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Showing 239 results for Analysis

Behbahani H., Mohammad Elahi S.,
Volume 1, Issue 1 (9-2003)
Abstract

This Paper is the result of a research project on a pavement management system that was performed by the Transportation Division of Iran University of Science and Technology. Information used in the project was gathered from 20 zones of the Tehran Municipality. Any maintenance and repair system for roads has a number of general and coordinated activities in conjunction with programming, designing, construction, Maintenance, Evaluation, and research on road pavement. Prediction of pavement condition is one of the most important parts of, such system. Prediction models have their application at the network level as well as project level activities. At the network level it is used in predicting the condition for budget programming. While in project level it is used in economical analysis. Many factors have been used in determination of pavement condition. These factors are the design life of the pavement, loading, climatic condition, and the type of road. To be able to plan for future improvements we need to predict the future condition of the pavement. In this paper, factors affecting the prediction of pavement condition are discussed. A model is developed exclusively for Tehran based on the distress data collected.
Afshar M.h.,
Volume 1, Issue 1 (9-2003)
Abstract

In this paper the analysis of the pipe networks is formulated as a nonlinear unconstrained optimization problem and solved by a general purpose optimization tool. The formulation is based on the minimization of the total potential energy of the network with respect to the nodal heads. An analogy with the analysis of the skeletal structures is used to derive tire formulation. The proposed formulation owes its significance for use in pipe network optimization algorithms. The ability and versatility of the method to simulate different pipe networks are numerically tested and the accuracy of the results is compared with direct network algorithms.
Afandizadeh Sh.,, Zoghi H. ,
Volume 1, Issue 2 (12-2003)
Abstract

Since Road transportation accounts for a large portion of total displaced passengers of Different types it is the most important mode of passenger services in Iran. The costs considered are depreciation, investment, insurance, tax, fuel, tires, main repairs, unexpected repairs, oil filter break shoe. Lubrication, batteries, commission, wages and other miscellaneous costs. These are classified into two categories of fixed and variable costs that it-ere analyzed. The data used is obtained, from the Iranian passenger transportation co- operatives based on their real costs in Fear 2002 . The methodology of determination rate of return and Passenger Transportation Price are described and these parameters are calculated. In this paper, a price model based on the economic techniques and sensitlvtfx. Analysis is presented for operators and managers. Pricing model of passenger service is prepared by the authors by the name of Development of Pricing Model of passenger Services in Intercity Roads . This research is pointing to Model Sensivity Analysis Dependent on Various Indicators.
Asghari K.,
Volume 1, Issue 2 (12-2003)
Abstract

The solution of shallow-water equation for a two-dimensional .simulation of overland /low for an actual watershed, is presented. The Petorv-Galerkin weighted residual method is used to overcome spurious oscillations inflow depth. For modeling overland flow over complex topography and variable surface, ct pre and postprocessor was developed to utilize the Triangulated Irregular Network (TIN) model and to generate finite element mesh. Close agreement of the model with measured data is obtained. This model can be used to better analyze the influence of varying surface roughness and topography on overland flow characteristics, including distribution of flow depth and velocity (is well as resulting hydrographs. Detailed spatial and temporal output parameters provide a basis fur further study of the patterns of soil erosion and evaluation of runoff natural slopes.
Asghari K.,
Volume 1, Issue 2 (12-2003)
Abstract

The solution of shallow-water equation for a two-dimensional .simulation of overland /low for an actual watershed, is presented. The Petorv-Galerkin weighted residual method is used to overcome spurious oscillations inflow depth. For modeling overland flow over complex topography and variable surface, ct pre and postprocessor was developed to utilize the Triangulated Irregular Network (TIN) model and to generate finite element mesh. Close agreement of the model with measured data is obtained. This model can be used to better analyze the influence of varying surface roughness and topography on overland flow characteristics, including distribution of flow depth and velocity (is well as resulting hydrographs. Detailed spatial and temporal output parameters provide a basis fur further study of the patterns of soil erosion and evaluation of runoff natural slopes.
Mazloom M., Ramezanian Pour A.a.,
Volume 2, Issue 1 (3-2004)
Abstract

