Zeminlerin Mekanik Davranışının Modellenmesi

Konferans Bildirisi -- Teorik ve Uygulamalı Mekanik Türk Milli Komitesi, 2008Conference Paper -- Theoretical and Applied Mechanical Turkish National Committee, 2008Zemin–yapı etkileşimi problemlerinde, zeminin cinsi, rijitliği ve deformasyon özellikleri çok önemlidir. Araştırmacılar genellikle, üst yapı davranışı üzerinde yoğunlaştıkları için zemin davranışı basite indirgenip, zemin lineer elastik malzeme kabul edilmekte ve sadece elastisite modülü ve Poisson oranı gibi birkaç parametreye ihtiyaç duyulmaktadır. Gerçekte zemin davranışı lineer elastik olmadığı gibi çok karmaşık bir yapıya sahiptir. Bu çalışmada kum zeminler üzerine oturan dairesel temellerin taşıma kapasiteleri laboratuar ortamında küçük ölçekli model deneylerle ve sayısal analiz yöntemleriyle araştırılmıştır. Sonlu elemanlar yöntemine dayalı PLAXIS V.8.2 (Finite Element Code for Soil and Rock Analyses) bilgisayar yazılımı kullanılarak yapılan sayısal analizlerde Lineer Elastik, Mohr Coulomb ve Pekleşme Zemin modelleri kullanılmıştır. Sayısal analiz sonuçları model deney sonuçları ile karşılaştırılmıştır. Sonuçta deneysel verilerle Pekleşme Zemin modeli kullanılarak elde edilen sayısal verilerin birbirleri ile daha uyumlu olduğu gözlenmiş, kum zeminler üzerine oturan dairesel temellerin taşıma kapasitesinin hesabında Pekleşme Zemin modeli parametrelerinin kullanılmasının daha uygun olacağı kanaatine varılmıştır. Ayrıca, Pekleşme Zemin modelinde kullanılan çeşitli parametrelerin (içsel sürtünme açısı, rijitlik modülleri) zemin davranışına etkisi ile ilgili parametrik çalışmalar da yapılmış, sonuçlar yorumlanmaya çalışılmıştır.In soil-structure interaction problems, soil type, soil rigidity and soil deformation characteristics are important. Researchers commonly focused on structure behavior therefore soil behavior is simplified assuming soil as a linear elastic material and need a few parameters such as modulus of elasticity and Poisson’s ratio. In reality, soil behavior is not linear elastic, just the opposite, soil has a very complex structure. In this study, the bearing capacity of circular foundation rested on sandy soils was investigated by small scale model tests in laboratory and numerical analyses. Numerical analyses were performed with a finite element method based computer software program PLAXIS V.8.2 (Finite Element Code for Soil and Rock Analyses) and Linear Elastic, Mohr Coulomb and Hardening Soil models were applied in these numerical analyses. The results of numerical analyses and model test were compared. Eventually, it was observed that results from Hardening Soil model had good agreement with model test results and it was proposed that in sandy soil rested circular foundation’s bearing capacity calculation using Hardening Soil model parameters was most suitable. Additionally, a parametric study concerning with the effect of some Hardening Soil model parameters (friction angle, oedometer and triaxial rigidity modulus) on soil behavior was conducted and the results were discussed

The Effect of Transportation Investments on Urban Logistics: Istanbul Sample

This paper defines the term of urban logistics, describes its significance, scope, shareholders, the factors affecting it, as well as the relevant performance criteria. Herein you will also find detailed information about the COST 321, a European Action which is considered as important for the urban logistics sector. This study outlines the urban logistics sector in Turkey, including the current transportation networks of Istanbul, a metropolis which has so far been experiencing an unplanned urbanization. In addition, the article claims that due to its geographical position, industrial opportunities, ever-growing population, connections, and infrastructure, urban transportation has become more of an issue for the city.  This study also analyzes endeavors of the last decade that aim to solve these above-mentioned problems, and their impacts. These impacts were analyzed based on the findings about COST 321, and possible logistics solutions were suggested within the study

Insulin resistance and serum leptin levels in men with obstructive sleep apnea syndrome

