分布式可再生能源的高比例接入提升了配电网能源构成的清洁性,但其出力的不确定性也导致配电网调度运行风险进一步提升。为平抑分布式可再生能源出力的不确定性,将隶属于同一配电台区的“分布式可再生能源-分布式火电-储能-灵活性负荷”作为整体,以安全性和经济性为目标,由配电网运营商统一调控。首先,为协调配电网运营商和其下辖台区之间的利益关系,文章建立了由配电网运营商和其下辖的多个台区所构成的主从博弈模型,运用条件风险价值理论量化以风光为主的分布式可再生能源导致的不确定性风险;然后,为进一步考虑分布式火电的碳排放成本,实现分布式可再生能源与火电的灵活互补调控,将各台区主体在碳市场中的获利加入优化调度模型中,通过BP神经网络拟合,将主从博弈模型简化为单层模型,并运用粒子群算法进行求解;最后,通过算例讨论了不同可再生能源出力风险与碳价下各台区内不同种类分布式电源出力变化,进一步验证了该优化策略的有效性。

磁流变阻尼器的半主动控制及实时混合模拟试验研究

磁流变阻尼器作为一种比较典型的半主动控制元件,具有构造简单、响应速度快、耐久性好、阻尼力大且连续可调等优点。即使地震中能源中断,磁流变阻尼器仍可以作为被动耗能装置继续工作发挥作用,可靠性高。设计合理有效的磁流变阻尼器半主动控制方法,对于整体结构的减震效果尤其重要。提出一种改进的磁流变阻尼器的半主动控制策略-改进的Bang-Bang控制策略,对装有磁流变阻尼器的减震控制3层框架结构进行了一系列的实时混合模拟试验,对多种半主动控制方法下的振动控制效果进行试验分析。试验结果表明:磁流变阻尼器对框架结构的减震效果显著,并验证了提出的磁流变阻尼器半主动控制策略的有效性。

自复位钢筋混凝土框架结构及其拟静力试验

自复位钢筋混凝土框架结构是一种新型可恢复功能结构。相比于普通混凝土框架,该结构在地震作用下结构损伤轻微残余变形小,在地震后不需修复或稍加修复即可重新投入使用。因此,该结构是一种适用于高烈度地震频发地区中低层框架的低成本新型防震结构。自复位混凝土框架结构体系使用无粘结预应力筋连接结构中的各个构件,在结构的节点位置形成可以互相分离的界面。在较大的地震作用下,构件间允许发生界面分离,表现为梁端节点张开与柱脚节点提离等现象,从而减轻了结构的损伤。震后在预应力的作用下,构件间的界面重新闭合,实现自复位。首先总结了已有自复位节点的研究成果,阐明了自复位结构的组成与关键构造。为了进一步研究自复位钢筋混凝土框架在地震作用下的变形模式与受力特征,进行了三向自复位框架结构的1:2.5缩尺模型拟静力试验。本文给出了试验模型的基本信息,包括模型的设计参数,材料性能,具体构造等内容;给出了主要的静力试验结果,包括试验的主要现象与损伤特征、模型的变形模式、滞回曲线、骨架曲线、刚度退化与残余变形等信息。试验结果表明:模型的变形能力强,在1/38顶层位移比(顶层位移/结构高度)下模型除少数细微裂缝外没有损伤,在更大的变形下模型损伤逐渐在梁端节点位置开展;在1/19顶层位移比下模型的承载力仍然没有出现下降;模型的残余变形很小,在模型加载的全过程中,其残余位移角都处在可以接受的范围内。

砂与黏土混合物强度特性环剪试验研究

为分析砂和黏土混合物的强度特性,将石英砂和高岭土按不同质量比配制试验土样,开展了一系列固结排水条件下的环剪试验。通过设置轴压为75 k Pa、150 k Pa、300 k Pa和600 k Pa状态下开展试验,得到土样剪切角与剪切应力的关系曲线。根据试验曲线的峰值剪应力,通过莫尔-库仑准则得到土样的黏聚力和摩擦角。结果表明,砂和黏土混合物的黏聚力在5~18 k Pa范围内波动,当高岭土含量为50%时黏聚力值达到最小值。当高岭土含量小于50%时,摩擦角随高岭土含量增加略有减小;当高岭土含量超过50%时,摩擦角随高岭土含量增加而减小的趋势更明显。

