Date of Graduation

12-2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Engineering (PhD)

Degree Level

Graduate

Department

Civil Engineering

Advisor/Mentor

Prinz, Gary

Committee Member

Murray, Cameron

Second Committee Member

Hebdon, Matt

Third Committee Member

Hale, Micah

Keywords

Composite bridges; Fatigue; Shear studs; Structural engineering

Abstract

Following curing of the concrete deck, load transfer between the concrete and steel components in a composite bridge girder is possible through three mechanisms: 1) mechanical contact (bearing) between the embedded shear connectors and surrounding cured concrete, 2) adhesion between the cured concrete and steel-section top flange, and 3) friction between the contacting materials Understanding the mechanisms of bearing, adhesion, and friction shear transfer at the steel-concrete interface of composite bridge girders is necessary for efficient proportioning of headed shear connectors (or studs) in design. To better understand the roles that stud bearing, adhesion, and friction play in composite girder load transfer, a two-part experimental program is executed in this study, involving 1) component-scale laboratory testing (isolating a section of composite girder) under controlled direct shear loading, and 2) full-scale girder testing under combined flexure and shear loading. Various instrumentations, including thin foil pressure gauges mounted to the embedded shear studs are used to measure stud demands. Results from the direct shear and flexure testing indicate that uncoated flanges in composite girders (having an SP-10 blast cleaned surface) experience lower stud demands than those currently predicted by the AASHTO specification. This is likely due to a complex girder-to-slab interface condition (interface interlocking) that is created during adhesion breakage resulting in a baseline stud demand reduction of 42%. Coating of the steel flange (application of a paint primer) prior to concrete casting likely affects the beneficial load transfer interface that is created following adhesion loss and can be expected to result in higher stud demands than those created from uncoated/un-primed flange conditions. For coated flanges, an interface friction reduction percentage equal to 2*N% is recommended, where N is the tributary slab and overlay dead load in kips/ft. Implementation of the stud demand reduction in a case-study re-design of the James Street bridge in Jacksonville, Arkansas, show a 27.7% and 29.2% reduction in the number of required shear studs for a composite bridge having uncoated exterior and interior girders respectively.

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