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During strong ground motion it is expected that extended structures (such as bridges) are subjected to excitation that varies along their longitudinal axis in terms of arrival time, amplitude and frequency content, a fact primarily attributed to the wave passage effect, the loss of coherency and the role of local site conditions. Furthermore, the foundation interacts with the soil and the superstructure, thus significantly affecting the dynamic response of the bridge. A general methodology is therefore set up and implemented into a computer code for deriving sets of appropriately modified time histories and spring–dashpot coefficients at each support of a bridge with account for spatial variability, local site conditions and soil–foundation–superstructure interaction, for the purposes of inelastic dynamic analysis of RC bridges. In order to validate the methodology and code developed, each stage of the proposed procedure is verified using recorded data, finite‐element analyses, alternative computer programs, previous research studies, and closed‐form solutions wherever available. The results establish an adequate degree of confidence in the use of the proposed methodology and code in further parametric analyses and seismic design. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
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Jean-Pierre Berger Bettina Reichenbacher Damien Becker Matthias Grimm Kirsten Grimm Laurent Picot Andrea Storni Claudius Pirkenseer Andreas Schaefer 《International Journal of Earth Sciences》2005,94(4):711-731
We present a general stratigraphic synthesis for the Upper Rhine Graben (URG) and the Swiss Molasse Basin (SMB) from Eocene to Pliocene times. The stratigraphic data were compiled both from literature and from research carried out by the authors during the past 6 years ; an index of the stratigraphically most important localitites is provided. We distinguish 14 geographical areas from the Helvetic domain in the South to the Hanau Basin in the North. For each geographical area, we give a synthesis of the biostratigraphy, lithofacies, and chronostratigraphic ranges. The relationships between this stratigraphic record and the global sea-level changes are generally disturbed by the geodynamic (e.g., subsidence) evolution of the basins. However, global sea-level changes probably affected the dynamic of transgression–regression in the URG (e.g., Middle Pechelbronn Beds and Serie Grise corresponding with sea-level rise between Ru1/Ru2 and Ru2/Ru3 sequences, respectively) as well as in the Molasse basin (regression of the UMM corresponding with the sea-level drop at the Ch1 sequence). The URGENT-project (Upper Rhine Graben evolution and neotectonics) provided an unique opportunity to carry out and present this synthesis. Discussions with scientists addressing sedimentology, tectonics, geophysics and geochemistry permitted the comparison of the sedimentary history and stratigraphy of the basin with processes controlling its geodynamic evolution. Data presented here back up the palaeogeographic reconstructions presented in a companion paper by the same authors (see Berger et al. in Int J Earth Sci 2005). 相似文献
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Iron-poor and refractory lithophile element (RLE) rich forsterite grains occur in all major types of unequilibrated chondrites. In our laser ablation inductively coupled mass spectrometry (LA-ICPMS) minor and trace element study we show that refractory forsterites (RF) from carbonaceous (CC), unequilibrated ordinary (UOC) and a Rumuruti chondrite (RC) have similar chemical compositions with high RLE concentrations and low concentrations of Mn, Fe, Co and Ni. Fractionation of RLEs and rare earth elements (REEs) is in agreement with formation by crystallization from a RLE rich silicate melt. Low concentrations and the fractionation of moderately siderophile elements (Fe, Co, Ni) in RFs suggests formation at low oxygen fugacity, possibly in equilibrium with primitive Fe,Ni metal condensates in a gas of solar composition. Anomalously high Ti in the parental melt can be explained by Ti3+/Ti4+ ∼1.5, supporting formation of RF in highly reducing conditions. Low Mn concentrations indicate formation at high temperatures (>∼1160 K). The model of formation of RFs and the accompanying physico-chemical conditions during their formation as well as their relation to non refractory olivine are discussed. 相似文献
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Climatology of Ozone, PAN, CO, and NMHC in the Free Troposphere Over the Southern North Atlantic 总被引:1,自引:0,他引:1
Free tropospheric measurements of ozone, peroxyacetylnitrate andprecursors (CO, NMHC) that were made within the framework of the EUROTRACsub-project TOR (Tropospheric Ozone Research) between 1990 and 1995 at theGAW station Izana, Tenerife (28°18N, 16°30W) arediscussed. The average annual cycles reveal the importance of transport fromnorthern mid-latitudes and the role of photo-chemistry. According toair-mass trajectories, which were supplied to us from AEROCE(Atmosphere/Ocean Chemistry Experiment), transport from northernmid-latitudes is associated with high precursor concentrations in winter,whereas ozone concentrations in winter are not much influenced by transportpatterns, suggesting a rather uniform distribution over the northern part ofthe Northern Hemisphere around mean value of 43 ± 5 ppb. In summer,high ozone concentrations of up to 90 ppb are often encountered duringtransport from north, while the levels of precursors are much lower than inwinter, because of photochemical destruction. Trajectories from southerlylatitudes and the Sahara usually have the lowest ozone concentrationsassociated with them. 相似文献
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Mountainous regions cover about 27 per cent of the world’s land surface and are home to some 22 per cent of the global population (UNEP 2002). A much greater number of people depend on mountain environments for a wide range of services, including clean water, energy, timber, biodiversity, recreation, and protection from environmental hazards, such as landslides and floods. At the same time, mountain areas are extremely vulnerable ecosystems and under continuous threat of environmental degrad… 相似文献
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Hasanuddin Z. Abidin I. Gumilar H. Andreas D. Murdohardono Y. Fukuda 《Environmental Earth Sciences》2013,68(6):1545-1553
The Bandung Basin is a large intra-montane basin surrounded by volcanic highlands, in western Java, Indonesia, inhabited by more than seven million people. The basin, an area of about 2,300 km2, is a highland plateau at approximately 650–700 m above sea level and is surrounded by up to 2,400 m high Late Tertiary and Quaternary volcanic terrain. Based on the results of nine GPS surveys conducted since 2000 up to 2011, it was shown that several locations in the Bandung Basin have experienced land subsidence, with an average rate of about ?8 cm/year and can go up to about ?23 cm/year in certain locations. A hypothesis has been proposed by several studies that land subsidence observed in several locations in the Bandung Basin has been caused mainly by excessive groundwater extraction. It is found that there is a strong correlation between the rates of groundwater level lowering with the GPS-derived rates of land subsidence in several locations in Bandung Basin. The GPS results in this study detected significant subsidence in the textile industry area, where very large volumes of groundwater are usually extracted. The impact of land subsidence in Bandung can be seen in several forms, mainly in the cracking and damage of houses, buildings and infrastructure. Land subsidence also aggravates the flooding in Bandung Basin, which has brought huge economic losses and deteriorated the quality of life and environment in the affected areas. 相似文献
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Andreas Burkert 《Astrophysics and Space Science》2003,284(2):697-700
The puzzling correlation between the spin parameter λ of galactic disks and the disk-to-halo mass fraction f
disk is investigated. It is shown that such a correlation arises naturally from large uncertainties in determining the virial
masses of dark matter halos. This result indicates that halo properties derived from fits to observed rotation curves are
still very uncertain. An analysis of λ versus f
disk as function of the adopted halo virial mass shows that for reasonable halo concentrations f
disk ≈ 0.01 - 0.07 which is significantly smaller than the universal baryon fraction. Most of the available gas either never settled
into the galactic disks or was ejected subsequently.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献