Graduation Year

2025

Document Type

Thesis

Degree

M.S.C.E.

Degree Name

MS in Civil Engineering (M.S.C.E.)

Degree Granting Department

Civil and Environmental Engineering

Major Professor

Gray Mullins, Ph.D.

Committee Member

Daniel Simkins Jr., Ph.D.

Committee Member

Manjriker Gunaratne, Ph.D.

Keywords

Moment-Curvature Analysis, Monte Carlo Simulation, Resistance Factors, Strength Reduction Factors, Thermal Integrity Profiling

Abstract

During the construction of drilled shafts, reinforcement cages can be inadvertently placed eccentrically. Current codes, such as ACI 318 and AASHTO LRFD Bridge Specifications, assume there is little impact from such movements within the drilled shaft or that cage centering provisions are sufficiently robust. This thesis will explore the impact that reinforcement cage eccentricity has on the bending capacity of drilled shafts and propose new strength reduction and resistance factors for tension-controlled failure in drilled shafts.

A total of 208 drilled shafts across eleven counties within the state of Florida were tested using thermal integrity profiling to identify the worst case cage eccentricity of the shaft. This information in addition to as-built information from inspectors, was used to perform a moment curvature analysis on the worst case tension failure for a drilled shaft with an eccentricity. This analysis was performed twice to determine the bias and coefficient of variation for different sized drilled shafts.

Monte Carlo analyses were performed and found that the current codes do not properly account for the impact an eccentric reinforcement cage has on a drilled shaft moment capacity. To account for this, more simulations were performed to calibrate the material factors. For the strength reduction factor (ACI) for tension failure for drilled shafts, it is recommended to be reduced from 0.90 to 0.80 for drilled shafts smaller than 72-inches, and from 0.90 to 0.85 for drilled shafts larger than 72-inches. For resistance factors (AASHTO) for tension failure for drilled shafts, it is recommended that the resistance factor be reduced from 0.90 to 0.85 for all shaft sizes.

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