Composed material models for nonlinear behavior of reinforced concrete

Tayfun Dede,Yusuf Ayvaz 사단법인 한국계산역학회 2013 Computers and Concrete, An International Journal Vol.12 No.3

The purpose of this study is to present different composed material models for reinforced concrete structures (RC). For this aim a nonlinear finite element analysis program is coded in MATLAB. This program contains several yield criteria and stress-strain relationships for compression and tension behavior of concrete. In this study, the well-known criteria, Drucker-Prager, von Mises, Mohr Coulomb, Tresca, and two new criteria, Hsieh-Ting-Chen and Bresler-Pister, are taken into account. It is concluded that the coded program, the new yield criteria, and the models considered can be effectively used in the nonlinear analysis of reinforced concrete beams.

Structural optimization with teaching-learning-based optimization algorithm

Tayfun Dede,Yusuf Ayvaz 국제구조공학회 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.47 No.4

In this paper, a new efficient optimization algorithm called Teaching–Learning-Based Optimization (TLBO) is used for the least weight design of trusses with continuous design variables. The TLBO algorithm is based on the effect of the influence of a teacher on the output of learners in a class. Several truss structures are analyzed to show the efficiency of the TLBO algorithm and the results are compared with those reported in the literature. It is concluded that the TLBO algorithm presented in this study can be effectively used in the weight minimization of truss structures.

A teaching learning based optimization for truss structures with frequency constraints

Tayfun Dede,Vedat Toğan 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.53 No.4

Natural frequencies of the structural systems should be far away from the excitation frequency in order to avoid or reduce the destructive effects of dynamic loads on structures. To accomplish this goal, a structural optimization on size and shape has been performed considering frequency constraints. Such anoptimization problem has highly nonlinear property. Thus, the quality of the solution is not independent of the optimization technique to be applied. This study presents the performance evaluation of the recently proposed meta-heuristic algorithm called Teaching Learning Based Optimization (TLBO) as an optimization engine in the weight optimization of the truss structures under frequency constraints. Some examples regarding the optimization of trusses on shape and size with frequency constraints are solved. Also, the results obtained are tabulated for comparison. The results demonstrated that the performance of the TLBO is satisfactory. Additionally, TLBO is better than other methods in some cases.

Continuous size optimization of large-scale dome structures with dynamic constraints

Tayfun DEDE,Maksym Grzywiński,Jacek Selejdak 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.73 No.4

In this study size optimization of large-scale dome structures with dynamic constraints is presented. In the optimal design of these structure, the Jaya algorithm is used to find minimal size of design variables. The design variables are the cross-sectional areas of the steel truss bar elements. To take into account the constraints which are the first five natural frequencies of the structures, the finite element analysis is coded in Matlab programs using eigen values of the stiffness matrix of the dome structures. The Jaya algorithm and the finite elements codes are combined by the help of the Matlab - GUI (Graphical User Interface) programming to carry out the optimization process for the dome structures. To show the efficiency and the advances of the Jaya algorithm, 1180 bar dome structure and the 1410 bar dome structure were tested by taking into the frequency constraints. The optimal results obtained by the proposed algorithm are compared with those given in the literature to demonstrate the performance of the Jaya algorithm. At the end of the study, it is concluded that the proposed algorithm can be effectively used in the optimal design of large-scale dome structures.

Towards Face Recognition Using Caricature Making Techniques

Tayfun Akgul 한국정보통신학회 2012 2016 INTERNATIONAL CONFERENCE Vol.5 No.1

Jaya algorithm to solve single objective size optimization problem for steel grillage structures

Tayfun Dede 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.26 No.2

The purpose of this paper is to present a new and efficient optimization algorithm called Jaya for optimum design of steel grillage structure. Constrained size optimization of this type of structure based on the LRFD-AISC is carried out with integer design variables by using cross-sectional area of W-shapes. The objective function of the problem is to find minimum weight of the grillage structure. The maximum stress ratio and the maximum displacement in the inner point of steel grillage structure are taken as the constraint for this optimization problem. To calculate the moment and shear force of the each member and calculate the joint displacement, the finite elements analysis is used. The developed computer program for the analysis and design of grillage structure and the optimization algorithm for Jaya are coded in MATLAB. The results obtained from this study are compared with the previous works for grillage structure. The results show that the Jaya algorithm presented in this study can be effectively used in the optimal design of grillage structures.

Influence of steel-fiber type and content on electrical resistivity of old-concrete

Tayfun Uygunoglu,Ilker Bekir Topcu,Baris Simsek 사단법인 한국계산역학회 2018 Computers and Concrete, An International Journal Vol.21 No.1

Electrical resistivity is a property associated with both the physical and chemical characteristics of concrete. It allows the evaluation of the greater or lesser difficulty with which aggressive substances penetrate the concrete\'s core before the dissolution of the passive film process and the consequent reinforcement\'s corrosion begin. This work addresses the steel fiber addition to concrete with two types and various contents from 0% to 1.3%, correlating it with its electrical resistivity. To that effect, 9 different mixes of steel fiber reinforced concrete (SFRC) were produced. The electrical resistivity was evaluated on the on six years aged SFRC by direct measurement at different frequency from 0.1 kHz to 100 kHz. The results indicate that steel fiber content is strongly conditioned by the type and quantity of the additions used. It was also found that long type of fibers has more effect on decreasing the electrical resistivity of concrete than short fibers. Therefore, they increase the corrosion risk of concrete depending on fiber volume fraction and moisture percentage.

