INTERNATIONAL JOURNAL OF INDUSTRIAL ENGINEERING AND PRODUCTION MANAGEMENT (IJIE) (INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE) (PERSIAN)
Year:2008 | Volume:19 | Issue:2 |Papers Count:12

It is well known that during strong ground motions most of structural damages and collapses are due to excessive displacement of stories, and other structural and non-structural elements. Therefore one of the most important objectives in seismic design procedure is estimating the maximum inelastic (actual) displacement and drift of structures occurring in severe ground motions. Seismic design provisions estimate the maximum inelastic story drifts and displacements occurring in major earthquakes by amplifying the drifts and displacements computed from elastic analysis at the prescribed design seismic force level using a deflection amplification factor. This parameter is useful for estimating minimum allowable space between two adjacent buildings, controlling story drift limitations and so on. In this research, the deflection amplification factor for both displacement and drift of four steel concentrically braced frames (CBF) and also four steel ordinary moment resisting frames (OMRF) are studied and evaluated. For each system, 2, 4, 6, and 8-story steel building are considered. These frames are subjected to 7 selected records of ground motions having different characteristic such as frequency content, peak ground acceleration (PGA), and so on. It is concluded that the deflection amplification factor for the systems under consideration is considerably higher than that recommended by Standard No.2800 Iran code. From the results of this research, a factor for both deflection and displacement amplification factor of each system under consideration is separately suggested.

Commonly in designing hydroelectric dams and in the level of consulting engineers, for determining the hydroelectric potential of an storage, the analyze is done based on an RBS (Reliability Based Simulation) model with an obvious operation policy.In this paper the effect of optimizing release rules instead of using a fixed and know release policy, like what it is adopted in an RBS model, was explored through developing a dynamic programming (DP) optimization model and Karoon 5 dam was used as a case study. DP evaluates energy potential while maximizing total annual energy generated as its objective function. In the case where no reliability constraint is considered, DP presents such results having lower reliability in meeting energy demands and lower vulnerability index with a slightly improved firm and total annual energy, compared to RBS results. The DP model was then completed as a reliability DP. This reliability model can control the reliability level in meeting energy demands like what it is done in RBS model. Comparison between reliability Dp. And RBS models showed that DP results are better than RBS results in term of firm and total energy generated and installed capacity.However, as the reliability level increases, the out performance of DP over RBS model decreases. This is because by adopting a more strict reliability constraint, the optimization problem will get more and highly constrained and there is little room left in this case for optimizing an objective function.

In this paper, the nonlinear behavior of RC frames strengthened by shear walls and steel bracings is investigated. The use of steel bracing and R C shear wall for strengthening of existing R.C structures usually leads to very complicated system and the study of the behavior of this kind of structures especially their connections, steel bracing area, and frame - shear walls and bracing interaction is necessary. In this study, a ten - story RC. Structure is analyzed using a nonlinear finite element program in four stages.In first stage; RC frame, in second stage; frame with shear walls, in third stage; frame with shear wall and bracing and in fourth stage; frame with bracings is studied. The analytical results show that the application of shear walls causes an increase in strength and stiffness of structure but a decrease in ductility. Compared with shear walls, bracings have less effect on the strength of system but increase the ductility. The modulus of elasticity in strain - hardening part of stress - strain curve of steel has significant effect on the behavior of structure and leads to some numerical problems.

Construction cost of municipal sewer networks as any other infrastructure systems are very demanding. These costs can, however, reduced through optimal design of these networks. A model based on Genetic Algorithm is used in this paper for the optimal design of sewer networks with predefined layout. Three different set of decision variables are used to check the efficiency of the method. Results show that the model is most efficient when pipe sips are used as decision variables of the problem. The efficiency of the proposed method is verified via an analytical example and two benchmark problems from the literature. The results show the ability of the method to produce designs comparable to the results of existing method in the literature with much less computational requirements.

Based on capacity design philosophy, considering the dissipated and non-dissipated parts in structures, the behavior factor is specified in codes. According to the standard Iranian code of practice, the behavior factors for structures with different bracing systems are the same. Whilst each system dissipates energy in different ways. In this research, the nonlinear dynamic behavior of structures with different bracing systems is investigated. For this propose, two dimensional frames with different types of bracing systems are designed Different time history records are applied for nonlinear dynamic analysis of the designed frames.The results indicated that the models are not satisfied the capacity design rules, the columns are failed sooner than the yielding pattern of the bracing elements and the frames cannot achieve the expected ductility. To overcome to these difficulties, the authors proposed the method for design of structures with diagollal bracing systems to increase ductility. All of the models are designed again according to this proposed method and analyzed for the second time.The results represented that the new models have better behavior and achieve more ductility. It is also shown that the behavior factors for these frames are significantly increased.

Through the recent two decades, Tuned Mass Dampers (TMD) has been used as one of passive control methods against seismic forces for tall buildings. In this paper, the impact of TMD on seismic performance of two X-braced and moment resisting frames in different conditions has been studied. The location of TMD in various height levels has been investigated to find its ideal placement. Multi TMDs have been used to suppress seismic vibrations in two lateral directions in order to compare the results with the case with just one TMD. Based on the obtained results, TMD gets basically activated after the first peak of imposed loads or excitations to suppress next peak amounts. Also, peak displacement mitigation depends highly on earthquake records characteristics.

