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Showing 174 results for Design

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.
Mivehchi Mahmood R., M.t. Ahmadi, Hajmomeni A.,
Volume 1, Issue 1 (9-2003)
Abstract

Ambient vibration test is an effective and economical method for identification of dynamic properties of structures such as dams. Mathematical models generally are developed for the design purpose. Structural and material parameter are assumed from similar projects or limited material tests. Therefore it is usually desirable to verify the results obtained from mathematical model by performing vibration test on the actual as-built structure and process its, data correctly. There are addressed in this paper. A modification of mathematical model could then be performed.
Afshar A., Marino M.a., Jalali M.r.,
Volume 1, Issue 1 (9-2003)
Abstract

The reliable operation of spillways, in emergency as well as normal conditions, is one of the vital components in dam safety. Free or uncontrolled overflow spillways are the most reliable choice however. They usually impose higher construction cost and /or results in wasting a considerable amount of water or live capacity of the reservoirs. Employing fuse gates might be a way of reconciling dam safety with maximized storage capacity. The operation of the system can be controlled to within a few centimeters, and the entire installation is not lost for floods less than the maximum design flood. The installation offers more or less the same level of safety as ungated spillways, but avoids their inherent storage capacity loss. Optimum design of fuse gates in particular installation calls for a mathematical model. The model developed in this work includes structural, hydraulics and operational constraints while maximizing the expected cost over the useful life of the project. Accounting for the lost benefit (i.e., water lost as a result of gate tilting) has an influenced effect on the optimum design. To test the performance of the model, data from Zarineh Rud dam in Iran has been used and its result is compared with a direct search technique. The model is capable of helping the design engineer to select the best alternative considering different types of constraints.
Shooshpasha I.,
Volume 1, Issue 2 (12-2003)
Abstract

This study was designed to investigate the local volume changes induced by swelling pressure in unsaturated stand-bentonite bused buffer material. A laboratory mixture of sodium bentonite (lilt/ well graded silica stool in equal proportion by do weight was used for moisture floss experiments in both ambient and elevated temperatures. Experimental results have shown that tit high water content locations within the tested specimens, the density was reduced by .3.57% from its initial values clue to swelling. The swelling pressure was calculated by 4 different models as a function of distance. The calculated results have indicated that the density distribution within the .specimen is affected by swelling potential distribution. The calculated swelling pressure values van as u function of water content, reaching I MPa at the source of water intake, i.e., at high water content :.one, and 2 MPa cot the heater .side, i.e., cot low water content .one.
Saffar Zadeh M., Asadi M.b.,
Volume 2, Issue 2 (6-2004)
Abstract

In this research, the Integrated Noise Model (INM), has been calibrated to perform the noise pollution evaluation in the vicinity of Mehrabad International Airport (MIA). First a conceptual model was developed to analyze the compatibility of airport noise with the land use based on the most widely accepted noise pollution standards. Second, the data generated from the INM package was compared with real data acquired from the test stations positioned around airport. Finally, the outputs of the calibrated model was compared with the noise pollution standards. The results show that more than 70 percent of the land use in the vicinity of airport are not compatible with the accepted noise levels. The generated noise contours was superimposed on the digital map of the city and the areas which violated the permitted levels was recognized. Moreover, the more noise sensitive facilities such as hospitals, schools, and residential units can be positioned in areas which have the permitted noise levels. The model and the procedure can be used to design new airports. Noise evaluation of existing operational airports can be performed by the model developed in this research.
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.
M.m. Alinia,
Volume 2, Issue 4 (12-2004)
Abstract

