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21.
Modified three‐dimensional seismic assessment method for buildings based on ambient vibration tests: extrapolation to higher shaking levels and measuring the dynamic amplification portion of natural torsion 
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下载免费PDF全文 This paper presents applications of the modified 3D‐SAM approach, a three‐dimensional seismic assessment methodology for buildings directly based on in situ experimental modal tests to calculate global seismic demands and the dynamic amplification portion of natural torsion. Considering that the building modal properties change from weak to strong motion levels, appropriate modification factors are proposed to extend the application of the method to stronger earthquakes. The proposed approach is consistent with the performance‐based seismic assessment approach, which entails the prediction of seismic displacements and drift ratios that are related to the damage condition and therefore the functionality of the building. The modified 3D‐SAM is especially practical for structures that are expected to experience slight to moderate damage levels and in particular for post‐disaster buildings that are expected to remain functional after an earthquake. In the last section of this paper, 16 low to mid‐rise irregular buildings located in Montreal, Canada, and that have been tested under ambient vibrations are analyzed with the method, and the dynamic amplification portion of natural torsion of the dataset is reported and discussed. The proposed methodology is appropriate for large‐scale assessments of existing buildings and is applicable to any seismic region of the world. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
22.
Spatio-temporal analysis of daily,seasonal and annual precipitation concentration in Jharkhand state,India 总被引：1，自引：0，他引：1
Reza?ZamaniEmail author Rasoul?Mirabbasi Mohammad?Nazeri Sarita?Gajbhiye?Meshram Farshad?Ahmadi 《Stochastic Environmental Research and Risk Assessment (SERRA)》2018,32(4):1085-1097
Nowadays, climate change and global warming have led to changes in the distribution of precipitation, which affect on the availability of water resources. Therefore, investigating the temporal and spatial variations of precipitation in the previous period is highly important in the future planning for flood control and local management of water resources. Considering the importance of this issue, in the present study, the precipitation concentration indices have been used for analysing precipitation changes at daily, seasonal, and annual time scales in the period of 1971 to 2011 over the Jharkhand state, India. Also, Modified Mann–Kendall test has used to study the trend of precipitation concentration indices in annual and seasonal time scales. The result shows a highly irregular and non-uniform distribution in the annual scale. For the seasonal scale an irregular and non-uniform distribution has been also observed, although the summer had a better situation than other seasons. For daily scale, none of the stations had a regular concentration and in the northeast and southern parts of the study area, there have been more irregularities. Furthermore, the results of investigating annual precipitation trend showed a combination of increasing and decreasing trend over the study area. The results of this study can be applied to manage water supplies, drainage projects, construct collection structures of urban flood, develop plans to prevent soil erosion, and designing appropriate plans to cope with drought conditions. 相似文献
23.
Hamid Reza Nassery Farshad Alijani Mohammad Nakhaei 《Arabian Journal of Geosciences》2014,7(11):4809-4818
In order to study the function, hydrodynamic behavior, and hydraulic properties of the karst aquifers in Izeh, southwest Iran, time series analysis was applied to the precipitation, spring discharge, and piezometric head data of two representative karst systems of Zagros (Ilam-Sarvak and Asmari Formations). Time series analysis was applied to two karst aquifers, those of Asmari and Ilam-Sarvak Formations. The daily precipitations of anticlines were estimated based on the precipitation–elevation function which was applied on digital elevation model (DEM) of the area. The mean estimated daily precipitations were considered in bivariate time series analysis as input data of each karst system. The total length of time series was about 2.7 years, extending from May 2007 to December 2009. During the research, several one-parameter probe data loggers were installed, which daily measure the water surfaces in karst aquifers. Time series analysis was applied for describing Izeh karst aquifers with a focus on both univariate (autocorrelation and spectral analysis) and bivariate (cross-correlation, gain function, and coherency function) methods. The results show that Asmari karst aquifer in Kamarderaz Anticline has a large storage capacity. Because of lacking a well-organized karst network, in the Asmari karst aquifer, baseflow dominates with low contribution of quick-flow. In the Ilam-Sarvak karst aquifer (Shavish and Tanush Anticlines), the karstification occurred in fractures and small diameter conduits, which caused to quick-flow between dense limestone. The Ilam-Sarvak karst aquifer could be regarded as a transition between two extreme types of karst, e.g., highly karstified system and in the opposite, extremely diffused one. The analysis of well hydrograph in Ilam-Sarvak karst aquifer shows that the karst aquifer has a low storage capacity. Unlike Asmari karst aquifer, the fractures and small diameter conduits in Ilam-Sarvak karst aquifer are more enhanced, producing a better developed karst network. Contrary to the typical karst systems, however, diffuse flow and conduit flow coexist in the Asmari Formation. 相似文献
24.
