نشریه بین المللی مهندسی صنایع و مدیریت تولید (فارسی)(نشریه بین المللی علوم مهندسی)
سال:1382 | دوره:14 | شماره:2 |تعداد مقالات:35

ALN samples have been produced by reaction bonding process using ALN and aluminum powders as starting materials. Different aluminum nitride and aluminum powders ratios were mixed in ethanol media, dried, isostatically pressed and nitrided in N__2 atmosphere. Results showed that the conversion of Al to ALN depends strongly on the amount of aluminum starting powder and decreased with increasing of aluminum after a maximum at 25 Al wt %. Changing the particle size and morphology of the aluminum starting power leads to change in the conversion ratio and microstructure of RBAN ceramics. Typical scanning electron micrographs of RBAN sample indicating primary and secondary aluminum nitride morphology and pore structure. The oxidation behavior of RBAN samples showed the weight gain depends on the average particle size, morphology and amount of Al in starting mixture and pore structure. Samples have been manufactured with equi-axed morphology of Al starting power have thermal conductivity higher than the samples have been manufactured with flake-like morphology. These differences were directly related to the different microstructure of RBAN samples.

In this paper, the seismic behavior of typical Iranian buildings with ordinary moment-resisting reinforced concrete frames is evaluated. The evaluation results indicated that these structures, which were designed based on 2800 standard (1366 edition) and before, due to ductility and stiffness deficiency, don"t satisfy the new 2800 standard (second edition) requirements. Concrete buildings with ordinary moment resistant frames with four and ten stories are investigated. The effectiveness of two retrofit schemes, ordinary concentric steel braces (CBF) and Added Damping And Stiffness steel plate energy dissipaters (ADAS), examined. The results of investigation indicated that, although CBF retrofit scheme (more traditional one) is efficient in stiffness increase and lateral displacement reduction, but increases the internal forces of some structural elements (specially braced columns and their foundation). Due to limited capacity of these elements, this scheme doesn" t satisfy the retrofit objectives. The ADAS dissipater, in contradiction of CBF system, doesn" t produce significant increases in structural seismic forces. Retrofitted structures with ADAS are able to sustain earthquakes, which are stronger than design earthquake. Nonlinear static pushover analysis conducted using ATC-40 capacity spectrum method.

In this study, the behavior of sliding asymmetric buildings subjected to vertical and horizontal components of earthquake is investigated. The three dimensional building is idealized as a single story and modeled as discrete system with six degrees of freedom at top and base floor level. The sliding and separation under the base is modeled by considering the interface sliding contact elements between the foundation and rigid base mass. So that the superstructure behaves on foundation elastically and sliding contact elements behave inelastically by considering separation and sliding with a suitable yield surface. The effect of vertical component of earthquake on the response ~of sliding asymmetric buildings to the number of strong ground motion is investigated for a series of structural parameters. The results show that the effect of vertical component of strong ground motion on the responses of sliding asymmetric building may be highly considerable and this component of earthquake cannot be neglected in design of such buildings.

Mathematical models for optimization are well developed in the last four decades. One of these models is the Quadratic Assignment Model in which the objective function has a quadratic form with respect to the variables. This model is often employed in combinatorial optimization, and has already been used for facility layout optimization in factories. In this paper the above model is modified in two directions. First of all it is used for facility layout optimization of civil engineering construction sites. Secondly the effect of slopes in roads for transportation is included.

One of the common structural systems in designing tall buildings is wall-frame system, which is highly efficient for buildings not taller than 50 stories. By considering wall and frame static interaction in wall-frame system, cutting the shear wall in an optimum level (based on the least displacement of the top) makes possible extinguishing extra forces in frame members. In this study the behavior of wall-frame structures under the lateral forces due to earthquake was investigated and through studying the optimum point of shear wall curtailment, by considering the dynamic wall and frame interaction. The optimum point of the shear wall curtailment is studied in order to extinguish extra forces in frame members and minimize the top of the structure deflection. This study was done by modeling and analyzing structural models and using equivalent static load of the Iranian 2800 earthquake code, response spectrum of the 2800 code, time histories of Tabas, Naghan , Manjil and El Centro earthquakes.

The wooden columnar structure of the historical building of Ali Qapu in Isfahan is a notable sample of Iranian traditional construction of 350 years ago. In this study, the structural system and load carrying elements of the structure have been identified. Structural analysis of the structure due to applied loads has been performed and structural strength of its members has been examined according to related codes. Based on obtained results, suggestions for repair and-maintenance of the structure have been made. In this paper, the results from study on the wooden columnar structure of the Ali Qapu building are presented.

