A damage-based definition of effective peak acceleration     

Biswajit Basu  Vinay K. Gupta 《地震工程与结构动力学》1998,27(5):503-512

This paper presents a rational basis for obtaining the Effective Peak Acceleration (EPA) of a given ground motion process. The proposed formulation considers the statistical variability in the ground motion, and is centred on the idea of explicitly linking EPA with expected cumulative damage in the structures due to the inelastic excursions. The structural behaviour has been modelled by a Single-Degree-Of-Freedom (SDOF) bilinear hysteretic oscillator. EPA is considered to be the expected PGA of a scaled ground motion process such that this oscillator undergoes a specified expected damage under the unscaled process if it is linearly designed for the scaled process. For estimation of the damage, the oscillator has been replaced by an equivalent linear oscillator through stochastic averaging. A parametric study has been carried out to investigate the dependence of EPA on several governing parameters, and it has been shown that despite the strong dependence of EPA on oscillator time period, it may be possible to obtain ‘period-averaged’ EPA values for several ground motion processes for engineering applications. © 1998 John Wiley & Sons, Ltd.  相似文献   

Inelastic seismic response of one-way plan-asymmetric systems under bi-directional ground motions     

Mario De Stefano  Giuseppe Faella  Roberto Ramasco 《地震工程与结构动力学》1998,27(4):363-376

The static design requirements of some seismic codes, such as the Eurocode 8 and—in most cases—the Uniform Building Code, to allow for the effects of earthquake excitation acting in a direction other than the principal axes of the structure do not apply to one-way asymmetric systems. Therefore, with some exceptions, no specific provisions are considered for such systems to cover effects of structural asymmetry on the behaviour of elements located along the symmetric system direction. Aimed towards fulfilling this need, in this paper, a wide parametric study of the inelastic response of one-way asymmetric systems designed according to Uniform Building Code is carried out, considering two-component earthquake excitations. The analyses show that the maximum ductility demands on elements aligned along the asymmetric system direction are very close to, and even lower than, those obtained for symmetric reference systems. Conversely, the symmetric direction elements undergo significantly larger inelasticity than if they were located in symmetric reference systems. Subsequently, the overstrength needed by the symmetric direction elements to prevent such additional ductility demands for several stiffness and plan configurations is quantified. It is concluded that one-way asymmetry should be considered by seismic codes as an intrinsic system property, thus implying that specific provisions should be included for designing elements located along the symmetric system direction, in addition to those currently subscribed to design the asymmetric direction elements. © 1998 John Wiley & Sons, Ltd.  相似文献   

利用卫星遥感和再分析数据刻画2017-2018年格陵兰北部罕见冰间湖事件     

雷瑞波  桂大伟  袁卓立  庞小平  陶丁  翟梦茜 《海洋学报(英文版)》2020,39(9):5-17

以90%海冰密集度为阈值,基于卫星遥感数据,2017-2018年冰季在格陵兰北部识别了两次冰间湖事件,分别出现在冬季和夏季。冬季的冰间湖事件从2018年2月20日持续至3月3日,夏季的事件从8月2日持续到9月5日。AMSR2被动微波的海冰密集度产品表明,冬季和夏季冰间湖事件对应的最低海冰密集度分别为72%和65%。两次冰间湖事件都与格陵兰北部东西气压梯度异常引起的南风加强有关,而气压梯度的异常则与对流层中部极涡的扰动有关。冬季冰间湖事件期间,相对暖和的气温和频繁出现的冰间湖,导致冬季海冰生长不持续,海冰热力增厚较小,这为夏季海冰发生破碎并形成冰间湖创造了条件。南风减弱和新冰生成是冬季冰间湖消失的主要原因。对于夏季的冰间湖,导致其消失的主要原因则是从北部输入的浮冰增加。Sentinel-1 合成孔径雷达产品相对AMSR2被动微波观测产品更加适合于应用到冰间湖事件伴随的新冰生长,这与前者具有更高的空间分辨率有关。格陵兰北部是北冰洋多年冰的聚集地,该区域被认为是北冰洋海冰的“避难所”。因此区域在2017-2018年出现罕见的冰间湖事件,对于整个北冰洋海冰的快速减少具有重要意义,也助于北冰洋海冰,尤其是多年冰的消退。  相似文献   

东海陆架区中尺度涡运动路径的统计特征分析          下载免费PDF全文

张桃  李君益  谢玲玲  郑少军  郑慧源 《海洋学研究》2020,38(1):77-86

基于1993—2017年卫星高度计海面高度异常中尺度涡旋追踪数据集,对东海陆架区及从西北太平洋入侵东海的涡旋进行路径分类、季节变化及特征参量统计分析,并结合再分析流场资料,进行背景流场、涡度场分析。研究结果显示,近25 a,在东海追踪到318个气旋涡和276个反气旋涡。根据涡旋运动路径将其分为:东海陆架浅海生成往深海传播型(148个)、深海生成向东海陆架浅海传播型(35个)、沿等深线运动型(180个)、徘徊型(121个)、外来入侵到达东海陆架型(25个)及外来入侵到达东海深海型(85个)。6类涡旋的数量存在明显的季节分布,各个类型气旋与反气旋涡数量的季节分布也各不相同。其中,沿等深线运动型涡在春、夏季的数量高于秋、冬季。陆架浅海区生成往深海运动型涡的季节分布较为平均,气旋式涡在夏季数量最少,在春季和冬季数量较多。黑潮与涡旋数量的季节分布有关。徘徊型涡的平均生命周期最长,约为44 d;陆架浅海生成往深海运动型及外来入侵到达东海陆架的中尺度涡具有最大的平均振幅,为13.2 cm;外来入侵到达东海陆架型涡具有最大的直径,为122 km;外来入侵到达东海深海型涡在进入东海后的生命周期、振幅、直径在数值上均为最小。  相似文献   

