Experimental Investigation of Impact Behaviour of RC Slab with Different Reinforcement Ratios

Tolga Yılmaz,Nevzat Kıraç,Özgür ANIL,R. Tuğrul Erdem,Gökhan Kaçaran 대한토목학회 2020 KSCE Journal of Civil Engineering Vol.24 No.1

Reinforced concrete (RC) slabs may be exposed to the low-velocity impact load during their service periods. In low-velocity impact scenarios, the effect of strain rates has been remarkably higher than quasi-static loading because the loading duration is very short. Thus, structural responses and failure modes will be different. The present study aims to investigate dynamic response and failure modes of simply supported two-way RC slabs exposed to low-velocity impact load. In the experimental part of this study, nine RC slabs with the dimension of 1,000 × 1,000 × 80 mm were tested. The reinforcement ratio of RC slabs and the input impact energy applied to RC slabs were experimental variables investigated. A drop-weight test setup was utilized to apply impact load to RC slabs. By varying drop-height as 1,000, 1,250 and 1,500 mm, three different impact energies have been applied to RC slabs via a hammer of which weight is 84 kg. The time histories of the accelerations, displacements and impact loads were recorded. The dynamic responses obtained by tests and the failure modes observed has been interpreted in detail. Besides, a finite element model where explicit dynamic analysis is performed has been established for verification of the experimental results. There was observed good accordance between numerical and experimental results. Consequently, it is considered that the present finite element treatment can be used for the evaluation of the dynamic responses and failure modes of RC slabs exposed to low-velocity impact load.

Low velocity impact behavior of shear deficient RC beam strengthened with CFRP strips

Özgür Anıl,Tolga Yılmaz 국제구조공학회 2015 Steel and Composite Structures, An International J Vol.19 No.2

Many methods are developed for strengthening of reinforced concrete structural members against the effects of shear. One of the commonly used methods in recent years is turned out to be bonding of fiber reinforced polymers (FRP). Impact loading is one of the important external effects on the reinforced concrete structural members during service period among the others. The determination of magnitude, the excitation time, deformations and stress due to impact loadings are complicated and rarely known. In recent year impact behavior of reinforced concrete members have been researched with experimental studies by using drop-weight method and numerical simulations are done by using finite element method. However the studies on the strengthening of structural members against impact loading are very seldom in the literature. For this reason, in this study impact behavior of shear deficient reinforced concrete beams that are strengthened with carbon fiber reinforced polymers (CFRP) strips are investigated experimentally. Compressive strength of concrete, CFRP strips spacing and impact velocities are taken as the variables in this experimental study. The acceleration due to impact loading is measured from the specimens, while velocities and displacements are calculated from these measured accelerations. RC beams are modeled with ANSYS software. Experimental result and simulations result are compared. Experimental result showed that impact behaviors of shear deficient RC beams are positively affected from the strengthening with CFRP strip. The decrease in the spacing of CFRP strips reduced the acceleration, velocity and displacement values measured from the test specimens.

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.

The effect of local application of thymoquinone, Nigella sativa’s bioactive component, on bone healing in experimental bone defects infected with Porphyromonas gingivalis

Ayşe Yılmaz Baştuğ,Ceyda Özçakır Tomruk,Elif Güzel,İlkay Özdemir,Gonca Duygu,Esma Kütan,Gül Merve Yalçın Ülker,Fatma Özen Arıcı 대한치주과학회 2022 Journal of Periodontal & Implant Science Vol.52 No.3

Purpose: This study was performed to evaluate the influence of local application of thymoquinone (TQ) on bone healing in experimental bone defects infected with Porphyromonas gingivalis (PG). Methods: Forty-two female rats were randomly divided into 6 groups. A bone defect was created on the right tibia of all animals. The PG, PG/collagen membrane (COL) and PG/ TQ/COL groups were infected with PG. In the COL and PG/COL groups, the defects were covered with a COL; in the TQ/COL and PG/TQ/COL groups, the defects were covered with a TQ-containing COL. After 28 days, all animals were sacrificed. Quantitative measurements of new bone formation and osteoblast lining, as well as semiquantitative measurements of capillary density and tissue response, were analyzed. Furthermore, the presence of bacterial infections in defect areas was evaluated. Results: The new bone formation, osteoblast number, and capillary density were significantly higher in the TQ groups than in the control groups (P<0.001, P<0.001, and P<0.01, respectively). In a comparison between the TQ/COL group, with a TQ-containing COL (TQ/COL), and the PG–infected TQ-containing COL (PG/TQ/COL) group, the newly formed bone and capillary density were higher in the TQ/COL group (P<0.01). When the control group was compared to the PG, PG/COL, and PG/TQ/COL groups in terms of tissue response, the differences were statistically significant (P<0.001, P=0.02, and P=0.041, respectively). The intensity of the inflammatory cell reaction was higher in the PG, PG/COL, and PG/TQ/COL groups (P<0.05). Conclusions: Within the limitations of this study, the local application of a TQ-containing COL positively affected bone healing even if the bone defects were infected. The results suggest that TQ increased angiogenesis and showed promise for accelerating bone defect healing. Further research is warranted to support these findings and reach more definitive conclusions.

