In practice, steel frames are analyzed and designed by assuming all beam to column connections as either rigid or simple. In real life, there are no such idealizations as rigid or simple and all connections would actually belong to a group of connections named as semi rigid connections. Various difficulties exist in modeling an accurate non-linear behavior of a steel structure, where one of these challenges is the modeling of semi-rigid behavior of connections. A detailed finite element model would take into account the complex interaction between all surfaces due to contact, friction and bolt pretension besides the material and geometrical nonlinearity effects. All these nonlinearity effects could be simply lumped as a moment-rotation type model at the connection region. Such a methodology is followed in this thesis and the main aim is to study the lumped nonlinear behavior of steel semi-rigid connections on the overall structural responses of steel Special Moment Frames. In this thesis three, nine and fifteen story steel Special Moment Frames are analyzed and designed as rigid frames first, and then the frames are reanalyzed considering non-linear effects due to semi-rigid connections. Changes in the ductility and overstrength reduction factors obtained from pushover curves are compared between the rigid and semi rigid modeling alternatives.

During the reservoir production life reservoir pressure will decline. Also after water breakthrough the fluid column weight will increase as hydrostatic pressure will increase because of increased water and oil mixture density. In this case, reservoir pressure may not be enough to lift up the fluid from bottom to the surface. These reasons decrease or even may cause to stop flowing of fluids from the well. Some techniques must be applied to prevent the production decline. Artificial lift techniques are applied to add energy to the produced fluids. It increases production rate by reducing down-hole pressure and so that by increasing the drawdown. Artificial lift techniques increase production either by pumping the produced fluid from the bottom to the surface or reduce bottom-hole pressure by reducing the fluid column weight as a result of decreased fluid mixture density. Artificial lift is used worldwide in approximately 85% of the wells, thus its impact in overall efficiency and profitability of production operations cannot be overemphasized. The most important problem is how to select optimum artificial lift techniques by taking into consideration the reservoir, well, environmental conditions. Selection of poor technique could cause decrease in efficiency and low profitability. As a result, it will lead to high operating expenses. Several techniques have been developed for selection of optimum artificial lift techniques. Expert Systems (ES) is the most suitable technique used in these selection techniques. Because the use and availability of required parameters is easy. Also in this selection method most of the artificial lift techniques are analyzed rather than other selection techniques. Expert Systems program mainly consist of three modules: (1) Expert Module, (2) Design Module, and (3) Economic Module. By entering required data to the system, program automatically suggests the feasible artificial lift techniques those might be used referring to given data. In this thesis work the artificial lift selection criteria and Expert Systems available in the literature have been studied. A Microsoft Windows based program has been developed to predict suitability of artificial lift methods for a given set of wells and produced fluid parameters. For the selected artificial lift method (i.e. sucker rod pump, ESP, gas lift, hydraulic pump, PCP) the program is able to perform basic calculations for the given data. Different case studies have been performed by running the program with actual data from fields. Well data of Venezuela, Azerbaijan and Iranian oil fields has been used in case studies. The results have been compared with previous studies those have been done on these fields with other selection techniques and current artificial lift techniques are being applied in selected wells. The obtained program results have been overlap with current real field application and previous studies.

Simultaneous solution of the conservation equations for energy and chemical species in conjunction with radiative transfer equation was carried out by coupling a previously developed and tested system model of fluidized bed combustion (FBC) to an existing radiation model. The predictive accuracy of the coupled code was assessed by applying it to 0.3 MWt METU Atmospheric Bubbling Fluidized Bed Combustor (ABFBC) Test Rig burning lignite in its own ash and comparing its predictions with the measured temperatures and concentrations of gaseous species along the combustor and radiative heat fluxes incident on the refractory-lined freeboard walls on two combustion tests, with and without recycle. The predictions of the coupled code were found to be in good agreement with the measurements. For the investigation of the significance of coupling of the radiation model to the system model, temperature predictions of the coupled code were compared with those obtained by the original system model. It was found that the effect of incorporating a radiation model into the system model on the predictions was not significant because the high temperatures of refractory-lined freeboard walls and high surface to volume ratio of the test rig under consideration cause the incident radiative heat fluxes to be dominated by walls rather than the particle laden gas emissions. However, in industrial boilers, freeboard is surrounded by water-cooled membrane walls and boilers have much lower surface to volume ratio. In order to examine the effects of both on radiation in industrial boilers, an investigation was carried out on 16 MWt Stationary Fluidized Bed Boiler (SFBB) by applying radiation model, in isolation from the system model, to the freeboard of the boiler. It was found that in the boiler, incident radiative heat fluxes were dominated by particle laden gas emissions. In brief, the coupled code proposed in this study proves to be a useful tool in qualitatively and quantitatively simulating the processes taking place in an atmospheric fluidized bed boilers.

