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991.
Influence of the construction process and nonstructural components on the modal properties of a five‐story building 下载免费PDF全文
Rodrigo Astroza Hamed Ebrahimian Joel P. Conte José I. Restrepo Tara C. Hutchinson 《地震工程与结构动力学》2016,45(7):1063-1084
A full‐scale five‐story reinforced concrete building was built and tested on the NEES‐UCSD shake table during the period from May 2011 to May 2012. The purpose of this test program was to study the response of the structure and nonstructural components and systems (NCSs) and their dynamic interaction during seismic base excitation of different intensities. The building specimen was tested first under a base‐isolated condition and then under a fixed‐based condition. As the building was being erected, an accelerometer array was deployed on the specimen to study the evolution of its modal parameters during the construction process and placement of major NCSs. A sequence of dynamic tests, including daily ambient vibration, shock (free vibration) and forced vibration tests (low‐amplitude white noise and seismic base excitations), were performed on the building at different stages of construction. Different state‐of‐the‐art system identification methods, including three output‐only and two input‐output methods, were used to estimate the modal properties of the building. The obtained results allow to investigate in detail the effects of the construction process and NCSs on the dynamic parameters of this building system and to compare the modal properties obtained from different methods, as well as the performance of these methods. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
992.
Eric Martin Simon Gascoin Youen Grusson Clément Murgue Mélanie Bardeau François Anctil Sylvain Ferrant Romain Lardy Patrick Le Moigne Delphine Leenhardt Vincent Rivalland José-Miguel Sánchez Pérez Sabine Sauvage Olivier Therond 《Surveys in Geophysics》2016,37(2):223-247
Natural and anthropogenic forcing factors and their changes significantly impact water resources in many river basins around the world. Information on such changes can be derived from fine scale in situ and satellite observations, used in combination with hydrological models. The latter need to account for hydrological changes caused by human activities to correctly estimate the actual water resource. In this study, we consider the catchment area of the Garonne river (in France) to investigate the capabilities of space-based observations and up-to-date hydrological modeling in estimating water resources of a river basin modified by human activities and a changing climate. Using the ISBA–MODCOU and SWAT hydrological models, we find that the water resources of the Garonne basin display a negative climate trend since 1960. The snow component of the two models is validated using the moderate-resolution imaging spectroradiometer snow cover extent climatology. Crop sowing dates based on remote sensing studies are also considered in the validation procedure. Use of this dataset improves the simulated evapotranspiration and river discharge amounts when compared to conventional data. Finally, we investigate the benefit of using the MAELIA multi-agent model that accounts for a realistic agricultural and management scenario. Among other results, we find that changes in crop systems have significant impacts on water uptake for agriculture. This work constitutes a basis for the construction of a future modeling framework of the sociological and hydrological system of the Garonne river region. 相似文献
993.
Populus nigra L. establishment and fluvial landform construction: biogeomorphic dynamics within a channelized river 下载免费PDF全文
Dov Corenblit Johannes Steiger Gaspard Charrier José Darrozes Virginia Garófano‐Gómez Alexandre Garreau Eduardo González Angela M. Gurnell Borbála Hortobágyi Frédéric Julien Luc Lambs Sébastien Larrue Thierry Otto Erwan Roussel Franck Vautier Olivier Voldoire 《地球表面变化过程与地形》2016,41(9):1276-1292
Populations of the riparian pioneer species Populus nigra L. which establish on alluvial bars within river channels modulate sediment dynamics and fluvial landforms. Dense cohorts of P. nigra have colonized gravel point bars along the channelized River Garonne, France, during the last 20 years and have enhanced the vertical, lateral and longitudinal development of the bars. For this period, the geomorphic characteristics of two wooded point bars on this laterally stable river are closely linked to the spatial distribution and intensity of establishment and resistance of different cohorts of P. nigra. Furthermore, P. nigra colonization dynamics were controlled by engineer effects of this same species. This relationship is illustrated by a significant correlation between key geomorphic and biological variables measured in situ and characterized with a set of four aerial photographs taken between 2000 and 2010. The development of wooded point bars, which are discrete biogeomorphic units, over the studied period, appear to result from a specific biogeomorphic positive feedback of matter aggregation and vegetation establishment related to sediment trapping and stabilization by pioneer engineer plants. We propose a conceptual model of biogeomorphic unit construction for channelized, lateral stable rivers. We consider the resultant biogeomorphic units as functional from an ecological point of view because P. nigra enhances at the cohort scale (i) its own inherent capacity to resist hydrogeomorphic disturbances, and (ii) its resilience capacity as a result of successful colonization, especially downstream of mature poplar stands. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
994.
