Browsing by Author "Ercan E."
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Item Atorvastatin treatment decreases inflammatory and proteolytic activity in patients with hypercholesterolemia(Klinika Kardiologii CMKP, 2004) Ercan E.; Tengiz I.; Altuglu I.; Sekuri C.; Aliyev E.; Ercan H.E.; Akin M.Background. Statins have anti-inflammatory and anti-platelet effects, which are known as non-lipid effects. Statin treatment can decrease endogenous inflammatory response. Aim. To study the effects of atorvastatin on matrix metalloproteinase-9 (MMP-9) and high sensitive C-reactive protein (hs-CRP) - markers of the proteinolytic and inflammatory activity. Methods. In this prospective study 44 patients with hypercholesterolemia were randomly assigned into 2 groups; Group 1 (n=22) treated with atorvastatin and diet for 2 months, and Group 2 (n=22) - diet alone. MMP-9 and hs-CRP were measured at baseline and two months later. Results. Groups were matched for age, sex and baseline characteristics. Lipid levels decreased by 32% (LDL from 153.9±26.6 to 94.5±20.8 mg/dl, p<0.005) in the atorvastatin group and by 9% in the diet alone group. Atorvastatin lowered plasma CRP from 5.16±1.9 to 2.88±1.06 mg/L (p<0.001) and MMP-9 activity from 64.3±28.1 to 35.4±20.0 ng/ml (p<0.0001). Atorvastatin-induced reductions in CRP and MMP-9 were greater than in the diet alone group. MMP-9 levels did not show significant changes in Group 2 after two months of diet. Conclusions. Atorvastatin treatment decreases inflammatory and proteolytic activity in patients with hypercholesterolemia.Item Renin-angiotensin system gene polymorphisms and premature coronary heart disease(JRAAS Limited, 2005) Sekuri C.; Cam F.S.; Ercan E.; Tengiz I.; Sagcan A.; Eser E.; Berdeli A.; Akin M.Introduction: Experimental and clinical studies demonstrated that the renin-angiotensin system (RAS) affects the pathogenesis of atherosclerosis and prognosis of coronary heart disease (CHD). The aim of this study was to investigate the genotype distribution and the allele frequencies of three RAS genes polymorphisms and their effects on premature CHD in a Turkish population. Materials and methods: One-hundred and fifteen Turkish patients with premature CHD and 128 controls were included into the study. Angiotensin-converting enzyme (ACE), angiotensin II type 1 (AT1) receptor and angiotensinogen (AGT) gene polymorphisms were analysed by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP). Results: The patients group showed an increased frequency of the ACE D allele compared with controls (65% vs. 35%, p-0.0001). There was a significant association between the DD genotype and premature CHD (ACE DD vs. ID and II; odds ratio [OR]=2.82 [CI 95% 1.33-2.91, P=0.002]). Also, we observed increased premature CHD risk associated with higher frequencies of the AGT MM genotype in patients when compared with controls (AGT MM vs. TT and MT, OR=1.92 [CI 95% 1.11-3-33, p=0.018]). We found a significant association between AT1-receptor AA genotype and decreased risk of premature CHD (AT1R AA vs. AC and CC, OR=0.57[CI 95% 0.34-0.95, p=0.03]). Conclusions: We demonstrated that increased premature CHD risk is associated with higher frequencies of the ACE DD and AGT MM genotypes. These findings indicate a synergistic contribution of ACE DD and AGT MM polymorphisms to the development of premature CHD. Also, our results suggest that family history, smoking, diabetes, hypertension, obesity and ACE DD genotype were independent risk factors for premature CHD.Item Association between the eNOS (Glu298Asp) and the RAS genes polymorphisms and premature coronary artery disease in a Turkish population(2005) Berdeli A.; Sekuri C.; Sirri Cam F.; Ercan E.; Sagcan A.; Tengiz I.; Eser E.; Akin M.The renin-angiotensin system (RAS) and endothelial nitric oxide (NO) affect the pathogenesis of atherosclerosis and prognosis of coronary artery disease (CAD). Previous epidemiologic data suggested that genetic factors are more likely to affect young rather than old people. Our objective was to investigate the association between the polymorphisms of eNOS (Glu298Asp) and the RAS genes and premature CAD in a Turkish population. A total of 115 Turkish patients with premature CAD and 83 controls were included in the study. ACE I/D, AT1R A/C, AGT T/M and eNOS Glu298Asp gene polymorphisms were analysed