Evaluation of Concrete Pile to Footing or Cap Connections

Authors

Isabella Rakestraw, Florida International UniversityFollow

Document Type

Dissertation

Degree

Doctor of Philosophy (PhD)

Major/Program

Civil Engineering

First Advisor's Name

David Garber

First Advisor's Committee Title

Committee chair

Second Advisor's Name

Armin Mehrabi

Second Advisor's Committee Title

Committee member

Third Advisor's Name

Seung Jae Lee

Third Advisor's Committee Title

Committee member

Fourth Advisor's Name

Kingsley Lau

Fourth Advisor's Committee Title

Committee member

Fifth Advisor's Name

Wallied Orabi

Fifth Advisor's Committee Title

Committee member

Keywords

Concrete, pile cap, footing, piles, pile-to-cap connection, bridges

Date of Defense

6-27-2023

Abstract

Foundations for many bridges consist of driven piles embedded in pile caps or footings whereby axial loads, lateral loads and moments are transferred from the bridge to underlying soil and/or bedrock. The connection between the pile and pile cap will affect the way forces are transferred through the bridge. The pile-to-cap connection is typically either assumed to be a pinned or a fixed connection. Current design recommendations for pinned and fixed connections vary in different states. Assuming a different level of fixity between pile and pile cap can lead to undesirable behavior of a structure. The disconnect between current design provisions and past research would suggest that many structures may have a different level of actual fixity between piles and pile caps than assumed. The primary objective of this research is to better understand the connection between the pile and pile cap, to analyze the impact of the connection in the overall structure, and to provide a better guidance to engineers. These objectives were accomplished through three interdependent research efforts, which included a literature review of previous research; an analytical investigation and numerical modeling to explore possible experimental vi variables; and an experimental testing to evaluate the level of fixity and impact of primary variables. Experimental testing was completed involving ten prestressed concrete pile specimens embedded into cast-in-place pile caps. Two different square pile sizes were investigated, 18-inch and 30-inch, that were simply embedded into the pile cap to lengths between 0.25 and 1.5 times the diameter of the piles. The tests were conducted to determine the moment capacity of the connection at failure. In all cases, the capacity of the connection was higher than expected due to the confining stress provided by the pile cap, which tends to decrease the development length of the strands. Recent research has shown that current design recommendations can be conservative under certain circumstances, e.g., a fixed connection can be achieved with a much shorted embedment length. A better design guidance of the connection between precast prestressed concrete piles and cast-in-place pile caps is needed to assure designs are completed correctly and conservatively.

Identifier

FIDC010980

Previously Published In

“Impact of pile-to-cap fixity on the design and behavior of sensitive structures”, PCI Journal, Jan-Feb 2022 Issue

Recommended Citation

Rakestraw, Isabella, "Evaluation of Concrete Pile to Footing or Cap Connections" (2023). FIU Electronic Theses and Dissertations. 5165.
https://digitalcommons.fiu.edu/etd/5165