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Wil-Bond Epoxy Anchor Design Considerations
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Wil-Bond adhesive anchors are a two component 100% solid, high aspect ceramic blend epoxy. They consist of a resin and a curing agent Adhesive anchors are often used because of fast curing times compared to cement based grouts. The Wil-Bond adhesive, after being properly mixed through the mixing nozzle, experiences an exothermic reaction which forms a polymer matrix bonding to the surrounding concrete. The bond generated by the Wil-Bond adhesive is accomplished through a dual action of chemically adhering to the concrete and by interlocking with drill hole surface deformations. When designing adhesive anchor systems the engineer should be aware of four potential failure modes; ductile steel failure, concrete breakout, bond failure between the adhesive and the steel threads and bond failure between the concrete and epoxy interface. Presently the anchor industry is absent of a formal design code for adhesive anchors, however the designer can consider the following equations for assistance. |
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Uniform Bond Stress Model |
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N
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Bond Stress (lbs.) |
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Bond Stress (based on cure times at 70˚ F) |
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1600 psi in 14 days - ASTM C882 |
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1100 psi in 2 days - ASTM C882 |
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3.14 |
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d
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Drill Hole Diameter (in.) |
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Anchor Embedment Depth (in.) |
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Concrete Breakout Strength |
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A designer can estimate the concrete capacity using methods such as ACI 349-97 Appendix B or ACI 318-02 Appendix D. Example: |
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P
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Concrete Capacity (lbs.) |
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fc'
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Concrete Compressive Strength (psi) |
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Ac
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 (hef)2 = Projected Cone Area (in2) |
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Anchor Embedment Depth (in.) |
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Williams recommends designing for ductile steel failure whenever possible. Steel strengths can be collected from the strength charts. The designer can verify concrete capacity and bond strengths from the equations listed above to determine which are the governing factors. |
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 Williams Form Engineering Corp. All rights reserved. |
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