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Additional Pankow Research 2016

Project Title:

Influence of Mechanical Properties of High-Strength Steel on
Deformation Capacity of Reinforced Concrete Walls

Institution:

University of Kansas
Lawrence, KS

Researchers:

MS Huq, AS Weber-Kamin, S Ameen
A Lepage
RD Lequesne

Award Period:

2016

Status:

Completed - Click here to download the Research Report

Description:

Use of high-strength steel bars with a nominal yield strength greater than 80 ksi (550 MPa) as longitudinal reinforcement in concrete is not currently permitted by U.S. building codes. This is mostly due to insufficient test data and, until recently, the limited availability of affordable high-strength steel. Use of high-strength steel bars could, however, allow designers to reduce the amount of reinforcement, resulting in less reinforcement congestion, simpler construction, and lower cost.

It is now possible to produce high-strength steel reinforcement at a cost that is competitive with Grade 60 (420 MPa) reinforcement. The various methods of doing so, however, result in post-yield behaviors that range from a bar having a clearly defined yield point and limited strain-hardening (tensile-to-yield strength ratio, T/Y, greater than 1.0) to a bar that exhibits no yield point and pronounced strain hardening. The 0.2%-offset method is commonly used to define the yield strength. Values of T/Y typically range between 1.1 and 1.5.

The main objective of this research is to study the effects of mechanical properties of reinforcement on the behavior and deformation capacity of T-shaped concrete walls. In particular, this investigation aims to define the minimum elongation required for high-strength reinforcing bars to be used in earthquake-resistant slender walls and to examine whether T/Y affects that requirement by altering the spread of plasticity in the plastic hinge region. It is important to study these variables through tests of T-shaped walls because the shape of the cross-section leads to larger longitudinal reinforcement tensile strain demands than in most other members. Reported results will also be evaluated to determine whether the performance of T-shaped concrete walls under lateral loads is affected by using reduced amounts of high-strength steel Grade 100 (690) in place of conventional Grade 60 (420) reinforcement.

Funded by the Charles Pankow Foundation. Co-funded by The Concrete Reinforcing Steel Institute Education & Reseach Foundation and The American Concrete Institute Foundation.