Real-time hybrid simulation of structures equipped with viscoelastic-plastic dampers using a user-programmable computational platform     

Jack Wen Wei Guo  Ali Ashasi-Sorkhabi  Oya Mercan  Constantin Christopoulos 《地震工程与工程振动(英文版)》2017,16(4):693-711

A user-programmable computational/control platform was developed at the University of Toronto that offers real-time hybrid simulation (RTHS) capabilities. The platform was verified previously using several linear physical substructures. The study presented in this paper is focused on further validating the RTHS platform using a nonlinear viscoelastic-plastic damper that has displacement, frequency and temperature-dependent properties. The validation study includes damper component characterization tests, as well as RTHS of a series of single-degree-of-freedom (SDOF) systems equipped with viscoelastic-plastic dampers that represent different structural designs. From the component characterization tests, it was found that for a wide range of excitation frequencies and friction slip loads, the tracking errors are comparable to the errors in RTHS of linear spring systems. The hybrid SDOF results are compared to an independently validated thermalmechanical viscoelastic model to further validate the ability for the platform to test nonlinear systems. After the validation, as an application study, nonlinear SDOF hybrid tests were used to develop performance spectra to predict the response of structures equipped with damping systems that are more challenging to model analytically. The use of the experimental performance spectra is illustrated by comparing the predicted response to the hybrid test response of 2DOF systems equipped with viscoelastic-plastic dampers.  相似文献   

Avalonian and Cadomian terranes in North Dobrogea,Romania     

Ion Balintoni  Constantin Balica  Antoneta Seghedi  Mihai N. Ducea 《Precambrian Research》2010

The North Dobrogea orogen is a collage of dismembered terrane fragments between the Moesian platform and East European craton (Baltica). It records Alpine and Variscan deformation, magmatism and metamorphism. Its basement comprises three metamorphic complexes (Boclugea, Megina and Orliga) that are separated by tectonic boundaries. Detrital zircon U/Pb ages suggest the Boclugea and Orliga complexes represent two peri-Gondwanan terranes of Avalonian and Cadomian affinities, respectively. The new data clarify the original relationships between the North Dobrogea terranes, and Baltica and Moesia platform.  相似文献   

The solar service of the National Observatory of Athens     

Constantin J. Macris 《Solar physics》1967,2(1):125-128

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Towards a dedicated impact portal to bridge the gap between the impact and climate communities : Lessons from use cases     

Céline Déandreis  Christian Pagé  Pascale Braconnot  Lars Bärring  Edoardo Bucchignani  Wim Som de Cerff  Ronald Hutjes  Sylvie Joussaume  Constantin Mares  Serge Planton  Maarten Plieger 《Climatic change》2014,125(3-4):333-347

Future climate evolution is of primary importance for the societal, economical, political orientations and decision-making. It explains the increasing use of climate projections as input for quantitative impact studies, assessing vulnerability and defining adaptation strategies in different sectors. Here we analyse 17 national and representative use cases so as to identify the diversity of the demand for climate information depending on user profiles as well as the best practices, methods and tools that are needed to answer the different requests. A particular emphasis is put on the workflow that allows to translate climate data into suitable impact data, the way to deal with the different sources of uncertainty and to provide a suited product to users. We identified three complementary tools to close the gap between climate scientists and user needs: an efficient interface between users and providers; an optimized methodology to handle user requests and a portal to facilitate access to data and elaborated products. We detail in the paper how these three tools can limit the intervention of experts, educate users, and lead to the production of useful information. This work provides the basis on which the ENES (European Network for Earth System Modelling) Portal Interface for the Climate Impact Communities is built.  相似文献   

A procedure for generating performance spectra for structures equipped with passive supplemental dampers     

Jack Wen Wei Guo  Constantin Christopoulos 《地震工程与结构动力学》2013,42(9):1321-1338

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Viscoelastic coupling dampers (VCDs) for enhanced wind and seismic performance of high‐rise buildings     

