Evaluation of the Orientation of 90 ° and 180° Reinforcing Bar Hooks in Wide Members

Status

Sequential Number

Identification Number

Matching Research Agency

Concrete Reinforcing Steel Institute (CRSI)

Principal Investigator

Student Involvement

Project Objective

The overall goal of the proposed project is to study the influence of tilt angle on the development of ACI standard reinforcing bar hooks.

Specific project objectives include:

-         evaluate  90° and 180° ACI standard reinforcing bar hooks to determine the influence of hook tilt angle (from vertical) on the development of the reinforcing bar;

-         study the influence of confinement and transverse reinforcement on the development of tilted, hooked reinforcing; and

-         develop design recommendations for limits of tilt of hooked reinforcing bars.

Project Abstract

Longitudinal reinforcing steel in concrete flexural elements is often developed at the end of a concrete member by a 90° or 180° standard hook that is usually oriented such that the hook is in the vertical direction. In some instances, such as the case of a shallow member that is heavily-reinforced with reinforcing bars of large diameter, the standard hook height in plus concrete cover above and below the bar may exceed the thickness of the concrete member. To address this issue, sometimes it is suggested that the hook may tilted from vertical to maintain the required clear cover. The limits of this tilt, however, are not defined or known. To address this issue, the overall goal of the proposed project is to study the influence of tilt angle on the development of standard reinforcing bar hooks and determine determine the limits of reinforcing steel hook tilt, if any, so ultimate performance of the member is not compromised. Design recommendations developed as part of this study will provide clarification to engineers and building code officials regarding limits of tilt of hooked reinforcing bars so that the original intent of hooked bar development is met.

Task Description

N/A

Anticipated Benefits

The topic of this study has been identified by CRSI as high-priority for the concrete reinforcing steel industry.  Design recommendations developed as part of this study will provide clarification to engineers and building code officials regarding limits of tilt of hooked reinforcing bars so that the original intent of hooked bar development is met.

Modal Orientation

Milestones

Relationship to other Research/Projects

N/A

Technology Transfer Activities

Results of this study will be disseminated through technical publication through CRSI as well as at least one peer-reviewed journal article. 

Transportation Research Board Keywords

Bridge superstructures, reinforcing bars, development