Gümüşhane ÜniversitesiGümüşhane ÜniversitesiAçık Erişim Arşivi · RDL Open

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  • MakaleYalnız künye2009
    Frequency optimization of laminated general quadrilateral and trapezoidal thin plates

    Topal, Umut

    This paper deals with frequency optimization of symmetrically laminated angle-ply general quadrilateral and trapezoidal thin plates. The objective function is to maximize the fundamental frequency of the quadrilateral and trapezoidal laminated plates and the fibre orientation is considered as design variable. The mathematical formulation is based on the classical laminated plate theory (CLPT) for the frequency analysis. The modified feasible direction (MFD) method is used as the optimization routine. Therefore, a program based on FORTRAN is used. Finally, the significant effects of aspect ratios, boundary conditions, taper ratios and unsymmetric trapezoidal plates on the optimal results are investigated and the results are compared.

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  • MakaleYalnız künye2009
    Determination of tectonic and crustal structure of the eastern pontide orogenic belt (NE Turkey) using gravity and magnetic data

    Maden, Nafiz; Gelisli, Kenan; Eyuboglu, Yener; Bektas, Osman

    The Eastern Pontide Orogenic Belt is one of the most complex geodynamic settings within the Alpine belt. Subduction polarity, which is responsible for the formation of the Eastern Pontide Magmatic Arc, is still under debate because of limited geological, geophysical and geochemical data. This orogenic belt is mainly divided into three subzones depending on lithological characteristics and facies changes as in Northern, Southern and Axial Zones from North to South. These zones are separated from each other by near-vertical faults that display the block-faulting tectonic style of this belt. In this study, the tectonic and crustal structure of the Eastern Pontides, which as yet have not been prospected by using geophysical data, has been investigated with potential field data. The horizontal gradient map obtained from gravity data shows a number of steep and gentle lineaments. It seems that these lineaments E-W, NE and NW-trending correspond to major structural zones of continental crust. Additionally, The Moho depth and Curie point depth variation maps of the Eastern Pontide Orogenic Belt have been computed with the power spectral method of the radial wavenumber carried out by using the fast Fourier transform method. As a result of this method, we estimated that the depths of the Moho and Curie point varied between 29.0 ± 1.2-47.2 ± 1.9 km and 14.3 ± 0.7-27.9 ± 1.4 km, respectively. Our findings indicate that the Moho depth generally increases from north to south in the region. However, the Curie point depth level within the crust has an undulating surface, not a horizontal one.

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  • MakaleYalnız künye2009
    Effects of nonuniform boundary conditions on the buckling load optimization of laminated composite plates

    Topal, Umut; Uzman, Ümit

    This paper deals with buckling load optimization of symmetrically laminated composite thin plates under the uniaxial and biaxial compressive loads with discontinuities along the boundaries. The objective of the design problem is to maximize the buckling load of the laminated plates and the fibre orientation is taken as design variable. The classical laminate plate theory is used for the mathematical formulations of the laminates. The modified feasible direction method is used as optimization routine. Therefore a program based on FORTRAN is used. Finally, the effect of nonuniform boundary conditions, aspect ratios and load ratios on the optimum results is illustrated.

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  • MakaleYalnız künye2009
    Implementation of different encoding types on structural optimization based on adaptive genetic algorithm

    Bekiroǧlu, Serkan; Dede, Tayfun; Ayvaz, Yusuf

    In this study, the use of new alternatives of encoding types such as quaternary encoding and octal encoding is reviewed along with that of binary and value encodings and how they provide contribution to efficiency and robustness of genetic algorithm is discussed in structural problems. In addition to new alternatives of encoding types, a genetic algorithm with adaptive manner is presented so that an adaptive approach including adaptive mutation and adaptive crossover operators is employed. It is concluded that it is not possible to tell that one of the encoding types is exactly dominant over the others in all aspects such as convergence, finding the optimum solution, and iteration number. However, it is worth to say that to run genetic process with different encoding types should be considered since one of the runs can give more appropriate solution than that of the others.

