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Dilek, Ufuk
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Dilek, U.
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udilek@gmail.com
Main Affiliation
05.03. Civil Engineering
Status
Former Staff
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Documents
31
Citations
225
h-index
8
Documents
20
Citations
159
Scholarly Output
6
Articles
4
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0/0
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0
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0
WoS Citation Count
23
Scopus Citation Count
27
WoS h-index
2
Scopus h-index
2
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0
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0
WoS Citations per Publication
3.83
Scopus Citations per Publication
4.50
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0
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0
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| Journal | Count |
|---|---|
| Journal of Performance of Constructed Facılıtıes | 3 |
| American Concrete Institute, ACI Special Publication | 1 |
| Journal of Testıng And Evaluatıon | 1 |
| Research in Nondestructıve Evaluatıon | 1 |
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4 results
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Now showing 1 - 4 of 4
Article Citation - WoS: 1Nondestructive Radiographic Evaluation and Repairs To a Prestressed Concrete Parking Structure Following Partial Collapse(Asce-Amer Soc Civil Engineers, 2015) Reis, Engin Murat; Dilek, UfukThis paper presents use of radiographic imaging (X-ray) in evaluation of existing reinforcing steel and tendon configuration of a structure following a collapse and development of steel retrofit and carbon-fiber-reinforced polymer (CFRP) repairs. A collapsed section in the driving surface in a precast concrete parking deck prompted an engineering evaluation and survey of the entire deck for assessment and repairs to distressed members. Distress was identified in decking members and perimeter spandrel beams in varying forms and degrees. Repairs to the decking members involved supporting the distressed decking using supplemental steel retrofit brackets installed through the double-Tee stems containing prestressing tendons. The precise location of the tendons in the stems needed to be identified to implement this repair in order not to damage the tendons during drilling for through-stem anchors. Radiographic X-ray imaging in this application enabled locating and avoiding the tendons in the stems to support and strengthen the decking member. The supplemental steel brackets also enabled continued and improved operation of an existing expansion joint in the area of repair. Radiographic evaluation technique was also used in identification of steel reinforcement configuration in the perimeter spandrel beams exhibiting cracking at bearing locations with maximum shear. Radiographic exposures were used for evaluation of existing steel configuration and development of CFRP repairs. CFRP repairs were implemented in perimeter spandrel beams while decking surfaces were retrofitted with steel brackets to support the driving surfaces and enable continued expansion and contraction in the existing expansion joints. (C) 2014 American Society of Civil Engineers.Conference Object Citation - WoS: 3Citation - Scopus: 4Comparison of Nondestructive Evaluation Findings, Constrained and Unconstrained Wave Speeds, Dynamic Moduli, and Poisson's Ratio of Core Specimens From a Concrete Structure Damaged by Fire(Asce-Amer Soc Civil Engineers, 2015) Dilek, Ufuk; Reis, EnginThis article discusses the use of nondestructive and subsequent laboratory materials testing techniques in evaluation of extent of fire damage to a precast prestressed parking structure. The nondestructive and laboratory testing findings were used in determination of extent of fire damage to concrete and potential effects on the prestressing tendons. The in-situ nondestructive testing phase consisted of scanning affected areas using ultrasonic pulse velocity through concrete members and use of impact echo on a confirmatory limited basis. Subsequently, cores were removed and tested for resonant frequency-based dynamic modulus in accordance with ASTM C 215. Upon determination of dynamic elastic modulus of the entire core per ASTM C 215, the cores were sawn into 25-mm (1-in.) disks. Young's modulus of individual disks was determined by utilizing nondestructive measurement of resonant frequency. Determination of Young's modulus at small depth increments permitted assessment of the heat-induced damage gradient into the concrete and more importantly at the level of the prestressing tendons. The data from multiple techniques provided a means of comparison between constrained in-situ ASTM C 597 pulse velocity to unconstrained compression wave velocity obtained from ASTM C 1383, and an estimated unconstrained compression wave velocity based on dynamic modulus based on disks. The results of these comparisons should be of value to practicing engineers utilizing these techniques in forensic evaluations. (C) 