Experimental investigation of impact behaviour of shear deficient RC beam to column connection

Murat Aras,Tolga Yılmaz,Özlem Çalışkan,Özgür Anıl,R. Tuğrul Erdem,Turgut Kaya 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.84 No.5

Reinforced concrete (RC) structures may be subjected to sudden dynamic impact loads such as explosions occurring for different reasons, the collision of masses driven by rockfall, flood, landslide, and avalanche effect structural members, the crash of vehicles to the highway and seaway structures. Many analytical, numerical, and experimental studies focused on the behavior of RC structural elements such as columns, beams, and slabs under sudden dynamic impact loads. However, there is no comprehensive study on the behavior of the RC column-beam connections under the effect of sudden dynamic impact loads. For this purpose, an experimental study was performed to investigate the behavior of RC column-beam connections under the effect of low-velocity impact loads. Sixteen RC beam-column connections with a scale of 1/3 were manufactured and tested under impact load using the drop-weight test setup. The concrete compressive strength, shear reinforcement spacing in the beam, and input impact energy applied to test specimens were taken as experimental variables. The time histories of impact load acting on test specimens, accelerations, and displacements measured from the test specimens were recorded in experiments. Besides, shear and bending crack widths were measured. The effect of experimental variables on the impact behavior of RC beam-column connections has been determined and interpreted in detail. Besides, a finite element model has been established for verification and comparison of the experimental results by using ABAQUS software. It has been demonstrated that concrete strength, shear reinforcement ratio, and impact energy significantly affect the impact behavior of RC column-beam connections.

Estimation of Dissolved Oxygen by using Neural Networks and Neuro Fuzzy Computing Techniques

Murat AY,Özgür Kisi 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.5

Dissolved oxygen, one of the most important water quality parameters, is a crucial parameter for the aquatic ecosystems. In this study, some advanced chemometric techniques included in a multi-layer perceptron, radial basis neural network, and two different adaptive neuro-fuzzy inference system methods are developed to model dissolved oxygen concentration. Moreover the estimations of these models are compared with the multiple linear regression. In this context, monthly mean quantities of the temperature, pH, electrical conductivity, discharge and dissolved oxygen data recorded at Broad River near Carlisle, SC in USA are used. The accuracy of the models is compared with one other by using determination coefficient, mean absolute error, root mean square error and mean absolute relative error statistics. Results indicate that radial basis neural network method performs better than the other methods in modelling monthly mean dissolved oxygen concentration. The temperature, pH, electrical conductivity, and discharge are found to be effective on dissolved oxygen concentration.

Strain distribution between CFRP strip and concrete at strengthened RC beam against shear

Özgür Anil,Nalan Bulut,Murat Ayhan 국제구조공학회 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.41 No.4

In recent years, CFRP material usage in strengthening applications gradually became widespread. Especially, the studies on the strengthening of shear deficient reinforced concrete beams with CFRP strips are chosen as a subject to numerous experimental studies and research on this subject are increased rapidly. The most important variable, that is affected on the failure mode of CFRP strips and that is needed for determining the shear capacity of the strengthened reinforced concrete beams, is the strain distribution between CFRP strips and concrete. Numerous experimental studies are encountered in the literature about the determination of strain distribution between CFRP strips and concrete. However, these studies mainly focused on the CFRP strips under axial tension. There are very limited numbers of experimental and analytic studies examining the strain distribution between concrete and CFRP strips, which are under combined stresses due to the effects of shear force and bending moment. For this reason, existing experimental study in the literature is used as model for ANSYS finite element software. Nonlinear finite element analysis of RC beams strengthened against shear with CFRP strips under reverse cyclic loading is performed. The strain distributions between CFRP strips and concrete that is obtained from finite element analysis are compared with the results of experimental measurements. It is seen that the experimental results are consisted with the results derived from the finite element analysis and important findings on the strain distribution profile are reached by obtaining strain values of many points using finite element method.

