Cyclic tests on large‐scale models of existing bridge piers with rectangular hollow cross‐section     

A. V. Pinto  J. Molina  G. Tsionis 《地震工程与结构动力学》2003,32(13):1995-2012

Cyclic tests on two large‐scale models of existing bridge piers with rectangular hollow cross‐section were performed in the ELSA laboratory. The prototype structure is an existing reinforced concrete highway bridge constructed in Austria in 1975. The piers presented several seismic deficiencies and consequently they showed poor hysteretic behaviour and limited deformation capacity as well as undesirable failure modes that do not comply with the requirements of modern codes for seismic‐resistant structures. Experimental data are compared to numerical and empirical predictions. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

On the circulation in the East Frisian Wadden Sea: numerical modeling and data analysis     

Emil V. Stanev  Jörg-Olaf Wolff  Hans Burchard  Karsten Bolding  Götz Flöser 《Ocean Dynamics》2003,53(1):27-51

 In this paper we use a combination of numerical modeling and data analysis to gain a better understanding of the major characteristics of the circulation in the East Frisian Wadden Sea. In particular, we concentrate on the asymmetry of the tidal wave and its modulation in the coastal area, which results in a complex pattern of responses to the sea-level forcing from the North Sea. The numerical simulations are based on the 3-D primitive equation General Estuarine Transport Model (GETM) with a horizontal resolution of 200 m and terrain-following vertical coordinates. The model is forced at its open boundaries with sea-level data from an operational model for the German Bight (German Hydrographic Office). The validation data for our model simulations include time series of tidal gauge data and surface currents measured at a pile in the back-barrier basin of the Island Langeoog, as well as several ADCP transects in the Accumer Ee tidal inlet. Circulation and turbulence characteristics are investigated for typical situations driven by spring and neap tides, and the analysis is focused on dominating temporal and spatial patterns. By investigating the response of five back-barrier basins with rather different morphologies to external forcing, an attempt is made to elucidate the dominating physical balances controlling the circulation in the individual sub-basins. It is demonstrated that the friction at the seabed tends to slow down the tidal signal in the shallow water. This leads to the establishment of flood dominance in the shallow sea north of the barrier islands. South of the islands, where the water volume of the channels at low tide is smaller than the tidal prism, the asymmetry of the tidal signal is shifted towards ebb dominance, a feature which is particularly pronounced at spring tide. At the northern open boundary, the tidal wave propagating from west to east generates a sea-level difference of ∼1 m along the boundary, and thereby triggers vigorous alongshore currents. The frictional control in the model is located in the inlets, as well as along the northern boundary. The correlation between velocity and turbulent kinetic energy tends to the establishment of a net southward transport, giving theoretical support to the observed accumulation of sediments on the intertidal flats. Weak turbulence along the northern shores of the barrier islands and the small magnitude of the residual currents there promote accumulation of suspended matter in these areas, although wave action will generally counteract this effect. Received: 29 May 2002 / Accepted: 26 September 2002 Responsible Editor: Jean-Marie Beckers Acknowledgements We are indebted to S. Dick for providing the data from the operational model of BSH and to B. Flemming for the useful discussions. The topography data and Fig. 1 have been prepared in cooperation with F. Meyer. Figure 2 has been prepared by G. Brink-Spalink. We also thank for the comments from an anonymous reviewer which helped to improve our paper.  相似文献   

Two and Half Dimensional Simulation of Ridge Effects on the Ground Motion Characteristics     

J. P. Narayan  P. V. Prasad Rao 《Pure and Applied Geophysics》2003,160(8):1557-1571

— Seismic responses of weathered and non-weathered ridge models were simulated to study the ridge effects on the ground motion characteristics. The range of ridge slope from 19.98° to 45° was considered to produce a possible set of generalized results. 2.5-D modeling based on parsimonious staggered grid approximation of elastodynamic wave equations was adopted in simulations. Computed results reveal an increase of amplitude of incoming waves with both elevation and the slope of the ridge. Further, the characteristics of surface waves are highly ridge slope dependent. The analysis of responses of weathered and non-weathered ridge models reveals that ridge has caused a strong generation of surface waves near its top. The surface waves are not dominating on the top of the ridge but at some lower elevation. The increase of weathering of ridge further intensified the ridge effect. Analysis in frequency domain, based on spectral ratio method, does not indicate any pattern in the spectral amplification factor and is very much sensitive to slope, source focal mechanism and location. However, on an average there is a continuous decrease of amplification with slope in the vertical component and increase in the transverse component, and it is increasing in the radial component up to slope =38.0° and thereafter decreasing.  相似文献   

Present-Day Issues of Studies and Use of Groundwater for Drinking Needs     

Borevskii  B. V.  Yazvin  L. S.  Zektser  I. S. 《Water Resources》2003,30(4):467-470

