İnşaat Mühendisliği Bölümü Koleksiyonu

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https://hdl.handle.net/20.500.12428/2661

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Tek Boyutlu Zemin Büyütme Analizlerinde Transfer Fonksiyonunun Değiştirilmiş Sonlu Elemanlar Taşıma Matrisi Yöntemi ile Elde Edilmesi
(Afet ve Acil Durum Yonetimi Baskanligi (AFAD), 2021) Bilican, Öznur; Bozdoğan, Kanat Burak; Keskin, Erdinç
In this study, a method is proposed to obtain Transfer functions used in one-dimensional soil amplification analysis. Within the scope of the study, the Modified Finite Element Transfer Matrix (MFETM) method, which was used to find the soil fundamental period in the literature, was adapted to the problem of finding transfer functions used in soil amplification analysis. In the classical finite element method, the system matrix size that increases depending on the number of elements is independent of the number of elements in the MFETM method. At the end of the study, the suitability of the proposed method was shown on two examples. The examples discussed were solved using both the MFETM method presented in this study and the method in the literature, and the results were compared. A program was written in Scilab for the application of the presented method.
Stress-strain model for high-strength concrete tied columns under concentric compression
(Elsevier Ltd, 2021) Köksal, H.O.; Erdoğan, A.
Providing accurate constitutive stress–strain relationships for confined concrete can increase the reliability of the moment curvature (MC) analyses in the displacement-based seismic design of reinforced concrete (RC) columns. This paper presents a new stress–strain model for high-strength concrete (HSC) tied square columns which exhibit a more brittle behavior than normal strength concrete (NSC) members. Introducing the concept of least confined volume in the damage localization zone at the middle of the concrete core, a new approach is developed for the confinement stress distribution of lateral ties. In order to determine the lateral stresses acting on the vertical surfaces of the least confined volume, the effective confinement stresses are reduced considering the tie configuration. The peak strength and the ductility of the column should therefore be calculated for the confined concrete in this region. A concrete failure criterion applicable to multi-axial compression due to the reduced confinement stresses in two orthogonal directions, is then used to determine the ultimate strength of HSC columns. Moreover, plotting the compression meridian of the failure criterion, a simple and design-oriented formula is proposed for the ultimate strength of HSC tied columns. The validity of the proposed approach and the performances of two well-known analytical models are verified against the test results of eighty-six HSC columns from five different experimental studies for both the axial stress–strain behavior and the ultimate strength. Besides, the implementation of the concept of the reduced confinement stress in the Mander's model leads to a significant improvement in its capability of predicting the triaxial strength of HSC.
Hydrogeochemical Assessment of Groundwater for Drinking and Agricultural Use: A Case Study of Rural Areas of Alwar, Rajasthan
(Springer, 2021) Aggarwal, Ankur; Soni, Jigyasa; Sharma, Khyati; Sapra, Mohnish; Karaca, Öznur
Groundwater contributes substantially to the development of arid and semi-arid regions around the globe. The present study integrates groundwater quality and its suitability for drinking and irrigation around Alwar city of Rajasthan state, where agriculture is the major land use. The application for drinking was assessed by comparing the observed value with prescribed standards of WHO. Groundwater was found suitable for drinking at most of the locations. The suitability of groundwater for irrigation was determined by calculating ion-based ratios and comparing them against the suggested ratios and indices for agricultural quality. Suitability for irrigation was assessed against electrical conductivity (EC), percentage sodium (%Na), residual Na2CO3 (RSC), per cent soluble sodium (SSP), sodium adsorption ratio (SAR), Mg hazard and permeability index (PI) etc., and the quality was compromised for EC, %Na and Mg Hz. Since the soil was sandy, the groundwater was found suitable for irrigation over long-term use, with the only problem of magnesium hazard. Based on the different ratios of anions and cations, silicate weathering was observed to be regulating groundwater chemistry, and the groundwater belonged to mixed CaMgCl and CaHCO3− type based on Piper’s classification and relative abundance of ions. Further, meteoric genesis classification showed that the groundwater in the study region had direct base exchange and shallow meteoric water percolation. Presence of kaolinite and quartz minerals in soil confirmed that silicate weathering is the major process controlling groundwater chemistry.