Lin Li Yi Pan Farshad Amini Kuang Cuiping Jean-Louis Briaud 《Geotechnical and Geological Engineering》2014,32(4):847-857
Post-Katrina investigations revealed that most earthen levee damage occurred on the levee crest and land-side slope as a result of either wave overtopping, storm surge overflow, or a combination of both. This study addresses erosion resistance performance of a levee strengthening technique—high performance turf reinforcement mat under combined wave and surge overtopping conditions using full-scale flume tests as well as erosion function apparatus (EFA) tests. Based on the results of full-scale flume tests, an “upper limit” of soil loss is observed for certain flow conditions. Erosion rate was presented as a function of velocity and freeboard. The effect of duration of overtopping on the erosion depth is also determined. The results of EFA tests indicate that the presence of grass roots substantially improve the critical velocity and soil erodibility. 相似文献
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26.
Active faulting and natural hazards in Armenia, eastern Turkey and northwestern Iran 总被引：1，自引：0，他引：1
Arkady S. Karakhanian Vladimir G. Trifonov Herve Philip Ara Avagyan Khaled Hessami Farshad Jamali M. Salih Bayraktutan H. Bagdassarian S. Arakelian V. Davtian A. Adilkhanyan 《Tectonophysics》2004,380(3-4):189-219
Active fault zones of Armenia, SE Turkey and NW Iran present a diverse set of interrelated natural hazards. Three regional case studies in this cross-border zone are examined to show how earthquakes interact with other hazards to increase the risk of natural disaster. In northern Armenia, a combination of several natural and man-made phenomena (earthquakes, landslides and unstable dams with toxic wastes) along the Pambak-Sevan-Sunik fault (PSSF) zone lowers from 0.4 to 0.2–0.3g the maximum permissible level (MPL) of seismic hazard that may induce disastrous destruction and loss of life in the adjacent Vanadzor depression.
In the Ararat depression, a large active fault-bounded pull-apart basin at the junction of borders of Armenia, Turkey, Iran and Azerbaijan, an earthquake in 1840 was accompanied by an eruption of Ararat Volcano, lahars, landslides, floods, soil subsidence and liquefaction. The case study demonstrates that natural hazards that are secondary with respect to earthquakes may considerably increase the damage and the casualties and increase the risk associated with the seismic impact.
The North Tabriz–Gailatu fault system poses a high seismic hazard to the border areas of NW Iran, eastern Turkey, Nakhichevan (Azerbaijan) and southern Armenia. Right-lateral strike–slip motions along the North Tabriz fault have given rise to strong earthquakes, which threaten the city of Tabriz with its population of 1.2 million.
The examples illustrate how the concentration of natural hazards in active fault zones increases the risk associated with strong earthquakes in Armenia, eastern Turkey and NW Iran. This generally occurs across the junctions of international borders. Hence, the transboundary character of active faults requires transboundary cooperation in the study and mitigation of the natural risk. 相似文献
27.
Teleconnections between oceanic–atmospheric indices and drought over Iran using quantile regressions
ABSTRACT In this research, the Bayesian quantile regression model is applied to investigate the teleconnections between large oceanic–atmospheric indices and drought standardized precipitation index (SPI) in Iran. The 12-month SPI time series from 138 synoptic stations for 1952–2014 were selected as the drought index. Three oceanic–atmospheric indices, the North Atlantic Oscillation (NAO), the Southern Oscillation Index (SOI) and the Multivariate El Niño/Southern Oscillation Index (MEI), were selected as covariates. The results show that NAO has the weakest impact on drought in different quantiles and different regions in Iran. La Niña conditions amplified droughts through all SPI quantiles in western, Caspian Sea coastal regions and southern regions. The positive phase of MEI significantly modulates low SPI quantiles (i.e. drought conditions) throughout the Zagros region, Caspian Sea coastal regions and southern regions. The study shows that the effect of large oceanic–atmospheric indices have heterogeneous impacts on extreme dry and wet conditions. 相似文献
28.
