Geometric and Material Nonlinear Analysis of Three-dimensional Steel Frames

Turgay Cosgun1,Baris Sayin 한국강구조학회 2014 International Journal of Steel Structures Vol.14 No.1

Results obtained through theoretical and empirical studies which examined the nonlinear behaviour of construction membersenabled us to characterize the behaviour of construction systems under external effects more closely. The calculation methodsthat took into consideration the nonlinear behaviour of the construction members and the nonlinear effects of their geometricalvariations had to be developed in order to evaluate these phenomena and to design structures according to their collapse loadprinciple. In the presented study, a computer program was developed for the characterization of structural systems by takinginto consideration the nonlinear conditions of material behaviours under increasing loads and by considering the second-ordereffects. A matrix-replacement method was used as the basis for developing the program, which takes into consideration theeffects of axial forces on the stiffness of the member by using the stability functions and the effects of plastic hinges bysystematically changing the stiffness matrix in each occurrence of the plastic hinges. In the study, based on the results obtainedfrom the examples, which were solved by the developed program, it was identified that the program could yield rapid andreliable results depending on the user-defined values (number of nodes, error limit for the iteration) and it is observed that theresults are consistent with the literature. The obtained results in this study have contributed to capability of converting twodimensional analyses to three-dimensional analysis of stability functions developed.

A method for the non-linear and failure load analysis of reinforced concrete frames

Turgay Cosgun1,Baris Sayin 사단법인 한국계산역학회 2014 Computers and Concrete, An International Journal Vol.14 No.1

Modern trend in structural design is to use smaller elements in order to ensure several purposes such as economy, functionality and aesthetic in appearance. However, because of decreasing rigidity of the structural elements, the system displacements increases and displacements become an important subject in this kind of structures takes into account both geometrical changes and the carrying capacity of the material after linear-elastic boundary. In this study, a method is proposed to calculate the failure loads and to analyse the reinforced concrete space frame systems. The numerical examples gathered from the literature survey are solved with this method utilising the prepared computer program and the comparable results are presented. The results show that the method is sufficiently accurate.

Evaluation of Invasive and Noninvasive Methods for the Diagnosis of Helicobacter Pylori Infection

Cosgun, Yasemin,Yildirim, Abdullah,Yucel, Mihriban,Karakoc, Ayse Esra,Koca, Gokhan,Gonultas, Alpaslan,Gursoy, Gul,Ustun, Huseyin,Korkmaz, Meliha Asian Pacific Journal of Cancer Prevention 2016 Asian Pacific journal of cancer prevention Vol.17 No.12

Objective: The present study was conducted to evaluate invasive and noninvasive diagnostic methods for detection of Helicobacter pylori (H. pylori) in patients admitted with dyspeptic complaints and to compare sensitivities and specificities. Method: Sets of four gastric biopsy specimens were obtained from a total of 126 patients included in the study. The presence of H. pylori was determined by invasive tests including culture, rapid urease test, polymerase chain reaction (PCR) and histopathology. Among noninvasive tests, urea breath test, serological tests and enzyme-linked immunosorbent assay (ELISA) were performed. Results: H. pylori was isolated in 79 (62.7%) gastric biopsy cultures, whereas positivity was concluded for 105 (83.3%) patients by rapid urease test, for 106 (84.1%) by PCR, for 110 (87.3%) by histopathology, for 119 (94.4%) by urea breath test, and for 107 (84.9%) by ELISA. In the present study, the culture findings and histopathological examination findings were accepted as gold standard. According to the gold standard, urea breath test had the highest sensitivity (96.5%) and the lowest specificity (30%), whereas culture and histopathology had the highest specificities (100%). Conclusion: The use of PCR invasively with gastric biopsy samples yielded parallel results with the gold standard. PCR can be recommended for routine use in the diagnosis of H. pylori.

Effect of biofilm formation, and biocorrosion on denture base fractures

Erdal Cosgun,Simel Ayyildiz,Gulay Uzun,Alper Ergin,Cem Sahin 대한치과보철학회 2013 The Journal of Advanced Prosthodontics Vol.5 No.2