冷弯薄壁钢管-稻草板组合墙体抗剪性能试验

目的 研究冷弯薄壁钢管-稻草板组合墙体的抗剪性能,为该类墙体在实际工程中的应用提供理论依据。方法 组合墙体由钢骨架和稻草板通过ST4.8×85 mm的外六角自攻螺钉连接而成,其中钢骨架由钢管和U型导轨通过ST3.5×16 mm的梅花沉头自攻螺钉连接。对3面组合墙体进行水平单调加载试验,分析各试件的破坏过程和破坏机理,得到组合墙体的屈服荷载、延性系数和抗侧刚度等抗剪性能指标。结果 组合墙体主要的破坏模式为受压侧钢管底部局部屈曲,稻草板表面出现斜向褶皱;无竖向荷载的组合墙体比竖向荷载为15 kN和30 kN的组合墙体在屈服荷载上分别提高了8.11%和14.87%,在抗侧刚度上降低了32.86%和70.18%。结论 稻草板对钢骨架起到了良好的约束作用,组合墙体整体性良好且具有较高的抗剪承载力。组合墙体的抗剪承载力随着上部竖向荷载的增加而逐渐降低,但同时提高了组合墙体的延性系数和抗侧刚度,增加了墙体的稳定性。

考虑固废强度非线性的填埋场地基承载力分析

基于幂函数准则描述了固废的非线性强度特性,并分析了该准则随强度参数的变化规律。与基于摩擦角修正的非线性Mohr-Coulomb准则和二次函数非线性强度准则进行了对比,并探讨了将幂函数准则换算为线性Mohr-Coulomb准则得到的黏聚力和内摩擦角随应力的变化规律。通过与一系列直剪试验结果对比,验证了幂函数准则预测固废非线性强度的合理性。基于所建立的非线性强度准则,对填埋场地基承载力进行数值模拟,并通过与基于线性强度准则模拟结果对比,获得了固废强度非线性对承载力的影响规律。参数分析结果表明,地基承载力值对强度准则指数参数的变化更敏感。

带有可更换连梁的钢筋混凝土结构设计方法

钢筋混凝土剪力墙结构通过设置可更换连梁,在地震作用下集中损伤,保护主体结构不受或只受微小破坏,震后更换损伤构件即可恢复结构功能。参照现行规范和已有试验分析结果,在普通钢筋混凝土结构设计基础上,提出带有可更换连梁的钢筋混凝土结构实用设计方法,设定性能目标,总结设计流程。采用提出的设计方法对1个50层钢筋混凝土结构进行设计,并采用大型有限元分析软件ABAQUS建立数值模型,验证结构性能目标和提出的设计方法。结果表明:按该方法设计的带有可更换连梁的钢筋混凝土结构能满足所设定的性能目标,设计方法合理实用,为该新型结构的工程应用提供了参考。

中国抗震规范与欧洲规范8的对比研究

我国是世界上地震灾害最严重的国家之一,自1959年起第一部抗震规范颁布至今,已有近60年的历史。从主要沿袭苏联标准到自主试验探究再到主动与国际接轨、逐步提高抗震设防水准,此过程中我国的抗震规范不断完善。本文主要对《建筑抗震设计规范》(GB50011-2010)和《Eurocode 8》进行对比分析,同时考虑材料基本性能、分项系数、荷载组合系数、抗震设防目标等基本原则;场地类别和设计用反应谱取值、底部剪力法等地震作用计算;内力调整、抗震构件等具体设计方法等。此外,利用算例对比两本规范在结构抗震设计时的安全性验算、内力计算和配筋量等方面的差异。

Shake-table testing of a self-centering precast reinforced concrete frame with shear walls

The seismic performance of a self-centering precast reinforced concrete （RC） frame with shear walls was investigated in this paper. The lateral force resistance was provided by self-centering precast RC shear walls （SPCW）, which utilize a combination ofunbonded prestressed post-tensioned （PT） tendons and mild steel reinforcing bars for flexural resistance across base joints. The structures concentrated deformations at the bottom joints and the unbonded PT tendons provided the self-centering restoring force. A 1/3-scale model of a five-story self-centering RC frame with shear walls was designed and tested on a shake-table under a series of bi-directional earthquake excitations with increasing intensity. The acceleration response, roof displacement, inter-story drifts, residual drifts, shear force ratios, hysteresis curves, and local behaviour of the test specimen were analysed and evaluated. The results demonstrated that seismic performance of the test specimen was satisfactory in the plane of the shear wall; however, the structure sustained inter-story drift levels up to 2.45%. Negligible residual drifts were recorded after all applied earthquake excitations. Based on the shake-table test results, it is feasible to apply and popularize a self-centering precast RC frame with shear walls as a structural system in seismic regions.

