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An investigation into the effects of damping and nonlinear geometry models in earthquake engineering analysis 
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下载免费PDF全文 The growing emphasis of considering the behavior of structures at extreme performance states, such as collapse, has necessitated the characterization of the effects of varying attributes of the structural model. One source of variability that has not previously been considered is variability in the mathematical model. This study investigated the effects of changing the geometric nonlinearity approach and damping model on a four‐story buckling restrained braced frame, a four‐story steel moment resisting frame, and an eight‐story steel moment resisting frame. The variations in behavior are quantified using the maximum interstory drift ratio as the performance metric and qualified by comparing the relative displaced shapes and component response histories at the collapse performance state. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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The concept of the hybrid passive control system is studied analytically by investigating the seismic response of steel frame structures. Hybrid control systems consist of two different passive elements combined into a single device or system. The hybrid systems investigated in this research consist of a rate‐dependent damping device paired with a rate‐independent energy dissipation element. The innovative configurations exploit individual element strengths and offset their weaknesses through multiphased behavior. A nine‐story, five‐bay steel moment‐frame was used for the analysis. Six different seismic resisting systems were analyzed and compared. The conventional systems included a special moment‐resisting frame (SMRF) and a dual SMRF–buckling‐restrained brace (BRB) system. The final four configurations are hybrid passive systems. The different hybrid configurations utilize a BRB and either a high‐damping rubber damper or viscous fluid damper. The analyses were run in the form of an incremental dynamic analysis. Several damage measures were calculated, including maximum roof drift, base shear, and total roof acceleration. The results demonstrate the capability of hybrid passive control systems to improve structural response compared with conventional lateral systems and to be effective for performance‐based seismic design. Each hybrid configuration improved some aspect of structural response with some providing benefits for multiple damage measures. The multiphased nature provides improved response for frequent and severe seismic events. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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M. L. Kaplan J. J. Charney K. T. WaightIII K. M. Lux J. D. Cetola A. W. Huffman A. J. Riordan S. D. Slusser M. T. Kiefer P. S. Suffern Y.-L. Lin 《Meteorology and Atmospheric Physics》2006,94(1-4):235-270
Summary In this paper, we will focus on the real-time prediction of environments that are predisposed to producing moderate-severe
(hazardous) aviation turbulence. We will describe the numerical model and its postprocessing system that is designed for said
prediction of environments predisposed to severe aviation turbulence as well as presenting numerous examples of its utility.
The purpose of this paper is to demonstrate that simple hydrostatic precursor circulations organize regions of preferred wave
breaking and turbulence at the nonhydrostatic scales of motion. This will be demonstrated with a hydrostatic numerical modeling
system, which can be run in real time on a very inexpensive university computer workstation employing simple forecast indices.
The forecast system is designed to efficiently support forecasters who are directing research aircraft to measure the environment
immediately surrounding turbulence.
The numerical model is MASS version 5.13, which is integrated over three different grid matrices in real-time on a university
workstation in support of NASA-Langley’s B-757 turbulence research flight missions. The model horizontal resolutions are 60,
30, and 15 km and the grids are centered over the region of operational NASA-Langley B-757 turbulence flight missions.
The postprocessing system includes several turbulence-related products including four turbulence forecasting indices, winds,
streamlines, turbulence kinetic energy, and Richardson numbers. Additionally there are convective products including precipitation,
cloud height, cloud mass fluxes, lifted index, and K-index. Furthermore, soundings, sounding parameters, and Froude number
plots are also provided. The horizontal cross section plot products are provided from 16,000–46,000 feet in 2,000 feet intervals.
Products are available every three hours at the 60 and 30 km grid interval and every 1.5 hours at the 15 km grid interval.
