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Project 2011-02

Project Title:

Innovative Alternatives for Shear Reinforcement

Institution:

University of Cincinnati
Cincinnati, Ohio

Researchers:

Dr. Bahram M. Shahrooz
Alyssa Hautman

Award Period:

2011-2012 school year

Status:

Completed

Description:

The current shear provisions in the ACI 318-08 Building Code allow for shear reinforcement consisting of (a) stirrups perpendicular to axis of member; (b) welded wire reinforcement with wires located perpendicular to axis of member; or (c) spirals, circular ties, or hoops (Section 11.4.1.1). Although some engineers may use continuous hoops, particularly in seismic applications, the Code does not specifically recognize them as a type of shear / torsion reinforcement.

Recent advancements in automatic steel bar bending machines allow fabrication of “continuous stirrups.” This project focused on evaluating behavior and capacity of continuous stirrups as shear and torsion reinforcement, as well as confinement steel. This stirrup type is viewed to be more efficient than standard stirrups. The closed nature of continuous stirrups can enhance strength and ductility of the members, and overall structural performance.

The principal research outcome will be the formulation of design and detailing provisions for continuous stirrups. In close collaboration with the industry advisory committee, the research team will develop Code provisions for adoption in ACI 318. The proposed system will benefit engineers in the cast-in-place and precast industries, and can be employed in building and bridge construction. Fabrication, jobsite productivity, and accuracy of stirrup placement will be improved during construction. These benefits will result in potential cost reductions and thus a larger market share for concrete structures.