Damage evolution in reinforced concrete columns subjected to biaxial loading   总被引：1，自引：0，他引：1  

Hugo Rodrigues  António Arêde  Humberto Varum  Aníbal Costa 《Bulletin of Earthquake Engineering》2013,11(5):1517-1540

An analysis of the damage observed in 24 reinforced concrete (RC) columns tested under uniaxial and biaxial horizontal loading is presented. The test results show that for biaxial loading conditions specific damage occurs for lower drift demands when compared with the corresponding uniaxial demand (a reduction of 50–75 % was found). The damage distribution observed in each column is also analysed. No significant differences are found in the plastic hinge length for uniaxial and biaxial loading. The drift demands associated with each damage state are compared with reference values proposed in international guidelines. Finally, and based on the philosophy of the Park and Ang uniaxial damage index, two new expressions are proposed for the evaluation of damage in RC elements under biaxial loading. The results of the application of these expressions to the experimental results are discussed.  相似文献   

Erratum to: Climate change under aggressive mitigation: the ENSEMBLES multi-model experiment     

T. C. Johns  J.-F. Royer  I. Höschel  H. Huebener  E. Roeckner  E. Manzini  W. May  J.-L. Dufresne  O. H. Otterå  D. P. van Vuuren  D. Salas y Melia  M. A. Giorgetta  S. Denvil  S. Yang  P. G. Fogli  J. Körper  J. F. Tjiputra  E. Stehfest  C. D. Hewitt 《Climate Dynamics》2011,37(5-6):1269-1270

  相似文献   

Regional hydrological cycle changes in response to an ambitious mitigation scenario     

H. Huebener  M. G. Sanderson  I. Höschel  J. Körper  T. C. Johns  J.-F. Royer  E. Roeckner  E. Manzini  J.-L. Dufresne  O. H. Otterå  J. Tjiputra  D. Salas y Melia  M. Giorgetta  S. Denvil  P. G. Fogli 《Climatic change》2013,120(1-2):389-403

Climate change impacts on the regional hydrological cycle are compared for model projections following an ambitious emissions-reduction scenario (E1) and a medium-high emissions scenario with no mitigation policy (A1B). The E1 scenario is designed to limit global annual mean warming to 2 °C or less above pre-industrial levels. A multi-model ensemble consisting of ten coupled atmosphere–ocean general circulation models is analyzed, which includes five Earth System Models containing interactive carbon cycles. The aim of the study is to assess the changes that could be mitigated under the E1 scenario and to identify regions where even small climate change may lead to strong changes in precipitation, cloud cover and evapotranspiration. In these regions the hydrological cycle is considered particularly vulnerable to climate change, highlighting the need for adaptation measures even if strong mitigation of climate change would be achieved. In the A1B projections, there are significant drying trends in sub-tropical regions, precipitation increases in high latitudes and some monsoon regions, as well as changes in cloudiness and evapotranspiration. These signals are reduced in E1 scenario projections. However, even under the E1 scenario, significant precipitation decrease in the subtropics and increase in high latitudes are projected. Particularly the Amazon region shows strong drying tendencies in some models, most probably related to vegetation interaction. Where climate change is relatively small, the E1 scenario tends to keep the average magnitude of potential changes at a level comparable to current intra-seasonal to inter-annual variability at that location. Such regions are mainly located in the mid-latitudes.  相似文献   

Adjusted radiative forcing and global radiative feedbacks in CNRM-CM5, a closure of the partial decomposition     

Olivier Geoffroy  David Saint-Martin  Aurore Voldoire  David Salas y Mélia  Stéphane Sénési 《Climate Dynamics》2014,42(7-8):1807-1818

This study provides a comprehensive global analysis of the climate radiative feedbacks and the adjusted radiative forcing for a CO₂ increase perturbation in the CNRM-CM5 climate model using the partial radiative perturbations (PRP) method. Some methodological key points of the PRP are investigated, with a particular focus on the consideration of the effect of fast adjustments. First, the standard PRP method is applied by neglecting certain fast adjustments. The effect of the field decorrelation is highlighted by performing a PRP across two different periods of a control experiment and by analyzing second-order terms. Sensitivity tests to the field substitution frequency, the sampling period and the perturbed experiment used are performed. The impact of the definition of the top of the climate system (top-of-the-atmosphere or tropopause) in the feedback estimate is also discussed. Secondly, the fast adjustment processes are taken into account by combining the PRP framework with the method of linear regression of the partial net radiative flux change against the mean surface air temperature change using a step forcing experiment. This method allows us to quantify the contribution of the different constituents to the forcing adjustment and to improve the estimation of the radiative feedbacks. It is shown that such decomposition allows the retrieval of the adjusted radiative forcing, the radiative feedbacks and the climate sensitivity as estimated with the linear regression method with a high level of accuracy, validating the partial decomposition.  相似文献   

