SMA阻尼器偏心结构平-扭震动控制试验研究

为了验证提出的新型筒式自复位形状记忆合金阻尼器(telescopic recentering shape memory al-loy damper,TRSMAD)对结构平动-扭转耦联振动反应的抑制作用,进行了偏心结构消能减震体系的振动台试验。设计了一个1/4缩尺的三层两跨单向偏心的钢框架模型,将提出的新型SMA阻尼器安装在结构底层的一侧,通过振动台分别对无控条件下和装有阻尼器的有控条件下的结构反应进行了研究。试验结果表明:(1)在各地震波作用下,TRSMAD对结构的平动反应有很好控制效果,而对结构各层扭转角位移的控制效果稍低;(2)不同地震波下的控制效果有所不同:对结构的平动位移而言,天津波的减震率最高,El Centro波次之,最后为Taft波;对结构扭转角的控制,平均而言,除了天津波作用下第二层为特例外,对El Centro波的减震效果最好,其次为Taft波,最后为天津波;(3)同一地震波下,阻尼器对结构模型一层的位移控制效果较其他层为优。     

仿自然鱼道整体物理模型试验研究

仿自然鱼道不仅能满足多种鱼类的洄游需要,同时还增加了河道内鱼类生境的数量与多样性,近来越来越受到人们的重视。由于仿自然鱼道结构复杂,断面型式多变、边坡及底部材质粗糙,糙率估算困难等,目前尚无完善的研究方法。结合新干枢纽仿自然鱼道工程,建立了1∶12的整体物理模型试验,对鱼道初步设计方案的水流条件进行了论证。结果表明,采用常规鱼道的研究方法控制鱼道内底坡、底宽、池室长度、偏移率和透水率等参数,然后通过整体物理模型试验进行验证和优化,可有效地用于指导仿自然鱼道的设计。与常规鱼道相比,仿自然鱼道受断面型式及建造材料的尺寸误差等影响,鱼道线路内流速差异明显。特别是鱼道转弯段,偏移率受弯道影响,流速易出现较直线段高或低的情况。研究成果为工程的设计提供了参考依据,同时为仿自然鱼道的设计和研究提供了参考。     

基于震源机制解资料的辽宁地区现今构造应力场

近年来,辽宁测震台网不断完善,为通过地震震源机制求解构造应力场提供了比以往更加良好的数据基础。收集并筛选出Global CMT和国内学者文章中1976—2015年、共228份震源机制资料,根据震级大小的不同,对数据赋予相应权重,使用全局网格搜索算法,反演辽宁地区现今构造应力场并给出其不确定范围。研究结果表明:辽宁地区主压应力轴为NEE向,主张应力轴以NNW向为主,在辽西隆起区为近南北向展布;近于1的应力形因子反映出由于西太平洋板块对亚欧板块的NWW向俯冲,导致上地幔软流圈上隆,使辽宁地区整体上处于拉张的应力状态。研究结果及所揭示的构造特征,可对后续研究辽宁地区的地震孕育机制和动力学过程提供参考。     

Computing Streamfunction and Velocity Potential in a Limited Domain of Arbitrary Shape. Part II: Numerical Methods and Test Experiments

Built on the integral formulas in Part I,numerical methods are developed for computing velocity potential and streamfunction in a limited domain.When there is no inner boundary(around a data hole) inside the domain,the total solution is the sum of the internally and externally induced parts.For the internally induced part,three numerical schemes(grid-staggering,local-nesting and piecewise continuous integration) are designed to deal with the singularity of the Green’s function encountered in numerical calculations.For the externally induced part,by setting the velocity potential(or streamfunction) component to zero,the other component of the solution can be computed in two ways:(1) Solve for the density function from its boundary integral equation and then construct the solution from the boundary integral of the density function.(2) Use the Cauchy integral to construct the solution directly.The boundary integral can be discretized on a uniform grid along the boundary.By using local-nesting(or piecewise continuous integration),the scheme is refined to enhance the discretization accuracy of the boundary integral around each corner point(or along the entire boundary).When the domain is not free of data holes,the total solution contains a data-hole-induced part,and the Cauchy integral method is extended to construct the externally induced solution with irregular external and internal boundaries.An automated algorithm is designed to facilitate the integrations along the irregular external and internal boundaries.Numerical experiments are performed to evaluate the accuracy and efficiency of each scheme relative to others.     