Uric acid albumin ratio as a predictive marker of short-term mortality in patients with acute kidney injury

Yasemin Özgür,Seydahmet Akın,Nuran Gamze Yılmaz,Murat Gücün,Özcan Keskin 대한응급의학회 2021 Clinical and Experimental Emergency Medicine Vol.8 No.2

Objective We aimed to investigate uric acid and albumin ratio (UA/A) as a marker of short-term mortality in acute kidney injury (AKI). Both uric acid and albumin are strongly correlated with the development and mortality of AKI. Methods The patients hospitalized from May 2019 to September 2019 for AKI were included in this study. The diagnostic odds ratio (DOR), Youden index (J), and the area under a receiver operating characteristic curve (AUROC) determined a cut-off UA/A ratio for mortality. Cox-regression analysis was performed to identify UA/A as a prognostic marker of the 30-day mortality rate. Results A total of 171 patients with an average age of 69.20±13.0 (45.6% women) were included in the study. The average UA/A ratio was 3.3±1.5 mg/g and 2.5±1.0 mg/g in the non-survivor and survivor groups, respectively (P=0.001). The best cut-off UA/A ratio associated with mortality was determined as 2.4 mg/g with a specificity of 52% and a sensitivity of 77% (DOR, 3.6; J, 28.8; AUROC, 0.644). Thirty-day cumulative survival rates of the low and high UA/A ratio groups were 85.9±4.0% and 63.7±5.0%, respectively. The estimated survival times of the low and high UA/A ratio groups were 27.7 days (95% confidence interval [CI], 26.2–29.3) and 23.9 days (95% Cl, 22.0–25.9), respectively. Conclusion We found a direct correlation between 30-day mortality and UA/A ratio at initial presentation in AKI patients regardless of age, comorbidities, and clinical and laboratory findings, including albuminuria.

Transformation of marriage migrants to diasporic actors and rethinking female agency: Ukrainian women in Türkiye

Deniz Ayla,Özgür Ertuğrul Murat 이화여자대학교 아시아여성학센터 2024 Asian Journal of Women's Studies(AJWS) Vol.30 No.1

This article investigates the transformation of Ukrainian female marriage migrants in Türkiye into diasporic actors. This role as diasporic actors represents a unique aspect of female agency, and its impact on migrant women and the diaspora is discussed. The representatives of the hometown associations (HTAs) were interviewed, the activities of the HTAs were tracked, and their social media posts were examined. The findings reveal that when women became diasporic actors, they influenced community politics on a large scale and created multiple networks. It has also been found that migrants strengthened the institutional structures of the HTAs by using these networks. Moreover, through their approach of bringing different groups together, they created a diaspora composition where hierarchy in representation is not explicit.

Seismic responses of base-isolated buildings: efficacy of equivalent linear modeling under near-fault earthquakes

Cenk Alhan,Murat Özgür 국제구조공학회 2015 Smart Structures and Systems, An International Jou Vol.15 No.6

Design criteria, modeling rules, and analysis principles of seismic isolation systems have already found place in important building codes and standards such as the Uniform Building Code and ASCE/SEI 7-05. Although real behaviors of isolation systems composed of high damping or lead rubber bearings are nonlinear, equivalent linear models can be obtained using effective stiffness and damping which makes use of linear seismic analysis methods for seismic-isolated buildings possible. However, equivalent linear modeling and analysis may lead to errors in seismic response terms of multi-story buildings and thus need to be assessed comprehensively. This study investigates the accuracy of equivalent linear modeling via numerical experiments conducted on generic five-story three dimensional seismic-isolated buildings. A wide range of nonlinear isolation systems with different characteristics and their equivalent linear counterparts are subjected to historical earthquakes and isolation system displacements, top floor accelerations, story drifts, base shears, and torsional base moments are compared. Relations between the accuracy of the estimates of peak structural responses from equivalent linear models and typical characteristics of nonlinear isolation systems including effective period, rigid-body mode period, effective viscous damping ratio, and post-yield to pre-yield stiffness ratio are established. Influence of biaxial interaction and plan eccentricity are also examined.

