Flexural deformation capacity of rectangular RC columns determined by the CAE method

A non‐parametric empirical approach, called the conditional average estimator (CAE) method, has been implemented for the estimation of the flexural deformation capacity of reinforced concrete rectangular columns expressed in terms of the ultimate (‘near collapse’) drift. Two databases (PEER and Fardis), which represent subsets of the original databases, were used. Four input parameters were employed in the basic model: axial load index, index related to confinement, shear span index, and concrete compressive strength. The results of analyses suggest that, in general, ultimate drift decreases with increasing axial load index, and increases with better confinement. An increase in the shear span‐to‐depth ratio has a beneficial effect until a turning point is reached. After that the opposite trend can be observed, i.e. a decrease in the ultimate drift with further increasing of the shear span‐to‐depth ratio. No clear trend is observed in the case of concrete compressive strength. The predictions, obtained by using the Fardis database are in general somewhat larger than the predictions from the PEER database, due to the difference in the definition of ultimate drift. The scatter of results is large. The local coefficient of variation, which is a measure for dispersion, amounts to about 0.2–0.5. The ultimate drifts obtained by using the two databases, were compared with the values predicted by the Eurocode 8 empirical formula. Copyright © 2006 John Wiley & Sons, Ltd.     

公路隧道辅助设计软件的新思路研究

研究了现有公路隧道辅助设计软件的思路和技术特点,结合公路隧道设计过程的实际需要,提出了公路隧道辅助设计软件的新思路,即建模和出图采用参数式与交互式相结合,计算、优化与出图集成统一。这些思路已经在作者开发的公路隧道设计软件中实现,证明了技术的可行性。该软件在同济曙光软件平台上开发,具有修改、实时更新的图形建模和出图功能,结合施工过程的有限元及其它数值方法的分析计算功能,并采用遗传算法等多种优化方法对结构进行最优化设计,具有后处理显示、可视化图纸管理、图纸库等功能。该软件能使整个公路隧道设计、计算、出图在统一的环境下完成,能有效提高公路隧道设计的效率。     

基于地震活动性的强震中长期预报的三种新方法

本文介绍基于地震活动性的强震中长期预报的三种新方法，即自助统计，Ｓｏｍｐｉ谱分析及模糊时空分维。对川滇地区一些强震的震例分析检验结果表明，这三种新方法可在数年期的强震中长期预报中发挥一定的作用。     

Multiple‐tuned liquid column dampers for torsional vibration control of structures: theoretical investigation

This paper presents a theoretical investigation on the performance of multiple‐tuned liquid column dampers (MTLCD) for reducing torsional vibration of structures in comparison with single‐tuned liquid column dampers (STLCD). The analytical model is first developed for torsional vibration of a structure with an MTLCD under either harmonic excitation or white noise excitation. The experimental results are then used to verify the analytical model for coupled MTLCD‐structure systems under harmonic excitation. The performance of an MTLCD and its beneficial parameters for achieving the maximum torsional response reduction to white noise excitation are finally investigated through an extensive parametric study in terms of the distance from the centre line of the MTLCD to the rotational axis of the structure, the ratio of the horizontal length to the total length of liquid column, frequency bandwidth, head‐loss coefficient, the number of TLCD units in an MTLCD, frequency‐turning ratio and the spectral level of excitation moment. The results show that there is an optimal head‐loss coefficient and an optimal frequency bandwidth for an MTLCD to achieve the maximum torsional response reduction. It is also demonstrated that the sensitivity of an optimized MTLCD to the frequency‐tuning ratio is less than that of an optimized STLCD, and it can be further improved by increasing the bandwidth but at the cost of less torsional vibration reduction. Copyright © 2002 John Wiley & Sons, Ltd.     

Dynamic characteristics and seismic response of adjacent buildings linked by discrete dampers

Coupling adjacent buildings using discrete viscoelastic dampers for control of response to low and moderate seismic events is investigated in this paper. The complex modal superposition method is first used to determine dynamic characteristics, mainly modal damping ratio and modal frequency, of damper-linked linear adjacent buildings for practical use. Random seismic response of linear adjacent buildings linked by dampers is then determined by a combination of the complex modal superposition method and the pseudo-excitation method. This combined method can effectively and accurately determine random seismic response of non-classically damped systems in the frequency domain. Parametric studies are finally performed to identify optimal parameters of viscoelastic dampers for achieving the maximum modal damping ratio or the maximum response reduction of adjacent buildings. It is demonstrated that using discrete viscoelastic dampers of proper parameters to link adjacent buildings can reduce random seismic responses significantly. Copyright © 1999 John Wiley & Sons Ltd.     