Spatial and Seasonal Variability of Long-Term Sea Surface Temperature Trends in Aegean and Levantine Basins
(Springer, 2021) Saraçoğlu, Fevziye Ayça; Aydoğan, Burak; Ayat, Berna; Saraçoğlu, Kebir Emre
This study aims to estimate the spatial variability of the long-term trends of Sea Surface Temperature (SST) in the Eastern Mediterranean Sea including the Aegean Sea for 39 years between 1982 and 2020. Two datasets consisting of in-situ daily mean SSTs provided by the Turkish State Meteorological Service for the 12 stations located along the Aegean and Levantine coasts of Turkey and gridded daily mean Optimum Interpolation Sea Surface Temperature version 2.1 (OISSTv2.1) data obtained from the National Centers for Environmental Information (NCEI) of the United States National Oceanic and Atmospheric Administration (NOAA) are used for this aim. The trend of change in SST is computed using a non-parametric Theil-Sen estimator methodology. The significance of trends is computed using the Mann–Kendall test. As well as the long-term trends of monthly mean SST, the trends of monthly minimum and maximum SSTs are analyzed to reveal the long-term variations of extreme SSTs. It is concluded that there is a statistically significant upward trend within the study area. The annual basin-averaged upward trends of monthly mean, minimum, and maximum SSTs are estimated as 0.039 °C/year, 0.043 °C/year, and 0.037 °C/year, respectively. Coastal in-situ data present different characteristics for the Aegean Sea and the Levantine Basin. Aegean Sea stations show that the annual maximum SST has a higher rate of upward trend than the annual mean and minimum SSTs, while measurements from the Levantine Basin show minimum SST values increasing at a greater rate than both the annual means and maximums. Analysis of in-situ data at 12 stations provides statistically significant trends between 0.024 °C/year and 0.055 °C/year, 0.025 °C/year and 0.093 °C/year, and 0.031 °C/year and 0.071 °C/year for annual mean, annual minimum, and annual maximum SSTs, respectively. Seasonal analysis of the monthly mean SST trends shows that the highest upward trend occurs in August at the Dikili station (Aegean Sea) with a rate of 0.110 °C/year. SST in the study area is significantly affected by the Atlantic Multidecadal Oscillation (AMO), Eastern Atlantic (EA), and East Atlantic/West Russia (EA/WR) indices.
A Hand Method for Assessment of Maximum IDR and Displacement of RC Buildings
(Springer Science and Business Media Deutschland GmbH, 2023) Bozdoğan, Kanat Burak; Özturk, Duygu
Maximum displacement and the maximum interstorey drift ratio are the important factors for the measurement of the vulnerability of multistorey buildings. For this reason, in this paper a method was proposed to calculate the maximum displacement and maximum interstorey drift ratio (IDR) values. In this model, reinforced concrete multistorey structure was modeled as an equivalent flexural-shear frame. Maximum displacement and the maximum IDR were calculated according to the Equivalent Static Loads Method and The Response Spectrum Method using the continuum model and the results were tabulated. With the help of the obtained tables by this study, the maximum displacement and the maximum IDR of the regular multistorey structures can be calculated quickly and practically. The axial deformation of the vertical elements (columns and shear walls) were approximately considered in the study. The convergence of the presented method to the Finite Elements Method was investigated by two examples in the last part of the study.
Single and Multi Effects of Polycarboxylate Main and Side Chain Lengths on Setting Time, Viscosity, and Yield Stress of Cementitious Mixtures Containing Fly Ash
(American Society of Civil Engineers (ASCE), 2023) Altun, Muhammet Gökhan; Özen, Süleyman; Karakuzu, Kemal; Mardani, Ali; Ramyar, Kambiz
In this study, polycarboxylate polymers having different main chain lengths, side chain lengths, and main chain and side-chain lengths at constant molecular weight were synthesized. Cementitious mixtures with 0%, 15%, 30%, and 45% fly ash substitution levels were tested with polycarboxylate based admixtures (PCEs). As the main and side chain length of the PCE increased up to a certain value, regardless of the fly ash content, the fluidity of the mixtures was positively affected. However, after a certain length, both the electrostatic and steric effects of the PCE decreased, as the polymers intercalated and flocculated, adversely affecting the flow properties of the mixtures. Regardless of the PCE structure, the use of fly ash adversely affected the setting times and rheological properties of the mixtures.
Utilization possibilities of steel slag as backfill material in coastal structures
(Nature Research, 2023) Tozsin, Gülşen; Yonar, Fatih; Yücel, Onuralp; Dikbaş, Atilla
The aim of this study is to investigate the utilization possibilities of steel slags, basic oxygen furnace (BOF) and electric arc furnace (EAF) slags, as backfill material in coastal structures. Within the scope of the study, physical, mechanical and chemical properties of the steel slags were investigated and their potential to create environmental risks were evaluated. The results showed that soundness loss and filler content ratio were below the limit values for steel slags to be used as backfill material. It was determined that the density, porosity, water absorption and Los Angeles abrasion ratios of steel slags were generally higher than natural aggregates. In order to reach the California Bearing Ratio (CBR) limit (> 25%), the maximum particle size of the steel slag was reduced to 25 mm. In this particle size, CBR of the slag samples generally gave better results compared to the natural aggregate (38%), except for Kardemir and Asil samples. In addition, the concentration values of heavy metals (Cu, Cd, Cr, Pb, Ni, Zn, Hg and As) were below the limit values specified in the regulation. It is suggested that EAF slags should be aged for at least 6 months and BOF slags for at least 24 months in open air conditions before being used as backfill material in coastal structures after the maximum particle size is reduced to 25 mm.
