Influence of frequency‐dependent soil–structure interaction on the fragility of R/C bridges          下载免费PDF全文

Nikolaos Lesgidis  Anastasios Sextos  Oh‐Sung Kwon 《地震工程与结构动力学》2017,46(1):139-158

Bridge performance under earthquake loading can be significantly influenced by the interaction between the structure and the supporting soil. Even though the frequency dependence of the interaction mentioned in this study has long been documented, the simplifying assumption that the dynamic stiffness is dominated by the mean or predominant excitation frequency is still commonly made, primarily as a result of the associated numerical difficulties when the analysis has to be performed in the time domain. This study makes use of the advanced lumped parameter models recently developed 1 in order to quantify the impact of the assumption on the predicted fragility of bridges mentioned in this study. This is achieved by comparing the predicted vulnerability for the case of a reference, well studied, actual bridge using both conventional, frequency‐independent, Kelvin–Voigt models and the aforementioned lumped parameter formulation. Analysis results demonstrate that the more refined consideration of frequency dependence of soil–structure interaction at the piers and the abutments of a bridge not only leads to different probabilities of failure for given intensity measures but also leads to different hierarchy and distribution of damage within the structure for the same set of earthquake ground motions even if the overall probability of exceeding a given damage state is the same. The paper concludes with the comparative assessment of the effect for different soil conditions, foundation configurations, and ground motion characteristics mentioned in this study along with the relevant analysis and design recommendations. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Ca(OH)2 Pre‐Treated Bentonite for Phosphorus Removal and Recovery From Synthetic and Real Wastewater          下载免费PDF全文

Giorgos Markou  Dimitris Mitrogiannis  Vassilis Inglezakis  Koenraad Muylaert  Nikolaos Koukouzas  Nikolaos Tsoukalas  Efstratios Kamitsos  Dimitrios Palles  Ioannis Baziotis 《洁净——土壤、空气、水》2018,46(2)

  相似文献   

Synergies of THESEUS with the large facilities of the 2030s and guest observer opportunities     

Rosati  P.  Basa  S.  Blain  A. W.  Bozzo  E.  Branchesi  M.  Christensen  L.  Ferrara  A.  Gomboc  A.  O’Brien  P. T.  Osborne  J. P.  Rossi  A.  Schüssler  F.  Spurio  M.  Stergioulas  N.  Stratta  G.  Amati  L.  Casewell  S.  Ciolfi  R.  Ghirlanda  G.  Grimm  S.  Guetta  D.  Harms  J.  Le Floc’h  E.  Longo  F.  Maggiore  M.  Mereghetti  S.  Oganesyan  G.  Salvaterra  R.  Tanvir  N. R.  Turriziani  S.  Vergani  S. D.  Balman  S.  Caruana  J.  Erkut  M. H.  Guidorzi  G.  Frontera  F.  Martin-Carrillo  A.  Paltani  S.  Porquet  D.  Sergijenko  O. 《Experimental Astronomy》2021,52(3):407-437

Experimental Astronomy - The proposed THESEUS mission will vastly expand the capabilities to monitor the high-energy sky. It will specifically exploit large samples of gamma-ray bursts to probe the...  相似文献   

Assessing water stress in Mediterranean lotic systems: insights from an artificially intermittent river in Greece     

Nikolaos Th. Skoulikidis  Leonidas Vardakas  Ioannis Karaouzas  Alcibiades N. Economou  Elias Dimitriou  Stamatis Zogaris 《Aquatic Sciences - Research Across Boundaries》2011,73(4):581-597

Water stress in Mediterranean countries is the result of both variable and changing climatic conditions and widespread anthropogenic pressures. Evrotas, an intermittent river located in Southern Greece, was used as a case study to assess the impacts of water stress on Mediterranean lotic ecosystems. Based on hydrological analyses, it was revealed that during prolonged drought years, such as the summers of 2007 and 2008, the vast majority of the Evrotas riverbed was completely desiccated, primarily as a result of substantial water abstraction for irrigation. The effects of desiccation on the riverine ecosystem were evaluated using fish and macroinvertebrate assemblages according to the demands of the Water Framework Directive 2000/60/EC (WFD). Faunal responses to water stress were assessed through comparisons of assemblages attributes in perennial and intermittent reaches and pre-drought versus post-drought communities. Effects of hydrological disturbance on fish species richness, density, percentage composition and size structure were more pronounced in intermittent than in perennial sites. The most obvious and immediate impact was the elimination of populations in the intermittent reaches. However, upon flow resumption, the recolonisation from upstream perennial reaches began, thereby permitting partial re-establishment of the depleted fish communities. Nevertheless, the structural integrity of fish communities remained severely impacted and recovery was markedly slow. On the contrary, post-drought macroinvertebrate assemblages were not affected by summer droughts, and the recruitment processes were rapid after flow resumption. Our findings point to the necessity of establishing a distinction between naturally and artificially driven intermittent rivers. We, therefore, propose the introduction of an “artificially intermittent Mediterranean river” condition within the context of the WFD assessment applications.  相似文献   