In this research, suitable models for large deformation analysis of concrete arch dams and other similar concrete structures are investigated and by considering arch dam special features and properties, proper model for its large displacement analysis is presented. Major abilities of the prepared computer code in geometric nonlinear analysis of structures is introduced and after its basic verifications a nonlinear analysis of the Morrow Point dam using the Saint-Venant –Kirchhoff model for large displacements is carried out under the case of an intensive ground motion. Foundation is considered as rigid and fluid-structure interaction is approximated by the modified Westergaard added mass concept. It is indicated that considering large deformation effects reduce the displacement response of dam. This reduction is about 8 % in respect to linear dynamic analysis in peak responses. On the other hand, large deformation effects reduce compression stresses and increases tensile ones. Values of these changes are about 9 % for compression and 6% for tension. It seems that for large seismic loads a consistent inclusion of this type of nonlinearity is necessary in order to grasp aproper image of cotlcrete arch dam dynamic real response.

This paper presents an assessment of the seismic hazard for the Markazi province. For approach to this aim based on Seismotectonic conditions, regional earthquake dam and seismicity analyses the active faults and potential seismic sources of the region are identified and illustrated in a seismotectonic map. By using different techniques such as "Time Normalization" a model of earthquake sources has been prepared. The appropriate attenuation laws are selected and earthquake hazard analysis has been done for the province using an analysis point interval scale of 0.1x 0.1 geographical degrees. Iso-acceleration maps have been compiled afterwards for return periods of 50, 100, 200 and 500 years. Finally, a hazard macrozonation map has been compiled and presented.According to the result of this research, Markazi province could be divided into VI zones from earthquake hazard point of view.Earthquake hazard is high in north of Markazi province, medium and low in central and west.

Evaluation of intercity trips may be used for anticipation of trip demands, services' pricing and improvement of the studies for contradiction determination. Usage of trip demand modeling processes, like what existed in the classic method for analyzing urban trip demand, would make the analysis of road trips possible. A substitute method for 4 Steps Models is to use Direct Demand Modeling which is consisted from sub-models of Trip Generation, Trip Distribution, Modal Split simultaneously. The main problem in such model is that they need many numbers of different parameters in order to fulfill all the aforesaid benefits. If the number of alternatives is increased; it would be hard to calibrate the direct demand models and with low number of alternatives, the results form models would lack enough power in anticipation of the future demand.In case we can enter more number of alternatives in model using a scientific method and complete the calibration process successfully, it is possible to remove the problem of direct models for trip demand. So in this paper a new methodology for evaluation of parameters effective on air trips demand to be used in trip demand modeling with the use of Factor Analysis technique.Based on the given methodology herein, at first many alternatives are selected for modeling the trip demand. Then using factor analysis technique a new pattern of alternatives is made and tested. After completing the process for decreasing data structure with the use of factor analysis technique and obtaining the relative results, we would construct a direct model for air trip demand in linear regression method. Comparing the results form models constructed on the base of data from factor analysis methodology in this paper with simple alternatives in linear regression method, satisfactorily results has been obtained. Validating the model based on the given method in this paper indicate a significant success of the method in estimation of air trip demand in Iran compared to common methods of air trip demand modeling.

Over the last decade, evolutionary and meta-heuristic algorithms have been extensively used as search and optimization tools in various problem domains, including science, commerce, and engineering. Ease of use and broad applicability may be considered as the primary reasons for their success. The honey-bee mating process has been considered as a typical swarm-based approach to optimization, in which the search algorithm is inspired by the process of real honey-bee mating. In this paper, the honey-bee mating optimization (HBMO) algorithm is applied to three well-known mathematical problems. To demonstrate the efficiency of the algorithm, these three problems are chosen from well-known constraint and unconstraint mathematical problems with continuous decision and state variables having all the complexities of optimization problems. The proposed HBMO algorithm results in a feasible, near-optimal solution in an acceptable number of mating flights. To emphasize the capability of the developed algorithm in handling these problems, results are compared with those of a well-developed genetic algorithm (GA). Although the HBMO algorithm is at the early stages of development the results obtained by the present algorithm are if not better but surly equally convenient to those employing genetic algorithms. A real-world water resources problem, in the field of water resources management is selected as a case study. The developed model is applied to a reservoir with 60 operational periods with the objective function of minimizing the root mean square error of release and demand. The results show that in this problem the algorithm arrives at the global optimum which is gained by non-linear programming. The results are promising and the algorithm arrives at the global optimum which is gained by nonlinear programming.

Estimating discharge and velocity in natural channels and flood plains for inflexible vegetative cover is important. In such waterways, velocity profile can be divided into three zones: uniform zone which is close to bed with uniform velocity distribution, logarithmic zone which involves the main channel without vegetative cover and the middle zone (transition zone) that is affected by the momentum of upper zone. Existing methods for estimating the discharge and velocity are based on average velocity. In this paper, an analytical model for calculating the velocity profile and transition zone thickness is presented. The results imply desirable correlation between calculated and observed parameters.

In this process after making proper chamber to produce plasma in d.c. Glow regime and readiness of samples and doing microhardness and PIXE analyzes, samples nitriding began in different conditions. The hardness changes and the depth of hardened layer of 321, 316 and 304 steels are studied as a function of discharge parameters [8, 9]. The plasma was produced using a mixture of N2 and H2 gases at glow discharge regime. The gas composition varied between 0.25< [n (H2)]/ [n (N2)]< 0.5, the sample temperature 300°C<T<400°C, And the gas pressure 300mtorr < p <1000 mtorr. Up to 450% increase in hardness was observed in this range of discharge parameters. XRD, GDS, SEM, RBS, PIXE and MICROHARDNESS tests are used for layer analyzing .RBS analyze determined hardened layer thickness up to 1700 A (Max). 20% Nitrogen concentration in nitrided zone and g,a -7 gN phase transformation were observed due to PIXE, GDS, XRD and SEM results.