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  • MakaleAçık Erişim2009
    Crustal thermal properties of the central Pontides (Northern Turkey) deduced from spectral analysis of magnetic data; [Orta pontidlerin (Kuzey Türkiye) kabuksal isıl özelliklerinin manyetik verilerin spektral analizi ile belirlenmesi]

    Maden, Nafiz

    The Pontides can be divided tectonically into three main sectors: Eastern, Central, and Western Pontides. Each of these represents an amalgamated tectonic mosaic consisting of remnants of oceanic, continental, and island arc segments. The Eastern and the Western Pontides meet in the Central Pontides, where they are structurally mixed and form a tectonic knot. The Central Pontides of northern Turkey is one of the best exposed segments of the southern margin of Eurasia adjacent to the Tethys Ocean. The study area also extends to parts of the Sakarya and Ki{dotless}rşehir continents. Magnetic spectral analysis, which has been used to estimate the Curie point depths and heat flow values, is employed to identify the thermal regime of the Central Pontides. The magnetic data of the region are separated into five subregions and the power spectra of each region is achieved by using 2D Fourier transform method to attain the average curie depth. The curie depth values changes across the studied region from 14.8 km in the south to 21.8 km in the north. The obtained results imply a high thermal gradient (39.2 °Ckm-1) and corresponding heat flow values (94.1 mWm-2) in the south of the research area. The northern part of the study area displays a low thermal gradient (26.6 °Ckm-1) and low heat flow value (63.9 mWm-2), corresponding to the Central Pontides consisting of accreted oceanic crustal material. The determined values show the heat flow decrease within the accretionary prism toward the island arc-like Pontides.

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  • MakaleYalnız künye2009
    Evaluation of annual legumes and barley as sole crops and intercrop in spring frost conditions for animal feeding I. Yield and quality

    Yolcu, Halil; Dasci, Mahmut; Tan, Mustafa

    This study evaluated sole grass pea (Lathyrussativush.), sole common vetch (Vicia sativa L.), sole barley (Hordeum vulgare L.), common vetch + barley intercrop, common vetch (I) and barley (I) in terms of yields and quality properties in 2006-2007 at Kelkit Aydin Dogan Vocational Training School Research Station of Gumushane University, Turkey. Intercrop plants were separated as common vetch (called as common vetch I) and barley (called as barley I). Plants were seeded in April of both years in a randomized complete block design with 3 replications. The study plots were 3.0 m long by 1.68 m wide, with 24 cm row spacing. Each plot was fertilized with 20 ton ha-1 organic farmyard manure. The year effects were significant in dry matter yield, crude protein, crude protein yield, acid detergent fiber and neutral detergent fiber. The legumes especially were injured by frost in 2007. Significant differences were found in terms of Dry Matter Yield (DMY), Crude Protein (CP), Crude Protein Yield (CPY), Acid Detergent Fiber (ADF), Neutral Detergent Fiber (NDF), Dry Matter Intake (DMI), Dry Digestible Matter (DDM) and Relative Feed Value (RFV) amongst all the plants. Sole common vetch and sole barley had good properties in DMY, CP and CPY. Sole grass pea, common vetch (I), sole common vetch and intercrops showed good quality properties in ADF and NDF. Sole grass pea especially, sole common vetch and common vetch (I) had good quality properties in DMI, DDM and RFV. Farmers should prefer sole common vetch and sole grass pea cultivation in yield and quality and regulate their seeding times according to days with frost in similiar conditions.

