Civil Engineering / İnşaat Mühendisliği
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Article Citation - WoS: 3Citation - Scopus: 2Assessing the Spatial and Temporal Characteristics of Meteorological Drought in Afghanistan(Birkhauser, 2025) Tayfur, G.; Hayat, E.; Safari, M.J.S.Afghanistan is suffering from periodic events of drought, which has exacerbated in recent years due to extreme climate events in the region. Having an arid to semi-arid climate, the country faces significant challenges of water resources management, especially for irrigation as reliance on agriculture is cumbersome. This study is undertaken to characterize historical meteorological drought in Afghanistan to provide an insight on where and when meteorological drought events happened in different River Basins (RBs). The study mainly employs the gamma-Standardized Precipitation Index (gamma-SPI) to analyze historical meteorological droughts across Afghanistan from 1979 to 2019. Monthly precipitation data is obtained from the Ministry of Energy and Water (MEW) of Afghanistan, which is a combination of observed data from ground stations and gap-filled data by the MEW for the study period. Gridded gamma-SPI values are interpolated and mapped to visualize patterns of spatial drought across the entire country. The results indicate that countrywide extreme drought events occurred in 1999, 2000, 2001, 2010, 2016, 2017, and 2019, particularly affecting southern, western, and southwestern regions. Decreasing rainfall occurred in all five RBs, with the most considerable decline observed in the 1999–2008 period. The study reveals the increasing frequency and severity of meteorological droughts in Afghanistan. It also emphasizes on the vulnerability of agriculture and water sectors due to the drought events. The findings of the study suggest the need for better drought monitoring, preparedness, awareness, and adaptation of strategies to ensure water security and agricultural sustainability in the face of climate change. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2024.Article Citation - WoS: 61Citation - Scopus: 60Performance of Structures in İzmir After the Samos Island Earthquake(Springer, 2022) Yakut, A.; Sucuoǧlu, H.; Binici, B.; Canbay, E.; Dönmez, C.; Ilki, A.; Ay, B.Ö.The October 30, 2020 Earthquake caused unexpectedly significant damage in İzmir considering its distance to the city. This paper evaluates the recorded ground motions, summarizes the performance of structures affected from the earthquake with emphasis on the reasons of damage. A detailed damage assessment was carried out by the Earthquake Engineering Research Center of Middle East Technical University to compile data on the damage of RC and masonry buildings. It was observed that majority of the damage was concentrated in the Bayraklı district due to its peculiar soil properties where many 7–10 story mid-rise RC buildings suffered heavy damage and collapse. The level of amplified ground motions combined with deficiencies of apparently non-code compliant buildings exacerbated the damage. The main reasons of damage were mainly attributed to the presence of soft stories, lack of proper detailing, poor construction quality, presence of heavy overhangs, and hence significant lack of code-compliance in essence. The influence of infill walls on seismic performance of deficient and inadequate buildings was clearly seen in this earthquake. This paper also discusses seismic code requirements in effect and their influence on the observed building performance. The recorded ground motions were compared with the code spectra to evaluate the performance of the buildings. The code response spectra were found to be well above the recorded ground motion spectra at the sites where significant damage was observed. © 2021, The Author(s), under exclusive licence to Springer Nature B.V.Conference Object Citation - WoS: 3Salihli Granitoid, Menderes Massif, Western Anatolia: a Sustainable Clean Energy Source for Mitigating Co2 Emissions(2022) Chandrasekharam, Dornadula; Ayzit, Tolga; Baba, AlperTurkey has a great opportunity to promote renewable energy, which is produced from high heat-generating granitoids using EGS (Enhanced Geothermal Systems) technology. Exploiting the energy from the radiogenic granitoid will help the country save about 32211 million kg of CO2 from gas-based electricity power plants. In addition to the hydrothermal energy sources, energy from EGS will make the country free from energy deficit and provide sustainable power, water, and food. In the present paper, we assess the power generation capacity of Salihli granitoid (SG), with an outcropping area of about 100 km2 located within the western Anatolian plateau, and describe the technology involved in harnessing the heat from these granitoids. The Anatolian Plateau is known for extension tectonics and is explained by the westward tectonic escape and subduction rollback processes. The most prominent structures of western Anatolia are E-W and ENE-WSW trending graben and horst controlled by low and high-angle oblique to dip-slip normal faults, exposing the Menderes Massif. Magmatic activity in western Anatolia is mainly related to episodic-two stage extensional regime, where the early phase is characterized mainly by calc-alkaline Early-Middle Miocene felsic lavas and pyroclastic and the latter by late Miocene-Quaternary rift-related alkaline basaltic volcanism. The plutonic activity started during 12 to 15 Ma represented by SG. The heat generation capacity of the SG varies from 5.5 to 6.7 (µW/m3), while the heat flow values over SG range from 68 to 107 HF (mW/m2). These values are much higher compared to the global average crustal values.Conference Object Citation - Scopus: 3Seismic Performance of Cfrp Jacketed