Performance of a high damping rubber bearing base isolation system for a shear beam structure     

Yu Chen  Goodarz Ahmadi 《地震工程与结构动力学》1994,23(7):729-744

Performance of High Damping Laminated Rubber Bearing (HD-LRB) base isolation system in protecting the structure and the structural content is studied. A non-uniform shear beam structural model is considered, and the generalized non-stationary Kanai–Tajimi model for the El Centro 1940 earthquake is used as excitation. The technique of equivalent linearization is utilized and the mean-square response statistics of secondary systems and primary structure are evaluated. Statistically estimated peak responses of the secondary system and the primary structure are evaluated and the results are compared with the response spectra for the actual earthquake accelerogram. Comparison of the stochastic responses for base-isolated structures with the HD-LRB and the linear Laminated Rubber Bearing (LRB) and the fixed-base structure is also carried out. It is shown that the HD-LRB system significantly reduces the mean-square, as well as the peak acceleration and deflection responses without generating large base displacements. Furthermore, the non-linear behaviour of the HD-LRB somewhat improves the performance of the bearing in reducing the peak responses of the secondary system and the primary structure when compared with the linear LRB model.  相似文献   

Petrology and geochemistry of the granitoid complex of Boroujerd, Sanandaj-Sirjan Zone, Western Iran     

A. Ahmadi Khalaji  D. Esmaeily  M.V. Valizadeh  H. Rahimpour-Bonab 《Journal of Asian Earth Sciences》2007,29(5-6):859-877

The Middle Jurassic Boroujerd Granitoid Complex of the Sanandaj-Sirjan Zone (with a U–Pb zircon age of 169–172 Ma) was emplaced in an active continental margin setting. This complex consists of three main units: an elongate NW–SE extending granodioritic unit (SiO₂ = 58–71 wt%), which is widespread throughout the area, a quartz-dioritic unit (SiO₂ = 52–63 wt%), exposed as small stocks within the granodioritic body, and a monzogranitic unit (SiO₂ = 70–75 wt%), widely scattered as separate small outcrops through the southern part of the area. A series of NW trending aplites and pegmatites are present in the granodioritic unit and its aureole.Geochemically this complex is metaluminous to slightly peraluminous, typical of I-type granites. It belongs to high-K calc-alkaline series and displays the geochemical characteristics typical of volcanic arc granites related to an active continental margin (e.g. significant Nb, Ti, P and Sr depletion). Isotopic data (Sr_i = 0.7062–0.7074 and εNd_t = −3.02 to −3.62) are consistent with a crustal protolith. In addition, fractional crystallization may have played an important role in the formation of the whole spectrum of the granitoid types that occur in the Boroujerd area.  相似文献   

On multicomponent gas diffusion and coupling concepts for porous media and free flow: a benchmark study     

Ahmadi  Navid  Heck  Katharina  Rolle  Massimo  Helmig  Rainer  Mosthaf  Klaus 《Computational Geosciences》2021,25(5):1493-1507

Computational Geosciences - Multicomponent gas transport in porous media and at the interface between porous media and free flow occurs in a wide range of technical and environmental systems....  相似文献   

A possible continuum theory for densification and liquefaction of saturated sand     

Goodarz Ahmadi 《Mathematical Geology》1981,13(1):37-52

A previously developed continuum theory of granular media is applied to the problems of densification and liquefaction of saturated sand. An expression for the free energy of saturated sand is developed. The process of densification of sand subjected to cyclic shear stress is studied and several expressions for an increase of the solid volume fraction are obtained and discussed. The problem of the initial liquefaction of saturated sand samples under cyclic shear stress is then considered and several criteria relating the shear stress amplitude, over-burden pressure, time to liquefaction, and physical properties of the sand sample are established. Some semiempirical relations for field applications are also presented.  相似文献   

Mental health preparedness for natural disasters in Iran     

Naghmeh Sadeghi  Mohammad H. Ahmadi 《Natural Hazards》2008,44(2):243-252

Appropriate emergency preparedness and response rely on social, economical, cultural, and political infrastructures, which vary widely according to the level of the development of each country. Mental health damages are among the consequences of absence of such infrastructure, which have not been studied comprehensively till to date. In most countries, planning for natural disasters and earthquakes has been mainly focused on physical and economical impacts; however, lessons learnt from recent earthquakes in Iran and other countries show that psychological impacts need to be considered more seriously. The first responder to an emergency is really the affected community, which consequently should be mentally prepared by appropriate training programs. These should include simple psychosocial interventions developed for people with average level of education in a way to be easily understandable and practicable. After the Bam earthquake, local community volunteers have been selected and trained to provide post-disaster mental health services.  相似文献   

Modelling thermal comfort of visitors at urban squares in hot and arid climate using NN-ARX soft computing method     

Shahab Kariminia  Shervin Motamedi  Shahaboddin Shamshirband  Jamshid Piri  Kasra Mohammadi  Roslan Hashim  Chandrabhushan Roy  Dalibor Petković  Hossein Bonakdari 《Theoretical and Applied Climatology》2016,124(3-4):991-1004

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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   

Impact of climate change on diffuse pollutant fluxes at the watershed scale          下载免费PDF全文

