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.

Determination of Shear Center of Arbitrary Cross-Section

In structural analysis, it is often necessary to determine the geometrical properties of cross section. The location of the shear center is greater importance for an arbitrary cross section. In this study, the problems of coupled shearing and torsional were analyzed by using the finite element method. Namely, the simultaneous equations with respect to the warping, shear deflection, angle of torsion and Lagrange’s multipliers are derived by finite element approximation. Solving them numerically, the matrix of the shearing rigidity and torsional rigidity is obtained. This matrix indicates the coupled shearing and torsional deflection. The shear center can be obtained determining the coordinate axes so as to eliminate the non-diagonal terms. Several numerical examples are performed and show that the present method gives excellent results for an arbitrary cross section.

A New Modified Conductivity Model for Prediction of Shear Yield Stress of Electrorheological Fluids Based on Face-center Square Structure

A new modified conductivity model was established to predict the shear yield stress of electrorheological fluids (ERF). By using a cell equivalent method, the present model can deal with the face-center square structure of ERF. Combining the scheme of the classical conductivity model for the single-chain structure, a new formula for the prediction of the shear yield stress of ERF was set up. The influences of the separation distance of the particles, the volume fraction of the particles and the applied electric field on the shear yield stress were investigated.

Resilient performance of self-centering hybrid rocking walls with curved interface under pseudo-static loading

Frame and rocking wall(FRW)structures have excellent resilient performance during earthquakes.However,the concrete at interfacial corners of rocking walls(RWs)is easily crushed due to local extreme compression during the rocking process.An innovative RW with a curved interface is proposed to prevent interfacial corners from producing local damage,enhancing its earthquake resilient performance(ERP).The precast wall panel with a curved interface is assembled into an integral self-centering hybrid rocking wall(SCRW)by two post-tensioned unbonded prestressed tendons.Moreover,two ordinary energy dissipation steel rebars and two shear reinforcements are arranged to increase the energy dissipation capacity and lateral resistance.Two SCRW specimens and one monolithic reinforced concrete(RC)shear wall(SW)were tested under pseudo-static loading to compare the ERPs of the proposed SCRW and the SW,focusing on studying the effect of the curved interface on the SCRW.The key resilient performance of rocking effects,failure modes,and hysteretic properties of the SCRW were explored.The results show that nonlinear deformations of the SCRW are concentrated along the interface between the SCRW and the foundation,avoiding damage within the SCRW.The restoring force provided by the prestressed tendons can effectively realize self-centering capacity with small residual deformation,and the resilient performance of the SCRW is better than that of monolithic SW.In addition,the curved interface of the SCRW makes the rocking center change and move inward,partially relieving the stress concentration and crush of concrete.The rocking range of the rocking center is about 41.4%of the width of the SCRW.

Shear Stress in MR Fluid with Small Shear Deformation in Bctlattic Structure

A theoretical model based on BCT lattice structure was developed. Resultant force in the BCT lattice structure was deduced, following the interaction force of two kinds of magnetic particles. According to empirical FroHlich-Kermelly law, the relationship between the magnetic induction and the magnetic field was discussed, and a predictive formula of shear stresses of the BCT lattice structure model was established for the case of small shear deformation. Compared with the experimental data for different particle volume fractions, the theoretical results of the shear stress indicate the effects of the saturation magnetization and the external magnetic field on the shear stress.

Multi-Order and Multi-Center Metallogenic Zoning of Yinshan Cu-Au Polymetallic Ore Deposit,Jiangxi Province,China

Yinshan anticline is the product of tectono-dynamic deformation - metamorphism .Along the axis of the anticline exists a brittle-ductile shearing zone which obviously controls the ore-formation . Mineralization occurs along the axis of the anticline in a width of about 1000m .In the mining area .volcano- subvolcanic rocks of Early Yanshan period are divided into three cycles :Ⅰ intermediate acidic dacite lava and dacite porphyry ;Ⅱ acidic amphibole liparite and quartz porphyry;Ⅲ intermediate andesite porphyrite . Among them activities of ⅠandⅡ cycles are more intensive and are intimately related to the mineralization . Yinshan ore deposit is the result of combinative processes of tectono -dynamic and volcano -magmatic hydrothermal fluids, so that mere are two centers of metallogenic zoning, one being the axial strain zone of Yinshan anticline which is the center of first order, and the other being porphyry stock , 2nd order.