Reliability of chest pain risk scores in cancer patients with suspected acute coronary syndrome

Cansu Alyeşil,Serkan Yilmaz,İbrahim Ulaş Özturan,Murat Pekdemir,Elif Yaka,Nurettin Özgür Doğan 대한응급의학회 2020 Clinical and Experimental Emergency Medicine Vol.7 No.4

Objective The history, electrocardiogram, age, risk factors, troponin (HEART), the thrombolysis in myocardial infarction (TIMI), and Global Registry of Acute Coronary Events (GRACE) scores are useful risk stratification tools in the emergency department (ED). However, the accuracy of these scores in the cancer population is not well known. This study aimed to compare the performance of cardiac risk stratification scores in cancer patients with suspected acute coronary syndrome (ACS) in the ED. Methods This prospective cohort study recruited patients with cancer who visited the ED because of suspected ACS. The development of any major adverse cardiac events (MACE) within 6 weeks was recorded, with the study outcome being a MACE within 6 weeks of ED admission. Results A total of 178 patients participated in this study, of whom 5.6% developed a MACE. Statistically significant differences were found between the mean HEART and TIMI scores in predicting MACE. The HEART score had the highest area under the curve (0.64; 95% confidence interval, 0.48–0.81), highest sensitivity (80%), and highest negative predictive value (97.5) in patients with cancer. Conclusion We found a similar rate of MACE in cancer patients with low-risk chest pain compared to that in the general population. However, the HEART, TIMI, and GRACE scores had a lower performance in cancer patients with MACE compared to that in the general population.

Impact of lymph node ratio on survival in stage IIIC endometrioid endometrial cancer: a Turkish Gynecologic Oncology Group study

Ali Ayhan,Nazlı Topfedaisi Ozkan,Murat Özdemir,Günsu Kimyon Comert,Zeliha Firat Cuylan,Gonca Çoban,Osman Turkmen,Baki Erdem,Hanifi Şahin,Özgür Akbayır,Murat Dede,Ahmet Taner Turan,Husnu Celik,Tayfun G 대한부인종양학회 2018 Journal of Gynecologic Oncology Vol.29 No.4

OBJECTIVE: The purpose of this study was to investigate the prognostic value of lymph node ratio (LNR) in women with stage IIIC endometrioid endometrial cancer (EC). METHODS: A multicenter, retrospective department database review was performed to identify patients with stage IIIC pure endometrioid EC at 6 gynecologic oncology centers in Turkey. A total of 207 women were included. LNR, defined as the percentage of positive lymph nodes (LNs) to total nodes recovered, was stratified into 2 groups: LNR1 (≤0.15), and LNR2 (>0.15). Kaplan-Meier method was used to generate survival data. Factors predictive of outcome were analyzed using Cox proportional hazards models. RESULTS: One hundred and one (48.8%) were classified as stage IIIC1 and 106 (51.2%) as stage IIIC2. The median age at diagnosis was 58 (range, 30-82) and the median duration of follow-up was 40 months (range, 1-228 months). There were 167 (80.7%) women with LNR ≤0.15, and 40 (19.3%) women with LNR >0.15. The 5-year progression-free survival (PFS) rates for LNR ≤0.15 and LNR >0.15 were 76.1%, and 58.5%, respectively (p=0.045). An increased LNR was associated with a decrease in 5-year overall survival (OS) from 87.0% for LNR ≤0.15 to 62.3% for LNR >0.15 (p=0.005). LNR >0.15 was found to be an independent prognostic factor for both PFS (hazard ratio [HR]=2.05; 95% confidence interval [CI]=1.07-3.93; p=0.03) and OS (HR=3.35; 95% CI=1.57-7.19; p=0.002). CONCLUSION: LNR seems to be an independent prognostic factor for decreased PFS and OS in stage IIIC pure endometrioid EC.