Sub-Standard Rc Columns Under High Axial Stress and Shear Demand(Springer, 2022) Demir, Merve Nur; Demir, Uğur; Demir, Cem; İlki, AlperIn the last decades, lessons learnt from the major earthquakes, that occurred in many countries, brought revisions in prevailing seismic design codes. As a consequence of this phenomenon, the current building stock in Turkey is mainly comprised of reinforced concrete (RC) buildings which were designed according to different seismic design codes. The presented paper is a component of a comprehensive investigation which containing three variables i) high axial load ratio defined as axial load divided by the axial capacity, ii) high shear demand defined as the ratio of shear demand at flexural yielding to shear resistance and iii) low transverse reinforcement ratio owing to large spacing among steel reinforcements. Thus, a total of four full-scale square RC columns comprised of i) one column designed to comply with the former Turkish Seismic Design Code (TSDC, 1975) and ii) three columns which are not compliant to any design codes (referred as sub-standard), were tested under high axial load ratio, 0.4 for code-conforming and 0.75 for sub-standard columns, combined with reversed cyclic lateral loading. The columns were also designed to have high shear demand in the order of 0.62 and 0.80 for bare sub-standard according to ACI 318 (2019) and TBEC (2018) design codes as sometimes observed in existing sub-standard structures. In addition to that, the ratio of shear demand for the code-conforming column is calculated 0.43 and 0.50 as per design codes, respectively. Besides, the ratio of transverse reinforcement area to the minimum required transverse reinforcement area was 0.19 and 0.77 for sub-standard columns according to ACI 318 (2019) and TBEC (2018), respectively. For the code-conforming column, the aforementioned ratio was 0.57 and 1.32 for both design codes, in the same manner. One of the sub-standard columns was kept as a reference column while the other two of them have been externally jacketed with one layer or two layers of carbon fiber-reinforced polymer (CFRP) sheets. Test results pointed out that the confinement provided by CFRP jacketing has remarkably improved the performance of seismically-deficient RC columns subjected to high axial compression under high shear demand in terms of lateral load capacity and ductility. The experimental results were also supplemented with theoretical work to evaluate the effects of CFRP jacketing on the seismic behavior of sub-standard RC columns.Conference Object Citation - WoS: 1Citation - Scopus: 2Seismic Performance of Substandard Rc Columns Retrofitted With Sprayed Gfrm(Springer, 2022) Kian, Nima; Demir, Uğur; Demir, Cem; Maraşlı, Muhammed; İlki, AlperThere is a myriad amount of substandard reinforced concrete (RC) buildings in developing countries that do not comply with the requirements and instructions of the current building design codes. In particular, columns in these substandard buildings demonstrate unsatisfactory and undesired behavior against lateral loads, mainly due to low concrete compressive strength and poor reinforcement detailing. The problem is exacerbated when the axial load ratio (ratio of applied axial load to the axial load capacity) and/or the shear ratio (ratio of shear force corresponding to moment capacity (Ve) to the shear capacity (Vr)) is/are high, leading to brittle failure modes. In this study, three full-scale substandard RC columns subjected to high axial load ratio of 0.75 were tested under constant axial load combined with reversed cyclic lateral displacements. Shear ratio (Ve/Vr) of the substandard columns were 0.75 and 0.82 according to ACI 318-19 (ACI 318 (2019) Building Code Requirements for Structural Concrete. American Concrete Institute, Farmington Hills, MI, USA) and (Turkish Building Earthquake Code (Turkish Building Earthquake Code (TBEC) (2018) Disaster & Emergency Management Authority, Ankara, Turkey), respectively. According to the TBEC (Turkish Building Earthquake Code (TBEC) (2018) Disaster & Emergency Management Authority, Ankara, Turkey), columns had a high Ve/(fctmbd) ratio of 1.12, where, fctm, b, and d are the direct tensile strength of concrete, width of the cross-section, and effective depth of the section. The ratio of transverse reinforcement to minimum required transverse reinforcement according to the ACI 318-19 (ACI 318 (2019) Building Code Requirements for Structural Concrete. American Concrete Institute, Farmington Hills, MI, USA) and TBEC (Turkish Building Earthquake Code (TBEC) (2018) Disaster & Emergency Management Authority, Ankara, Turkey) was 0.19 and 0.77, respectively. Two of the columns were retrofitted with an innovative, cost-effective, and easily-applicable strengthening method, through external jacketing with sprayed glass fiber reinforced mortar (GFRM) of different characteristics. The remaining column was tested as the reference specimen to evaluate the efficiency of the strengthening method. The test results demonstrated the extremely poor performance of the reference substandard column as well as the remarkable lateral load capacity and ductility improvement provided by the adopted novel strengthening approach.Conference Object Experimental Investigation of the Stabilization Performance of Geogrids for Unpaved Roads with Low Bearing Capacity Subgrade(Springer International Publishing AG, 2022) Gokova, Suleyman; Saltan, Mehmet; Terzi, Serdal; Tutumluer, Erol; Uz, Volkan Emre; Karasahin, MustafaIn this study, laboratory experiments were carried out on real sized samples to investigate the reinforcement performance of geogrids in highway pavements constructed on low bearing capacity subgrade (California Bearing Ratio, CBR = 3%). In all prepared samples, Hot