Nonlinear earthquake analysis of high arch dam–water–foundation rock systems     

Jin‐Ting Wang  Chu‐Han Zhang  Feng Jin 《地震工程与结构动力学》2012,41(7):1157-1176

A nonlinear finite element model for earthquake response analysis of arch dam–water–foundation rock systems is proposed in this paper. The model includes dynamic dam–water and dam–foundation rock interactions, the opening of contraction joints, the radiation damping of semi‐unbounded foundation rock, the compressibility of impounded water, and the upstream energy propagating along the semi‐unbounded reservoir. Meanwhile, a new equivalent force scheme is suggested to achieve free‐field input in the model. The effects of the earthquake input mechanism, joint opening, water compressibility, and radiation damping on the earthquake response of the Ertan arch dam (240 m high) in China are investigated using the proposed model. The results show that these factors significantly affect the earthquake response of the Ertan arch dam. Such factors should therefore be considered in the earthquake response analysis and earthquake safety evaluation of high arch dams. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Cotidal charts and tidal power input atlases of the global ocean from TOPEX/Poseidon and JASON-1 altimetry   总被引：1，自引：0，他引：1  

WANG Yihang  FANG Guohong  WEI Zexun  WANG Yonggang  WANG Xinyi  XU Xiaoqing 《海洋学报(英文版)》2012,31(4):11-23

The global distributions of eight principal tidal constituents, M₂ , S₂ , K₁ , O₁ , N₂ , K₂ , P₁ , and Q₁ , are derived using TOPEX/Poseidon and JASON-1（T/P-J） satellite altimeter data for 16 a. The intercomparison of the derived harmonics at 7000 subsatellite track crossover points shows that the root mean square （RMS） values of the tidal height differences of the above eight constituents range from 1.19 cm to 2.67 cm, with an average of about 2 cm. The RMS values of the tidal height differences between T/P-J solutions and the harmonics from ground measurements at 152 tidal gauge stations for the above constituents range from 0.34 cm to 1.08 cm, and the relative deviations range from 0.031 to 0.211. The root sum square of the RMS differences of these eight constituents is 2.12 cm, showing the improvement of the present model over the existing global ocean tidal models. Based on the obtained tidal model the global ocean tidal energetics is studied and the global distribution of the tidal power input density by tide-generating force of each constituent is calculated, showing that the power input source regions of semidiurnal tides are mainly concentrated in the tropical belt between 30 S and 30 N, while the power input source regions of diurnal tides are mainly concentrated off the tropic oceans. The global energy dissipation rates of the M₂ , S₂ , K₁ , O₁ , N₂ , P₁ , K₂ and Q₁ tides are 2.424, 0.401, 0.334, 0.160, 0.113, 0.035, 0.030 and 0.006 TW, respectively. The total global tidal dissipation rate of these eight constituents amounts to 3.5 TW.  相似文献   

斜压海洋能量传递对风场的响应     

陈维亮  吴德星  陈学恩 《中国海洋大学学报(自然科学版)》2012,42(5):7-13

风是海水运动的重要动力因素,也是海洋内部的主要能量来源.本文在应用陆架海洋模式HAMSOM对东中国海海水运动进行数值模拟的基础上,通过傅里叶变换、旋转谱分析等研究方法,对风向海洋的能量输运进行研究.研究结果显示,风场向海洋输运的最有效途径是风杨扰动量与流场扰动量的相互作用;惯性能量主要来源于海洋表层,由风场提供,向下传递;而潮频率能量大部分来自海底的内潮与底地形相互作用,向上传递.  相似文献   

外源氮输入对沼泽湿地小叶章枯落物性质及其早期分解的影响   总被引：6，自引：0，他引：6  

刘德燕  宋长春 《湿地科学》2008,6(2)

在三江平原沼泽湿地,选取典型湿地植物小叶章(Calamagrostis angustifolia)为研究对象,对比研究了连续施氮[24g/(m2·a)]3a的小叶章立枯物(N24)与自然条件下形成的立枯物(CK)的差异;并采用分解袋法对此2种小叶章枯落物的早期分解过程进行了研究。结果表明,施氮处理下小叶章立枯物的氮、磷含量均高于CK,但碳含量显著降低(n=3,p<0.05)。施氮处理下形成的小叶章枯落物的分解速率明显大于CK,分解160d后两者的失重率分别为初始值的31.13%(N24)和28.50%(CK)。分解过程中,2种处理下枯落物有机碳的绝对含量都表现为净损失;其氮、磷浓度的变化趋势大致相同,分解160d后均发生了氮、磷的净释放,其中,N24的氮、磷净释放量分别是CK的64.91和2.11倍。外源氮输入影响下小叶章枯落物C/N和C/P值的降低,加快了该枯落物的分解速率,从而影响土壤有机质的累积和CO2的排放;而该枯落物分解过程中营养元素释放量的增大,还可能会影响土壤其它营养元素可利用性。  相似文献   

Prediction of input energy spectrum: attenuation models and velocity spectrum scaling          下载免费PDF全文

F. S. Alıcı  Halûk Sucuoğlu 《地震工程与结构动力学》2016,45(13):2137-2161

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Response of the Fatih Sultan Mehmet Suspension Bridge under spatially varying multi-point earthquake excitations     

