Shaking table testing of an existing masonry building: assessment and improvement of the seismic performance          下载免费PDF全文

Nuno Mendes  Paulo B. Lourenço  Alfredo Campos‐Costa 《地震工程与结构动力学》2014,43(2):247-266

This paper aims to assess and improve the seismic performance of an existing masonry building with flexible floors, representative of a Portuguese building typology—‘gaioleiro’ buildings. The study involved seismic tests and dynamic identification tests of two models (nonstrengthened and strengthened) in the shaking table. Each model was subjected to several seismic tests with increasing amplitude. Before the first test and after each seismic test, the dynamic identification of the model was carried out, aiming at obtaining their seismic vulnerability curves based on a damage indicator obtained from the decrease of the frequencies of the modes. In the strengthened model, steel elements were used to improve the connection between walls and floors, together with ties in the upper stories. The results show that adopted strengthening technique is effective for reducing the seismic vulnerability of ‘gaioleiro’ buildings, namely for improving the out‐of‐plane behavior of the facades. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Near-infrared sky background fluctuations at mid- and low latitudes     

G. Moreels  J. Clairemidi  M. Faivre  D. Pautet  F. Rubio da Costa  P. Rousselot  J.W. Meriwether  G.A. Lehmacher  E. Vidal  J.L. Chau  G. Monnet 《Experimental Astronomy》2008,22(1-2):87-107

The emission of the upper atmosphere introduces an additional variable component into observations of astronomical objects in the NIR 700–3,000 nm range. The subtraction of this component is not easy because it varies during the night by as much as 100% and it is not homogeneous over the sky. A program aimed at measuring and understanding the main characteristics of the atmospheric NIR emission was undertaken. A 512?×?512 CCD camera equipped with a RG780/2 mm filter is used to obtain images of the sky in a 36°?×?36° field of view. The intensities of a given star and of the nearby region devoid of star in a 439 arcmin² area are monitored during periods of time of several hours. The sky intensity measured in the 754–900 nm bandpass, reduced to zenith and zero airmass is comprised between mag20 and mag18.5 per arcsecond². A diminution by a factor of two during the night is frequently observed. Intensity fluctuations having an amplitude of 15% and periods of 5–40 min are present in the images with a structure of regularly spaced stripes. The fluctuations of the NIR sky background intensity are due to (1) the chemical evolution of the upper atmosphere composition during the night and (2) dynamical processes such as tides with periods of 3–6 h or gravity waves with periods of several tens of minutes. We suggest that a monitoring of the sky background intensity could be set up when quantitative observations of astronomical objects require exposure times longer than ~10 min. The publication is illustrated with several video films accessible on the web site http://www.obs-besancon.fr/nirsky/. Enter username: nirsky and password: skynir.  相似文献   

Preface     

Sebastian Wolf  Paulo J.V. Garcia   《New Astronomy Reviews》2008,52(2-5):19

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Considerations about the occurrence of pollen grains of the Valeriana eichleriana (C.A.Muller) Graebner, in sediments of the Upper Quaternary in the state of Rio Grande do Sul, Brazil     

Paulo C.P.Neves  Soraia G.Bauermann  Maria G.Rossoni  Jose R.R.Coiro  Marleni M.Toigo  Abdul R.Ashraf 《世界地质(英文版)》2004,7(1)

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Shaking table testing for masonry infill walls: unreinforced versus reinforced solutions          下载免费PDF全文

Paulo B. Lourenço  João M. Leite  Manuel F. Paulo‐Pereira  A. Campos‐Costa  P. X. Candeias  Nuno Mendes 《地震工程与结构动力学》2016,45(14):2241-2260

Several factors influence the behaviour of infilled frames, which have been a subject of research in the past with moderate success. The new generation of European design standards imposes the need to prevent brittle collapse of the infills and makes the structural engineer accountable for this requirement, yet it fails to provide sufficient information for masonry infills design. Therefore, the present work aims at understanding the seismic behaviour of masonry infill walls within reinforced concrete frames, using both unreinforced and reinforced solutions (bed joint reinforcement and reinforced plaster). For this purpose, three reinforced concrete buildings with different infill solutions were constructed at a scale of 1:1.5, all with the same geometry, and were tested on the shaking table of the National Laboratory for Civil Engineering, Portugal. All solutions performed adequately for the design earthquake, with no visible damage. Still, the experimental tests show that the double‐leaf‐unreinforced infill walls underperformed during a large earthquake, collapsing out of plane by rotating as rigid bodies with multiple configurations. Also the reinforced concrete buildings collapsed, because of the adverse interaction with the infill walls. The infill walls with bed joint reinforcement and reinforced plaster did not collapse out of plane, because of their connection to the concrete frame, which is an essential requirement. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Can a minimalist model of wind forced baroclinic Rossby waves produce reasonable results?     