by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP). It was found that increased premature CAD risk is associated with higher frequencies of the ACE DD [OR: 2.600 (CI 95% 1.395-4.847, p=0.002)], AGT MM [OR=2.407 (CI 95% 1.267-4.573, p=0.007)] and eNOS 894TT [OR=17.000 (CI 95% 3.952-73.125, p<0.001)] genotypes. Carriers of ACE DD+eNOS 894TT (p=0.002), AGT MM+eNOS 894TT (p=0.001), AT1R AA+eNOS 894TT and AT1R non-AA+eNOS 894TT (p=0.002) genotypes were significantly associated with the risk of premature CAD. This study indicates a synergistic contribution of RAS genes (ACE I/D, AGT T/M, AT1R T/C) and eNOS Glu298Asp polymorphisms to the development of the premature CAD. © 2004 Elsevier B.V. All rights reserved.Item The G894T polymorphism on endothelial nitric oxide synthase gene is associated with premature coronary artery disease in a Turkish population(2005) Cam S.F.; Sekuri C.; Tengiz I.; Ercan E.; Sagcan A.; Akin M.; Berdeli A.Introduction: The aim of the present study was to investigate the association between premature coronary artery disease and Glu298Asp polymorphism of the endothelial nitric oxide synthase gene. Materials and methods: The eNOS gene polymorphism was analysed in 115 (mean age, 48.1±7.9 years) Turkish patients with a diagnosis of premature coronary artery disease and 83 (mean age, 44.6±1.4 years) control subjects. The Glu298Asp polymorphism of the endothelial nitric oxide synthase gene was determined by polymerase chain reaction and restriction fragment length polymorphism. Results: The patients group showed an increase in the frequency of the T allele compared to controls (0.456 versus 0.169, p=0.0001). There was a significant association between the TT genotype and premature coronary artery disease [eNOS TT vs. TG and GG; OR=17.000 (CI 95% 3.952-73.125, p=0.0001)]. The eNOS T/G genotypes were not associated with the number of affected vessels (p>0.05). In addition, the family history of premature coronary artery disease, smoking, diabetes, obesity, dyslipidemia and eNOS TT genotype were independent risk factors of coronary artery disease. The patients with eNOS TT genotype had 15 fold risk of coronary artery disease compared with the control group [OR=15.356(CI 95% 3.262-77.289, p=0.001)]. Conclusions: These results suggest that premature coronary artery disease is associated with the Glu298Asp polymorphism of the endothelial nitric oxide synthase gene in our population. © 2004 Elsevier Ltd. All rights reserved.Item Association of platelet-activating factor acetylhydrolase gene polymorphism with premature coronary artery disease in Turkish patients(2006) Şekuri C.; Çam F.S.; Tengiz I.; Ercan E.; Bayturan Ö.; Berdeli A.Objective: Platelet-activating factor (PAF) is a phospholipid with multiple actions that is involved in inflammatory diseases as well as in atherogenesis. It is inactivated by a plasma enzyme, PAF-acetylhydrolase (PAF-AH). Deficiency of this enzyme in plasma is caused by a missense mutation in the gene (G994T). The aim of this study was to investigate association of this mutation with premature coronary artery disease (CAD). Methods: One hundred and fifteen unrelated Turkish patients with a diagnosis of premature CAD and 128 unrelated healthy subjects were enrolled in this study. Genotyping was performed by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP). Results: The prevalence of the G994T mutation in the patients was 2.60 % (heterozygote), and 0 % in the controls. There was no significant difference in allele frequency and genotype distribution among the study groups. Conclusion: The G9943T mutation in the plasma PAF acetylhydrola se gene is not associated with premature CAD in Turkish subjects.Item No association of interleukin-6 gene polymorphism (-174 G/C) with premature coronary artery disease in a Turkish cohort(2007) Sekuri C.; Cam F.S.; Sagcan A.; Ercan E.; Tengiz I.; Alioglu E.; Berdeli A.OBJECTIVES: Interleukin-6 (IL-6) may contribute to the inflammatory response by activating endothelial cells and stimulating the synthesis of fibrinogen. It might thus be important in the pathogenesis of inflammation associated with coronary artery disease (CAD). Several studies suggested that the -174 C allele was associated with an increased prevalence of coronary heart disease. The aim of this study was to investigate further the association of the IL-6 -174 G/C allele status with premature CAD. METHODS: A