This paper presents the long-term deformations of reinforced high-strength concrete columns subjected to constant sustained axial forces. The objective of the study was to investigate the effects of binder systems containing different levels of silica fume on time-dependent behaviour of high-strength concrete columns. The experimental part of the work focused on concrete mixes having a fixed water/binder ratio of 0.35 and a constant total binder content of 500 kg/m3. The percentages of silica fume that replaced cement in this research were: 0%, 6%, 8%, 10% and 15%. The mechanical properties evaluated in the laboratory were: compressive strength secant modulus of elasticity strain due to creep and shrinkage. The theoretical part of the work is about stress redistribution between concrete and steel reinforcement as a result of time-dependent behaviour of concrete. The technique used for including creep in the analysis of reinforced concrete columns was age-adjusted effective modulus method. The results of this research indicate that as the proportion of silica fume increased, the short-term mechanical properties of concrete such as 28-day compressive strength and secant modulus improved. Also the percentages of silica fume replacement did not have a significant influence on total shrinkage however, the autogenous shrinkage of concrete increased as the amount of silica fume increased. Moreover, the basic creep of concrete decreased at higher silica fume replacement levels. Drying creep (total creep - basic creep) was negligible in this investigation. The results of the theoretical part of this researchindicate that as the proportion of silica fume increased, the gradual transfer of load from the concrete to the reinforcement decreased and also the effect of steel bars in lowering the concrete deformation reduced. Moreover, the total strain of concrete columns decreased at higher silicafume replacement levels.
Kheyr Aldin A., Mortezaei A.r.,
Volume 2, Issue 1 (3-2004)
Abstract

Structural walls are used extensively in moderate- and high-rise buildings to resist lateral loads induced by earthquakes. The seismic performance of many buildings is, therefore, closely linked to the behavior of the reinforced concrete walls. The analytical models used in this paper are developed to study the push-over response of T-shaped reinforced concrete walls andinvestigate the influence of the flange walls on laterally loaded walls and nonlinear behavior of shear walls, namely strength, ductility and failure mechanisms. A layered nonlinear finite element method is used to study the behavior of T-shaped and rectangular (barbell) shear walls. This paper introduces a computer program to practically study three-dimensional characteristics of reinforced concrete wall response by utilizing layered modeling. The program is first verified bysimulated and reported experimental response of 3-D reinforced concrete shear walls. Subsequently, a study considering eighteen analytical test specimens of T-shaped and barbell shear walls is carried out. Finally, based on analytical results, a new equation for minimum ratio of shear wall area to floor-plan area is proposed.
Masoud Ghodsian ,
Volume 2, Issue 1 (3-2004)
Abstract

The flow characteristics of triangular weir are studied under free and submerged flow condition. This paper reports the results of an investigation carried out to establish the stage-discharge relationship for sharp and broad crested triangular weir. The stage-discharge relationships are deduced by the application of the theorem of the dimensional analysis and the incomplete self-similarity theory coupled with experimental data.
Kimiaei M., Shayanfar M.a., Hesham Ei Naggar M., Agha Kouchak A.a.,
Volume 2, Issue 2 (6-2004)
Abstract

The seismic response of pile-supported offshore structures is strongly affected by the nonlinear behavior of the supporting piles. Nonlinear response of piles is the most important source of potentially nonlinear dynamic response of offshore platforms due to earthquake excitations. It is often necessary to perform dynamic analysis of offshore platforms that accountsfor soil nonlinearity, discontinuity condition at pile soil interfaces, energy dissipation through soil radiation damping and structural non linear behaviors of piles.In this paper, an attempt is made to develop an inexpensive and practical procedure compatible with readily available structural analysis software for estimating the lateral response of flexible piles embedded in layered soil deposits subjected to seismic loading. In the proposed model a BNWF (Beam on Nonlinear Winkler Foundation) approach is used consisting of simple nonlinear springs, dash pots and contact elements. Gapping and caving-in conditions at the pile-soil interfaces are also considered using special interface elements. This model was incorporated into a Finite Element program (ANSYS), which was used to compute the response of laterally excited piles. A linear approach was used for seismic free field ground motion analysis. The computed responses compared well with the Centrifuge test results.This paper deals with the effects of free field ground motion analysis on seismic non linear behavior of embedded piles. Different parts of a BNWF (Beam on Nonlinear Winkler Foundation) model, together with quantitative and qualitative findings and conclusions for dynamic nonlinear response of offshore piles, are discussed and addressed in detail. The proposed BNWF model (only using the existing features of the available general finite element software) could easily be implemented in a more comprehensive model of nonlinear seismic response analysis of pile supported offshore platforms.
Afandi Zadeh Sh., Zoghi H.,
Volume 2, Issue 2 (6-2004)
Abstract

