Stochastic responses of isolated bridge with triple concave friction pendulum bearing under spatially varying ground motion

Yurdakul, Muhammet,Ates, Sevket Techno-Press 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.65 No.6

This study aims to investigate the stochastic response of isolated and non-isolated highway bridges subjected to spatially varying earthquake ground motion model. This model includes wave passage, incoherence and site response effects. The wave passage effect is examined by using various wave velocities. The incoherency effect is investigated by considering the Harichandran and Vanmarcke coherency model. The site response effect is considered by selecting homogeneous firm, medium and soft soil types where the bridge supports are constructed. The ground motion is described by power spectral density function and applied to each support point. Triple concave friction pendulum (TCFP) bearing which is more effective than other seismic isolation systems is used for seismic isolation. To implement seismic isolation procedure, TCFP bearing devices are placed at each of the support points of the deck. In the analysis, the bridge selected is a five-span featuring cast-in-place concrete box girder superstructure supported on reinforced concrete columns. Foundation supported highway bridge is regarded as three regions and compared its different situation in the stochastic analysis. The stochastic analyses results show that spatially varying ground motion has important effects on the stochastic response of the isolated and non-isolated bridges as long span structures.

Structural repairing of damaged reinforced concrete beam-column assemblies with CFRPs

Yurdakul, Ozgur,Avsar, Ozgur Techno-Press 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.54 No.3

Depending on the damage type as well as the level of damage observed after the earthquake, certain measures should be taken for the damaged buildings. In this study, structural repairing of two different types of damaged RC beam-column assembly by carbon fiber-reinforced polymer sheets is investigated in detail as a member repairing technique. Two types of 1:1 scale test specimens, which represent the exterior RC beam-column connection taken from inflection points of the frame, are utilized. The first specimen is designed according to the current Turkish Earthquake Code, whereas the second one represents a deficient RC beam-column assembly. Both of the specimens were subjected to cyclic quasistatic loading in the laboratory and different levels of structural damage were observed. The first specimen displayed a ductile response with the damage concentrated in the beam. However, in the second specimen, the beam-column joint was severely damaged while the rest of the members did not attain their capacities. Depending on the damage type of the specimens, the damaged members were repaired by CFRP wrapping with different configurations. After testing the repaired specimens, it is found that former capacities of the damaged members were mostly recovered by the application of CFRPs on the damaged members.

Modeling of triple concave friction pendulum bearings for seismic isolation of buildings

Yurdakul, Muhammet,Ates, Sevket Techno-Press 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.40 No.3

Seismic isolated building structures are examined in this study. The triple concave friction pendulum (TCFP) is used as a seismic isolation system which is easy to be manufactured and enduring more than traditional seismic isolation systems. In the TCFP, take advantage of weight which pendulum carrying and it's geometry in order to obtain desirable result of seismic isolation systems. These systems offer advantage to buildings which subject to severe earthquake. This is result of damping force of earthquake by means of their internal constructions, which consists of multiple surfaces. As the combinations of surfaces upon which sliding is occurring change, the stiffness and effective friction change accordingly. Additionally, the mentioned the TCFP is modeled as of a series arrangement of the three single concave friction pendulum (SCFP) bearings. A two dimensional- and eight- story of a building with and without isolation system are used in the time history analysis in order to investigate of the effectiveness of the seismic isolation systems on the buildings. Results are compared with each other to emphasize efficiency of the TCFP as a seismic isolation device against the other friction type isolation system like single and double concave surfaces. The values of the acceleration, floor displacement and isolator displacement obtained from the results by using different types of the isolation bearings are compared each other. As a result, the findings show that the TCFP bearings are more effective devices for isolation of the buildings against severe earthquakes.