total of 120 patients and 105 controls were included in the study. The IL-6 -174 G/C polymorphism was genotyped using PCR-restriction fragment length polymorphism. RESULTS: The genotype distribution of the -174 G/C polymorphism was not different in premature CAD patients (GG: 53%; GC: 42.6%; CC: 4.3%) and controls (GG: 54.3%; GC: 39%; CC: 6.7%) (P=0.72). The prevalence of the C allele was 25.6% in patients and 26.1% in controls. By multiple regression analysis, family history, smoking, diabetes, and hypertension were independent risk factors of premature CAD, but not IL-6 genotype. CONCLUSIONS: We conclude that the IL-6 -174 G/C polymorphism is not associated with the risk of premature CAD, and does not contribute to cardiovascular risk stratification. © 2007 Lippincott Williams & Wilkins, Inc.Item G protein β3 subunit gene polymorphism in Turkish hypertensives(2008) Alioǧlu E.; Ercan E.; Tengiz I.; Yildiz A.; Saygi U.ö.T.S.; Çam F.S.; Berdeli A.Objective: G protein is one of the most important regulators of intracellular signaling pathways. C825T polymorphism of G protein β3 subunit is associated with increased intracellular signal transduction. The 825T allele has been found associated with a variety of cardiovascular risk factors, including hypertension. The aim of the present study was to investigate the association between the C825T polymorphism of the G protein β3 subunit and essential hypertension in Turkish population. Methods: This cross-sectional, case-controlled study included 209 patients with essential hypertension (Patient group) and 82 subjects with normal blood pressure (Control group). The G protein β3 subunit C825T gene polymorphism was determined by polymerase chain reaction. Hypertension was defined according to JNC VII criteria. Statistical analysis was performed using Chi square and unpaired t tests. Logistic regression analysis was used to study association between hypertension and genotypes. Results: We found that the frequencies of the G protein β3 subunit C825T polymorphism in hypertensive and control groups were 17.7%, 59.3%, 23.0% and 32.9%, 48.8%, 18.3%, (CC, CT, TT) respectively (χ2=7.963, p=0.019). In the multivariate logistic regression analysis CT genotype had 2.2 (OR=2.262, 95% CI 1.228-4.167, p=0.009), and TT genotype had 2.3 times (OR=2.335, 95% CI 1.089-5.008, p=0.029) greater risk of hypertension compared to CC genotype. Conclusion: It seems that the G protein β3 subunit C825T gene polymorphism is associated with systolic a diastolic blood pressure. Furthermore, the study indicates that the G protein β3 subunit may be a susceptible gene to essential hypertension.Item Effect of monocyte chemoattractant protein-1 (MCP-1) gene polymorphism in Turkish patients with premature coronary artery disease(2008) Cam S.F.; Sekuri C.; Sagcan A.; Ercan E.; Tengiz I.; Alioglu E.; Berdeli A.Objectives. It has been suggested that monocyte chemoattractant protein-1 (MCP-1) is important in the initiation of atherosclerosis and crucial in monocyte recruitment into the subendothelial lesions. Recent studies have demonstrated that MCP-1 -2518 A>G polymorphism is associated with susceptibility to coronary artery disease (CAD). Since there are conflicting reports on the possible association of MCP-1 -2518 A>G polymorphism with CAD, we investigated the role of this polymorphism in Turkish patients with premature CAD. Material and methods. Genomic DNA was collected from 171 premature CAD patients and 151 healthy individuals. MCP-1 -2518 A>G polymorphism was genotyped using the PCR-RFLP method. Results. There were no differences between genotype distribution and allele frequencies in the premature CAD and control groups (AA: 49.7 %; AG: 40.3 %; GG: 10.0 % in premature CAD groups and AA: 53.7 %; AG: 34.4 %; GG: 11.9 % in controls; p = 0.53). The prevalence of the G allele was 0.302 in patients and 0.291 in controls. Conclusions. Our data demonstrate that MCP-1 -2518 A>G polymorphism is not associated with premature CAD in Turkish patients. Further studies are needed to elucidate the role of this polymorphism in the pathogenesis of CAD in various populations. © 2008 Informa UK Ltd (Informa Healthcare, Taylor & Francis AS).Item Polymorphisms of the methylenetetrahydrofolate reductase, vascular endothelial growth factor, endothelial nitric oxide synthase, monocyte chemoattractant protein-1 and apolipoprotein E genes