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Effect of sand column on compressibility and shear strength of fibrous peat
Peat is found in many countries throughout the world where it can be generally seen in thick layers in limited areas. Peat is an extreme form of soft soil and is considered problematic due to the low shear strength and large compressibility. This project presents laboratory finding on the compressibility and shear strength characteristics of fibrous peat with sand column.The peat used in the study is taken from Sakarya region, Turkey. It is classified as fibrous peataccording to ASTM D 1997-91 and due to its low to medium degree of decomposition classified as H_1-H_4 in von Post scale. The natural water content of the peat is 236 % and its liquid limit is 119%. In all tests, the fibrous peat used for the test passing #200 and remain on #100. The rounded sand used for making sand column is poorly graded passing from 2 mm sieve size and retaining on 0.075 mm sieve size. The tests focused on effect of diameter of granular column on shear strength and compressibility of the organic soil.Four different sand column diameters were used for compressibility and shear strength testswere (1.7, 2.5, 3.5and 4.7cm).All tests results showed that; when the ratio of sand column surface to organic soil surface area (S/O) increases; compression index (c_c); recompression index (c_( r)); and volume compressibility (m_v) decreases. Also,sand columns causes increase in (IFA)and reduction in (C) of the organic soil.
A parametric study on the behaviour of mechanically stabilized earth (MSE) wall using finite element method
Mechanically stabilized earth (MSE) walls offer simple construction techniques, pleasing aesthetics, and cost-effective solutions as an alternative to conventional gravity walls.This dissertation presents the analysis of reinforced soil retaining walls were carried out to review the engineering properties of the MSE wall and perform parametric studies various factors that may govern the behaviour of the MSE wall by using finite element program PLAXIS 2D. The geometric parameters such as reinforcement length, vertical spacing between the reinforcement layers, reinforcement stiffness, wall height, face element thickness, position of traffic load, and finally the type of reinforced soil were examined to investigate their effects on the forces developed in the reinforcement and the wall deformation. It is shown that the forces developed are largely independent of reinforcement length, reinforcement stiffness, and face element thikness. Generally, axial force increases with increasing the wall height, vertical spacing between the geogrid layers, and angle of internal friction for backfill soil. While, wall deformation are largely dependent on geogrid length and an acceptable resultes were obtained when using L/H equal to 0.7. Wall deformation also decreasing with increasing geogrid stiffness and therfore geogrid with higher strength is recomended to be used. Beside, the vertical spacing (Sv) between geogrid layers which also affect on the horizontal deformation and the minimum value can be used in the design of MSE walls equal to 0.5 m.
Numerical modeling and experimental evaluation of shrinkage of concretes incorporating fly ash and silica fume
Shrinkage is generally considered as an important hardened concrete property. During the drying process, free and absorbed water is lost from the concrete. When the drying shrinkage is restrained, cracks can occur, depending on the internal stresses in the concrete. The ingress of deleterious materials through these cracks can cause decrease in the compressive strength and the durability of concrete. In the first stage of the study, prediction models through gene expression programming (GEP) and neural network (NN) were derived. The data set used for training and testing covers the experimental data presented in the literature. In the second stage of the study presented herein, the findings of an experimental study on drying shrinkage behavior of concretes incorporated with silica fume (SF) and fly ash (FA) were reported. Free shrinkage strain measurements as well as corresponding weight loss were measured over 40 days of drying. The obtained experimental results were also used for the validation of the proposed prediction models. The highest amount of mineral admixture resulted in high shrinkage strain development. Moreover, the proposed NN model also accurately predicted the values obtained from experimental study. The errors obtained from GEP model were very high, especially for SF incorporated concrete Keywords: Shrinkage, modeling, Prediction, Experimental validation, Mineral admixtures
A study on explicit formulation of sorptivity of concretes containing mineral admixtures