带有拼缝阻尼器的自复位预制双肢剪力墙的耗能能力研究

为提升自复位预制双肢剪力墙的耗能能力,针对预制双肢剪力墙提出了一种拼缝阻尼器,该阻尼器可适应接缝附近的大变形,帮助结构同时实现自复位和耗能的性能。通过拟静力试验,获得了该阻尼器的滞回曲线,验证了所提阻尼器具备良好的耗能性能;使用Opensees把阻尼器放入预制双肢剪力墙中进行数值分析,发现所提阻尼器在不降低结构原本自复位性能的同时,大大提升了结构的耗能能力。同时,耗能主要由拼缝阻尼器承担,结构自身的耗能和损伤较小,有利于实现结构在震后的快速修复。

一种新型自复位耗能段的力学性能试验研究

基于扩孔螺栓连接型耗能段和自复位SMA支撑,提出一种新型自复位耗能段,具有强耗能、高延性、低残余变形和低损伤等特点,可进一步提高偏心支撑结构的抗震性能和震后功能恢复能力。分别设计3个考虑摩擦滑移的自复位耗能段和1个普通自复位耗能段试验试件,并进行往复加载研究,得到其变形或破坏模式、滞回曲线和骨架曲线等。结果表明,滑移阶段耗能段处于相对静止状态,所有构件均处于弹性状态;非滑移阶段耗能段依次发生滑移、屈服、翼缘和腹板屈曲现象,整个过程中自复位SMA支撑中的SMA受拉,并为自复位耗能段提供承载力、耗能能力和复位力。自复位耗能段的骨架曲线主要包括弹性阶段、弹塑性阶段、强化阶段。最后,基于校正的有限元法对自复位耗能段进行分析,阐明自复位耗能段在不同阶段的耗能机理。

中心不重合径向剪切干涉迭代波前重构算法仿真分析

径向剪切干涉测量时经常会出现扩束与缩束光波中心不重合情况,传统波前重构算法会导致较大重构误差,其应用受到挑战。推导了中心不重合径向剪切干涉迭代波前重构算法,仿真分析了组合像差、单阶Zernike像差、中心偏移量大小及其计算误差对重构算法的影响。结果表明,在剪切光波中心不重合情况下,该文算法能够准确进行波前重构,重构效果显著优于传统算法;在论文仿真条件下,随着中心偏移量的增大,本文算法重构波面均方根误差(RMS)不高于0.05λ,而传统算法重构误差RMS值达1.6λ且与偏移量近似线性相关。

新型部分自复位耗能段的滞回性能与简化力学模型研究

提出一种用于偏心支撑结构中的部分自复位耗能段,主要包括自复位形状记忆合金(shape memory alloy,SMA)支撑和扩孔螺栓连接型耗能段,具有耗能能力和自复位能力强、构件损伤小、震后功能可恢复等特点。基于部分自复位耗能段的设计方法,合理设计其试验模型,由此得到变形模式和滞回曲线等。随后采用校正的有限元法对部分自复位耗能段力学性能进行研究,主要考虑SMA面积、高强螺栓预拉力和垫片滑移系数的影响。研究结果表明:滑移阶段自复位耗能段中耗能段处于滑移并保持相对静止状态;随后非滑移阶段耗能段开始承载、耗能和非弹性变形等,整个过程中自复位SMA支撑提供耗能和复位能力,以及减小构件残余变形。基于不同因素下的分析结果,提出滑移阶段和非滑移阶段下自复位耗能段简化的力学模型,为偏心支撑结构的抗震设计与分析提供新的思路和理论基础。

