Finite element modeling assumptions impact on seismic response demands of MRF-buildings     

Shehata E Abdel Raheem  Ahmed K Abdel Zaher  Ahmed MA Taha 《地震工程与工程振动(英文版)》2018,17(4):821-834

Recent seismic events have raised concerns over the safety and vulnerability of reinforced concrete moment resisting frame “RC-MRF” buildings. The seismic response of such buildings is greatly dependent on the computational tools used and the inherent assumptions in the modelling process. Thus, it is essential to investigate the sensitivity of the response demands to the corresponding modelling assumption. Many parameters and assumptions are justified to generate effective structural finite element (FE) models of buildings to simulate lateral behaviour and evaluate seismic design demands. As such, the present study focuses on the development of reliable FE models with various levels of refinement. The effects of the FE modelling assumptions on the seismic response demands on the design of buildings are investigated. the predictive ability of a FE model is tied to the accuracy of numerical analysis; a numerical analysis is performed for a series of symmetric buildings in active seismic zones. The results of the seismic response demands are presented in a comparative format to confirm drift and strength limits requirements. A proposed model is formulated based on a simplified modeling approach, where the most refined model is used to calibrate the simplified model.  相似文献   

Histopathologic biomarker response of clam, <Emphasis Type="Italic">Ruditapes decussates</Emphasis>, to organophosphorous pesticides reldan and roundup: A laboratory study     

Nahla S. El-Shenawy  Tarak I. S. Moawad  Mahmoud E. Mohallal  Ismail M. Abdel-Nabi  Inas A. Taha 《Ocean Science Journal》2009,44(1):27-34

Clam Ruditapes decussates was used as a biomonitoring organism to measure the potential impact of pollution. The present study investigated histological alterations of R. decussates following a long-term exposure to a sublethal-level of pesticides Reldan and Roundup. The clams were taken to the laboratory and kept for days to adjust to a continuous closed flow system with quality water control. After the adjustment period, clams were exposed either to sublethal concentrations of Reldan (0.6 μl L^?1) or Roundup (1.1 μl L^?1) for 90 days. Clams were taken to determine the histological damage at 30, 60 and 90 days. Most histological alterations were highly localized in the glandular cells of the gills, mantle tissues and digestive gland; secretions of glandular cells were found to be increased by increasing the time of exposure. Histopathological results showed the activation of resistance mechanisms that allowed the clams to survive under sublethal stresses. Thus, histological changes on localized tissues were sensitive and they have positive correlation to the time of exposure to the pesticides, suggesting that they may serve as biomarkers for Reldan and Roundup exposures.  相似文献   

Site specific probabilistic seismic hazard analysis at Dubai Creek on the west coast of UAE   总被引：2，自引：1，他引：1  

Ayman A. Shama 《地震工程与工程振动(英文版)》2011,10(1):143-152

A probabilistic seismic hazard analysis (PSHA) was conducted to establish the hazard spectra for a site located at Dubai Creek on the west coast of the United Arab Emirates (UAE). The PSHA considered all the seismogenic sources that affect the site, including plate boundaries such as the Makran subduction zone, the Zagros fold-thrust region and the transition fault system between them; and local crustal faults in UAE. PSHA indicated that local faults dominate the hazard. The peak ground acceleration (PGA) for the 475-year return period spectrum is 0.17 g and 0.33 g for the 2,475-year return period spectrum. The hazard spectra are then employed to establish rock ground motions using the spectral matching technique.  相似文献   

Hydrochemical evolution and variation of groundwater and its environmental impact at Sohag, Egypt   总被引：1，自引：0，他引：1  

Ayman A. Ahmed  Mohamed H. Ali 《Arabian Journal of Geosciences》2011,4(3-4):339-352

