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41.
This study examines the performance of integration methods for hybrid simulation of large and complex structural systems in the context of structural collapse due to seismic excitations. The target application is not necessarily for real-time testing, but rather for models that involve large-scale physical sub-structures and highly nonlinear numerical models. Four case studies are presented and discussed. In the first case study, the accuracy of integration schemes including two widely used methods, namely, modified version of the implicit Newmark with fixed-number of iteration (iterative) and the operator-splitting (non-iterative) is examined through pure numerical simulations. The second case study presents the results of 10 hybrid simulations repeated with the two aforementioned integration methods considering various time steps and fixed-number of iterations for the iterative integration method. The physical sub-structure in these tests consists of a single-degree-of-freedom (SDOF) cantilever column with replaceable steel coupons that provides repeatable highlynonlinear behavior including fracture-type strength and stiffness degradations. In case study three, the implicit Newmark with fixed-number of iterations is applied for hybrid simulations of a 1:2 scale steel moment frame that includes a relatively complex nonlinear numerical substructure. Lastly, a more complex numerical substructure is considered by constructing a nonlinear computational model of a moment frame coupled to a hybrid model of a 1:2 scale steel gravity frame. The last two case studies are conducted on the same porotype structure and the selection of time steps and fixed number of iterations are closely examined in pre-test simulations. The generated unbalance forces is used as an index to track the equilibrium error and predict the accuracy and stability of the simulations. 相似文献
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Water Resources - In the comprehensive management of watersheds, the knowledge of the sedimentation process in flood conditions is considered as an important and challenging issue. The aim of this... 相似文献
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Maryam Dehghani Mohammad Javad Valadan Zoej Sassan Saatchi Juliet Biggs Barry Parsons Tim Wright 《Journal of the Indian Society of Remote Sensing》2009,37(1):147-156
A large agricultural area located in 20 km north of the city of Mashhad in the north-east of Iran is subject to land subsidence.
The subsidence rate was achieved in a couple of sparse points by precise leveling between 1995 and 2005, and continuous GPS
measurements obtained from 2005 to 2006. In order to study the temporal behavior of the deformation in high spatial resolution,
the small baseline subset (SBAS) algorithm was used to generate the interferometric SAR time series analysis. Time series
analysis was performed using 19 interferograms calculated from 12 ENVISAT ASAR data spanning between 2003 and 2006. The time
series results exhibited that the area is subsiding continuously without a significant seasonal effect. Mean LOS deformation
velocity map obtained from time series analysis demonstrated a considerable subsidence rate up to 24 (cm/yr). In order to
evaluate the time series analysis results, continuous GPS measurements as a geodetic approach were applied. The comparisons
showed a great agreement between interferometry results and geodetic technique. Moreover, the information of various piezometric
wells distributed in the area corresponding to 1995 to 2005 showed a significant decline in water table up to 20 meters. The
correlation between the piezometric information and the surface deformation at well’s locations showed that the subsidence
occurrence in Mashhad is due to the excess groundwater withdrawal. 相似文献
44.
Maryam Ghazanfari Shabankareh Sedigheh Battaleb-Looie Javad Dravishi Khatooni 《国际地球制图》2013,28(11):1257-1267
Abstract This study investigated the effects of some physicochemical properties of sediments on the accumulation of heavy metals in portions of the Musa creek coasts (Jafari and Petrochemical creeks). Effective properties such as pH, EC, texture, GS, γd, n, CaCO3 and OM were determined. All variables showed a normal distribution and general trends of NW–SE and NE–SW. After detrending the variables, ordinary kriging was used for modelling. The C0/σ2, C0/σ2, and search radius criteria were used to select the best semivariogram. All the variables displayed a spatial structure with different intensities. The IDW method was also used for estimation. The cross-validation showed that the results of both IDW and kriging methods are almost similar. Distribution of the sand particle, GS, n and OM decreases with distance from the waterways, whilst clay–silt deposits. In the center of the studied area, CaCO3 has the highest value and EC has the lowest value. 相似文献
45.