The soil pile system (SPS) is a wastewater infiltration system used for secondary and tertiary treatment of wastewater. The purpose of this study is to perform a feasibility study to assess the applicability of SPS for treatment and safe disposal of domestic wastewaters, using a simplistic steady-state flow analytical modeling and a numerical transient unsaturated flow and transport modeling approaches. It is also aimed to develop guidelines for the design and operation of field scale SPS using the results of modeling studies. The analytical modeling approach (AMA) was used to assess total coliform and chlorine attenuation efficiency in a SPS with clay loam soil. Analytical modeling results showed that SPS can treat wastewater in terms of total coliform and chlorine. Thus, in the light of findings of analytical modeling study, a pilot scale field study was conducted for the identifying the design and operational characteristics of a field scale system. Numerical modeling approach was used to evaluate the impact on contaminant removal of transient nature of wastewater infiltration and redistribution through clay loam soil pile. The results of numerical and analytical models were compared to assess the effect of flow regime on contaminant removal efficiencies. Results show that there is no significant difference between removal efficiencies achieved by numerical and analytical models. Whereupon, analytical model was used to assess behavior of SPS with different soil types, namely silt loam, loam, and sandy loam soils. Model results indicated that SPS can be effective reducing chlorine and total coliform concentrations of wastewater below discharge standards. Results also indicated that SPS is highly sensitive to soil thickness, infiltration rate, soil bulk density and most importantly decay rate coefficients and the performance of SPS is dependent on the design, construction, operation characteristics and soil-environmental conditions of the system.

Harmony search method based optimum design algorithm is presented for the grillage systems. This numerical optimization technique imitates the musical performance process that takes place when a musician searches for a better state of harmony. For instance, jazz improvisation seeks to find musically pleasing harmony similar to the optimum design process which seeks to find the optimum solution. The design algorithm considers the displacement and strength constraints which are implemented from LRFD-AISC (Load and Resistance Factor Design-American Institute of Steel Construction). It selects the appropriate W (Wide Flange)-sections for the transverse and longitudinal beams of the grillage system among 272 discrete W-section designations given in LRFD-AISC so that the design limitations described in LRFD are satisfied and the weight of the system is confined to be minimal. Number of design examples is considered to demonstrate the efficiency of the algorithm presented.

This thesis investigates analysis and simulation of the backscattering enhancement phenomenon from randomly distributed point scatterers. These point scatterers are randomly distributed within a cube or a sphere and then the backscattering enhancement phenomenon from both cubical and spherical distributions are examined throughout the thesis. The general characteristic differences between cubical and spherical distribution about the scattering phenomenon are observed. T-matrix method is used for analytic investigations of the backscattering enhancement and also a certain number of approximate formulas are obtained. As for Monte Carlo simulation method, it is used for simulated investigations of the backscattering enhancement. Some Monte Carlo simulations are prepared by using MATLAB programming language and verified by showing their confidence intervals. Both analytic and simulated investigations of the backscattering enhancement due to single and double scattering are analyzed / however, only simulated investigation of the backscattering enhancement due to multiple scattering are analyzed because of its computational complexity. The thesis traces differences between single scattering and multiple scattering from randomly distributed point scatterers. Effects of both incident field frequency and point scatterer density on the backscattering enhancement are indicated. The thesis seeks answers to questions such as which conditions cause the backscattering enhancement phenomenon from randomly distributed point scatterers, why we need to consider multiple scattering to examine the backscattering phenomenon and how we can discriminate the backscattering enhancement from the specular enhancement.

When using data for estimating the parameters in a bivariate distribution, the tradition is to assume that data comes from a bivariate normal distribution. If the distribution is not bivariate normal, which often is the case, the maximum likelihood (ML) estimators are intractable and the least square (LS) estimators are inefficient. Here, we consider two independent sets of bivariate data which come from non-normal populations. We consider two distinctive distributions: the marginal and the conditional distributions are both Generalized Logistic, and the marginal and conditional distributions both belong to the Student&rsquo / s t family. We use the method of modified maximum likelihood (MML) to find estimators of various parameters in each distribution. We perform a simulation study to show that our estimators are more efficient and robust than the LS estimators even for small sample sizes. We develop hypothesis testing procedures using the LS and the MML estimators. We show that the latter are more powerful and robust. Moreover, we give a comparison of our tests with another well known robust test due to Tiku and Singh (1982) and show that our test is more powerful. The latter is based on censored normal samples and is quite prominent (Lehmann, 1986). We also use our MML estimators to find a more efficient estimator of Mahalanobis distance. We give real life examples.