鞣酸小檗碱治疗特应性皮炎作用研究

目的研究鞣酸小檗碱在特应性皮炎(atopic dermatitis,AD)中的治疗作用。方法将30只雄性、SPF级BALB/c小鼠随机分为5组:对照组、模型组、1%鞣酸小檗碱组、5%鞣酸小檗碱组、0.03%他克莫司组,除对照组外其余组于第1周第1、3、5天分别在小鼠双侧耳廓外侧皮肤局部涂抹1%2,4-二硝基氯苯(DNCB)的丙酮-橄榄油溶液各20μL进行初次致敏,第2~3周起每3 d在小鼠双侧耳廓外侧的致敏处涂抹0.5%DNCB的丙酮-橄榄油溶液各20μL进行再次致敏,并每天分别使用药物进行治疗;对照组于相同时间涂抹等量的丙酮-橄榄油基质。每周按相同时间间隔测量两次小鼠双侧耳部厚度。实验结束后处死小鼠,切取小鼠耳朵行组织病理学检查。结果经过DNCB致敏之后,与对照组小鼠相比,模型组小鼠耳部厚度显著增加,差异有显著统计学意义(P<0.01)。经过1%、5%鞣酸小檗碱和0.03%他克莫司治疗后,小鼠耳部厚度有明显改善,与模型组相比,差异均有显著统计学意义(P<0.01),且各浓度鞣酸小檗碱组与0.03%他克莫司组相比,小鼠耳部厚度差异无统计学意义(P>0.05)。组织病理学结果显示模型组与对照组相比,小鼠耳部真皮层水肿、炎症细胞浸润明显,表皮层厚度增加,其厚度差异具有显著统计学意义(P<0.01)。使用1%、5%鞣酸小檗碱和0.03%他克莫司治疗后,表皮层厚度减少,差异有显著统计学意义(P<0.01),说明疾病状况改善,各浓度鞣酸小檗碱组与0.03%他克莫司组相比差异无统计学意义(P>0.05)。结论鞣酸小檗碱对特应性皮炎具有良好的治疗效果,有望用于开发治疗AD,为临床治疗AD提供新思路。

Shake table testing of a multi-tower connected hybrid structure

Many single-tower reinforced concrete core wall-steel frame （RCC-SF） buildings have been built in China, but there are no buildings of different-height multi-tower hybrid system. A multi-tower RCC-SF tall building was thus studied because of its structural complexity and irregularity. First, a 1/15 scaled model structure was designed and tested on the shake table under minor, moderate, and major earthquake levels. Then, the dynamic responses of the model structure were interpreted to those of the prototype structure according to the similitude theory. Experimental results demonstrate that, despite the complexity of the structure, the lateral deformation bends as the ＂bending type＂ and the RC core walls contribute more than the steel frames to resist seismic loads. The maximum inter-story drift of the complex building under minor earthquakes is slightly beyond the elastic limitation specified in the Chinese code, and meets code requirements under major earthquakes. From the test results some suggestions are provided that could contribute favorable effect on the seismic behavior and the displacement of the building.

Recent progress of seismic research on tall buildings in China Mainland

As a result of rapid economic growth and urbanization in the past two decades,many tall buildings have been constructed in China Mainland,offering researchers and practitioners an excellent opportunity for research and practice in the field of structural engineering. This paper reviews progress by researchers throughout China Mainland on the seismic research of tall buildings,focusing on three major topics that impact the seismic performance of tall buildings. These are:(1) new types of steel-concrete composite structural members such as steel-concrete composite shear walls and columns,(2) earthquake resilient shear wall structures such as shear walls with replaceable structural components,self-centering shear walls and rocking walls,and(3) performance-based seismic design,including seismic performance index,performance level and design method. The paper concludes by presenting future research needs and directions in this field.

Study on the effect of the infill walls on the seismic performance of a reinforced concrete frame

Motivated by the seismic damage observed to reinforced concrete （RC） frame structures during the Wenchuan earthquake, the effect of infill walls on the seismic performance of a RC frame is studied in this paper. Infill walls, especially those made of masonry, offer some amount of stiffness and strength. Therefore, the effect of infill walls should be considered during the design of RC frames. In this study, an analysis of the recorded ground motion in the Wenehuan earthquake is performed. Then, a numerical model is developed to simulate the infill walls. Finally, nonlinear dynamic analysis is carried out on a RC frame with and without infill walls, respectively, by using CANNY software. Through a comparative analysis, the following conclusions can be drawn. The failure mode of the frame with infill walls is in accordance with the seismic damage failure pattern, which is strong beam and weak column mode. This indicates that the infill walls change the failure pattern of the frame, and it is necessary to consider them in the seismic design of the RC frame. The numerical model presented in this paper can effectively simulate the effect of infill walls on the RC frame.