Rapid urbanization has led to extensive land-use changes,particularly in developing countries.This research is aimed to investigate the role of land use and its effect on soil and water quality in Ziarat watershed focusing on four land uses:forest,pasture,cultivated and urban development.Soil samples were taken from a depth of 0-30 cm on each land use and were analyzed by completely randomized split-plot design in two geographical directions.Results showed that bulk density(BD),electrical conductivity(EC),pH,calcium carbonate equivalent(CCE),and soil particle density(DS) of the soil samples in pastures,cultivated and urban areas increased and the mean weight diameter(MWD),soil porosity(F),organic carbons(OC),total nitrogen(TN),exchangeable cations(Ca 2+,Mg 2+,K +,Na +),cation exchange capacity(CEC) and soil microbial respirations(SMR) decreased,respectively in comparison with the forest soils.For water quality evaluations,sodium adsorption ratio(SAR),electrical conductivity(EC),pH,total dissolved solids(TDS),bicarbonate(HCO 3),chloride(Cl),total hardness(TH),calcium(Ca 2+),potassium(K +),sodium(Na +) and magnesium(Mg 2+) were investigated in two areas:Nahrkhoran and Abgir stations.Results showed that the concentration of TDS,EC and HCO 3 in Naharkhoran station is higher than that in Abgir station.On the other hand,the concentration of TDS,EC and HCO 3 in Abgir station are the relatively higher due to its location.Total hardness had the same trend during the study years except in the last three years;however,TH showed an increase of 25% TH in Naharkhoran for the last two years.Cl,K + and SAR in Naharkhoran station increased by 61%,22%,78% and 56% respectively,in comparison with Abgir station.This study demonstrated that the trend of soil degradation and mismanagement of land use may increase the frequency of urban floods and human health problems. 相似文献
29.
Sensitivity analysis of carbon fiber-reinforced elastomeric isolators based on experimental tests and finite element simulations 总被引：1，自引：0，他引：1
Conventional steel-based rubber bearings are being replaced by fiber reinforced elastomeric isolators (FREI) due to their high weight and manufacturing cost. Compared to existing rubber bearings, FREIs have superior performance and as a result can control the seismic response of structures more efficiently. This study aims to simulate the performance of rectangular carbon FREIs (C-FREIs) produced through a simple and cost-effective manufacturing process. Additionally, the effect of different factors including the number and the thickness of rubber layers, as well as the thickness of carbon fiber reinforced sheets are investigated on the performance of C-FREIs through sensitivity analyses based on the results obtained from finite element simulations. The results show that by increasing the number and thickness of rubber layers, the efficiency of C-FREIs degrades in terms of vertical strength and damping capacity, however, the performance improves in terms of lateral flexibility. Another important observation is that the increasing thickness of fiber-reinforced layers can increase the vertical rigidity of the base isolator. The vertical stiffness has the most sensitivity to the thickness of elastomeric layers and the thickness of CFR sheets while, when the number of rubber layers increases, the effective lateral stiffness is mostly affected. 相似文献
30.
Farshad Ahmadi Feridon Radmaneh Gholam Ali Parham Rasoul Mirabbasi 《Natural Hazards》2017,87(3):1313-1331
Determination of the return period of design flood depends on the nature of the project and the consequences of the flood and is based on economic criteria, human casualties, and hydrological factors. Underestimation of flood might result in casualties and economic damages, while the overestimation leads to capital waste. Therefore, in this research, the flood frequency analysis of Dez Basin, Iran was conducted within the period of 1956–2012 using power law approach together with ordinary distributions, including normal, log normal, Pearson type III, exponential, gamma, generalized extreme value, Nakagami, Rayleigh, logistic, generalized logistic, generalized Pareto, and Weibull distributions. The power law comes from the fractal nature of earth science phenomena such as precipitation and runoff. Accordingly, in this research the partial duration flood series of five hydrometric stations in Dez Basin were extracted using power law with the intervals of 7, 14, 30, and 60 days and then compared with the annual maxima. The results indicated that the annual maxima were not suitable for frequency analysis of the flood in Dez Basin, and the 30-day partial duration series obtained from the power law has a better correspondence with the flow and properties of the Dez Basin. The independence and stationarity of the 30-day partial duration series were examined by Wald–Wolfowitz test, confirming the independence of the considered series. Next, the power distribution and the typical statistical distributions were fitted onto the data of the flood in Dez Basin, with the performance of each distribution being investigated using normalized root-mean-square error and Nash–Sutcliffe criteria. The results revealed that in the SDZ and TPB stations, power distribution had a better performance than other considered distributions. Moreover, in the SDS, TPS, and TZ stations the power distribution stood in the second rank in terms of the best distribution. As the performance of power distribution in the estimation of the flood in Dez Basin has been very satisfactory and calculation of its parameters and its application is easier than ordinary probability distributions, thus it can be suggested as the superior distribution for flood frequency analysis in Dez Basin. 相似文献