Assessment of seismic damage of thin and lightly reinforced concrete walls using fractal dimension of cracking          下载免费PDF全文

Julian Carrillo  William Avila 《地震工程与结构动力学》2017,46(4):661-675

Length, maximum width, and residual width of cracks are key indicators of structural damage. However, pattern and propagation of cracks on the affected structural component should be also considered. In addition, damage evaluation based on visual inspection is a subjective and capricious procedure because the damage assessment relies on the expertise and judgment of the inspector engineer. In order to assess a rapid and reliable evaluation approach of seismic damage, pattern and propagation of cracks observed in thin and lightly reinforced concrete walls for low‐rise housing subjected to seismic demands are evaluated in this study by means of fractal dimension of cracking pattern. The proposed parameters are based on the results of an experimental program that comprised 39 low‐rise RC wall specimens having typical variables of this type of housing, such as low compressive strengths of concrete, thin walls, low axial loads, low reinforcement ratios, and web shear reinforcement made of deformed bars and welded‐wire meshes. A statistical analysis is carried out for computing values of fractal dimension associated to cracking patterns at key damage conditions. Recommendations of this study can help the inspector in estimating the current limit state or performance level of the wall and the story‐drift ratio experienced by the wall during shaking. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Soil-zone microfabrics in calcrete and in desiccation cracks from the upper Jurassic purbeck formation of dorset     

Julian E. Andrews 《Geological Journal》1988,23(3):261-270

Soil-zone microfabrics, alveolar-septal structure, needle-fibre calcite, and calcans are described from horizontal calcrete layers, stringers, and infillings in vertical desiccation cracks from an Upper Jurassic limestone in the Lower Purbeck Formation of Dorset. These calcrete palaeosols occur in an oolitic limestone (the Hard Cap) which represents former evaporitic lagoonal to carbonate mudflat environments. The calcretes occur 6-10 cm below the Great Dirt Bed, a former rendzina soil with rooted tree remains. Desiccation cracks and vugs formed in the oolitic sediment before Great Dirt Bed times. After formation of the Great Dirt Bed, soil-water rich in dissolved CaCO₃ preferentially flowed through natural conduits in the underlying sediment, namely the desiccation cracks and vugs. Calcrete precipitated in these cracks and vugs around decaying plant roots, and probably, during more arid (evaporative) climatic periods. These palaeosol microfabrics are among the first to be described from the British Jurassic and were probably preserved due to the semiarid Lower Purbeck climate where rapid oxidation of organic matter limited the amount and strength of carbonic acid generation, thereby limiting extensive dissolution of early formed soil-zone carbonate. Early diagenetic cementation of the sediment also aided microfabric preservation by sealing off soil-zone structures from subsequent diagenetic fluids.  相似文献   

Midwater fishes in the eastern North Atlantic—I. Vertical distribution and associated biology in 30°N, 23°W,with developmental notes on certain myctophids     

Julian Badcock  N.R. Merrett 《Progress in Oceanography》1976,7(1):3-58

This paper is the first of a series describing the vertical distribution of midwater fishes in the eastern North Atlantic in areas approximately 10° of latitude apart near the 20° meridian. As such, it is concerned solely with collections made in 30°N, 23°W. The results are based primarily upon RMT 8 net samples collected using an opening-closing RMT 1+8 combination net. In all, 17,443 specimens were caught by RMT 8, divisible into 37 families, 66 genera with 98 species identified. Numerically the most abundant groups recognized were the Gonostomatidae (60% total catch), Macrorhamphosidae (23%) and Myctophidae (7%). Some definition of vertical limits is provided for the majority of species represented, but only 31 are considered in detail. Where possible, observed biological phenomena (e.g. development, sexual maturity, sexual dimorphism, etc.) and distribution limits have been correlated. In general, the characteristics of species' distributions, and the observed relations of distribution and migratory behaviour were as one would anticipate from past work. Among many species, a size-depth stratification was observed, and with migrants, migratory behaviour appeared dependent upon developmental state. The mode of species development, however, had no bearing upon ultimate migratory behaviour. Certain non-migratory elements of the population of an habitually migrant species, e.g. Chauliodus danae, could not be satisfactorily interpreted upon the basis of biological factors examines. Migrant species principally occupied 400–900 m depth by day, and 25–300 m by night, although they occurred at greater depths. Reverse migrations were only observed in Macrorhamphosus. The overall catches were dominated by non-migrants, and at depths greater that 200 m these comprised the most abundant species per depth at all times. Cyclothone constituted the most abundant genus sampled and provided greatest insight into distributional and biological detail. C. braueri, the most numerous species, is probably a single spawner, and the results demonstrate a size-depth stratification that may be correlated with sexual maturity stages. The olfactory structure in males is more complicated than previously described. The larger males develop a snout prolongation which would improve water flow through the nasal rosette and hence olfaction. Unlike C. microdon, C. braueri probably does not undergo sex-reversal. Developmental notes are included for the myctophid species Notoscopelus resplendens, Benthosema suborbitale, and Hygophum hygomi in the Appendix.  相似文献   