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  • MakaleYalnız künye2009
    Lithostratigraphy, facies, and deposition environment of the lower Jurassic Ammonitico Rosso type sediments (ARTS) in the Gümüşhane area, NE Turkey: Implications for the opening of the northern branch of the Neo-Tethys Ocean

    Kandemir, Raif; Yilmaz, Cemil

    Ammonitico Rosso type sediments (ARTS) form the bottom level of the Şenköy Formation in the Gümüşhane area. The formation accumulated in the rift-related basins triggered by extensional tectonic regimes in the Early Jurassic times. Six different sections were studied in this area in order to interpret the lithostratigraphy, facies, and deposition environments of the ARTS. Two basic lithofacies were distinguished, nodular-marly and nodular-calcareous. These facies provide useful information regarding depositional conditions in the area and environmental energy. These factors were mainly related to the relative sea-level that in turn was controlled by tectonic and eustasy conditions. In addition, seven different types of microfacies were recognized and described as a result of the detailed analysis of the sections. The results of the analysis show that these sediments in the Gümüşhane area were developed in transgressive phases/events. These sediments share characteristics with other peri-Mediterranean regions and sea-level curves, and show a similarity to the major transgressive pulse during the Pliensbachian stage. Deposition of ARTS was controlled by syn-depositional extensional movements, leading to their accumulation on top of tilted blocks, slopes and horsts in an open marine environment. The ARTS were developed during the rifting of the continental margins pointing up the phases of the Tethys opening. Neptunian dykes verifying this opening developed at different levels of the ARTS and were filled with overlying sediments. These results support the hypothesis that the ARTS were formed in tectonically active environments where extensional tectonic movements were continuously improved during the deposition of the ARTS.

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  • MakaleYalnız künye2009
    Thermal buckling load optimization of laminated skew plates

    Topal, U.; Uzman, Ü.

    In this study thermal buckling load optimization of laminated skew plates subjected to uniformly distributed temperature load is investigated. All of the laminates considered are assumed to have fully clamped boundary conditions, though the general boundary conditions may also be studied without any difficulty. The objective function is to maximize the critical temperature capacity of the laminated skew plates and the fibre orientation is considered as design variable. The first-order shear deformation theory is used in the mathematical formulation. Nine-node Lagrangian rectangular plate element is used for the finite element solution of the skew laminates. The temperature field is assumed to be uniform over the plate surface and varies in the thickness direction only. Modified feasible direction method (MFD) is used for the optimization routine. A program based on FORTRAN is used for the optimization problem. Finally, the effect of number of layers, skew angles, aspect ratios, width-to-thickness ratios and antisymmetric lay-up on the optimal designs is investigated and the results are compared.

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  • MakaleAçık Erişim2009
    Compositional variations, zoning types and petrogenetic implications of low-pressure clinopyroxenes in the neogene alkaline volcanic rocks of northeastern Turkey

    Aydin, Faruk; Karsli, Orhan; Sadiklar, M. Burhan

    Clinopyroxene phenocrysts and microphenocrysts in different series of the Neogene alkaline volcanic rocks from the eastern Pontides (NE Turkey) record various stages in the crystallization conditions and evolution history of the alkaline melt as well as its origin. Crystal chemical studies reveal that the clinopyroxenes in each rock series show strong textural and compositional similarities, which all reflect a common petrogenetic affinity. They have relatively high Mg-numbers (0.68-0.95), variable Al2O3 (1.3-9.6 wt%), low TiO2 (<2.7 wt%) and Na2O (<0.9 wt%) contents and low Al[6]/Al[4] ratios (mostly <0.25), suggesting relatively low-pressure crystallization conditions of the magma in the storage region. The pressures calculated for the clinopyroxenes in each series are nearly similar and vary in the range of 2.4-4.6 ± 0.9 kbars, which approximately corresponds to a crystallization depth of 7-14 ± 3 km. The analyses of the compositional trends of the clinopyroxenes indicate the following types of zoning: (i) oscillatory and sectorial zoning related to melt crystallization (i.e. rapid cooling and crystallization), (ii) oscillatory, reverse zoning related to the different crystallization paths under a variable fluid regime, (iii) normal zoning related to the differentiation and fractional crystallization of the magma. Based on the primitive mantle- and chondrite-normalized trace and rare earth element patterns, all clinopyroxenes have high abundances of incompatible elements (i.e. La, Ce) with negative high field strength element anomalies (i.e. Zr, Ti) and low Nb/Y (0.1-0.2), Th/Y (< 0.1) and Rb/Y (< 0.03) ratios, suggesting derivation from a similar source. Obtained textural and mineral chemical data, as well as whole-rock compositions, thus suggest that the clinopyroxenes may have started to crystallize from alkaline basaltic magma derived from a homogeneous lithospheric mantle enriched by an earlier subduction event. After this process, the alkaline magma, from which early clinopyroxenes crystallized, underwent a relatively low-pressure fractional crystallization process. This was in closed magma chambers at different levels of the crust (or within a volcanic conduit system devoid of interaction processes), shown by variations in the different crystallization paths and in the fluid regime of the melt during differentiation and ascent of the magma, in a post-collisional extensional tectonic regime which affected the eastern Pontides during the Neogene.