高层建筑单核心筒周边悬挂结构振动台试验研究

为深入研究高层建筑单核心筒周边悬挂结构体系在地震作用下的动力响应特点以及核心筒底部的受力性能、损伤特征、破坏模式等,以实际高层建筑结构为原型,设计并制作了缩尺比为1/20的模型,进行了三向激励下的模拟地震振动台试验,包含了多遇、设防、罕遇以及极罕遇地震作用工况。试验中核心筒呈现的损伤破坏过程为:连梁最先开裂;随后连梁原有裂缝加深,同时筒体底部墙肢也逐渐进入损伤状态;最后筒体底部墙脚达到压溃状态。该损伤破坏是渐变过程,具有延性破坏的特征,表明核心筒单独作为抗侧力系统能够提供两道抗震防线。试验结果表明,悬挂部分竖向加速度峰值响应约是筒体的2~4倍,结构设计中应予以重视;对于单核心筒周边悬挂结构,将楼面主梁与核心筒以及悬吊柱分别铰接,受力简洁合理,吊杆应力设计可控。研究成果可为单核心筒周边悬挂结构体系的工程设计提供相应的结构抗震性能依据,也为城市密集区域内空间的高效综合利用提供有利条件。

多元特征驱动的超高层建筑变形状态智能学习与预测

为实现基于监测数据的结构未来状态可预测,提出了一种多元特征驱动的超高层建筑变形状态智能学习与预测方法。通过信号自适应分解、响应多维特征分析与子信号相关性分析,实现结构响应数据重构与组合,并基于长短时记忆网络(LSTM)进行多通道学习与多步预测。利用上海中心大厦在台风“梅花”作用下的结构顶部水平位移响应实测数据,揭示位移响应数据具有超低频准静态变形与一阶模态控制振动响应的叠加特征以及时域非平稳特性。通过响应数据重构,形成三组具有不同时间尺度、振动幅值和平稳特性的子信号组合。通过3个独立LSTM模型,实现基于300个时间步数据预测未来1~60个时间步的位移响应。结果表明,在控制未来预测时间步长(60个时间步内)的条件下,所提出的数据驱动的学习预测模型能充分学习与预测已知的位移响应数据特征与物理状态,具备较高的预测精度,归一化误差可控制在10%以内,能实现对超高层建筑变形状态的准确实时预测。

可恢复功能防震结构研究进展

对于可恢复功能防震理念,要求结构在保护生命的前提下,能够在震后快速恢复使用功能,尽量减少对正常生活和生产的影响。依据该理念,作为可恢复功能城市的基本组成部分,可恢复功能防震结构合理应用摇摆、自复位、可更换和耗能等四种机制,将损伤集中于可更换的耗能构件或部件,从而保护主体结构,使其无损伤或可快速修复。因此,结构功能可在震后及时恢复。利用这些机制,可恢复功能防震结构在材料、构件和体系三个层次具有不同的实现方案,包括摇摆结构、自复位结构、可更换构件/部件结构和复合自复位结构。基于可恢复功能的设计和评估方法,采用恢复时间、经济损失等更加直接的指标,为这一新型结构体系的应用奠定基础。目前,应提出更多的可恢复功能防震结构新体系,而进一步研究该类结构的关键构造和动力特性,提出切实可行的设计方法并形成统一的设计规范,应成为进一步研究的重点。

近场脉冲型地震作用下复合自复位结构刚度需求的谱分析

复合自复位结构利用摇摆机制和耗能机制控制结构层间位移集中程度的同时降低其层间位移角响应,将损伤集中于可更换的次体系（摇摆部件）中从而使主体系（框架结构）可以快速恢复使用功能。为分析其刚度需求与动力响应之间的关系,提出了拓展的复合自复位结构的双梁模型,将主体系和次体系分别简化为剪切梁和底部带有弹性转动约束的弯曲梁,其动力特征由剪弯刚度比α和弯曲梁底部转动约束刚度比Rf两个无量纲参数决定。通过求解动力方程得到该体系振型和振型转角的闭合解,进而得到体系的广义层间位移角谱和层间位移集中系数谱的计算公式。由简化脉冲模型得到近场破裂的方向性效应引起的双向脉冲和滑冲效应引起的单向脉冲。在这两种近场脉冲作用下分析了参数α和Rf对该体系广义层间位移角谱和层间位移集中系数谱的影响。分析表明,当1≤α≤5和0〈Rf≤5时，该体系可以有效且稳定地控制中低层框架结构的层间位移程度并降低层间位移角响应；广义层问位移角谱和层间位移集中系数谱作为量化刚度需求和控制目标的工具可以初步实现该体系的性能化设计。