Tropical drought patterns and their linkages to large-scale climate variability over Peninsular Malaysia     

Qing He  Kwok Pan Chun  Mou Leong Tan  Bastien Dieppois  Liew Juneng  Julian Klaus  Matthieu Fournier  Nicolas Massei  Omer Yetemen 《水文研究》2021,35(9):e14356

Ocean–atmosphere modes of climate variability in the Pacific and Indian oceans, as well as monsoons, regulate the regional wet and dry episodes in tropical regions. However, how those modes of climate variability, and their interactions, lead to spatial differences in drought patterns over tropical Asia at seasonal to interannual time scales remains unclear. This study aims to analyse the hydroclimate processes for both short- and long-term spatial drought patterns (3-, 6, 12- and 24-months) over Peninsular Malaysia using the Standardized Precipitation Index, Standardized Precipitation Evapotranspiration Index, and Palmer Drought Severity Index. Besides that, a generalized least squares regression is used to explore underlying circulation mechanisms of these spatio-temporal drought patterns. The tested drought indices indicate a tendency towards wetter conditions over Peninsular Malaysia. Based on principal component analysis, distinct spatio-temporal drought patterns are revealed, suggesting North–South and East–West gradients in drought distribution. The Pacific El Nino Southern Oscillation (ENSO), the South Western Indian Ocean (SWIO) variability, and the quasi-biennial oscillation (QBO) are significant contributors to the observed spatio-temporal variability in drought. Both the ENSO and the SWIO modulate the North–South gradient in drought conditions over Peninsular Malaysia, while the QBO contributes more to the East–West gradient. Through modulating regional moisture fluxes, the warm phases of the ENSO and the SWIO, and the western phases of the QBO weaken the southwest and northeast monsoon, leading to precipitation deficits and droughts over Peninsular Malaysia. The East–West or North–South gradients in droughts are related to the middle mountains blocking southwest and northeast moisture fluxes towards Peninsular Malaysia. In addition, the ENSO and QBO variations are significantly leading to short-term droughts (less than a year), while the SWIO is significantly associated with longer-duration droughts (2 years or more). Overall, this work demonstrates how spatio-temporal drought patterns in tropical regions are related to monsoons and moisture transports affected by the oscillations over the Pacific and Indian oceans, which is important for national water risk management.  相似文献   

Moving beyond run‐off calibration—Multivariable optimization of a surface–subsurface–atmosphere model          下载免费PDF全文

Simon Stisen  Julian Koch  Torben O. Sonnenborg  Jens Christian Refsgaard  Simone Bircher  Rasmus Ringgaard  Karsten H. Jensen 《水文研究》2018,32(17):2654-2668

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Hydrogen isotope fractionation in freshwater and marine algae: II. Temperature and nitrogen limited growth rate effects     

Zhaohui Zhang  Julian P. Sachs  Adrian Marchetti 《Organic Geochemistry》2009,40(3):428-439