The aim of present study was to improve compost quality as well as to achieve an optimum C/N ratio in compost, reduction in heavy metal content and increased water‐holding capacity of composting piles in arid areas. Four windrow compost piles were prepared by mixing sawdust at various dosages with municipal solid waste (MSW). The sawdust was mixed with MSW at 0% (MSW0), 16% (MSW16), 32% (MSW32), and 70% (MSW70) on dry weight basis. The compost piles were monitored daily by recording the temperature, while, weekly measurement was done on C/N ratio, moisture, pH, and electrical conductivity (EC). The addition of 16% sawdust increased the initial C/N to the optimum level and decreased N loss during the composting process. The MSW16 and MSW32 exhibited better temperature dynamics and their composting period seemed to be shorter than that of MSW0 and MSW70. Moreover, addition of sawdust caused lowering of moisture loss from the composting piles. Sawdust admixtures also produced lowering of pH and EC values and led to lower heavy metal content in final products. The quality of the final compost makes it possible to propose the use of this experimental procedure for building up a novel mass reduction of the initial composted waste mixtures. 相似文献
46.
The propagation of seismic waves through a saturated reservoir compresses the fluid in the pore spaces. During this transition, parts of seismic energy would be attenuated because of intrinsic absorption. Rock physics models make the bridge between the seismic properties and petrophysical reality in the earth. Attenuation is one of the significant seismic attributes used to describe the fluid behaviour in the reservoirs. We examined the core samples using ultrasonic experiments at the reservoir conditions. Given the rock properties of the carbonate reservoir and experiment results, the patchy saturation mechanism was solved for substituted fluid using the theory of modulus frequency. The extracted relationship between the seismic attenuation and water saturation was used in time–frequency analysis. We performed the peak frequency method to estimate the Q factor in the Gabor domain and determined the water saturation based on the computed rock physics model. The results showed how the probable fault in the reservoir has stopped the fluid movement in the reservoir and caused touching the water‐bearing zone through drilling. 相似文献
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Natural Resources Research - Groundwater level forecasting is a paramount necessity for integrated management of a basin. Development of suitable models is an essential step in determining... 相似文献
49.
In a comprehensive geochemical study, the genetic relationships among 14 samples of gas condensates from the Persian Gulf were investigated for the purpose of evaluating the respective source rocks in terms of both age and sedimentary paleoenvironment. Chemometric analysis was used for categorization and determination of a certitude range to determine the genetic type of the condensate families in the studied basin. The samples were collected from Late Permian – Triassic reservoirs (Dalan and Kangan formations) located in 6 gasfields (gas condensate) hosting some of Iran’s most important gas/gas condensate reserves. Obtained by gas chromatography-mass spectrometry (GC-MS), a total of 16 biomarker parameters (10 maturity-related parameters and 6 sedimentary environment-related parameters) were used to evaluate the samples in terms of thermal maturity (and hence their positions in the maturity chart), the sedimentary environment of the source rock and the lithology. Application of Hierarchical Clustering Analysis (HCA) and Principal Component Analysis (PCA) to the collected data led to the categorization of the samples into three main genetic groups, I–III. Groups I and III were found to be located in the east and the west of the Persian Gulf, respectively, while Group II was developed between the two other groups. 相似文献
50.
The Salmas geothermal field is located in NW Iran. Subduction of Neo-Tethys oceanic crust beneath the Iranian microcontinent caused to propagation of the magmatic-Arc. Fractures and faults in the convergent zone have created path-ways for the circulation of geothermal fluid. Fracture concentration in the Salmas geothermal field has been characterized using of the fractal method and creation of a fracture density map that shows the highest concentration in the central part of the study area. The permeability of fractures has been evaluated by analyzing their orientation in respect to the paleostress axes. Also, the fractal analyzing result indicates the maximum fractal dimension (1.96) is around the thermal spring outlet. Paleostress analyzing revealed that in the central part of the study area, σ1 axes orientation is S90°W/10° and the σ2 dip is near to the vertical in this stress field, where strike slip faults can be propagated. In the SE part near the recharge of the thermal springs, the σ3 plunge increases to 70? and σ1 orientation is N15°E/20°, in this local tectonic regime thrust fault developed. Fractures have an important role in the circulation of fluid and the fractal dimension increases near the thermal springs in the Salmas geothermal field. Regarding the paleostress data fracture with N-S direction such as the F1 fault zone (parallel to the σ1 axes), a suitable pathway for deep circulation of geothermal fluid flow has been created. 相似文献