Since Road transportation accounts for a large portion of total displaced passengers of Different types it is the most important mode of passenger services in Iran.The costs considered are depreciation, investment, insurance, tax, fuel, tires, main repairs, unexpected repairs, oil filter break shoe. Lubrication, batteries, commission, wages and other miscellaneous costs.These are classified into two categories of fixed and variable costs that it-ere analyzed. The data used is obtained, from the Iranian passenger transportation co- operatives based on their real costs in Fear 2002 .The methodology of determination rate of return and Passenger Transportation Price are described and these parameters are calculated. In this paper, a price model based on the economic techniques and sensitlvtfx. Analysis is presented for operators and managers.Pricing model of passenger service is prepared by the authors by the name of Development of Pricing Model of passenger Services in Intercity Roads . This research is pointing to Model Sensivity Analysis Dependent on Various Indicators.
Baziar M.h., Asna Ashari M.,
Volume 2, Issue 3 (9-2004)
Abstract

An experimental study was carried out to evaluate the liquefaction resistance of silty sand utilizing laboratory techniques. In this study, liquefaction potential of silty sand by using cyclic triaxial tests on frozen samples retrieved from calibration chamber and constructed samples by dry pouring method were investigated. Correlation between cone penetration resistance and cyclic strength of undisturbed silty sand samples are also examined using CPT calibration chamber and cyclic triaxial tests. The cone penetration tests were performed on silty sand samples with fine contents ranging from 0% to 50% and overburden stresses in the range of 100-300 kPa. Then the soil sample in calibration chamber, in the same way that soil samples were prepared during CPT sounding, was frozen and undisturbed soil specimen retrieved from frozen soil sample were tested using cyclic triaxial tests. Analysis of results indicates that the quality of frozen samples is affected by fine content and overburden pressures. Also, using data obtained in this research, the relationship between cone tip resistance and cyclic resistance ratio (CRR) for silty sand soils will be presented. These correlations are in relatively good agreement with field case history data. Also increasing confining pressure in silty sand material increases the cone tip resistance and generally, cyclic resistance ratio increases by increasing silt content.
Jalali M.r., Afshar A., Mokhtare A.r.,
Volume 2, Issue 4 (12-2004)
Abstract

It is indispensable to explore simulation techniques that not only represent complexdynamic systems in a realistic way but also allow the involvement of end users in modeldevelopment to increase their confidence in the modeling process. System dynamics as a feedbackbasedand object-oriented simulation approach is presented for reservoir operation modeling. Thequick modeling process, the trust developed in the model due to user contribution, group modelsdevelopment possibility and the effective relations of model results are the most significant strongpoints of this approach. The simple modification of model in response to changes in system andcapability to accomplish sensitivity analysis make this approach more attractive and useful ratherthan traditional reservoir operation models. In this paper system dynamics is applied to simulateoperation of a free reservoir with an Ogee spillway, a reservoir with a gated spillway and finally amulti-reservoir system with simple and gated spillways. The multi-reservoir system on Karun riverin south of Iran is modeled under flood condition as a case study in order to demonstrate thecapabilities of the developed model.
Ghodrati Amiri G., Sedighi S.,
Volume 2, Issue 4 (12-2004)
Abstract

