Civil Engineering / İnşaat Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/13
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Article Citation - Scopus: 1Anomalous Crustal Structure Beneath the Örenli-Eğiller Depression Zone, Inferred From Magnetotelluric Studies, Western Anatolia, Türkiye(TÜBİTAK - Türkiye Bilimsel ve Teknolojik Araştırma Kurumu, 2024) Chandrasekharam, Dornadula; Raju, K.; Subba Rao, P.B.V.; Baba, AlperIn Türkiye, the prevalence of high radiogenic granites makes them ideal locations for initiating enhanced geothermal system (EGS) projects. One such occurrence of these granites is observed in the Kozak area of the Bergama region. To assess the energy potential of this site, a magnetotelluric (MT) survey was conducted, focusing on determining the depth distribution of the intrusive granite. The survey employed dimensionality analysis, utilizing Bahr skew and phase tensor analyses that denote a 2D subsurface nature up to 100 s and beyond that a 3D nature. In the present study, we interpreted MT data up to 100 s. The data collected, including rotated impedance tensors and tippers, were inverted using a nonlinear conjugate gradient algorithm integrated into the MT interpretation software of the WinG Link 2D inversion data modeling package. Multiple homogeneous half-space initial models were tested during the 2D inversion process. The findings indicate the existence of a midcrustal conductor associated with graphites and iron sulfides in the source region. This conductivity may be attributed to processes such as exsolution of metamorphic fluids, influx of mantle sources, or the entry of magmatic fluids through transcrustal fault zones. The findings indicate that the intrusive granite was emplaced along a NE–SW major fault, penetrating shallow crustal levels. The depth of this granite intrusion is determined to be 15 km, covering an outcrop area of 60 km². This detailed geological information allows a comprehensive assessment of the power-generating capacity of the intrusive granite. The results of this investigation contribute valuable insights for the development and optimization of Enhanced Geothermal System (EGS) projects in the region. © 2024, TUBITAK. All rights reserved.Article Citation - Scopus: 2Application of Endurance Time Method in Seismic Assessment of Rc Frames Designed by Direct Displacement-Based Procedure(Turkish Chamber of Civil Engineers, 2024) Karımzada, Nisar Ahmad; Shırkhanı, Amir; Aktaş, EnginThis paper addresses the Direct Displacement-Based Design (DDBD) approach of multi-story RC frame structures consistent with changes to design criteria between Turkish earthquake codes of TSC-2007 and TBEC-2018. The corresponding response modification factor (R) of structures designed based on the DDBD approach is also estimated in this research. The design base shear forces of both codes are compared considering different R factors and also with that of the DDBD approach. The results showed that the DDBD approach, as per TBEC-2018, provides RC frame structures with higher R values compared to the similar approach in accordance with TSC-2007. The Endurance Time (ET) method is a time history-based procedure for seismic assessment of structures under intensifying dynamic excitations aided to judge their performance at various intensity levels. Since, up to now, the ET method has not been considered to evaluate the performance of the structures designed by the DDBD approach, this paper addresses this issue. The ET performance curves of RC frames show that structures designed by the DDBD approach in accordance with TBEC-2018 exhibit higher Interstory Drift Ratios (IDRs) values than TSC-2007 at various hazard levels.Article Citation - Scopus: 3A Brief Overview on Geothermal Scaling(General Directorate of Mineral Research and Exploration (MTA), 2023) Isık, Tuğba; Baba, Alper; Chandrasekharam, Dornadula; Demir, Mustafa M.; Isık, Tuğba; Baba, Alper; Demir, Mustafa MuammerHot spring waters are rich in terms of minerals. Since there are dramatic changes in thermodynamic parameters in geothermal power plants, such as a decrease in temperature and pressure, severe precipitation occurs throughout the system components in an uncontrolled manner. There are three main chemistries in deposits: carbonates (mainly calcium carbonates), silicates (metal silicates), and sulphides (antimony sulphide-stibnite). Energy harvesting is remarkably reduced out of the insulating nature of the deposit. Various actions need to be taken to mitigate this undesirable issue of scaling in geothermal systems. Geothermal systems are in fact quite complex, and the composition of brine and, accordingly, the chemistry of the deposit are not identical. Therefore, each system should be studied individually, and a tailor-made remedy should be developed. In this overview, the types of deposits in terms of chemistry and the actions (pH modification