Degree Granting Department
Civil and Environmental Engineering
Austin Gray Mullins, Ph.D.
Rajan Sen, Ph.D.
Daniel Hess, Ph.D.
Sarah Kruse, Ph.D.
Michael J. Stokes, Ph.D.
Drilled Shaft, Driven Piles, Thermal Integrity Post Grout, Fiber-Reinforced Polymers
There are over 602,000 bridges in the United States, of which 12.5% are classified as functionally obsolete and 11.2% are structurally deficient. The functionally obsolete bridges will require expansion or replacement to increase the service capacity of the bridge. The structurally deficient bridges will either need remediation of the load carrying elements which are damaged or deteriorated or will need to be replaced completely. Replacement of the bridges means new construction; new construction means better design and quality assurance to meet the 100+ year service life requirement in place now. Rehabilitation of bridges will require better design and quality assurance to increase the current service life of the structure. This dissertation presents new design, testing, and repair methods developed to extend the life of new and existing bridges through pressure grouting, thermal integrity testing of drilled shafts, and the bond enhancement of fiber reinforced polymer (FRP) repair materials bonded to concrete with vacuum bagging and pressure bagging, respectively.
Pressure grouting of drilled shaft tips has been used for over five decades to improve the end bearing capacity, but no rational design procedure had ever been published until this study. The research outlined in this dissertation analyzed nine grouted shafts and compared them to standard design procedures to determine the improvement in end bearing. Improvements ranged from 60% to 709% increase in end bearing capacity. From these improvements, a design procedure was developed for pressure grouted drilled shafts.
Post construction inspection of drilled shafts relies largely on non-visual techniques dealing with measured concrete quantities, acoustic wave speed or frequency, gamma radiation attenuation and now the internal temperature of the curing concrete. Thermal Integrity Profiling (TIP), developed at USF, utilizes the heat of hydration of curing concrete to evaluate the concrete cover, foundation shape, cage alignment, and concrete mix design performance. This research developed standard test equipment and procedures for thermal integrity testing.
Comparing the results of the different types of integrity tests is difficult due to the varied nature of the different tests. The dissertation looked at various shafts constructed across the nation which were tested with thermal and at least one other integrity test method. When compared to acoustic and gamma radiation test results, TIP agreed with 4 of 6 cases for acoustic and 2 of 5 cases using gamma radiation. In the one case were both sonic caliper and inclination data were available, TIP showed good agreement.
Vacuum bagging and pressure bagging are techniques for improving the FRP-concrete bond in the repair of partially submerged piles. Prototype vacuum bagging and pressure bagging systems were developed and bond improvement assessed from results of pullout tests on full size piles repaired under simulated tidal exposures in the laboratory. Pressure bagging gave better bond and was found to be simpler because it did not require an airtight seal. A field demonstration project was conducted in which pressure bagging was used in combination with two different glass FRP systems to repair two corroding piles supporting the Friendship Trails Bridge across Tampa Bay. Inspection of the post-cured wrap showed no evidence of air voids.
Scholar Commons Citation
Winters, Danny, "Selected Topics in Foundation Design, Quality Assurance, and Remediation" (2014). Graduate Theses and Dissertations.