Analytical and Parametric Investigations on Lateral Torsional Buckling of European IPE and IPN Beams

Tolga Yilmaz,Nevzat Kirac 한국강구조학회 2017 International Journal of Steel Structures Vol.17 No.2

Lateral torsional buckling is one of the main failure modes controlling the strength of the slender thin-walled members. A transversely or transversely and axially combined loaded member that is bent with respect to its axis of greatest flexural rigidity may buckle laterally and twist as applied load reaches its critical value unless the beam is provided with a sufficient lateral support. This study intends to present a unique convenient equation that it can be used for calculating critical lateral-torsional buckling load of simply supported European IPE and IPN beams. First, an analytical model is introduced to describe lateraltorsional buckling behavior of beams with monosymmetric cross-section. The analytical model includes first order bending distribution, load height level and monosymmetry property of the section. Then, parametric study is carried out using the analytical solutions in order to establish a simplified equation with dimensionless coefficients. The effect of slenderness and loading positions on lateral-torsional buckling behavior of IPE and IPN beams are studied. The proposed solutions are compared to finite element simulations where thin-walled shell elements and beam elements including warping are used. Good agreement between the analytical, parametric and numerical solutions is demonstrated. It is found out that the lateral-torsional buckling load of European IPE and IPE beams can be determined by presented equation and can be safely used in design procedures.

An alternative evaluation of the LTB behavior of mono-symmetric beam-columns

Tolga Yilmaz,Nevzat Kiraç,Özgür Anil 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.30 No.5

Beam-columns are structural members subjected to a combination of axial and bending forces. Lateral-torsional buckling is one of the main failure modes. Beam-columns that are bent about its strong axis may buckle out of the plane by deflecting laterally and twisting as the values of the applied loads reach a limiting state. Lateral-torsional buckling failure occurs suddenly in beam-column elements with a much greater in-plane bending stiffness than torsional or lateral bending stiffness. This study intends to establish a unique convenient closed-form equation that it can be used for calculating critical elastic lateraltorsional buckling load of beam-column in the presence of a known axial load. The presented equation includes first order bending distribution, the position of the loads acting transversely on the beam-column and mono-symmetry property of the section. Effects of axial loads, slenderness and load positions on lateral torsional buckling behavior of beam-columns are investigated. The proposed solutions are compared to finite element simulations where thin-walled shell elements including warping are used. Good agreement between the analytical and the numerical solutions is demonstrated. It is found out that the lateral-torsional buckling load of beam-columns with mono-symmetric sections can be determined by the presented equation and can be safely used in design procedures.

The Investigation of Treatment of Pistachio Processing Industrial Wastewater by Electrochemical Methods in Terms of Chemical Oxygen Demand and Total Phenol Removal

Alper Erdem Yilmaz,Baybars Ali Fil,Murat Tolga Yilmaz,Serkan Bayar,Zuhal Koksal The Korean Electrochemical Society 2024 Journal of electrochemical science and technology Vol.15 No.1

This work aims to investigate the efficiency of electrocoagulation (EC) of pistachio processing industrial wastewater (PPIW) using the continuous EC process. The tubular reactor made of stainless steel with an internal diameter of 60 mm was used as a cathode electrode. The effect of some parameters was examined on the removal of chemical oxygen demand (COD) and total phenols (TP) removal efficiency. The influences of the initial pH of wastewater (from 4 to 8), flow rate (from 25 to 125 mL/min), current density (from 7 to 21 mA/cm²), and supporting electrolyte type (NaCl, NaNO₃, and Na₂SO₄), supporting electrolyte concentration (from 10 to 100 mg/L NaCl) on removal efficiency were investigated to determine the best experimental conditions. The examination of the physico-chemical parameters during the EC treatment showed that the best removal efficiency was obtained under conditions where the flow rate was 25 mL/min (20 min reaction time), the pH value was 5.2, and the current density was 21 mA/cm² has set. Under these experimental conditions, COD and TP removal efficiency were found to be 75% and 97%, respectively, while energy consumption was 18.5 kW h/m³. The study results show that the EC can be applied to PPIW pre-treatment.

Slide Session : OS-NEP-07 ; Nephrology : Effect of Donor Kidney Volume on Graft Functions in Living Donor Kidney Transplantation: 5 Years Follow Up

( Tolga Yildirim ),( Hadim Akoglu ),( Rahmi Yilmaz ),( Gonca Eldem ),( Tuncay Hazirolan ),( Tuncay Aki ),( Mustafa Arici ),( Bulent Altun ),( Yunus Erdem ) 대한내과학회 2014 대한내과학회 추계학술발표논문집 Vol.2014 No.1

Background: Immunosuppressive protocols decreased the rates of acute rejection in kidney transplantation however long term graft survival has not changed signifi cantly. Nephron underdosing may be one of the factors affecting the long term prognosis of the transplanted kidney. Aim of this study was to determine the impact of volume of transplanted kidney on long term allograft functions. Methods: The study was conducted among sixty-two living renal transplant recipients (41 male, 21 female; mean age 30.6±10.2 years) who underwent transplantation between years 2003-2007 and their respective donors (22 male, 40 female; age 41.9±9.9 years). Patients that suffered graft loss due to any cause within fi ve years after transplantation were excluded. Volume of the transplanted kidneys had been measured preoperatively via 3-D helical computerized tomography. Transplanted kidney volume/ recipient weight (Vol/weight) was calculated for each donor-recipient pair. Subjects were divided into two groups according to the median value of Vol/weight (2.35 cm3/ kg). Glomerular fi ltration rates (GFR) of the recipients were calculated for fi ve years. Results: First and third year GFR`s of the patients was significantly higher in Vol/ weight>2.35 cm3/kg group compared to Vol/weight<2.35 cm3/kg group (73.7±17.6 vs. 61.6±19.3, p=0.01 and 72.3±20.7 vs. 60.0±17.3, p=0.01 respectively). However fi fth year GFR was similar in both groups (64.5±16.9 and 56.6±21.7, p=0.11). There was a signifi cant correlation between Vol/weight and both fi rst and third year GFR`s (r=0.409, p<0.001 and r=0.429, p<0.001; respectively). The correlation was not observed with the fi fth year GFR (r=0.133, p=0.303). Conclusions: Volume of transplanted kidney adjusted for recipient weight is a signifi - cant predictor of early but not late graft functions.