The model is initialized from the NWS ETA analyses and integrated two times a day. 相似文献
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Despite the growing recognition that metropolitan real estate markets are segmented spatially and that property development is still profoundly local, research has taken little notice of agents that actually initiate and propel the development process. Earlier studies that aimed at identifying metropolitan segmentation employed statistical techniques whilst ignoring the practices of agents that might shed light on the notion of segmentation. Greater Toronto’s office market, which is Canada’s largest, exemplifies a real estate market far more spatially segmented than the downtown–suburban framework, a dichotomy so extensively use in research. Locational preferences of the numerous developers that work in this market tend to be highly localized, confirming deep-rooted segmentation. Their preferences correspond to submarket classification and follow dividing lines that crisscross the metropolitan region, emphasizing the extent and the power of parochialism, which defines the nature of real estate development. 相似文献
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Palestinian suicide terrorism has been a key feature in the latest phase of the Israeli–Palestinian conflict. During the past decade, and particularly since September 2000, there has been a substantial increase in the use of this type of warfare. Recent studies suggest that, contrary to common belief, suicide terrorism is highly rational and driven by strategic considerations. This article explores the rationality of Palestinian suicide terrorism from a geographical perspective. It is argued that suicide terrorism works along two parallel paths: rationality and randomness. It complies with geographical fundamentals, and target selection is highly rational, subject to spatial considerations such as distance, agglomeration, and accessibility. As the permeability to Israel became more difficult, suicide bombers and their organizers had to adopt more flexible practices which emphasized other spatial considerations. Timing is of importance both for strategic and tactical reasoning. Obstructing negotiations and peace talks has been a salient objective, but the exact timing of suicide bombings has been influenced by tactical considerations, which aim at maximizing casualties. 相似文献
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M. L. Kaplan A. W. Huffman K. M. Lux J. D. Cetola J. J. Charney A. J. Riordan Y.-L. Lin K. T. Waight III 《Meteorology and Atmospheric Physics》2005,88(3-4):153-173
Summary Simulation experiments reveal key processes that organize a hydrostatic environment conducive to severe turbulence. The paradigm requires the juxtaposition of the entrance region of a curved jet streak, which is highly subgeostrophic, with the entrance region of a straight jet streak, which is highly supergeostrophic. The wind and mass fields become misphased as the entrance regions converge, resulting in significant spatial variation of inertial forcing, centripetal forcing, as well as along and cross-stream pressure gradient forcing over a meso- scale region. Maxima of these forces are misphased where the two dissimilar jet streaks converge and geostrophic balance is disrupted. Velocity divergence within the subgeostrophic region of largest upstream-directed pressure gradient force and velocity convergence near the region of largest downstream-directed centripetal/inertial-advective forcing act to produce a mesoscale front due to spatially varying confluent flow flanked by zones of increasing velocity divergence. This results in frontogenesis as well as the along-stream divergence of cyclonic and convergence of cyclonic ageostrophic vertical vorticity. The nonuniform centripetally forced mesoscale front becomes the locus of large gradients of ageostrophic vertical vorticity along an overturning isentrope. This region becomes favorable for streamwise vorticity gradient formation enhancing the environment for the organization of horizontal vortex tubes in the presence of buoyant forcing. This is because the mesoscale convergence of vertical vorticity on an overturning isentropic surface creates vertical rotation for the development of horizontal vorticity in regions where isentropic surfaces overturn. Vorticity, shear, and buoyancy are focused in one location by this front thus favoring an environment favorable for microvortex formation leading to turbulence. 相似文献
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Response to Professor John Hall's discussion of Hardyniec and Charney's paper, ‘An investigation into the effects of damping and nonlinear geometry models in earthquake engineering analysis’ 下载免费PDF全文
下载免费PDF全文 The discussion presents questions regarding the recommended damping scheme from the discussed paper and provides an alternative recommendation. The discussion also requests further explanation on behavioral differences between models incorporating the P‐delta and corotational approaches that are presented in the paper. Responses to these questions are presented. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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Coral branches partially block the flow of water through the colony, creating an inner zone of reduced water exchange where hypoxic conditions can develop during the night. Previous studies have shown that this oxygen deficiency is alleviated by the fanning behavior of mutualistic damselfish that spend the night between the coral branches, constantly moving their fins. Our findings show that fin‐stroking frequency during fanning by the damselfish Dascyllus marginatus is moderately plastic, with lower frequency under higher oxygen concentration, and vice versa. The inter‐play between oxygen concentration and fin motion maintains nearly steady oxygen concentration between the coral branches during the night. 相似文献