are not associated with carotid intima-media thickness(Pulsus Group Inc., 2009) Alioglu E.; Turk U.; Cam S.; Abbasaliyev A.; Tengiz I.; Ercan E.Background: Single nucleotide polymorphisms in the 5,10-methyl-enetetrahydrofolate reductase (MTHFR), vascular endothelial growth factor (VEGF), endothelial nitric oxide synthase (eNOS), monocyte chemoattractant protein-1 (MCP-1) and apolipoprotein E (ApoE) genes appear to be a genetic risk factor for atherosclerosis. Common carotid intima-media thickness (cIMT) provides information on the severity of atherosclerosis. Objective: To investigate the relationship between cIMT and gene polymorphisms associated with atherosclerosis in Turkish patients with coronary artery disease (CAD). Methods: Sixty-two patients with angiographically diagnosed stable CAD were divided into two groups according to their cIMT values (group 1: n=35, cIMT of 1 mm or greater; group 2: n=27, cIMT of less than 1 mm). MTHFR 677 C/T, VEGF -460 C/T, eNOS 894 G/T, MCP-1 -2518 A/G and ApoE (E2, E3 and E4) gene polymorphisms (where A is adenine, C is cytosine, G is guanine and T is thymine) were analyzed by polymerase chain reaction and restriction fragment length polymorphism. Evaluations of cardiovascular risk factors and coronary atherosclerotic lesions were performed in all patients. Serum homocysteine and high-sensitivity C-reactive protein were measured and compared between the two groups. Results: Serum high-sensitivity C-reactive protein (P=0.04) and homocysteine (P=0.006) levels were higher in group 1 than in group 2. The ratio of multivessel CAD and previous myocardial infarction was significantly higher in group 1 than in group 2 (P=0.014). In the study population, no significant difference in cIMT was observed according to the polymorphisms studied. Only hyperhomocysteinemia (OR 1.17 [95% CI 1.01 to 1.35], P=0.033) and previous myocardial infarction (OR 3.76 [95% CI 1.10 to 12.81], P=0.034) maintained a significant correlation with cIMT on multiple logistic regression analysis. Conclusion: cIMT is increased in patients with hyperhomocysteinemia, inflammation and extended CAD. MTHFR 677 C/T, VEGF -460 C/T, eNOS 894 G/ T, MCP-1 -2518 A/G and ApoE single nucleotide polymorphisms were not associated with increased cIMT. © 2009 Pulsus Group Inc. All rights reserved.Item Shaking table study of masonry buildings with reinforced plaster; [Ispitivanje zidanih gradevina s armiranom žbukom na vibracijskom stolu](Union of Croatian Civil Engineers and Technicians, 2014) Ba̧aran H.; Demir A.; Bagci M.; Ercan E.The objective of this study is to determine seismic behaviour of masonry buildings with reinforced plaster mortar, with a particular focus on the modification of structural response due to application of the polypropylene and steel reinforced plaster, as compared to an ordinary type of plaster. The resistance of one-storey single-span masonry buildings subjected to seismic load on the shaking table is investigated in the study. Experimental results revealed natural periods, response acceleration spectrums, and spectrum interactions of masonry buildings. In addition, finite element models of test buildings were established, and their results were compared with those obtained during experimental study.Item Effects of fiber reinforced plaster on the earthquake behavior of masonry buildings(Shiraz University, 2015) Başaran H.; Demir A.; Baǧci M.; Ercan E.In this paper the traditional covering plaster of masonry buildings is supplied with Polypropylene and steel fiber to enhance their seismic behavior. The plaster mix proportion is determined by some initial mortar tests. Also, one story, single span masonry building specimen plastered with different mortars is tested on a shaking table 8 times under a seismic input and the performance of the specimens with the above types of mortar is evaluated. The specimen plastered with a traditional plaster was regarded as control and its earthquake behavior was compared to that reinforced by fiber plaster. Steel fiber or polypropylene addition significantly increased stiffness, displacement ability and energy consumption ability of specimens as compared to control. The suggested reinforcement method was proven to strengthen masonry buildings in a fast, reliable and economical way. Moreover, it can easily be adapted to any masonry building without causing any negative