One main factor in design of panels subjected to axial loading is their buckling behaviour. The design of stiffeners in a metal or composite plated structure is the key factor for safety and weight reduction. This work presents a parametric study on the optimal types and geometrical properties of stiffeners in plates under in-plane axial loads. The results show that flanged type (such as T or L) longitudinal stiffeners increase the normal critical stresses by at least 28% compared to non-flanged stiffener. It is also shown that the optimum geometric properties of stiffeners correspond to the point when the buckling shape of a plate changes from the overall to local mode. Also it is illustrated that for these optimal instances, there always is a linear relationship between the cross-sectional area ratio and the rigidity ratio of the stiffeners to the plates. Finally, Sample relationships for plates having different number of stiffeners are presented.
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.
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. Afshar, M.r. Ghasemi,
Volume 3, Issue 2 (6-2005)
Abstract

An efficient selection operator for use in genetic search of pipe networks optimal design is introduced in this paper. The proposed selection scheme is the superior member of a family of improved selection operators developed in an attempt to more closely simulate the main features of the natural mating process which is not reflected in existing selection schemes. The mating process occurring in the nature exhibits two distinct features. First, there is a competition between phenotypes looking for the fittest possible mate which usually ends up with choosing a mate with more or less the same fitness. Second, and more importantly, the search for a mate is often confined to a community of phenotypes rather than the whole population. Four different selection operators simulating these features in a random and pre-determined manner are developed and tested. All the selection schemes exhibit good convergence characteristics, in particular the one in which both the size of the sub-community and the pair of the mates in the sub-community are determined randomly. The efficiency of the proposed selection operator is shown by applying the method for the optimal design of three well-known benchmark networks, namely two-loop, Hanoi and New-York networks. The proposed scheme produces results comparable to the best results presented in the literature with much less computational effort
A. Afshar, H. Abbasi, M. R. Jalali,
Volume 4, Issue 1 (3-2006)
Abstract

Water conveyance systems (WCSs) are costly infrastructures in terms of materials, construction, maintenance and energy requirements. Much attention has been given to the application of optimization methods to minimize the costs associated with such infrastructures. Historically, traditional optimization techniques have been used, such as linear and non-linear programming. In this paper, application of ant colony optimization (ACO) algorithm in the design of a water supply pipeline system is presented. Ant colony optimization algorithms, which are based on foraging behavior of ants, is successfully applied to optimize this problem. A computer model is developed that can receive pumping stations at any possible or predefined locations and optimize their specifications. As any direct search method, the mothel is highly sensitive to setup parameters, hence fine tuning of the parameters is recommended.
H. Behbahani, S.m. Elahi,
Volume 4, Issue 1 (3-2006)
Abstract

To properly plan for construction, repair, maintenance, and reconstruction of highways the minimum acceptable roadway condition is needed information. This, along with other pavement management tools, will help select the most desirable roadway alternatives. In this research the minimum acceptable conditions are developed based on an opinion survey of non-technical but high-level decision makers. Roadway roughness, expressed as international roughness index (IRI), is used as the measurement criteria. Because IRI is a widely known, acceptable, and a uniformly measurable index, it is used for the purpose of this research. The minimum IRI values developed here will help managers, planners, and engineers in prioritizing their plans and projects. Iran has a central planning system, hence having a minimum acceptable IRI will help in producing homogeneity in decision making. A questionnaire is sent to top level and influential managementlevel officials who have a decisive input in highway matters. The officials are asked to choose the minimum acceptable service level of different types of roadways and classifications. Naturally, roadways with higher levels of importance would require higher service levels. The answers to the survey questionnaires are investigated to determine a preferred minimum acceptable roadway condition. The IRI is computed using a mechanical device enabling a more uniform data collection. The IRI was first proposed by The World Bank as a standard roughness statistic. Extensive research has proven that the IRI can be related to pavement condition. The result of the opinion survey is investigated to determine the minimum levels acceptable for each category. The responses show distinct preference patterns for most of the roadway types. Survey results are investigated by plotting and analyzing them. Based on road user’s perception of roadway condition using guidelines from AASHTO, the Corp of Engineers, and related research work. The appropriate IRI limits and ranges are determined for Iran’s highways. These values are adjusted to obtain final values for Iran. The result, shown in a table, gives upper and lower IRI values accepted and recommended for Iran’s highways. The result of this research work is specifically useful in developing specifications for new pavement design, accepting new pavement from contractors, pavement management, highway planning, and in roadway life cycle cost analysis decision making. The results are subject to refinement over time.
H. Moharrami, S.a. Alavinasab,
Volume 4, Issue 2 (6-2006)
Abstract