In the past decade design procedure changed to �performance-based design� from�force-based design�, by this mean many researchers focused on nonlinear static analysis (NSA)and the procedure named �PUSHOVER�. Advantages of this method are defining the inelasticbehavior of structure without nonlinear dynamic analysis (NDA) effort and also defining plastichinges formation in critical elements, and the order of formed plastic hinges. In spite of these goodadvantages NSA is limited to short and planar structures and application of that in tall andtorsionaly asymmetric structures may yield unreliable results.In this study reliability of NSA is investigated by performing both nonlinear static and dynamicanalysis on six 2D moment resisting concrete frames. Non linear dynamic analysis has been doneby the suggested method in FEMA356 guideline called �Target Displacement Method�. A groupof 4 different lateral increasing loads were used in pushover analysis and 3 different groundmotions were applied in NDA. Results indicate that same responses can be obtained by performingNSA, but errors will be increased by frames height increment.
Soroush A., Koohi Sh.,
Volume 2, Issue 4 (12-2004)
Abstract

Lateral spreading of liquefied saturated sandy deposits happens during and shortly afterearthquakes. This paper first reviews this phenomenon by means of reviewing and comparingobservations on case histories and experimental works. Based on the results from the review andcomparison, a mechanism for describing lateral spreading will be suggested. The Finn model,adopted in the Computer code FLAC is employed to carry out numerical analyses of lateralspreading of the Wildlife Site, happened during the 1987 Superstition Hills earthquake. First themodel is calibrated by means of numerical analysis of the first centrifuge model test of theVELACS Project. For the Wildlife site, three types of analysis are carried out: a) coupledliquefaction-consolidation analysis using the coefficient of permeability (K1) of the liquefiedlayers, as reported in the literature b) analysis type (a), but with K equal to 0.1K1, and c) a fullyundrained liquefaction analysis. The analyses results, in forms of excess pore water pressures andsurface displacements, indicated that the fully undrained behavior of the liquefied layers betterrepresents the behavior and response of the site during the earthquake.
Khalou A.r., Ghara Chour Lou A.,
Volume 3, Issue 1 (3-2005)
Abstract

This paper presents the results of analytical studies concerning the flexuralstrengthening of reinforced concrete beams by external bonding of high-strength lightweightcarbon fiber reinforced plastic (CFRP) plates to tension face of the beam. Three groups of beamswere tested analytically and compared with existing experimental results. Results of the numericalanalyses showed that, although addition of CFRP plates to the tension face of the beam increasesthe strength, it decreases the beam ductility. Finite element modeling of fifteen different beams in aparametric study indicates that steel area ratio, CFRP thickness, CFRP ultimate strength andelastic modulus considerably influence the level of strengthening and ductility.
M. Naderi,
Volume 3, Issue 1 (3-2005)
Abstract

Having observed the costly failures of different cutoff walls, that had been constructed according to the mix design specified by reputable consultants in Iran, a research programme was conducted to study the effects of constituent materials on the properties of plastic concrete. The main properties, such as compressive strength, biaxial and triaxial strains, permeability, and modulus of elasticity have been investigated using different mixes, obtained from prototype production line plant, situated on site, because it was realized that the site production line and the systems employed have major effects on the properties of plastic concrete. Statistical analysis of the results, revealed the coefficients of influence of main constituent materials of plastic concrete namely cement, bentonite, aggregate and water on its compressive strength and modulus of elasticity. Having realized the cancelling effects of bentonite and aggregates on the measured properties, some equations relating the quantities of cement and water to the compressive strength and modulus of elasticity are introduced. Effects of clay and hydrated lime powder, as fillers were also investigated leading to the proposal of limits for their safe and economic use. Since most of the cutoff walls are buried structures, failure strains under both uniaxial and triaxial tests, with values of cohesion and internal friction, are also presented in this paper.
Sabouri Ghomi S., Kharazi M.h.k., Asghari A., Javidan P.,
Volume 3, Issue 1 (3-2005)
Abstract

