Structural and nonstructural performance of a seismically isolated building using stable unbonded fiber‐reinforced elastomeric isolators          下载免费PDF全文

Niel C. Van Engelen  Dimitrios Konstantinidis  Michael J. Tait 《地震工程与结构动力学》2016,45(3):421-439

Stable unbonded fiber‐reinforced elastomeric isolators (SU‐FREIs) exhibit a characteristic horizontal softening and stiffening response, similar to other adaptive devices such as the triple friction pendulum and sliding systems with variable curvature. The transition between the softening and stiffening occurs at a displacement corresponding to a unique deformation known as full rollover. In this paper, the full rollover displacement of SU‐FREIs is altered by using modified support geometry (MSG), a geometric modification of the upper and lower supports applied to tailor the hysteresis loops of the isolator. Experimental results are used to calibrate a numerical model of a base‐isolated structure. The model demonstrates that the stiffening regime provides minimal restraint against displacements during events that meet or exceed the maximum considered earthquake. A parametric study revealed that the level of stiffening required to restrain displacements during large events is significant. This increase in stiffness is reflected in an increase in the response of the structure and light nonstructural components. Full rollover and MSG is considered advantageous to maintain horizontal stability and provide control over the stiffening of SU‐FREIs. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Science and User Needs for Observing Global Mass Transport to Understand Global Change and to Benefit Society     

Roland Pail  Rory Bingham  Carla Braitenberg  Henryk Dobslaw  Annette Eicker  Andreas Güntner  Martin Horwath  Eric Ivins  Laurent Longuevergne  Isabelle Panet  Bert Wouters  IUGG Expert Panel 《Surveys in Geophysics》2015,36(6):743-772

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A multi-model comparison of Atlantic multidecadal variability     

Jin Ba  Noel S. Keenlyside  Mojib Latif  Wonsun Park  Hui Ding  Katja Lohmann  Juliette Mignot  Matthew Menary  Odd Helge Otterå  Bert Wouters  David Salas y Melia  Akira Oka  Alessio Bellucci  Evgeny Volodin 《Climate Dynamics》2014,43(9-10):2333-2348

A multi-model analysis of Atlantic multidecadal variability is performed with the following aims: to investigate the similarities to observations; to assess the strength and relative importance of the different elements of the mechanism proposed by Delworth et al. (J Clim 6:1993–2011, 1993) (hereafter D93) among coupled general circulation models (CGCMs); and to relate model differences to mean systematic error. The analysis is performed with long control simulations from ten CGCMs, with lengths ranging between 500 and 3600 years. In most models the variations of sea surface temperature (SST) averaged over North Atlantic show considerable power on multidecadal time scales, but with different periodicity. The SST variations are largest in the mid-latitude region, consistent with the short instrumental record. Despite large differences in model configurations, we find quite some consistency among the models in terms of processes. In eight of the ten models the mid-latitude SST variations are significantly correlated with fluctuations in the Atlantic meridional overturning circulation (AMOC), suggesting a link to northward heat transport changes. Consistent with this link, the three models with the weakest AMOC have the largest cold SST bias in the North Atlantic. There is no linear relationship on decadal timescales between AMOC and North Atlantic Oscillation in the models. Analysis of the key elements of the D93 mechanisms revealed the following: Most models present strong evidence that high-latitude winter mixing precede AMOC changes. However, the regions of wintertime convection differ among models. In most models salinity-induced density anomalies in the convective region tend to lead AMOC, while temperature-induced density anomalies lead AMOC only in one model. However, analysis shows that salinity may play an overly important role in most models, because of cold temperature biases in their relevant convective regions. In most models subpolar gyre variations tend to lead AMOC changes, and this relation is strong in more than half of the models.  相似文献   

The introduction of Sargassum muticum modifies epifaunal patterns in a Moroccan seagrass meadow          下载免费PDF全文

Zahira Belattmania  Abdellatif Chaouti  Abdeltif Reani  Aschwin H. Engelen  Margarida Machado  Ester A. Serrão  Brahim Sabour 《Marine Ecology》2018,39(3)

Marine macrophytes sustain valuable epiphytic biodiversity. Nonindigenous macroalgae may induce changes in composition and structure of epifaunal assemblages and therefore support different assemblages from those associated with native species. In this study, differences in faunal community structure between the introduced fucoid Sargassum muticum and the native seagrass Cymodocea nodosa were tested over a year on an intertidal shallow sandy bottom at the southern introduction front, the El Jadida coastline (NW Morocco). Epifaunal community structure consistently differed between macrophytes through seasons, with more species‐rich assemblages associated with S. muticum than C. nodosa despite comparable abundances. The significantly greater epifauna diversity on S. muticum may be related to its structural complexity. However, the species contributing most to differences in assemblages between both macrophytes, such as Steromphala umbilicalis and S. pennanti, were found on both habitats with temporally varying abundances. Some species‐specific affinities were detected (Stenosoma cf. acuminatum, Elasmopus vachoni, Chauvetia brunnea). Nitrogen, dissolved oxygen, suspended matter and temperature were identified as the best explanatory variables contributing to the observed macroepifaunal patterns. This study provides evidence that S. muticum acts as a favourable and additional habitat for epifaunal species and supports a more diverse epifaunal assemblage in this Moroccan seagrass meadow.  相似文献   