Groundwater resources of Sohag, Egypt are currently threatened by contamination from agricultural and urbanization activities. Groundwater in Sohag area has a special significance where it is the second source for fresh water used for agricultural, domestic, and industrial purposes. Due to growing population, agriculture expansion, and urbanization, groundwater quality assessment needs more attention to cope with the increasing water demand in this arid zones and limited water resources. The aim of this paper is to address the integrated role of geochemical processes, agriculture and urbanization in evolution of groundwater composition, and their impact on groundwater quality to help in management and protection of groundwater resources of study area using geochemical modeling techniques and geographical information systems. Spatial variation of groundwater hydrochemical properties, rock–water interaction, ion exchange, and assessment of groundwater quality were investigated. Results indicated that groundwater properties are varied spatially and its evolution in the study area is generally controlled by the prevailed geochemical processes represented by leaching, dissolution, and precipitation of salts and minerals, ion exchange, in addition to human activities represented by agriculture and urbanization as well as climatic and poor drainage conditions. Management alternatives should be followed in the study area to avoid degradation of groundwater quality and provide sustainable development.  相似文献   

Geo-environmental effect of landfill site, southeast of Riyadh, Saudi Arabia     

Oumar Allafouza Loni  M. Tahir Hussein  Ayman M. Alrehaili 《Arabian Journal of Geosciences》2013,6(6):2021-2033

Landfilled wastes manifest slow decomposition, producing emanation of gases, and outflow of leachate. Waste mass shows various chemical reactions and complex evolutions that occur under the influence of natural agents, as rain and microorganisms. These reactions lead to biological, physical, and chemical transformations of wastes. The intensity of the phenomenon is related to the air and the humidity. These factors originate from the initial composition of the solid waste, the operating mode of the landfill, and the geological and hydrogeological conditions. Leachate is considered a major source of groundwater pollution. It has a complex nature; it typically contains high concentrations of chemical hazardous including heavy metals, chemical compounds that may severely pollute the environment. These challenges are faced all over the world by environment protection agencies and waste management bodies. The challenge differs according to the specific situation of the site, the climatic, environmental, and geological factors. The international literature is rich with studies in this concern. Each country or region of the world has its own legislation and laws governing waste management, e.g., the European Commission Legislation, the US Environmental Agency, and so forth. The main objective of this study is to shed light on the environmental consequences of a landfill site located in the southeast of Riyadh City, Saudi Arabia. It constitutes a peculiar case because of its situation, its exploitation mode, and nature of buried wastes. The study made use of satellite MSS, TM, ETM and SPOT image 2007, and Digital Elevation Model (DEM), respectively. Geological, morphological, hydrological, hydrochemical, and detailed drainage analyses were performed. Records of meteorological stations were also used in this study. The satellite images illustrate the evolution of the site through time since its start in the 1990s of the twentieth century. The main geological units outcropping in the area are the Sulaiy Formation, the Yamama Formation, Khabra deposits, floodplain deposits, alluvium, and sheet gravel. Drainage analyses shows a dendritic nature for the network, a total area of 2,113 km², basin slope of 0.016, perimeter of 430?×?10³, and a mean elevation of 635 m. Annual rainfall is around 100 mm, evapotranspiration is about 2,900 mm, wind speed averages at 5.1 km/h, and runoff peak is within 2.7–4.7 m³/s. A plume of total dissolved solids and nitrates was observed to initiate from the landfill site. Heavy metal concentration confirms the same result. Planners, environmentalists, decision makers, and other interest groups can use the findings of this study for environmental management of the landfill and protection of the downstream part of the Sulaiy tributary from leachate contamination. The results indicate the importance of monitoring landfills through the combined use of ground and satellite monitoring.  相似文献   

"Biostratigraphy and Paleoecology of Paleocene/Eocene (P/E) interval of some geological sections in Central Egypt"     