Wandrey B. Watanabe  Paulo S. Polito  Ilson C. A. da Silveira 《Ocean Dynamics》2016,66(4):539-548

The linear theory predicts that Rossby waves are the large scale mechanism of adjustment to perturbations of the geophysical fluid. Satellite measurements of sea level anomaly (SLA) provided sturdy evidence of the existence of these waves. Recent studies suggest that the variability in the altimeter records is mostly due to mesoscale nonlinear eddies and challenges the original interpretation of westward propagating features as Rossby waves. The objective of this work is to test whether a classic linear dynamic model is a reasonable explanation for the observed SLA. A linear-reduced gravity non-dispersive Rossby wave model is used to estimate the SLA forced by direct and remote wind stress. Correlations between model results and observations are up to 0.88. The best agreement is in the tropical region of all ocean basins. These correlations decrease towards insignificance in mid-latitudes. The relative contributions of eastern boundary (remote) forcing and local wind forcing in the generation of Rossby waves are also estimated and suggest that the main wave forming mechanism is the remote forcing. Results suggest that linear long baroclinic Rossby wave dynamics explain a significant part of the SLA annual variability at least in the tropical oceans.  相似文献   

Geological and Isotopic Constraints on the Metallogenic Evolution of the Proterozoic Sediment-Hosted Pb-Zn (Ag) Deposits of Brazil   总被引：2，自引：0，他引：2  

Aroldo Misi  Sundaram S. Iyer  Colombo C.G. Tassinari  J. Richard Kyle  Carlos E.S. Coelho  Washington J.S. Franca-Rocha  Adriana S.R. Gomes  Ion A. Cunha  Ilson G. Carvalho 《Gondwana Research》1999,2(1):47

Integrated studies of seven Proterozoic sediment-hosted, Pb-Zn-Ag sulfide deposits of Brazil, permit the estimation of the age of the hosting sequence and the mineralization, the nature of the sulfur and metal sources, the temperature range of sulfide formation and the environment of deposition. These deposits can be classified into three groups, according to their ages. (a) Archean to Paleoproterozoic: the Boquira deposit, in Bahia state, consists of stratiform massive and disseminated sulfides hosted by parametamorphic sequences of grunnerite-cummingtonite+magnetite that represent a silicate facies of the Boquira Formation (BF). Lead isotope data of galena samples indicate a time span between 2.7 and 2.5 Ga for ore formation, in agreement with the stratigraphic position of the BF. The relatively heavy sulfur isotope compositions for the disseminated and stratiform sulfides (+8.3 to +12.8 ‰ CDT)suggest a sedimentary source for the sulfur. (b) Paleo to Mesoproterozoic: stratiform and stratabound sulfides in association with growth faults are present in the Canoas mine (Ribeira, in Paraná state) and in the Caboclo mineralization (Bahia state). They are hosted by calcsilicates and amphibolites in the Canoas deposit, whereas in the Caboclo area the mineralization is associated with hydrothermally altered dolarenites at the base of the 1.2 Ga Caboclo Formation. The interpreted Pb-Pb age of the Canoas mineralization is coeval with the 1.7 Ga host rocks. Sulfur isotopic data for Canoas sulfides (+1.2 to +16 ‰ CDT) suggest a sea water source for the sulfur. The range between −21.1 and +8.8 ‰ CDT for the Caboclo sulfides could suggest the action of bacterial reduction of seawater sulfates, but this interpretation is not conclusive. (c) Neoproterozoic: stratiform and stratabound sulfide deposits formed during the complex diagenetic history of the host carbonate rocks from the Morro Agudo (Bambui Group), Irecê and Nova Redenção (Una Group), yield heavy sulfur isotope values (+18.9 to +39.4 ‰ CDT). The uniform heavy isotope composition of the barites from these deposits (+25.1 to +40.9 ‰) reflect their origin from Neoproterozoic seawater sulfates. The late-stage, and most important, metallic concentrations represent sulfur scavenged from pre-existing sulfides or from direct reduction of evaporitic sulfate minerals. Lead isotope data from the Bambui Group suggest focused fluid circulation from diverse Proterozoic sediment sources, that probably was responsible for metal transport to the site of sulfide precipitation. (d) Late Proterozoic to Early Paleozoic: lead-zinc sulfides (+pyrite and chalcopyrite) of Santa Maria deposits, in Rio Grande do Sul, form the matrix of arkosic sandstones and conglomerates, and are closely associated with regional faults forming graben structures. Intermediate volcanic rocks are intercalated with the basal siliciclastic members. Lead isotope age of the mineralization (0.59 Ga) is coeval with the host rocks. Sulfur isotopic values between −3.6 and +4.1 are compatible with a deep source for the sulfur.Geological, petrographic and isotopic data of the deposits studied suggest that they were formed during periods of extensional tectonics. Growth faults or reactivated basement structures probably were responsible for localized circulation of metal-bearing fluids within the sedimentary sequences. Sulfides were formed by the reduction of sedimentary sulfates in most cases. Linear structures are important controls for sulfide concentration in these Proterozoic basins.  相似文献   

