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Öğe Çağlayan (Suçatı-Kahramanmaraş) Trafo Merkezi Kazı Şevlerinin Duraylılık Analizi(Çukurova Üniversitesi, 2022) Özbek, Ahmet; Natur, Ozan; Keskin, Mehmet SalihSon yıllarda Mühendislik yapıları inşa edilirken, özellikle eğimli topoğrafyaya sahip alanlarda yapılan kazılar nedeniyle, oluşturulan şevlerin duraylılığı, kazı sonunda ve uzun dönemde önem taşımaktadır. Şevlerde duraysızlık sorununu, doğru bir şekilde değerlendirebilmek için duraysızlığa neden olan koşulların ve zemine ait parametrelerin doğru seçilmesi ve bu doğrultuda şev duraylılık analizlerinin yapılması gerekmektedir. Bu çalışma kapsamında, inceleme alanı olarak, Çağlayan (Suçatı-Kahramanmaraş) Trafo Merkezi temel alanında oluşturulan kazı şevleri seçilmiştir. Seçilen kazı şevlerinde, duraysızlığa neden olan parametreler ve kayma mekanizmasının belirlenmesi için Limit denge yöntemlerinden Slide-5 bilgisayar programı ile sonlu elamanlar yöntemine dayanan, Plaxis 7.20 programı kullanılarak iki farklı kesit profili üzerinde, duraylılık analizi yapılmıştır. Yapılan analizlerde, yeraltısuyu ve deprem durumunda şevlerin, duraysızlığa uğradığı ve modellerin destek ve dizayn değişikliğine ihtiyacı olduğu tespit edilmiştir. Ayrıca analizler sonunda, şevin duraylılığının sağlanması için iyileştirme yöntemi önerilmiştir. İyileştirme amaçlı, istinat duvarı çözümü ele alınmıştır. Hem sonlu elemanlar hem de limit denge yöntemi ile gerçekleştirilen analizlerde; statik, dinamik ve yeraltı suyu koşullarında şevin duraylılığının arttığı ve gerekli güvenlik sayısına ulaşılarak kazı şevlerinde duraylılık sağlanmıştır.Öğe Centrifuge model tests and numerical analysis of uplift capacity of strip anchors in geogrid-reinforced sand(MDPI, 2023) Bildik, Selçuk; Dickin, Edward Alan; Keskin, Mehmet Salih; Ilamparuthi, Kanniappan; Laman, MustafaAnchor-type foundations are one of the foundation types used in structures subject to tensile forces. These anchors are generally designed according to the weight of the soil on them depending on the depth they are buried at and the frictional resistance obtained from the failure surfaces during failure. One method of increasing the uplift capacity of the foundation without increasing the burial depth is the use of geogrid material. In this study, the uplift capacities of strip anchor plates at different embedment depths were investigated by considering the geogrid effect placed in different combinations. The aim of the study is to investigate whether a more economical solution can be obtained by using geogrid without increasing the embedment depth of the anchor plate. Experiments were carried out using centrifugal experimental setup, which gives values closer to the real results. The tests were performed on sand of two different densities for anchor burial depths H/B = 2 and H/B = 5. According to the results, the uplift capacity is significantly improved when geogrid is used. As the reinforcement configuration, the use of a single geogrid layer placed just above the anchor plate with an inclination angle of 45 degrees gave more effective results than using the geogrid horizontally and vertically. In the study, up to 98% increases in uplift capacity were obtained with reinforcement. In addition, the prototype model was analyzed with a numerical program based on the finite element method, and the results were compared with the experimental results. As a result of the comparison, it was observed that the experimental and numerical results were compatible with each other. Suggestions for practice are presented using the results obtained.Öğe Effect of seismic isolation on the performance of high-rise buildings with torsional instability(MDPI, 2023) Sarıtaş, Fevzi; Bedirhanoğlu, İdris; Konak, Arova; Keskin, Mehmet SalihSeismic bearings have been used to mitigate the harmful effect of the earthquakes. Torsion mode, one of the most important irregularities, generally increases the shear forces to the vertical members such as columns and shear walls in turn this may results in brittle failure of the reinforced concrete (RC) members. Accordingly, it is vital to eliminate the torsion failure mode or switch to the higher modes with lower mass contribution. This study has evaluated the seismic performance of a high-rise building with torsion mode through push-over analysis including nonlinear time history analyses. The damage conditions of RC structural members are defined considering the Eurocode definitions and general performance assessments of the building have been evaluated accordingly. Lead rubber bearings have been used for base isolation system. By using enough number of rubber bearings, the dominant torsion mode (first free vibration mode) has been shifted to higher modes. Various earthquake records have been used in non-linear dynamic analysis to evaluate the positive effects of the bearings. The results revealed that proper arrangement of rubber bearings in structural plan of ground floor can effectively improve dynamic behavior of a high rise building with torsional instability to achieve better seismic performance.