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.

Reliability of Fossae Lumbales Laterales and Pelvic Incidence for Estimating Transsacral Corridors Assessed Using Reconstruction Computed Tomography

Orhan Balta,Mehmet Akif Yılmaz,Kürşad Aytekin,Recep Kurnaz,Harun Altinayak,Mehmet Burtaç Eren,Eyüp Çağatay Zengin 대한정형외과학회 2022 Clinics in Orthopedic Surgery Vol.14 No.3

Background: The present study aimed to evaluate the effect of fossae lumbales laterales and pelvic incidence (PI) on transsacral corridors. Methods: Patients who underwent pelvic computed tomography (CT) during routine therapy in a single center between 2015 and 2020 were retrospectively reviewed. The patients’ age and sex were documented during CT examination. Measurements were performed for both the upper and second sacral segments. Height and weight of the patients were determined using appropriate tools and body mass index (BMI) was calculated. Transsacral corridors were identified in true coronal and true sagittal planes and their width was determined as the maximum gap measured so that no screws could come out of the transacral corridors. PI was measured. Results: Our study included 244 (57%) male and 184 (43%) female patients, who had a mean age of 49.3 ± 14.15 years (range, 18–89 years) and a mean BMI of 26.57 ± 2.38 kg/m2. No statistically significant correlation was found between the detection of the dimple sign in physical examination and the presence of an adequate corridor. The PI was statistically significantly higher in the patients with dimples (p < 0.001). PI of the female patients was higher than that of the male patients (p = 0.026). The correlation between PI and the existence of adequate corridors for S1 and S2 screws was not statistically significant (p = 0.858 and p = 0.129, respectively). On the relationship between the presence of adequate S1 and S2 corridors where transsacral screws could be sent, an inverse relationship was detected: if the S1 transsacral corridor was adequate, the S2 corridor was inadequate or vice versa. Conclusions: We could not obtain meaningful results on the use of the dimples of Venus or PI instead of CT to evaluate the adequacy of transverse corridors. Nevertheless, we confirmed that an increased PI was associated with the presence of dimples of Venus.

3D virtual learning environments in education: a meta-review

I. Reisoğlu,B. Topu,R. Yılmaz,T. Karakuş Yılmaz,Y. Göktaş 서울대학교 교육연구소 2017 Asia Pacific Education Review Vol.18 No.1

The aim of this study is to investigate recent empirical research studies about 3D virtual learning environments. A total of 167 empirical studies that involve the use of 3D virtual worlds in education were examined by meta-review. Our findings show that the “Second Life” platform has been frequently used in studies. Among the reviewed papers, case study designs and quasi-experimental studies were more common. Sample sizes were below 100 for most studies. 3D virtual learning environments are mainly designed for learning support, simulation, and game. Language learning and science have been the most extensively studied topics. Collaborative and exploration-based learning strategies have been used most frequently in 3D virtual learning environments. Presence, satisfaction, communication skills, and engagement were examined as emotional and cognitive achievements.

Three-dimensional evaluation of alveolar changes induced by nasoalveolar molding in infants with unilateral cleft lip and palate: A case-control study

Merve Altay Burgaz,Derya Germec Cakan,R. Burcu Nur Yılmaz 대한치과교정학회 2019 대한치과교정학회지 Vol.49 No.5