Mohamed Youssef  Saida Taha 《Arabian Journal of Geosciences》2013,6(11):4279-4298

The Paleocene/Eocene boundary intervals were studied in three outcrops along the Nile Valley: Gabal Taramsa, Gabal Qreiya, and Gabal Nag El Quda in Qena and Esna regions. The planktonic and benthic foraminifera have been examined. The qualitative study of planktonic foraminifera distinguishes eight planktonic biozones from (P4 and P5) Paleocene age to (E1, E2, E3, E4, E5, and E6) Early Eocene age. The analysis of quantitative distribution patterns of benthic foraminifera allows the reconstruction of the paleoenvironmental settings in the studied area. The disappearance or scarce appearance of deeper-water benthic foraminifera (Angulogavelinella avnimelechi and Gavelinella rubiginosus) and increasing dominance of shallow-marine taxa (Buliminides, Loxostomoides applinae) indicate deposition in shallow water environments. The benthic foraminiferal assemblages which dominated by Loxostomoides applinae, Buliminids, and Lenticulina indicate Dysoxic conditions and maximum food levels. The species of mid-way type fauna dominate the assemblages of the studied area; the species of Velasco-type fauna are very rare.  相似文献   

Magneto-seismic studies of the eastern Qattara Depression,Northwestern desert,Egypt     

Taha Rabeh 《Russian Geology and Geophysics》2012,53(9):916-925

The potential field data are considered the main supporting factor in the geophysical exploration process for detecting and evaluating the subsurface structures. Therefore, a detailed land magnetic survey was performed in an area subjected to seismic investigations. The main target of this study was to detect the deeper subsurface structures and to investigate their possible relationships with earthquake activity.The RTP aeromagnetic map was used to detect the regional extension of the structures interpreted from the land magnetic survey. The RTP land and aeromagnetic maps were interpreted by the filtering technique, least-squares separations, tectonic trend analysis, spectral analysis, Werner method, Euler method, and 2D techniques. The results show that the main tectonic trends are 35° N–45° W, 45° N–65° E, E–W, and Aqaba.Moreover, two seismic lines, WQ85-31B and 127, were interpreted, and their location was matched with the deduced tectonic map. The results show great matching between the location of the faults deduced from both the geomagnetic and seismic data. They agree completely with the well logging data.Furthermore, these structures are correlated with the earthquake activities recorded by the Egyptian National Seismological Network (ENSN). The correlation implies that the studied area is more stable than other adjacent areas in the northern parts of Egypt close to the Mediterranean Sea and the Nile River Delta.  相似文献   

Salt response of the freshwater microalga Scenedesmus obliquus (Turp.) Kutz is modulated by the algal growth phase     

Taha Mohamed El-Katony  Magda Faiz El-Adl 《中国海洋湖沼学报》2020,38(3):802-815

Growth and biochemical responses of the coenobial green alga Scenedesmus obliquus to salinity stress were monitored across different phases of growth. The alga was cultured on BG11 growth medium and subjected to 0, 30, 100, and 200 mmol/L NaCl for a period of 20 d, during which algal cultures were harvested at 4-d intervals. The salinity-induced inhibition of algal growth was accompanied with prolongation of timing of the different growth phases. The sharp and progressive salinity-induced inhibition of algal growth rate during the early phase of growth points to salt shock but moderation of inhibition at the subsequent stages of growth means algal acclimation to salinity. The concentrations of chlorophylls a and b, soluble sugars, proteins as well as those of K+ and Na+ in the alga exhibited peaks at the initiation of the exponential phase of growth, with increasing magnitude in proportion to the increase in the level of salinity. Nevertheless, whereas soluble sugars of the alga peaked at initiation of the exponential phase, starch concentration progressively increased with culture age, reaching saturation towards the stationary phase. Whereas the salinity-induced increase in soluble sugars was most evident at the early stages of growth the reverse was true for starch. The present results point to fast acclimation of S. obliquus to salt stress post a brief salt shock, utilizing soluble sugars, K+ and Na+ for osmotic adjustment. Increasing salinity from 0 to 200 mmol/L NaCl led to progressive increase in soluble sugars, proteins, K + and Na + concentrations of the algal cells, particularly at the early stages of growth. However, the salinity-induced increase in chlorophyll concentration approached a limit at 100 mmol/L NaCl whereas that in starch concentration was more evident at the later stages of growth.  相似文献   