新型装配式自复位RC剪力墙设计与性能研究

为满足结构施工效率高、震后功能可恢复的多重目标,提出了一种新型装配式自复位RC剪力墙。该新型剪力墙主要包含RC墙板、碟簧复位装置和摩擦耗能装置,三者仅通过高强螺栓组装而成,施工方便且效率高;在地震作用下,主要由碟簧复位装置和摩擦耗能装置提供抵抗弯矩和恢复力,能减小整体剪力墙构件的震后残余变形和损伤,有效提高其震后功能可恢复性。该文分析了新型装配式自复位RC剪力墙的截面受力形式,提出了其截面承载力计算公式;设计了一新型装配式自复位RC剪力墙构件进行数值模拟,获得了其滞回性能,对比分析了其与普通剪力墙的承载力、耗能能力、自复位性能。结果表明:在相同位移角下,新型装配式自复位RC剪力墙的承载力小于普通剪力墙,但其极限承载力与普通剪力墙的峰值承载力相当,且其在超大震(2.0%位移角)下的残余位移角仅为0.31%,具有优异的自复位能力,能使结构在震后具有低损伤、功能可恢复的特点。增大碟簧复位装置的预压力,可有效提高新型剪力墙构件的承载力和累积耗能,但残余变形也相应增大。

新型竖齿摇摆自复位剪力墙抗震性能研究

底端固结在基础上的剪力墙,在地震中墙角最易损伤破坏,且耗能较差,震后不宜修复。提出了一种新型竖齿摇摆自复位剪力墙(self-centering vertical tooth swing shear wall,SCVT-SW)体系。SCVT-SW体系由钢筋混凝土墙体、碟簧复位装置、软钢阻尼器以及竖齿摇摆支座等组成,所有部件均通过高强螺栓相连,便于施工和震后对受损部件更换。SCVT-SW体系的工作原理是:在地震过程中,由墙体两侧的竖向碟簧复位装置提供墙体摇摆复位弯矩,软钢阻尼器消耗地震能量,竖齿摇摆支座在提供水平抗剪能力并将墙体受到的水平作用力传递到墙体基础的同时起到固定铰支座的作用。理论分析给出了SCVT-SW体系中墙体截面的正截面承载力计算公式。通过非线性数值模拟,对新型剪力墙与普通剪力墙的受力性能进行了对比,设计了9组不同工况的对比参数。结果表明:与普通剪力墙相比,SCVT-SW骨架曲线没有明显下降段,残余变形更小;SCVT-SW体系的正截面承载力随着墙角两侧碟簧装置的预压力的增大而提高,最大提升27.8%;残余变形随碟簧装置刚度增大而减小,工况7比工况5减小了19.4%,工况8比工况5减小了46.9%,因此通过增大碟簧装置预压力与碟簧装置刚度来减小SCVT-SW的残余变形,提高复位能力的效果是显著的。

基于剪力比的自复位支撑结构体系主体框架设计

为了解决自复位支撑结构体系中支撑与主体框架的匹配性问题,提出一种基于剪力比的自复位支撑结构体系主体框架初步设计方法。根据不同的复位比和剪力比,设计了多组SCBRB钢框架结构,通过结构模型的反应谱分析和弹性时程分析,确定了剪力比的合理取值范围和主体钢框架弹性层间位移角限值的建议取值。研究结果表明,剪力比的合理取值范围为0.3~0.5;当剪力比为0.3、0.4、0.5时,主体钢框架弹性层间位移角限值的建议取值分别为1/263、1/238、1/217。

重大改建船的原船重量重心分布推算

文章以“海州湾之星”改建船为例,演算了如何在没有初始重量重心分布的情况下,利用静力学原理推算原船重量重心分布的方法,并利用该方法得到原船空船重量重心分布,核算了改建后船舶的总纵强度,并取得船级社的认可,可为同行提供借鉴。

扭转梁悬架性能影响因素分析

为了准确研究扭转梁悬架的设计参数与悬架和整车性能的关联性,分析了扭转梁悬架性能的影响因素.建立了扭转梁悬架刚柔耦合模型,详细分析了扭梁开口方向、布置位置、扭转刚度对悬架K&C的影响并仿真计算得到K&C特性指标与上述参数的非线性关系.总结了悬架性能指标极值情况及设计参数对悬架性能指标影响的显著性.根据双轨车辆运动模型,分析了扭梁开口角度与转向时悬架侧倾特性、左右车轮载荷转移及侧偏角的关系.探明了扭梁开口角度、侧倾中心高度和侧倾角刚度对整车转向特性影响的内在机理.仿真得到稳态及瞬态操稳性能指标与扭梁开口角度在整个设计空间的非线性关系曲线.结果表明:在扭梁开口向下75°左右时,车辆的稳态、瞬态响应特性指标均达到较优.