Zhang and Sachs [Hydrogen isotope fractionation in freshwater algae: I. Variations among lipids and species. Organic Geochemistry 38, 582–608, 2007] demonstrated that algal lipid δD values track water δD values with high fidelity (R² > 0.99), but that D/H fractionation varied among lipids and algal species. Here we report on the influence of temperature and nitrogen limitation on D/H fractionation in lipids from cultured microalgae. Two species of freshwater green algae, Eudorina unicocca and Volvox aureus, were grown in batch culture at 15 °C and 25 °C. Increased D/H fractionation of 2?4‰/°C occurred at the higher temperature in all lipids analyzed. The marine diatom Thalassiosira pseudonana was grown in continuous culture under nitrogen replete (NR) and nitrogen limited (NL) conditions, resulting in a growth rate that was 4.4 fold lower under the latter conditions. The fatty acid content of NL cells was approximately 4 fold higher than in NR cells, whereas the sterol content was similar in both. While sterols from the NL culture were enriched in deuterium by 37‰ relative to the NR culture, fatty acids from both cultures had similar δD values, implying that D/H fractionation during isoprenoid (branched) lipid synthesis is affected by nitrogen limitation, but D/H fractionation during acetogenic (linear) lipid synthesis is not. Cross-talk of the precursor isopentenyl diphosphate between the cytosolic MVA and plastidic DOXP/MEP synthetic pathways is a plausible mechanism for the observed D/H differences between isoprenoid and acetogenic lipids. This preliminary study highlights the need to consider both the type of lipid and potential changes in growth conditions in paleoenvironmental studies using lipid D/H ratios.  相似文献   

Interactions between the Indonesian Throughflow and circulations in the Indian and Pacific Oceans   总被引：2，自引：0，他引：2  

Julian P. McCreary  Toru Miyama  Tommy Jensen  Bohyun Bang 《Progress in Oceanography》2007,75(1):70-114

Circulations associated with the Indonesian Throughflow (IT), particularly concerning subsurface currents in the Pacific Ocean, are studied using three types of models: a linear, continuously stratified (LCS) model and a nonlinear, -layer model (LOM), both confined to the Indo-Pacific basin; and a global, ocean general circulation model (COCO). Solutions are wind forced, and obtained with both open and closed Indonesian passages. Layers 1-4 of LOM correspond to near-surface, thermocline, subthermocline (thermostad), and upper-intermediate (AAIW) water, respectively, and analogous layers are defined for COCO.The three models share a common dynamics. When the Indonesian passages are abruptly opened, barotropic and baroclinic waves radiate into the interiors of both oceans. The steady-state, barotropic flow field from the difference (open − closed) solution is an anticlockwise circulation around the perimeter of the southern Indian Ocean, with its meridional branches confined to the western boundaries of both oceans. In contrast, steady-state, baroclinic flows extend into the interiors of both basins, a consequence of damping of baroclinic waves by diapycnal processes (internal diffusion, upwelling and subduction, and convective overturning). Deep IT-associated currents are the subsurface parts of these baroclinic flows. In the Pacific, they tend to be directed eastward and poleward, extend throughout the basin, and are closed by upwelling in the eastern ocean and Subpolar Gyre. Smaller-scale aspects of their structure vary significantly among the models, depending on the nature of their diapycnal mixing.At the exit to the Indonesian Seas, the IT is highly surface trapped in all the models, with a prominent, deep core in the LCS model and in LOM. The separation into two cores is due to near-equatorial, eastward-flowing, subsurface currents in the Pacific Ocean, which drain layer 2 and layer 3 waters from the western ocean to supply water for the upwelling regions in the eastern ocean; indeed, depending on the strength and parameterization of vertical diffusion in the Pacific interior, the draining can be strong enough that layer 3 water flows from the Indian to Pacific Ocean. The IT in COCO lacks a significant deep core, likely because the model’s coarse bottom topography has no throughflow passage below 1000 m. Consistent with observations, water in the near-surface (deep) core comes mostly from the northern (southern) hemisphere, a consequence of the wind-driven circulation in the tropical North Pacific being mostly confined to the upper ocean; as a result, it causes the near-surface current along the New Guinea coast to retroflect eastward, but has little impact on the deeper New Guinea undercurrent.In the South Pacific, the IT-associated flow into the basin is spread roughly uniformly throughout all four layers, a consequence of downwelling processes in the Indian Ocean. The inflow first circulates around the Subtropical Gyre, and then bends northward at the Australian coast to flow to the equator within the western boundary currents. To allow for this additional, northward transport, the bifurcation latitude of the South Equatorial Current shifts southward when the Indonesian passages are open. The shift is greater at depth (layers 3 and 4), changing from about 14°S when the passages are closed to 19°S when they are open and, hence, accounting for the northward-flowing Great Barrier Reef Undercurrent in that latitude range.After flowing along the New Guinea coast, most waters in layers 1-3 bend offshore to join the North Equatorial Countercurrent, Equatorial Undercurrent, and southern Tsuchiya Jet, respectively, thereby ensuring that northern hemisphere waters contribute significantly to the IT. In contrast, much of the layer 4 water directly exits the basin via the IT, but some also flows into the subpolar North Pacific. Except for the direct layer 4 outflow, all other IT-associated waters circulate about the North Pacific before they finally enter the Indonesian Seas via the Mindanao Current.  相似文献   