In order to investigate the effects of aluminum slag powder replacement for cement on compressive strength and durability of concrete, 180 number of 15 cm cube concrete specimens prepared using 0,10, 20, 30 and 40 percent replacement of aluminum slag powder (obtained from Arak aluminum manufacturing factory) for cement. Total cementitious materials content in concrete were 330 kg/m^3. The water to cementitious ratio and maximum size of coarse aggregate in concrete specimens were 0.50 and 19 mm respectively. The compressive strength of concrete specimens were measured at 7, 28 and 56 days. Two different curing conditions applied as follow: 1) Curing in fog room in 25°C and 60% RH. 2) Curing in sulphate solutions in 25°C including: a) 5% magnesium sulphate solution, b) 2.5% magnesium sulphate solution. C) 2.5% magnesium sulphate + 2.5% sodium chloride solution. The experimental results indicate that aluminum slag powder obtained from Arak aluminum manufacturing factory is not suitable as a cement material in concrete and through taking part in undesirable reactions on cement hardening, precludes complete hydration of cement particles. Moreover it was found that the use of slag powder more than 10 percent instead of cement is very detrimental to the concrete.

Several 1 D or 2D models have recently been developed by various researchers for the study of flow in compound channels, both in laboratory flumes and natural rivers. In all of these methods, only one typical geometry of channel under consideration must be assumed. This assumption is valid as long as the total changes in cross section over the period of consideration could be ignored. However, in some natural rivers, this is not so and the discrepancy in bed levels during the period under consideration is too great to ignore due to mobility of the channel boundary arising from flood events. In the present research, the channel crosses section of Minab river. At Brentin Hydrometry Station is considered as compound channel. Over a period of only three years, the channel cross section varied significantly. The variation of water depth has been 1.5 m in comparison with the maximum water depth of nearly 4 to 4.5m. In this case, to evaluate the hydraulic behavior of the channel, it is no logical to consider only one geometry. To overcome this problem in general, a new method called the Envelope Sections Method (ESM) has been developed and is illustrated in this paper. The method have been validate against available river gauging data by simulating the stage-discharge relationships for both ordinary and flood flow conditions using detailed information of Minab river and is compared with the observed data. The new method has wide implications for open channel hydraulics, river engineering and flood management in channels with similar hydraulic behavior of highly variable boundaries as observed in Minab River.

Today as the technology improves and the application of energy and chemicals enhances the organic pollutants increases in surface waters in which wastewaters are discharged into. In order to reduce water-borne diseases, necessary actions should be taken to decrease the pollutants. Common methods of surface water treatment are not sufficient anymore. Therefore complementary methods like using activated carbon, aeration, and oxidation and. reverse osmosis should be used. In this paper the use of Powdered Activated Carbon (PAC), TOC test and Jar test in reducing the concentration of organic carbons in water treatment is investigated. Initial experimental results showed large errors in Total Organic Carbon (TOC) evaluation so Dissolved Organic Carbon (DOC) was measured instead. The results showed that using the PAC in addition to conventional treatment method using Ferric Chloride. Greatly reduces organic pollutants. Adding about 60 mg/lit of PAC may reduce DOC up to 90% in optimum conditions. However, different factors like the quality of surface water. Experimental errors, instrumental errors and tool errors can influence the experimental results.

Providing the citizens with drinking water is one of the most important undertakings of the governments requiring huge amount of investments. Piping and pumping costs constitutes a major part of the water distribution network costs. It is obvious that any reduction in these costs amounts to a considerable savings in particular for large scale projects. A constrained nonlinear programming formulation for the optimal design of pipe networks is presented in this paper enabling optimal sizing of the network pipes and pumping heads if required. Two general purpose optimization codes namely DOT & DOC are used to solve the resulting optimization problem. Different numerical examples are considered and results are compared with other methods to verify the capabilities and versatility of the proposed method. Further researches are underway to improve the proposed method and the early results are encouraging.

