Nuclear power utilization as a future alternative energy on icebreakers

Bayraktar M.,Pamik M. 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.2

Diversified fuel types such as methanol, hydrogen, liquefied natural gas, ammonia, biofuels, have been come to fore in consideration of the limitations, regulations, environmental perception and efficient use of resources on maritime sector. NE is described as a substantial alternative energy source on the marine vessels in the sense of de-carbonization and fuel efficiency activities carried out by IMO. Although NPVs have been constructed for the merchant, navy and supply fields over the years, their numbers are few and working ranges are quite limited. NE generation techniques, reactor types, safety and security issues in case of any leakage or radiation pollution are analyzed and comparisons are performed between fossilbased fueled and NP based on icebreakers. The comparison are conducted on the basis of dimensions, resistances and operational competences by the VIKOR. NP icebreakers operated in recent years occupy a notable position in the ranking, although fossil fueled ones are most prevalent. Consequently, refueling period and emissions are the principal benefits of NPVs. Nevertheless, the use of such systems on marine vessels especially for merchant ships may come to the fore when all concerns in terms of safety, security and society are resolved since the slightest mistake can have irreversible consequences.

Damages of minarets during Erciş and Edremit Earthquakes, 2011 in Turkey

Bayraktar, Alemdar,Altunisik, Ahmet Can,Muvafik, Murat Techno-Press 2014 Smart Structures and Systems, An International Jou Vol.14 No.3

This paper illustrates the damages of reinforced concrete and masonry minarets during October 23 (Erci?) and November 9 (Edremit), 2011 Van earthquakes in Turkey. Erci? and Edremit are townships located 90km and 18km from Van city center in Turkey, respectively. Ground accelerations and response spectrums for these earthquakes are given in this paper. A total of 63 reinforced concrete and masonry minarets are heavily damaged or collapsed in the city center and villages nearby after both earthquakes. Because of the fact that there is no Turkish standard and specification directly related to design of minarets, nearly all of the constructions are carried out by workers using only their own technical knowledge. So, all of the non-engineering reinforced concrete and masonry minarets completely collapsed or damaged heavily. From the study, it is seen that the damages are due to several reasons such as site effect, location, and length of the fault, reduction in cross section and formation of the discontinuity, use of plain reinforcement steel, use of concrete with insufficient strength, existence of short lap splices and incorrect end hook angle, larger mass and stiffness concentrations on some region, longitudinal reinforcements discontinuity, cracks at the cylindrical body, and damage of spire and end ornament. In addition to these reasons, the two earthquakes hit the minarets within seventeen days, causing progressive damage. So, the existing design and construction practices should be improved to provide sufficient earthquake performance. Also, it is recommended that there should be a safe distance between the minaret and surrounding structures to reduce the loose of life after earthquake.

Stochastic analysis of fluid-structure interaction systems by Lagrangian approach

Bayraktar, Alemdar,Hancer, Ebru Techno-Press 2005 Structural Engineering and Mechanics, An Int'l Jou Vol.20 No.4

In the present paper it is aimed to perform the stochastic dynamic analysis of fluid and fluidstructure systems by using the Lagrangian approach. For that reason, variable-number-nodes twodimensional isoparametric fluid finite elements are programmed in Fortran language by the authors and incorporated into a general-purpose computer program for stochastic dynamic analysis of structure systems, STOCAL. Formulation of the fluid elements includes the effects of compressible wave propagation and surface sloshing motion. For numerical example a rigid fluid tank and a dam-reservoir interaction system are selected and modeled by finite element method. Results obtained from the modal analysis are compared with the results of the analytical and numerical solutions. The Pacoima Dam record S16E component recorded during the San Fernando Earthquake in 1971 is used as a ground motion. The mean of maximum values of displacements and hydrodynamic pressures are compared with the deterministic analysis results.