Design and construction of efficient and economic Reinforced Concrete (R.C.) Hyperbolic Cooling Towers have driven the engineers toward the design of tall and thin-shell towers which have considerable high slenderness aspect ratio. Consequently, the shell of R.C. Cooling Towers with relative high slenderness aspect ratio is extremely prone to buckling instability due to wind loading. To increase the structural stability or buckling safety factor, one economic approach is to design and construct stiffening rings for the R.C. Hyperbolic Cooling Towers. Despite the research previously performed to determine the effect of stiffening rings on the buckling behavior of the R.C. Hyperbolic Cooling Towers, information resulting in maximum buckling stability is absent considering the optimized utilization of the quantity and dimension as well as the location of this type of stiffeners. In this paper, not only the effect of the stiffening rings on the buckling stability of the R.C. Cooling Tower is studied but also the optimized location,quantity and dimension of the stiffening rings are carried out for a sample RC Cooling Tower. The dimensions of the selected sample cooling tower are in average typical dimensions which are used in the current practice. In this study, finite element (F. E.) analyses has been carried out to define the buckling modes and resistance of this tower due to wind loading for different number of stiffening ring configurations. Based on the conducted buckling analysis, the optimized number, location and dimension of the stiffening rings that maximizes the tower.s buckling stability are defined and the methodology to achieve this information is discussed in this paper.
Sadeghi J.m., Youldashkhan M.,
Volume 3, Issue 1 (3-2005)
Abstract

In this paper, the main factors in the analysis of the railway concrete sleepers areinvestigated and new recommendations are made in order to improve the accuracy of the currentpractices in analysis of the railway track system. First, a comprehensive literature survey isconducted, then, FEM models for a railway track system are developed and used to discuss andevaluate the assumptions commonly used in the analysis of the railway track system. The analysisfactors investigated include stress distribution under a concrete sleeper, rail-seat load, anddynamic coefficient factor. Finally, recommendations and needs for continuation of the researchare presented.
Mahmoud Saffarzadeh, Maghsoud Pooryari,
Volume 3, Issue 2 (6-2005)
Abstract

This paper specifies the relationship among various factors contributing to road accidents including geometrical design characteristics, environmental and traffic specifications, by multiple regression analysis. The main objective of this paper is identification of problems associated with the safety issue of road networks by application of accident prediction models. Data from previous accidents were used to develop the models. Results of this study showed that the rate of road accidents is to a large extent dependent on the rate of traffic volume. Type of road and land-use are other important factors influencing the number and intensity of accidents. The mountainous roads in this respect require special attention regarding their safety factors. The quantitative rate of road safety upgrading has also been specified by adding traffic lanes in road networks.
M.h. Bagheripour, S.m. Marandi,
Volume 3, Issue 2 (6-2005)
Abstract

Arational approach is introduced for numerical modeling of unbounded soil foundations based on coupled dynamic periodic infinite and conventional finite elements (IFE-FE). The model can be applied for analysis of various dynamic problems in geomechanics, especially in Soil Structure Interaction (SSI), where determination of stiffness properties and response of unbounded soil domains are of prime importance. In numerical SSI analysis, there exists important problems a) the discretization of natural soil foundation, especially defining the boundaries to prevent reflecting body waves and avoiding spurious results, b) the definition of the matrices related to the soils impedance functions which are essentially dependant on the excitation frequency, c) the evaluation of free field motion of the natural foundation, especially those of irregular geometry and material diversity. An efficient way and integrated solution to these important problems is found to be the use of periodic infinite elements. The wave equation of motion is derived numerically for discretization of the soil domain. Shape functions and mapping coordinates for dynamic periodic infinite elements are presented in this paper. The accuracy of the IFE is examined for the evaluation of free field motion of a visco-elastic soil foundation. Derivation of impedance function is shown and leads to the determination of dynamic stiffness characteristics of the unbounded soil medium including spring and dashpot coefficients. Application of the approach introduced here is shown by analysis of SSI for a semi-tall building subjected to earthquake loading. Other advantages of the approach are the substantial reduction in degrees of freedom involved in numerical SSI analysis, the computational time and costs without sacrificing the accuracy of the results.

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