Civil Engineering / İnşaat Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/13
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Article Citation - WoS: 44Citation - Scopus: 47Predicting Flood Plain Inundation for Natural Channels Having No Upstream Gauged Stations(IWA Publishing, 2019) Kaya, C. Melisa; Tayfur, Gökmen; Güngör, OğuzFlow hydrographs are one of the most important key elements for flood modelling. They are recorded as time series; however, they are not available in most developing countries due to lack of gauged stations. This study presents a flood modelling method for rivers having no upstream gauged stations. The modelling procedure involves three steps: (1) predicting upstream hydrograph by the reverse flood routing method which requires information about channel geometric characteristics, downstream flow stage and downstream flow hydrographs; (2) modelling flood wave spreading using HEC-RAS. The hydrograph predicted by the reverse flood routing in the first step becomes an inflow for the HEC-RAS model; (3) delineating the flood-risk areas by overlapping the Geographical Information System (GIS)-based flood maps produced by the HEC-RAS to the related orthophoto images. The developed model is applied to Guneysu Basin in Rize Province in Eastern Black Sea Region of Turkey. The model-produced flood map is compared to the observed one with success.Article Citation - WoS: 3Citation - Scopus: 3Magnetically Driven Foldable Shell Type Swimmers at Stokes Flow(Springer, 2019) Özdemir, İzzetThis paper focuses on the interaction of low Reynolds number (Re) flows and thin shell type deformable structures in the context of flexible body locomotion and addresses the coupled field problem through a numerical solution framework. The thin structure is discretized by enhanced three-node finite elements and coupled with boundary element based treatment of Stokes flow in a monolithic manner. The locomotion is triggered and driven by an external magnetic field that generates displacement dependent body couples over the magnetically sensitive parts of the flexible structure. A particular novelty of the paper is the use of internal hinges through which very large rotations and structural deformations can be combined in an efficient way. Using this concept; new, on the fly locomotion direction reversal mechanisms can be generated as demonstrated by the foldable bi-directional swimmer.Article Two dimensional bed deformation model in turbulent streams(Taylor & Francis, 2019) Gharehbaghi, Amin; Kaya, Birol; Tayfur, GökmenA coupled model is developed to simulate two dimensional water surface profile, suspended sediment load and bed deformation in unsteady open channels. The hydrodynamical component employs the two dimensional shallow water equations to obtain the hydraulic variables. These, in turn, are used in the morphdynamical component to determine the bed deformation. For the turbulence variables; two turbulence models are supervened to the governing equations. Triangular meshes were developed to discretize the domain of open channel. In order to discretize the governing equations, the explicit finite volume method is used by the total variation diminishing (TVD) schemes. The performance of the developed model is compared to that of the Flow3D software. The comparison results are in good agreement.Article Citation - WoS: 33Citation - Scopus: 37Trend Analysis of Temperature and Precipitation in Trarza Region of Mauritania(IWA Publishing, 2019) Yacoub, Ely; Tayfur, GökmenTrend analysis of annual temperature and precipitation time series data collected from three stations (Boutilimit (station 1), Nouakchott (station 2) and Rosso (station 3)) has been used to detect the impacts of climate change on water resources in Trarza region, Mauritania. The Mann-Kendall, the Spearman's rho, and the Sen trend test were used for the trend identification. Pettitt's test was used to detect the change point of the series while the Theil-Sen approach was used to estimate the magnitude of the slope in the series. For precipitation, two stations (1 and 3) indicated statistically significant increase in trends. In the case of temperature, almost all the stations show statistically significant increasing trends in the maximum, minimum, and average temperatures. The magnitude of precipitation detected by the Theil-Sen test for stations 1 and 3, respectively, was found to be at the rate of 2.93 and 3.35 mm/year at 5% significance level. The magnitude trend of temperature detected by the Theil-Sen approach was found to be at the rate of 0.2-0.4 degrees C per decade for almost all the stations. The change points of temperature trends detected by Pettitt