Modeling of triple concave friction pendulum bearings for seismic isolation of buildings

Muhammet Yurdakul,Sevket Ates 국제구조공학회 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.40 No.3

Seismic isolated building structures are examined in this study. The triple concave friction pendulum (TCFP) is used as a seismic isolation system which is easy to be manufactured and enduring more than traditional seismic isolation systems. In the TCFP, take advantage of weight which pendulum carrying and it’s geometry in order to obtain desirable result of seismic isolation systems. These systems offer advantage to buildings which subject to severe earthquake. This is result of damping force of earthquake by means of their internal constructions, which consists of multiple surfaces. As the combinations of surfaces upon which sliding is occurring change, the stiffness and effective friction change accordingly. Additionally, the mentioned the TCFP is modeled as of a series arrangement of the three single concave friction pendulum (SCFP) bearings. A two dimensional- and eight- story of a building with and without isolation system are used in the time history analysis in order to investigate of the effectiveness of the seismic isolation systems on the buildings. Results are compared with each other to emphasize efficiency of the TCFP as a seismic isolation device against the other friction type isolation system like single and double concave surfaces. The values of the acceleration, floor displacement and isolator displacement obtained from the results by using different types of the isolation bearings are compared each other. As a result, the findings show that the TCFP bearings are more effective devices for isolation of the buildings against severe earthquakes.

Sulfuric acid effect and application of freezing-thawing curing on long fiber reinforced metabentonite and slag-based geopolymer composites

Aygormez, Yurdakul Techno-Press 2021 Advances in concrete construction Vol.12 No.2

In this study, different types of metabentonite (MB) and slag (S)-based geopolymer were produced based on origin, polyvinyl alcohol (PVA) and basalt (B) fiber at different percentages of 0.2%, 0.4%, and 0.6%. A total of 7 series were produced. Two steps of curing method were applied for the samples, the first step was at room temperature from day 1-7, and the second step freezing-thawing from 8-28 days. Thus, the applicability of a curing method that used less energy instead of heat curing was investigated. Due to the freezing-thawing curing, the continuation of geopolymerization reactions was ensured and a compact structure was created. The produced samples were subjected to 10% sulfuric acid effect for 3 months after the 28th day. Compressive strength, flexural strength, ultrasonic pulse velocity (UPV), and weight losses due to acid effects were found. Despite the decrease in mechanical properties after the acid effect, the geopolymer products didn't experience easy dispersal because they had strong aluminosilicate bonds, crystalline phase formation, morphology, and lower calcium content that provided high stability. Also, SEM, XRD, FT-IR, and TGA-DTA analyzes and visual inspection resulting from the acid effect were examined.

Stochastic responses of isolated bridge with triple concave friction pendulum bearing under spatially varying ground motion

Muhammet Yurdakul,Sevket Ates 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.65 No.6

This study aims to investigate the stochastic response of isolated and non-isolated highway bridges subjected to spatially varying earthquake ground motion model. This model includes wave passage, incoherence and site response effects. The wave passage effect is examined by using various wave velocities. The incoherency effect is investigated by considering the Harichandran and Vanmarcke coherency model. The site response effect is considered by selecting homogeneous firm, medium and soft soil types where the bridge supports are constructed. The ground motion is described by power spectral density function and applied to each support point. Triple concave friction pendulum (TCFP) bearing which is more effective than other seismic isolation systems is used for seismic isolation. To implement seismic isolation procedure, TCFP bearing devices are placed at each of the support points of the deck. In the analysis, the bridge selected is a five-span featuring cast-in-place concrete box girder superstructure supported on reinforced concrete columns. Foundation supported highway bridge is regarded as three regions and compared its different situation in the stochastic analysis. The stochastic analyses results show that spatially varying ground motion has important effects on the stochastic response of the isolated and non-isolated bridges as long span structures.

