Civil Engineering / İnşaat Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/13
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Article Citation - WoS: 3Citation - Scopus: 4Effects of Steel Fiber Type and Ratio on the One-Way Bending Behavior of Hybrid Fiber Reinforced Concrete Thin Panels(Elsevier Sci Ltd, 2024) Saatci, Selcuk; Cetin, Fatma Sirin; Aloui, Sarra; Naseri, JamalullahPerformance of hybrid fiber reinforced concrete (HyFRC) determined through standardized material tests usually correlates well with the structural performance. However, for thin panels, this correlation may be disturbed due to the fiber orientation and small crack surfaces, and more detailed investigations are required. In this study, effects of steel fiber type and ratio on the one-way bending behavior of HyFRC thin panels was investigated through concrete mixes obtained by using three different steel fiber types and polyvinyl alcohol (PVA) fibers. 45 dog bone shaped, notched specimens were cast and tested under direct tension to investigate the direct tension behavior of used HyFRC. Nine panels of 2500 x 500 x 50 mm in dimension were tested under three-point bending, and nine panels of 1240 x 500 x 50 mm in dimension were tested under four-point bending. An in-verse analysis to obtain crack width-stress variation in three-and four-point bending specimens was also per-formed and behavior of steel fiber reinforced concrete specimens with and without PVA addition were compared. It was found that steel fiber type and ratio was consistently the dominant factor for all types of tests on HyFRC specimens. Addition of PVA fibers in HyFRC specimens either resulted in a similar or worse behavior for direct tension and three-point bending compared to their steel fiber only counterparts. Adverse effect of PVA fibers was more pronounced in three-point bending tests. On the other hand, PVA addition had a more positive effect in four-point bending tests. Inverse analyses performed on three-point bending tests revealed that stress levels develop between crack surfaces in these thin panels were significantly lower compared to direct tension stress levels. However, under four-point bending, these tensile stresses were closer to direct tension stresses, especially for specimens with shorter steel fibers. Loading conditions were found to be an effective factor in the behavior of HyFRC thin panels.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 Citation - WoS: 1Citation - Scopus: 1Proposals for Monitoring Current Conservation Condition of Historical Masonry Buildings: Matrone Church and Çardak Han Cases;(Istanbul University Press, 2020) Durmuşlar,F.; Ipekci,E.; Turan,M.H.; Aktaş,E.The aim of this study is to transfer the international developments related to the process of diagnosis and monitoring of historical masonry structures to the national area. The method chosen is to test the recommendations made at the international level on national cases and to discuss the results obtained by comparing them. A review of preliminary studies, on-site observations, measured surveys, material characterizations, mapping and visual analysis have been carried out. An examination of structural characteristics and observed failures have also been detailed. Related risks have been evaluated with criteria developed by taking into consideration condition classes defined in the UNI EN 16096, titled Conservation of Cultural Property - Condition Survey and Report of Built Cultural Heritage. According to the defined risks and classes, priorities of interventions were determined. Two historical masonry buildings which possess characteristics of different periods and present different damage types were selected: Matrone Church in Ildiri, Çeşme, Izmir and Çardak Han in Çardak, Denizli. The condition reports of the selected buildings have been prepared. The critical points in the condition reporting of historical masonry buildings were determined: accurate comprehension of the authentic structural characteristics and related failures have priority in maintaining historical masonry structures. Identification of condition class and risk assessment of each historic masonry building should be made in accordance with a standard specific to the cases of our country, but in line with the European standards and current developments in the field of architectural restoration. Thus, it will be possible to evaluate the conservation state of our masonry assets in comparison with each other. The content and priority of interventions can be well planned with the participation of the necessary disciplines. © 2020 The authors.Article Citation - WoS: 4Citation - Scopus: 5Dynamic Analysis of an Immersed Tunnel in Izmir;(Pontificia Universidad Catolica de Chile, Escuela de Construccion Civil, 2018) Egeli,I.; Gurbuz,C.The original design of the planned Izmir Bay Immersed Tube Tunnel, considered it to be a continuous subsea tunnel for the whole length of about 7.6 km. But this was later changed into having 2 shorter tubes of 2.7 km long each connected thru’ a 2.2 km long artificial island created in the middle of the bay from the excess dredged material, a concept which also reduces costs and increases efficiency. This island will serve as a venue for the 2025 Expo Exhibition, which Izmir city will apply to organize in the future. Reason for the research study was to provide a preliminary design, using a dynamic analysis, during the current pre-feasibility stage, of the immersed tunnel to show whether it can be built across the Izmir Bay. This paper takes into account the new alignment and presents the results of a 2-D dynamic analysis conducted of the prefabricated 100m long tunnel elements, sitting within a backfilled dredged ditch, dug after the recommended ground improvement was carried out. Analyses considered staged construction and the results showed that: Tunnel units and its surrounding soils inside the dredged ditch act together to provide a better earthquake response with a damping effect of the earthquake force; Tunnel units do not float to the sea surface, but continued to stay inside the dredged ditch and applied positive stresses to the foundations during the design earthquakes. As there was no floating, there was no need for anchoring the tunnel to ditch bottom; Tunnel units and immersion joints (made of specified strong elastomer material) continued to stay in compression longitudinally and provided a superb water-tightness level; There were no risky (un-tolerable) ground deformations during, after striking of the design earthquakes. Total vertical and differential displacements of the tunnel units and in the surrounding soils were all at acceptable levels; Concrete surface crack widths occurring in the tunnel units, during striking of the design earthquakes were also found to be allowable. Study results show that the tunnel elements can withstand Mw=7 short duration (<10 sec) or Mw=6 long duration (>10 sec) earthquakes without major damages to their structure © 2018. Revista de la Construccion. All rights reserved.