A simplified model proposal for non-linear analysis of buildings
(Techno-Press, 2023) Halimi, Abdul Rahim; Bozdoğan, Kanat Burak
In this study, a method has been proposed for the static and dynamic nonlinear analysis of multi-storey buildings, which takes into account the contribution of axial deformations in vertical load-bearing elements, which are especially important in tall and narrow structures. Shear deformations on the shear walls were also taken into account in the study. The presented method takes into account the effects that are not considered in the fishbone and flexural-shear beam models developed in the literature. In the Fishbone model, only frame systems are modeled. In the flexural shear beam model developed for shear wall systems, shear deformations and axial deformations in the walls are neglected. Unlike the literature, with the model proposed in this study, both shear deformations in the walls and axial deformations in the columns and walls are taken into account. In the proposed model, multi-storey building is represented as a sandwich beam consisting of Timoshenko beams pieced together with a double-hinged beam. At each storey, the total moment capacities of the frame beams and the coupled beams in the coupled shear walls are represented as the equivalent shear capacity. On the other hand, The sums of individual columns and walls moment at the relevant floor level are represented as equivalent moment capacity at that floor level. At the end of the study, examples were solved to show the suitability of the proposed method in this study. The SAP2000 program is employed in analyses. In a conclusion, it is observed that among the solved examples, the proposed sandwich beam model gives good results. As can be seen from these results, it is seen that the presented method, especially in terms of base shear force, gives very close results to the detailed finite element method.
Application of differential transformation method for free vibration analysis of wind turbine
(Techno-Press, 2021) Bozdoğan, Kanat Burak; Maleki, Farshid Khosravi
In recent years, there has been a tendency towards renewable energy sources considering the damages caused by non-renewable energy resources to nature and humans. One of the renewable energy sources is wind and energy is obtained with the help of wind turbines. To determine the behavior of wind turbines under earthquake loads, dynamic characteristics are required. In this study, the differential transformation method is proposed to determine the free vibration analysis of wind turbines with a variable cross-section. The wind turbine is modeled as an equivalent variable continuous flexural beam and blade weight is considered as a point mass at the top of the structures. The differential equation representing the free vibration of the wind turbine is transformed into an algebraic equation with the help of differential transformation method and the angular frequencies and the mode shapes of the wind turbine are obtained by the help of the differential transformation method. In the study, a sample taken from the literature was solved with the presented method and the suitability of the method was investigated. The same wind turbine example also modeled by finite element modelling software, ABAQUS. Results of the finite element model and differential transformation method are compared with each other and the results are in good agreement.
Stability Analysis of Nanobeams by Modified Finite Element Transfer Matrix Method
(TUBITAK, 2021) Bozdoğan, Kanat Burak; Khosravi, Farshid
In this study, the modified finite element-transfer matrix method was adapted for nanobeam’s stability analysis. The nanobeam's stability equation was first established with the help of Euler beam theory. Using differential equation, the finite element matrix of the element was first deduced, followed by the Ricatti transfer matrix. The suitability of the present method was demonstrated using an example reported in the literature. In our reported method, the matrix dimensions are significantly reduced compared to the classical finite element method, and therefore the solution time is shortened. This method can be used mainly for the solution of multi-span and variable cross-section nanobeams.
An approach for dynamic analysis of steel plate shear wall systems
(Croatian Association of Civil Engineers, 2021) Güngör, Yasin; Bozdogan, Kanat Burak
In this paper, the Timoshenko beam model (continuous system model) is originally adapted for dynamic analysis of steel plate shear wall (SPSW) systems. Dynamic characteristics for the first three modes are found by solving differential equation of the equivalent Timoshenko beam model using the differential transformation method. Dynamic characteristics are tabulated for quick and practical calculation. With the help of the dynamic characteristics, the response spectrum analysis of such buildings is performed. Using the approach developed in this study, it is possible to calculate not only natural periods, but also the base shear force, maximum storey displacement, and maximum storey drift ratio. The differential transformation method is used in this study for solving the differential equation written according to the continuous system calculation model. To investigate the suitability of the method presented in the study, an example taken from the literature is solved and the results are evaluated. The results show that the method presented can be used in the preliminary design stage.
A simplified method for free vibration analysis of wall-frames considering soil structure interaction
(Techno-Press, 2021) Kara, Döndü; Bozdoğan, Kanat Burak; Keskin, Erdinç
In this study, a method for free vibration analysis of wall-frame systems built on weak soil is proposed. In the development of the method, the wall-frame system that constitutes the superstructure was modeled as flexural-shear beam. In the study, it is accepted that the soil layers are isotropic, homogeneous and elastic, and the waves are only vertical propagating shear waves. Based on this assumption, the soil layer below is modeled as an equivalent shear beam. Then the differential equation system that represented the behavior of the whole system was written for both regions in a separate way. Natural periods were obtained by solving the differential equations by employing boundary conditions. At the end of the study, two examples were solved and the suitability of the proposed method to the Finite Element Method was evaluated.

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