Date of Award
Master of Science
Civil, Construction, and Environmental Engineering
Terry J. Wipf
F. W. Klaiber
As the United States highway infrastructure is in need of rehabilitation due to increasing traffic needs and structural inadequacies, use of precast concrete elements is increasing. Use of precast concrete systems provide various advantages, including minimizing traffic disruption, increasing the quality of the final product, and lowering life-cycle costs. Both the Federal Highway Administration and the Iowa Department of Transportation have recognized the benefits of using precast concrete elements in bridge construction to help reduce the duration of construction projects.
This thesis focuses on the laboratory testing of full-depth precast, prestressed concrete deck panels used in the construction of a continuous four-girder, three span bridge over Squaw Creek on 120th Street in Boone County, Iowa. Various laboratory tests were conducted on a single panel and on two panels connected by a closure pour. These tests ranged from determining physical properties of the panel (compressive strength and prestressing force), to determining the panel's response in various circumstances (moving with a crane, during field leveling, and under loading).
Tests were conducted to determine physical characteristics of a deck panel such as compressive strength and stress in the mild reinforcing due to prestressing. The average compressive strength of the concrete core samples was 7,600 psi, which exceeded the specified compressive strength of 5,000 psi. Prestressing strands in one post-tensioning channel were cut to determine the amount of stress in each strand due to prestressing. Of the six bars instrumented, five were found to have a stress lower than that expected from the initial prestressing force.
Strains in the mild reinforcing bars were monitored in the laboratory while a panel was lifted with a crane. Two different strap configurations were used to lift the panel; the first configuration used four lifting straps, and the second used two lifting straps. Results from these tests showed the strap configuration did not have a significant effect on the strain induced in the mild reinforcing bars. The total strain (measured plus induced due to prestressing) of a bar used during these tests had a maximum value of 70%. Panels were also leveled in the laboratory to monitor the strains in the mild reinforcement. Bars were found to utilize 86% of the yield strain during this process.
Service load tests were performed on both a single panel and two panels connected by a closure pour. Through these tests it was determined that the deck panels had adequate strength under service loads.
Both a single panel and two connected panels were tested to failure. Ultimate load tests included testing a single panel and two connected panels to a flexural failure, and testing the connected panels to a punching shear failure. The connected panels also experienced a combination punching shear and flexure failure during one test. Failures during each test occurred at loads much greater than the service loads the panels are expected to experience in the field.
Ryan Paul Bowers
Bowers, Ryan Paul, "Laboratory testing of full-depth precast, prestressed concrete deck panels used in the Boone County IBRC accelerated bridge replacement project" (2009). Graduate Theses and Dissertations. 10526.