Application of Teaching-Learning-based-Optimization Algorithm for the Discrete Optimization of Truss Structures

Tayfun Dede 대한토목학회 2014 KSCE JOURNAL OF CIVIL ENGINEERING Vol.18 No.6

The aim of this study is to present a new efficient optimization algorithm called Teaching-Learning-Based Optimization (TLBO). The TLBO algorithm is based on the effect of the influence of a teacher on the output of learners in a class. Several benchmarkproblem related truss structures with discrete design variables are used to show the efficiency of the TLBO algorithm and the resultsare compared with those reported in the literature. It is concluded that the TLBO algorithm presented in this study can be effectivelyused in the weight minimization of truss structures.

The Effects of Galantamine Hydrobromide Treatment on Dehydroepiandrosterone Sulfate and Cortisol Levels in Patients with Chronic Fatigue Syndrome

Tayfun Turan,Hasan Basri Izgi,Saliha Ozsoy,Fatih Tanrıverdi,Mustafa Basturk,Akif Asdemir,Aslı Beşirli,Ertugrul Esel,Seher Sofuoglu 대한신경정신의학회 2009 PSYCHIATRY INVESTIGATION Vol.6 No.3

Objective: Mental fatigue, cognitive disorders, and sleep disturbances seen in chronic fatigue syndrome (CFS) may be attributed to cholinergic deficit. A functional deficiency of cholinergic neurotransmission may cause the hypothalamic-pituitary-adrenal axis hypoactivity seen in CFS. Therefore, we investigated the alterations in stress hormones such as cortisol and dehydroepiandrosterone sulfate (DHEAS) in CFS patients before and after 4- week administration of galantamine hydrobromide, a selective cetylcholinesterase inhibitor, and aimed to investigate whether there are any relationships between the probable hormonal changes and cholinergic treatment. Methods: Basal levels of cortisol and DHEAS were measured in 29 untreated CFS patients who were diagnosed according to Centers for Disease Control (CDC) criteria and in 20 healthy controls. In the patient group, four weeks after 8 ㎎/d galantamine hydrobromide treatment, cortisol and DHEAS levels were measured again. After the treatment 22 patients who stayed in study were divided into two subgroups as responders and nonresponders according to the reduction in their Newcastle Research Group ME/CFS Score Card (NRG) scores. Results: Important findings of this study are lower pre-and post-treatment cortisol levels and in all CFS patients compared to controls (F=4.129, p=0.049; F=4.803, p=0.035, respectively); higher basal DHEAS values and higher DHEAS/cortisol molar ratios which were normalized following four weeks’ treatment with 8 ㎎/d galantamine hydrobromide in the treatment-respondent group (F=5.382, p=0.029; F=5.722, p=0.025, respectively). Conclusion: The findings of the decrease in basal DHEAS levels and DHEAS/cortisol molar ratios normalizing with galantamine treatment may give some support to the cholinergic deficit hypothesis in CFS. Objective: Mental fatigue, cognitive disorders, and sleep disturbances seen in chronic fatigue syndrome (CFS) may be attributed to cholinergic deficit. A functional deficiency of cholinergic neurotransmission may cause the hypothalamic-pituitary-adrenal axis hypoactivity seen in CFS. Therefore, we investigated the alterations in stress hormones such as cortisol and dehydroepiandrosterone sulfate (DHEAS) in CFS patients before and after 4- week administration of galantamine hydrobromide, a selective cetylcholinesterase inhibitor, and aimed to investigate whether there are any relationships between the probable hormonal changes and cholinergic treatment. Methods: Basal levels of cortisol and DHEAS were measured in 29 untreated CFS patients who were diagnosed according to Centers for Disease Control (CDC) criteria and in 20 healthy controls. In the patient group, four weeks after 8 ㎎/d galantamine hydrobromide treatment, cortisol and DHEAS levels were measured again. After the treatment 22 patients who stayed in study were divided into two subgroups as responders and nonresponders according to the reduction in their Newcastle Research Group ME/CFS Score Card (NRG) scores. Results: Important findings of this study are lower pre-and post-treatment cortisol levels and in all CFS patients compared to controls (F=4.129, p=0.049; F=4.803, p=0.035, respectively); higher basal DHEAS values and higher DHEAS/cortisol molar ratios which were normalized following four weeks’ treatment with 8 ㎎/d galantamine hydrobromide in the treatment-respondent group (F=5.382, p=0.029; F=5.722, p=0.025, respectively). Conclusion: The findings of the decrease in basal DHEAS levels and DHEAS/cortisol molar ratios normalizing with galantamine treatment may give some support to the cholinergic deficit hypothesis in CFS.

Manic Episode Associated with Mega Cisterna Magna

Tayfun Turan,Aslı Bes¸irll,Akif Asdemir,Saliha Özsoy,Ertug˘rul Es¸el 대한신경정신의학회 2010 PSYCHIATRY INVESTIGATION Vol.7 No.4

Mega cisterna magna is a part of “Dandy-Walker Complex” and it is characterized by the enlargement of the cisterna magna, morphologically intact vermis and cerebellar hemispheres. We report a case of manic attack in a 23-year-old man with mega cisterna magna. The patient was treated with quetiapine 1,000 mg/day and sodium valproate 1,500 mg/day and the symptoms were ameliorated within 2.5 months. In this case, mega cisterna magna and manic symptoms may be found together coincidentally or any cerebellar dysfunction due to mega cisterna magna may cause or contribute to the appearance of affective symptoms. To our knowledge, this is the first case reporting manic attack with psychotic symptoms associated with mega cisterna magna. This report suggests that any lesion in the cerebellum might contribute to the occurrences of some affective and psychotic symptoms seen in bipolar disorder.