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  • MakaleYalnız künye2009
    Frequency optimization of laminated folded composite plates

    Topal, U.; Uzman, Ü.

    In this study, frequency optimization of symmetrically laminated folded composite plates is presented. The folded plates are modelled as a composite structure that consists of flat plates. The fundamental frequencies of one- and two-fold folded plates are maximized with respect to fibre orientations. The first-order shear deformation theory (FSDT) is used for vibration analysis of laminated folded plates. The modified feasible direction (MFD) method is used for the optimization routine. Therefore a program based on FORTRAN is used. Finally, the significant effects of length-to-thickness ratios, crank angles, different plate lengths and boundary conditions on the optimum results are demonstrated.

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  • MakaleYalnız künye2009
    Mineralogy, whole-rock and Sr-Nd isotope geochemistry of mafic microgranular enclaves in Cretaceous Dagbasi granitoids, Eastern Pontides, NE Turkey: Evidence of magma mixing, mingling and chemical equilibration

    Kaygusuz, Abdullah; Aydinçakir, Emre

    Rocks of the Late Cretaceous Dagbasi Pluton (88-83 Ma), located in the eastern Pontides, include mafic microgranular enclaves (MMEs) ranging from a few centimetres to metres in size, and from ellipsoidal to ovoid in shape. The MMEs are composed of gabbroic diorite, diorite and tonalite, whereas the felsic host rocks comprise mainly tonalite, granodiorite and monzogranite based on both mineralogical and chemical compositions. MMEs are characterized by a fine-grained, equigranular and hypidiomorphic texture. The common texture of felsic host rocks is equigranular and also reveals some special types of microscopic textures, e.g., oscillatory-zoned plagioclase, poikilitic K-feldspar, small lath-shaped plagioclase in large plagioclase, blade-shaped biotite, acicular apatite, spike zones in plagioclase and spongy-cellular plagioclase textures and rounded plagioclase megacrysts in MMEs. Compositions of plagioclases (An33-An60), hornblendes (Mg#=0.77-1.0) and biotites (Mg#=0.61-0.63) of MMEs are slightly distinct or similar to those of host rocks (An12-57; hbl Mg#=0.63-1.0; Bi Mg#=0.50-0.69), which suggest partial to complete equilibration during mafic-felsic magma interactions. The felsic host rocks have SiO2 between 60 and 76 wt% and display low to slightly medium-K tholeiitic to calc-alkaline and peraluminous to slightly metaluminous characteristics. Chondrite-normalized rare-earth element (REE) patterns are fractionated (Lacn/Lucn=1.5-7.3) with pronounced negative Eu anomalies (Eu/Eu*=0.46-1.1). Initial εNd(i) values vary between -3.1 and 1.6, initial 87Sr/86Sr values between 0.7056 and 0.7067. Compared with the host rocks, the MMEs are characterized by relatively high Mg-number of 22-52, low contents of SiO2 (53-63 wt%), low ASI (0.7-1.1) and low to medium-K tholeiitic to calc-alkaline, metaluminous to peraluminous composition. Chondrite-normalized REE patterns are relatively flat [(La/Yb)cn=1.4-3.9; (Tb/Yb)cn=0.9-1.5] and show small negative Eu anomalies (Eu/Eu*=0.63-1.01). Isotope signatures of these rocks (87Sr/86Sr(i)=0.7054-0.7055; εNd(i)=-1.0 to 1.9) are largely similar to the host rocks. Gabbroic diorite enclaves have relatively low contents of SiO2, ASI; high Mg#, CaO, Al2O3, TiO2, P2O5, Sr and Nb concentrations compared to dioritic and tonalitic enclaves. The geochemical and isotopic similarities between the MMEs and their host rocks indicate that the enclaves are of mixed origin and are most probably formed by the interaction between the lower crust- and mantle-derived magmas. All the geochemical data suggest that a basic magma derived from an enriched subcontinental lithospheric mantle, interacted with a crustal melt that originated from dehydration melting of the mafic lower crust at deep crustal levels. The existence of compositional and textural disequilibrium and the nature of chemical and isotopic variation in these rock types indicate that magma mixing/mingling between an evolved mafic and a granitic magma was involved in their genesis. Microgranular enclaves are thus interpreted to be globules of a more mafic magma probably from an enriched lithospheric mantle source. Al-in-amphibole estimates the pluton emplacement at ca. 0.3-3.8 kbar, and therefore, magma mixing and mingling must have occurred at 3.8 kbar or below this level.