“In-site” regionalization to estimate an intensity-duration-frequency law: a solution to scarce spatial data in Spain     

L. de Salas  J. A. Fernández 《水文研究》2007,21(25):3507-3513

The study of annual maximum rainfall intensity is quite difficult in Spain due to its limited recording rain gauges and short record lengths. This problem can't be solved applying classical regional approach, since scarce stations and great climate variability prevents forming homogeneous regions. The present study tries a new way of applying regionalization, a method which improves robustness, joining series with different durations (≤1 hour, > 1 hour) at the same station to form regions. Besides, the SQRT-ETmáx distribution is used due to extreme rainfall intensity in the Mediterranean area is not under Gumbel law domain. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Shell architecture,element composition,and stable isotope signature of the giant deep-sea oyster Neopycnodonte zibrowii sp. n. from the NE Atlantic     

Max Wisshak  Matthias López Correa  Serge Gofas  Carmen Salas  Marco Taviani  Joachim Jakobsen  André Freiwald 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(3):374-407

A conspicuous new deep-sea oyster, Neopycnodonte zibrowii sp. n., is described from the Azores Archipelago, where it thrives in 420 to >500 m water depth in high densities concealed underneath overhangs. The new species reaches a relatively large size, which may exceed 20 cm, and is characterised by a very unusual hinge line morphology, straight without a bulge of the resilium. It is compared to the extant Indo-Pacific Empressostrea kostini Huber and Lorenz, 2007 and to the cosmopolitan Neopycnodonte cochlear (Poli, 1791), which has a broadly sympatric distribution at shallower depths in the Azores and Bay of Biscay. Radiocarbon dating reveals that individuals reach an impressive lifespan of one to more than five centuries, placing them among the longest-lived molluscs known to date. They often grow on top of each other, forming stacks that resemble dish piles—an effective measure to optimise shell stability with minimal biomineralisation effort, but with the drawback of increased bioerosion ultimately leading to detachment.Three microstructure types are developed in N. zibrowii: (1) the cross-foliated, calcitic, dorsal to central endostracum and aragonitic ligostracum, (2) the porous vesicular structure of the calcitic ventral endostracum, and (3) the simple prismatic aragonitic myostracum. Foliated and vesicular shell portions show sub-millimetre-scale first-order increments delineated by conchiolin-rich growth breaks (interpreted as reproductive cyclicity), and less distinct second-order increments (interpreted as annual in nature). This pattern is clearly reflected by the elemental composition with the primary growth breaks lacking Ca and Sr but including Mg and S as organic matrix constituents. The second-order increments within the calcite are mirrored by moderately co-varying Mg/Ca and S/Ca fluctuations at stable Sr concentrations, reflecting varying proportions of organic matrix. Dorsal and central endostracum transects reveal a low inter-valve, but considerable inter-specimen variability with high Mg/Ca molar ratios and fluctuations (22.5±17.6 mmol/mol), low Sr/Ca values (0.2±0.1 mmol/mol), and a typical to high S/Ca content (6.9±2.2 mmol/mol), when compared to other calcitic bivalves.Unlike short-lived, shallow-water oysters, N. zibrowii thrives under very stable environmental conditions. Minimal temperature fluctuations and stable open marine salinity provide an optimal basis to recognise biological fractionation processes. Strong Mg/Ca fluctuations indicate a physiological control related to metabolism and biomineralisation, prohibiting the use of this ratio as a temperature or ocean chemistry proxy. Low Sr/Ca ratios indicate rather constant and low long-term accretion rates, while short-scale fluctuations may be attributed to short-term variations in growth rate and Mg incorporation. Oxygen isotopes yield a considerable spread of 1.8‰ with a mean of 2.0±0.3‰ δ¹⁸O V-PDB, and low correlation between different contemporaneous parts of the shell and between specimens. These values surprisingly exceed expected equilibrium conditions, calculated from in situ temperature data (annual mean 12.3±0.3 °C) and seawater isotopic composition (0.5±0.1‰ δ¹⁸O SMOW), by 0.5‰ on average. Such positively shifting vital effects, previously reported for limpets and barnacles, are often overlooked in high-temperature and high-amplitude settings and may be more common than is currently believed. Carbon isotopes range from 0.2 to 3.5‰ δ¹³C V-PDB (mean 1.8±0.7‰) and show an ontogenetic decrease, but may incorporate an environmental signal in adult portions, indicated by a strong correspondence of peaks between specimens. This signal is likely driven by a complex interplay of different factors, such as primary production, current-based food supply and metabolism.  相似文献   