Near-fault ground motion effects on the nonlinear response of dam-reservoir-foundation systems

Bayraktar, Alemdar,Altunisik, Ahmet Can,Sevim, Baris,Kartal, Murat Emre,Turker, Temel Techno-Press 2008 Structural Engineering and Mechanics, An Int'l Jou Vol.28 No.4

Ground motions in near source region of large crustal earthquakes are significantly affected by rupture directivity and tectonic fling. These effects are the strongest at longer periods and they can have a significant impact on Engineering Structures. In this paper, it is aimed to determine near-fault ground motion effects on the nonlinear response of dams including dam-reservoir-foundation interaction. Four different types of dam, which are gravity, arch, concrete faced rockfill and clay core rockfill dams, are selected to investigate the near-fault ground motion effects on dam responses. The behavior of reservoir is taken into account by using Lagrangian approach. Strong ground motion records of Duzce (1999), Northridge (1994) and Erzincan (1992) earthquakes are selected for the analyses. Displacements, maximum and minimum principal stresses are determined by using the finite element method. The displacements and principal stresses obtained from the four different dam types subjected to these nearfault strong-ground motions are compared with each other. It is seen from the results that near-fault ground motions have different impacts on the dam types.

Finite element model updating of Kömürhan highway bridge based on experimental measurements

Bayraktar, Alemdar,Altunisik, Ahmet Can,Sevim, Baris,Turker, Temel Techno-Press 2010 Smart Structures and Systems, An International Jou Vol.6 No.4

The updated finite element model of K$\ddot{o}$m$\ddot{u}$rhan Highway Bridge on the Firat River located on the $51^{st}$ km of Elazi$\breve{g}$-Malatya highway is obtained by using analytical and experimental results. The 2D and 3D finite element model of the bridge is created by using SAP2000 structural analyses software, and the dynamic characteristics of the bridge are determined analytically. The experimental measurements are carried out by Operational Modal Analysis Method under traffic induced vibrations and the dynamic characteristics are obtained experimentally. The vibration data are gathered from the both box girder and the deck of the bridge, separately. Due to the expansion joint in the middle of the bridge, special measurement points are selected when experimental test setups constitute. Measurement duration, frequency span and effective mode number are determined by considering similar studies in literature. The Peak Picking method in the frequency domain is used in the modal identification. At the end of the study, analytical and experimental dynamic characteristic are compared with each other and the finite element model of the bridge is updated by changing some uncertain parameters such as material properties and boundary conditions. Maximum differences between the natural frequencies are reduced from 10% to 2%, and a good agreement is found between natural frequencies and mode shapes after model updating.

Experimental analysis of transverse jet using various decomposition techniques

Seyfettin Bayraktar,Tamer Yilmaz 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.5

This experimental study reports on testing of a single circular jet in crossflow (JICF) for three different jet-to-crossflow velocity ratios:R=0.5, 1.0, and 1.5. Velocity measurements were made using a hot-wire anemometer. Experimentally obtained JICF data were processed using Fourier, wavelet, and proper orthogonal decomposition (POD) techniques. Power spectrum obtained by Fourier analysis shows that flow at the center of nozzle has better laminar property than subsequent stations. The principle observation is that when jet exit velocity increases, the energy of the flow decreases. The center of the nozzle jet acts as an obstacle and damps the effect of the crossflow. Wavelet analysis reveals the dominant frequencies of the flow to 45 Hz for R=0.5 and 85-105 Hz for R=1.0. Energy distribution of the flow was also calculated by using the POD technique; results show that lower velocity ratio carries more energy of the flow.