2014 American Society of Civil Engineers.Article Citation - WoS: 1Citation - Scopus: 1Evaluation and Load Testing of Posttensioned Concrete Structure Exhibiting Distress(Asce-Amer Soc Civil Engineers, 2016) Dilek, Ufuk; Reis, Engin MuratThis article discusses the evaluation of a posttensioned concrete structure exhibiting cracking using nondestructive evaluation, laboratory testing of concrete samples, and subsequent in situ load testing. During a field survey, it was identified that the posttensioned beams exhibited visually apparent deflections. An engineering evaluation was initiated to identify the cause of this type of cracking in the posttensioned structural system. Following a field survey and document review, an analysis was initiated for the estimation of potential posttension losses and analytical expected deflections for the purposes of comparing it to measured deflections in the field. After the analytical phase, an in situ, nondestructive evaluation phase and a subsequent material testing phase were initiated. The in situ evaluation of the structure involved nondestructive testing of concrete slabs and beams using ground-penetrating radar (GPR) to locate tendons. Cores were removed, and compressive strength testing and petrographic analysis of the cores were performed in the laboratory. Based on the review of the findings of the engineering analysis, nondestructive evaluation, and laboratory testing, the concrete beams and slabs were load-tested in accordance with ACI 318, Chapter 20. The load test served to verify that the structure could safely sustain the service load requirements of the building code. This paper should be of value to consulting engineers engaged in condition assessment of posttensioned structures exhibiting distress, in terms of the test methods used and the methodology used in developing various aspects of the load-testing program.Article Citation - WoS: 17Citation - Scopus: 21Effects of Manufactured Sand Characteristics on Water Demand of Mortar and Concrete Mixtures(Amer Soc Testing Materials, 2015) Dilek, UfukManufactured sands are produced by crushing rock deposits to produce a fine aggregate that is generally more angular and has a rougher surface texture than naturally weathered sand particles. Manufactured sands can also contain significant quantities of rock dust. As natural sand deposits become depleted near some areas of metropolitan growth and viable sand sources non-susceptible to alkali-silica reactivity are consumed, the use of manufactured sands as a replacement fine aggregate in concrete is receiving attention. Designers, specifiers, contractors, and material suppliers need to understand the effects of manufactured sand angularity, as well as fines content on concrete water demand and concrete durability. As part of a comprehensive research program, various manufactured sand properties and their effects on fresh and hardened concrete properties were investigated. This paper investigates the effects of manufactured sand properties on water demand of mortar and concrete. The relationships between manufactured sand characteristics and hardened concrete properties are discussed in subsequent papers. Manufactured sands with a wide range of particle angularities and fines contents were included in the testing program. The program involved measurement of various sand attributes, and a subsequent testing phase on mortar workability that isolated and evaluated the effect of the subject sand attributes on water demand and workability of mortars. The testing phase, using mortars rather than full-scale concrete mixtures, enabled the isolation of sand attributes, such as particle angularity, particle size, and fine-particle content; it also enabled the evaluation of the effect of each attribute on water demand. Results of mortar testing confirmed that particle angularity and fineness of the sand gradation (as quantified by fineness modulus) influenced the water demand of mortars. Testing performed on a paired comparison basis on individual sizes with substantially different angularities indicated that, as the particle size decreased, the exponential increase in surface area overshadowed any difference caused by particle angularity between particles of comparable size. The results of sand and mortar testing were used in the development of the subsequent testing phase, examining the effects of manufactured sand properties on concrete water demand utilizing full-scale concrete mixtures. A statistically based water demand model was developed for conventional strength concrete. The regression-based model enabled the evaluation of the contribution of each attribute and the relative importance and statistical significance of each contribution. Particle angularity was found to be the dominant contributor to water demand with the secondary contribution from fineness of the overall sand gradation, as quantified by the fineness modulus and quantity of very fine particles. The influence of these factors was statistically significant. Effects caused by well-graded particle distributions were not found to be significant, contrary to initial expectations.