Mix Asphalt (HMA) layer was not applied. A moving wheel load was applied with Accelerated Pavement Tester (APT) device on representative pavement samples with and without geogrids. Two types of geogrids were used to construct the pavement sample configurations. Resistance to plastic (permanent) deformation was recorded as a performance indicator to compare structural performance trends of the pavement samples. For this objective, surface deformations were measured after certain wheel load repetitions. Rut depths have been calculated from surface profiles measured with a laser profiler and were plotted versus number of load repetitions. As a result of this study, the use of geogrid over soft subgrade with lowCBR values has been shown to extend the life of the pavement by reducing the rut depth.Article Citation - WoS: 13Citation - Scopus: 14Soil Erosion Model Tested on Experimental Data of a Laboratory Flume With a Pre-Existing Rill(Elsevier Ltd., 2020) Aksoy, Hafzullah; Gedikli, Abdullah; Yılmaz, Murat; Eriş, Ebru; Ünal, N. Erdem; Yoon, Jaeyoung; Tayfur, GökmenPrediction of sediment discharge transported within flow is strongly needed in order to provide measures for a well-established erosion control and water quality management practice. Initiated by runoff generation and erosion processes sediment transport is influenced by microtopography over hillslopes of hydrological watersheds. Consideration of microtopography provides more accurate results. In this study, a process-based two-dimensional rainfall-runoff mathematical model is coupled with erosion and sediment transport component. Both the rainfall-runoff and sediment transport components make simulations in rills and over interrill areas of a bare hillslope. Models at such fine resolution are rarely verified due to the complexity of rills and interrill areas. The model was applied on a data set compiled from laboratory experiments. Erosion flume was filled with granular sand to replace a bare soil. A longitudinal rill and an interrill area were pre-formed over the soil in the flume before the simulated rainfall exerted on. The flume was given both longitudinal and lateral slopes. The simulated rainfall was changed between 45 mm/h and 105 mm/h and exerted on granular uniform fine and medium sand in the erosion flume with longitudinal and lateral slopes both changing from 5% to 20%. Calibration of the model shows that it is able to produce good results in terms of sedigraphs, which suggest also that the model might be considered an important step to verify and improve watershed scale erosion and sediment transport models.Conference Object A Boundary Element Method for Axisymmetric Elastodynamic Analysis(John Wiley and Sons Inc., 1996) Özkan, Gonca; Mengi, YalçınA new numerical method is proposed for the boundary element analysis of axisymmetric bodies. The method is based on complex Fourier series expansion of boundary quantities in circumferential direction, which reduced the boundary element equation to an integral equation in (r-z) plane involving the Fourier coefficients of boundary quantities, where r and z are the coordinates of the r theta z cylindrical coordinate system. The kernels appearing in these integral equations can be computed effectively by discrete Fourier transform formulas together with the fast Fourier transform (FFT) algorithm, and the integral equations (r-z) plane can be solved by Gaussian quadrature, which establishes the Fourier coefficients associated with boundary quantities. The Fourier transform solution can then be inverted into r theta z space by using again discrete Fourier transform formulas together with FFT algorithm. In this paper, we present the formulation of the proposed method which is outlined above. A comparison is given between the existent methods in literature and our method, which shows that the use of FFT algorithm for the integrations in circumferential direction provides considerable saving in computer time.Conference Object Upscaling Surface Flow Equations Depending Upon Data Availability at Different Scales(Springer Verlag, 2003) Tayfur, GökmenSt. Venant equations, which are used to model sheet flows, are point-scale, depth-averaged equations, requiring data on model parameters at a very fine scale. When data are available at the scale of a hillslope transect, the point equations need to be upscaled to conserve the mass and momentum at that scale, Hillslope-scale upscaled model must be developed if data are available at that scale. The performance of the three models applied to simulate flows from non-rilled surfaces revealed that the hillslope-scale upscaled model performs as good as the point-scale model though it uses far less data. The transectionally-upscaled model slightly underestimates the observed data.Conference Object Citation - WoS: 1Effect of Water Source on Human Health: a Case Study From Biga Peninsula, Turkey(2009) Baba, Alper; Gündüz, OrhanThe concentrations of certain elements including arsenic (As), fluoride (F) and aluminum (AI) were measured in groundwater in the different part of Biga Peninsula which is located in the western parts of Turkey. The concentration values of As and AI in groundwater ranged between 10-40 ppb, 0.5-0.8 ppm and 1-11.5 ppm, respectively, in this region. Al values exceed the Turkish drinking water standard value of 0.2 ppm. Furthermore, As concentration in water from alteration zones exceed the drinking water standard value of 10 ppb. Based on this background, this study was intended to investigate the source of these heavy metals and its neurotoxin effects on human health as many people living in this region have undergone medical treatment, which are believed to be related to the quality of water resources originating from densely altered volcanic rocks.