Force reduction factors for steel buildings with welded and post-tensioned connections     

Alfredo Reyes-Salazar  Mario D. Llanes-Tizoc  Juan Bojorquez  Edén Bojórquez  Arturo López-Barraza  Achintya Haldar 《Bulletin of Earthquake Engineering》2016,14(10):2827-2858

The seismic responses of steel buildings with perimeter moment resisting frames (MRF) with welded connections (WC) are estimated and compared to those of similar buildings with semi-rigid post-tensioned connections (PC). The responses are estimated in terms of ductility reduction factors (R _µ,), ductility demands (µ _G ) and force reduction factors (R). Two steel model buildings, which were modeled as complex-3D-MDOF systems, were used in the study. Results indicate that the reduction magnitude of global response parameters is larger than that of local response parameters, contradicting the same reduction implicitly assumed in the static equivalent lateral force procedure, implying that non-conservative design may result. The value of 8 for R, suggested in many codes for ductile steel MRF, and the value of 1 suggested in the well known Newmark and Hall procedure for the ratio of R to µ _G , cannot be justified. The reason for this is that SDOF systems were used to model actual structures, where higher mode effects, energy dissipation and structural overstrength weren’t explicitly considered. The codes should be more transparent regarding the magnitude and the components involved in the force reduction factors. The seismic performance of steel buildings with PC may be superior to that of the buildings with WC, since their force reduction factors are larger and their ductility demands smaller, implying that PC buildings could be designed for smaller lateral seismic forces. The conclusions of this paper are for the particular structural systems and models considered. Much more research is needed to reach more general conclusions.  相似文献   

Faulräume und Möglichkeiten der Schlammtrocknung und Eindickung     

Ed. Holinger Dipl.-Ing. 《Aquatic Sciences - Research Across Boundaries》1957,19(1):457-480

Ohne Zusammenfassung  相似文献   

Book review     

Martin A. Buzas  Michael Ed. Hohn  John H. Schuenemeyer 《Mathematical Geology》1986,18(2):257-262

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Variability of the Atlantic thermohaline circulation described by three-dimensional empirical orthogonal functions     

Ed Hawkins  Rowan Sutton 《Climate Dynamics》2007,29(7-8):745-762

We describe the use of bivariate three-dimensional empirical orthogonal functions (EOFs) in characterising low frequency variability of the Atlantic thermohaline circulation (THC) in the Hadley Centre global climate model, HadCM3. We find that the leading two modes are well correlated with an index of the meridional overturning circulation (MOC) on decadal timescales, with the leading mode alone accounting for 54% of the decadal variance. Episodes of coherent oscillations in the sub-space of the leading EOFs are identified; these episodes are of great interest for the predictability of the THC, and could indicate the existence of different regimes of natural variability. The mechanism identified for the multi-decadal variability is an internal ocean mode, dominated by changes in convection in the Nordic Seas, which lead the changes in the MOC by a few years. Variations in salinity transports from the Arctic and from the North Atlantic are the main feedbacks which control the oscillation. This mode has a weak feedback onto the atmosphere and hence a surface climatic influence. Interestingly, some of these climate impacts lead the changes in the overturning. There are also similarities to observed multi-decadal climate variability.  相似文献   

Die Windverhältnisse am Bodensee     

Ed. Huss  D. Stranz 《Pure and Applied Geophysics》1970,81(1):323-356

Summary Within the programme sponsored by the Deutsche Forschungsgemeinschaft (Bad Godesberg) in which different branches of scientific disciplines cooperated in order to investigate Lake Constance in Southern Germany, meteorology was mainly dealing with the wind situation round the Lake.Investigations by the Aerological Observatory of Friedrichshafen which was destroyed during the last war, yielded fundamental contributions to the problem of air currents on the Lake and in the outer regions of the Alps in its vicinity. With regard to the various problems in the common achievements of the Lake Constance Project of the Deutsche Forschungsgemeinschaft it proved necessary to extend the investigations across the whole region of the Lake in order to elaborate the synoptic situations of the daily and annual periodical wind systems.The vertical structure of the air currents could not be inferred but by an indirect manner, whilst its confirmation by direct aerological means is going to be studied in an additional research programme. The results of the comprehensive observational material of several years will be published in a final report by the Deutsche Forschungsgemeinschaft.Here some special results of the wind observations are presented.  相似文献   

Les végétaux (Macrofossiles) du crétacé moyen de l'Europe occidentale et du Sahara. Végétations et paléoclimats     

C. Alvarez-Ramis  Ed. Biondi  D. Desplats  N. F. Hughes  J. C. Koeniguer  D. Pons  M. Rioult 《Cretaceous Research》1981,2(3-4)

Cette note expose un ensemble de synthèses régionales sur les thèmes suivants: les macrofossiles de l'Angleterre; les bois de l'Albien du Boulonnais; les végétaux de Normandie du Crétacé moyen; les milieux forestiers littoraux du Cénomanien inférieur de l'Anjou et des Charentes; les macroflores du Crétacé moyen continental de l'Espagne; les gisements de l'Italie et du Sahara.L'esquisse d'une évolution possible de quelques végétations de ces contrées est proposée, ainsi que les arguments paléoclimatiques que l'on peut en déduire.This paper presents a regional synthesis concerning mid-Cretaceous plant megafossils from England, Normandy, Northern and Western France, Spain, Italy, and the Sahara. A possible evolution pattern is offered for these floras during mid-Cretaceous time; some climatic arguments are presented.  相似文献   

Objective comparison of mass fragmentograms by principal components analysis: method and results     

Michael Ed. Hohn  N.W. Jones  R. Patience 《Geochimica et cosmochimica acta》1981,45(7):1131-1140

The multivariate statistical method of Principal Components Analysis is used to classify gas chromatographic-mass spectrometric data. The specific examples comprise sterane and triterpane regions of GC-MS analyses of branched/cyclic fractions. The statistical model provides an objective analogue to visual comparison and classification of mass fragmentograms. Sources of experimental error influencing the statistical results include insufficient sample size, short integration times, and peak skewing. The method successfully groups samples of oils, oil sand, and polluted beach sand according to geographic origin: beach sand groups with type of crude spilled; laboratory biodegraded and untreated Nigerian crudes group together. Applications of three-mode Principal Components Analysis can range from study of geologic processes acting on organic compounds to classification of unknown pollutants.  相似文献