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  • MakaleYalnız künye2008
    Elazığ çevresindeki kayaçların beton agregası olarak kullanılabilirliği

    Gurocak, Zulfu; Alemdag, Selcuk

    Bu çalışmada, Elazığ çevresinde yüzeyleyen kayaçların beton agregası olarak kullanılabilirliğinin belirlenmesi amaçlanmıştır. Bu amaç doğrultusunda, Keban Uetamorfitleri, Elazığ Magmatitleri, Harami Formasyonu, Maden Karmaşığı, Kırkgeçit Formasyonu ve Karabakır Formasyonu' ndan farklı noktalardan kaya örnekleri alınmış, kaya ve agrega örneklerinde deneysel çalışmalar yapılmıştır. Petrografik ve kimyasal özellikleri belirlemek için, kimyasal analizler ve ince kesitlerde petrografik çalışmalar yapılmıştır. Ayrıca, kaya örneklerinin birim hacim ağırlık, ağırlıkça ve hacimce su emme, porozite, doluluk oranı, serbest basınç dayanımı belirlenmiştir. Çeneli kırıcı yardımıyla standart boyutta agrega örnekleri hazırlanmış, bu agregaların alkali agrega reaktivitesi, magnezyum sülfat çözeltisinde don kaybı, özgül ağırlık, su emme, yıkanabilir madde içeriği ve Los Angeles aşınma dayanımı belirlenmiştir. Deney sonuçları TSE standartlarındaki sınır değerler ile karşılaştırılmıştır. Keban Metamorfitleri, Elazığ Magmatitleri ve Kırkgeçit Formasyonu' nun düşük Los Angeles aşınma direncine ve özgül ağırlığa sahip olması nedeniyle, bu kayaçların beton agregası olarak kullanılması uygun değildir. Maden Karmaşığı ve Karabakır Formasyonu'na ait bazaltların tüm fiziko-mekanik özellikleri beton agregası olarak kullanılabilme açısından uygundur ve bu kay açlar beton agregası olarak kullanılabilirler.

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  • MakaleYalnız künye2008
    Atatürk Üniversitesi Ziraat Fakültesi Çiftliğinde yetiştirilen siyah alaca sığırlarda akrabalı yetiştirme düzeyi ile bunun bazı üreme ve süt verim özellikleri üzerine etkileri

    Bilgin, Ömer C.; Yanar, Mete; Tüzemen, Naci; Güler, Olcay; Aydin, Recep; Akbulut, Omer; Bayram, Bahri