In this thesis, mathematical models derived from gene expression programming (GEP) and artificial neural network (ANN) were used for prediction of sorptivity of concretes. For this, 151 data samples were collected from the previous studies.The common predicttion parameters were selected as water-to-binder ratio (w/b), total binder content (B), compressive strength of 150 mm cube speciment at 28 days (fc,28), aggregate-to-binder ratio (Agg./B) and age of concrete (A). Additionally, in order to evaluate the performance of the proposed models an experimental study was also conducted. The study was carried out on water cured and air cured concretes produced by w/b ratio of 0.45 with total binder content of 400 kg/m3. Moreover, silica fume (SF) and fly ash (FA) were used in different replacement levels. Total 9 different concrete mixtures with binary and ternary blends of SF and FA were produced. Both of the proposed models were proved to be effective enough for prediction of sorptivity of concretes. However, NN models was more accurate than GEP model. Moreover, validation study also indicated that the proposed mathematical models can be utilized as reliable prediction tools for estimation of sorptivity of concretes. Keywords: Sorptivity of concrete, Mineral admixtures, Artificial Neural Network, Gene Expression Programming
Comparative analysis of high-rise rc structures according tointernational seismic design codes
The field of earthquake engineering and seismology is of great importance to structural engineers around the world. The location, size and consequences of an earthquake are variable depending on several conditions. Surface conditions, boundary/fault type and distance from the boundary and hypocenter are all elements that dictate the outcome of a seismic event. Describing the effects of an earthquake can be difficult. Early records of earthquakes date back to ancient civilizations. In present study, a high-rise reinforced concrete building is analyzed namely, International building code and European code. This building composed of 20 floors, the area of floors (1 to 12) is 1750 m2. The area floors of (13 to 20 ) is 1225 m2. Applied live load is equal o.4 ton /m2, finish floor 0.3 ton /m2. The well known structure program ETABS has been used to analyze the structure .The Equivalent static method has been used to calculate the seismic loads . Table of displacement, moment story ,shear story,t orsion story, column moment and column shear are obtained.
Lateral load resisting systems in high-rise reinforced concrete buildings
The high-rise building becomes very important in construction because every day the prices of land are increasing and the demand is also increased. The more concern matter in high-rise building is lateral loads due to earthquake loads and wind loads. In this study, the classification of lateral load resisting systems has been discussed in chapter 2 for steel structures and reinforced concrete structures. The researcher focused on the reinforced concrete structures (moment resisting system, shear wall system, shear frame system, frame tube system). In chapters 3 and 4, the effects of lateral load (earthquake and wind) were taken in the behavior of building. In the present study, the high-rise reinforced concrete building was analyzed which consisted of 28 floors and it was symmetrical from story 1 up to story 28. The area of building was 625 (25m ˟ 25m), applied dead load is equal 0.5 ton/ , live load is 0.3 ton/ . The well-known structure program ETABS has been used to analyze the structure. The equivalent static method has been used to calculate the seismic load. Tables and charts of displacements and maximum drifts story were obtained. Keywords: lateral load resisting system, high rise buildings, earthquake load, wind load, stiffness, displacements.
Seismic base isolation in reinforce concretestructure
Base isolation is one of the most widely accepted seismic protection systems used in building in earthquake prone areas. The base isolation system separates the structure from its foundation and primarily moves it relative to that of the upper structure. The aim of this study is to reduce the base shear and story drifts due to earthquake ground excitation, applied to the superstructure of the building by installing base isolation devices at the foundation level and then to compare the different performances between the fixed base condition and base-isolated condition .The static equivalent lateral force of analysis, response spectrum and time history analysis and used on both of fixed base and base isolated buildings The key references that are used in this study are the related chapters of IBC2006 code for seismic isolated structures. In this work, this code is used for the design examples of elastomeric bearings. Furthermore, the internal forces develop in the superstructure during a ground motion is determined; and the different approaches defined by the codes towards the 'scaling factor' concept is compared in this perspective.
