Application of hybrid‐simulation to fragility assessment of the telescoping self‐centering energy dissipative bracing system

Substructure hybrid simulation has been the subject of numerous investigations in recent years. The simulation method allows for the assessment of the seismic performance of structures by representing critical components with physical specimens and the rest of the structure with numerical models. In this study the system level performance of a six‐storey structure with telescoping self‐centering energy dissipative (T‐SCED) braces is validated through pseudo‐dynamic (PsD) hybrid simulation. Fragility curves are derived for the T‐SCED system. This paper presents the configuration of the hybrid simulation, the newly developed control software for PsD hybrid simulation, which can integrate generic hydraulic actuators into PsD hybrid simulation, and the seismic performance of a structure equipped with T‐SCED braces. The experimental results show that the six‐storey structure with T‐SCED braces satisfies performance limits specified in ASCE 41. Copyright © 2013 John Wiley & Sons, Ltd.     

Current state and trends in Canadian Arctic marine ecosystems: I. Primary production

During the International Polar Year (IPY), large international research programs provided a unique opportunity for assessing the current state and trends in major components of arctic marine ecosystems at an exceptionally wide spatio-temporal scale: sampling covered most regions of the Canadian Arctic (IPY-Canada??s Three Oceans project), and the coastal and offshore areas of the southeastern Beaufort Sea were monitored over almost a full year (IPY-Circumpolar Flaw Lead project). The general goal of these projects was to improve our understanding of how the response of arctic marine ecosystems to climate warming will alter the productivity and structure of the food web and the ecosystem services it provides to Northerners. The present paper summarizes and discusses six key findings related to primary production (PP), which determines the amount of food available to consumers. (1) Offshore, the warming and freshening of the surface layer is leading to the displacement of large nanophytoplankton species by small picophytoplankton cells, with potentially profound bottom-up effects within the marine food web. (2) In coastal areas, PP increases as favourable winds and the deeper seaward retreat of ice promote upwelling. (3) Multiple upwelling events repeatedly provide food to herbivores throughout the growth season. (4) A substantial amount of pelagic PP occurs under thinning ice and cannot be detected by orbiting sensors. (5) Early PP in the spring does not imply a trophic mismatch with key herbivores. (6) The epipelagic ecosystem is very efficient at retaining carbon in surface waters and preventing its sedimentation to the benthos. While enhanced PP could result in increased fish and marine mammal harvests for Northerners, it will most likely be insufficient for sustainable large-scale commercial fisheries in the Canadian Arctic.     

Assessment of vulnerability for rockfalls in Cozia Gorge (Southern Carpathians,Romania)

Natural Hazards - Rockfalls represents a sudden, extremely important geomorphological hazard and may become a threat for people’s life, as well as goods and transport. The present study aims...     

Soil metal pollution from former Zn–Pb mining assessed by geochemical and magnetic investigations: case study of the Bou Caid area (Tissemsilt,Algeria)

Former zinc and lead mines that have been operating for half a century are located in the massif of Bou Caid (Tissemsilt, Algeria). Hazardous heavy metals emitted from the mines are abundant in the surrounding soil and cause strong metal pollution in the region. This paper investigates the extent of lead and zinc mine activity derived pollution by characterizing both magnetic and geochemical properties of samples collected in the vicinity of the mines. The results of the magnetic study show the coexistence of magnetic minerals such as magnetite, hematite and goethite. Analyses on surface soils and weathered rocks suggest that hematite and goethite have ore-related lithogenic origins. Magnetic susceptibility shows a positive correlation with lead content when present in low-to-medium concentrations (< ~500 mg/kg). At higher lead concentrations, there is no correlation with magnetic susceptibility. The relationship between magnetic susceptibility and zinc content is not straightforward. These observations are explained by the higher affinity of Pb to iron oxides at lower pollution levels and their preferential bonding to carbonates when Pb and Zn contents are extremely high, as demonstrated by Iavazzo et al. (J Geochem Explor 113:56–67, 2012) in a study of former Zn–Pb mine in Morocco. Based on the general features of the spatial maps of field-measured magnetic susceptibility, mass-specific magnetic susceptibility, Pb and Zn contents, it is concluded that field magnetic measurements provide a good qualitative proxy of pollution spread out of the mining galleries, while laboratory measurements afford a more detailed investigation of the links between iron oxides and the main heavy metals in the ore.     

