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Search Results: 1 - 10 of 43741 matches for " Seismic analysis. "
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Towards Earthquake Shields: A Numerical Investigation of Earthquake Shielding with Seismic Crystals  [PDF]
Baris Baykant Alagoz, Serkan Alagoz
Open Journal of Acoustics (OJA) , 2011, DOI: 10.4236/oja.2011.13008
Abstract: Authors numerically demonstrate that the seismic surface waves from an earthquake can be attenuated by a seismic crystal structure constructed on the ground. In the study, seismic crystals with a lattice constant of kilometer are investigated in the aspect of band gaps (Stop band), and some design considerations for earthquake shielding are discussed for various crystal configurations in a theoretical manner. Authors observed in their FDTD based 2D wave simulation results that the proposed earthquake shield can provide a decreasing in magnitude of surface seismic waves. Such attenuation of seismic waves might reduce the damage in an earthquake.
Structural Effect on Hydrocarbon Trapping, North Western Nile Delta, Egypt  [PDF]
Elhamy A. Tarabees, Salah S. Azam
International Journal of Geosciences (IJG) , 2016, DOI: 10.4236/ijg.2016.73028
Abstract: The present study aims to interpret the available data, that derived from well logs and 2-D seismic reflection data, in the area located northeast onshore Nile Delta, in order to delineate its structural styles and its relation with the basement inferences and regional tectonic, and also to detect the possible existence of hydrocarbon accumulation at the Tertiary-Quaternary sedimentary section. The study area lies between latitudes 30°31' and 31°17'N, and longitudes 30°38' and 31°21'E. Using the available well logs, the average velocity gradients are calculated at El-Wastani, Kafr El Sheikh, Abu Madi, Qawasim and Sidi Salem Formations and velocity contour maps are constructed. The available 2-D seismic sections were interpreted and utilized to construct the isochronous reflection maps to the tops of the fore-mentioned five formations. These maps were converted into depth maps. The depth maps show the predominance of three tectonic trends. The structure contour maps were used to deduce the structural elements affecting the fore-mentioned formations in the area under study. These maps reflect the abundance of the E-W trending faults (sometimes ENE-WSW and in other times WNW-ESE), which characterize the general Mediterranean Sea trend. The second system of structural deformations is trending NE-SW (Syrian arc trend). The third type of faults is the NW-SE trending features (Red Sea faults trend). By integrating the structure contour maps together with the different kinds of maps have been done using different sources of data such as velocity data, the possible locations that can be oil traps for hydrocarbon accumulation have been detected.
A Comparison of Saudi Building Code with 1997 UBC for Provisions of Modal Response Spectrum Analysis Using a Real Building  [PDF]
Tariq M. Nahhas
Open Journal of Earthquake Research (OJER) , 2017, DOI: 10.4236/ojer.2017.62006
Abstract: The study uses an actual building to compare the modal response spectrum analysis results of Saudi Building Code (SBC) and the 1997 Uniform Building Code (UBC) used in Saudi Arabia before the introduction of SBC. A sample of four buildings with reported analysis of comparison between IBC and UBC is taken for confirming the comparison. Eight sample places from SBC map for Saudi Arabia together with two sample places of high seismic activity in USA were taken for the comparisons. The study used software package ETABS in this study for modeling and analysis. The results are dissimilar from the comparisons reported for test places of USA. It is concluded that at most places SBC base shear is higher for both ELFP and MRSA. However, the results cannot be generalized and considered always right. The same is factual for overturning moments. Consequently, we cannot report that SBC is more conservative than UBC for all scenarios.
Seismic Signal and Data Analysis of Rock Media with Vertical Anisotropy  [PDF]
Yuan Zhao, Nan Zhao, Lin Fa, Meishan Zhao
Journal of Modern Physics (JMP) , 2013, DOI: 10.4236/jmp.2013.41003
Abstract:

This paper is concerned with anisotropic effects on seismic data and signal analysis for transversely isotropic rock media with vertical anisotropy. It is understood that these effects are significant in many practical applications, e.g. earthquake forecasting, materials exploration inside the Earth’s crust, as well as various practical works in oil industry. Under the framework of the most accepted anisotropic media model (i.e. VTI media, transverse isotropy with a vertical axis symmetry), with applications of a set of available anisotropic rock parameters for sandstone and shale, we have performed numerical calculations of the anisotropic effects. We show that for rocks with strong anisotropy, the induced relative depth error can be significantly large. Nevertheless, with an improved understanding of the seismic-signal propagation and proper data processing, the error can be reduced, which in turn may enhance the probability of forecasting accurately the various wave propagations inside the Earth’s crust, e.g. correctly forecasting the incoming earthquakes from the center of the Earth.