Objective: The objectives of this study were to evaluate linear and volumetric alveolar changes induced by nasoalveolar molding (NAM) in infants with complete unilateral cleft lip and palate (UCLP) and compare the maxillary dimensions after NAM with the normal dimensions in infants without clefts. Methods: A total of 26 infants with UCLP treated by NAM (mean age before and after NAM: 14.20 ± 8.09 days and 118.16 ± 10.06 days, respectively) comprised the treatment group, while 26 infants without clefts (mean age: 115.81 ± 8.71 days) comprised the control group. Changes in the maxillary dimensions following NAM were measured on three-dimensional models using Mimics software, version 17.0. Results: During NAM, there was a decrease in the cleft widths, maxillary arch depths, and rotation of the greater segment. While the anterior alveolar arch width exhibited a significant decrease, the posterior arch width was mostly maintained. There were no changes in the anterior vertical deviations of the alveolar segments. The alveolar crest lengths, arch circumference, and bilateral posterior volumetric measures exhibited an increase. After NAM, the anterior arch width was comparable between the treatment and control groups, whereas the posterior arch width and anterior vertical deviations were greater in the treatment group than in the control group. The maxillary arch depths, alveolar crest lengths, and maxillary volumes were smaller in the NAM group than in the control group. Conclusions: During NAM in infants with UCLP, the cleft width and anteroposterior and transverse alveolar dimensions exhibited a decrease while the vertical dimensions were maintained. Compared with infants without clefts, those with UCLP treated by NAM exhibited sagittal and vertical alveolar growth deficiencies and tissue insufficiency.

Evaluation of biogeneric design techniques with CEREC CAD/CAM system

Yeliz Arslan,Secil Karakoca Nemli,Merve Bankoğlu Güngör,Evsen Tamam,Handan Yılmaz 대한치과보철학회 2015 The Journal of Advanced Prosthodontics Vol.7 No.6

PURPOSE. The aim of this study was to evaluate occlusal contacts generated by 3 different biogeneric design modes (individual (BI), copy (BC), reference (BR)) of CEREC software and to assess the designs subjectively. MATERIALS AND METHODS. Ten pairs of maxillary and mandibular casts were obtained from full dentate individuals. Gypsum cast contacts were quantified with articulating paper and digital impressions were taken. Then, all ceramic crown preparation was performed on the left first molar teeth and digital impressions of prepared teeth were made. BI, BC, and BR crowns were designed. Occlusal images of designs including occlusal contacts were superimposed on the gypsum cast images and corresponding contacts were determined. Three designs were evaluated by the students. RESULTS. The results of the study revealed that there was significant difference among the number of contacts of gypsum cast and digital models (P<.05). The comparison of the percentage of virtual contacts of three crown designs which were identical to the contacts of original gypsum cast revealed that BI and BR designs showed significantly higher percentages of identical contacts compared with BC design (P<.05). Subjective assessment revealed that students generally found BI designs and BR designs natural regarding naturalness of fissure morphology and cusp shape and cusp tip position. For general occlusal morphology, student groups generally found BI design "too strong" or "perfect", BC design "too weak", and BR design "perfect". CONCLUSION. On a prepared tooth, three different biogeneric design modes of a CAD/CAM software reveals different crown designs regarding occlusal contacts and morphology.

On the Severity of Carpal Tunnel Syndrome: Diabetes or Metabolic Syndrome

Fatma Gul Yurdakul,Hatice Bodur,Özgu¨r Öztop Çakmak,Filiz Sivas,Filiz Eser,Özlem Yılmaz Taşdelen 대한신경과학회 2015 Journal of Clinical Neurology Vol.11 No.3

Background and Purpose Carpal tunnel syndrome (CTS) is the most common entrapment neuropathy. Although its etiology is unknown, certain conditions are commonly associated with CTS, such as obesity, arthritis, hypothyroidism, diabetes mellitus, trauma, mass lesions, amyloidosis, and sarcoidosis. We aimed to determine the association between metabolic syndrome and CTS, and we compared the severity of CTS between patients with diabetes (and no concomitant metabolic syndrome) and patients with metabolic syndrome. Methods Two hundred patients with a clinically and electrophysiological confrmed diagnosis of CTS were included in the study. Teir demographic characteristics and severity of CTS were analyzed according to the presence or the absence of metabolic syndrome. Diferences in the electrophysiological fndings were evaluated between the following four groups: 1) metabolic syndrome alone (n=52), 2) diabetes alone (n=20), 3) combined metabolic syndrome and diabetes (n=44), and 4) no metabolic syndrome or diabetes (n=84). Results CTS was more severe in the patients with metabolic syndrome than those without this syndrome. Te electrophysiological fndings were worse in patients with metabolic syndrome alone than in those with diabetes alone and those without diabetes and metabolic syndrome. Conclusions CTS appears to be more severe in patients with metabolic syndrome than patients with diabetes. Diabetes is one of the well-known risk factors for CTS, but other components of metabolic syndrome may have a greater efect on the severity of CTS.