POST-INSTALLED REINFORCING BAR DESIGN OPTIONS – AN OVERVIEW

Reinforcing bars that are installed into hardened concrete using an adhesive product are referred to as “post-installed” reinforcing bars. The installation process consists of drilling a hole into a concrete member, injecting an adhesive into the hole, and inserting the reinforcing bar into the hole such that the adhesive, when cured, will bond to both the concrete and the bar. The bond that develops between the adhesive and bar, and the adhesive and concrete, permits load applied to the bar to be transferred into the concrete member. Post-installed reinforcing bars that have been evaluated via an accepted test program can be designed for a strength that exceeds the load being applied (also referred to as “strength design”) or for development using cast-in reinforcing bar design provisions.

The International Code Council Evaluation Service (ICC-ES) writes what are known as “acceptance criteria”, to permit evaluation of products for recognition under the International Building Code (IBC). IBC recognition is provided via an ICC-ES evaluation report which is also known as an “ESR”. 

The ICC-ES acceptance criteria for evaluation of adhesive anchor systems under the IBC is titled Acceptance Criteria for Post-Installed Adhesive Anchors in Concrete Elements (AC308). Evaluation per AC308 not only permits recognition under the IBC, it also provides data and provisions that can be used for design with the American Concrete Institute (ACI) standard titled Building Code Requirements for Structural Concrete (ACI 318). ACI 318 includes provisions for designing reinforced concrete members such as beams, slabs and columns; and for anchoring into a concrete member. ACI 318 provisions for reinforced concrete member design are predicated on the use of cast-in reinforcing bars. ACI 318 provisions for anchoring into a concrete member are predicated on the use of cast-in anchors such as ASTM F1554 headed bolts and AWS D1.1 headed studs, or post-installed mechanical anchors and “adhesive anchor systems”. Adhesive products can be considered to be one component of an overall “adhesive anchor system” that consists of the adhesive product, the anchor element (e.g. reinforcing bar), and the approved installation procedure. Reinforcing bars evaluated per AC308 can be post-installed as part of an adhesive anchor system in which the bars are designed using ACI 318 anchoring-to-concrete provisions (e.g. ACI 318-19 Chapter 17 provisions). Reinforcing bars evaluated per AC308 can also be post-installed as part of an adhesive anchor system in which the bars are designed using ACI 318 development provisions (e.g. ACI 318-19 Chapter 25 provisions). Therefore, satisfying the criteria of an AC308 test program permits adhesive product recognition under the IBC, and establishes product-specific data and parameters that permit an adhesive product to be used (e.g. with a reinforcing bar) for design with ACI 318 provisions. The product-specific data and design parameters derived from testing per AC308 test programs are given in an ICC-ES Evaluation Report (ESR). 

The test programs outlined in AC308 Table 3.2 are used to evaluate an adhesive anchor system for use with ACI 318 anchoring-to-concrete provisions. Testing per Table 3.2 is noted in Section 6 of the adhesive anchor ESR.

AC308 Table 3.2 testing establishes design parameters such as the types of anchor elements that can be used with the adhesive, permissible concrete condition (cracked, uncracked, normal weight, lightweight), and load conditions (static, seismic). Table 3.2 testing also establishes installation parameters such embedment depth limits, minimum concrete edge distance, minimum anchor spacing, minimum concrete member thickness, and hole cleaning provisions.

Installation parameters such maximum embedment depth, injection method, and hole cleaning are evaluated to determine if a post-installed reinforcing bar installed per these parameters performs equivalent to a cast-in bar; thereby permitting the post-installed reinforcing bar to be designed for development using ACI 318 development and splice provisions in the same manner as a cast-in bar is designed using these provisions.

You can learn more about Post-Installed Reinforcing Bar design by referencing the following:

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