PURPOSE The aim of this study was to investigate the destructive effects of biofilm formation and/or biocorrosive activity of 6 different oral microorganisms. MATERIALS AND METHODS Three different heat polymerized acrylic resins (Ivocap Plus, Lucitone 550, QC 20) were used to prepare three different types of samples. Type "A" samples with "V" type notch was used to measure the fracture strength, "B" type to evaluate the surfaces with scanning electron microscopy and "C" type for quantitative biofilm assay. Development and calculation of biofilm covered surfaces on denture base materials were accomplished by SEM and quantitative biofilm assay. According to normality assumptions ANOVA or Kruskal-Wallis was selected for statistical analysis (α=0.05). RESULTS Significant differences were obtained among the adhesion potential of 6 different microorganisms and there were significant differences among their adhesion onto 3 different denture base materials. Compared to the control groups after contamination with the microorganisms, the three point bending test values of denture base materials decreased significantly (P<.05); microorganisms diffused at least 52% of the denture base surface. The highest median quantitative biofilm value within all the denture base materials was obtained with P. aeruginosa on Lucitone 550. The type of denture base material did not alter the diffusion potential of the microorganisms significantly (P>.05). CONCLUSION All the tested microorganisms had destructive effect over the structure and composition of the denture base materials.

Finite element analysis of RC walls with different geometries under impact loading

Metin Husem,Suleyman I. Cosgun,Hasan Sesli 사단법인 한국계산역학회 2018 Computers and Concrete, An International Journal Vol.21 No.5

Today, buildings are exposed to the effects such as explosion and impact loads. Usually, explosion and impact loads that act on the buildings such as nuclear power plants, airports, defense industry and military facilities, can occur occasionally on the normal buildings because of some reasons like drop weight impacts, natural gas system explosions, and terrorist attacks. Therefore, it has become important to examine the behavior of reinforced concrete (RC) structures under impact loading. Development of computational mechanics has facilitated the modeling of such load conditions. In this study, three kinds of RC walls that have different geometric forms (square, ellipse, and circle) and used in guardhouses with same usage area were modeled with Abaqus finite element software. The three configurations were subjected to the same impact energy to determine the geometric form that gives the best behavior under the impact loading. As a result of the analyses, the transverse impact forces and failure modes of RC walls under impact loading were obtained. Circular formed (CF) reinforced concrete wall which has same impact resistance in each direction had more advantages. Nonetheless, in the case of the impact loading occurring in the major axis direction of the ellipse (EF-1), the elliptical formed reinforced concrete wall has higher impact resistance.

Experimental and numerical investigations on reinforcement arrangements in RC deep beams

Husem, Metin,Yilmaz, Mehmet,Cosgun, Suleyman I. Techno-Press 2022 Advances in concrete construction Vol.13 No.3

Reinforced concrete (RC) deep beams are critical structural elements used in offshore pile caps, rectangular cross-section water tanks, silo structures, transfer beams in high-rise buildings, and bent caps. As a result of the low shear span ratio to effective depth (a/d) in deep beams, arch action occurs, which leads to shear failure. Several studies have been carried out to improve the shear resistance of RC deep beams and avoid brittle fracture behavior in recent years. This study was performed to investigate the behavior of RC deep beams numerically and experimentally with different reinforcement arrangements. Deep beams with four different reinforcement arrangements were produced and tested under monotonic static loading in the study's scope. The horizontal and vertical shear reinforcement members were changed in the test specimens to obtain the effects of different reinforcement arrangements. However, the rebars used for tension and the vertical shear reinforcement ratio were constant. In addition, the behavior of each deep beam was obtained numerically with commercial finite element analysis (FEA) software ABAQUS, and the findings were compared with the experimental results. The results showed that the reinforcements placed diagonally significantly increased the load-carrying and energy absorption capacities of RC deep beams. Moreover, an apparent plastic plateau was seen in the load-displacement curves of these test specimens in question (DE-2 and DE-3). This finding also indicated that diagonally located reinforcements improve displacement ductility. Also, the numerical results showed that the FEM method could be used to accurately predict RC deep beams'behavior with different reinforcement arrangements.

Development and commissioning of the UNIST electron beam ion trap

Park SungNam,Shin Bokkyun,Cosgun Emre,Han JeHwan,Chung Moses 한국물리학회 2024 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.84 No.5

An electron beam ion trap (EBIT) creates and confnes highly charged ions (HCIs). To maximize the movement of the EBIT towards and away from the accelerator beamlines, we adopted permanent magnets, thereby reducing the size and maintenance costs associated with the EBIT. A magnetic feld of 0.84 T at the trap center provided a trap capacity of approximately 107 charges. By sweeping the electron beam energy from 2.4 keV to 3.3 keV at an electron beam current of 10 mA, the silicon drift detector successfully measured the KLL lines of the HCI states of argon and confrmed the presence of up to He-like argon ions. Before measuring the highly charged irons for astrophysics purposes, we conducted preliminary experiments to connect the EBIT with the Pohang Accelerator Laboratory X-ray Free Electron Laser (PAL-XFEL) hard X-ray beamline. In this study, we present the initial operation of the compact EBIT at an XFEL facility, demonstrating its X-ray fuorescence measurement capability.