Interdecadal North-Atlantic meridional overturning circulation variability in EC-EARTH   总被引：2，自引：2，他引：0  

Bert Wouters  Sybren Drijfhout  Wilco Hazeleger 《Climate Dynamics》2012,39(11):2695-2712

The Atlantic meridional overturning circulation (AMOC) in a 600?years pre-industrial run of the newly developed EC-EARTH model features marked interdecadal variability with a dominant time-scale of 50–60?years. An oscillation of approximately 2 Sverdrup (1?Sv?=?10⁶?m³?s^?1) is identified, which manifests itself as a monopole causing the overturning to simultaneously strengthen (/weaken) and deepen (/shallow) as a whole. Eight years before the AMOC peaks, density in the Labrador-Irminger Sea region reaches a maximum, triggering deep water formation. This density change is caused by a counterclockwise advection of temperature and salinity anomalies at lower latitudes, which we relate to the north-south excursions of the subpolar-subtropical gyre boundary and variations in strength and position of the subpolar gyre and the North Atlantic Current. The AMOC fluctuations are not directly forced by the atmosphere, but occur in a delayed response of the ocean to forcing by the North Atlantic Oscillation, which initiates “intergyre”-gyre fluctuations. Associated with the AMOC is a 60-year sea surface temperature variability in the Atlantic, with a pattern and timescale showing similarities with the real-world Atlantic Multidecadal Variability. This good agreement with observations lends a certain degree of credibility that the mechanism that is described in this article could be seen as representative of the real climate system.  相似文献   

Circulation dynamics and its influence on European and Mediterranean January–April climate over the past half millennium: results and insights from instrumental data, documentary evidence and coupled climate models     

J. Luterbacher  S. J. Koenig  J. Franke  G. van der Schrier  E. Zorita  A. Moberg  J. Jacobeit  P. M. Della-Marta  M. Küttel  E. Xoplaki  D. Wheeler  T. Rutishauser  M. Stössel  H. Wanner  R. Brázdil  P. Dobrovolný  D. Camuffo  C. Bertolin  A. van Engelen  F. J. Gonzalez-Rouco  R. Wilson  C. Pfister  D. Limanówka  Ø. Nordli  L. Leijonhufvud  J. Söderberg  R. Allan  M. Barriendos  Rüdiger Glaser  D. Riemann  Z. Hao  C. S. Zerefos 《Climatic change》2010,101(1-2):201-234

We use long instrumental temperature series together with available field reconstructions of sea-level pressure (SLP) and three-dimensional climate model simulations to analyze relations between temperature anomalies and atmospheric circulation patterns over much of Europe and the Mediterranean for the late winter/early spring (January–April, JFMA) season. A Canonical Correlation Analysis (CCA) investigates interannual to interdecadal covariability between a new gridded SLP field reconstruction and seven long instrumental temperature series covering the past 250 years. We then present and discuss prominent atmospheric circulation patterns related to anomalous warm and cold JFMA conditions within different European areas spanning the period 1760–2007. Next, using a data assimilation technique, we link gridded SLP data with a climate model (EC-Bilt-Clio) for a better dynamical understanding of the relationship between large scale circulation and European climate. We thus present an alternative approach to reconstruct climate for the pre-instrumental period based on the assimilated model simulations. Furthermore, we present an independent method to extend the dynamic circulation analysis for anomalously cold European JFMA conditions back to the sixteenth century. To this end, we use documentary records that are spatially representative for the long instrumental records and derive, through modern analogs, large-scale SLP, surface temperature and precipitation fields. The skill of the analog method is tested in the virtual world of two three-dimensional climate simulations (ECHO-G and HadCM3). This endeavor offers new possibilities to both constrain climate model into a reconstruction mode (through the assimilation approach) and to better asses documentary data in a quantitative way.  相似文献   

Monthly, seasonal and annual temperature reconstructions for Central Europe derived from documentary evidence and instrumental records since AD 1500   总被引：2，自引：0，他引：2  

Petr Dobrovolný  Anders Moberg  Rudolf Brázdil  Christian Pfister  Rüdiger Glaser  Rob Wilson  Aryan van Engelen  Danuta Limanówka  Andrea Kiss  Monika Halíčková  Jarmila Macková  Dirk Riemann  Jürg Luterbacher  Reinhard Böhm 《Climatic change》2010,101(1-2):69-107