Giovanni Vezzoli Eduardo Garzanti Stephen J. Vincent Sergio Andò Andrew Carter Alberto Resentini 《地球表面变化过程与地形》2014,39(8):1101-1114
This article investigates landscape characteristics and sediment composition in the western Greater Caucasus by using multiple methods at different timescales. Our ultimate goal is to compare short‐term versus long‐term trends in erosional processes and to reconstruct spatio‐temporal changes in sediment fluxes as controlled by partitioning of crustal shortening and rock uplift in the orogenic belt. Areas of active recent uplift are assessed by quantitative geomorphological techniques [digital elevation model (DEM) analysis of stream profiles and their deviation from equilibrium] and compared with regions of rapid exhumation over longer time intervals as previously determined by fission‐track and cosmogenic‐nuclide analyses. Complementary information from petrographic and heavy‐mineral analyses of modern sands and ancient sandstones is used to evaluate erosion integrated throughout the history of the orogen. River catchments displaying the highest relief, as shown by channel‐steepness indices, correspond with the areas of most rapid exhumation as outlined by thermochronological data. The region of high stream gradients is spatially associated with the highest topography around Mount Elbrus, where sedimentary cover strata have long been completely eroded and river sediments display the highest metamorphic indices and generally high heavy‐mineral concentrations. This study reinforces the suggestion that the bedrock–channel network can reveal much of the evolution of tectonically active landscapes, and implies that the controls on channel gradient ultimately dictate the topography and the relief along the Greater Caucasus. Our integrated datasets, obtained during a decade of continuing research, display a general agreement and regularity of erosion patterns through time, and consistently indicate westward decreasing rates of erosional unroofing from the central part of the range to the Black Sea. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
995.
This paper presents the history of badland generated in the Saldaña region, Spain; as well as the main responses eight decades after the start of restoration – in terms of vegetation, soil and erosive processes. The restoration consisted of intense reforestation and construction of more than 100 check dams and numerous wattle fences. Presently, the dense vegetation (87% cover) contrasts markedly with the degraded landscape from the early 20th century (5% cover). The thickness of litter and the natural presence of some species (Quercus pyrenaica, Paeonia broteroi and Lactarius deliciosus) clearly indicate the recovery of the site. The development of the forest cover shows that the intervention has the potential to recover almost 90% of the area. There is also evidence of soil regeneration, although some properties (erodibility, resistance to penetration and shear‐strength resistance) are not that different between the forested and degraded areas. In the restored zones, runoff is negligible, since a thick layer of moss covers the spillways of all the check dams. Erosion has almost been stopped by the effects of vegetation cover, litter and higher infiltration rates (infiltration rate in forested slopes is 43.4 times greater than in bare slopes). Sediment detachment, such as landslides, mudflows and piping, still occur, but are restricted to the degraded zones. Furthermore, even when sediments are mobilized from the upper degraded hillslopes during the larger storms events (2000–2010), check dams and the lower elevation restored forest‐buffers effectively work to reduce the sediment yield into the Carrión River by almost three orders of magnitude (<102 mg L‐1), compared with data from the 1930s and 1940s (>105 mg L‐1). Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
996.
Daniel Käser Tobias Graf Fabien Cochand Rob McLaren René Therrien Philip Brunner 《Ground water》2014,52(6):827-836
Recent models that couple three‐dimensional subsurface flow with two‐dimensional overland flow are valuable tools for quantifying complex groundwater/stream interactions and for evaluating their influence on watershed processes. For the modeler who is used to defining streams as a boundary condition, the representation of channels in integrated models raises a number of conceptual and technical issues. These models are far more sensitive to channel topography than conventional groundwater models. On all spatial scales, both the topography of a channel and its connection with the floodplain are important. For example, the geometry of river banks influences bank storage and overbank flooding; the slope of the river is a primary control on the behavior of a catchment; and at the finer scale bedform characteristics affect hyporheic exchange. Accurate data on streambed topography, however, are seldom available, and the spatial resolution of digital elevation models is typically too coarse in river environments, resulting in unrealistic or undulating streambeds. Modelers therefore perform some kind of manual yet often cumbersome correction to the available topography. In this context, the paper identifies some common pitfalls, and provides guidance to overcome these. Both aspects of topographic representation and mesh discretization are addressed. Additionally, two tutorials are provided to illustrate: (1) the interpolation of channel cross‐sectional data and (2) the refinement of a mesh along a stream in areas of high topographic variability. 相似文献
997.