In this paper a general procedure for automated minimum weight design of twodimensional steel frames under seismic loading is proposed. The proposal comprises two parts: a) Formulation of automated design of frames under seismic loading and b) introduction of an optimization engine and the improvement made on it for the solution of optimal design. Seismic loading, that depends on dynamic characteristics of structure, is determined using "Equivalent static loading" scheme. The design automation is sought via formulation of the design problem in the form of a standard optimization problem in which the design requirements is treated as optimization constraints. The Optimality Criteria (OC) method has been modified/improved and used for solution of the optimization problem. The improvement in (OC) algorithm relates to simultaneous identification of active set of constraints and calculation of corresponding Lagrange multipliers. The modification has resulted in rapid convergence of the algorithm, which is promising for highly nonlinear optimal design problems. Two examples have been provided to show the procedure of automated design and optimization of seismic-resistant frames and the performance and capability of the proposed algorithm.
Sh. Afandizadeh Zargari, R. Taromi,
Volume 4, Issue 3 (9-2006)
Abstract

Optimization is an important methodology for activities in planning and design. The transportation designers are able to introduce better projects when they can save time and cost of travel for project by optimization methods. Most of the optimization problems in engineering are more complicated than they can be solved by custom optimization methods. The most common and available methods are heuristic methods. In these methods, the answer will be close to the optimum answer but it isn’t the exact one. For achieving more accuracy, more time has been spent. In fact, the accuracy of response will vary based on the time spent. In this research, using the generic algorithms, one of the most effective heuristic algorithms, a method of optimization for urban streets direction will be introduced. Therefore model of decision making in considered one way – two way streets is developed. The efficiency of model in Qazvin network is shown and the results compared whit the current situation as case study. The objective function of the research is to minimize the total travel time for all users, which is one of the most used in urban networks objectives.
M. Khanzadi, G. Ghodrati Amiri, G. Abdollahzadeh Darzi,
Volume 5, Issue 1 (3-2007)
Abstract

According to performance-based seismic design method by using energy concept, in this paper it is tried to investigate the duration and damping effects on elastic input energy due to strong ground motions. Based on reliable Iranian earthquake records in four types of soils, structures were analyzed and equivalent velocity spectra were computed by using input energy. These spectra were normalized with respect to PGA and were drawn for different durations, damping ratios and soil types and then effects of these parameters were investigated on these spectra. Finally it was concluded that in average for different soil types when the duration of ground motions increases, the input energy to structure increases too. Also it was observed that input energy to structures in soft soils is larger than that for stiff soils and with increasing the stiffness of the earthquake record soil type, the input energy decreases. But damping effect on input energy is not very considerable and input energy to structure with damping ratio about 5% has the minimum value.
A. Yeganeh Bakhtiary, A. Ghaheri, R. Valipour,
Volume 5, Issue 1 (3-2007)
Abstract

Determination of allowable free span length plays a crucial role in design of offshore pipelines. The seabed intervention cost and safety of an offshore pipelines project are largely influenced by pipelines free spanning during the project life time. Different criteria are proposed by both the current designing guidelines and researchers there is however lack of comprehensive assessment of independent parameters affects the design length of free span. In this note, it is intended to investigate the effects of seabed formation along with axial force on Natural Frequency of offshore pipelines. Based on this assessment a new simple formula is proposed. Finally, to evaluate the result of this study, the allowable free span length of Qeshem Island pipelines is calculated as a case study and compared with those of the DNV (1998) and ABS (2001) guidelines and the modal analysis.
A.a. Maghsoudi, H. Akbarzadeh Bengar,
Volume 5, Issue 2 (6-2007)
Abstract