Finite element model updating of Kömürhan highway bridge based on experimental measurements

Alemdar Bayraktar,Ahmet Can Altunisik,Baris Sevim,Temel Türker 국제구조공학회 2010 Smart Structures and Systems, An International Jou Vol.6 No.4

The updated finite element model of Kömürhan Highway Bridge on the Flrat River located on the 51st km of Elazl-Malatya highway is obtained by using analytical and experimental results. The 2D and 3D finite element model of the bridge is created by using SAP2000 structural analyses software, and the dynamic characteristics of the bridge are determined analytically. The experimental measurements are carried out by Operational Modal Analysis Method under traffic induced vibrations and the dynamic characteristics are obtained experimentally. The vibration data are gathered from the both box girder and the deck of the bridge, separately. Due to the expansion joint in the middle of the bridge, special measurement points are selected when experimental test setups constitute. Measurement duration, frequency span and effective mode number are determined by considering similar studies in literature. The Peak Picking method in the frequency domain is used in the modal identification. At the end of the study, analytical and experimental dynamic characteristic are compared with each other and the finite element model of the bridge is updated by changing some uncertain parameters such as material properties and boundary conditions. Maximum differences between the natural frequencies are reduced from 10% to 2%, and a good agreement is found between natural frequencies and mode shapes after model updating.

Near-fault ground motion effects on the nonlinear response of dam-reservoir-foundation systems

Alemdar Bayraktar,Ahmet Can Altuni ik,Baris Sevim,Murat Emre Kartal,Temel Türker 국제구조공학회 2008 Structural Engineering and Mechanics, An Int'l Jou Vol.28 No.4

Ground motions in near source region of large crustal earthquakes are significantly affected by rupture directivity and tectonic fling. These effects are the strongest at longer periods and they can have a significant impact on Engineering Structures. In this paper, it is aimed to determine near-fault ground motion effects on the nonlinear response of dams including dam-reservoir-foundation interaction. Four different types of dam, which are gravity, arch, concrete faced rockfill and clay core rockfill dams, are selected to investigate the near-fault ground motion effects on dam responses. The behavior of reservoir is taken into account by using Lagrangian approach. Strong ground motion records of Duzce (1999), Northridge (1994) and Erzincan (1992) earthquakes are selected for the analyses. Displacements, maximum and minimum principal stresses are determined by using the finite element method. The displacements and principal stresses obtained from the four different dam types subjected to these nearfault strong-ground motions are compared with each other. It is seen from the results that near-fault ground motions have different impacts on the dam types.

Reliability and fatigue life evaluation of railway axles

Meral Bayraktar,Necati Tahrali,Rahmi Guclu 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.3

The axle is one of the most important components of a rail vehicle which transmits the weight of the vehicle to the wheels, meets the vertical and horizontal loads formed during static and dynamic moving, and carries the driving moment and braking moment. The prediction of fatigue failure of axles plays an important role in preventing fatigue fractures. Varying loads on components lead to cumulative failure in the mechanism. In this study, failures in axles of rail vehicles serving the Istanbul Transportation Co. have been investigated. Statistical evaluation of real life values has been performed by taking into account the kilometer and load cycle. Equivalent stresses have been used to derive life equations and diagrams by using one of the cumulative life theories known as the Palmgren-Miner method. Finally,theoretical and practical Wohler diagrams S-N (σ-N: stress-life) have been plotted to reveal error calculation.

A New Approach for the Estimation of Immission Loads Under Steady State Conditions

Hanefi Bayraktar 대한토목학회 2010 KSCE JOURNAL OF CIVIL ENGINEERING Vol.14 No.6

Air quality management takes into consideration emission factors and inventories which are essential for developing emission control strategies for determining applicability of permitting and controlling programs and ascertaining the effects of sources and appropriate mitigation strategies. Emission estimates are also important for the related applications such as climate change etc. Emission inventories are studied by emission factors, which mostly lack association of some parameters, such as regional meteorological conditions, socioeconomic and developmental status and industrialization. This study offers a new approach (estimation of imission load) for the calculation of emission inventories after adding the estimation of many possible inputs and outputs. Foremost, average areal concentrations of pollutants are calculated by applying Percentage Weighting Polygon Method (PWP) to Erzurum urban SO2 imission measurement values. Later, mixing height of the study region in Erzurum, Turkey, is assessed by upper atmosphere observations from March 31st to April 1st 2006. Imission load of SO2 in Erzurum urban centre are calculated by a different paradigm based on multiplying urban centre area, mixing height and areal pollutant SO2 concentration values.