Öğe Experimental and numerical studies of vertical stresses beneath the circular footings on sand(MDPI, 2023) Keskin, Mehmet Salih; Bildik, Selçuk; Laman, MustafaThis paper presents experimental and numerical studies of the vertical stress distribution beneath the centerline of circular footings resting on sand. Vertical stress values due to circular load in medium-dense sand were measured using soil stress transducers. Reduced-scale laboratory model tests were carried out in a square-shaped test box, and vertical stresses were measured at the centerline of the circular footing at different depths of the sand. In order to determine the effect of footing width on vertical stress distribution, laboratory experiments were performed on circular footings of different diameters. In addition, a series of finite element analyses was carried out on the test model to validate the findings of the experimental study. In the numerical analysis, the sand was modeled as a non-linear elastoplastic material. The analyses were performed using the finite element method with two-dimensional axisymmetric and three-dimensional conditions. The results obtained from laboratory model tests and numerical analysis were compared with the vertical stress values obtained from the theoretical solution in the literature. Vertical stress distribution in horizontal planes at any depth from the footing base shows the same characteristic form in all methods. However, some differences were observed between experimental, numerical, and theoretical results and were discussed.Öğe Experimental study of bearing capacity of strip footing on sand slope reinforced with tire chips(Techno-Press, 2014) Keskin, Mehmet Salih; Laman, MustafaTire chips and tire chips-soil mixtures can be used as alternative fill material in many civil engineering applications. In this study, the potential benefits of using tire chips as lightweight material to improve the bearing capacity and the settlement behavior of sand slope was investigated experimentally. For this aim, a series of direct shear and model loading tests were conducted. In direct shear tests, the effect of contents of the tire chips on the shear strength parameters of sand was investigated. Different mixing ratios of 0, 5, 10, 15 and 20% by volume were used and the optimum mixing ratio was obtained. Then, laboratory model tests were performed on a model strip footing on sand slope reinforced with randomly distributed tire chips. The loading tests were carried out on sand slope with relative density of 65% and the slope angle of 30 degrees. In the loading tests the percentage of tire chips to sand was taken as same as in direct shear tests. The results indicated that at the same loading level the settlement of strip footing on sand-tire chips mixture was about 30% less than in the case of pure sand. Addition of tire chips to sand increases BCR (bearing capacity ratio) from 1.17 to 1.88 with respect to tire chips content. The maximum BCR is attained at tire chips content of 10%.Öğe Predicting liquefaction-induced lateral spreading by using the multigene genetic programming (MGGP), multilayer perceptron (MLP), and random forest (RF) techniques(Springer Science and Business Media, 2023) Kaya, Zülküf; Latifoğlu, Levent; Uncuoğlu, Erdal; Erol, Aykut; Keskin, Mehmet SalihLandslides refer to a wide range of processes that result in the downward and outward movement of slope-forming materials, which may spread. Estimating lateral spreading of soil is essential because of the complexities associated with the lateral spreading behavior. Existing empirical models for predicting liquefaction-induced lateral spread displacement are developed using a dataset that varied in terms of earthquake magnitude, source distance, ground slope, layer thickness, fines content, and grain size. The aim of this study is to increase the accuracy of earthquake-induced lateral spreading prediction using multigene genetic programming (MGGP), multilayer perceptron (MLP), and random forest (RF) model. MGGP, MLP, and RF model predictions of lateral spreading are compared with the results anticipated using machine learning techniques and conventional approaches. Results showed that the MGGP outperforms the Hamada, Youd, MLP, and RF equations for estimating maximum lateral displacement under free-face and gently sloping ground conditions according to the comparisons. The MGGP, which is proved to be better, was also utilized to estimate total lateral displacement for Adapazari data, along with machine learning techniques and conventional approaches.