Biostratigraphic characterization by means of ammonoids of the lower Aptian Oceanic Anoxic Event (OAE 1a) in the eastern Iberian Chain (Maestrat Basin, eastern Spain)     

J.A. Moreno-Bedmar  M. Company  T. Bover-Arnal  R. Salas  G. Delanoy  R. Martínez  A. Grauges 《Cretaceous Research》2009,30(4):864-872

It is now generally accepted that the Oceanic Anoxic Event 1a [OAE 1a] correlates with the lower part of the Leupoldina cabri planktonic foraminiferal Zone. Its calibration against the standard ammonite scale, however, seems to be more problematic. This is due, in part, to the fact that ammonites are scarce and/or of little diagnostic value from a biochronological viewpoint in the lower Aptian pelagic successions where the black shale horizons are better developed.We have been able to characterize OAE 1a geochemically in the relatively shallow water deposits of the eastern Iberian Chain (Maestrat Basin, eastern Spain), where ammonite faunas are rich. The interval corresponding to this event is dominated by the genera Roloboceras and Megatyloceras, accompanied by Deshayesites forbesi and Deshayesites gr. euglyphus/spathi. This assemblage is characteristic of the middle/upper part of the Deshayesites weissi Zone. The first occurrence of the species Deshayesites deshayesi (d'Orbigny), which marks the base of the overlying zone, takes place in our sections some metres above the OAE 1a interval.In the historical stratotype region of Cassis-La Bédoule (southern Provence Basin, southeastern France), the OAE 1a interval is also characterized by the presence of Roloboceras and Megatyloceras. Nevertheless, it has usually been correlated with the D. deshayesi Zone. In our opinion, this discrepancy is due to divergences in the taxonomic assignments of the deshayesitids present in these beds. In fact, the specimens attributed by French authors [Ropolo, P., Conte, G., Gonnet, R., Masse, J.P., Moullade, M., 2000. Les faunes d'Ammonites du Barrémien supérieur/Aptien inférieur (Bédoulien) dans la région stratotypique de Cassis-La Bédoule (SE France): état des connaissances et propositions pour une zonation par Ammonites du Bédoulien-type. Géologie Méditerranéenne 25, 167–175; Ropolo, P., Moullade, M., Gonnet, R., Conte, G., Tronchetti, G., 2006. The Deshayesitidae Stoyanov, 1949 (Ammonoidea) of the Aptian historical stratotype region at Cassis-La Bédoule (SE France), Carnets de Géologie / Notebooks on Geology Memoir 2006/01, 1–46.] to D. deshayesi and D. dechyi can be reinterpreted as belonging to D. forbesi.Following this reinterpretation, the Roloboceras beds (equivalent of OAE 1a) of Cassis-La Bédoule would also correspond to the D. weissi Zone. This age is additionally corroborated by data from southern England [Casey, R., 1961a. The stratigraphical palaeontology of the Lower Greensand. Palaeontology 3, 487–621; Casey, R., 1961b. A Monograph of the Ammonoidea of the Lower Greensand, part III. Palaeontographical Society, London, pp. 119–216], and by our recent observations in Le Teil (Ardèche Platform, southeastern France), where the Roloboceras faunas are also associated with Deshayesites consobrinus and Deshayesites gr. euglyphus, taxa that are characteristic of the D. weissi Zone.  相似文献   

A multiresolution ensemble Kalman filter using the wavelet decomposition     

Kyle S. Hickmann  Humberto C. Godinez 《Computational Geosciences》2017,21(3):441-458

