A reliable approach for determining concrete strength in structures by using cores

Ayşegül Durmuş,Hasan Tahsin Öztürk,Ahmet Durmuş 사단법인 한국계산역학회 2013 Computers and Concrete, An International Journal Vol.11 No.5

As known, concrete classes are described as strength of standard specimens produced and kept in ideal conditions, not including reinforcement and not subjected to any load effect before. Under the circumstances, transforming core strengths to the standard specimen strength is necessary and considering all parameters, affected on the core strength, is inevitable. In fact, effects of the reinforcement and the load history on concrete strength are generally neglected when these mentioned transforms are performing. The main purpose of this paper is investigating the effects of the reinforcement and the load history on the core strength. This investigation is experimentally performed on cores drilled from specimens having different keeping conditions, reinforced, unreinforced, subjected to bending and central pressure in various proportions of failure load during specified periods. Obtained results show that the importance of these effects cannot be neglected.

Modal parameter identification of in-filled RC frames with low strength concrete using ambient vibration

Mehmet E. Arslan,Ahmet Durmuş 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.50 No.2

In this study, modal parameters such as natural frequencies, mode shapes and damping ratios ofRC frames with low strength are determined for different construction stages using ambient vibration test. For this purpose full scaled, one bay and one story RC frames are produced and tested for plane, brick infilledand brick in-filled with plaster conditions. Measurement time, frequency span and effective modenumber are determined by considering similar studies and literature. To obtain experimental dynamiccharacteristics, Enhanced Frequency Domain Decomposition and Stochastic Subspace Identificationtechniques are used together. It is shown that the ambient vibration measurements are enough to identify themost significant modes of RC frames. The results indicate that modal parameters change significantlydepending on the construction stages. In addition, Infill walls increase stiffness and change the mode shapesof the RC frame. There is a good agreement between mode shapes obtained from brick in-filled and in-filledwith plaster conditions. However, some differences are seen in plane frame, like expected. Dynamiccharacteristics should be verified using finite element analysis. Finally, inconsistency between experimentaland analytical dynamic characteristics should be minimize by finite element model updating using someuncertain parameters such as material properties, boundary condition and section properties to reflect thecurrent behavior of the RC frames.

Fuzzy logic approach for estimating bond behavior of lightweight concrete

Mehmet E. Arslan,Ahmet Durmuş 사단법인 한국계산역학회 2014 Computers and Concrete, An International Journal Vol.14 No.3

In this paper, a rule based Mamdani type fuzzy logic model for prediction of slippage at maximum tensile strength and slippage at rupture of structural lightweight concretes were discussed. In the model steel rebar diameters and development lengths were used as inputs. The FL model and experimental results, the coefficient of determination R2, the Root Mean Square Error were used as evaluation criteria for comparison. It was concluded that FL was practical method for predicting slippage at maximum tensile strength and slippage at rupture of structural lightweight concretes.

Construction stage effect on the dynamic characteristics of RC frame using operational modal analysis

Mehmet Emin Arslan,Ahmet Durmuş 사단법인 한국계산역학회 2013 Computers and Concrete, An International Journal Vol.12 No.1

In this study, dynamic characteristics such as natural frequencies, mode shapes and damping ratios of RC frame is determined for different construction stages using Operational Modal Analyses method under ambient vibration. Full scaled, one bay and one story RC frames are selected as an application for different construction stages such as plane, brick in-filled and brick in-filled with plaster. The RC frame is vibrated by natural excitations with small impact effects and the response signals are measured using sensitive accelerometers during ambient vibration tests. Measurement time-frequency span and effective mode number are determined by considering similar studies in literature. Sensitive seismic accelerometers are used to collect signals obtained from the experimental tests. To obtain experimental dynamic characteristics, output-only system identification technique is employed namely; Enhanced Frequency Domain Decomposition technique in the frequency domain. It is demonstrated that the ambient vibration measurements are enough to identify the most significant modes of RC frames.

Neutrophil to Lymphocyte Ratio Predicts Left Ventricular Remodeling in Patients with ST Elevation Myocardial Infarction treated with Primary Percutaneous Intervention

Abdurrezzak Börekçi,Mustafa Gür,Caner Türkoğlu,Ahmet Oytun Baykan,Taner Şeker,Durmuş Yıldıray Şahin,Hazar Harbalıoğlu,Zafer Elbasan,Mustafa Topuz,Murat Çaylı 대한심장학회 2016 Korean Circulation Journal Vol.46 No.1

Background and Objectives: It has been demonstrated that the neutrophil/lymphocyte ratio (NLR) might be a useful marker to predict cardiovascular risk and events. We aimed to investigate the role of the NLR to predict ventricular remodeling (VR) in patients with anterior ST-elevation myocardial infarction (STEMI) who were treated with primary percutaneous coronary intervention. Subjects and Methods: We prospectively included 274 consecutive anterior STEMI patients. Echocardiography was performed during admission and at six months after myocardial infarction. VR was defined as at least 20% increase from baseline in left ventricular end- diastolic volume. Patients were divided into two groups according to their VR status: VR (n=67) and non-VR (n=207). Total and differential leukocyte count, N-terminal pro-brain natriuretic peptide (NT-proBNP) and other biochemical markers were measured at admission and 24 hours later. Results: Compared with the non-VR group, peak creatine kinase MB (CK-MB), NT-proBNP (24 h), neutrophil/lymphocyte ratio, presence of diabetes, no-reflow frequency and wall motion score index were significantly higher in patients with VR (p<0.05 for all). On multivariate logistic regression analysis, NLR (β=2.000, 95% confidence interval=1.577-2.537, p<0.001) as well as peak CK-MB, NT-proBNP (24 h), WMSI and diabetes incidence were associated with VR. The cutoff value of the neutrophil/lymphocyte ratio obtained by receiver operator characteristic curve analysis was 4.25 for the prediction of VR (sensitivity: 79 %, specificity: 74%). Conclusion: In patients with anterior STEMI, initial NLR and NT-proBNP measured 24 hours after admission may be useful for predicting adverse cardiovascular events including left VR.

Investigation of bond behavior between lightweight aggregate concrete and steel rebar using bending test

Mehmet Emin Arslan,Ahmet Durmu 사단법인 한국계산역학회 2011 Computers and Concrete, An International Journal Vol.8 No.4

This paper investigates bond behavior of structural lightweight concrete (SLWC) and ordinary concrete (OC) comparatively using bending test called Standard Belgium Hinged Beam Test (SBHBT). For this purpose the experiments were carried out as three series on 36 beam specimens (12 specimens of SLWC and OC with 20φ development length, 12 specimens of SLWC with 25φ development length). For each series bond behavior of steel rebars with 8, 10, 12, 14 mm diameters were tested. The results indicate that bond strength of SLWC is considerable lower than OC and 20φ development length is insufficient for steel rebars with 12 mm and 14 mm diameters. Therefore development length of SLWC was extended to 25φ, even if 8 and 10 mm steel rebars provided acceptable bond strength. In this way, bond strength between SLWC and 8 and 10 mm steel rebars was developed. In addition, adequate bond behavior was achieved for 12 mm rebar but the beam in which 14 mm rebar used exceeded their bearing capacity by shear forces before yield stress. This result shows that SBHBT is more convenient for small sized steel rebars.