Effects of Incoherence, Wave Passage and Spatially Varying Site Conditions on Bridge Response

2000 ◽  
pp. 413-424 ◽  
Author(s):  
P. Keshishian ◽  
A. Der Kiureghian
Keyword(s):  
Site Conditions ◽  
Wave Passage ◽  
Spatially Varying

scholarly journals Nonlinear Response of High Arch Dams to Nonuniform Seismic Excitation Considering Joint Effects

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Masoomeh Akbari ◽  
Mohammad Amin Hariri-Ardebili ◽  
Hasan Mirzabozorg
Keyword(s):  
Structural Response ◽  
Incompressible Material ◽  
Arch Dam ◽  
High Arch Dam ◽  
Arch Dams ◽  
Base Level ◽  
Nonlinear Responses ◽  
Wave Passage ◽  
Spatially Varying Ground Motions ◽  
Spatially Varying

Nonuniform excitation due to spatially varying ground motions on nonlinear responses of concrete arch dams is investigated. A high arch dam was selected as numerical example, reservoir was modelled as incompressible material, foundation was assumed as mass-less medium, and all contraction and peripheral joints were modelled considering the ability of opening/closing. This study used Monte-Carlo simulation approach for generating spatially nonuniform ground motion. In this approach, random seismic characteristics due to incoherence and wave passage effects were investigated and finally their effects on structural response were compared with uniform excitation at design base level earthquake. Based on the results, nonuniform input leads to some differences than uniform input. Moreover using nonuniform excitation increase, stresses on dam body.

Seismic Analysis of Structures Subjected to Spatially Varying Earthquake Using POD Vectors: Experimental and Analytical Studies

2020 ◽  
Vol 14 (04) ◽  
pp. 2050017
Author(s):  
K. Balamonica ◽  
N. Gopalakrishnan ◽  
A. Ramamohan Rao
Keyword(s):  
Seismic Analysis ◽  
Null Space ◽  
Time History ◽  
Soil Conditions ◽  
Classical Formulation ◽  
Local Soil ◽  
Wave Passage ◽  
Input Motion ◽  
Differential Excitation ◽  
Spatially Varying

Structures, such as bridges, pipelines which are supported at multiple places, will be subjected to differential excitation. A significant change in the correlation of the motions between the two supports is due to the combined effects of wave passage, coherency loss and local soil conditions. In the classical formulation, the response is divided into quasi-static and dynamic components and the latter is usually evaluated by time history methods or modal analysis for a linear system. In this work, the feasibility of Proper Orthogonal Decomposition (POD) vectors as a replacement for the conventional eigenvectors has been discussed. The performance of POD modes has been assessed for the uncoupled system, system having closely spaced modes. The null space vectors of the POD modes generated from the response of the structure subjected to correlated input motion were able to predict the responses of the structures subjected to spatially varying input motions. The efficiency of using the POD vectors has also been verified with the help of an experiment conducted on a steel control and safety rod drive mechanism (CSRDM) which is an example of multi-supported and differentially excited structure.

Investigation of ground-motion spatial variability effects on component and system vulnerability of a floating cable-stayed bridge

2019 ◽  
Vol 22 (8) ◽  
pp. 1923-1937 ◽  
Author(s):  
Kai Ma ◽  
Jian Zhong ◽  
Ruiwei Feng ◽  
Wancheng Yuan
Keyword(s):  
Spatial Variability ◽  
Ground Motion ◽  
Seismic Vulnerability ◽  
Site Response ◽  
Soil Condition ◽  
System Level ◽  
Soil Conditions ◽  
Cable Stayed Bridge ◽  
Wave Passage ◽  
Spatially Varying

The effects of ground-motion spatial variability on the seismic vulnerability of a floating cable-stayed bridge with 420-m long main span are investigated using component and system-level fragility analysis methods. Four combinations of the spatial variability components are considered including (a) the incoherence effect; (b) the incoherence and wave-passage effects; (c) the incoherence and site-response effects; and (d) general excitation case including the incoherence, wave-passage, and site-response effects. Parametric study was carried out to assess the sensitivity of seismic fragility to the variation of spatial variability components. The results indicate that the bridge becomes more vulnerable under spatially varying excitations than uniform excitations. The fragile components and the bridge system become more vulnerable with an increase in incoherence level. The component and system-level vulnerabilities are not sensitive to the variation of apparent wave velocities in most cases. However, the site-response effect is more complex than incoherence and wave-passage effects. There is no general trend about its effect on different components, whereas the system fragility increases as the soil conditions of adjacent excitation sites change more significantly and the soil types vary from the soft to the firm along wave-traveling direction. In addition, the bridge tends to be more vulnerable if the soil condition of the reference site becomes softer for the general excitation case. Spatial variability effects, especially incoherence and site-response effects, should be considered in the fragility analyses of this type of bridges.

