组合结构有限元计算存在的问题和处理方法   总被引：3，自引：0，他引：3  

朱合华  缪圆冰  梁伟  韩秋官  陆忠良 《岩土力学》2005,26(9):1437-1442

梁、板、壳等结构单元在有限元计算中使用十分广泛,但由于其几何特点,在组合结构有限元计算中,如果不正确处理,有时会给计算结果带来一定的影响。针对组合结构分析中,应力集中及几何位置简化等导致较大计算误差的情况,以地铁车站结构中常见的板梁组合结构为分析对象,从工程实用角度出发提出了相应的对策和处理方法。采用这些措施,可以在使用现有通用有限元软件进行计算的情况下,获得较符合实际的结果  相似文献   

Diurnal wind and nonlinear interaction between inertial and tidal currents in the South China Sea during the passage of Typhoon Conson   总被引：2，自引：2，他引：0  

LIU Junliang  CAI Shuqun  WANG Shengan 《海洋学报(英文版)》2014,33(5):1-7

Diurnal wind （DW） and nonlinear interaction between inertial and tidal currents near the Xisha Islands of the South China Sea （SCS） during the passage of Typhoon Conson （2010） are investigated using observational data and a damped slab model. It is found that the DWs, which are dominated by clockwise wind components, are prominent at our observational site. The DWs increase after the passage of the typhoon from 1 to about 4 m/s, which may be due to the decrease of the sea surface temperature caused by the passage of the typhoon. Kinetic energy spectra and bicoherence methods reveal nonlinear interactions between the inertial currents and the 2MK3 tidal constituent at our observational site. The slab damped model reproduces the inertial currents successfully induced by the total observed winds, and it is shown that the inertial currents induced by DWs are positively proportional to the DWs speed. Even though the observed inertial currents are distinct, the proportion of inertial currents induced by DWs to those induced by the total observed winds is just 0.7%/4% before/after the passage of typhoon. This shows that the inertial currents induced by the DWs are unimportant near the Xisha Islands during the typhoon season.  相似文献   

京沪高铁轨道板精调相关技术问题研究及对策   总被引：1，自引：0，他引：1  

徐秀川  花向红  邹勇  李程春  范晓敏 《测绘信息与工程》2011,36(1):47-49

介绍了轨道板博格精调技术,详细论述并有效改进了精调操作流程,针对精调过程中常见问题提出了解决办法,最后对轨道板的精调成果进行了简要分析。  相似文献   

一种求解地下结构顶板频率和振型的方法     

姚小彬  戚承志  陈国兴 《地震学刊》2011,(6):688-694

采用欧拉梁横向自由振动理论,发展了一种求解浅埋地下结构顶板频率和振型的方法。鉴于地下结构顶板频率求解问题的复杂性,首先将该问题假定为平面应变问题求解,推导出浅埋地下结构项板梁的自由振动方程;然后根据顶板梁的边界条件,得到了顶板梁的频率方程,从而得出了顶板梁的频率和振型;进一步得出了墙体转动刚度对顶板频率影响的规律,即转动刚度对顶板低频影响较小,对高频影响较大。还综合考虑土体刚度随埋深的变化和由于土体成拱引起的土体附加质量的变化,研究了结构顶板频率随埋深的变化。这些结果可以为地下结构的动力计算提供参考。  相似文献   

Seismic Evidence for Plume and Subducting Slab in West Yunnan, Southwestern China     

HE Chuansong 《《地质学报》英文版》2011,85(3):629-636

Western Yunnan is located within a gigantic Tethys orogenic zone between Gondwana and Laurasia. Magmatic activity records of the associated Wilson orogenic cycle show that the causes of plate spreading in the region might have been related to sub-mantle plume. Tectonics, geophysics, sedimentary strata, tectonic evolution of the lithosphere and other research results indicate that there is geological evidence for mantle plume magmatic activities in West Yunnan. Tomography also supports the idea that there is a subducting slab near the Red River fault and an upwelling mantle plume in West Yunnan. Here our research presents seismic evidence for upwelling mantle plume, which is a main cause leading to subducting slab in West Yunnan. The analysis is based on compressional-to-shear (P-to-S) converted seismic phases, recorded on seismograph stations in the Sichuan-Yunnan seismic network, and made a study on 410-km and 660-km discontinuities, as well as on three sections of CCP stacking.  相似文献   

The Somuncura Large Igneous Province in Patagonia: Interaction of a Transient Mantle Thermal Anomaly with a Subducting Slab     

Kay  S. Mahlburg; Ardolino  A. A.; Gorring  M. L.; Ramos  V. A. 《Journal of Petrology》2007,48(1):43-77