《Soil Dynamics and Earthquake Engineering》2016

The study aims at investigating the structural behavior of the Fatih Sultan Mehmet Suspension Bridge, i.e. the second Bosphorus Bridge in Turkey, under multi-point earthquake excitations, and determining the earthquake performance of the bridge based on the results obtained from this analysis. For this objective, spatially varying ground motions in triple direction were produced for each support of the bridge considering the Mw=7.4 scenario earthquakes on the main Marmara Fault. In order to simulate the ground motions, modified stochastic finite-fault technique was utilized. Taking the ground motions into account, non-linear time-history analysis was carried out, and the results obtained from the analysis were compared to those from uniform support earthquake excitation to identify the effects of multi-point earthquake excitations on the seismic performance of the bridge. From the analysis, it was determined that modal response of the towers and the deck was mostly effective on dynamic response of the entire bridge rather than other structural elements, such as cable and approach viaduct. Compared to the results obtained from simple-point earthquake excitation, noticeable axial force increase in the cable elements was obtained under multi-point earthquake excitation. The changes at the main cable and the side span cable were determined as 21% and 18%, respectively. This much increase in the cable elements led to increase in axial force at the towers and in shear force at the base section of the tower column. These changes in the structural elements were closely related to response of the deck and the towers since they had considerable contribution to response of the entire bridge. Based on the findings from the study, spatially varying ground motions has to be considered for long span suspension bridges, and the multi-support earthquake analysis should be carried out for better understanding and obtaining reliable results necessary for retrofitting and performance evaluation.  相似文献   

Neural network prediction of bed material load transport     

Bimlesh Kumar 《水文科学杂志》2013,58(5):956-966

Abstract

Bed material load, which comprises bed load and suspended load, has been extensively studied in the past few decades and many equations have been developed, but they differ from each other in derivation and form. If a process can be related to various flow conditions on a general basis, a proper understanding of bed material load movement can be ascertained. As the process is extremely complex, obtaining a deterministic or analytical form of it is too difficult. Neural network modelling, which is particularly useful in modelling processes about which knowledge of the physics is limited, is presented here as a complimentary tool for modelling bed material load transport. The developed model demonstrated a superior performance compared to other traditional methods based on different statistical criteria, such as the coefficient of determination, Nash-Sutcliffe coefficient and discrepancy ratio. The significance of the different input parameters has been analysed in the present work to understand the influence of these parameters on the transport process.

Editor D. Koutsoyiannis

Citation Kumar, B., 2012. Neural network prediction of bed material load transport. Hydrological Sciences Journal, 57 (5), 956–966.  相似文献   

基于等效单自由度体系的结构地震输入能量的研究     

杜敏  林玮  郭晓云 《地震工程与工程振动》2011,31(3):77-82

通过对多自由度体系结构在地震作用下的能量分析,考虑地震动因素和结构自身特性,提出一种框架结构地震总输入能量的简化求解方法.实例计算结果表明:基于等效单自由度体系来估计多自由度体系的地震总输入能,是一种计算简便且较为准确的方法.  相似文献   

江西鄱阳湖地区土壤酸化与人为源氮的关系   总被引：4，自引：0，他引：4  

文帮勇  杨忠芳  侯青叶  杨晓燕  尹国胜  衷存堤 《现代地质》2011,25(3):562-568

江西鄱阳湖地区是我国土壤酸化严重的地区之一,对比研究区多目标区域地球化学调查与第二次土壤普查资料发现,研究区土壤酸化趋势严重,强酸性土壤占研究区面积比例由58.22%上升到78.44%;赣江、抚河水系入湖区和饶河流域表层土壤酸化明显。研究区因施肥、大气干湿沉降和灌溉输入到农田的氮素分别为123.84 kg.hm-.2a-1、74.13 kg.hm-.2a-1、11.02 kg.hm-.2a-1。研究区因人为氮带入农田的H+为18.67 kmol.hm-.2a-1。化肥氮是引起土壤酸化的主控因素,氮沉降也是影响土壤酸化的主要因素之一。土壤pH与氮含量呈较差负相关,说明土壤中的有机氮对土壤酸化作用有限,增施有机肥和复合肥,适当减少氮肥,特别是铵态氮肥的比例,可以补充盐基物质的相对不足,达到缓解土壤酸化的作用。土壤pH与钙含量呈极显著正相关,适量增施含钙物质可以有效地防止表层土壤酸度降低。  相似文献   

国外海洋渔业准入制度的实践分析   总被引：1，自引：0，他引：1  

唐建业 《广东海洋大学学报》2011,31(2):1-6

捕捞生产的准入是进行海洋渔业资源有效管理的必要条件。综合相关国家渔业管理发展过程,准入制度可能有三种类型:初步准入制度、投入型准入制度和产出型准入制度。准入的对象涉及渔船、渔获及渔具等。从实践经验看,在渔船数量扩展前,建立有效的准入制度的成功概率相对较大;如果现有的捕捞能力已经远超过渔业资源的承载能力时,投入型准入制度虽然还是十分重要,但在削减捕捞能力方面作用有限;产出型准入制度在一些国家的渔业实践中取得了一定的成功,但存在着诸如总可捕量控制、监测与执法等方面的问题。总体上,捕捞权利与捕捞许可证流转等是实施准入制度过程中应给予关注的两个事项。我国可在现行的捕捞许可证与船网工具指标制度的基础上完善我国投入型准入制度,将渔具纳入管理;在条件成熟的情况下,可适当过渡实施产出型准入制度。  相似文献