Brief
Post-installed reinforcing bars that comply with anchoring-to-concrete provisions under ACI 318 are typically designed with anchor failure modes in mind, not yield. Richard Morgan from Hilti North America examines recent research that covers how anchoring-to-concrete provisions could be used to design post-installed deformed rebar for yield, which entails accounting for breakout failure and bond failure instead of splitting failure.
Insight
Designing For Yield Based on Anchoring-to-Concrete Provisions
The American Concrete Institute (ACI) standard ACI 318, Building Code Requirements for Structural Concrete, includes provisions to design cast-in reinforcing bars for development, i.e., embedding a bar deep enough to develop the yield strength without splitting failure occurring.
Splitting failure refers to cracking and splitting in the concrete around bars in tension. Post-installed reinforcing bars have typically been designed using ACI 318 anchoring-to-concrete provisions, which consider various possible anchor failure modes rather than designing the bars to yield.
This article expands the discussion of a design concept introduced in an ACI Structural Journal article by Charney et al. in which anchoring-to-concrete provisions could be used to design post-installed reinforcing bars specifically for yielding.
What is a Post-Installed Reinforcing Bar?
Post-installed reinforcing bars are installed into hardened concrete. The bars are part of an overall system consisting of the bar, an adhesive product, and the installation method (Figure 1).
A hole is drilled into the concrete, cleaned, filled with adhesive, and a bar is inserted into the adhesive-filled hole. After the adhesive cures, any load applied to the bar is transferred into the concrete via bonding between the adhesive, the bar, and the concrete.
Adhesive systems must be evaluated to demonstrate compliance with relevant code parameters. For example, the International Code Council Evaluation Service (ICC-ES) acceptance criteria AC308, Post-Installed Adhesive Anchors in Concrete Elements, can be used to evaluate adhesive systems for design per the International Building Code (IBC) and ACI 318 provisions.
Related Sources:
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ACI – ACI 318
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ACI – Anchoring
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AATM – Anchor Bolt
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Hilti – BS code for the selection and installation of post-installed anchors
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