Performance Based Assessment of Steel Frame Structures by Different Material Models

Ercan Işık,Mesut Özdemir 한국강구조학회 2017 International Journal of Steel Structures Vol.17 No.3

Acceptable limit conditions for materials used in structures are one of the influential factors for design and evaluation of buildings. These limits are described using different material models. Material models can be generally defined by the stressstrain relationship. Stress-strain relationship varies based on the material. Mathematical models are used for describing the stress-strain relationship for any material. The material model takes a very important role in the seismic analysis of structures. The aim of this study is investigate of effects of steel models on structural performance of steel frame buildings. For this aim, pushover curves were obtained for three different steel models. It was determined that the pushover curves obtained according to three various steel models used in the study were consonant with each other.

Performance Analysis of Steel Structures with A3 Irregularities

Ercan Işık,Mesut Özdemir,İbrahim Baran Karaşin 한국강구조학회 2018 International Journal of Steel Structures Vol.18 No.3

Determination of the behaviour of structures during earthquakes is a very important engineering concern. Irregularities in the structure may lead to more damage imposed on it by weakening its defence mechanism during an earthquake. Some of these irregularities may be indentations or protrusions in the plan. Such irregular buildings may be encountered in practice because of various reasons. This study examined the state of irregularity by the A3 plan in the Turkish Building Earthquake Regulation of 2016. Four diff erent A3-type irregularity cases were considered. The building with no irregularities in its plan was taken as the reference building. The fi ve steel structures were compared by obtaining pushover curves for both the X and Y directions. Additionally, as a rapid assessment method, the Canada Seismic Screening Method was used in the study. Both in the rapid assessment method and from the pushover curves, it was determined that buildings without irregularities are safer. The study also allows a comparison among the earthquake performances of the structures using the rapid assessment method. It may be stated that there was an agreement between the two methods. This shows that the rapid assessment method may be used for steel structures. The importance of constructing structures that do not include irregularities is emphasized with the study. If one has to construct such structures, the defence mechanism of the structure should be strengthened by taking various measures.

Analysis of Technical Specification-based Disputes in Construction Industry

Ercan Erdis,Sitki Alper Ozdemir 대한토목학회 2013 KSCE JOURNAL OF CIVIL ENGINEERING Vol.17 No.7

This article covers the role of the standard and dynamic technical specification system for building structures in avoiding disputes between the employer and contractor, which is a ever-lasting problem in Turkey. For this purpose, the study was started with examining approximately 100 specification files and 32 court records on these issues. Afterwards, a survey was conducted among 58construction firms associated with the “Turkish Contractors Union” to identify the causes of technical specification related disputes and developing suggestions for possible resolutions. The survey results showed that these disputes generally arise from project characteristics and are mostly human oriented. It was concluded that establishing an institute consisting of experts in technical specifications, creating a standard and dynamic specification system, having quality guidelines, making judicial arrangements to shorten the judicial process, and information dissemination on related subjects through academic programs and judicial documents are important.

Microhardness and Morphologic Characteristics of Rapidly Solidified Al–12Si–8Ni–5Nd Alloy

Ercan Karaköse,Mustafa Keskin 대한금속·재료학회 2010 METALS AND MATERIALS International Vol.16 No.3

Al–Si–Ni–Nd alloys with a nominal composition of Al–12 wt.% Si–8 wt.% Ni–5 wt.% Nd alloy are prepared by a conventional casting (ingot) and melt spinning technique at different cooling rates (v). The effects of the rapid solidification rate on the microstructures and microhardness performances of the specimen alloys are investigated in detail. The results obtained by the XRD, SEM and DSC show that the ingot and melt spun alloys have a multiphase structure. When v is 5 m/s, the alloy consists of four phases namely α-Al,intermetallic Al3Ni, Al11Nd3, and fcc Si. The melt-spun ribbons are completely composed of α-Al and eutectic Si phases, and primary silicon is not observed when v increases to 20 m/s, 25 m/s, 30 m/s and 35 m/s. The XRD analysis indicated that the solubility of Si in the α-Al matrix increases greatly with the rapid solidification. The change in microhardness is discussed based on the microstructural observations. The microhardness values of the melt spun ribbons are about three times higher than those of ingot counterparts.