    Bu çalışmada, Atatürk Üniversitesi Ziraat Fakültesi Çiftliğinde 1989-2002 yılları arasında yetiştirilen Siyah Alaca sığırlarda akrabalı yetiştirme katsayıları hesaplanmış ve yıllar itibarıyla akrabalı yetiştirme düzeyindeki değişimler incelenmiştir. Ayrıca akrabalı yetiştirme düzeyinin doğum ağırlığı ve ilkine buzağılama yaşı gibi üreme özellikleri ve süt verim özellikleri üzerine etkileri de araştırılmıştır. İncelenen dönemde, doğan Siyah Alaca sığırların ortalama akrabalı yetiştirme katsayısı % 1.35 ± 0.45 olarak saptanmıştır. Yıllara göre akrabalı yetiştirme düzeyi dalgalanmalar göstermiştir. 1995 hariç, 1989–1996 yılları arasında akrabalı yetiştirme söz konusu değildir. Son yıllarda ise, akrabalı yetiştirme katsayısında bir artış saptanmıştır. Akrabalı yetiştirme düzeyinin doğum ağırlığını önemli (P<0.01) seviyede etkilediği saptanmıştır. Akrabalı yetiştirme katsayısındaki her % 1’lik artışa karşılık, doğum ağırlığında 0.264 ± 0.006 kg’lık azalma olmuştur. Akrabalı yetiştirilen Siyah Alaca sığırların ilk laktasyon 305 gün süt (P<0.01), günlük süt (P<0.01) ve laktasyon yağ verimi (P<0.05), akrabalı yetiştirilmeyenlere göre önemli derecede düşük belirlenmiştir. Bununla birlikte, ilkine buzağılama yaşı, % süt yağı oranı ve laktasyon süresi gibi diğer özellikler akrabalı yetiştirmeden etkilenmemiştir.

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  • MakaleYalnız künye2008
    The use of cation packing index for characterizing the weathering degree of granitic rocks

    Ceryan, S.; Zorlu, K.; Gokceoglu, C.; Temel, A.

    The weathering state and weatherability of rocks are highly important for engineering geology projects and the use of rocks as building stones. The weathering state of rocks can be described by various chemical and petrographical weathering indices. To determine weathering state of a rock, considerable amount of chemical analyses is required. Weatherability of rocks depends on not only their mineral composition but also the number of cation replaceable with hydrogen in a mineral. In this study, the use of the k-value (cation packing index is defined as the number of cation in a mole) for characterizing the degree of weathering of granitic rocks is investigated. For the purpose of the study, the Kurtun granitic rocks are selected as the material of the study. The study contains three main stages and these are field investigations, laboratory studies and regression analyses. During the field studies, in-situ weathering descriptions and sampling are carried out. The samples are subjected to chemical and petrographic analyses and physical and mechanical tests. At the final stage of the study, a series of regression analyses between the cation packing index and other properties of the samples are performed. The results show that the k-value can be used as a weathering indicator. When compared with the other chemical weathering indices, the k-value can be used as a weathering index without chemical analyses, because it can be determined by mineralogical analyses. (C) 2008 Elsevier B.V. All rights reserved.

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  • MakaleYalnız künye2008
    Investigation of seismic behavior of fluid-rectangular tank-soil/foundation systems in frequency domain

    Livaoglu, R.

    Main purpose of this study is to evaluate the dynamic behavior of fluid-rectangular tank-soil/foundation system with a simple and fast seismic analysis procedure. In this procedure, interaction effects are presented by Housner's two mass approximations for fluid and the cone model for soil/foundation system. This approach can determine; displacement at the height of the impulsive mass, the sloshing displacement and base forces for the soil/foundation system conditions including embedment and incompressible soil cases. Models and equations for proposed method were briefly explained for different tank-soil/foundation system combinations. By means of changing soil/foundation conditions, some comparisons are made on base forces and sloshing responses for the cases of embedment and no embedment. The results showed that the displacements and base shear forces generally decreased, with decreasing soil stiffness. However, embedment, wall flexibility, and soil-structure interaction (SSI) did not considerably affect the sloshing displacement.