Evaluating anchorage loss in upper incisors during distalization of maxillary posterior teeth using clear aligners in adult patients: A prospective randomized study

Zehra Yurdakul,Nurver Karsli 대한치과교정학회 2024 대한치과교정학회지 Vol.54 No.2

Objective: To evaluate the effect of clear aligner treatment and differential sequence distalization of maxillary posterior teeth on anchorage loss in the upper incisors (U1s). Methods: This study used lateral cephalometries and digital models of 12 patients treated with 33% sequential distalization (group 1, mean age: 22.9 ± 0.7 years, five males, seven females) and 12 treated with 50% sequential distalization (group 2, mean age: 25.83 ± 0.5 years, three males, nine females) acquired before and after distalization of upper second premolars (U5) and upper first molars (U6) and upper second molars (U7). The amount of distalization was determined as 2.5 mm in both the groups. Independent Samples t test was used to compare normally distributed parameters. Mann–Whitney U and Wilcoxon tests were used to compare parameters that were not normally distributed. Results: In both groups, the posterior teeth significantly moved by tipping distally and the U1s were displaced anteriorly. Increase in maxillary posterior transverse width (P < 0.001) and distopalatal rotation were observed in U5, U6, and U7 after distalization. It was also observed that U1 was significantly more proclined (1.82°; P < 0.001) and protruded (0.62 mm; P < 0.001), and the overjet (0.45 mm; P < 0.001) increased more in group 1 than in group 2. Conclusions: After sequential distalization of maxillary posterior teeth, more anchorage loss was observed in the anterior region in group 1 than in group 2.

Structural repairing of damaged reinforced concrete beam- column assemblies with CFRPs

Özgür Yurdakul,Özgür Avşar 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.54 No.3

Depending on the damage type as well as the level of damage observed after the earthquake, certain measures should be taken for the damaged buildings. In this study, structural repairing of two different types of damaged RC beam-column assembly by carbon fiber-reinforced polymer sheets is investigated in detail as a member repairing technique. Two types of 1:1 scale test specimens, which represent the exterior RC beam-column connection taken from inflection points of the frame, are utilized. The first specimen is designed according to the current Turkish Earthquake Code, whereas the second one represents a deficient RC beam-column assembly. Both of the specimens were subjected to cyclic quasistatic loading in the laboratory and different levels of structural damage were observed. The first specimen displayed a ductile response with the damage concentrated in the beam. However, in the second specimen, the beam-column joint was severely damaged while the rest of the members did not attain their capacities. Depending on the damage type of the specimens, the damaged members were repaired by CFRP wrapping with different configurations. After testing the repaired specimens, it is found that former capacities of the damaged members were mostly recovered by the application of CFRPs on the damaged members.

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.

Diagnostic Signifcance of Ultrasonographic Measurements and Median-Ulnar Ratio in Carpal Tunnel Syndrome: Correlation with Nerve Conduction Studies

Ozan Volkan Yurdakul,Nіlgün Mescі,Yilmaz Çetіnkaya,Duygu Geler Külcü 대한신경과학회 2016 Journal of Clinical Neurology Vol.12 No.3

Background and PurposezzWe determined the reliability of ultrasonography (US) measurements for diagnosing carpal tunnel syndrome (CTS) and their correlation with symptom duration and electrophysiology fndings. We determined whether the ratio of the median-to-ulnar cross-sectional areas (CSAs) can support CTS diagnoses. MethodszzTe pisiform CSA (CSApisiform ), swelling ratio (SR), palmar bowing, and CSApisiform / ulnar CSA (CSAulnar ) measurements made in two subgroups of CTS patients (having sensory afection alone or having both sensory and motor afection) were compared with controls. CSAulnar was measured in Guyon’s canal at the level of most-protuberant portion of the pisiform bone. ResultszzTe values of all of the measured US parameters were higher in patients with CTS (n=50) than in controls (n=62). CSApisiform could be used to diagnose CTS of mild severity. All of the parameters were positively correlated with the distal latency of the compound muscle action potential, and all of them except for SR were negatively correlated with the sensory nerve conduction velocity. A CSApisiform /CSAulnar ratio of ≥1.79 had a sensitivity of 70% and a specifcity of 76% for diagnosing CTS. ConclusionszzOnly CSApisiform measurements were reliable for diagnosing early stages of CTS, and CSApisiform /CSAulnar had a lower diagnostic value for diagnosing CTS.