AMIRKABIR
Year:2005 | Volume:16 | Issue:61-C|Papers Count:15

In this research limestone powder of stone processing factories as pore-forming material in brick was investigated. Brick samples were made with different proportions of brick making clay and limestone powder. Tests for determination of body density, drying and firing Shirinkages, water absorption, compressive strength and thermal conductivity were performed. After obtaining optimum percentage of additive, lightweight bricks and blocks using limestone were produced in pilot plant scale. In addition to mass decreasing due to CO2 removing, calcite prevents firing shirinkage and density increase. Compressive strength increased in relatively low percentages of calcite. Additive caused improvement of insulation properties.  

Subsidence is an undesirable consequence of underground mining in many countries. It can cause environmental damage and harm surface structures in the mine area. There are many methods for prediction of surface subsidence due to mining activities. Prediction of subsidence due to inclined coal seam working is complicated for non-symmetric nature of the subsidence curve trough. In this research, a new two-conditional function is developed to predict non-symmetric curve of subsidence profile above an inclined long wall face. The results are compared to the subsidence profiles obtained from the Lizhuizi coalmine in China. The coefficient of deviations between calculated and measured data is 0.997. This comparison shows that mining subsidence can be predicted with a reasonable degree of accuracy using the proposed new method.    

Hydrogen sulfide (H2S) is generally an undesirable component of natural gas. H2S not only can critically affect the economic proportion of hydrocarbon gas in the reservoir, but also it is highly toxic and corrosive for production equipment. Therefore the ability to predict the occurrence of H2S in undrilled prospects would be a very useful idea in decrease of gas exploration and production risk. A variety of discrete sources for H2S in petroleum have been identified including: 1-Bacterial reduction of sulfate to H2S (BSR) 2-Thermal decomposition of sulfides in kerogen and/or oil.  thermochemical reduction of sulfate to H2S (TSR). In natural gas reservoirs in the south of Iran have been seen the sign of TSR in particular in lower Dalan gas reservoir.Significant enrichment in nitrogen, occurrence of isotopically light CO2 and depletion in the light carbon isotope of methane, ethane and propane in the gas reservoir that buried in more than 4km . These peculiarities suggest that the composition of gases in this zone was modified by the process of the thermochemical reduction of sulfate.    

This paper is devoted to introduce an earthquake intensity scale for evaluation of intensity of earthquakes in Iran. The introduced scale is based on two important points of view, first; damage to buildings and structures which exist in Iran have been taken into the account, second; the scale is compatible to international intensity scales specially to the MSK scale. The utilized criteria are mainly based on; damage to building and structures, disturbing and changes of the earth surface and under ground water, and earthquake effect observations. Buildings and structures were classified into 5 types from (A) very week to (E) very good. Damages were classified as they are in the MSK scale. The introduced scale has 12 degrees. From (I) very weak (not noticeable) to (XII) strongly destructive. Each one of the degrees were defined by clarified criteria.      

In this paper a novel non-parametric approach for designing geodetic networks based on  evolutionary algorithms is proposed. Since conventional analytical optimization methods are based on gradient approaches, they have some drawbacks including approximate parameters requirement and inability to work with discrete objective functions and/or constraints e.g. visibility matter. To prevent from above problems, the standard genetic algorithm method is utilized. Primary tests demonstrate the capability of proposed method to design the optimal network without approximate values and with visibility constraint satisfaction.    

It has been proved that increasing structural strength as the unique parameter in the common design method does not suffice safety or the reduction of structural damages. Different researches showed that the earthquake destructive effects are affected by seismic input energy, received by structure during the ground motion that its prediction is not possible by nonlinear strength response spectra or even displacement response spectra. In this research, some common RC structures have been chosen, and nonlinear time history dynamic analyses of these designed structures have been performed. Based on the results of this procedure and basic structural seismic energy equations, values of different energy parameters in the structures have been calculated and their time history graphs have been drawn. By investigation on these graphs, it is evident that by using energy concepts, the most of effective structural seismic behaviour parameters are justified and applicable in the seismic design procedure.    

Chador- malu mineral processing plant includes three similar and parallel production lines. The nominal production capacity of each line has been designed to be 1,700,000 tons per year. The final products are magnetite, hematite and phosphate concentrates. The magnetite and hematite concentrate productions are 216 and 50 tones per hour for each production line respectively. The hematite concentrate is produced in a flotation circuit including rougher, scavenger and cleaner stages. Sala mechanical flotation cells were employed in all stages. To make a prediction of results of column flotation of hematite, a laboratory test was designed. The laboratory column cell diameter and height were 7.6and 153cm respectively. Bubbles were generaled by using a vertical Internal sparger. A wash water system was employed to clean overflow concentrate. Hydrodynamic parameters of column cell were estimated by water manometers. Effects of parameters such as under flow rate, gas rate, wash water rate and collector-frother dosages on metallurgical and hydrodynamic cell performance were determined. The reasonable cell performance values for under flow rate, gas rate, wash water rate and collector-frother dosage were obtained. which is very close to plant production performance. It is predicted that by employing these results, all nine stages in mechanical flotation cell can be replaced with one column flotation stage.    