Decellularization of Trachea With Combined Techniques for Tissue-Engineered Trachea Transplantation

Aysegul Batioglu-Karaaltin,Ercüment Ovali,Mehmet V Karaaltin,Murat Yener,Mehmet Yılmaz,Fatma Eyüpoğlu,Yetkin Zeki Yılmaz,Erol Rüştü Bozkurt,Necdet Demir,Esma Konuk,Ergun Süreyya Bozdağ,Özgür Yiğit,Har 대한이비인후과학회 2019 Clinical and Experimental Otorhinolaryngology Vol.12 No.1

Objectives. The purpose of this study is to shorten the decellularization time of trachea by using combination of physical, chemical, and enzymatic techniques. Methods. Approximately 3.5-cm-long tracheal segments from 42 New Zealand rabbits (3.5±0.5 kg) were separated into seven groups according to decellularization protocols. After decellularization, cellular regions, matrix and strength and endurance of the scaffold were followed up. Results. DNA content in all groups was measured under 50 ng/mg and there was no significant difference for the glycosaminoglycan content between group 3 (lyophilization+deoxycholic acid+de-oxyribonuclease method) and control group (P=0.46). None of the decellularized groups was different than the normal trachea in tensile stress values (P>0.05). Glucose consumption and lactic acid levels measured from supernatants of all decellularized groups were close to group with cells only (76 mg/dL and 53 mg/L). Conclusion. Using combination methods may reduce exposure to chemicals, prevent the excessive influence of the matrix, and shorten the decellularization time.

Impact of lymph node ratio on survival in stage III ovarian high-grade serous cancer: a Turkish Gynecologic Oncology Group study

Ali Ayhan,Nazlı Topfedaisi Ozkan,Mustafa Erkan Sarı,Husnu Celik,Murat Dede,Özgür Akbayır,Kemal Güngördük,Hanifi Şahin,Ali Haberal,Tayfun Güngör,Macit Arvas,Mehmet Mutlu Meydanlı 대한부인종양학회 2018 Journal of Gynecologic Oncology Vol.29 No.1

Objective: The purpose of this study was to investigate the prognostic value of lymph node ratio (LNR) in patients with stage III ovarian high-grade serous carcinoma (HGSC). Methods: A multicenter, retrospective department database review was performed to identify patients with ovarian HGSC at 6 gynecologic oncology centers in Turkey. A total of 229 node-positive women with stage III ovarian HGSC who had undergone maximal or optimal cytoreductive surgery plus systematic lymphadenectomy followed by paclitaxel plus carboplatin combination chemotherapy were included. LNR, defined as the percentage of positive lymph nodes (LNs) to total nodes recovered, was stratified into 3 groups: LNR1 (<10%), LNR2 (10%≤LNR<50%), and LNR3 (≥50%). Kaplan-Meier method was used to generate survival data. Factors predictive of outcome were analyzed using Cox proportional hazards models. Results: Thirty-one women (13.6%) were classified as stage IIIA1, 15 (6.6%) as stage IIIB, and 183 (79.9%) as stage IIIC. The median age at diagnosis was 56 (range, 18–87), and the median duration of follow-up was 36 months (range, 1–120 months). For the entire cohort, the 5-year overall survival (OS) was 52.8%. An increased LNR was associated with a decrease in 5-year OS from 65.1% for LNR1, 42.5% for LNR2, and 25.6% for LNR3, respectively (p<0.001). In multivariate analysis, women with LNR≥0.50 were 2.7 times more likely to die of their tumors (hazard ratio [HR]=2.7; 95% confidence interval [CI]=1.42–5.18; p<0.001). Conclusion: LNR seems to be an independent prognostic factor for decreased OS in stage III ovarian HGSC patients.