Centrifuge modelling-based verification of response spectra design methods for some vulnerable structures     

S. P. G. Madabhushi  C. H. Lawson 《Geotechnical and Geological Engineering》2006,24(4):793-808

Residential RC framed structures suffered heavily during the 2001 Bhuj earthquake in Gujarat, India. These types of structures also saw severe damage in other earthquakes such as the 1999 Kocaeli earthquake in Turkey and 921 Ji-Ji earthquake in Taiwan. In this paper the seismic response of residential structures was investigated using physical modelling. Idealised soft storey and top heavy, two degrees of freedom (2DOF) portal frame structures were developed and tested on saturated and dry sand models at 25 g using the Schofield Centre 10-m Beam Centrifuge. It was possible to recreate observed field behaviour using these models. As observed in many of the recent earthquakes, soft storey structures were found to be particularly vulnerable to seismic loads. Elastic response spectra methods are often used in the design of simple portal frame structures. The seismic risk of these structures can be significantly increased due to modifications such as removal of a column or addition of heavy water tanks on the roof. The experimental data from the dynamic centrifuge tests on such soft storey or top-heavy models was used to evaluate the predictions obtained from the response spectra. Response spectra were able to predict seismic response during small to moderate intensity earthquakes, but became inaccurate during strong earthquakes and when soil structure interaction effects became important. Re-evaluation of seismic risk of such modified structures is required and time domain analyses suggested by building codes such as IBC, UBC or NEHRP may be more appropriate.  相似文献   

Gzhelian fusulinids first discovered in central Iran     

E. Ya. Leven  M. H. Gorgij 《Stratigraphy and Geological Correlation》2006,14(1):19-29

Gzhelian deposits established in Iran for the first time are described. They rest with a considerable hiatus on the Moscovian deposits constituting, along with Asselian strata, an integral carbonate succession of the Zaladu Formation in eastern Iran. The Zaladu Formation is correlative with the Vazhnan Formation of the Abadeh region (central Iran) and the Dorud Formation of the Elburz (Alborz) Mountains. An assemblage of Gzhelian fusulinids from the studied section is well comparable with the assemblage of the Ultradaixina bosbytauensis Zone distinguished in the uppermost Gzhelian of the Darvaz, Fergana, the Southern Urals, Donetsk Basin, and Carnic Alps. Two new species of the genus Schellwienia (Sch. anarakensis and Sch. stocklini) are described. Gzhelian and Asselian fusulinids found in the section are figured in two paleontological plates.  相似文献   

Seismic Hazards Assessment for Radioactive Waste Disposal Sites in Regions of Low Seismic Activity   总被引：4，自引：0，他引：4  

Clark H. Fenton  John Adams  Stephen Halchuk 《Geotechnical and Geological Engineering》2006,24(3):579-592

A comparative tectonic quiescence and lack of earthquakes make the stable centres of continents attractive for siting long-term radioactive waste storage facilities. The low rates of deformation in such regions, however, make it difficult to characterize their long-term seismotectonic behaviour, leading to uncertain estimates for the very low probability hazard estimates required by society. In an attempt to overcome the deficiency of both contemporary seismicity and paleoseismic data in central Canada, we have used earthquake histories from regions with similar seismotectonic characteristics from around the world. Substituting space for time, we estimate a long-term rate per 10⁶ km² of 0.004 magnitude ≥6 earthquakes per annum, of which 33–100% might rupture to the surface.  相似文献   

Interpreting tracer breakthrough tailing in a conduit-dominated karstic aquifer   总被引：1，自引：2，他引：1  

N. Massei  H. Q. Wang  M. S. Field  J. P. Dupont  J. Rodet 《Hydrogeology Journal》2006,14(6):849-858

Breakthrough tailing has been observed during dye-tracing recovery tests in the Norville aquifer system (chalk), France. Karst-conduit flow and transport parameters were assessed using two different interpretative methods: the linear graphical method and the Chatwin method (implemented in the Qtracer2 program). The linear graphical method was used to model the observed tailing effects, which was explained by a second smaller delayed breakthrough curve. By comparing the results of tracer-test interpretation for the two methods, it was possible to relate the area of this second curve to the importance of turbulent flow in spring discharge. The more turbulent the flow, the less important the contribution of the second breakthrough curve and the tailing effect. The observed tailing could possibly be controlled by hydrodynamics to a greater extent than usually expected, the tailing effects being mostly attributed to diffusion phenomena. Tailing effects were expected to increase with discharge and the piezometric level, which would have resulted in overpressure in conduits, fissure flooding, etc. Instead, breakthrough tailing tended to disappear with increasing aquifer discharge, which would support the hypothesis of there being mostly hydrodynamic-controlled tailing effects instead of matrix- or fissure-diffusion.An erratum to this article can be found at  相似文献   

Dissolved Trace Metal–Organic Complexes in the Lot–Garonne River System Determined Using the C18 Sep-Pak System     