Comparative study of codes for the seismic design of structures
Santos, S. H. C.;Lima, S. S.;Arai, A.;
Revista IBRACON de Estruturas e Materiais , 2012, DOI: 10.1590/S1983-41952012000600006
Abstract: a general evaluation of some points of the south american seismic codes is presented herein, comparing them among themselves and with the american standard asce/sei 7/10 and with the european standard eurocode 8. the study is focused in design criteria for buildings. the western border of south america is one of the most seismically active regions of the world. it corresponds to the confluence of the south american and nazca plates. this region corresponds roughly to the vicinity of the andes mountains. this seismicity diminishes in the direction of the comparatively seismically quieter eastern south american areas. the south american countries located in its western border possess standards for seismic design since some decades ago, being the brazilian standard for seismic design only recently published. this study is focused in some critical topics: definition of the recurrence periods for establishing the seismic input; definition of the seismic zonation and design ground motion values; definition of the shape of the design response spectra; consideration of soil amplification, soil liquefaction and soil-structure interaction; classification of the structures in different importance levels; definition of the seismic force-resisting systems and respective response modification coefficients; consideration of structural irregularities and definition of the allowable procedures for the seismic analyses. a simple building structure is analyzed considering the criteria of the several standards and obtained results are compared.
Optimal design and earthquake-resistant design evaluation of low-rise framed RC structure  [PDF]
Reyes Indira Herrera, Juan Carlos Vielma, Ronald Ugel, Yolsanie Martínez, Alex Barbat
Natural Science (NS) , 2012, DOI: 10.4236/ns.2012.428089
Abstract: This study evaluates the seismic response of an existing two stories RC building using non-linear analysis. The original model was resized and there were obtained two buildings designed under two different methodologies to fulfill the Venezuelan codes requirements for a high seismic hazard. An elastic analysis was applied to the original building in order to verify interstory drifts; the resizing building it was designed under requirements of strong column-wake beam condition. A third building was modeled according to the seismic displacement design procedure. It were performed non-linear static analysis and 2D and 3D dynamic analyses, obtaining capacity curves, structural ductility, structural performance point, global and interstory drifts for each building. Torsional effects for the resizing building were also computed from 3D analysis. In the original building it was obtained a weak seismic behavior, while resized buildings presented good seismic performance under the Limits States evaluated in this study.
Seismic Response of a Typical Fixed Jacket-Type Offshore Platform (SPD1) Under Sea Waves  [PDF]
Khosro Bargi, S. Reza Hosseini, Mohammad H. Tadayon, Hesam Sharifian
Open Journal of Marine Science (OJMS) , 2011, DOI: 10.4236/ojms.2011.12004
Abstract: Offshore platforms in seismically active areas should be designed to service severe earthquake excitations with no global structural failure. In seismic design of offshore platforms, it is often necessary to perform a dynamic analysis that accounts for nonlinear pile soil structures interaction effects. This paper summarizes the nonlinear dynamic analysis of a 3-D model of a typical Jacket-Type platform which is installed in Persian Gulf (SPD1), under simultaneously wave and earthquake loading has been conducted. It is assumed that they act in the same and different directions. The interaction between soil and piles is modeled by equivalent pile length theory. The structure is modeled by finite element method (Ansys Inc.). It be concluded that when the longitudinal components of the earthquake and wave are in different directions, an increase on the response of platform can be seen.
Parameters Identification of Stochastic Nonstationary Process Used in Earthquake Modelling  [PDF]
Giuseppe Carlo Marano, Mariantonietta Morga, Sara Sgobba
International Journal of Geosciences (IJG) , 2013, DOI: 10.4236/ijg.2013.42027
Abstract:

This paper proposes a new deterministic envelope function to define non-stationary stochastic processes modeling seismic ground motion accelerations. The proposed envelope function modulates the amplitude of the time history of a stationary filtered white noise to properly represent the amplitude variations in the time histories of the ground motion accelerations. This function depends on two basic seismological indices: the Peak Ground Acceleration (PGA) and the kind of soil. These indices are widely used in earthquake engineering. Firstly, the envelope function is defined analytically from the Saragoni Hart’s function. Then its parameters are identified for a set of selected real records of earthquake collected in PEER Next Generation Attenuation database. Finally, functions of the parameters depending on the Peak Ground Acceleration and the kind of soil are defined from these identified values of the parameters of the envelope function through a regression analysis.

Seismic Capacity Assessment of Existing RC Buildings in The Sudan by Using Pushover Analysis  [PDF]
Mohammed Ismaeil, Mohamed Sobaih, Adel Akl
Open Journal of Civil Engineering (OJCE) , 2015, DOI: 10.4236/ojce.2015.52016
Abstract: Recently, the evaluation of seismic performance of existing buildings has received a great attention. Current research works and observations indicate that The Sudan have low-to-moderate seismic regions. Most of existing buildings are designed only for gravity load. The objective of this paper is to assess the seismic performance of existing RC buildings in The Sudan. Four typical buildings were investigated using pushover analysis according to ATC-40. They were designed according to the Regulations for earthquake-resistant design of buildings in Egypt (ESEE) and International Building Code (IBC2012). Results showed that the buildings designed considering by ESEE and IBC2012 loads were found adequate and satisfied the Immediate Occupancy (IO) acceptance criteria according to ATC-40. The comparison of the pushover curve shows that the stiffness of frames is larger when using ESEE Regulations compared to the IBC2012 design. This means that ESEE design procedure provides a greater capability to resist seismic load than the IBC2012 design.
Effects of Building Configuration on Seismic Performance of RC Buildings by Pushover Analysis  [PDF]
Yasser Alashker, Sohaib Nazar, Mohamed Ismaiel
Open Journal of Civil Engineering (OJCE) , 2015, DOI: 10.4236/ojce.2015.52020
Abstract: In the recent earthquakes, concrete structures have been severely damaged or collapsed, which has raised questions against the seismic adequacy of existing buildings. These existing reinforced concrete buildings need to be evaluated to determine the capacity to resist seismic loads. The behavior of a building during earthquakes depends critically on its overall shape, size and geometry. Conventional approach to earthquake resistant design of buildings depends upon providing the building with strength, stiffness and inelastic deformation capacity which are great enough to withstand a given level of earthquake-generated force. This is generally accomplished through the selection of an appropriate building configuration and the careful detailing of structural members. In this research, nonlinear pushover analysis has been used to evaluate the seismic performance of three buildings with three different plans having same area and height. This method determines the base shear capacity of the building and performance level of each part of building under varying intensity of seismic force. The results of effects of different plan on seismic response of buildings have been presented in terms of displacement, base shear and plastic hinge pattern.
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