Seismic risk investigation for reinforced concrete buildings in Antalya, Turkey

Engin Kepenek,Kasim A. Korkmaz,Ziya Gencel 사단법인 한국계산역학회 2020 Computers and Concrete, An International Journal Vol.26 No.3

Turkey is located in one of the most seismically active regions of in Europe. The majority of the population living in big cities are at high seismic risk due to insufficient structural resistance of the existing buildings. Such a seismic risk brings the need for a comprehensive seismic evaluation based on the risk analysis in Turkey. Determining the seismic resistance level of existing building stock against the earthquakes is the first step to reduce the damages in a possible earthquake. Recently in January 2020, the Elazig earthquake brought the importance of the issue again in the public. However, the excessive amount of building stock, labor, and resource problems made the implementation phase almost impossible and revealed the necessity to carry out alternative studies on this issue. This study aims for a detailed investigation of residential buildings in Antalya, Turkey. The approach proposed here can be considered an improved state of building survey methods previously identified in Turkey’s Design Code. Antalya, Turkey’s fifth most populous city, with a population over 2.5 Million, was investigated as divided into sub-regions to understand the vulnerability, and a threshold value found for the study area. In this study, 26,610 reinforced concrete buildings between 1 to 7 stories in Antalya were examined by using the rapid visual assessment method. A specific threshold value for the city of Antalya was determined with the second level examination and statistical methods carried out in the determined sub-region. With the micro zonation process, regions below the threshold value are defined as the priority areas that need to be examined in detail. The developed methodology can be easily calibrated for application in other cities and can be used to determine new threshold values for those cities.

Fresh, flexural and mechanical performance of polyamide and polypropylene based macro-synthetic fiber-reinforced concretes

Fuat Koksal,Cem Bacanli,Ahmet Benli,Osman Gencel 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.82 No.1

The brittleness of concrete can be overcome by fiber reinforcement that controls the crack mechanisms of concrete. Corrosion-related durability issues can be prevented by synthetic fibers (SFs), while macro synthetic fibers have proven to be particularly effective to provide ductility and toughness after cracks. This experimental study has been performed to investigate the comparative flexural and mechanical behavior of four different macro-synthetic fiber-reinforced concretes (SFRCs). Two polyamide fibers (SF1 and SF2) with different aspect ratios and two different polypropylene fiber types (SF3 and SF4) were used in production of SFRCs. Four different SFRCs and reference concrete were compared for their influences on the toughness, compressive strength, elastic modulus, flexural strength, residual strength and splitting tensile strength. The outcomes of the study reveal that the flowability of reference mixture decreases after addition of SFs and the air voids of all SFRC mixtures increased with the addition of macro-synthetic fibers except SFRC2 mixture whose air content is the same as the reference mixture. The results also revealed that with the inclusion of SFs, 11.34% reduction in the cube compressive strength was noted for SFRC4 based on that of reference specimens and both reference concrete and SFRC exhibited nearly similar cylindrical compressive strength. Results illustrated that SFRC1 and SFRC4 mixtures consistently provide the highest and lowest flexural toughness values of 36.4 joule and 27.7 joule respectively. The toughness values of SFRC3 and SFRC4 are very near to each other.

Flexural properties of a light-cure and a self-cure denture base materials compared to conventional alternatives

Emre Mumcu,Altug Cilingir,Burc Gencel,Tonguc S?l?n 대한치과보철학회 2011 The Journal of Advanced Prosthodontics Vol.3 No.3

PURPOSE A new light curing urethane dimethacrylate and a cold curing resin with simpler and faster laboratory procedures may have even improved flexural properties. This study investigated the 3-point flexural strengths and flexural moduli of two alternate base materials. MATERIALS AND METHODS A cold curing resin (Weropress) and a light curing urethane dimethacrylate base material (Eclipse). Along with Eclipse and Weropress, a high impact resin (Lucitone199) and three conventional base materials (QC 20, Meliodent and Paladent 20) were tested. A 3-point bending test was used to determine the flexural strengths and flexural moduli. The mean displacement, maximum load, flexural modulus and flexural strength values and standard deviations for each group were analyzed by means of one-way analysis of variance (ANOVA) (with mean difference significant at the 0.05 level). Post hoc analyses (Scheffe test) were carried out to determine the differences between the groups at a confidence level of 95%. RESULTS Flexural strength, displacement and force maximum load values of Eclipse were significantly different from other base materials. Displacement values of QC 20 were significantly different from Lucitone 199 and Weropress. CONCLUSION The flexural properties and simpler processing technique of Eclipse system presents an advantageous alternative to conventional base resins and Weropress offers another simple laboratory technique.