In this thesis, two-echelon systems with exogenous and endogenous lead times are studied for the orders placed by the retailer(s) from the supplier. The retailer(s) employ periodic-review base-stock policy, namely (R,S) policy. For the case the demand during review period is i.i.d. and the probability distribution is Normal for each review period, a new method is proposed for exogenous lead time case under stationary policy. The results of the proposed method is then compared with the results of the existing methods in the literature and it is concluded that the proposed method provides service levels sufficiently close to target levels whereas the existing methods do not necessarily provide target levels. We use the simulation to study the endogenous replenishment lead time case. The proposed method is modified when the retailer employs stationary policy and it is seen that the proposed method gives no-stockout probabilities close to target levels. Moreover, the impacts of using adaptive policy on the performance of the retailer are studied for endogenous replenishment lead time case. It is concluded that updating of the order-up-to-level deteriorates the performance of the retailer. Finally, it is questioned whether it is beneficial for a retailer to use adaptive policy in a supply chain with two retailers. Simulation results show that the deterioration in the performance of the retailer handling stationary policy is larger compared to the other retailer handling adaptive policy and the deteriorations get larger in the case of an increase in update frequency or in utilization of the supplier.

The main function of a water distribution system is to supply water in sufficient quantity at appropriate pressure with an acceptable quality and as economically as possible. Water leakage in distribution networks may account from 5% to 50% and even larger of the total water delivered. The amount of leakage in a network is directly related to system service pressure. Therefore, reductions in high service pressures will result in considerable reductions in leakage. A methodology for leakage reduction has been presented in context of a developed computer program, LEAKSOL with two sub-programs. The first code, CODE I, provides solution by using optimization techniques with defined pressure-leakage and pressure-demand relations in order to find optimal flow control valve settings minimizing water leakage. The second one, CODE II, makes hydraulic analysis of the network in order to solve the system and to compute the amount of leakage and the amount of water consumed, by using different combinations of isolation valves generated according to the number of valves given and employing the relationships among pressure, leakage and consumption. Computer program application was performed for different scenarios in a sample network previously used in literature and also in N8-3 pressure zone of Ankara Municipal Water Supply System. Leakage reduction up to 10 % has been achieved in N8-3 pressure zone for eight valves located at the entrances of sub-zones, depending on the defined pressure-leakage relationship.

ABSTRACT NOISE ASSESSMENT OF SHIPYARD WORKERS Can,&Ouml / zg&uuml / n M.Sc.,Department of Engineering Sciences Supervisor : Prof.Dr.G&uuml / lin Birlik May 2008,139 pages Noise is one of the most important health risks in workplaces worldwide and NIOSH identified noise as one of the 10 important occupational problems. In OSHA&#039 / s hearing conservation amendment it is stated that in U.S., more than 5 million workers are exposed to potentially hazardous levels of noise in manufacturing and utilities. In 1981 OSHA estimated that, at least one million workers in industry had undergone occupational hearing loss. Ship building has been one of the most promising and rapidly growing industries in Turkey in the recent years. It comprises many production techniques and activities, requires qualified personnel and compliance with several class institutions making the job interesting for the enthusiastic engineers and workers. However shipyard workers are subject to high levels of noise besides other health risks. The aim of this study is to figure out the effect of noise on shipyard workers. For this purpose 2 factories, namely Factory 1 and Factory 2 in a shipyard were chosen and two methods were adopted. The first method was the subjective evaluation of the workers through questionnaires distributed to them, whereas the second method involved the noise level measurement during their work hours. At all the points in Factory 1 where noise level measurements have been done, higher A-weighted values of noise than the limits stated in the legal regulations were found. In Factory 2, noise levels were all below the action value of 85 dBA .Dose measurements of the workers displayed the extremely variable acoustical conditions that the workers encountered. According to the &ldquo / Noise Regulation&rdquo / of Ministry of Labour and Social Security and &ldquo / The European Noise Directive&rdquo / , the employer seems to be obliged to measure periodically and to assess the level of noise exposure of workers in Factory 1 and take immediately the necessary precautions. Ear plug performance and speech interference conditions were also examined.