Monthly temperature series for Central Europe back to AD 1500 are developed from documentary index series from Germany, Switzerland and the Czech Republic (1500–1854) and 11 instrumental temperature records (1760–2007). Documentary evidence from the Low Countries, the Carpathian Basin and Poland are used for cross-checking for earlier centuries. The instrumental station records are corrected for inhomogeneities, including insufficient radiation protection of early thermometers and the urban heat island effect. For overlapping period (1760–1854), the documentary data series correlate with instrumental temperatures, most strongly in winter (86% explained variance in January) and least in autumn (56% in September). For annual average temperatures, 81% of the variance is explained. Verification statistics indicate high reconstruction skill for most months and seasons. The last 20 years (since 1988) stand out as very likely the warmest 20-year period, accounting for the calibration uncertainty and decreases in proxy data quality before the calibration period. The new reconstruction displays a previously unobserved long-term decrease in DJF, MAM and JJA temperature variability over last five centuries. Compiled monthly, seasonal and annual series can be used to improve the robustness of gridded large-scale European temperature reconstructions and possible impact studies. Further improvement of the reconstruction would be achieved if documentary data from other European countries are further developed.  相似文献   

Modelling environmentally friendly fairways using Lagrangian trajectories: a case study for the Gulf of Finland,the Baltic Sea     

Tarmo Soomere  Mihhail Berezovski  Ewald Quak  Bert Viikmäe 《Ocean Dynamics》2011,61(10):1669-1680

We address possibilities of minimising environmental risks using statistical features of current-driven propagation of adverse impacts to the coast. The recently introduced method for finding the optimum locations of potentially dangerous activities (Soomere et al. in Proc Estonian Acad Sci 59:156–165, 2010) is expanded towards accounting for the spatial distributions of probabilities and times for reaching the coast for passively advecting particles released in different sea areas. These distributions are calculated using large sets of Lagrangian trajectories found from Eulerian velocity fields provided by the Rossby Centre Ocean Model with a horizontal resolution of 2 nautical miles for 1987–1991. The test area is the Gulf of Finland in the northeastern Baltic Sea. The potential gain using the optimum fairways from the Baltic Proper to the eastern part of the gulf is an up to 44% decrease in the probability of coastal pollution and a similar increase in the average time for reaching the coast. The optimum fairways are mostly located to the north of the gulf axis (by 2–8 km on average) and meander substantially in some sections. The robustness of this approach is quantified as the typical root mean square deviation (6–16 km) between the optimum fairways specified from different criteria. Drastic variations in the width of the ‘corridors’ for almost optimal fairways (2–30 km for the average width of 15 km) signifies that the sensitivity of the results with respect to small changes in the environmental criteria largely varies in different parts of the gulf.  相似文献   

Unforeseen importance of historical collections as baselines to determine biotic change of coral reefs: the Saba Bank case     

Bert W. Hoeksema  Jacob van der Land  Sancia E. T. van der Meij  Leendert P. van Ofwegen  Bastian T. Reijnen  Rob W. M. van Soest  Nicole J. de Voogd 《Marine Ecology》2011,32(2):135-141

Botanical and zoological collections may serve as archives for historical ecological research on the effects of global change and human impact on coral reef biota. Museum collections may harbour old specimens of reef‐dwelling species that have become locally extinct. Such collections also help to determine whether early records of invasive species can be obtained from times when they were not yet recognized as such. A case study (2006) involving Saba Bank, Caribbean Netherlands (former Netherlands Antilles), suggests that the coral reef fauna here may have become impoverished when compared with data obtained during an earlier expedition in 1972. However, the 1972 sampling may have been incomplete, as it was performed by professional divers who were not trained taxonomists, whereas the collecting in 2006 was done by experienced marine biologists who knew the taxa they were sampling. As Saba Bank has been under stress due to the anchoring of large vessels, and invasive species have been a potential threat as well, future studies are needed to obtain more insights into the changing reef biota of Saba Bank. Using this Saba Bank example, we want to address the importance of natural history collections as reservoirs of valuable data relevant to coral reef biodiversity studies in a time of global change. As such, these collections are still underexplored and underexploited.  相似文献   

Challenges From Solid Earth Dynamics for Satellite Gravity Field Missions in the Post-Goce Era     

Bert L. A. Vermeersen 《Earth, Moon, and Planets》2004,94(1-2):31-40

Examples from four main categories of solid-earth deformation processes are discussed for which the GOCE and GRACE satellite gravity missions will not provide a high enough spatial or temporal resolution or a sufficient accuracy. Quasi-static and episodic solid-earth deformation would benefit from a new satellite gravity mission that would provide a higher combined spatial and temporal resolution. Seismic and core periodic motions would benefit from a new satellite mission that would be able to detect gravity variations with a higher temporal resolution combined with very high accuracies.  相似文献