Can Propofol Lead to an Increase in Seizure Threshold Over the Course of Electroconvulsive Therapy?

Hande Gurbuz Aytuluk,Tahsin Simsek,Mehmet Yilmaz,Ayse Zeynep Turan,Kemal Tolga Saracoglu 대한정신약물학회 2019 CLINICAL PSYCHOPHARMACOLOGY AND NEUROSCIENCE Vol.17 No.4

Objective: To evaluate the effects of 2 different dose regimens of propofol (low dose: < 1 mg/kg, high dose: ≥ 1 mg/kg) on the duration of the seizures, the required energy for the seizures, and the seizure threshold over the course of electroconvulsive therapy (ECT). Methods: The electronic medical records of 165 patients receiving 971 sessions of ECT were analyzed retrospectively. Patients were evaluated in two groups according to the according to propofol doses that they had received for ECT. Group LP (n = 91): patients who received low dose propofol (< 1 mg/kg). Group HP (n = 74): patients who received high dose propofol (≥ 1 mg/kg). Results: The required energy for seizures in Group HP were significantly higher than the Group LP in the 3rd, 4th, 5th, 6th, 7th, 8th, and 9th sessions (p < 0.05). The duration of seizures in the Group HP were significantly lower than the Group LP in the 1st, 2nd, 4th, 5th, 7th, and 8th sessions (p < 0.05). Higher electrical stimulus was needed to acquire a minimum length of seizure (> 25 sn) during the course of ECT in higher propofol doses. Although there was an increase in the seizure threshold over the course of ECT in both groups, this increase was found to be much more pronounced in the high-dose propofol group according to the low-dose propofol group. Longer duration of seizures was observed in the low-dose propofol group. Conclusion: Higher doses of propofol in induction of anesthesia can lead to a more progressive rise in seizure threshold than lower doses of propofol.

Experimental and numerical investigation of RC column strengthening with CFRP strips subjected to low-velocity impact load

Omer Mercimek,Ozgur Anil,Rahim Ghoroubi,Shaimaa Sakin,Tolga Yilmaz 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.79 No.6

Reinforced concrete (RC) square columns are vulnerable to sudden dynamic impact loadings such as the vehicle crash to the bridges of highway or seaway, rock fall, the collision of masses with the effect of flood and landslide. In this experimental study RC square columns strengthened with and without CFRP strip subjected to sudden low velocity lateral impact loading were investigated. Drop-hammer testing machine was used to apply the impact loading to RC square columns. The test specimens were manufactured with square cross sections with 1/3 geometric scale. In scope of the study, 6 test specimens were manufactured and tested. The main variables considered in the study were the application point of impact loading, and CFRP strip spacing. A 9.0 kg mass was allowed to fall freely from a height of 1.0 m to apply the impact loading on the columns. During the impact tests, accelerations, impact force, column mid-point displacements and CFRP strip strains measurements were taken. The general behavior of test specimens, collapse mechanisms, acceleration, displacement, impact load and strain time relationships were interpreted, and the load displacement relationships were obtained. The data from the experimental study was used to investigate the effect of variables on the impact performances of RC columns. It has been observed that the strengthening method applied to reinforced concrete columns, which are designed with insufficient shear strength, insufficient shear reinforcement and produced with low strength concrete, using CFRP strips significantly improves the behavior of the columns under the effect of sudden dynamic impact loading and increases their performance. As a result of the increase in the hardness and rigidity of the specimens strengthened by wrapping with CFRP strips, the accelerations due to the impact loading increased, the displacements decreased and the number of shear cracks formed decreased and the damage was limited. Moreover, the finite element analyses of tested specimens were performed using ABAQUS software to further investigate the impact behavior.

Could the Platelet-to-Lymphocyte Ratio be a Novel Marker for Predicting Invasiveness of Cervical Pathologies?

Kose, Mesut,Celik, Fatih,Kose, Seda Kayman,Arioz, Dagistan Tolga,Yilmazer, Mehmet Asian Pacific Journal of Cancer Prevention 2015 Asian Pacific journal of cancer prevention Vol.16 No.3

Purpose: To determine whether the preoperative platelet to lymphocyte ratio (PLR) could predict invasiveness of cervical pathologies. Materials and Methods: Patients with preinvasive and invasive diseases were reviewed retrospectively, over a nine-year period, 2005-2014. The pathological records and completed blood counts of the patients were collected and recorded in the SPSS program. Patients were divided in two groups, preinvasive and invasive. Results: The median PLR was significantly higher in the invasive group than in the preinvasive group (p=0.03). There was a correlation between invasion of cervical cancer and white blood cell count, red cell distributing width (RDW), neutrophil-lymphocyte ratio (NLR), and PLR. Conclusions: This study showed that patients with uterine cervical cancer may present with leukocytosis, increased RDW, NLR and PLR. These cheap and easily available parameters, especially PLR, may provide useful information about the invasiveness of cervical lesions.