Measurement of Contrast Sensitivity in Patients with Behçet’s Disease without Ocular Involvement

Ercan Ozsoy 대한안과학회 2019 Korean Journal of Ophthalmology Vol.33 No.2

Purpose: To evaluate contrast sensitivity in patients with Behçet’s disease (BD) without ocular involvement. Methods: The study group was composed of 47 BD patients (20 to 50 years of age) who did not have ocularinvolvement. The control group was composed of 47 normal volunteers who were similar to the study group interms of age and gender. No participants in this study had any ocular or systemic pathologies except for BD. The contrast sensitivity measurements were performed using the Functional Acuity Contrast Test under photopicconditions, and the results were compared between the two groups. Results: The mean age of the BD patients and control subjects was 34.5 ± 9.7 and 33.2 ± 7.6 years, respectively. The mean disease duration of the BD patients was 5.5 ± 6.4 years. There was a statistically significantdecrease at five spatial frequencies (A, 1.5; B, 3; C, 6; D, 2; and E, 18 cycles per degree) in patients with BDcompared with control subjects (p < 0.001, p = 0.004, p = 0.002, p < 0.001, and p = 0.001, respectively). Conclusions: The contrast sensitivity of BD patients without ocular involvement was lower than that of the controlgroup. Further studies seem mandatory to confirm our results.

ON DEFERRED CESÀRO MEAN IN PARANORMED SPACES

Ercan, Sinan The Kangwon-Kyungki Mathematical Society 2021 한국수학논문집 Vol.29 No.1

The aim of the present study is to introduce the concepts of deferred statistical convergence, deferred statistical Cauchy sequence and deferred Cesàro summability in paranormed spaces. We investigate some properties of these concepts and some inclusion relations with examples.

Letter to the Editor : Posttraumatic Ectopic Nail: A Usual Manifestation and Treatment of an Unusual Anomaly

( Ercan Caliskan ),( Didem Dincer ),( Gurol Acikgoz ),( Erol Koc ) 대한피부과학회 2014 Annals of Dermatology Vol.26 No.6

Aortic Stiffness in Patients with Deep and Lobar Intracerebral Hemorrhage: Role of Antihypertensive Drugs and Statins

Ercan Varol,Mehmet Ozaydin 대한뇌졸중학회 2015 Journal of stroke Vol.17 No.1

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Microstructure Properties and Microhardness of Rapidly Solidified Al64Cu20Fe12Si4 Quasicrystal Alloy

Ercan Karaköse,Mustafa Keskin 대한금속·재료학회 2012 METALS AND MATERIALS International Vol.18 No.2

This paper presents differences in the microstructure and microhardness properties of conventional casting (ingot) and rapidly solidified Al64Cu20Fe12Si4 quasicrystal (QC) alloys. The phases present in the Al64Cu20Fe12Si4ingot alloy were determined to be icosahedral quasicrystalline (IQC) Ψ-Al65Cu20Fe15, cubic β-AlFe, tetragonal θ-Al2Cu, and monoclinic λ-A13Fe4 phases, whereas only IQC Ψ-Al65Cu20Fe15 and cubic β-AlFe phases were identified in the rapidly solidified alloy. The microhardness value of the melt spun alloy was measured to be approximately 790 kg/mm2. Microhardness increases with increasing solidification rates.

Observation of behavior of the Ahlat Gravestones (TURKEY) at seismic risk and their recognition by QR code

Ercan Işık,Barış Antep,Aydın Büyüksaraç,Mehmet Fatih Işık 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.72 No.5

Protection of cultural heritage and carrying it to the future are at the top of the significant topics of research and implementation in engineering in the 21st century. There are several historical structures in the district of Ahlat located in the east of Turkey on the Lake Van Basin that has harbored many civilizations. Some of such works are the gravestones that are found in the Ahlat Seljuk Cemetery, which is the oldest and largest cemetery in the district. This study firstly provides information about the Ahlat Seljuk Cemetery and the gravestones found in it. Observation-based structural analyses were carried out on these gravestones that are found in this area that are known to have belonged to different civilizations based on their physical and constructional characteristics. These stones were built out of Ahlat stone as single pieces. Information is provided on the damages that have occurred on the gravestones in time and their causes. In general, losses of mass, abrasions, separations, collapses and calcifications due to natural conditions, as well as vegetative formations, were observed in the gravestones. To provide an example of other gravestones within the context of the study, the gravestone that is known to belong to the person named Nureddin Ebu Hasan was selected. As a result of the modeling that was carried out for this gravestone by using the finite elements method, modal analyses were carried out. With these analyses, for the gravestone, period, effective mass participation rates and stress values were calculated. The stress values that were obtained in this study were compared to the material safety stress values that were obtained in previous studies. Additionally, QR code application was created for the gravestone that was selected as an example in the study, and information on this gravestone was transferred to an electronic environment. The QR code application includes different language options, visuals of the gravestone and information on the gravestone. The QR application was also supported with a video of the cemetery where the gravestone is located. With this application, access to information about gravestones will be possible by using tablets and smartphones. With a QR code to be created for each gravestone, these gravestones will obtain identity cards.