impact. The suggested method is fire and corrosion resistant. © Shiraz University.Item Strengthening of brick masonry with PVA fiber reinforced cement stucco(Elsevier Ltd, 2015) Arisoy B.; Ercan E.; Demir A.This paper presents the behavior of masonry walls externally strengthened by poly vinyl alcohol (PVA) fiber reinforced cement plaster. Tensile weakness of masonry wall is improved by simply applying fiber reinforced cement (FRC) plaster on masonry surface. Strengthening by ductile materials, in order to maintain ductile behavior of masonry to resist shear forces would provide reduction in the crack development and crack width providing delay in failure. FRC was applied to surfaces of the masonry wall as stucco to prevent crack growth under shear effect. An experimental program was performed to study the response of unreinforced and retrofitted masonry walls with externally applied fiber reinforced cement mixture, under shear and compressive loading. The experimental results indicate that retrofitting masonry walls with PVA fiber reinforced cement stucco increases the shear strength of the wall approximately half times in solid and high strength brick walls, 2.5 times in regular brick walls. © 2015 Elsevier Ltd. All rights reserved.Item Investigation of a historic masonry structure by numerical and operational modal analyses(John Wiley and Sons Ltd, 2015) Nohutcu H.; Demir A.; Ercan E.; Hokelekli E.; Altintas G.This paper presents the results of model calibration conducted on a historical mosque called Hafsa Sultan in Manisa, Turkey. The finite element model of the mosque was calibrated by the use of the results obtained from ambient vibration tests of the structure. In order to develop a solid model of the structure, the dimensions of the structure, defects such as cracks and material degradations in the structure, and the materials used in different parts were identified. For the evaluation of the material properties of the structure, nondestructive and destructive testing methods were used. The numerical and experimental modal parameters of the structure were obtained by finite element method (FEM) and Operational Modal Analysis (OMA), respectively. The natural frequencies and corresponding mode shapes were obtained from both FEM and OMA and compared with each other. While a good compatibility was achieved between mode shapes, some differences between natural frequencies occurred. It was thought that the differences resulted from variations in the Young's modulus of masonry, cracks in elements or boundary conditions. Therefore, the finite element model was calibrated by changing material parameters. Finally, a more realistic numerical model of the mosque was put forward and the results were discussed in detail. Copyright © 2015 John Wiley & Sons, Ltd.Item Investigation of seismic safety of a masonry minaret using its dynamic characteristics(Techno Press, 2016) Başaran H.; Demir A.; Ercan E.; Nohutçu H.; Hökelekli E.; Kozanoğlu C.Besides their spiritual significance, minarets are humanity's cultural heritage to the future generations due to their historical and architectural attraction. Currently, many historical masonry minarets are damaged and destroyed due to several reasons such as earthquakes and wind. Therefore, safety of these religiously significant buildings needs to be thoroughly investigated. The utmost care must be taken into account while investigating these structures. Our study investigated earthquake behavior of historical masonry minaret of Haci Mahmut Mosque. Destructive and non-destructive tests were carried out to determine earthquake safety of this structure. Brick-stone masonry material properties of structure were determined by accomplishing ultrasonic wave velocity, Schmidt Hammer, uniaxial compression (UAC) and indirect tension (Brazilian) tests. Determined material properties were used in the finite element analysis of the structure. To validate the numerical analysis, Operational Modal Analysis was applied to the structure and dynamic characteristics of the structure were determined. To this end, accelerometers were placed on the structure and vibrations due to environmental effects were followed. Finite element model of the minaret was updated using dynamic characteristics of the structure and the realistic numerical model of the structure was obtained. This numerical model was solved by using