Dynamic Response of a Single Pile Embedded in Sand Including the Effect of Resonance

In this paper, responses of a single pile embedded in sand soil (loose and dense) under dynamic loading (sinusoidal dynamic vibrations of 0.1 g to 0.5 g) have been investigated by two-dimensional analysis using the finite element method (FEM). Viscous (dashpot) boundaries have been used for taking the boundary effects of far-field into account. The applicability and accuracy of site responses of two-dimensional analysis due to the FEM modelling have been well verified with one-dimensional site responses. The results indicate that the relative density of sand (loose, dense) becomes prominent for the displacements of the pile, specifically under the frequency effects of resonance. While the pile in loose sand causes the displacements of 0.1 m to 0.5 m, the pile in dense sand leads to the displacements of 0.05 m to 0.25 m, proportionally with the dynamic loads from 0.1 g to 0.5 g. Moreover, the displacements reach their peak value at the frequency ratio of the resonance case. Viscous boundaries are found sufficient for modelling excessive displacements due to dynamic loading. However, the displacements reveal that high vibrations (> 0.1 g for loose sand, > 0.2 g for dense sand) influencing the pile deformations are critical for the issues of settlements. This is more significant for the resonance case in order for ensuring sufficient design. Consequently, the findings from the study are promising good contributions for pile design under the dynamic effect

Investigation of the behaviour of piles under the dynamic load.

TEZ12528Tez (Yüksek Lisans) -- Çukurova Üniversitesi, Adana, 2016.Kaynakça (s. 115-118) var.XIX, 120 s. :_res. (bzs. rnk.), tablo ;_29 cm.Bu çalışmada, kum zemine gömülü tekil bir kazığın dinamik yük etkisindeki davranışı sayısal olarak incelenmiştir. Bu amaçla gerçekleştirilen analizlerde, sonlu elemanlar yöntemine dayanan Plaxis 2D bilgisayar yazılımı kullanılmıştır. Ayrıca, bu programın dinamik analiz modülünün ürettiği sonuçların doğruluğunu kontrol etmek için zeminlerin bir boyutlu yer tepki analizini gerçekleştirebilen Deepsoil bilgisayar yazılımı kullanılmıştır. Her iki programdan elde edilen sonuçların oldukça uyumlu olduğu gözlenmiştir. Analizlerde, zemin sıkılığının etkisi, dinamik yükün genliğinin ve frekansının etkisi, kazık başlığının etkisi, kazık rijitliğinin ve sünekliğinin etkisi detaylı olarak incelenmiştir. Bu parametreler için Plaxis 2D programında yer alan iki farklı zemin modeli kullanılmış ve analizlerde kullanılan dinamik yük zemin tabanına etki ettirilen sinüzoidal bir yer hareketi olarak belirlenmiştir. Araştırılan her parametrenin kazık davranışında önemli bir etkisinin olduğu görülmüş ve elde edilen sayısal sonuçlar detaylı olarak sunulmuştur.In this study, the behaviour of a single pile under the dynamic load has been investigated numerically in sand soil conditions. Numerical analyses carried out for this purpose have been performed by using Plaxis 2D which is a software based on finite element method. Furthermore, Deepsoil computer software that can perform one-dimensional site response analysis of ground has been used to check the accuracy of the results produced by Plaxis 2D dynamic analysis module. It has been observed that the results obtained from both programs are quite compatible. In the analyses, the effect of the relative density of sand, the effect of the dynamic load amplitude and frequency, the effect of the pile cap, and the effect of the pile stiffness and flexibility have been investigated in detail. For these parameters, two different soil models in the Plaxis 2D have been used and the dynamic load used in the analyses has been determined as a sinusoidal ground motion applied to sand bottom. It has been observed that the all investigated parameters affect significantly the behaviour of pile and the results obtained from analyses have been presented in detail

Geogrid Donatılı Kumda Grup Ankraj Plakalarının Çekme Kapasitesinin İncelenmesi

Bu çalışmada, geogridle güçlendirilmiş ve güçlendirilmemiş kum zemindeki grup ankrajların çekme kapasitesi deneysel ve sayısal olarak incelenmiştir. Tek ve 2x2 yerleşim düzenindeki ankraj plakalarında gömülme oranı ve geogrid tabakası sayısının çekme kapasitesine etkisi araştırılırken, ankrajlar arası mesafe oranı, geogrid tabakasının ilk derinliği, geogrid tabakaları arası düşey mesafe ve geogrid tabakasının uzunluğu sabit tutulmuştur. Deneyler sonlu elemanlar programına dayalı Plaxis 3D bilgisayar programı ile sayısal olarak modellenmiş ve analiz edilmiştir. Deneysel çalışmalar ve sayısal analizlerden elde edilen sonuçlar karşılaştırılmış ve sayısal analizin ankraj plakasının çekme kapasitesini tahminindeki başarısı araştırılmıştır. Sonuç olarak, geogridle güçlendirmenin ankraj plakasının çekme kapasitesini 2 kata kadar artırdığı görülmüştür.In this study, the uplift capacity of group anchors has been investigated in sand with and without geogrid reinforcement experimentally and numerically. While the investigated parameters are the effect of embedment ratio of anchors and number of geogrid layers for a single anchor plate and 2x2 anchor configuration, the constant parameters are spacing ratio between anchors, depth of the first layer of geogrid, vertical spacing ratio of geogrid layers and length of geogrid. Experimental studies have been modelled and analyzed with Plaxis 3D which is a finite elements software. The results obtained from both of the studies have been compared and the validity of the numerical analysis has been investigated on the uplift capacity of anchor plate. As a result, it was shown that depending on the reinforcement geogrid, the uplift capacity of anchor plate can be improved by up to 2 times that of the unreinforced sand

