Structures in locations susceptible to severe seismic disturbances should be designed properly in order to resist lateral forces induced by earthquake motions. Steel offshore platforms are some of those structures which are built to withstand environmental and accidental loads during oil exploitation operation. Particular attention is being paid to earthquake loads in seismic active areas because it directly influences the capacity of the offshore installations.
In this paper, a small-scaled planar platform has been modelled analytically using nonlinear finite element program, based on an experimental test, conducted simultaneously in order to assess the local and global behavior of pile–leg interaction in Jacket Type Offshore Platforms (JTOPs). A combination of nonlinear beam column elements and fatigue affected elements are used to capture the inelastic cyclic behavior of planar frame as accurately as possible. Results of analytical tests are to be compared with experiments and it is concluded that an analytical approach can be best used for modelling JTOPs with reasonable accuracy regardless of the type and scale of the structure. Moreover, a special study on joints has been carried out and the best model has been selected to simulate brittle behavior of joints resulting from heat affected zone. 相似文献
The first discovery of dinosaur footprints on the Dalmatian part of the Adriatic-Dinaric carbonate platform (ADCP) is reported. They constitute the geologically youngest record of footprints on the ADCP. The trackbearing layer was formed in the intertidal environment and represents the final stage of a shallowing-upward cycle. Just below it, a heavy dinoturbated limestone layer can be observed. Microfacies analysis, incorporating evidence from benthic foraminifera and algae, indicates a Late Turonian–Early Coniacian age. The overall morphology and size of the footprints points to sauropod dinosaurs; they represent the largest forms recorded so far on the ADCP. This hints at a prolonged sauropod presence on the platform and to its Late Cretaceous connection to the continent rather than isolation. 相似文献
Geochemistry of chlorine and fluorine in apatites, micas, and amphiboles in rocks from eight intrusive complexes of the Siberian Platform has been first studied on the basis of new factual and analytical data (more than 1000 analyses). The main attention is focused on minerals from layered intrusions. Most apatites show F > Cl; the maximum contents of halogens are specific to chlorapatite (6.97 wt.% Cl) and fluorapatite (6.04 wt.% F). The total f value (f = Fe/(Fe + Mg), at.%) of femic minerals varies from 2 to 98 at.% in micas and from 22 to 95 at.% in amphiboles. The Cl-f and F-f trends show an increase in the Cl content and a decrease in the F content in the minerals with increasing f. Chlorine clearly exhibits ferrophilic properties, and fluorine has magnesiophilic properties. The halogen-richest minerals are fluorophlogopite (F = 7.06 wt.%, f = 7 at.%), chlorannite (Cl = 6.30 wt.%, f = 89 at.%), and chloroferrihastingsite (Cl = 5.22 wt.%, f = 90 at.%). Coexisting micas and amphiboles in the rocks are close in f value, but the micas are richer in Cl than the amphiboles. We assume that the halogen-containing minerals crystallized at the high pressure of halogen-hydrocarbon fluids at the levels of the MW, IW, and QIF buffers. The reducing conditions of the magmatism process are also evidenced by the presence of graphite and native metals in the rocks. The similarity of the Cl-f and F-f trends of micas and amphiboles from different intrusive complexes indicates the same mechanisms of the melt differentiation and mineral crystallization. 相似文献