earthquake records of Turkey with time history analysis (THA) and the realistic earthquake behavior of the structure was introduced. © 2016 Techno-Press, Ltd.Item Effect of model calibration on seismic behaviour of a historical mosque(Techno-Press, 2016) Demir A.; Nohutcu H.; Ercan E.; Hokelekli E.; Altintas G.The objective of the study is to investigate the effects of model calibration on seismic behaviour of a historical mosque which is one of the most significant Ottomon structures. Seismic analyses of calibrated and noncalibrated numeric models were carried out by using acceleration records of Kocaeli earthquake in 1999. In numerical analysis, existing crack zones on real structure was investigated in detail. As a result of analyses, maximum stresses and displacements of calibrated and noncalibrated numerical models were compared each other. Consequently, seismic behaviour and damage state of historical masonry Hafsa Sultan mosque was determined as more realistic in the event of a severe earthquake. Copyright © 2016 Techno-Press, Ltd.Item Finite element model updating of a historical minaret via operational modal analysis(International Operational Modal Analysis Conference (IOMAC), 2017) Ercan E.; Hökelekli E.; Demir A.; Nohutçu H.Finite element method is commonly used for analysis of historical structures. However, since material properties of historical structures are evaluated from destructive tests using empirical formulas, this approach makes the results of finite element analysis questionable. In recent years Operational Modal Analysis of historical masonry structures have found great interest because by the help of Operational Modal Analysis, the material parameters and the boundary conditions can be verified and the finite element model can be updated. The updated model is a more realistic model of the historical structures and gives more accurate results. This study describes the results of a model updating study conducted on a historical minaret. For the purposes of developing a 3-D solid model of the minaret; the dimensions, defects and material degradations in the minaret were determined in detail by making a measurement survey. For evaluation of the material properties of the minaret, nondestructive and destructive testing methods were applied. The modal analysis of the structure was done by FEM. Then, Operational Modal Analysis was carried out and dynamic properties were extracted. The results obtained from ambient vibration measurements of the minaret were used to update the finite element model of the minaret. The natural frequencies and corresponding mode shapes were determined from both theoretical and experimental modal analyses and compared with each other. A good harmony was attained between mode shapes, but differences between natural frequencies were observed. Model updating was realized via changing material parameters and boundary conditions. Finally, the more realistic finite element model of the minaret was put forward and the results were discussed.Item Collapse mechanism estimation of a historical slender minaret(Techno-Press, 2017) Nohutcu H.; Hokelekli E.; Ercan E.; Demir A.; Altintas G.The aim of this study is to accurately estimate seismic damage and the collapse mechanism of the historical stone masonry minaret "Hafsa Sultan", which was built in 1522. Surveying measurements and material tests were conducted to obtain a 3D solid model and the mechanical properties of the components of the minaret. The initial Finite Element (FE) model is analyzed and numerical dynamic characteristics of the minaret are obtained. The Operational Modal Analysis (OMA) method is conducted to obtain the experimental dynamic characteristics of the minaret and the initial FE model is calibrated by using the experimental results. Then, linear time history (LTH) and nonlinear time history (NLTH) analyses are carried out on the calibrated FE model by using two different ground motions. Iron clamps which used as connection element between the stones of the minaret considerably increase the tensile strength of the masonry system. The Concrete Damage Plasticity (CDP) model is selected in the nonlinear analyses in ABAQUS. The analyses conducted indicate that the results of the linear analyses are not as realistic as the nonlinear analysis results when compared with existing damage. Copyright © 2017 Techno-Press, Ltd.Item