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Construction Engineering PhD Defense by Fray Pozo-Lora

“Flexural & Bond Performance of Pre-Tensioned Beams Reinforced with 1.125-Inch Diameter Prestressing Strands”

10:00 am – 11:00 am
Peter Kiewit Institute
Lily Wang, (402) 554-2065,
Under the supervision of Dr. Marc Maguire

Abstract: Groundbreaking experimental research addressing the bond performance, transfer, and development length of 1-1/8 in. diameter grade 250 strands to concrete is presented in this dissertation. Three different bond testing methodologies were employed to appraise the strands’ pullout force values in concrete and mortar, namely the Large Block Pullout Test (LBPT), the ASTM A1081 test, and the non-prestressed square concrete prisms. The results revealed that the 1-1/8 in. diameter strands exhibit good bonding quality to normal-weight concrete and mortar, though there is limited information for comparison and the testing presented is the only one of its kind for this strand size. Eight full-scale beams were tested to evaluate the development length, pre-stress losses, and large diameter strands’ flexural performance employing one strand only. Two full-scale beams were also tested to assess multiple strands’ effect on the previously mentioned parameters. The transfer length measurements were determined by analyzing the concrete surface strain readings and their corresponding strain profiles employing the 95% AMS method. It was found that current code equations overestimate transfer length for the 1-1/8 in. diameter strands. The beams were also employed to assess the strands’ development length, and it was determined that the current code might overestimate 1-1/8 in. diameter strands in the concretes tested.

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