A Consistent Cross-Border Seismic Hazard Methodology for Loss Estimation and Risk Management along the Border Regions of Canada and the United States

2015 ◽  
Vol 31 (1) ◽  
pp. 1-17 ◽  
Author(s):  
Paul C. Thenhaus ◽  
Kenneth W. Campbell ◽  
Nitin Gupta ◽  
David F. Smith ◽  
Mahmoud M. Khater
Keyword(s):  
United States ◽  
Seismic Hazard ◽  
The United States ◽  
Cascadia Subduction Zone ◽  
Earthquake Risk ◽  
Site Conditions ◽  
Site Factors ◽  
Local Site ◽  
Spatially Varying ◽  
Risk Managers

We provide a methodology that seamlessly integrates national seismic hazard models across the Canada-U.S. border to provide earthquake risk managers with updated and consistent seismic hazard science and technology in the two countries. Consistent with our U.S. hazard model, we developed a new Canadian model that incorporates (1) spatially varying seismicity for the major metropolitan areas of southeastern and southwestern Canada and the United States, (2) a comprehensive probabilistic model for the Cascadia subduction zone that includes M 8.0–9.2 interface earthquakes, (3) a consistent set of ground motion prediction equations across eastern and western North America, and (4) a soil-based attenuation (SBA) methodology that mitigates uncertainty in the conversion of earthquake motions from rock to soil, on which the majority of exposure is located. NEHRP site conditions are mapped for all of Canada from existing geological data, and NEHRP site factors are used to account for local site conditions.

scholarly journals Impact of Local Site Conditions on Simulation of Non-stationary Spatial Variable Seismic Motions

2021 ◽  
Author(s):  
Nassima Benmansour ◽  
Rachid Derbal ◽  
Mustapha Djafour ◽  
Salvador Ivorra ◽  
Mohammed Matallah
Keyword(s):  
Spatial Variability ◽  
Site Conditions ◽  
Seismic Excitations ◽  
Multi Scale ◽  
Seismic Motion ◽  
Local Site ◽  
Scale Structures ◽  
Wave Passage ◽  
Coherency Loss ◽  
Local Site Conditions

It is commonly accepted that multi-scale structures are subject to spatially variable seismic motions. This spatial variability of seismic motions is described by different intensities at different locations due to the coherency loss effect, wave passage effect and local site conditions. For multi-scale structures, the estimation of seismic excitations must consider these factors. Often, the influence of the spatial variability of seismic motion on the dynamic response of structures is performed by neglecting the site effect. In several cases, it has been observed that the high intensities of seismic motion are caused by the site amplification besides coherency loss and wave passage effects. This study aims to analyze the impact of local site conditions on seismic motions. For this purpose, a method of simulation of spatially variable seismic motions is performed. The seismic signals on the bedrock are defined by considering a target power spectral density and a coherency loss model. According to the seismic wave propagation theory, the projection of these seismic motions on the surface is realized. The results of this study show that neglecting the local site conditions induces an undervaluation of spatially variable seismic excitations.

Electron microscopy study of shock synthesis of silicides

1993 ◽  
Vol 51 ◽  
pp. 1162-1163
Author(s):  
Kenneth S. Vecchio
Keyword(s):  
Shock Wave ◽  
Plastic Deformation ◽  
Close Contact ◽  
Microscopy Study ◽  
High Energy ◽  
Electron Microscopy Study ◽  
Powder Materials ◽  
Porous Powder ◽  
Wave Effects ◽  
Wave Passage

Shock-induced reactions (or shock synthesis) have been studied since the 1960’s but are still poorly understood, partly due to the fact that the reaction kinetics are very fast making experimental analysis of the reaction difficult. Shock synthesis is closely related to combustion synthesis, and occurs in the same systems that undergo exothermic gasless combustion reactions. The thermite reaction (Fe2O3 + 2Al -> 2Fe + Al2O3) is prototypical of this class of reactions. The effects of shock-wave passage through porous (powder) materials are complex, because intense and non-uniform plastic deformation is coupled with the shock-wave effects. Thus, the particle interiors experience primarily the effects of shock waves, while the surfaces undergo intense plastic deformation which can often result in interfacial melting. Shock synthesis of compounds from powders is triggered by the extraordinarily high energy deposition rate at the surfaces of the powders, forcing them in close contact, activating them by introducing defects, and heating them close to or even above their melting temperatures.

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