International Journal of Civil Engineering
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International Journal of Civil Engineering - Journal articles for year 2005, Volume 3, Number 3Yektaweb Collection - http://www.yektaweb.comen2005/9/10Numerical Simulation of Flow of Bulk Solids Using CANAsand Constitutive Model
http://ijce.iust.ac.ir/browse.php?a_id=1061&sid=1&slc_lang=en
The CANAsand constitutive law in conjunction with the ID technique is used to study the flow phenomenon in a cohesionless granular medium placed between two parallel, rough vertical walls. It is shown that the development of flow is influenced by the geometry of the case. However the main factor is the void ratio of the medium: i.e. arching will prevent the free flow of the material if its void is close to the compact state. The study is extended to cover the axisymmetric situation.
Here the flow of bulk solids through a circular opening at the base of a cylindrical tank is examined.
Ali NoorzadA CARBONATE SAND PARTICLE CRUSHING UNDER MONOTONIC LOADING
http://ijce.iust.ac.ir/browse.php?a_id=53&sid=1&slc_lang=en
The unique behaviour of carbonate materials under shear loading has stimulated in investigating of their geological and engineering properties.Carbonate soils composed of calcium or other carbonates and most abundant in tropical marine environments are of interest from geotechnical view, especially for offshore engineers engaged with Fossil-based fuel exploitation. This was initiated in the early 1960's, when the first offshore borings in the Persian Gulf identified layers of calcarenite and thick layers of sand containing visible shell fragments.For the purpose of exploiting gas and oil resources in hot and temperate climates (e.g. Persian Gulf) off-shore structures have been placed on carbonate soils. The carbonate sediments are high crushable compared with low crushable sediments such as quartzic soils.To examine the crushability of these problematic sediments a series of monotonic compression, extension and post-cyclic triaxial tests under different densities and confining pressures was carried out to study the crushing behaviour of "Rock" carbonate sand obtained from Cornwall, England.It was shown that crushing coefficient decreases with increasing in maximum principal effective stress ratio for both loose and dense states. It seems that for skeletal carbonate sand maximum and minimum dry densities will be changed during shearing loading. In other words, even though the sample has experienced an increase in density, it may also have experienced a reduction in relative density. SALEH ZADEH H.STRENGTH REDUCTION TECHNIQUE IN STABILITY ANALYSIS OF JOINTED ROCK SLOPES
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Existence of discontinuities causes higher deformability and lower strength in rock masses. Thus joints can change the rock mass behaviour due to the applied loads. For this reason properties and orientation of the joint sets have a great effect on the stability of rock slopes. In this paper, after introducing some numerical methods for evaluating the factor of safety for the stability of slopes, stability of jointed rock slopes in the plane strain condition is investigated with the strength reduction technique this method is modified and applied in the multilaminate framework. First of all, stability of one homogeneous rock slope is investigated and compared with the limit equilibrium method. Then stability of a layered rock slope is analyzed with some modifications in the strength reduction technique. Effects of orientation, tensile strength and dilation of layered joint sets on the factor of safety and location of the sliding block are explained. MAHIN ROOSTA R.DIRECT INDEX CODING FOR DISCRETE SIZING OPTIMIZATION OF STRUCTURES BY GENETIC ALGORITHMS
http://ijce.iust.ac.ir/browse.php?a_id=55&sid=1&slc_lang=en
Genetic Algorithm is known as a generalized method of stochastic search and has been successfully applied to various types of optimization problems. By GA s it is expected to improve the solution at the expense of additional computational effort. One of the key points which controls the accuracy and convergence rate of such a process is the selected method of coding/decoding of the original problem variables and the discrete feasibility space to be searched by GAS. In this paper, a direct index coding (DIC) is developed and utilized for the discrete sizing optimization of structures. The GA operators are specialized and adopted for this kind of encoded chromosomes and are compared to those of traditional GA S. The well-known lO-bar truss example from literature is treated here as a comparison benchmark, and the outstanding computational efficiency and stability of the proposed method is illustrated. The application of the proposed encoding method is not limited to truss structures and can also be directly applied to frame sizing problems. KAVEH A.BEHAVIOR OF LOW TO HIGH-STRENGTH LIGHTWEIGHT CONCRETE UNDER TORSION
http://ijce.iust.ac.ir/browse.php?a_id=56&sid=1&slc_lang=en
Results of an experimental investigation performed to evaluate the effect of various concrete strength levels on behavior of lightweight concrete (LWC) under pure torsion are reported.The principle variable of the testing program was compressive strength of concrete (�'c) which ranged between 6.9 and 81.4 MPa. Ten mixture proportions were utilized for LWC of 1500 to 2050 kg/m3 unit weight. In total, sixty four (thirty two pairs) rectangular specimens with 100x 200 mm cross-section were tested. Ultimate torsion strength of LWC increases as uniaxial compressive strength increases however the increase rate reduces for high levels of concrete strengths. The test results are compared with predictions of elastic and plastic theories for torsion and the ACI Code. The Code underestimates the cracking torque of LWC under pure torsion. A regression equation incorporating test results is higher than the ACI equation prediction by a factor of 1.12. KHALOO R.MODELING FREEWAY TRAFFIC FLOW UNDER OFF-RAMP CONGESTION
http://ijce.iust.ac.ir/browse.php?a_id=57&sid=1&slc_lang=en
This paper studies the effects of queue formation in the bottlenecks at off-ramps on the capacity of the freeways. Six expressway exit-ramps throughout the city of Tehran, Iran were selected and their traffic flows were observed in thirty-minute intervals during which the queue formation and queue elimination occurred. Assuming that in the absence of the queue, the traffic flow is in its normal state, the changes in the volume of through vehicles has been modeled as an average estimator of the change in the expressway capacity.The developed models prove that the changes in freeway capacity are due to queue formation at the off-ramp sections. However, the estimated figures are different from those obtained from the theory of freeway capacity. The conclusion is that lane blockage is only one of many factors that affect the freeway capacity while the queue forms. Since it is not possible to quantify all those factors individually, the resulting models are macroscopic estimates of the phenomenon. NASSIRI H.