Öğe Şerit ankraj plakalarının çekme kapasitesi davranışının farklı koşullar altında sayısal analizi(Dicle Üniversitesi Mühendislik Fakültesi, 2017) Korkmaz, Bilal; Keskin, Mehmet SalihBu çalışmada, kumlu zeminlere gömülü şerit ankraj plakalarının çekme kapasitesi davranışı sayısal olarak analiz edilmiştir. Bu amaçla, prototip bir model oluşturulmuş ve farklı koşullar için sonlu elemanlar analizleri gerçekleştirilmiştir. Çalışmada, sonlu elemanlar yöntemi ile çözüm yapan PLAXIS bilgisayar programı kullanılmıştır. Analizlerde, ankraj genişliği, gömülme derinliği ve kumun sıkılık derecesi parametrelerinin, şerit ankraj plakalarının çekme kapasitesi davranışına etkileri incelenmiştir. Tüm analizler iki farklı malzeme modeli (Mohr-Coulomb ve Hardening Soil) kullanılarak gerçekleştirilmiş ve elde edilen çekme kapasitesi değerleri, teorik sonuçlarla karşılaştırılmıştır. Analizler sonunda elde edilen sonuçlara göre, kuma gömülü şerit ankraj plakalarının çekme kapasitesi, plaka genişliği, ankraj gömülme derinliği ve kumun sıkılığının artmasına bağlı olarak artış göstermektedir. Hardening Soil malzeme modeli kullanılarak gerçekleştirilen analizlerden elde edilen çekme kapasitesi değerleri, Mohr-Coulomb malzeme modeli ile elde edilen değerlerden daha büyüktür. Ayrıca, sayısal analizlerden elde edilen çekme kapasitesi değerleri ile teorik çözümden elde edilen değerler arasında genel bir uyum söz konusudur. Ancak, teorik çözüm ile elde edilemeyen deplasman ve gerilme davranışının sonlu elemanlar yöntemiyle gözlenebilmesi konunun daha rahat anlaşılmasına olanak sağlamaktadırÖğe Şev stabilitesinin iki ve üç boyutlu modeller ile incelenmesi(Dicle Üniversitesi Mühendislik Fakültesi, 2015) Taşkıran, Taha; Yavuz, Veysel Süleyman; Keskin, Mehmet SalihBu çalışmada, sonlu elemanlar yönteminin, şev stabilitesi problemlerinin analizinde uygulanabilirliği iki ve üç boyutlu modeller kullanılarak araştırılmıştır. Çalışmada, şevlerin stabilitesinin sonlu elemanlar yöntemi ile analizinde kullanılan mukavemet azaltma tekniğinden bahsedilmiş ve kumlu bir şev örneği ele alınarak göçmeye karşı güvenlik sayısı, mukavemet azaltma tekniği kullanılarak elde edilmiştir. Çalışmada iki ve üç boyutlu modellemenin sonlu elemanlar analizi üzerindeki etkileri araştırılmıştır. Ayrıca, limit denge yöntemi kullanılarak şev stabilite analizleri gerçekleştirilmiş ve elde edilen güvenlik sayıları sonlu elemanlar yöntemi ile elde edilen sonuçlarla karşılaştırılmıştır. Çalışma sonunda, üç boyutlu şev modeliyle elde edilen güvenlik sayısı değerlerinin iki boyutlu durumda elde edilen değerden daha büyük olduğu ve mukavemet azaltma tekniği ile elde edilen güvenlik sayısı değerlerinin, limit denge yöntemleri ile elde edilen güvenlik sayısı değerleriyle uyum içerisinde olduğu görülmüştürÖğe Stability of MSW landfill slopes reinforced with geogrids(MDPI, 2022) Keskin, Mehmet Salih; Kezer, SedatSlope stability is one of the main problems encountered in MSW (municipality solid waste) landfill designs. Slope stability calculations become difficult due to the heterogeneous structure of MSW landfills and leachate, and therefore, slope geometries are formed by choosing low slope angles for safe designs. This causes less waste to be stored on site. This study presents slope stability analyses of MSW landfills. Numerical analyses were performed using finite element and limit equilibrium methods. The stability behavior of landfill slopes was analyzed for both unreinforced and geogrid-reinforced conditions in order to investigate the effects of shear strength parameters, the unit weight of soil waste, and material model parameters. It has been seen that the stability of landfill slopes can be increased significantly using geogrid materials. When the optimum geogrid parameters obtained from the numerical analysis results are used, it has been observed that the safety factor of the slope can be increased by up to approximately two times. Slopes in landfills reinforced with geogrid reinforcements can be formed steeper, allowing more solid waste to be stored. Considering the high initial investment cost of MSW landfills, it has been concluded that storing more solid waste with the use of geogrids will provide significant economic gains. Based on the results, the optimum values of geogrid parameters were determined and suggested for maximum reinforcing effects in MSW landfill slopes.