E. Lemaire  G. Blanc  J. Schäfer  A. Coynel  H. Etcheber 《Aquatic Geochemistry》2006,12(1):21-38

An 11-month observation of dissolved and particulate organic matter, chlorophyll a(Chl a), C18 Sep-Pak extractable hydrophobic dissolved organic matter (hDOM) fraction and associated dissolved trace metals (Cd, Cu, V, Co, Ni, Mo, U) was performed in the Lot–Garonne River system. This system includes the Riou Mort, the Lot River and the downstream reaches of the Garonne River and represents the fluvial transport path of trace metals between the major point source of polymetallic pollution, located in the Riou Mort watershed and the Gironde estuary. Spatial and temporal variations of dissolved and particulate organic carbon and Chl areflect the presence of different types of organic matter and their relation with the hDOM fraction. Maximum Chl a/POC ratios (up to 0.03), indicate intense phytoplankton production from March to May. In the Lot River (Temple), DOC and POC concentrations were clearly higher and mean Chl a concentration (2.8 mg g⁻¹) was about three times higher than those of the other sites. High Chl a/POC ratios suggest high phytoplankton activity with maxima in spring and late summer. In the Riou Mort River, very high POC concentrations of up to 40 (mean: 20) occurred, whereas Chl a concentrations were relatively low indicating low phytoplankton activity. High, strongly variable DOC and POC concentrations suggest important natural (Carboniferous soils, forests) or anthropogenic (e.g., former coal mines, waste areas, agriculture, sewage) carbon sources within the small Riou Mort watershed. Despite high DOC concentrations in the Riou Mort River, hDOM metal fractions were generally lower than those at the other sites. The general order of decreasing binding strength between metals and the organic hydrophobic phase (Cu, U > Co, Ni > V, Mo > Cd) at all four sites was in good agreement with the Irving–William series of transition element affinity towards organic ligands. Accordingly, the role of the hydrophobic phase in dissolved Cd transport appeared to be negligible, whereas the hDOM–Cu fraction strongly contributed to dissolved Cu transport.  相似文献   

Editorial     

G. Barla  H. Einstein  K. Kovari 《Rock Mechanics and Rock Engineering》2006,39(2):87-87

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Avalanche Risk During Backcountry Skiing – An Analysis of Risk Factors     

Harpa Grímsdóttir  David Mcclung 《Natural Hazards》2006,39(1):127-153

Skier-triggered avalanches are the main cause of avalanche accidents in backcountry skiing. The risk of accidents during backcountry skiing was analysed statistically and related to factors such as elevation level, aspect, stability rating and the time of the year. The analysis is based on a database about terrain usage and avalanche accidents from a large heli-skiing operator in Canada, which makes it possible to study the conditional probability of accidents given the recorded pattern of terrain usage. This study shows that the historical risk of accidentally triggering an avalanche greater than size 1 depends highly on the stability rating, with the highest risk occurring during “poor” stability. The risk is greater at high elevations, and it is lower during the late season than earlier on. Skier risk does not depend as much on aspect as may be indicated from avalanche data alone. However, it is relatively high in the N–NE–E sector. These factors are not independent of each other and therefore analyses of combined factors were also performed. Questionnaires and interviews were used to gain knowledge about the terrain selection of professional mountain guides. These results indicate that when selecting terrain, guides first look at the overall shape and size of the terrain, but avalanche history of terrain and inclination are also important factors. Finally, remarks in avalanche reports were analysed, and common human factors identified.  相似文献   

Mercury speciation and mobilization in contaminated soils of the Valle del Azogue Hg mine (SE,Spain)   总被引：1，自引：0，他引：1  

A. Navarro  H. Biester  J. L. Mendoza  E. Cardellach 《Environmental Geology》2006,49(8):1089-1101

Hg mobilization from contaminated soils and mine wastes was the source of environmental contamination in the Valle del Azogue mining area. We researched solid-phase speciation and aqueous mobility of Hg through Scanning electron microscopy-energy dispersive X-ray spectroscopy and electron probe microanalysis analysis, solid-phase-Hg-thermo-desorption (SPTD) and laboratory column experiments. We found that in contaminated soils and mine wastes, the predominant Hg species was cinnabar (HgS), mainly formed from the weathering of Hg-rich pyrite, and metallic Hg (0) in the matrix, whereas in calcines and tailings the dominant species was metallic Hg (0). The mobilization of Hg in the aqueous phase seems to have originated from the dissolution of elemental Hg (0) present in soils and wastes, reaching concentrations of up to 67 μg l⁻¹, and showing a higher long-term environmental potential risk, in addition to atmospheric emissions.  相似文献   

环境样品中痕量元素的化学形态分析Ⅱ．砷汞镉锡铅硒铬的形态分析   总被引：2，自引：6，他引：2  

何红蓼  倪哲明李冰 杨红霞 《岩矿测试》2005,24(2):118-128

环境中元素的生物有效性和毒性依赖于其存在的化学形态。文章依据文献的有关报道介绍砷、汞、镉、锡、铅、硒和铬在环境中的分布、毒性及它们在环境样品如水、土壤、沉积物和生物体中的形态分析方法,包括分析物的保存、提取、分离和检测。引用文献120篇。  相似文献   

Multicollinearity and correlation among local regression coefficients in geographically weighted regression   总被引：5，自引：3，他引：5  

David Wheeler  Michael Tiefelsdorf 《Journal of Geographical Systems》2005,7(2):161-187

Present methodological research on geographically weighted regression (GWR) focuses primarily on extensions of the basic GWR model, while ignoring well-established diagnostics tests commonly used in standard global regression analysis. This paper investigates multicollinearity issues surrounding the local GWR coefficients at a single location and the overall correlation between GWR coefficients associated with two different exogenous variables. Results indicate that the local regression coefficients are potentially collinear even if the underlying exogenous variables in the data generating process are uncorrelated. Based on these findings, applied GWR research should practice caution in substantively interpreting the spatial patterns of local GWR coefficients. An empirical disease-mapping example is used to motivate the GWR multicollinearity problem. Controlled experiments are performed to systematically explore coefficient dependency issues in GWR. These experiments specify global models that use eigenvectors from a spatial link matrix as exogenous variables.This study was supported by grant number 1 R1 CA95982-01, Geographic-Based Research in Cancer Control and Epidermiology, from the National Cancer Institute. The author thank the anonymous reviewers and the editor for their helpful comments.  相似文献