Browsing by Author "Reis, Engin Murat"

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Citation - WoS: 1
Citation - Scopus: 1
Evaluation and Load Testing of Posttensioned Concrete Structure Exhibiting Distress
(Asce-Amer Soc Civil Engineers, 2016) Dilek, Ufuk; Reis, Engin Murat
This 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.
Citation - WoS: 1
Nondestructive Radiographic Evaluation and Repairs To a Prestressed Concrete Parking Structure Following Partial Collapse
(Asce-Amer Soc Civil Engineers, 2015) Reis, Engin Murat; Dilek, Ufuk
This 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.