Statistical tools for earthquake and mining seismology     

George M. Tsaklidis  Eleftheria E. Papadimitriou  Nikolaos Limnios 《Acta Geophysica》2011,59(4):657-658

  相似文献   

Identification of hydrologic and geochemical pathways using high frequency sampling,REE aqueous sampling and soil characterization at Koiliaris Critical Zone Observatory,Crete     

Daniel Moraetis  Fotini Stamati  Manolis Kotronakis  Tasoula Fragia  Nikolaos Paranychnianakis  Nikolaos P. Nikolaidis 《Applied Geochemistry》2011

Koiliaris River watershed is a Critical Zone Observatory that represents severely degraded soils due to intensive agricultural activities and biophysical factors. It has typical Mediterranean soils under the imminent threat of desertification which is expected to intensify due to projected climate change. High frequency hydro-chemical monitoring with targeted sampling for Rare Earth Elements (REE) analysis of different water bodies and geochemical characterization of soils were used for the identification of hydrologic and geochemical pathways. The high frequency monitoring of water chemical data highlighted the chemical alterations of water in Koiliaris River during flash flood events. Soil physical and chemical characterization surveys were used to identify erodibility patterns within the watershed and the influence of soils on surface and ground water chemistry. The methodology presented can be used to identify the impacts of degraded soils to surface and ground water quality as well as in the design of methods to minimize the impacts of land use practices.  相似文献   

Approximate matching of analytic and numerical solutions for rapidly rotating neutron stars     

Emanuele Berti †  Nikolaos Stergioulas 《Monthly notices of the Royal Astronomical Society》2004,350(4):1416-1430

  相似文献   

The habitation Model Trend Calculation (MTC): A new effective tool for predictive modeling in archaeology     

George Malaperdas  Nikolaos Zacharias 《地球空间信息科学学报》2013,16(4):314-331

ABSTRACT

The aim of this paper is to create and present a new archaeological predictive model via GIS, incorporating what archaeologists consider the most important criterion absent of similar past models, that of critical thinking. The new model suggested in this paper is named habitation Model Trend Calculation (MTC) and is not only integrates the archaeological questions with a critical view, but it can be easily adjusted, according to the conditions or the questions concerning the archaeological community. Furthermore, it uses new topographical and geomorphological indexes such as Topographical Index (TPI), Hillslope and Landform Classification that give a new sense of the topographical and geomorphological characteristics of the examined area; therefore this model is a more powerful tool compared to older models that did not use new topographical and geomorphological indexes. The success of the created model is checked as a case study in the region of Messenia, Greece during the Mycenaean era. The region of Messenia is considered as one of the most important Mycenaean regions of Greece due to the great number and the importance of Mycenaean sites identified. For the present paper, 140 habitation sites were divided into four hierarchical categories (centers, large villages, villages, and farms) based on the extent and the plurality of the tholos tombs that exist in the broader region and according to the hierarchical categorization used by the archaeologists who have studied the area. The new predictive model presented in this work can assist in solving a series of criticisms that have been expressed in the previous studies regarding such models. Additionally, in the case of Mycenaean Messenia, the model shows excellent results in relation to the habitats of the time.  相似文献   

Non-linear axisymmetric pulsations of rotating relativistic stars in the conformal flatness approximation     

Harald Dimmelmeier  Nikolaos Stergioulas  José A. Font 《Monthly notices of the Royal Astronomical Society》2006,368(4):1609-1630

  相似文献   

Trends of urban surface temperature and heat island characteristics in the Mediterranean     

Nikolaos?Benas  Nektarios?ChrysoulakisEmail author  Constantinos?Cartalis 《Theoretical and Applied Climatology》2017,130(3-4):807-816

Urban air temperature studies usually focus on the urban canopy heat island phenomenon, whereby the city center experiences higher near surface air temperatures compared to its surrounding non-urban areas. The Land Surface Temperature (LST) is used instead of urban air temperature to identify the Surface Urban Heat Island (SUHI). In this study, the nighttime LST and SUHI characteristics and trends in the seventeen largest Mediterranean cities were investigated, by analyzing satellite observations for the period 2001–2012. SUHI averages and trends were based on an innovative approach of comparing urban pixels to randomly selected non-urban pixels, which carries the potential to better standardize satellite-derived SUHI estimations. A positive trend for both LST and SUHI for the majority of the examined cities was documented. Furthermore, a 0.1 °C decade^?1 increase in urban LST corresponded to an increase in SUHI by about 0.04 °C decade^?1. A longitudinal differentiation was found in the urban LST trends, with higher positive values appearing in the eastern Mediterranean. Examination of urban infrastructure and development factors during the same period revealed correlations with SUHI trends, which can be used to explain differences among cities. However, the majority of the cities examined show considerably increased trends in terms of the enhancement of SUHI. These findings are considered important so as to promote sustainable urbanization, as well as to support the development of heat island adaptation and mitigation plans in the Mediterranean.  相似文献