Constantin Christopoulos  Michael Montgomery 《地震工程与结构动力学》2013,42(15):2217-2233

As high‐rise buildings are built taller and more slender, their dynamic behavior becomes an increasingly critical design consideration. Wind‐induced vibrations cause an increase in the lateral wind design loads, but more importantly, they can be perceived by building occupants, creating levels of discomfort ranging from minor annoyance to severe motion sickness. The current techniques to address wind vibration perception include stiffening the lateral load‐resisting system, adding mass to the building, reducing the number of stories, or incorporating a vibration absorber at the top of the building; each solution has significant economic consequences for builders. Significant distributed damage is also expected in tall buildings under severe seismic loading, as a result of the ductile seismic design philosophy that is widely used for such structures. In this paper, the viscoelastic coupling damper (VCD) that was developed at the University of Toronto to increase the level of inherent damping of tall coupled shear wall buildings to control wind‐induced and earthquake‐induced dynamic vibrations is introduced. Damping is provided by incorporating VCDs in lieu of coupling beams in common structural configurations and therefore does not occupy any valuable architectural space, while mitigating building tenant vibration perception problems and reducing both the wind and earthquake responses of the structure. This paper provides an overview of this newly proposed system, its development, and its performance benefits as well as the overall seismic and wind design philosophy that it encompasses. Two tall building case studies incorporating VCDs are presented to demonstrate how the system results in more efficient designs. In the examples that are presented, the focus is on the wind and moderate earthquake responses that often govern the design of such tall slender structures while reference is made to other studies where the response of the system under severe seismic loading conditions is examined in more detail and where results from tests conducted on the viscoelastic material and the VCDs in full‐scale are presented. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Radon and remediation measures near Băiţa-Ştei old uranium mine (Romania)     

Constantin Cosma  Alexandra Cucoş  Botond Papp  Robert Begy  Tiberiu Dicu  Mircea Moldovan  Lucia Adina Truţă  Dan Constantin Niţă  Bety-Denissa Burghele  Liviu Suciu  Carlos Sainz 《Acta Geophysica》2013,61(4):859-875

B?i?a-?tei mine is an open pit mine in NW Romania (West Carpathian Mountains). It was the largest surface uranium deposit in the world. Two means of uranium transport and dissemination were used over time. The first was the natural way, represented by transportation of geological sediments by Cri?ul-B?i?a River that crosses the B?i?a surface deposit. These sediments were used as building materials (stone, gravel, sand). The second way was related to the people living in this valley, who used also the uranium waste as building material. The preliminary indoor radon concentrations measured in the buildings ranged from 40 to 4000 Bq m^?3 with a mean value of 241 Bq m^?3. A focused radon survey facilitated the selection of 20 houses with the highest indoor radon that were therefore proposed for remediation. To find the radon sources of these houses, systematic investigations on radon were performed. The remedial measures for these 20 houses were tested on a chosen pilot house.  相似文献   

Sliding response of gravity dams including vertical seismic accelerations     

Constantin?ChristopoulosEmail author  Pierre?Léger  André?Filiatrault 《地震工程与工程振动(英文版)》2003,2(2):189-200

Seismic safety assessment of gravity dams has become a major concern in many regions of the world while the effects of vertical seismic accelerations on the response of structures remain poorly understood. This paper first investigates the effect of including vertical accelerations in the sliding response analysis of gravity dams subjected to a range of historical ground motion records separated in two groups according to their source-to-site distance. Analyses showed that the incidence of vertical accelerations on the sliding response of gravity dams is significantly higher for near-source records than for farsource records. The pseudo-static 30% load combination rule, commonly used in practice to account for the non-simultaneous occurrence of the peak horizontal and vertical accelerations, yielded good approximations of the minimum safety factors against sliding computed from time-history analyses. A method for empirically estimating the vertical response spectra based on horizontal spectra, accounting for the difference in frequency content and amplitudes between the two components is investigated. Results from analyses using spectrum compatible horizontal and vertical synthetic records also approximated well the sliding response of a gravity dam subjected to series of simultaneous horizontal and vertical historical earthquake records.  相似文献   

Le développement du potentiel dans le cas d'une densité lisse     

Constantin Kholchevnikov 《Celestial Mechanics and Dynamical Astronomy》1972,6(2):214-220

The potential of a body of revolution is expanded in a series of spherical functions. It is proved that for a body of smooth structure the coefficients of expansion decrease in a power law.

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The mm wave outbursts of November 1 and 2, 1968     

Michael Anastassiades  Constantin Macris 《Solar physics》1969,10(1):188-195

On November 1 and 2, 1968 two flares of importance 2b associated with the active region = S15°, L = 173° presented particular activity in the mm band. The outburst of November 1 in the mm wavelength band was of the gradual rise and fall type, while 24 hours later, the outburst of November 2 was of the sudden increase type with flux increase of the order of 4000 units. In the cm band the flare of November 1 produced a flux increase greater than in the mm band, while on November 2 the flare produced a series of outbursts with gradually increasing maxima, but much lower than the mm flux increase. It is reported that generally the peak flux decreases with increasing wavelength. The outburst of November 2 follows this rule but it is exactly the opposite for the sudden increase outburst produced by the November 1 flare. As to whether an increased brightness produces a higher mm or cm flux increase, available observations are not sufficient to make a firm statement.  相似文献