Aim: The aim of this study was to assess the insulin resistance andserum leptin levels in patients with obstructive sleep apnea syndrome(OSAS), and to compare body mass indexes (BMI) of OSAS patients withmatched controls without OSAS.Method: Twenty eight patients having apnea-hypopnea index (AHI)?5included in the study. Thirty two healthy subjects assumed as a controlgroup. Venous blood was obtained in the fasting state for themeasurement of glucose, insulin and leptin levels. Insulin resistanceindex was based on the homeostasis model assesment method (HOMAIR).Result: There was no significant difference in the serum leptin levels(control group, 32.88±24.22 ng/ml, OSAS group, 24.93±25.84 ng/ml) and HOMA-IR (control group, 3.01±1.81, OSAS group, 2.58±1.21)between control group and OSAS patients. Insulin resistance and circulatingplasma leptin concentrations in OSAS patients were independentof the AHI and were not different from the control group.Conclusion: We concluded that insulin resistance and plasma leptinconcentrations are mostly associated with the degree of obesity andBMI. Those parameters seem not to be related with the AHI in OSASpatients

Yumuşak kil zeminlerin geogrid danatı ile güçlendirilmesi

TEZ7574Tez (Doktora) -- Çukurova Üniversitesi, Adana, 2009.Kaynakça (s.286-293) var.xxii, 318 s. : res. ; 29 cm.In this study, the bearing capacity and settlement behavior of shallow foundations on a natural clay reinforced with geogrid layers were investigated using a large scale field tests. Circular, rigid model foundations with the diameters of 30cm, 45cm, 60cm and 90cm were used in the tests. Geogrids used as reinforcement materials were placed in granular fill bed compacted over the natural clay soil. The effects of parameters such as thickness of the granular fill layer, the location of the first layer of reinforcement, the vertical spacing of reinforcement layers and the number of reinforcement layers on bearing capacity and settlement were investigated in the tests. After field tests, numerical analyses were carried out with finite element based two and three dimensional software PLAXIS and the results obtained were compared with experimental results. Then, scale effect analyses with foundation sizes were conducted and some statistical relations were suggested.Bu çalışmada, geogrid donatı ile güçlendirilen doğal kil zeminlere oturan yüzeysel temellerin taşıma gücü ve oturma davranışları, arazi ortamında büyük ölçekli yükleme deneyleri yapılarak irdelenmiştir. Deneylerde yüzeysel temel olarak 30cm, 45cm, 60cm ve 90cm çaplarında dairesel rijit model temel plakaları kullanılmıştır. Güçlendirme elemanı olarak kullanılan geogrid donatılar, doğal kil zemin üzerine serilen stabilize dolgu tabakası içine yerleştirilmiştir. Deneylerde; stabilize dolgu tabakası kalınlığı, ilk donatı derinliği, donatılararası mesafe ve donatı tabaka sayısı gibi parametrelerin taşıma kapasitesi ve oturma üzerindeki etkileri araştırılmıştır. Deneylerin ardından sonlu elemanlar yöntemine dayanan PLAXIS yazılımı kullanılarak iki ve üç boyutlu sayısal analizler yapılmış, elde edilen sonuçların deney sonuçları ile olan uyumu araştırılmıştır. Daha sonra temel boyutları esas alınarak ölçek etkisi analizi yapılmış ve bir takım istatistiksel bağıntılar önerilmiştir.Bu çalışma Ç.Ü. Bilimsel Araştırma Projeleri Birimi Tarafından Desteklenmiştir. Proje No:MMF2006D28 TÜBİTAK 106M49

The Effect of Transportation Investments on Urban Logistics: Istanbul Sample

This paper defines the term of urban logistics, describes its significance, scope, shareholders, the factors affecting it, as well as the relevant performance criteria. Herein you will also find detailed information about the COST 321, a European Action which is considered as important for the urban logistics sector. This study outlines the urban logistics sector in Turkey, including the current transportation networks of Istanbul, a metropolis which has so far been experiencing an unplanned urbanization. In addition, the article claims that due to its geographical position, industrial opportunities, ever-growing population, connections, and infrastructure, urban transportation has become more of an issue for the city. This study also analyzes endeavors of the last decade that aim to solve these above-mentioned problems, and their impacts. These impacts were analyzed based on the findings about COST 321, and possible logistics solutions were suggested within the study