Dynamics of a Prorocentrum minimum bloom along the northern coast of Sinaloa,Mexico     

Aída Martínez-López  Diana Cecilia Escobedo-Urías  Ana Elsi Ulloa-Pérez  Raul Aguirre 《Continental Shelf Research》2008

To investigate the relative importance of mesoscale physical events, such as upwellings and physical and chemical variables during an algae bloom of Prorocentrum minimum, 25 sampling sites were established offshore of the Navachiste Lagoon Complex on the east side of the Gulf of California. Samples were analyzed for phytoplankton concentration, water chemistry, and temperature during November 1999, January, March, April, May, and August 2000. Satellite imagery of sea surface temperature (SST) for April 2000 was processed to obtain a synoptic view of the area during the extraordinary bloom of P. minimum in the open waters of the Gulf of California. The bloom was associated with change of oceanographic conditions from moderate winds to calm period, temperature increase and high nitrate (NO₃⁻-N) and ammonia (NH₄⁺-N) content in the offshore waters. Depletion of these nutrients during the bloom suggests that this species uses both types of nitrogen substrates. Cysts in the northernmost sampling stations in January and March indicate that upwelling water, rich in nitrates, also carried a seed stock population of P. minimum. SST patterns in the satellite imagery suggest wind-forcing as the responsible mechanisms triggering the algal bloom offshore of the Navachiste Lagoon Complex.  相似文献   

Source identification and global implications of black carbon     

Erika P.Blanco-Donado  Ismael L.Schneider  Paulo Artaxo  Jesus Lozano-Osorio  Luana Portz  Marcos L.S.Oliveira 《地学前缘(英文版)》2022,(1):404-416

Black carbon(BC)is one of the short-lived air pollutants that contributes significantly to aerosol radiative forcing and global climate change.It is emitted by the incomplete combustion of fossil fuels,biofuels,and biomass.Urban environments are quite complex and thus,the use of mobile jointly with fixed monitoring provides a better understanding of the dynamics of BC distribution in such areas.The present study addresses the measurement of BC concentration using real-time mobile and ambient monitoring in Barranquilla,an industrialized urban area of the Colombian Caribbean.A microaethalometer(MA200)and an aethalometer(AE33)were used for measuring the BC concentration.The absorption ?ngstr?m exponent(AAE)values were determined for the study area,for identifying the BC emission sources.The results of the ambient sampling show that vehicle traffic emissions prevail;however,the influence of biomass burning was also observed.The mean ambient BC concentration was found to be 1.04±1.03μg/m³ and varied between 0.5 and 4.0μg/m³.From the mobile measurements obtained in real traffic conditions on the road,a much higher average value of 16.1±16.5μg/m³ was measured.Many parts of the city showed BC concentrations higher than 20μg/m³.The spatial distribution of BC concentration shows that vehicle emissions and traffic jams,a consequence of road and transport infrastructure,are the factors that most affect the BC concentration.A comparison of results obtained from two aethalometers indicates that the concentrations measured by MA200 are 9%lower than those measured by AE33.The AAE obtained was found to vary between 1.1 and 1.6,indicating vehicular emissions as the most crucial source.In addition,it was observed that the BC concentration on working days was 2.5 times higher than on the weekends in the case of mobile monitoring and 1.5 times higher in the case of ambient monitoring.  相似文献   

Hurricane flood risk assessment for the Yucatan and Campeche State coastal area     

Rey  Wilmer  Mendoza  E. Tonatiuh  Salles  Paulo  Zhang  Keqi  Teng  Yi-Chen  Trejo-Rangel  Miguel A.  Franklin  Gemma L. 《Natural Hazards》2019,96(3):1041-1065

Natural Hazards - In this study, the first ever Sea, Lake, Overland Surges from Hurricanes (SLOSH) grid was built for the Yucatan Peninsula. The SLOSH model was used to simulate storm surges in the...  相似文献