The Oligo-Miocene Somuncura province is the largest (55 000km²) back-arc mafic volcanic field in Patagonia, and one ofEarth's largest with no clear link to a hotspot or major extension.Major and trace element and Sr–Nd–Pb isotopic datasuggest involvement of a plume-like component in the mantlemagma source mixed with hydrous, but not high field strengthelement (HFSE)-depleted components, from a disintegrating subductingplate. Magmatism is attributed to mantle upwelling related todisturbances during plate reorganization, possibly at a timewhen the South America plate was nearly stationary over theunderlying mantle. Melting was enhanced by hydration of themantle during Paleogene subduction. Crustal contamination wasminimal in a refractory crust that had been extensively meltedin the Jurassic. Eruption began with low-volume intraplate alkalinemafic flows with depleted Nd–Sr isotopic signatures. Thesewere followed by voluminous 29–25 Ma tholeiitic maficflows with flat light and steep heavy rare earth element (REE)patterns, intraplate-like La/Ta ratios, arc-like Ba/La ratiosand enriched Sr–Nd isotopic signatures. Their source canbe explained by mixing EM1–Tristan da Cunha-like and depletedmantle components with subduction-related components. Post-plateau24–17 Ma alkaline flows with steep REE patterns, highincompatible element abundances, and depleted Sr–Nd isotopicsignatures mark the ebbing of the mantle upwelling. KEY WORDS: Somuncura plateau; slab interaction; Patagonia; large igneous province (LIP); plume-like upwelling  相似文献   

Influence of seismic wave type and incident direction on the dynamic response of tall concrete-faced rockfill dams          下载免费PDF全文

Chen-guang Zhou  De-gao Zou  Xiang Yu 《地震科学（英文版）》2022,35(5):343-354

Owing to the stochastic behavior of earthquakes and complex crustal structure, wave type and incident direction are uncertain when seismic waves arrive at a structure. In addition, because of the different types of the structures and terrains, the traveling wave effects have different influences on the dynamic response of the structures. For the tall concrete-faced rockfill dam (CFRD), it is not only built in the complex terrain such as river valley, but also its height has reached 300 m level, which puts forward higher requirements for the seismic safety of the anti-seepage system mainly comprising concrete face slabs, especially the accurate location of the weak area in seism. Considering the limitations of the traditional uniform vibration analysis method, we implemented an efficient dynamic interaction analysis between a tall CFRD and its foundation using a non-uniform wave input method with a viscous-spring artificial boundary and equivalent nodal loads. This method was then applied to investigate the dynamic stress distribution on the concrete face slabs for different seismic wave types and incident directions. The results indicate that dam-foundation interactions behave differently at different wave incident angles, and that the traveling wave effect becomes more evident in valley topography. Seismic wave type and incident direction dramatically influenced stress in the face slab, and the extreme stress values and distribution law will vary under oblique wave incidence. The influence of the incident direction on slab stress was particularly apparent when SH-waves arrived from the left bank. Specifically, the extreme stress values in the face slab increased with an increasing incident angle. Interestingly, the locations of the extreme stress values changed mainly along the axis of the dam, and did not exhibit large changes in height. The seismic safety of CFRDs is therefore lower at higher incident angles from an anti-seepage perspective. Therefore, it is necessary to consider both the seismic wave type and incident direction during seismic capacity evaluations of tall CFRDs.  相似文献   

Petrogenesis and tectonic implications of early Devonian mafic dike–granite association in the northern West Junggar,NW China     

Jiyuan Yin  Wenjiao Xiao  Chao Yuan  Min Sun  Keda Cai 《International Geology Review》2018,60(1):87-100

Mafic dike–granite associations are common in extensional tectonic settings and important and pivotal in reconstructing crust–mantle geodynamic processes. We report results of zircon U–Pb and hornblende ⁴⁰Ar-³⁹Ar ages and major-element and trace-element data for mafic dike–granite association from the northern West Junggar, in order to constrain their ages, petrogenesis, and geodynamic process. The mafic dike–granite association was emplaced in the early Devonian. The Xiemisitai monzogranites have high SiO₂ contents and low MgO, Cr, and Ni concentrations, suggesting that they were mainly derived from crustal sources and were probably generated by partial melt of the juvenile mid-lower crust. The mafic dikes have low Mg^# and Cr and Ni abundances, suggesting that they have experienced significant fractional crystallization. The Xiemisitai mafic dikes contain hornblende and biotite and display negative Nb–Ta–Ti anomalies, enrichment of LREEs and LILEs, and depletion of HREEs and HFSEs, consistent with an origin from a lithospheric mantle metasomatized by subducted slab-derived fluids. In addition, the Xiemisitai mafic dikes are plotted within melting trends with little to no garnet (Cpx: Grt = 6:1) in their source. The La/Yb versus Tb/Yb plot also indicates the presence of less than 1% residual garnet in the source region for the Xiemisitai mafic dikes. Therefore, it can be inferred that the Xiemisitai mafic dikes were generated at a correspondingly shallow depth, mostly within the spinel stability field. The Xiemisitai mafic dikes were most probably generated by the partial melting of the metasomatized lithospheric mantle at relatively shallow depths (<80 km). The Xiemisitai mafic dike–granite association could have been triggered by asthenospheric upwelling as a result of the rollback of the subducted Irtysh–Zaysan oceanic lithosphere.  相似文献   