0808号台风凤凰前部龙卷的环境场和雷达回波分析

用多普勒天气雷达、常规观测和地面加密观测资料对2008年7月29—30日发生在江苏的台风凤凰前部系列龙卷过程进行了详细分析。结果如下:该龙卷发生在台风前部风切变区里,低空较强的垂直风切变、极不稳定的大气层结和深厚的正涡度区,为龙卷的发生提供了热力和动力条件。龙卷回波的反射率因子特征表现为最大反射率因子梯度位于回波的后侧,一般都有弱回波区和后侧入流缺口相伴随。东台龙卷产生于飑线型弓形回波的顶点,具有相对较大的反气旋性切变。高邮龙卷中低层具有弱的气旋性涡旋,宝应龙卷回波的内部环流特征明显,有明显的中气旋结构。在业务工作中,强回波质心高度和垂直累积液态含水量的骤降、径向速度风场中气旋性涡旋的迅速发展是对龙卷的提前警戒很好的参考指标。

可恢复功能剪力墙结构研究进展

近年来,可恢复功能结构逐渐成为了抗震工程研究的热点。可恢复功能剪力墙,主要包括:配合框架结构同时使用的摇摆或自复位剪力墙,通过摇摆减轻地震作用的破坏,通过自重或施加预应力使结构复位;应用于剪力墙结构中的可更换剪力墙,通过对破坏部位的更换实现结构功能的快速恢复。介绍了自复位剪力墙结构,摇摆剪力墙结构及可更换剪力墙结构的相关研究进展,对研究领域的成果和不足进行了总结,并指出研究领域中存在的空白。

基于灵敏度分析的某扭力梁悬架的优化

根据材料力学原理推导出某扭力梁悬架横梁的剪切中心,结合空间解析几何变换公式,建立悬架运动学方程并对悬架结构参数进行优化,利用偏导数法分析得出悬架结构参数对悬架性能的影响程度,通过分析灵敏度,找出对K特性影响最灵敏的参数,并对其进行修改,实现悬架性能的优化。最后结合有限元模型验证了剪切中心的准确性,同时利用ADAMS软件和实验对数学模型的可靠性进行验证。

底部铰支自复位钢筋混凝土剪力墙设计与性能研究

为克服传统钢筋混凝土剪力墙在遭受较大地震时易发生墙脚压溃形成塑性铰等问题,减小结构残余位移,提出一种底部铰支自复位钢筋混凝土剪力墙。通过将传统剪力墙破坏严重的底部进行替换,上部墙板通过V型连接梁与基础铰接,两侧墙脚位置处布置具有双线性滞回特性的复位支撑,将墙板传递的内力解构,弯矩由复位支撑单独承受,在墙体底部形成弹性旋转约束的方式,实现了剪力墙较大弹性侧移,从而降低墙体损伤和残余位移。数值模拟分析了普通钢筋混凝土剪力墙(SW)和相同截面的自复位钢筋混凝土剪力墙(SC-SW)在低周往复荷载下的承载能力、耗能能力、变形能力及损伤分布。结果表明:SC-SW通过合理设计可达到与SW相同初始刚度和承载力,同时延性提高了26.52%;损伤水平明显小于SW,避免了以墙体塑性受损而吸收能量的耗能方式;残余位移明显减少,复位效果较好。

具有复位功能的钢筋混凝土剪力墙设计与性能研究

为减轻混凝土剪力墙墙脚处的严重破坏,提高混凝土结构延性并控制震后残余变形,提出一种具有复位功能的钢筋混凝土剪力墙。该自复位剪力墙(SC-SW)通过两侧墙脚设置的碟簧装置提供复位力,利用墙体自身变形耗散地震能量。基于相同的几何尺寸和配筋以及相似的加载规则,建立普通钢筋混凝土剪力墙SW1和自复位剪力墙SC-SW有限元模型,对比分析两者的承载能力,耗能能力及变形能力。结果表明,SC-SW的承载能力略高于SW1,累积滞回耗能大于SW1,并且SC-SW的延性性能相比SW1提高约40.95%。新型SC-SW墙脚处放置碟簧装置可提供必要的抗侧刚度减轻墙脚的破坏,并提供较好的复位能力,能基本消除构件的残余变形,使结构在地震后具有可恢复的功能。