We present a method of using classical wavelet-based multiresolution analysis to separate scales in model and observations during data assimilation with the ensemble Kalman filter. In many applications, the underlying physics of a phenomena involve the interaction of features at multiple scales. Blending of observational and model error across scales can result in large forecast inaccuracies since large errors at one scale are interpreted as inexact data at all scales due to the misrepresentation of observational error. Our method uses a partitioning of the range of the observation operator into separate observation scales. This naturally induces a transformation of the observation covariance and we put forward several algorithms to efficiently compute the transformed covariance. Another advantage of our multiresolution ensemble Kalman filter is that scales can be weighted independently to adjust each scale’s affect on the forecast. To demonstrate feasibility, we present applications to a one-dimensional Kuramoto-Sivashinsky (K–S) model with scale-dependent observation noise and an application involving the forecasting of solar photospheric flux. The solar flux application uses the Air Force Data Assimilative Photospheric Transport (ADAPT) model which has model and observation error exhibiting strong scale dependence. Results using our multiresolution ensemble Kalman filter show significant improvement in solar forecast error compared to traditional ensemble Kalman filtering.  相似文献   

Explosive volcanism (VEI 6) without caldera formation: insight from Huaynaputina volcano, southern Peru     

Yan Lavallée  Shanaka L. de Silva  Guido Salas  Jeffrey M. Byrnes 《Bulletin of Volcanology》2006,68(4):333-348

Through examination of the vent region of Volcán Huaynaputina, Peru, we address why some major explosive eruptions do not produce an equivalent caldera at the eruption site. Here, in 1600, more than 11 km³ DRE (VEI 6) were erupted in three stages without developing a volumetrically equivalent caldera. Fieldwork and analysis of aerial photographs reveal evidence for cryptic collapse in the form of two small subsidence structures. The first is a small non-coherent collapse that is superimposed on a cored-out vent. This structure is delimited by a partial ring of steep faults estimated at 0.85 by 0.95 km. Collapse was non-coherent with an inwardly tilted terrace in the north and a southern sector broken up along a pre-existing local fault. Displacement was variable along this fault, but subsidence of approximately 70 m was found and caused the formation of restricted extensional gashes in the periphery. The second subsidence structure developed at the margin of a dome; the structure has a diameter of 0.56 km and crosscuts the non-coherent collapse structure. Subsidence of the dome occurred along a series of up to seven concentric listric faults that together accommodate approximately 14 m of subsidence. Both subsidence structures total 0.043 km³ in volume, and are much smaller than the 11 km³ of erupted magma. Crosscutting relationships show that subsidence occurred during stages II and III when ∼2 km³ was erupted and not during the main plinian eruption of stage I (8.8 km³). The mismatch in erupted volume vs. subsidence volume is the result of a complex plumbing system. The stage I magma that constitutes the bulk of the erupted volume is thought to originate from a ∼20-km-deep regional reservoir based on petrological constraints supported by seismic data. The underpressure resulting from the extraction of a relatively small fraction of magma from the deep reservoir was not sufficient enough to trigger collapse at the surface, but the eruption left a 0.56-km diameter cored-out vent in which a dome was emplaced at the end of stage II. Petrologic evidence suggests that the stage I magma interacted with and remobilized a shallow crystal mush (∼4–6 km) that erupted during stage II and III. As the crystal mush erupted from the shallow reservoir, depressurization led to incremental subsidence of the non-coherent collapse structure. As the stage III eruption waned, local pressure release caused subsidence of the dome. Our findings highlight the importance of a connected magma reservoir, the complexity of the plumbing system, and the pattern of underpressure in controlling the nature of collapse during explosive eruptions. Huaynaputina shows that some major explosive eruptions are not always associated with caldera collapse. Editorial responsibility: J Stix  相似文献   

Wood anatomical variation of Neobuxbaumia tetetzo: A columnar Cactaceae     

S. Bernal-Salazar  T. Terrazas   《Journal of Arid Environments》2005,63(4):671-685

Anatomical variation in radial and longitudinal wood in Neobuxbaumia tetetzo was studied in four monopodic individuals. Vascular bundles in the radial direction from the pith to the vascular cambium and in the longitudinal direction from the base to the stem apex were analysed. Except for vessel density in the radial direction, the anatomical characters studied showed a pattern of cambial maturation similar to those reported for other angiosperms. The patterns of fiber anatomical variation show higher mechanical strength in the lower part of the stem, while the increase in vessel diameter towards the vascular cambium produces a positive relationship between plant water demands and larger size.  相似文献