Strengthening of reinforced concrete beams using external steel members(Techno Press, 2018) Demir A.; Ercan E.; Demir D.D.The objective of this study is to devise an alternative strengthening method to the ones available in the literature. So, external steel members were used to enhance both flexural and shear capacities of reinforced concrete (RC) beams having insufficient shear capacity. Two types of RC beams, one without stirrups and one with lacking stirrups, were prepared in the study. These beams were strengthened with external steel clamps devised by the authors and with external longitudinal reinforcements. Although the use of clamps alone didn’t have a significant effect on the load carrying capacity of the tested beams, the ductility increased approximately tenfold and the failure behavior changed from brittle to ductile. Although the use of clamps and longitudinal reinforcements together did not significantly increase the ductility of the beams, it approximately doubled their load capacities. The results of the experimental study were compared to the ones obtained from nonlinear finite element analysis (NLFEA) and it was observed that they were compatible. Finally, it can be concluded that the devised method could be applied to structural members as an alternative to methods in application due to lightness, low-cost, easy applicable and reliable. Copyright © 2018 Techno-Press, Ltd.Item Analysis of strengthened composite beams under flexural stress(Springer, 2018) Ercan E.; Arısoy B.; Demir A.; Özdemir A.A steel-concrete composite beam is composed of a steel beam and concrete slap connected with shear connectors. Composite beams are highly efficient structural members in order to load carrying capacity because the tension component of the force pair originating from bending is carried by the steel profile and the compressive component is carried by the concrete slab in composite beams. In this study, numerical and experimental analysis of steel-concrete composite and strengthened steel-concrete composite beams is presented. In experimental study, one strengthened and one un-strengthened specimens are produced and tested in bending. Strengthening is produced applying carbon fiber reinforced polymers sheet to the lower flange of the steel beam and using steel fiber reinforced concrete in the concrete slab. Specimens are tested under four-point loading test. During the tests, load, deflection and strain values are collected by data acquisition system. In numerical study, the finite element models of the steel-concrete composite beams are generated and analyzed by Atena-GiD program. Comparison and evaluations are made in terms of strength, applicability, stiffness and energy consumption about the steel-concrete composite beams with carbon fiber reinforced polymers and steel fibered concrete for both numerical and experimental results. © Springer International Publishing AG, part of Springer Nature 2018.Item Seismic assessment in a historical masonry minaret by linear and non-linear seismic analyses(Budapest University of Technology and Economics, 2020) Hökelekli E.; Demir A.; Ercan E.; Nohutçu H.; Karabulut A.Operational Modal Analysis (OMA) method is frequently used in order to determine dynamical properties of historical masonry structures. In this study, damage pattern of historical Alaca minaret which is selected as application is investigated under different ground motions by updating finite element models (FEM) depending on operational modal analysis test. Initial Finite element model was prepared in ABAQUS V10 program and numerical dynamic characteristics of minaret were determined. In addition, experimental dynamic properties of minaret were provided by operational modal analysis. Initial numerical model of brick masonry structure was calibrated via OMA method. Then, linear and non-linear seismic analyses of calibrated FEM of historical minaret were performed by using different earthquakes acceleration records that occurred in Turkey. Concrete Damage Plasticity model was taken into account in non-linear seismic analyses. As a result of the analyses, it is concluded that the stresses obtained with linear analyses aren’t as realistic as the non-linear analyses results and the earthquakes can cause some damages in the minaret. © 2020, Budapest University of Technology and Economics. All rights reserved.