  相似文献   

Studies of Hydrochemical and Kinetic Characteristics of Small Water Bodies in the Context of Their Eutrophication     

Gribovskaya  I. V.  Ivanova  E. A.  Kalacheva  G. S.  Kravchuk  E. S. 《Water Resources》2003,30(1):68-71

Comparison study data on the hydrochemical parameters, bacterio- and phytoplankton, and reduction–oxidation characteristics of two ponds in Krasnoyarsk are presented. These water bodies are of interest due to the fact that the ecosystems of these natural model objects respond to eutrophication in different ways. It is assumed that the reason for this difference is in the hydrophysical characteristics depending on the morphology of the basins of the water bodies rather than in the hydrochemical characteristics.  相似文献   

Transformation of the Ebro River Delta under the Impact of Intense Human-Induced Reduction of Sediment Runoff   总被引：1，自引：0，他引：1  

Mikhailova  M. V. 《Water Resources》2003,30(4):370-378

The regularities of the Ebro River delta formation and the impact of hydraulic construction on the river sediment runoff are discussed. As shown, the drastic reduction of the sediment runoff after the construction of two large reservoirs in the lower river reaches in the 1960s slowed down the delta protrusion and intensified the delta coastline washout.  相似文献   

Fishery Water Releases to the Lower Pool of the Volgograd Hydroelectric Power Plant     

Ratkovich  D. Ya.  Vyruchalkina  T. Yu.  Solomonova  I. V. 《Water Resources》2003,30(4):387-403

Conditions of fish reproduction in the Volga–Caspian Basin depending on the hydrological regime in the Volga lower reaches, transformed by water withdrawals and regulatory impact of reservoirs are considered.  相似文献   

Numerical viscoelastic modelling by the spectral Laguerre method   总被引：1，自引：0，他引：1  

B.G. Mikhailenko  A.A. Mikhailov  G.V. Reshetova 《Geophysical Prospecting》2003,51(1):37-48

Seismic wave propagation in a viscoelastic media can be described by a system of integro-differential equations. The solution of such equations requires special methods when using finite-difference techniques in the time domain. In the frequency domain, the integral terms are represented by complex elastic parameters. This paper presents an efficient algorithm for viscoelastic modelling based on the integral Laguerre transform for the approximation of temporal derivatives and for the calculation of convolution integrals. For the calculation of spatial derivatives, it is possible to use various methods: finite-difference and finite-element techniques, spectral and pseudo-spectral methods. We then obtain a system of algebraic equations with a matrix independent of the parameter m , i.e. the degree of the Laguerre polynomials. In this case, only the right-hand side of the system has recurrent dependence on the parameter m , which is an analogue of the temporal frequency in the frequency domain. The obtained system with a large number of right-hand sides can be solved using fast methods, where the matrix is transformed only once, as opposed to the frequency-domain approach, when the matrix is transformed for each temporal frequency.  相似文献   

3D F–K and finite-difference dip moveout in cross-spreads     

Andrey V. Masjukov 《Geophysical Prospecting》2003,51(4):333-345

A 3D F–K dip-moveout (DMO) is developed, which is applicable to data acquired in an elementary single-fold cross-spread. The key idea is that a 3D log-stretch transform and the inherent regularity of the cross-spread geometry make it possible to transform 3D Fourier DMO. The derived theory generalizes the 2D Fourier shot-gather DMO in the log-stretch domain; 2D turns out to be a special case. Similarly to 2D, the cross-spread DMO becomes convolutional after multidimensional logarithmic stretch. The proposed method works for orthogonal and slanted acquisition geometries; the cross-spread DMO relationships are found to be independent of the intersection angle of the shot and receiver lines. In contrast to integral (Kirchhoff-style) methods, the cross-spread F–K DMO does not degrade from the inevitable irregularity in 3D sampling of offsets in a CMP gather. The newly derived F–K DMO operator can be approximated by finite-difference (FD) schemes; the low-order FD cross-spread DMO equation is shown to be the 3D extension of the Bolondi and Rocca offset continuation. It is shown that F–K and low-order FD operators are effective in a synthetic case.  相似文献   

An Environmentally Friendly Decontamination Protocol for Ground Water Sampling Devices     

Louise V. Parker  Thomas A. Ranney 《Ground Water Monitoring & Remediation》2003,23(2):84-91

Several detergent-washing/air-drying decontamination protocols were tested to determine their ability to remove residual contamination from two types of ground water sampling devices. We tested a relatively simply constructed device, a bailer, and a much more complex, and theoretically more difficult to decontaminate, bladder pump. The devices were decontaminated after sampling ground water that was contaminated with organics that varied in their hydrophobic nature and propensity to be sorbed by the materials in the devices. These studies showed that a hot-detergent wash, hot-water rinse, and hot-air drying protocol was effective.  相似文献