Experimental Study of A Pile-Restrained Floating Breakwater Constructed of Pontoon and Plates   总被引：3，自引：3，他引：0  

王永学  董华洋  刘冲 《中国海洋工程》2010,24(1):183-190

A pile-restrained pontoon-plate floating breakwater is proposed in this paper.The laboratory physical-model tests are conducted to investigate the wave-dissipation property and heave-motion response of a model.The influence of the model′s geometric parameters including relative pontoon width,plate width,number of plates and pontoon draft on wave-dissipation performance and heave-motion response are discussed,as well as the correlation between these two factors.The result indicates that wave-dissipation performance of the proposed structure is better than the pontoon structure:its transmission coefficient and heave-motion height are reduced by 0.2 and 0.3,respectively,in comparison with those of the pile-restrained pontoon model at a relative pontoon width of 0.2.  相似文献   

南海北部沙波区海底强流的内波特征及其对沙波运动的影响   总被引：4，自引：0，他引：4       下载免费PDF全文

夏华永  刘愉强  杨阳 《热带海洋学报》2009,28(6):15-22

2008年3月6日至2008年4月9日, 在南海北部外陆架与陆坡上的沙波区进行了海底流速的连续观测,观测结果表明潮流与海流较弱,但时有流速达30—77cm.s-1的海底强流发生。强流方向与南海北部内波传播方向相对应,多分布在偏NW向与偏SE向。偏SE向流强于偏NW向流,与内波在传播方向上的下坡流大于上坡流的特征一致。对流速序列进行了旋转功率谱分析,结果表明,高于M2分潮的频率中,众多的振荡分量具有内波流性质,说明阵发性强流为内波所致。采用观测流速计算了沙波的移动速度,计算结果得出强流能起动海底泥沙,由于NW向传播（上坡方向）的内波导致了SE向（下坡方向）的净流动,沙波偏SE向移动,但沙波移动速度不大,小型沙波移动速度小于1.6m.a-1。采用潮流、风暴潮耦合模型计算了强台风驱动的海底流速过程,表明潮流、风暴潮耦合也能移动海底沙波,但沙波移动方向与台风路径相关,不一定为SE向,且移动距离更小,潮流、风暴潮耦合不是沙波移动的主要动力机制。  相似文献   

μ������ֽ�ؿ�ˮƽ�˶���Ӧ������   总被引：3，自引：2，他引：1  

瞿伟  张勤  王庆良  凌晴 《大地测量与地球动力学》2009,29(4):34-37

????2001??2004??GPS?????????о?μ??????????????????????????????????????????????????????????????????1)????????????????????, ?о????????????????????????????????,????μ??????в????????????????????????GPS????????????????2)???е???????-????-????-??????????????????????????,???????????????,????????????-????-????-μ???????С??????????????  相似文献   

A set of canonical problems in sloshing, Part I: Pressure field in forced roll—comparison between experimental results and SPH   总被引：1，自引：0，他引：1  

L. Delorme  A. Colagrossi  R. Zamora-Rodríguez 《Ocean Engineering》2009,36(2):168-956

In this article, impact pressure in the case of shallow water sloshing is investigated experimentally and numerically for forced rolling motion. The maximum values of impact pressures have been found for a frequency lower than the first sloshing frequency. Experimental results are compared with numerical ones obtained using smoothed particle hydrodynamics (SPH). The influence of viscosity and of density re-initialization on the SPH results are discussed. A new method for calculating the pressure on walls with SPH is presented.  相似文献   

强震地面运动超随机特性的几点注记     

徐国栋  周锡元  闫维明 《地震工程与工程振动》2007,27(1):7-15

本文详细论述了功率谱与功率谱密度、平方和SS与平方平均值MS的适用范围及物理意义,比较深入地分析了平稳和非平稳加速度时间历程的统计特征,通过引入时域包线获取特定相位的方法,考虑了非平稳特性。本文基于非平稳时间历程,在不考虑频率非平稳性的基础上,提出了设计地震动三要素:(1)平方和SS;(2)归一化自相关函数或其对应的功率谱;(3)地震动时域包线.本文提出了在设计地震动合成中考虑超随机特性的实用方法,并指出地震动的超随机特性(即归一化功率谱的锯齿状波动部分,或归一化自相关函数的随机噪声部分)与相位的随机性是地震动随机特性的两个重要方面。本文将地震动的统计分析直接建立在非平稳时间历程的基础之上,从而避开了要对地震动进行平稳化处理的困难。这样提取出的地震动统计特征完全是以真实地震动记录为基础的。应用这些统计特征,可模拟出符合统计要求的基于非平稳时间历程的设计地震动。最后本文还讨论了工程上常用的将反应谱近似转换为功率谱的转换式的一些缺陷。  相似文献   

地下结构抗震理论分析与试验研究的发展展望   总被引：5，自引：0，他引：5  

刘晶波  刘祥庆  杜修力 《地震工程与工程振动》2007,27(6):38-45

目前我国在地下结构抗震分析与破坏灾变机理研究中尚存在诸多问题需要解决,在分析总结我国地下结构抗震理论与试验研究的基础上,重点阐述了需要进一步深入研究的六个关键问题:地下结构振动模型试验研究技术,土体非线性动力本构模型,高轴压的地下结构承重构件地震破坏机理,非一致波动输入及非一致波动输入下地下结构的地震反应,饱和砂土液化大变形理论及本构模型,大型三维非线性土-结构动力相互作用分析模型。这些问题的研究和解决对于完善地下结构抗震理论分析方法与试验研究技术,获得大型地下结构在地震作用下的反应规律与破坏灾变机理具有重要的科学意义和工程应用价值。  相似文献