Numerous steel moment-resisting connections failed by brittle fracture during the Northridge earthquake. Sideplate connection uses a pair of parallel full-depth side plates to connect the beam to the column. The beam never touches the column. The physical separation between beam and column eliminates the peaked triaxial stress concentration. Fifteen 3D finite element models were developed to represent the nonlinear behavior of sideplate connections. The results indicate that this connection type has sufficient stiffness, strength and ductility to classify it as rigid, full-strength, ductile connection.    

Nanopowders are powders with particle size less than 100 nanometer. The applications of nanopowders are in the production and processing of nanocomposites, microelectronic, industrial cathalists, coating, sintering at low temperature, lubricants, propellants, purification of aqiuos solutions, biomaterials and filtration. In this work, a reactor for production of nanopowder using IGC method was designed and manufactured. By changing the production parameters such as chamber temperature and pressure, evaporation rate, precursor and evaporation time, silver powders were produced. The characteristics of the produced powders were studied using EDX, SEM and TEM techniques. The results showed that powders with particle size between 2-60 nm can be produced. These powders had spherical shape but they were very aggregated. The particle size increases with chamber pressure and temperature.      

In this papers, the punching shear strength of flat plate lightweight concrete slabs, using natural lightweight aggregates, is studied. In the experimental part of the study, six specimens of rectangular lightweight concrete slabs have been manufactured and tested. The strength of concrete and reinforcement varied in different tests. The slab dimensions and the area of reinforcing bars in slabs have been carefully designed so that the slabs failed due to punching shear. In each test, load and displacement were measured using a computer data acquisition system. The behavior of slabs, cracking pattern and the slab stiffness were studied from the test results. The experimental results have been compared with the provisions of different codes. The comparison shows that the BS-8110 Code estimates the punching shear of lightweight slabs most accurately. The slabs made of natural lightweight aggregates can be used in structures by providing good concrete mixture designs.    

In this paper, concrete elevated tanks with Frame Staging, is evaluated to determine the failure mechanism. seismic behavior of. Then (R), a computer model of Frame staging elevated tanks has been built to achieve Response Modification Factor. By using linear and nonlinear time history analysis method for 9 different earthquakes, effect of multi components of earthquake, liquid-structure interaction and P-Δ another nlinear performance has been determined and discussed. At the end, (R) factor for frame staging concrete elevated tanks regarding the seismicity of the site has been recommended.      

This Paper aims at the behavior of the driven piles in soft to moderately stiff clay. Driving the piles in such soils cause the surrounding layers to be disturbed and consequently the pore pressure to be increased. As a result, immediately after driving the effective stress and shear strength of the surrounding soil decreases. Then pore pressure dissipates and results in the consolidation of the soil and increase in the effective stress and shear strength parameters. Such an event also happens in thixotropic clays, which causes the bearing capacity of the driven piles in soft clay to increase with time.    

The objective of this paper is to investigate, in a simplified manner, the process of rock blasting in discontinuous and blocky rock media. The developed code considers the effects of blast geometry (blasthole shape, angle, and location), the physical properties of the intact rock and existing discontinuities, and the blasthole pressure on the processes of rock breakage, fragment throw and muckpile formation. The newly modified DDA code (DDA_BLAST) describes the expansion of the blast chamber as a function of blast chamber volume and time. It is assumed in the code that the media consists of a blocky rock mass which is already fragmented in-situ due to the intersection of pre-existing discontinuities and the passage of stress wave. Hence, the model only considers the gas pressurization phase of the blasting process. Moreover, the proposed model for blasthole expansion assumes an adiabatic expansion of explosion products and variations in explosion pressure upon expansion of blast chamber is calculated from an equation of state. The newly developed DDA_BLAST code was employed to simulate a typical bench blasting problem in jointed rock mass and delve into the mechanisms involved (in a macro scale) in the gas pressurization phase of the blasting process.    

In this paper, the philosophical concept of objectivity in scientific studies and analyses is described. Its meanings in damage analysis and especially "strain localization analyses" are presented. The most important solution for making an analysis objective i.e. using the nonlocal values of relevant variables is discussed. Then the current idea on objective analysis based on secant modulus is represented and the authors' suggestion for objective analysis based on tangent modulus is proposed and finally, a sample problem is solved.