Temporal trends in δ18O composition of precipitation in Germany: insights from time series modelling and trend analysis          下载免费PDF全文

Julian Klaus  Kwok Pan Chun  Christine Stumpp 《水文研究》2015,29(12):2668-2680

Temporal and spatial variations of stable oxygen (¹⁸O) and hydrogen (²H) isotope measurements in precipitation act as important proxies for changing hydro‐meteorological and regional and global climate patterns. Temporal trends in time series of the stable isotope composition in precipitation were rarely observed, and they are poorly understood. These might be a result of a lack of proper trend detection tools and effort for exploring trend processes. Here, we investigate temporal trends of δ¹⁸O in precipitation at 17 observation stations in Germany between 1978 and 2009. We test if significant trends in the isotope time series from different models can be observed. Mann–Kendall trend tests are applied on the isotope series, using general multiplicative seasonal autoregressive integrate moving average (ARIMA) models, which account for first and higher order serial correlations. Effects of temperature, precipitation, and geographic parameters on isotope trends are also investigated in the proposed models. To benchmark our proposed approach, the ARIMA results are compared with a trend‐free pre‐whitening procedure, the state of the art method for removing the first order autocorrelation in environmental trend studies. Moreover, we further explore whether higher order serial correlations in isotope series affects our trend results. Overall, three out of the 17 stations show significant changes when higher order autocorrelation are adjusted, and four show a significant trend when temperature and precipitation effects are considered. The significant trends in the isotope time series generally occur only at low elevation stations. Higher order autoregressive processes are shown to be important in the isotope time series analysis. Results suggest that the widely used trend analysis with only the first order autocorrelation adjustment may not adequately take account of the high order autocorrelated processes in the stable isotope series. The investigated time series analysis method including higher autocorrelation and external climate variable adjustments is shown to be a better alternative. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Trends in Extremes of Surface Humidity, Temperature, and Summertime Heat Stress in China   总被引：1，自引：0，他引：1  

Julian X.L. Wang  Dian J. Gaffen 《大气科学进展》2001,18(5):742-751

l. IntroductionPrevious studies have shown climatological and seasonal surface temperature and humld-ity dlstributlons over China (Wang and Gaffen, 200l ) and evaluated trends in seasonal meansof several surface humidity variables, rainfall, temperatures, and apparent temPerature for thelast half century (Easterling et al., 2000, Zhai et al., 1999, Zhai and Eskridge, l997, Zhai andRen, l997, Wang and Gaffen, 200l). However, trends in local temperatures, and particularlytrends in extreme he…  相似文献   

Correction to: Quantifying and understanding carbon storage and sequestration within the Eastern Arc Mountains of Tanzania,a tropical biodiversity hotspot     

Simon Willcock  Oliver L. Phillips  Philip J. Platts  Andrew Balmford  Neil D. Burgess  Jon C. Lovett  Antje Ahrends  Julian Bayliss  Nike Doggart  Kathryn Doody  Eibleis Fanning  Jonathan M. H. Green  Jaclyn Hall  Kim L. Howell  Rob Marchant  Andrew R. Marshall  Boniface Mbilinyi  Pantaleon K. T. Munishi  Nisha Owen  Ruth D. Swetnam  Elmer J. Topp-Jorgensen  Simon L. Lewis 《Carbon balance and management》2017,12(1):20

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