Limit to the tension reinforcement ratio ( ρ) in flexural high strength reinforced concrete (HSRC) members is based on the requirement that tension failure as sufficient rotation capacity are ensured at ultimate limit state. However, the provisions for the total amount of longitudinal reinforcement ratio ( ρ and ρ’) are not associated with any rational derivation. In this paper, a quantitative measure to evaluate an upper limit to the compression reinforcement ratio ρBmax of flexural HSRC members is proposed. The quantitative criterion to ρBmax can be derived from i) steel congestion and ii) considerations that are related to the diagonal compression bearing capacity of the members. In this paper it is shown that, when shear loading is dominant, the limit to is set by the diagonal compression criterion. Parameters that affect this limit are deeply investigated and the expressions were derived for different end conditions, to provide an additional tool for a better design and assessment of the flexural capacity of HSRC members.
F. Amini, R. Vahdani,
Volume 5, Issue 3 (9-2007)
Abstract

In this research, an innovative numerical simulating approach for time domain analysis of multi degrees of freedom structures with uncertainty in dynamic properties is presented. A full scale finite element model of multi-story and multi bays of three sample structures has been constructed. The reduced order model of structure with holding the dominant and effective Gramians in the balanced state-space realization has been achieved for easy and safe design of the optimal control forces applied to the structure. Some easy selective control algorithms based on the Optimal-Stochastic control theories such as LQG, DLQRY and modified sliding mode control has been programmed with the simulation control sequences. Some real features of accurate control system such as time delay and noise signals in earthquake time histories and also measurement sensors are considered in illustrative simulation models. These models can be analyzed under either various intensity of corresponding earthquakes or desired random excitations passed through the suitable filters providing stochastic parameters of earthquake disturbances. This control procedure will be shown to be very efficient suppressing all the severities and difficulties may arise in design of a multi-objective optimal control system. The obtained results illustrate the feasibility and applicability of the proposed stochastic optimal control design of active control force providing a stable and energy-saving control strategy for tall building structures.
H. Behbahani, S.a. Sahaf,
Volume 5, Issue 3 (9-2007)
Abstract

The available methods for predicting mechanical characteristics of pavement layers are categorized into two general groups, Destructive and Non-destructive. In destructive method, using coring and pavement subgrade and performing necessary experiments on them, the quantities of layers properties will be identified. In Non-destructive method, the attained deflection is measured by applying the loading on pavement surface using equipments such as FWD which charges the impact dynamic load, and the mechanical characteristics of pavement layers are determined using back calculations. The procedure of conducting these calculations is that by knowing the thickness of the pavement layers and assuming the initial amounts for mechanical characteristics of the layer, the attained deflection at the desired points on the pavement surface will be calculated. Then, new figures are assumed for the characteristics of layers in a reattempt and calculations are repeated again. This trial and error is continued until the produced basin deformations from the calculations with true value, differs in an acceptable range. Using this method may have no accurate and single answer, since the various compositions of layers characteristics can produce similar deformations in different points of pavement surface. In this article, using an innovative method, a measurement is taken in constructing and introducing a mathematical model for determining the elastic module of surface layer using deflections attained from FWD loading equipment. The procedure is such that by using dynamic analysis software of finite elements like ABAQUS and ANSYS, the deformation of corresponding points on the surface of the pavement will be attained by FWD loading equipment. This analysis will be performed on a number of pavements with different thicknesses and different layers properties. The susceptibility analysis of different points deformations show, which will be performed as a result of the change of properties and layers thicknesses. Using this artificial data base as well as deflection basin parameters (DBP), a measurement will be taken toward constructing a regression model for determination of asphalt layer model, i.e. Eac =f(DBP) function shall be attained. To achieve the maximum correlation coefficient, an attempt is made to use the parameters of deformations basin which has the most susceptibility in changing asphalt layer module.

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