Teaching computer architecture by designing and simulating processors from their bits and bytes

Teaching computer architecture (Comp-Arch) courses in undergraduate curricula is becoming more of a challenge as most students prefer software-oriented courses. In some computer science/engineering departments, Comp-Arch courses are offered without the lab component due to resource constraints and differing pedagogical priorities. This article demonstrates how students working in teams are motivated to study the Comp-Arch course and how instructors can increase student motivation and knowledge by taking advantage of hands-on practices. The teams are asked to design and implement a 16-bit MIPS-like processor with constraints as a specific instruction set, and limited data and instruction memory. Student projects include following three phases, namely, design, desktop simulator implementation, and verification using hardware description language (HDL). In the design phase, teams develop their Comp-Arch to implement specified instructions. A range of designs resulted, e.g., (a) a processor with extensive user-defined instructions resulting in longer cycle times (b) a processor with a minimal instruction set but with a faster clock cycle time. Next, teams developed a desktop simulator in any programming language to execute instructions on the architecture. Finally, students engage in Verilog Hardware Description Language (HDL) projects to simulate and verify the data-path designed during the initial phase. Student feedback and their current understanding of the project were collected through a questionnaire featuring varying Likert scale questions, some with a ten-point scale, and others with a five-point scale. Results of the survey show that the hands-on approach increases students’ motivation and knowledge in the Comp-Arch course, which is centered around computer system design principles. This approach can also be effectively extended to related courses, such as Microprocessor Design, which delves into the intricacies of creating and implementing microprocessors or central processing units (CPUs) at the hardware level. Furthermore, the present study demonstrates that interactions, specifically through peer reviews and public presentations, between students in each phase increases their knowledge and perspective on designing custom processors

Mycobacterial flora of the skin in leprosy

Attempts were made to investigate mycobacteria other than Mycobacterium tuberculosis on the hands and in biopsy specimens of fifty leprosy patients receiving treatment at the center for Leprosy at Üstanbul Medical School, who were under control for reaction, who were maintained for their lesions or who were hospitalized for non-leprosy reasons. The same investigation was also performed on the hands of fifty healthy subjects who were selected randomly as control group. On the hands of one male subject wtih lepromatous leprosy (2%) mycobacteria other than Mycobacterium tuberculosis was cultivated, whereas these bacteria were not recovered in the control group. Results were not considered to be statistically significant

Serum Homocysteine Levels In Patients With Non-Alcoholic Fatty Liver Disease

Aim: Non-alcoholic fatty liver disease (NAFLD) is a common disorder which causes serum liver enzyme elevation. Elevated homocysteine levels was demonstrated in fatty liver disease and chronic liver failure. However, enough data related with homocysteine levels in patients with NAFLD is not available. We aimed to find out whether there is an association between homocysteine levels and NAFLD. Methods: Twenty patients (14 men, 6 women) with NAFLD and 20 healthy adults (13 men, 7 women) enrolled in the study. Fasting blood samples were obtained and serum homocysteine levels were measured by fluorescence polarization immunoassay (FPIA) technology. Oral glucose tolerance test was performed and serum insulin, c-peptide, and lipoprotein levels were also measured. Results: The mean serum homocysteine levels (+/-SD) were 13.44±3.10 μmol/L and 11.62 ±1.34 μmol/L in NAFLD and the control group, respectively. Mean serum homocysteine level in the NAFLD group was significantly higher than in control group (p=0.015). Fasting blood glucose, insulin, total cholesterol and low density lipoprotein (LDL) cholesterol were all found higher than the control group. Conclusion: The serum homocysteine levels were significantly higher in patients with NAFLD than in control group. This may point out that high homocysteine levels may be associated with NAFLD

Oxidative Stress in Migraine with and Without Aura

Migraine is the most common neurological disorder, but the molecular basis is still not completely understood. An impairment of mitochondrial oxidative metabolism might play a role in the pathophysiology. The goal of this study was to investigate the differences in oxidative stress status with the measurement of erythrocyte superoxide dismutase (SOD), catalase activity, and malondialdehyde (MDA) levels in the migraine patients with or without aura and attack. There were 56 patients (46 female, 10 male) in the migraine group and 25 matched healthy subjects in the control group. The patients comprised 37 with migraine without aura (MWoA], 19 with migraine with aura (MWA), and 22 with headache attack. The MDA levels of patients in the migraine group were significantly higher than that in the control group. The SOD activity was significantly higher in the MWA as compared to MWoA. There was no significant correlation between these levels and headache attack period. Conclusively, in this preliminary study, we had found increased oxidative stress in the migraine patients especially the patients with MWA. Further knowledge about this issue may contribute the cause and complications of migraine and may be essential for development of treatment approaches