or antiscalant dosing) that should be taken to reduce scaling are mentioned, and potential chemistries of antiscalants are given.Article Citation - WoS: 1Citation - Scopus: 2Geothermal Power Corridor-Connecting the Middle East Countries(Maden Tetkik ve Arama Genel Mudurlugu-mta, 2023) Chandrasekharam, DornadulaThe Middle East economy and life depend on imports, be it food, water, or energy, despite each country in the region having enormous energy resources to exploit and reduce dependency on countries outside the region and develop a socioeconomic model of regional cooperation and synergy. An estimated 371 TWh of electricity available from geothermal energy resources can be utilized by these countries to support basic needs and be free from food-energy-water imports by sharing their energy resources. The total amount of CO2 emissions from these countries is currently 945 x 106 kg, so these countries can further earn about 92 million euros from carbon savings, by using geothermal energy along this corridor. This amount can be utilized for augmenting the energy supply from geothermal sources. In this work, the available geothermal resources are evaluated, and suggestions are made how this energy can be best utilized for peaceful existence and cooperation in the region.Article Efficiency of Shear Studs Manufactured From Threaded Bars on the Punching Behavior of Flat Slabs(Golden Light Publishing, 2023) Saatçi, Selçuk; Saatcı, Selçuk; Yaşayanlar, YoncaPunching resistance in flat slab systems in reinforced concrete structures is often provided with drop panels or shear reinforcement around columns. Shear studs are effectively used in these structures as shear reinforcement. However, factory-made shear studs may not be available in all locations and small quantities for small projects. Therefore, cheap shear studs that can be manufactured from widely available materials in small quantities can be very useful in certain cases. In this study, shear studs manufactured from threaded bars, widely available in hardware stores, are used for providing punching resistance to flat slabs. Stud heads were formed with T-section nuts. Four slab specimens, two with shear studs and two without, were cast and tested under concentrated loads at their mid-point. The slabs had 2150×2150×150 mm dimensions and they were cast with two different longitudinal reinforcement ratios. Test results showed that manufactured shear studs significantly increased the load and deformation capacities of the slabs. Slabs with shear studs were able to show up to three times higher bending deformations and they were able to sustain up to 50% higher loads. The study has shown that these studs can be effectively used for punching strengthening purposes in flat plate systems or in other cases where punching resistance is needed.Article Citation - WoS: 6Citation - Scopus: 7Magnetotelluric Investigations Over Geothermal Provinces of India: an Overview(TÜBİTAK - Türkiye Bilimsel ve Teknolojik Araştırma Kurumu, 2023) Prabhala, Bhaskhara Venkata Subba Rao; Pachigolla, Venkata Vijaya Kumar; Chandrasekharam, Dornadula; Deshmukh, Vasu; Singh, Ajay KishoreMagnetotelluric (MT) and audio-magnetotelluric (AMT) studies are sensitive to the geothermal fluids filling the faults and/ or fracture zones of the geothermal system. In India, MT/AMT studies have been carried out in NW Himalayas, central, eastern, and western India. In other areas, detailed MT/AMT studies need to be expedited. This review paper presents the art of geothermal exploration in India by using MT/AMT techniques and identifies potential zones that can be exploited for power generation and direct application. Reservoir characteristics, carbon emissions reduction methods, and levelised cost factor are also discussed. © TÜBİTAK.Article Investigation of the Effect of Aggregate Specific Gravity on Optimum Bitumen Content of Hot Mix Asphalt(2022) Saltan, Mehmet; Karadağ, Öznur; Uz, Volkan Emre; Kaçaroğlu, Gizem; Gökalp, İslamIn this study, effect of aggregate specific gravity, which is directly related to origin of aggregates used in hot mix asphalt on optimum bitumen content, indirect tensile strength and tensile strength ratio of hot mix asphalt, was investigated. Specific gravity (SG) values of one kind of limestone aggregate were calculated according to Turkish Standard (TS), American Society for Testing and Materials (ASTM) and American Association of State Highway and Transportation Officials (AASHTO) standards, separately. Although one kind of limestone aggregate and 50/70 penetration grade bitumen are used in the mixtures, different values were obtained in terms of optimum bitumen content, indirect tensile strength and moisture sensitivity due to differences in the specific gravity values of the aggregates. Optimum bitumen contents were found by using TS, ASTM and AASHTO standards as 5.03%, 4.75% and 4.59%, respectively. According