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191.
Sonia L. Parvanova Petia S. Dineva George D. Manolis Frank Wuttke 《Bulletin of Earthquake Engineering》2014,12(2):981-1005
In this work, we examine the seismic response of multiple tunnels reinforced with liners and buried within the elastic homogeneous half-plane in the presence of surface relief. The seismic waves are upward propagating, time-harmonic, horizontally polarized shear (SH) waves. More specifically, we examine: (a) the scattered wave fields along the free surface and inside the half-plane with the embedded tunnels; (b) the dynamic stress concentration factors that develop at the soil-liner interfaces; (c) the stresses and displacements that develop inside the tunnel liners. We use a sub-structuring technique that is based on the direct boundary element method to model each constituent part of the problem separately. Then, assembly of the full problem is accomplished through the imposition of compatibility and equilibrium conditions at all interfaces. Next, a detailed verification study is carried out based on comparisons against available analytical and/or numerical results for a series of test examples. Subsequently, detailed numerical simulations are conducted and the results of these parametric studies reveal the influence of the following key parameters on the soil-tunnel system response: (a) the shape of the free-surface relief; (b) the depth of placement of the tunnels and their separation distance; (c) the SH-wavelength to tunnel diameter ratio; (d) the elastic properties of the tunnel lining rings and (e) the dynamic interaction effects between the free-surface relief and the tunnels. 相似文献
192.
Oliver Wetter Christian Pfister Johannes P. Werner Eduardo Zorita Sebastian Wagner Sonia I. Seneviratne Jürgen Herget Uwe Grünewald Jürg Luterbacher Maria-Joao Alcoforado Mariano Barriendos Ursula Bieber Rudolf Brázdil Karl H. Burmeister Chantal Camenisch Antonio Contino Petr Dobrovolný Rüdiger Glaser Iso Himmelsbach Andrea Kiss Oldřich Kotyza Thomas Labbé Danuta Limanówka Laurent Litzenburger Øyvind Nordl Kathleen Pribyl Dag Retsö Dirk Riemann Christian Rohr Werner Siegfried Johan Söderberg Jean-Laurent Spring 《Climatic change》2014,125(3-4):349-363
The heat waves of 2003 in Western Europe and 2010 in Russia, commonly labelled as rare climatic anomalies outside of previous experience, are often taken as harbingers of more frequent extremes in the global warming-influenced future. However, a recent reconstruction of spring–summer temperatures for WE resulted in the likelihood of significantly higher temperatures in 1540. In order to check the plausibility of this result we investigated the severity of the 1540 drought by putting forward the argument of the known soil desiccation-temperature feedback. Based on more than 300 first-hand documentary weather report sources originating from an area of 2 to 3 million km2, we show that Europe was affected by an unprecedented 11-month-long Megadrought. The estimated number of precipitation days and precipitation amount for Central and Western Europe in 1540 is significantly lower than the 100-year minima of the instrumental measurement period for spring, summer and autumn. This result is supported by independent documentary evidence about extremely low river flows and Europe-wide wild-, forest- and settlement fires. We found that an event of this severity cannot be simulated by state-of-the-art climate models. 相似文献
193.
Oliver Wetter Christian Pfister Johannes P. Werner Eduardo Zorita Sebastian Wagner Sonia I. Seneviratne Jürgen Herget Uwe Grünewald Jürg Luterbacher Maria-Joao Alcoforado Mariano Barriendos Ursula Bieber Rudolf Brázdil Karl H. Burmeister Chantal Camenisch Antonio Contino Petr Dobrovolný Rüdiger Glaser Iso Himmelsbach Andrea Kiss Oldřich Kotyza Thomas Labbé Danuta Limanówka Laurent Litzenburger Øyvind Nordli Kathleen Pribyl Dag Retsö Dirk Riemann Christian Rohr Werner Siegfried Johan Söderberg Jean-Laurent Spring 《Climatic change》2014,125(3-4):365-367
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Geoffrey M. Morrison Sonia Yeh Anthony R. Eggert Christopher Yang James H. Nelson Jeffery B. Greenblatt Raphael Isaac Mark Z. Jacobson Josiah Johnston Daniel M. Kammen Ana Mileva Jack Moore David Roland-Holst Max Wei John P. Weyant James H. Williams Ray Williams Christina B. Zapata 《Climatic change》2015,131(4):545-557
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The effectiveness of Tuned Mass Dampers (TMD) on buildings subjected to moderate and high-intensity motions is analysed. First, the response of a 22-storey four-bay reinforced concrete non-linear frame with a TMD is studied for motions with different intensities. Several values of the relevant parameters are assumed in the analyses. Then, equivalent single-degree-of-freedom systems with TMDs and without them are defined and analysed under the action of ground motions with intensities associated with different return intervals at the site where the structures are located. Vulnerability curves for the systems are obtained based on the probabilities of reaching two different performance limit states. The expected annual rate of exceedance of each limit state is calculated. The results show that the effectiveness of TMDs is higher for systems with small non-linearity produced by small and moderate earthquakes, than for systems with high non-linear behaviour, generally associated with high-intensity motions. Some recommendations about the applicability of TMD are given. Copyright © 1999 John Wiley & Sons Ltd. 相似文献
198.
The influence of late Quaternary sedimentation on vegetation in an Amazonian lowland megafan 下载免费PDF全文
Dilce F. Rossetti Rogério Gribel Hanna Tuomisto Carlos L.O. Cordeiro Sonia H. Tatumi 《地球表面变化过程与地形》2018,43(6):1259-1279
The largest areas of white‐sand vegetation in northern Amazonia are confined to Late Pleistocene–Holocene megafan depositional systems, which suggest a relationship between the two. The aim of this work is to determine: (i) the relative role of sedimentary history and recent ecological processes to explaining the mosaic of white‐sand forest patches, grasslands and shrublands in a wetland area of northern Amazonia; and (ii) the long‐term successional trajectory that led to the establishment of the white‐sand forest patches. Facies analysis was used to reconstruct the megafan paleoenvironment; δ13C, total organic carbon and carbon/nitrogen from sedimentary organic matter to reconstruct the past vegetation; and floristic inventories to characterize the modern vegetation. The results revealed that the Viruá megafan consists of various sandy sub‐environments, including aeolian sand dunes and sheets developed mostly in the Holocene after the megafan turned inactive as a depositional site. Dune margins and tops are colonized by white‐sand trees mixed with a few generalist rain‐forest species, whereas adjacent lower‐lying areas, which are affected by seasonal flooding, are covered by graminoid plants and/or shrubs. The latter initiated their development over the megafan surface in different times of the Holocene due to hydrological gradients imposed by the topography of the various megafan depositional environments, while the white‐sand forest became dominant only on sand dunes over the last few centuries. We suggest that the late Quaternary sedimentary history was crucial in creating morphologies that now determine topographic gradients responsible for different vegetation physiognomies over the Amazonian lowlands. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
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