Magnetic signature of different vegetation species in polluted environment

Detailed magnetic study on vegetation samples from several strongly polluted and clean sites in Bulgaria is carried out in order to evaluate suitability of different species as passive dust collectors in magnetometry. From each location, available species among lichens, mosses, poplar leaves, dandelion, needles have been sampled. Magnetic susceptibility calculated on mass-specific basis shows wide variability between diamagnetic signal up to 846 × 10⁻⁸ m³/kg. Lichens and mosses are found to be the species, showing magnetic signals with the strongest contrast between clean and polluted environment. The main magnetic phase is magnetite-like according to the results from thermomagnetic analysis of susceptibility on magnetic extracts. Scanning electron microscopy (SEM) microphotographs reveal the presence of abundant particulate matter on vegetation surface both with anthropogenic (spherules) and lithogenic origin. Magnetic grain size deduced by the ratio of saturation remanent magnetization (SIRM) and mass-specific magnetic susceptibility (χ) and coercivities (B_c and B_cr) suggest that different species accumulate preferentially small SD-like grains from pollution emissions. Contrasting relationship of the ratio of anhysteretic remanent magnetization (ARM) and χ for polluted vs clean sites deduced by needles and lichens may be related to transformation of the accumulated dust particles within lichens’ tissue. This finding indicates that the exact species used as biological dust collector is of importance when studying spatial grain size distribution of magnetic dust particles. Pilot study on polycyclic aromatic hydrocarbons (PAH) content and its relation to magnetic parameters shows good correspondence between high levels of PAHs and high SIRM values for locations affected by non-ferrous industrial production.     

Particulate matter geochemistry of a highly industrialized region in the Caribbean:Basis for future toxicological studies

Air pollution has become an important issue,especially in Caribbean urban areas,and,particulate matter(PM)emitted by different natural and anthropogenic sources causes environmental and health issues.In this work,we studied the concentrations of PM₁₀ and PM_2.5 sources in an industrial and port urban area in the Caribbean region of Colombia.PM samples were collected within 48-h periods between April and October 2018 by using a Partisol 2000 i-D sampler.Elemental geochemical characterization was performed by X-ray fluorescence(XRF)analysis.Further,ionic species and black carbon(BC)were quantified by ion chromatography and reflectance spectroscopy,respectively.Using the Positive Matrix Factorization(PMF)receptor model,the contributions of PM sources were quantified.The average concentration of PM₁₀ was 46.6±16.2μg/m³,with high concentrations of Cl and Ca.For PM_2.5,the average concentration was 12.0±3.2μg/m³,and the most abundant components were BC,S,and Cl.The receptor model identified five sources for PM₁₀ and PM_2.5.For both fractions,the contributions of marine sea spray,re-suspended soil,and vehicular traffic were observed.In addition,PM_2.5 included two mixed sources were found to be fuel oil combustion with fertilizer industry emissions,and secondary aerosol sources with building construction emissions.Further,PM₁₀ was found to also include building construction emissions with re-suspended soil,and metallurgical industry emissions.These obtained geochemical atmospheric results are important for the implementation of strategies for the continuous improvement of the air quality of the Caribbean region.     

Palaeoclimatic record from a loess–soil profile in northeastern Bulgaria—I. Rock magnetic properties

