Inelastic buildings with tuned mass dampers under moderate ground motions from distant earthquakes

The effectiveness of tuned mass dampers (TMD) in vibration control of buildings was investigated under moderate ground shaking caused by long‐distance earthquakes with frequency contents resembling the 1985 Mexico City (SCT) or the 1995 Bangkok ground motion. The elastic–perfectly plastic material behaviour was assumed for the main structure, with linear TMDs employed by virtue of their simplicity and robustness. The accumulated hysteretic energy dissipation affected by TMD was examined, and the ratio of the hysteretic energy absorption in the structure with TMD to that without it is proposed to be used, in conjunction with the peak displacement ratio, as a supplementary TMD performance index since it gives an indication of the accumulated damage induced in the inelastic structures. For the ground motions considered, TMD would be effective in reducing the hysteretic energy absorption demand in the critical storeys for buildings in the 1.8–2.8 s range. The consequence is reduction in damage of the buildings which would otherwise suffer heavy damage in the absence of TMD, resulting in economical restorability in the damage control limit state. This is of practical significance in view of the current trend toward performance‐based design. Copyright © 2001 John Wiley & Sons, Ltd.     

Effectiveness of structural control based on control energy perspectives

A computational algorithm for maximizing the control efficiency in actively controlling the elastic structural responses during earthquake is proposed. Study of optimal linear control using a single degree of freedom shows that applying active control is very effective in reducing the structural displacement and velocity responses for long‐period structures, but at the same time it has an adverse effect in increasing the absolute acceleration response. The extent of this adverse effect reduces the effectiveness of the control system, and therefore it poses a limit on the maximum control force in order to provide maximum control efficiency. In view of this shortcoming, maximum control energy dissipation is used to define the most effective optimal linear control law. Less displacement and velocity response are expected as larger control force is applied, but there is always a limit that maximum control energy can be dissipated. This study shows that this limit depends on the structural characteristics as well as the input ground motion, and a general trend is that the maximum control energy decreases as damping increases. Finally, application of the proposed algorithm on a six‐storey hospital building is presented to show the effectiveness of using optimal linear control on a multi‐degree‐of‐freedom system from the control energy perspectives. Copyright © 2001 John Wiley & Sons, Ltd.     

The NO2 absorption spectrum. III: The 200–300 nm region at ambient temperature

Absorption cross-section measurements of NO₂ performed in our laboratory have been extended to the 200–300 nm region at ambient temperature. Low pressures have been used, limiting the effects of the dimer N₂O₄ which has an absorption cross-section from one to two orders of magnitude larger than that of NO₂ in this region. The results have been compared to those of previous authors and are now available for atmospheric purposes at 0.01 nm intervals.Unité de Recherche Associée au CNRS.     

脉冲电镀金刚石钻头试验研究

介绍脉冲电镀在人造金刚石孕镶钻头上的应用研究，探讨脉冲电镀机理，采用正交试验法优化脉冲电镀工艺参数；研制了脉冲电镀钻头，生产钻头周期缩短了３０％。在室内和野外生产试验中，发现脉冲电镀钻头较直流电镀钻头有如下优点：钻进地层适用范围广、钻进时效高。     

偏岭石及煅烧高岭石的红外光谱研究

通过对偏岭石和相应煅烧高岭石的红外光谱测定,发现偏岭石同煅烧高岭石在结构上有很大的差异。在偏岭石中不存在非晶态SiO_2相,其中Si—O_4四面体同Al—O_6八面体是相互聚合的:煅烧高岭石(600～995℃)中则不同,其中Si大部分是以独立的非晶态SiO_2相存在,而同其中的Al_2O_3相分离。偏岭石同煅烧高岭石的关系是:对偏岭石进行一定温度的煅烧,它可以转变成像煅烧高岭石一样的结构状态。     

电吸附元素异常来源及找矿模式

电吸附元素异常来源于深部矿体,主要是在各种后期地质作用下溶解了矿体中的矿质成分,并扩散迁移至地表,形成能反映矿体的电吸附晕。电吸附找矿方法在金属矿上所捕获到的异常是在矿体中心垂直投影位置以块状异常出现的称“顶部晕”。在大红山铜矿和李坝金矿上异常也反映了这种异常特征。     

半拉格朗日、半隐式欧拉方程组大气数值模式研究

介绍了一个具有较高时间积分效率的三维弹性大气数值模式。其中,控制方程为能够描述大气非静力及可压缩性的欧拉方程组,时间积分采用了高效率的“半拉格朗日、半隐式”方案。通过引用一个简化的“云物理过程”参数化方案,针对大气中深厚湿对流过程的若干问题进行了数值试验,结果表明,模式能够对该过程中的一些基本和复杂现象进行有效地模拟。试验结果还表明,动力学框架具有很好的稳定性,能够实现高效率的时间积分,它还具有较好的频散特性,保证了空间计算的精度,从而完好地描述了风暴的形态。     

The use of riparian vegetated filter strips to reduce river sediment loads: an overestimated control measure?

The spatially distributed soil erosion and sediment delivery model WATEM/SEDEM was used to simulate the impact of riparian vegetated filter strips (RVFSs) on river sediment delivery at different spatial scales. For a field plot with a straight slope, sediment reduction by the RVFSs is comparable to results obtained through experimental set‐ups elsewhere (i.e. >70%). However, at the scale of an entire catchment, sediment reduction is much less (i.e. ±20%) due to (1) overland flow convergence, which reduces the sediment trapping efficiency of an RVFS, and (2) because part of the sediment bypasses the RVFSs through ditches, sewers and road surfaces. These results suggest that, at the catchment scale, RVFSs should be accompanied with other conservation techniques that are more appropriate for reducing river sediment loads, and that also reduce on‐site soil erosion. Copyright © 2006 John Wiley & Sons, Ltd.     

基于扁铲侧胀试验的桩基水平承载力分析

依据扁铲侧胀试验的结果,对桩侧土水平抗力系数的比例系数进行了估算,并估算出单桩水平承载力设计值;根据单桩水平载荷试验的成果,计算出试验桩的水平临界荷载平均值,并得到桩侧土水平抗力系数的比例系数;在此基础上,对两者进行了对比分析,其单桩水平承载力非常接近,但比例系数存在差异。认为不宜将试桩的结果直接应用于工程桩的水平承载力计算,应根据工程桩的实际情况,考虑承台、桩群、土相互作用产生的群桩效应。