电梯轮轨系统平面外静力本构模型及其验证

针对电梯地震破坏中的对重脱轨现象,对电梯轮轨系统的平面外接触作用力学机理进行了研究,通过对轮轨系统导靴、导轨及其支架的各个构件的深入分析,判断了它们间的作用关系。并在一定简化基础上提出了电梯轮轨系统平面外静力本构模型,给出了轮轨系统的平面外刚度公式,并通过静力试验对该模型进行了验证,通过参数化分析探究了影响电梯轮轨系统平面外作用的关键参数。     

考虑双向碰撞效应的连续斜交桥地震响应研究

为研究双向碰撞效应对连续斜交桥地震响应的影响,采用Kelvin-Voigt模型模拟桥台伸缩缝处的纵向碰撞现象,采用简化滞回模型模拟挡块与主梁的横向碰撞过程,针对某三跨连续斜交桥进行参数对比研究。研究表明,双向碰撞对主梁横向位移的影响远比纵向位移大,其中桥台间隙对主梁平面转角的影响最大,且平面转角随桥台间隙的增大而减小;横向碰撞对墩柱曲率变形的影响远比纵向碰撞大,其中挡块强度的影响特别大,当挡块强度由0%增至50%时,墩柱纵、横向曲率均值分别增大13.43倍、7.21倍。随着斜交角的增大,梁端纵向位移不断增大,横向位移和平面转角则先增后减;墩底纵向曲率不断增大,横向曲率经历先增后减\,再增的过程;纵向碰撞效应先减弱后增强,而横向碰撞效应则先增强后减弱。由于横向碰撞对墩柱的影响远大于纵向碰撞,因此在斜交角为15°～45°时,宜设法降低横向碰撞效应。     

海洋电缆弯曲加强器参数化设计与分析

为建立海洋电缆弯曲加强器参数化设计方法,使用有限元模型进行了弯曲加强器设计参数研究.基于海缆及其弯曲加强器的几何结构及受力特点,建立了基于多相耦合梁单元的平面有限元模型,可以计算并分析海缆及其弯曲加强器在一定角度的张力作用下的形变与等效应力分布.通过多个案例系统性地分析了弯曲加强器的主要设计参数,即根部直径、锥体段长度及材料弹性模量,对海缆弯曲挠度、曲率及等效应力分布的影响.文中原创性地提出了弯曲加强器组合设计参数φ(t,L,E).通过定量分析确定了其与海缆最大曲率之间的近似线性关系,并由此设计了参数化的弯曲加强器设计流程.通过设计实例验证了组合参数与海缆最大曲率之间关系的准确性和参数化设计流程的有效性.     

数字经济加剧了地区差距吗？

数字经济的兴起为实现地区协调发展提供了重要契机。基于中国284个地级市数据,通过构建传导机制考察数字经济对地区差距的直接、间接和调节效应,采用Bootstrap有调节的中介效应方法进行分析。研究表明：数字经济、制造业集聚和地区差距的空间分布均呈现“东强西弱、南强北弱”的不均衡特征;数字经济对地区差距具有负向的直接效应;数字经济通过集聚经济对地区差距发挥了显著的正向中介效应;财政科教支出在直接路径中发挥负向的调节效应,在数字经济影响集聚经济过程中发挥正向调节效应。如须在数字经济时代下缩小地区差距,既需要推广数字技术、消弭数字鸿沟,也需要完善要素流动、财政科教支出等制度性配套机制。     

参数方程法确定线路放样中边桩坐标

给出了线路放样过程中确定中边桩坐标的新方法。根据曲线模型,找出线路控制坐标系与局部坐标系坐标之间的参数方程关系,推出了缓和曲线及圆曲线中、边桩坐标的参数方程,代入已知量求得参数的值,且给出了求解步骤。该方法思路清晰,具有一次转换计算就可以实现获取线路中边桩测量坐标的优点,便于工程应用。