Retinal nerve fiber layer thickness in patients with essential tremor

Ornek, Nurgul/0000-0003-3068-1831WOS: 000367386600006Objective: To investigate the retinal nerve fiber layer (RNFL) thickness in essential tremor (ET). Methods: Twenty-seven eyes of 27 patients with essential tremor were included in this study. Twenty-seven eyes of 27 healthy volunteers served as controls. All eyes were examined with spectral domain optical coherence tomography (OCT) (Retinascan Advanced RS-3000; NIDEK, Gamagori, Japan) using image filling software program (NAVIS-EX, NIDEK, Tokyo, Japan). Results: No statistically significant difference was detected between ET patients and control group for overall (RNFL) and foveal retinal thickness parameters. [RNFL thickness (Average thickness p=0.86, superior average p=0.22, inferior average p=0.24, nasal average p=0.06, temporal average p=0.88), foveal retinal thickness p=0.63] There was no relationship between OCT parameters and age, gender and duration of ET (all p>0.05). Conclusion: We did not find altered RNFL and foveal thickness values in patients with ET compared to controls. Retinal thickness changes do not seem to be a potentially useful biomarker in ET patients

Determination of optimum post embedment depth for C120 steel posts using field and full scale crash test

C120 steel sections are the most widely used post shapes in European guardrail designs. The design length of these posts is determined based on guardrail containment level and engineering judgment. The soil properties where these posts are embedded are usually not considered in design. It is a well-known fact that the crash test performance of soil embedded posts depends mostly on post–soil interaction and post embedment depth (PED). In this study, a series of field impact tests were performed on soil embedded C120 posts to determine optimum PED for three different soil conditions. Seven different PED varied from 650 to 900mm was used for each soil type. Based on these findings a full-scale crash test is performed on a guardrail to verify optimum PED for hard soil conditions. With the use of optimum length guardrail posts considerable amount of installation time, labor and material savings are expected

Factors affecting systematic marketing approach of Turkish construction firms

Günümüzde eğitim ve teknolojideki ilerlemeler, toplumun refah düzeyindeki artıs müsterilerin daha kaliteli binalar talep etmesine neden olmaktadır. Bu durum insaat sektörünün içinde bulunduğu rekabetçi pazar ortamında sirketlerin doğru projelerle ve doğru fiyatlandırma anlayısı ile müsterilerin karsısına çıkmasını gerektirmektedir. Bu da ancak sirketlerin insaat öncesi ön hazırlık çalısmalarının titizlikle yürütmesi ile mümkün olmaktadır. Bunun yanında sirketin kisisel satma ve tutundurma faaliyetlerinin (reklâm, firmanın tanıtımını yapacak aktiviteler vb.) etkinliği de olusan bu pazarı elde etmek için önem arz etmektedir. Sirketin sistematik bir pazarlama anlayısına sahip olması, diğer bir deyisle kendi bünyesinde kendisini diğer sirketlerden ayrılmasını sağlayacak değerler insa etmesi ile mümkün olacaktır. Bu arastırma kapsamında insaat sirketlerinin pazarlama kavramını algılama ve uygulama düzeyi incelenmistir. Sirketlerin pazar içinde ve rakip firmalarla etkili bir biçimde rekabet etmelerini, sistematik bir pazarlama anlayısına sahip olmasını sağlayacak doğru fiyatlandırma ve tutundurma stratejileri üzerinde durulmustur. Sirketlerin bu yönde bir yönetim tarzı sergileyip sergilemedikleri ile ilgili değerlendirmede bulunabilmek için insaat sektöründe yer alan orta ve büyük ölçekli 50 firma ile bir anket çalısması düzenlenmistir. Anketin amacı, öncelikle insaat firmalarının pazarlama sürecini etkileyen fiyatlandırma ve tutundurma stratejilerini belirlemektir. Anket çalısması sonucunda ayrıca, firmaların pazarlama sürecini algılama ve uygulama düzeyleri ve uygulamadaki eksiklikleri ortaya çıkarılmıstır. Sonuçlar, literatür bulguları ısığında değerlendirilmistir.Due to improvements in education and technology and increase in prosperity of the society, the consumers demand buildings with higher quality. This requires construction companies which are working in a competitive marketing environment to come up with right projects and bidding strategies. This becomes possible by preparing rigorous preconstruction feasibility studies. Additionally, the effectiveness of personal selling and promotion activities of the company is important to acquire a market share which can be realized by having systematic marketing concept. In this study, the perception and application level of marketing concept of construction firms are investigated. Specifically, bidding and promotion strategies which enable the companies to have systematic marketing concept in order to compete with other companies in the market are discussed. To evaluate whether this management approach is applied by the companies, a questionnaire was performed with fifty Turkish construction firms. The purpose of the questionnaire was to determine bidding and promotional activities affecting the marketing process of the companies. Depending on the results of the questionnaire, the level of perception and application of the marketing process and deficiency in practices are discussed. Results are evaluated in the light of literature findings