INTERNATIONAL JOURNAL OF INDUSTRIAL ENGINEERING AND PRODUCTION MANAGEMENT (IJIE) (INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE) (PERSIAN)
Year:2008 | Volume:19 | Issue:8-1 (SUPPLEMENT CIVIL ENGINEERING)|Papers Count:9

Development of new techniques and improvements of the existing methods are of concerns of the new generation of civil engineers. One of the most popular types of the floor systems is concrete joist floor system. The traditional method consist the use of piling to limit the deflection of the joists during the construction of floors. Omitting this supports (piles) saves money and time and is a remarkable improvement in the techniques of construction. The aim of the present research is to find the new materials and to perform the structural computations to be able to remove the piles during the construction. Such a system is called "Self-Standing Joist Floor Systems". To achieve the goal of the research, first the formulation and the reason of using the light weight concrete in joists is demonstrated and then 15 concrete beams with 4-m length each was constructed and the load-deflection behavior on each was measured. Finally one floor without piling is constructed and based on codes is loaded. The results of these tests were compared with those of the numerical test performed with ANSYS (V.5.4) software and showed a good agreement. The method was also investigated from an economical point of view. In the present thesis based on complete investigate of the economy of available methods and the computational basis of the proposed methods and the experimental set up and the test conditions, out coming that the proposed self-standing light weight concrete joist floor system has remarkable advantages in compare with the traditional systems.

In this paper a two-dimensional numerical model is developed for simulation of discontinuous density currents. The model is based on unsteady Reynolds-averaged Navier-Stokes equations and uses a buoyancy-modified k - e closure for the turbulence. The governing equations are solved with a finite-volume, fractional step approach. The model is based on a non-iterative direct implicit method. The sigma coordinate system with staggered grid has been deployed. A second order semi-Lagrangian approach has been used for the main advection terms. The model simulation results on discontinuous saline density currents have been compared with the two-dimensional experimental data. It is demonstrated that a two-dimensional model can reliably predict some features of density current. Comparisons with experimental measurement of the evolution of the current, the horizontal velocity components, and the density distributions have shown favorable agreement.

During the current years for the quick scientific and technical transformations and in turn the resulted transformations in social, economic structures and framework of cities as well for the theory of urban stable developments, the importance of urban reconstruction and renovation has been multiplied. Unfortunately the projects for reconstruction and renovation of eroded texture in Tehran city could not satisfy the objectives in reconstruction and renovation. So in this paper we try to identify the sources of risk in reconstruction and renovation projects of Tehran using risk management techniques. To identify the sources of risk in reconstruction and renovation projects of Tehran, in one hand the same project in forerunner countries in addition to the ideas of famous theorists in this field and conclusions made in main international conferences and declarations were studied, and on the other hand the history of renovation and reconstruction in Iran in addition to those renovation and reconstruction projects executed in Iran were studied and through comparison of such studies and interview with relative authorities in the field of urban renovation and reconstruction, the sources of risks in renovation and reconstruction projects in Tehran were identified. Then performing two stages of poling and prioritizing the sources of risk were determined with a high risk. Among such alternatives we may count lack of enough study and identification of the city from various aspects and lack of suitable object identification for such projects.

Application of classic optimization methods in large scale water resources problems usually leads to impractical models with dimensionality and excessive computational time issues. In recent years, heuristic search methods such as Simulated Annealing (SA), Genetic Algorithms (GA) and Ant Colony Optimization (ACO) have been used successfully for solving these kinds of problems.In this paper, a Simulated Annealing algorithm (SA) is adopted for solving the operation problem of Dez Reservoir located in southwestern Iran. The objective junction is assumed to be as minimization of the deficits, both in short (I year) and long term (42 years) periods. Furthermore, the sensitivity of results with respect to changing some of the parameters is studied. Finally, the results of SA with those of GA and ACO, as two other heuristic methods, and DP as a classic method, are compared and discussed. Results indicate that the SA method leads to better solutions with more efficient computational time and effort.

Cost and safety are two most important factors involved in the design of civil engineering systems and structures. Thus, the optimal design of structure dimensions is of big importance in order to reduce the cost of construction while meeting the safety requirement and the design constraints. Up to now several algorithms have been developed and used for optimization of different civil engineering problems. One of these algorithms is the Particle Swarm Optimization (PSO) which is a swarm intelligence based algorithm inspired by the social behavior of animals such as fish schooling and bird flocking to solve continuous problems. In this paper, an optimization model is developed for the optimal design of flood control systems which contain both detention dam and bottom outlet. The proposed model uses the powerful PSO algorithm as the search engine and The "Transport Module" of "SWMM" as the hydraulic analyzer of the system. The applicability of the model to solve real world problem is verified by the optimal design of of South Pars flood control system which contains both detention dam and bottom outlet. The results show that the proposed optimization model can considerably reduce the total costs of flood control systems.

In this paper, the effect of rotation of principal stress axes on anisotropic strength and deformation behaviors of granular soils has been studied by proposing a new bounding surface plasticity model. Due to incorporation of state parameter into the formulation, the model is capable of considering the effect of soil state over wide ranges of densities and void ratios. Location of critical state line is defined between two boundaries which are those under compression and extension modes of triaxial. Finally the model is evaluated compared with the experimental results obtained from hollow cylindrical apparatus.

The idea of the energy dissipation in buckling of thin-walled tubes under axial cyclic loading lead to development of an accordion metallic damper (AMD) as a valid seismic energy absorption damper for installing in chevron braced frames. Of course AMD's have many advantages against available metallic dampers, but need to improve and developing for behavior stability and increasing low cycle fatigue strength. In this paper, for the purpose of improvement and modifying the buckling behavior of AMD's, filled accordion metallic dampers (FAMD) are introduced and It's parameters have been defined, then analytical Finite element model of AMD and FAMD's have been developed and a series of parametric analytical studies have lunched on FAMD's for the determination of the approximate preliminary specifications of different polymers for potential use. After specifying the preliminary material properties, a series of AMD's and FAMD's filled by polyurethane foam were subjected to dynamic tension and compression actuator. Based on the results obtained, using suitable fillers inside AMD's is an efficient method for the purpose of preventing destructive buckling such as diamond mode which in turn improves low cycle fatigue strength of AMD's. Separation between fillers foam and accordion thin-walled tubes because of stress concentration and the generation of contact force is an important parameter of failure in FAMD's, of course this separation occur less for full fill FAMD's.

In the beginning, a matrix formulation for damage detection of static structures by use of elemental stress measurements is suggested. Then, a new approach is proposed to solve the related nonlinear programming utilizing the pseudo-dual simplex technique. Since the mentioned scheme works with the linear model and binary variables, the linearization of the related functions and binary-converting of the variables are explained. Finally, the suggested method is implemented on some plane trusses and its validity is checked.

In recent years, composite materials have been widely used in the engineering structures due to light weight, high strength and corrosion resistance. In this paper, the buckling behavior of laminated composite FRP plates has been studied due to the important role of them as a major part of composite structures. The composite plates have been modeled as symmetric and anti-symmetric angle-ply orthotropic laminated plates as either simple or fixed boundary conditions, to carry out the buckling analysis. ANSYS finite element software has been used for structural analysis to investigate the effective parameters like as aspect ratio, boundary' conditions and fiber orientation of the lamina on the buckling resistance of laminates. Also, the best direction of layers for optimum strength of laminates has been determined. To demonstrate the effect of holes on buckling resistance of laminates, the results of numerical analysis of plates with and without holes for different ratio of hole diameter to the plate width has been compared and the amount of buckling strength reduction has been determined.