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131.
基于位移设计的钢筋混凝土桥墩抗震性能试验研究(Ⅰ):拟静力试验 总被引:2,自引:0,他引:2
通过拟静力试验研究了基于位移设计钢筋混凝土桥墩的抗震性能。利用基于位移抗震设计方法和桥梁抗震规范方法设计了各2根和1根1:2.5比例钢筋混凝土桥墩试件,对低周反复荷载作用下试件试验破坏形态、承载力、位移延性、滞回耗能、刚度退化等方面进行了比较分析,可以认为基于位移设计的钢筋混凝土桥墩能够达到预期的延性抗震要求,并且在相对耗能能力(与理想弹塑性模型相比)、刚度退化性能方面与现行规范抗震设计方法设计的桥墩相当。试验表明建议的钢筋混凝土桥墩基于位移的抗震设计方法是实际可行的。 相似文献
132.
The peer‐to‐peer (P2P) Internet online hybrid test system has been developed for the seismic simulation of a structure. In this study, the stability and accuracy of the system are investigated analytically by studying the spectral radius of the recursive matrix of the test scheme featuring a two‐round quasi‐Newton test scheme. The applicability of the system is further examined by exploring the seismic responses of a complex structure, a steel‐encased reinforced concrete (SRC) structure with a steel tower on the top. The structure is divided into two numerical substructures and one tested part for hybrid test. The numerical substructures are simulated by sophisticated finite element method (FEM) models with material nonlinearities to capture local plastifications. Two types of FEM programs, namely OpenSEES and ABAQUS, which are suitable for the SRC part and the steel tower, respectively, are employed. The results demonstrate that the P2P system is able to simulate complex structures with significant nonlinearities. As compared with the previous study in which two elastic numerical substructures were considered, increase in the number of iterations in this study is not significant, because the associated nonlinearities are limited due to the small time interval adopted in the test. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
133.
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??????VRS???????????????????????????????????????????????????????????????3 cm??????Ч?????????????????????????Ч??? 相似文献
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M. van der Klis 《Astronomische Nachrichten》2005,326(9):798-803
Aspects of QPOs in the X‐ray flux of low mass X‐ray binaries are reviewed, with particular attention to the comparison between the QPOs in black holes and those in neutron stars. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
136.
“98.7”暴雨β中尺度低涡生成发展结构演变:双向四重嵌套网格模拟 总被引:18,自引:0,他引:18
用非静力中尺度模式MM5.V3全物理湿过程和双向四重嵌套网格技术及四维资料同化分析张弛方法,对1998年7月20~22日(简称"98.7")鄂东武汉沿江地区特大暴雨进行了36 h数值模拟,结果大大改进了原二重和三重嵌套网格的模拟,特别是水平分辨率为2 km的嵌套子域D04能更正确地模拟出暴雨的落区及雨强中心,进而揭示了强暴雨β中尺度系统发生和发展的结构及演变. 其主要结果包括(1)β中尺度切变线在鄂东沿江低空强烈发展及辐合中心的出现与其β中尺度低涡的形成和发展直接关联.(2)β中尺度切变线强烈发展的垂直结构强辐合层和强辐散层复式迭置并与强上升运动耦合发展;强涡度层和强位涡度层与强辐合层互伴发展;低空湿位温中心与中空饱和水汽带共存.(3)β中尺度低涡生成的垂直结构散度和上升运动均呈双支柱状发展;涡度和位涡度均呈单支柱状发展;高湿能柱呈双支耦合发展,水汽通道呈阶梯斜升状.(4)β中尺度低涡发展的垂直结构V字型散度柱和上升运动柱互耦发展;涡度和位涡度呈双支柱状;双支高湿能柱强烈发展,阶梯斜升水汽通道变宽增厚.至此低涡发展达最强,其结构具有典型性.模拟结果还指出,发展时空分辨率更高的多重嵌套网格模拟技术和应用四维资料同化方法,将有助于更细致的了解β中尺度强对流系统发生和发展的结构及其演变,并能进一步提高对暴雨落区及雨强的预报水平. 相似文献
137.
Evgueni T. Filipov Jessica R. Revell Larry A. Fahnestock James M. LaFave Jerome F. Hajjar Douglas A. Foutch Joshua S. Steelman 《地震工程与结构动力学》2013,42(9):1375-1394
Modern highway bridges in Illinois are often installed with economical elastomeric bearings that allow for thermal movement of the superstructure, and steel fixed bearings and transverse retainers that prevent excessive movement from service‐level loadings. In the event of an earthquake, the bearing system has the potential to provide a quasi‐isolated response where failure of sacrificial elements and sliding of the bearings can cause a period elongation and reduce or cap the force demands on the substructure. A computational model that has been calibrated for the expected nonlinear behaviors is used to carry out a parametric study to evaluate quasi‐isolated bridge behavior. The study investigates different superstructure types, substructure types, substructure heights, foundation types, and elastomeric bearing types. Overall, only a few bridge variants were noted to unseat for design‐level seismic input in the New Madrid Seismic Zone, indicating that most structures in Illinois would not experience severe damage during their typical design life. However, Type II bearing systems, which consist of an elastomeric bearing and a flat PTFE slider, would in some cases result in critical damage from unseating at moderate and high seismic input. The sequence of damage for many bridge cases indicates yielding of piers at low‐level seismic input. This is caused by the high strength of the fixed bearing element, which justifies further calibration of the quasi‐isolation design approach. Finally, the type of ground motion, pier height, and bearing type were noted to have significant influence on the global bridge response. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
138.
139.
M. A. Abramowicz D. Barret M. Bursa J. Hork W. Klu
niak P. Rebusco G. Trk 《Astronomische Nachrichten》2005,326(9):864-866
Double peak kHz QPO frequencies in neutron star sources varies in time by a factor of hundreds Hz while in microquasar sources the frequencies are fixed and located at the line ν 2 = 1.5ν 1 in the frequency‐frequency plot. The crucial question in the theory of twin HFQPOs is whether or not those observed in neutron‐star systems are essentially different from those observed in black holes. In black hole systems the twin HFQPOs are known to be in a 3:2 ratio for each source. At first sight, this seems not to be the case for neutron stars. For each individual neutron star, the upper and lower kHz QPO frequencies, ν 2 and ν 1, are linearly correlated, ν 2 = Aν 1 + B , with the slope A < 1.5, i.e., the frequencies definitely are not in a 1.5 ratio. In this contribution we show that when considered jointly on a frequency‐frequency plot, the data for the twin kHz QPO frequencies in several (as opposed to one) neutron stars uniquely pick out a certain preferred frequency ratio that is equal to 1.5 for the six sources examined so far. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
140.