Behavior of reinforced concrete plates under impact loading: different support conditions and sizes

Metin Husem,Suleyman I. Cosgun 사단법인 한국계산역학회 2016 Computers and Concrete, An International Journal Vol.18 No.3

In this study, effects of impact loads on reinforced concrete (RC) plates are examined analytically. During examination of RC plates, they were exposed to impact loading with two different support conditions in three different sizes. RC plates in different support conditions were analyzed with Concrete Damage Plasticity Model (CDP) and reinforcing steel was modeled with Classical Metal Plasticity Model (CMP) by ABAQUS finite element software. After the analysis it is found that impact loads, displacements, energy absorption capacities and damage patterns are changed due to support conditions and plate sizes. Results that are obtained from RC plate experiments in literature under impact loads are found to be similar with the results of numerical analysis with CDP material models.

Push-out bond strength and dentinal tubule penetration of different root canal sealers used with coated core materials

Sungur, Derya Deniz,Purali, Nuhan,Cosgun, Erdal,Calt, Semra The Korean Academy of Conservative Dentistry 2016 Restorative Dentistry & Endodontics Vol.41 No.2

Objectives: The aim of this study was to compare the push-out bond strength and dentinal tubule penetration of root canal sealers used with coated core materials and conventional gutta-percha. Materials and Methods: A total of 72 single-rooted human mandibular incisors were instrumented with NiTi rotary files with irrigation of 2.5% NaOCl. The smear layer was removed with 17% ethylenediaminetetraacetic acid (EDTA). Specimens were assigned into four groups according to the obturation system: Group 1, EndoRez (Ultradent Product Inc.); Group 2, Activ GP (Brasseler); Group 3, SmartSeal (DFRP Ltd. Villa Farm); Group 4, AH 26 (Dentsply de Trey)/gutta-percha (GP). For push-out bond strength measurement, two horizontal slices were obtained from each specimen (n = 20). To compare dentinal tubule penetration, remaining 32 roots assigned to 4 groups as above were obturated with 0.1% Rhodamine B labeled sealers. One horizontal slice was obtained from the middle third of each specimen (n = 8) and scanned under confocal laser scanning electron microscope. Tubule penetration area, depth, and percentage were measured. Kruskall-Wallis test was used for statistical analysis. Results: EndoRez showed significantly lower push-out bond strength than the others (p < 0.05). No significant difference was found amongst the groups in terms of percentage of sealer penetration. SmartSeal showed the least penetration than the others (p < 0.05). Conclusions: The bond strength and sealer penetration of resin-and glass ionomer-based sealers used with coated core was not superior to resin-based sealer used with conventional GP. Dentinal tubule penetration has limited effect on bond strength. The use of conventional GP with sealer seems to be sufficient in terms of push-out bond strength.

Push-out bond strength and dentinal tubule penetration of different root canal sealers used with coated core materials

Derya Deniz Sungur,Nuhan Purali,Erdal Cosgun,Semra Calt 대한치과보존학회 2016 Restorative Dentistry & Endodontics Vol.41 No.2

Objectives: The aim of this study was to compare the push-out bond strength and dentinal tubule penetration of root canal sealers used with coated core materials and conventional gutta-percha. Materials and Methods: A total of 72 single-rooted human mandibular incisors were instrumented with NiTi rotary files with irrigation of 2.5% NaOCl. The smear layer was removed with 17% ethylenediaminetetraacetic acid (EDTA). Specimens were assigned into four groups according to the obturation system: Group 1, EndoRez (Ultradent Product Inc.); Group 2, Activ GP (Brasseler); Group 3, SmartSeal (DFRP Ltd. Villa Farm); Group 4, AH 26 (Dentsply de Trey)/gutta-percha (GP). For push-out bond strength measurement, two horizontal slices were obtained from each specimen (n = 20). To compare dentinal tubule penetration, remaining 32 roots assigned to 4 groups as above were obturated with 0.1% Rhodamine B labeled sealers. One horizontal slice was obtained from the middle third of each specimen (n = 8) and scanned under confocal laser scanning electron microscope. Tubule penetration area, depth, and percentage were measured. Kruskall-Wallis test was used for statistical analysis. Results: EndoRez showed significantly lower push-out bond strength than the others (p < 0.05). No significant difference was found amongst the groups in terms of percentage of sealer penetration. SmartSeal showed the least penetration than the others (p < 0.05). Conclusions: The bond strength and sealer penetration of resinand glass ionomer-based sealers used with coated core was not superior to resin-based sealer used with conventional GP. Dentinal tubule penetration has limited effect on bond strength. The use of conventional GP with sealer seems to be sufficient in terms of push-out bond strength.