Recent warming trend in the coastal region of Qatar     

Way?Lee?Cheng  Ayman?Saleem  Reza?SadrEmail author 《Theoretical and Applied Climatology》2017,128(1-2):193-205

The objective of this study was to analyze long-term temperature-related phenomena in the eastern portion of the Middle East, focusing on the coastal region of Qatar. Extreme temperature indices were examined, which were defined by the Expert Team on Climate Change Detection and Indices, for Doha, Qatar; these indices were then compared with those from neighboring countries. The trends were calculated for a 30-year period (1983–2012), using hourly data obtained from the National Climatic Data Center. The results showed spatially consistent warming trends throughout the region. For Doha, 11 of the 12 indices studied showed significant warming trends. In particular, the warming trends were represented by an increase in the number of warm days and nights and a decrease in the number of cool nights and days. The high-temperature extremes during the night have risen at more than twice the rate of their corresponding daytime extremes. The intensity and frequency of hot days have increased, and the minimum temperature indices exhibited a higher rate of warming. The climatic changes in Doha are consistent with the region-wide heat-up in recent decades across the Middle East. However, the rapid economic expansion, increase of population since the 1990s, and urban effects in the region are thought to have intensified the rapidly warming climate pattern observed in Doha since the turn of the century.  相似文献   

Tectonic evolution of an intraplate basin: the Lower Tagus Cenozoic Basin,Portugal          下载免费PDF全文

João Carvalho  Carlos Pinto  Ruben Dias  Taha Rabeh  Luis Torres  José Borges  Ricardo Torres  Henrique Duarte 《Basin Research》2017,29(5):636-657

This article focuses on the reinterpretation of well, seismic reflection, magnetic, gravimetric, surface wave and geological surface data, together with the acquisition of seismic noise data to study the Lower Tagus Cenozoic Basin tectono‐sedimentary evolution. For the first time, the structure of the base of the basin in its distal and intermediate sectors is unravelled, which was previously only known in the areas covered by seismic reflection data (distal and small part of intermediate sectors). A complex geometry was found, with three subbasins delimited by NNE‐SSW faults and separated by WNW‐ESE to NW‐SE oriented horsts. In the area covered by seismic reflection data, four horizons were studied: top of the Upper Miocene, Lower to Middle Miocene top, the top of the Palaeogene and the base of Cenozoic. Seismic data show that the major filling of the basin occurred during Upper Miocene. The fault pattern affecting Neogene and Palaeogene units derived here points to that of a polyphasic basin. In the Palaeogene, the Vila Franca de Xira (VFX) and a NNE‐SSW trending previously unknown structure (ABC fault zone) probably acted as the major strike‐slip fault zones of the releasing bend of a pull‐apart basin, which produced a WNW‐ESE to NW‐SE fault system with transtensional kinematic. During the Neogene, as the stress regime rotated anticlockwise to the present NW‐SE to WNW‐ESE orientation, the VFX and Azambuja fault zones acted as the major transpressive fault zones and Mesozoic rocks overthrusted Miocene sediments. The reactivation of WNW‐ESE to NW‐SE fault systems with a dextral strike‐slip component generated a series of horsts and grabens and the partitioning of the basin into several subbasins. Therefore, we propose a polyphasic model for the area, with the formation of an early pull‐apart basin during the Palaeogene caused by an Iberia–Eurasia plates collision that later evolved into an incipient foreland basin along the Neogene due to a NW‐SE to WNE‐ESE oriented Iberia–Nubia convergence. This convergence is producing uplift in the area since the Quaternary except for the Tagus estuary subbasin around the VFX fault, where subsidence is observed. This may be due to the locking or the development of a larger component of strike‐slip movement of the NNE‐SSW to N‐S thrust fault system with the exception of the VFX fault, which is more favourably oriented to the maximum compressive stress.  相似文献