998.
Denis Ramón Avellán José Luis Macías Giovanni Sosa-Ceballos Gema Velásquez 《Bulletin of Volcanology》2014,76(2):1-19
Apoyeque volcano, located 9 km northwest of Managua city, erupted explosively at 12.4 ka. The Plinian eruption deposited a widespread pumice fall deposit known as the Upper Apoyeque Tephra (UAq). The UAq is massive, reversely graded, and consists of white juvenile pumice (~78 vol.%), a variety of cognate lithics and accidental altered lithics. The whole-rock pumice composition is rhyodacitic (SiO2?=?66.9–68.5 wt.%) with a mineral paragenesis of plagioclase, orthopyroxene, clinopyroxene, amphibole, titanomagnetite, and ilmenite in a rhyolitic glass groundmass (SiO2?=?74.4?±?0.6 wt.%). The deposit’s dispersal axis is to the south, with the deposit covering a minimum area of 877 km2 within the 50 cm isopach and has a total volume of 3 km3 (dense rock equivalent, 1.15 km3). The eruption column reached a maximum height of ca.28 km. The eruption ejected a total mass of 3?×?1012 kg at an average rate of 2?×?108 kg/s, and based on available models, we infer duration of almost 4 h. Petrographic and geochemical characteristics suggest that the eruption was triggered by magma mixing. 相似文献
999.
José Morales Juan V. Cantavella Flor de Lis Mancilla Lucía Lozano Daniel Stich Encarnación Herraiz José B. Martín José A. Lopez-Comino José M. Martinez-Solares 《Bulletin of Earthquake Engineering》2014,12(5):1871-1888
The Lorca 2011 seismic series was recorded by an unprecedented set of high quality on scale broadband seismograms and strong motion accelerograms. The waveforms from permanent and temporary broadband seismic networks deployed in the region by different institutions allowed to invert regional moment tensor for the fore, main and largest aftershock of the complete seismic sequence. Using double-difference algorithm we have performed a precise relocation of the seismic series, where body wave travel times from strong ground motion accelerograms were included in the data set. Regional moment tensor inversion for the three main events show similar oblique-reverse faulting regime with a northeast-southwest fault orientation. The scalar seismic moment, moment magnitude and focal depth retrieved from the inversion yield the following values for each event: \(\hbox {Mo}=6.5\times 10^{16}\) Nm (Mw = 5.2) for the mainshock, \(\hbox {Mo}= 9.6 \times 10^{15}\) Nm (Mw = 4.6) for the foreshock and \(\hbox {Mo}=7.3\times 10^{14}\) Nm (Mw = 3.9) for the large aftershock. The centroid depths range between 4 and 6 km. The double-difference relocation of the seismic series shows significant epicentral differences with the preliminary routine location. The epicentral solutions given by this relocation show a seismic sequence distributed following a NE–SW strike, subparallel to the Alhama de Murcia fault and compatible with the faulting parameters inverted from the moment tensor analysis. The hypocenters of the series generate a subvertical trend in depth distribution, being concentrated between 2 and 6 km. The depth distribution of the main events, which range from 4.6 to 5.5 km, is in good relationship with the faulting and depth parameters deduced from the moment tensor inversion technique. The regional moment tensor solutions for the three largest earthquakes, the epicentral distribution and the focal depths show good relationship with the surface geometry and tectonic regime of the Alhama de Murcia fault. The stress drop deduced for the mainshock gives a value ranging between 58 and 85 bars, which does not support the idea of a high stress drop release as a main factor contributing to the high ground acceleration recorded at Lorca. The PGA values observed at Lorca, which contributed to the high damage independently of structural deficiencies, could be generated mainly by shallowness and proximity to the seismic source together with a directivity effect in the seismic radiation. 相似文献
1000.