A detailed record of mineral magnetic properties of a loess–palaeosol profile comprising seven loess horizons, six interbedded palaeosols and recent soil at the top in NE Bulgaria is analysed. A strong contrast between the soil and loess susceptibilities as well as other concentration-dependent hysteresis parameters is present, similar to the well-documented magnetic characteristics of the Chinese loess ( Hus & Han 1992 ; Maher & Thompson 1992 ; Heller & Evans 1995 ; Hunt et al. 1995 ). The magnetic enhancement of the palaeosol units is caused by very fine-grained pedogenic magnetite with superparamagnetic behaviour. Thermomagnetic analyses on bulk material suggest magnetite and maghemite as the main ferrimagnetic carriers in both soil and loess horizons. Their relative proportions are shown to reflect different palaeoclimatic conditions. Chernozem soils, which include recent soil S₀ and first and second palaeosols S₁ and S₂ developed under steppe vegetation, show a high degree of low-temperature oxidation of the pedogenic magnetite to maghemite. This material is characterized by coercive force H _c showing even higher values than those of the parent loess material. The older palaeosols (S₄ to S₆ ) were formed during more humid climatic conditions and therefore probably developed as forest types. Rock magnetic data suggest the existence here of only partly oxidized magnetite grains. The behaviour of the thermomagnetic curves, characterized by a kink at 200 °C, may be due to either a release of internal stress (built up as a result of partial low-temperature oxidation) or interactions between two phases.     

Archaeomagnetic investigation of two mediaeval brick constructions in north Belgium and the magnetic anisotropy of bricks

Archaeomagnetic dates derived from geomagnetic field direction records in baked materials are proposed for a mediaeval brick kiln (from inclination I and declination D) and for bricks from a brick wall (from I only) in northern Belgium. They are used to verify whether a brick chronology based on the format of bricks is feasible in Flanders. The brick kiln yielded a highly reliable average magnetization direction corresponding to an archaeomagnetic date around A.D. 1650, using the British and French geomagnetic field secular variation curves as a reference, at least half a century younger than expected from historical data. The fidelity of the geomagnetic records was controlled by measuring the magnetic anisotropy of the bricks. Anisotropy of magnetic susceptibility (AMS) measurements demonstrate that the bricks have a shape related magnetic fabric, which is induced during the molding process. A test to control whether AMS can substitute for the anisotropy of thermo‐remanent magnetization (ATRM) failed because of induced changes during laboratory heating. © 2003 Wiley Periodicals, Inc.     

The impact of inhomogenous background errors on a global wave data assimilation system

One of the main limitations in current wave data assimilation systems is the lack of an accurate representation of the structure of the background errors. In this work, models for the observational error variance, background error variance and background error correlations are developed based on the results of previous studies. These are tested in a global wave data assimilation system and the resulting wave forecasts are verified against independent observations from buoys. Forecasts of significant wave height show substantial improvement over the Australian Bureau of Meteorology's current operational wave forecasting system. However, forecasts of peak period are not similarly improved. The regional impacts of the new assimilation scheme are found to vary on a seasonal basis. Overall, it is shown that the inclusion of a latitudinally dependent background error, and improved specification of the background and observational error variances can reduce the root-mean-square error of 24-hour forecast Significant Wave Height by almost 10%.     

Weathering of sandstone lotus petals at the Angkor site: a 1,000-year stone durability trial

This article is based on field investigations carried out at Ta Keo and Banteay Srei temples (Angkor, Cambodia), which have similar environmental histories and display the same recurrent decorative pattern (lotus petal) in three different sandstone lithotypes. Based on two original scales of mechanical and chemical weathering, the degree of deterioration of c.2000 sandstone petals was visually assessed, resulting in the proposal of a durability scale. An explanatory scheme was provided, based on laboratory analyses of stone materials (ICP-AES, XRD, SEM-EDS, polarizing microscopy and mercury injection). The key drivers of sandstone durability are both mineralogical and petrophysical. The remarkable preservation of the pink sandstone is due to the quartzose nature of its clasts, the non-swelling clay content of its abundant matrix (kaolinite) and its porosity structure (large connected pores and probable non-connected porosity). The overall good preservation of the green sandstone is due to its extremely low porosity and specific surface area, associated with its strong cementation. The severe deterioration of the grey sandstone is due to its laminated structure (oriented biotites), the susceptibility to hygric swelling and solution of its binding agents (chlorite/smectite and calcite) and its porosity structure, which evolves during a two-stage weathering sequence. The first stage is characterized by a bimodal porosity due to the partial clogging of macropores by swelling clays, and the second stage by a substantial increase in porosity and the penetration of salts (barite and anhydrite). Conversely, oxidation phenomena associated with weathering can lead to a drastic reduction of porosity.