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  • MakaleYalnız künye2008
    Mineralogy, mineral chemistry, and fluid inclusion investigation of Köstere hydrothermal vein-type deposit (Gümüşhane, NE-Turkey)

    Demir, Yilmaz; Uysal, Ibrahim; Sadiklar, M. Burhan; Sipahi, Ferkan

    Vein type Köstere ores were deposited along cracks formed as a result of NE-SW fault system in the late Cretaceous felsic volcanic rocks in the northeastern Black Sea Region of Turkey. Total silver content of the Köstere ore is controlled by total silver content of the hydrothermal solution, homogenization temperature of the ore minerals and modal abundances of the tetrahedrite-tennantite serie minerals. The Zn/Cd ratios of sphalerites from the Köstere deposit are close to those of granite-related classical vein-type hydrothermal deposits. Furthermore Co/Ni ratio in pyrite separates, higher than unit, suggests an acidic source for the ore forming fluids. Homogenization temperatures of 200-370 °C and salinity of 0-9.85 eq. wt% NaCl were obtained on the basis of fluid inclusions studies measured in quartz minerals. These data indicate that ore formation conditions for the Köstere ore are similar with the vein-type epithermal-mesothermal deposits, related to the magmatic fluids. The overall low salinities of fluids (on average: 5.4 eq. wt% NaCl) suggest that meteoric waters were involved in mineralization. The possibility of interactions between ascending hydrothermal fluids and dilute meteoric waters is supported by geological features and mineralogical data which indicate a shallow depth of mineralization. Torul Pluton, which is the younger acidic unit (72 my) in the area, is suggested to be related to the formation of Köstere deposit.

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  • MakaleYalnız künye2008
    Investigation of dynamic response of masonry minaret structures

    Dogangun, Adem; Acar, Ramazan; Sezen, Halil; Livaoglu, Ramazan

    Almost all historical minarets in Turkey were constructed using cut stone, masonry blocks or combination of these two materials. The structural and geometrical properties of each masonry minaret, or slender tower structure, depend on many factors including the structural knowledge and applications at the time of construction, experience of the architect or engineer, seismicity of the region, and availability of construction materials in that area. Recent earthquakes in Turkey have shown that most masonry minarets in high seismic regions are vulnerable to structural damage and collapse. In this study, in order to investigate the dynamic behavior of historical unreinforced masonry minarets, three representative minarets with 20, 25, and 30 m height were modeled and analyzed using two ground motions recorded during the 1999 Kocaeli and Duzce, Turkey earthquakes. The modal analyses of the models have shown that the structural periods and the overall structural response are influenced by the minaret height and spectral characteristics of the input motion. The dynamic displacement and axial stress time histories are computed at the critical points on the minarets. During recent earthquakes, most minaret failures occurred above the base of the structure. Consistent with the observed response, the largest stresses were calculated at the same location.

    • SDG 11 · Sürdürülebilir Şehirler ve Topluluklar
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  • MakaleYalnız künye2008
    The rift-related Late Cretaceous drowning of the Gümüşhane carbonate platform (NE Turkey)

    Yilmaz, Cemil; Carannante, Gabriele; Kandemir, Raif

    In the Gümüşhane region (NE Turkey), carbonate platform and basin deposits, crop out with excellent exposures. In this area, two localities (Mescitli-İkisu region, 10 km west of the Gümüş hane and Kale-Kilop region, 20 km southeast of the Gümüşhane), in which the related successions are particularly well exposed, have been studied in detail. The outcropping shallow water limestones of the Berdiga Formation (Eastern Pontides Carbonate Platform) were deposited during Late Jurassic-Cenomanian p.p. times in peritidal environments. The overlying Kermutdere Formation consists of monogenic breccias, calciturbidites, red pelagic limestone and siliciclastic turbidites, which were deposited in slope and basin environments. In the Gümüşhane region, the above Formations record the evolution from platform to basin settings in relation to an extensional regime set up in the Cenomanian. The tectonics-related drowning of the Eastern Pontides carbonate platform resulted in graben-semi graben basins in which deep marine sediments were deposited during Late Cretaceous times, having a wedge geometry.