Late Cretaceous basalts and rhyolites from Shimaoshan Group in eastern Fujian Province,SE China: age,petrogenesis, and tectonic implications     

Xi-Yao Li  Yan-Hui Suo  Li-Ming Dai  Ling-Li Guo  Feng-Jian Ge 《International Geology Review》2018,60(11-14):1721-1743

ABSTRACT

Southeastern China is characterized by an extensive Late Mesozoic (Yanshanian) tectono-magmatic-metallogenic event. Although Late Cretaceous volcanism gradually weakened during the epilogue of the Yanshanian event, its petrogenesis and geodynamic processes remain unclear. In this study, we present new zircon U–Pb–Hf isotopic, whole-rock elemental, and Sr–Nd isotopic compositions data, for volcanic rocks from the Zhaixia Formation of the Shimaoshan Group in Fujian Province. The lower member of the Zhaixia Formation consists of basalts and rhyolites, and the upper member is only rhyolites. These volcanic rocks erupted in the early stage of Late Cretaceous, with basalts erupting earlier (ca. 99–98 Ma) than rhyolites (ca. 98–94 Ma). These basalts record high-K calc-alkaline to shoshonitic, light rare earth element (LREE)- and LILE-enrichment, high field strength element (HFSE)depletion with negligible Eu anomalies, and uniform whole-rock ε_Nd(t) (–3 to –6) and zircon ε_Hf(t) (–3.3 to –14.1) values. The overlying rhyolites record peraluminous and high-K calc-alkaline characteristics, LREE- and LILE-enrichment with negative Eu anomalies, and Nb–Ta depletion. The whole-rock ε_Nd(t) and zircon ε_Hf(t) values of these rhyolites both increase from the lower member (ε_Nd(t), –1.5 to –4.7; ε_Hf(t), –5.1 to –16.1) to the upper member (ε_Nd(t), –0.5 to 0.1; ε_Hf(t), –0.3 to –4.3). The features imply that these basalts were derived from the partial melting of the enriched lithospheric mantle and the overlying rhyolites from the melting of the crustal components, respectively. Data from the rhyolites in the upper member indicate that more juvenile, Nd–Hf isotopically depleted materials were injected into their source. During the Late Cretaceous, the new, fast rollback of the subducting slab triggered lithospheric extension and asthenospheric upwelling beneath the coastal regions, which induced the melting of lithospheric mantle and crustal components. As continued, the new round of basaltic underplating provided necessary heat to cause partial melting of the deep crust, including the younger, juvenile, and isotopically depleted crustal components.  相似文献   

西秦岭天水地区晚三叠世柴家庄二长花岗岩及其暗色包体地球化学——岩石成因及岩浆混合作用   总被引：1，自引：0，他引：1  

巨银娟  王邢颖  张泽中 《地质与资源》2018,27(1):43

晚三叠世花岗岩类在秦岭-大别造山带西端广泛分布,其成因机制及地球动力学背景的研究对于反演华北、扬子两大板块沿秦岭-大别造山带在三叠纪时期的拼合历史具有重要意义.本文选择西秦岭天水地区柴家庄晚三叠世二长花岗岩及其中的暗色包体进行精细的岩石学和地球化学研究.暗色包体中普遍发育针状磷灰石及斜长石捕掳晶,暗示岩浆混合作用;暗色包体具有较低的SiO₂（60.27%~60.38%）、高的Mg#（54~55）和Nb/Ta比值（14.8~16.6）,表明其来源于富集岩石圈地幔的部分熔融作用;寄主二长花岗岩表现出典型埃达克岩的地球化学特征,其富集Sr、Ba,亏损Y和HREE,岩石的Sr/Y比值介于88~98之间,Y/Yb比值介于13~15之间,暗示源区有石榴石残余.结合前人的研究结果,提出柴家庄二长花岗岩可能为增厚的造山带下地壳在碰撞后伸展环境下发生部分熔融作用的产物,可能与晚三叠世时期秦岭造山带的板片断离作用有关  相似文献