In the last several years periodic reports indicated the damages to resident"s homes due to ground movement in the Barikan region, 120 km away from Tehran. The earth movement demonstrated by tension cracks and scarps at the surfaces and cracks in the walls of homes and gardens. Maximum movement of village was occurred during the 1990 S Roodbar and Manjil earthquake, north of Iran. Since the slow and continuous earth movement has been observed in the site, a course of site investigation consisting the monitoring of surface and deep earth movement was considered to study the affecting factors and extent of landslide. In the assigned monitoring program, 15 pillars have been fixed around the surface of village, and during about 8 months at the different intervals of time, movement of each point was controlled with reference to a BM out of the moved part. The preliminanary, investigation showed that the rate of movements is a function of groundwater level, and decreased with lowering the groundwater level. Also the increase in width of tension cracks on the surface ground, and walls through the region measured periodically. Plaster plugs installed between concrete frames in depth of monitoring wells, in which any possible cracks reveal soil movement in depth. In addition to ground movement measurements, using the geotechnical properties of different soil layers, stability analysis of soil mass was performed. Results have shown that village would be stable at static conditions in all relative water level conditions. However, in case of earthquake with the value of horizontal acceleration at the pseudo static analysis equal to 0.14g, analysis indicated total instability of landslide. In this paper the results of conducted researches, as well as possible remedial measures to soil movements with regards to known responsible factors of landslide presented.

The presence of sulfate ion in lime treated soil can disrupt the chemical reactions between lime and clay minerals. The result wills be-the formation of ettringite and thaumasite; highly water expansive minerals that can create large volume expansion and strength decrease by time. In a study presented here, caly specimens, which are treated by various amounts of lime, are compacted in CBR molds and then submerged in sodium sulfate solution for 30 days. Two series of experiments were conducted. In the first series called A, the compacted specimens were immediately immersed in the sulfate solutions with different concentrations. Induced volume changes of these specimens were measured every day for a period of one month. CBR tests were conducted at the end of this period. In the second series (called B), specimens were prepared and tested similarly except that these specimens were first cured in water for one month and, then immersed in sulfate solution for another month. The comparison of results indicates the effectiveness of the curing in diminishing the damaging effects of sulfates on lime-treated soils.

Rutting of the asphalt concrete surface layer is a common distress mode in pavement structures that are constructed in hot climatic regions of Iran. In general, if the strength, thickness and compaction of pavement layers and subgrade are adequate, surface rutting will occur only because of the plastic deformation of the asphalt layer. Thus, it is a mixture design problem. To characterize the rutting potential of asphalt concrete mixtures, the authors designed and constructed a small-accelerated test facility that simulates load repetition and temperature conditions that asphalt concrete mixtures experience in the field. The results show that the rutting resistance of asphalt concrete mixtures to plastic deformation depends upon the mix gradation, grade of bitumen and in-service temperature of the asphalt. Using a larger aggregate size and/or harder grade of bitumen will markedly improve the rutting resistant of the mix. This effect is more pronounced at high mixture temperatures.

In recent decade use of silica fume has been become greater in coastal concrete structures in the persona Gulf, to increase durability of those establishments, In this research the durability of cement passers and concrete cubes with use of 7 and 10 percent of silica fume as a cement replacement have been investigated in three curing conditions (fresh water, coast of sea and simulation bonds) by measuring compressive strengths and capillary absorption. Silica fume specimens under wetting and drying condition showed more strength loss after 180 days compare to samples without silica fume or cured in the fresh water. In addition the greater silica fume amount in specimens cured within tidal zone and under wetting and drying simulation, the more water absorption by capillary. According to the results, good correspondence between simulated condition and real site exposure was obtained.

Dynamic instability of the structures, subjected to the impulsive loading, is a significant phenomenon and the possibility of the dynamic collapse of this type of structures is high. One of the most important structural systems, subjected to the impulsive loading, is the industrial frame. In the present paper, dynamic instability behavior of two-dimensional industrial frames, subjected to the impulsive loading of cranes, has been investigated using (geometric and material) nonlinear dynamic analysis. The results of analyses for the industrial buildings with different spans and boundary conditions have been discussed. Also in the present study, the effects of initial imperfections and damping on the dynamic instability behavior of this type of structures have been investigated. The obtained results from the nonlinear dynamic analyses are in good agreement with the design criteria presented by design codes. Also, some recommendations have been suggested to modify the design of these structures.

In this article formulas for determining the degree of statical indeterminacy for skeletal structures are presented. Hybrid methods are also developed for simple and efficient calculation of the indeterminacy. Examples are included to illustrate the proposed approaches.

In order to investigate the effect of strengthening of reinforced beams using steel and GFRP plates on the flexural strength and ductility, 14 specimens have been designed and tested. The specimen regarding the amount of compressive steel and the condition of strengthening are divided in to t\No Group I and II. All the beams were simply supported and were tested under two-point loading. The amount of imposed load, strain in concrete, strain in the level of tension reinforcement bars and deflection of mid span in different stages of loading have been measured and recorded. According to test results the amount of change in the flexural strength and ductility of beams have been calculated. The effect of shape and type of the performance, the strengthening of beams on the flexural parameters and ductility has been investigated.