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  • MakaleYalnız künye2008
    Petrogenesis of the Neogene alkaline volcanics with implications for post-collisional lithospheric thinning of the Eastern Pontides, NE Turkey

    Aydin, Faruk; Karsli, Orhan; Chen, Bin

    Whole-rock geochemistry, Sr-Nd-Pb isotopes and K-Ar data are reported for alkaline samples collected from the Neogene alkaline volcanics (NAVs) in the Eastern Pontides, northeastern Turkey, in order to investigate their source and petrogenesis and geodynamic evaluation of the region. The NAVs were made of three groups that comprise of basanite-tephrite (feldspar-free; Group A), tephrite-tephriphonolite (feldspar and feldspathoid-bearing; Group B) and alkaline basalt-rhyolite (feldspathoid-free; Group C) series. These rocks cover a broad compositional range from silica-undersaturated to silica-oversaturated types, almost all of which are potassic in character. They show enrichment of LREE and LILE and depletion of HFSE, without a Eu anomaly in most of the mafic samples. Textural features and calculated pressures based on the Cpx-barometer in each series indicate that the alkaline magma equilibrated at shallow crustal depths under a pressure of about 3-4.5 kbar and approximating a crystallization depth of 9-14 km. The NAVs are slightly depleted in isotopic composition, with respect to 87Sr/86Sr (ranging from 0.705018 to 0.705643) and 143Nd/144Nd (ranging from 0.512662 to 0.512714) that indicate young Nd model ages (0.51-059 Ga). This may indicate that the parent melts tapped a homogeneous and young lithospheric mantle source which was metasomatized by subduction-derived sediments during the Late Mesozoic. Pb isotopic compositions (206Pb/204Pb = 18.85-18.95; 207Pb/204Pb = 15.60-15.74; 208Pb/204Pb = 38.82-39.25) may also be consistent with a model for an enriched subcontinental lithospheric mantle source. Lithospheric thinning and resultant upwelling of asthenosphere induced by lithospheric delamination may have favoured partial melting of chemically enriched, young lithospheric mantle beneath the Eastern Pontides. Then, the melt subsequently underwent a fractional crystallization process along with or without minor amounts of crustal assimilation, generating a wide variety of rock types in a post-collision extensional regime in the Eastern Pontides during the Neogene.

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  • MakaleYalnız künye2008
    Landslide susceptibility mapping for a landslide-prone area (Findikli, NE of Turkey) by likelihood-frequency ratio and weighted linear combination models

    Akgun, Aykut; Dag, Serhat; Bulut, Fikri

    Landslides are very common natural problems in the Black Sea Region of Turkey due to the steep topography, improper use of land cover and adverse climatic conditions for landslides. In the western part of region, many studies have been carried out especially in the last decade for landslide susceptibility mapping using different evaluation methods such as deterministic approach, landslide distribution, qualitative, statistical and distribution-free analyses. The purpose of this study is to produce landslide susceptibility maps of a landslide-prone area (Findikli district, Rize) located at the eastern part of the Black Sea Region of Turkey by likelihood frequency ratio (LRM) model and weighted linear combination (WLC) model and to compare the results obtained. For this purpose, landslide inventory map of the area were prepared for the years of 1983 and 1995 by detailed field surveys and aerial-photography studies. Slope angle, slope aspect, lithology, distance from drainage lines, distance from roads and the land-cover of the study area are considered as the landslide-conditioning parameters. The differences between the susceptibility maps derived by the LRM and the WLC models are relatively minor when broad-based classifications are taken into account. However, the WLC map showed more details but the other map produced by LRM model produced weak results. The reason for this result is considered to be the fact that the majority of pixels in the LRM map have high values than the WLC-derived susceptibility map. In order to validate the two susceptibility maps, both of them were compared with the landslide inventory map. Although the landslides do not exist in the very high susceptibility class of the both maps, 79% of the landslides fall into the high and very high susceptibility zones of the WLC map while this is 49% for the LRM map. This shows that the WLC model exhibited higher performance than the LRM model.

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