to the cost – benefit analysis, it can be said that changes in aggregate specific gravity values, which were calculated, based on different standards provide economic benefit. Overall, the results indicated that specific gravity values of one kind of limestone aggregate used in hot mix asphalt have significantly affected optimum bitumen content and indirect tensile strength of the mixtures.Article Citation - Scopus: 3Improvement of Strength Characteristics of a Highly Plastic Expansive Soil by Fly Ash(Sakarya University, 2022) Kodaz, G.; Demirci, H.E.; Pulat, H.F.Highly plastic expansive clays swell or shrink due to change in moisture content and they often have very low bearing capacity. Construction of engineering structures particularly pavements and lightweight buildings on problematic soils such as highly plastic expansive clays may create severe structural problems due to poor engineering properties of that kind of soil. This study focused on the influence of fly ash on strength properties of highly expansive clays which are problematic soils due to their undesirable engineering characteristics such as high plasticity index, liquid limit, swelling and shrinkage characteristics, and low bearing capacity. Atterberg’s limit tests and hydrometer tests were conducted to obtain consistency limits and grain-size distribution of the highly plastic expansive clay. Standard proctor tests for clay samples with different fly ash contents such as 10%, 15%, and 20% were performed to determine maximum dry densities and optimum water contents of the mixtures of clay and fly ash. The clay and fly ash mixtures were prepared at optimum water content and maximum dry density for unconfined compression strength (UCS) and California Bearing Ratio (CBR) tests. Effects of fly0ash content on the strength characteristics of a highly plastic expansive clay were investigated through unconfined compression and CBR tests. The experiment results showed that fly0ash is a promising additive to enhance strength characteristics of highly plastic expansive clays. An approximately 66% increase in UCS and CBR values was observed with the addition of 20% fly ash into the clay mixture in weight. © 2022, Sakarya University. All rights reserved.Article Citation - WoS: 10Citation - Scopus: 11Meteorological Drought Analysis for Helmand River Basin, Afghanistan(TMMOB İnşaat Mühendisleri Odası, 2022) Alami, Mohammad Musa; Tayfur, GökmenThis study evaluates drought at Lashkargah, Farah, Adraskan, and Gardandiwal stations in Helmand River Basin (HRB) in Afghanistan to determine appropriate drought indices for the basin. Thirty seven years of monthly recorded precipitation data from 1979 to 2015 are employed with different drought index (DI) methods which include the Standardized Precipitation Index (Normal-SPI, Log-SPI, and Gamma-SPI), the Percent of Normal (PN), and the Deciles. All the methods are applied to the annual long term precipitation data. The log-SPI and the gamma-SPI predict extreme drought conditions, whereas, the normal-SPI determines wet and less dry conditions. The results emphasize that the PN and the Deciles methods predict more drought years in comparison to the SPI methods. The Deciles method shows longer period of extreme and severe drought than other methods. The five methods indicate various drought intensities in 1985, 1987, 1994, 1997, 1999, 2000, 2001, 2002, 2003, and 2004 at all the stations. The extreme drought condition in 2001 at all the stations confirms to the recorded drought reports for the same region. It is noted that since the log-SPI and the gamma-SPI capture the historical extreme and severe drought periods successfully, these are recommended as the drought monitoring indices for Helmand River Basin.Article Citation - WoS: 1Citation - Scopus: 1Fragility Analysis of Wide-Beam Infill-Joist Block Rc Frames(Gazi Üniversitesi, 2022) Dönmez, Cemalettin; Karaarslan, Enes; Erberik, Murat AltuğPurpose: The purpose of the presented study is to develop fragility curves for the wide-beam infill-joist block reinforced concrete structures. Theory and Methods: Nonlinear time history analyses are performed for the set of selected ground motions. The performance levels are identified through pushover analysis and fragility curves are produced for ground motion parameters. Results: Fragility curves obtained for the wide-beam RC frames presents a different characteristic than the curves obtained for the conventional frames. Conclusion: Results show that wide-beam RC frame buildings are seismically more vulnerable than the conventional deep beam RC frame buildings based on structural models with similar properties. The possible reason seems to be low lateral stiffness of wide-beam frames that causes large lateral drift demands and therefore severe damage at the wide-beam column connections.
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