Mechanical properties of blended cements at elevated temperatures predicted using a fuzzy logic model

Ahmet Beycioğlu,Adil Gültekin,Hüseyin Yilmaz Aruntaş,Osman Gencel,Magdalena Dobiszewska,Witold Brostow 사단법인 한국계산역학회 2017 Computers and Concrete, An International Journal Vol.20 No.2

This study aimed to develop a Rule Based Mamdani Type Fuzzy Logic (RBMFL) model to predict the flexural strengths and compressive strengths of blended cements under elevated temperatures. Clinoptilolite was used as cement substitution material in the experimental stage. Substitution ratios in the cement mortar mix designs were selected as 0% (reference), 5%, 10%, 15% and 20%. The data used in the modeling process were obtained experimentally, after mortar specimens having reached the age of 90 days and exposed to 300C, 400C, 500C temperatures for 3 hours. In the RBMFL model, temperature (C) and substitution ratio of clinoptilolite (%) were inputs while the compressive strengths and flexural strengths of mortars were outputs. Results were compared by using some statistical methods. Statistical comparison results showed that rule based Mamdani type fuzzy logic can be an alternative approach for the evaluation of the mechanical properties of concrete under elevated temperature.

Characteristics of lightweight diatomite‑based insulating firebricks

Serkan Dal,Mucahit Sutcu,Mustafa Sabri Gok,Osman Gencel 한국세라믹학회 2020 한국세라믹학회지 Vol.57 No.2

This study covers the physical, thermal, mechanical, and microstructural properties of porous ceramic materials produced from mixtures containing refractory clay and diatomite in different proportions. The raw materials were characterized by chemical (X-ray fluorescence), thermal (thermogravimetry), morphological (scanning electron microscopy), and phase (X-ray diffraction) analysis techniques. The prepared samples were sintered at different firing temperatures between 900 and 1100 °C in an electrical furnace. The bulk densities, apparent porosities, linear dimensional shrinkages, compression strengths, thermal conductivities, and microstructural properties of the sintered samples were investigated. The porosity of the sample with 90% diatomite content increased to 55.4%, density decreased to 1.02 g/cm3, and thermal conductivity coefficient decreased to 0.32 W/mK.

Retrorectal tumor: a single-center 10-years’ experience

Orçun Yalav,Uğur Topal,İsmail Cem Eray,Mehmet Ali Deveci,Eyüphan Gencel,Ahmet Rencuzogullari 대한외과학회 2020 Annals of Surgical Treatment and Research(ASRT) Vol.99 No.2

Purpose: Retrorectal tumors (RTs) are a rare incidence and recommendations on the ideal surgical approaches are lacking. This study aimed to evaluate outcomes and follow-up results of patients undergoing excision of RTs at our institution. Methods: A retrospective review was conducted for undergoing surgery for RT between January 2009 and January 2019. Demographic characteristics, presenting symptoms, preoperative diagnostic tests, surgical procedures, histopathological results, intraoperative and postoperative complications, postoperative hospital stay, postoperative 30-day mortality, 90-day unplanned readmission rate, and long-term outcomes were evaluated. Results: Twenty patients with a mean age of 48.3 ± 14.2 were analyzed. The most common presenting complaint was perineal pain (35.0%). Magnetic resonance imaging and computed tomography was preferred in 18 and 2 patients, respectively. Tumor localization was below the level of the third sacral vertebrae in 14 patients for whom the posterior surgical approach was used. No postoperative mortality was recorded at the end of follow-up of 53.8 ± 40 months. Mean length of postoperative hospital stay was 8.6 ± 9.4 days. Ten percent of the patients had unplanned hospital readmission within 90 days after discharge. Recurrence developed in 1 patient, for whom pathology were reported as chordoma. Conclusion: RT should be managed by a multidisciplinary team given the complexity and heterogeneity of these tumors despite the fact that the majority are benign. A good understanding of pelvic anatomy and characterization of lesions through detailed radiological imaging is crucial to optimize surgical planning. Complete surgical resection is key for prolonged disease-free and overall survival of patients diagnosed with RTs.

Experimental and numerical analysis of new bricks made up of polymer modified-cement using expanded vermiculite

Fuat Köksal,Juan J. del Coz Diaz,Osman Gencel,Felipe P. Alvarez Rabanal 사단법인 한국계산역학회 2013 Computers and Concrete, An International Journal Vol.12 No.3

In this paper, the properties of the cement mortar modified with styrene acrylic ester copolymer were investigated. Expanded vermiculite as lightweight aggregate was used for making the polymer modified mortar test specimens. To study the effect of polymer–cement ratio and vermiculite-cement ratio on various properties, specimens were prepared by varying the polymer–cement and vermiculite-cement ratios. Tests of physical properties such as density, water absorption, thermal conductivity, three-point flexure and compressive tests were made on the specimens. Furthermore, a coupled thermal-structural finite element model of an entire corner wall was modelled in order to study the best material configuration. The wall is composed by a total of 132 bricks of 120 × 242 × 54 size, joined by means of a contact-bonded model. The use of advanced numerical methods allows us to obtain the optimum material properties. Finally, comparisons of polymer–cement and vermiculite-cement ratios on physical properties are given and the most important conclusions are exposed.