test are found to be in the same year (1995) for all the stations.Article Citation - WoS: 4Citation - Scopus: 4Inelastic Ultimate Load Analysis of Steel Frames Considering Lateral Torsional Buckling Under Distributed Loads(Budapest University of Technology and Economics, 2019) Seçer, Mutlu; Uzun, Ertuğrul TürkerContemporary structural design approaches necessitates ways to determine realistic behavior of structures. For this purpose, inelastic ultimate load analysis methods are used widely since strength and stability of whole structure can be represented. In this study, a numerical method is proposed for determining inelastic ultimate load capacity of steel frames considering lateral torsional buckling behavior under distributed loads. In the analyses, inelastic material behavior, second-order effects and residual stresses of the structural frame system and its members are taken into account. Additionally, lateral torsional buckling behavior is considered in the analysis using finite difference method and it is used for determining the structural load carrying capacity of steel frames. Consequently, the problem associated with flexural capacity decreases due to lateral torsional buckling is precisely considered in the load increment steps of inelastic ultimate load analysis. In order to validate the proposed method, numerical examples from the literature are calculated considering the proposed method, AISC 360-16 design specification equations and approaches from the literature. Results of the numerical examples show that lateral torsional buckling is a key issue in determining structural load carrying capacity. Thus, proposed analysis method is shown to be an ef.cient and consistent tool for inelastic ultimate load analysis.Article Construction Techniques of Hayat Houses: Two Case Studies in the Vicinity of Izmir(American Society of Civil Engineers (ASCE), 2019) Turan, Mine; Aktaş, Engin; Mamaklı, Fatma Sezgi; Kaplan, ZişanThis study aims to contribute to the analytic studies on constructional aspects of the hayat house typology with an eye on its historical evolution for conservation purposes. The method used included a review of the surviving examples of the typology in Izmir and its vicinity and the selection of two intact examples whose structural components are legible: one from the earliest period and the other from the latest period. The examples selected are Kerimaga Konagi in Birgi, odemis, Izmir and a house in Kirkagac, Soma, Manisa. The early example (probably eighteenth century, constructed over the remains of an older house) sustains the traditional box system in its wooden upper story that integrates with the roof. The provision of level differences on the upper floor, the traditional relationship of the sitting level-window design, and masonry base are its authentic features. The late example (probably early twentieth century) presents signs of modernization, such as the establishment of a systematic wooden roof and wall frames in relation to each other, lack of diagonals in the perpendicular wall frame, avoidance of projections, and relatively elongated windows placed at higher positions.Article Citation - WoS: 6Citation - Scopus: 4Conservation-Aimed Evaluation of a Historical Aqueduct in Izmir(American Society of Civil Engineers (ASCE), 2019) Mamaklı, Fatma Sezgi; Turan, Mine; Aktaş, Engin; Vardaroğlu, MustafaThe seventeenth century was the era in which Izmir became an international commercial center in the eastern Mediterranean. The vizier of the era, Koprulu Fazil Ahmet Pasa, noticed the scarcity of potable water in relation with the increasing population at the center of this harbor city and ordered the construction of an aqueduct on Melez Valley. The Veziraga Aqueduct was constructed in 1674. This article aims to identify historical, architectural, and structural characteristics of the Veziraga Aqueduct so that its heritage values and conservations problems can be understood. The geographical and historical characteristics of the Veziraga Aqueduct are described by taking the effects of site and the sociocultural situation of city into consideration. The architectural characteristics of the aqueduct are prepared by using the site survey data to reveal the current condition and find out the original state. Seismic behavior of the aqueduct is investigated by using two approaches: analytical equivalent static analysis and finite-element analysis. The historical, architectural, and structural characteristics of the Veziraga Aqueduct prove its historical, documentary, and aesthetic values.Article Citation - WoS: 15Citation - Scopus: 18Extreme Value Statistics of Wind Speed and Wave Height of the Marmara Sea