Mehdi Ahmadi  Rosemary Records  Mazdak Arabi 《水文研究》2014,28(4):1962-1972

This study aims to assess watershed‐scale impacts of changing climate on sediment, phosphorus, nitrogen and pesticide (atrazine) fluxes over the 21st century at the watershed scale. In particular, changes in dissolved and particulate forms of water quality constituents in response to climate change are investigated. The hydrologic model Soil and Water Assessment Tool was calibrated and evaluated in a primarily agricultural watershed in the Midwestern United States to simulate hydrologic and water quality processes on a daily basis over the 2015–2099 time horizon. The model was then driven with 112 distinct statistically downscaled climate projections representing Intergovernmental Panel on Climate Change Special Report on Emissions Scenarios (IPCC SRES) low, moderate and high greenhouse gas emission scenarios. Projected hydrologic and water quality responses were categorized according to the three IPCC SRES emission scenarios for summarizing and synthesizing results over early‐century (2015–2034), mid‐century (2045–2064) and late‐century (2080–2099) assessment. Results revealed clear warming trends in the study area, whereas small increases in precipitation were predicted. Streamflow, sediment and total nutrient loads did not differ noticeably between assessment periods. However, the proportion of dissolved to total nutrients increased significantly from early‐century to late‐century periods. With the exception of total atrazine in the mid‐century period, predicted pollutant loads for a given assessment period did not differ between emission pathways for a given assessment period. Changes in pollutant fluxes showed pronounced monthly variability. The projected increase in readily available forms of nutrients has important implications for the ecological health of water systems and management of drinking water supplies. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Evaluation of floodplain variability considering impacts of climate change     

Mohammad Karamouz  Navideh Noori  Ali Moridi  Azadeh Ahmadi 《水文研究》2011,25(1):90-103

In this study, an approach is presented for handling hydraulic uncertainties in the prediction of floodplain. Different factors affect river flood characteristics. Furthermore, the high changeability of flooding conditions leads to high variability of the inundation. River morphology is one of the most effective factors in river flood characteristics. This factor is influenced by sedimentation and erosion in the river cross sections, which affects the discharge variation. The depth and the width of the river cross section lead to an increase or decrease in the river flow path. This results in changes in the extent of the floodplain based on the generated rainfall. The inundated region boundaries are determined by utilizing the mean first‐order second‐moment analysis. The proposed method is applied to the Kajoo River in the south‐eastern part of Iran. Determination of floodplain uncertainty is a damage‐reduction policy in this region. Also, it is useful to prepare the necessary activities for overcoming the flood hazards. Climate change is the second effective factor on the floodplain uncertainties. Climate change affects the magnitude, extent and depth of inundation and it may intensify the flood problem. Therefore, the future rainfall pattern of the study area under climate change is simulated to evaluate its impacts on the river flow characteristic. Subsequently, a hydraulic routing model is used to determine floodplain. Finally, the copula function is used to estimate the joint probability of the changes in the inundation area due to changes in river morphology and the rainfall changes due to impacts of climate change. Results show that the uncertainties of the extent of floodplain are affected by climate change and river morphology, leading to noticeable changes in the magnitude and frequency of floods. Evaluating these impacts and estimating corresponding river discharges will help in the study of river dynamics, and will also contribute towards devising effective mitigation and management strategies. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Combining suspended sediment monitoring and fingerprinting to determine the spatial origin of fine sediment in a mountainous river catchment   总被引：2，自引：0，他引：2  

Olivier Evrard  Oldrich Navratil  Sophie Ayrault  Mehdi Ahmadi  Julien Némery  Cédric Legout  Irène Lefèvre  Alain Poirel  Philippe Bonté  Michel Esteves 《地球表面变化过程与地形》2011,36(8):1072-1089

An excess of fine sediment (grain size <2 mm) supply to rivers leads to reservoir siltation, water contamination and operational problems for hydroelectric power plants in many catchments of the world, such as in the French Alps. These problems are exacerbated in mountainous environments characterized by large sediment exports during very short periods. This study combined river flow records, sediment geochemistry and associated radionuclide concentrations as input properties to a Monte Carlo mixing model to quantify the contribution of different geologic sources to river sediment. Overall, between 2007 and 2009, erosion rates reached 249 ± 75 t km^?2 yr^?1 at the outlet of the Bléone catchment, but this mean value masked important spatial variations of erosion intensity within the catchment (85–5000 t km^?2 yr^?1). Quantifying the contribution of different potential sources to river sediment required the application of sediment fingerprinting using a Monte Carlo mixing model. This model allowed the specific contributions of different geological sub‐types (i.e. black marls, marly limestones, conglomerates and Quaternary deposits) to be determined. Even though they generate locally very high erosion rates, black marls supplied only a minor fraction (5–20%) of the fine sediment collected on the riverbed in the vicinity of the 907 km² catchment outlet. The bulk of sediment was provided by Quaternary deposits (21–66%), conglomerates (3–44%) and limestones (9–27%). Even though bioengineering works conducted currently to stabilize gullies in black marl terrains are undoubtedly useful to limit sediment supply to the Bléone river, erosion generated by other substrate sources dominated between 2007 and 2009 in this catchment. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献