A new indicator of elastic spectral shape for the reliable selection of ground motion records

How to select a limited number of ground motion records (GMRs) is an important challenge for the non‐linear analysis of structures. Since epsilon (ε_Sa) is an indicator of spectral shape, which has a significant correlation with the non‐linear response of a structure, the selection of GMRs based on the hazard‐related target ε_Sa is a reasonable approach. In this paper, an alternative indicator of spectral shape is proposed, which results in a more reliable prediction of the non‐linear response for the structures with the natural period of 0.25 to 3.0 s. This new parameter, named eta (η), is a linear combination of ε_Sa and the peak ground velocity epsilon (ε_PGV). It is shown that η, as a non‐linear response predictor, is remarkably more efficient than the well‐known and convenient parameter ε_Sa. The influence of η‐filtration in the collapse analysis of an eight‐story reinforced concrete structure with special moment‐resisting frames was studied. Statistical analysis of the results confirmed that the difference between ε‐filtration and η‐filtration can be very significant at some hazard levels. In the case of this structure, the resulting annual frequency of collapse was found to be lower in the case of η‐based record selection, in comparison with the ε‐based record‐selection approach. Copyright © 2011 John Wiley & Sons, Ltd.     

Effectiveness of superelastic bars for seismic rehabilitation of clay‐unit masonry walls

This paper presents the results on shaking table tests of half‐scale brick walls performed to investigate the effectiveness of newly developed Cu–Al–Mn superelastic alloy (SEA) bars in retrofitting of historical masonry constructions. Problems associated with conventional steel reinforcing bars lie in degradation of stiffness and strength, or pinching phenomena, under cyclic loading, and presence of large residual cracks in structures during and after intense earthquakes. This paper attempts to resolve the problems by applying newly developed Cu–Al–Mn SEA bars, characterized by large recovery strain, low material cost, and high machinability, as partial replacements for steel bars. Sets of unreinforced, steel reinforced, and SEA‐reinforced specimens are subjected to scaled earthquake excitations in out‐of‐plane direction. Whereas steel‐reinforced specimens showed large residual inclinations, SEA‐reinforced specimens resulted in stable rocking response with slight residual inclinations. Corresponding nonlinear finite element (FE) models are developed to simulate the experimental observations. The FE models are further used to examine the sensitivity of the response with respect to the variations in experimental conditions. Both the experimental and numerical results demonstrate the superiority of Cu–Al–Mn SEA bars to conventional steel reinforcing bars in avoiding pinching phenomena. Copyright © 2012 John Wiley & Sons, Ltd.     

On the modified groundwater flow equation: analytical solution via iteration method

To take into account the variability of the medium through which the groundwater flow takes place, we presented the groundwater flow equation within a confined aquifer with prolate coordinates. The new equation is a perturbed singular equation. The perturbed parameters is introduced and can be used as accurately replicate the variability of the aquifer from one point to another. When the perturbed parameter tends to zero, we recover the Theis equation. We solved analytically and iteratively the new equation. We compared the obtained solution with experimental observed data together with existing solutions. The comparison shows that the modified equation predicts more accurately the physical problem than the existing model. Copyright © 2015 John Wiley & Sons, Ltd.     

山西代县地震台前兆数字化形变观测资料异常特征研究

结合2010年至2011年国外发生的M〉6．0、山西地区4．0级以上地震,对山西代县地震台数字化形变观测资料进行系统研究,分析其映震情况和映震特征。研究发现,在多次中强以上地震前几小时至几天左右,各测项均记录到固体潮畸变、高频脉冲、抖动、转折等异常形态。     

山西河津4．8级地震临汾地震台数字形变资料异常特征及同震响应分析

文章对山西河津4．8级地震前后临汾地震台各形变资料异常变化特征及同震响应的差异性进行分析,结果表明,震前各仪器观测资料均存在明显的异常,由于仪器频率响应范围的差异性,各仪器对同一地震的响应也存在显著不同。     

A new isolation device using shape memory alloy and its application for long-span structures

The key points to consider in determining the effectiveness of using structural isolation with shape memory alloys (SMA) are the constitutive model, the SMA isolation device and the analysis method. In this paper, a simplifi ed constitutive model based on the classic theory of plasticity is proposed to simulate the behavior of the superelasticity of the SMA, in which the martensite volume fraction is considered as one of the state variables. Comparisons between simulation results and experimental results ar...