Based on Combined Radar Altimeter Data(Elsevier, 2019) Özbahçeci, BergüzarBoth reliable and long-term wind and wave data are necessary for the design of coastal and offshore structures. Due to lack of sufficient in-situ measurement data, modeling data have been used in the limited number of wind and wave climate studies of the Marmara Sea. Satellites equipped with instruments capable of observing marine surface wind and ocean waves like Radar Altimeter can be another source for the long term wind and wave climate of the Marmara Sea. In this study, for the first time, the altimeter wind speed and the significant wave height data from different satellite missions are attempted to use in the climate and extreme value analysis of the Marmara Sea. Altimeter wind speeds and significant wave heights are compared with the in-situ measurements and it is found that while the altimeter wind speed agrees with the measurement data, the significant wave height data should be calibrated. After the calibration of the altimeter data and the inter-calibrations of earlier satellite missions, 27 years of altimeter wind speed and wave height data are obtained to use in extreme value analysis. The wind speed and the significant wave height values corresponding to various return periods are determined as a result of extreme value statistics and those values are compared with the results of the measurements and previous studies. Consistent extreme values computed in the current study indicate that the combined radar altimeter data can be used in the wind and the wave climate calculations and the extreme value analysis of the Marmara Sea. © 2019 COSPARArticle Citation - WoS: 16Citation - Scopus: 20Groundwater Recharge Estimation Using Hydrus 1d Model in Alaşehir Sub-Basin of Gediz Basin in Turkey(Springer Verlag, 2019) Tonkul, Serhat; Baba, Alper; Şimşek, Celalettin; Durukan, Seda; Demirkesen, Ali Can; Tayfur, GökmenGediz Basin, located in the western part of Turkey constituting 2% land of the country, has an important groundwater potential in the area. Alasehir sub-basin, located in the southeast of the Gediz Basin and subject to the extensive withdrawal for the irrigation, constitutes the study area. Natural recharge to the sub-basin due to precipitation is numerically investigated in this study. For this purpose, 25 research wells, whose depths range from 20 to 50 m, were drilled to observe the recharge and collect the necessary field data for the numerical model. Meteorological data were collected from 3 weather stations installed in the study area. The numerical model HYDRUS was calibrated using the field water content data. Soil characterization was done on the core samples; the aquifer characterization was performed, and the alluvial aquifer recharge due to precipitation was calculated. As a result, the computed recharge value ranges from 21.78 to 68.52 mm, with an average value of 43.09 mm. According to the numerical model, this amount of recharge corresponds to 10% of the amount of annual rainfall.Article Citation - WoS: 72Citation - Scopus: 79Artificial Neural Networks for Estimating Daily Total Suspended Sediment in Natural Streams(IWA Publishing, 2006) Tayfur, Gökmen; Güldal, VeyselEstimates of sediment loads in natural streams are required for a wide spectrum of water resources engineering problems from optimal reservoir design to water quality in lakes. Suspended sediment constitutes 75-95% of the total load. The nonlinear problem of suspended sediment estimation requires a nonlinear model. An artificial neural network (ANN) model has been developed to predict daily total suspended sediment (TSS) in rivers. The model is constructed as a three-layer feedforward network using the back-propagation algorithm as a training tool. The model predicts TSS rates using precipitation (P) data as input. For network training and testing 240 sets of data sets were used. The model successfully predicted daily TSS loads using the present and past 4 days precipitation data in the input vector with R2 = 0.91 and MAE = 34.22 mg/L. The performance of the model was also tested against the most recently developed non-linear black box model based upon two-dimensional unit sediment graph theory (2D-USGT). The comparison of results revealed that the ANN has a significantly better performance than the 2D-USGT. Investigation results revealed that the ANN model requires a period of more than 75 d of measured P-TSS data for training the model for satisfactory TSS estimation. The statistical parameter range (xmin - xmax) plays a major role for optimal partitioning of data into training and testing sets. Both sets should have comparable values for the range parameter.