Seismic performance improvement of steel buildings by using zipper braces
Ters V çaprazlar merkezi çapraz sistemlerin bir tipini oluşturmaktadır. Bu tür sistemlerin deprem performansı çoğunlukla birinci kat çapraz elemanların basınçta burkulmasına bağlıdır. Genellikle, şiddetli depremler altında bu sistemlerde yük tekrar dağılımı yeterli şekilde gerçekleşmemektedir. Literatürde bu problemin çözümü için fermuar tipi çapraz kullanımı önerilmektedir. Sunulan bu çalışmada, fermuar çaprazların değişik deprem kuvvetlerine maruz 3, 6 ve 8 katlı çelik binaların deprem davranışına etkisi incelenmiştir. Örnek binalar her yönde üç eşit açıklığa ve aynı kat planına sahiptir. Bu nedenle analizlerde iki boyutlu modeller kullanılmıştır. Mevcut yapıların yapısal davranışlarının iyileştirilmesinde tek ve çift fermuar çapraz uygulaması yapılmıştır. Yapıların analizinde doğrusal olmayan statik ve dinamik analizler gerçekleştirilmiştir. Dinamik analizlerde 1994 Northridge, 1999 Hector Mine ve 1999 Chi-Chi deprem kayıtları kullanılmıştır. Yapı yüksekliği boyunca fermuar çaprazların kullanımının yapıların deprem davranışı üzerinde önemli etkisinin olduğu, ayrıca, çapraz kullanımı ile mevcut yapıların göreli kat ötelenmesi ve yerdeğiştirme taleplerinde azalmalar olduğu görülmüştür.
Effect of Rice Husk Powder content with different watercement ratios on rheological properties of cement-based grouts
It is appear that a lot of waste materials producted during industrial production in all over the world. There is a difficulty for storing and removing these products. Moreover, they cause pollution of the environment. One of the huge waste products is rice husk. Every year nearly 400 million tons of waste rice husk produced in the world. The rice husk has been used for different purposes such as a fuel in brick kilns, in furnaces, as an cleaning or polishing agent in metal and machine industry, in the manufacturing of building materials. In addition, rice husks themselves are a class A thermal insulating material because they are difficult to burn and less likely to allow moisture. Its ash is also replaced with cement as a cementitious material in concrete production In this study, feasibility of use of rice husk powder (RHP) as filler in cement grout was investigated. For this purpose rice husk was grinded to certain grain size and mixed with cement grouts at 4, 8, 12, 16 and 20% respectively. The mixture were prepared at different water to cement ratio (0.75, 1.00, 1.25 and 1.50). Effect of RHP on fluidity and rheological properties of the cement grout mixtures were studied. Test results showed that at water cement ratio (w/c) of 0.75, 1.00, 1.25 mixture showed shear thinning behavior. On the other hand, this behavior changes to shear thickening behavior at w/c = 1.50 at all RHP content. Experimental results indicated that this waste product can be utilized as filler in cement grout for geotechnical application such as filling large voids.
Flood hydrograph modeling studies by using GIS and HEC-HMS for Dakar, Senegal
Dakar, capital city of Senegal, has a hot semi-arid climate with a short rainy season. Dakar's rainy season lasts from July to October. Floods due to rainfall during this short period of time cause destruction in residential area and loss of life and properties. Actually, the main reason of destructions and losses is not exactly the heavy rains. Houses built in the floodplain and settlements in this area destroy the nature of the floodplain and cause disasters. To avoid disasters caused by flooding, conservation and mitigation studies and activities should be performed in natural floodplains. The main objective of this study is applying hydrological model to Dakar Basin and obtaining flood hydrographs of the basin. In the study, for determination of watershed boundaries and drainage lines, Geospatial Hydrologic Modeling Extension (HEC-GeoHMS); for hydrologic modeling studies, Hydrologic Engineering Center's Hydrologic Modeling System (HEC-HMS) software's were applied to Dakar Basin. According to the modeled hydrographs, results will try to be interpreted. Moreover, it is aimed to use obtained model parameters for Dakar's flood prevention studies.