Long-Term Performance of Epoxy Adhesive Anchor Systems (2013) / Chapter Skim
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3 Introduction The objectives of this research project were to: • Investigate the influence of various parameters (e.g., type of adhesive, installation conditions, and in-service conditions) on the sustained-load performance of adhesive anchors and • Develop recommended test methods, material specifications, design guidelines, design specifications, quality assurance guidelines, and construction specifications for AASHTO for the use of adhesive anchors in transportation structures.
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4concrete breakout failure adhesive/concrete interface steel/adhesive interface adhesive/concrete and steel/adhesive interface Source: Cook et al.
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5 calculated at the anchor diameter (d)
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6• Mixing Effort: how well are the constituent parts mixed prior to installation. • Adhesive Curing Time When First Loaded: 24 hours, 7 days, 28 days, or longer.
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7 based adhesives have higher bond strengths than ester-based adhesives. ASTM C881/C881M classifies seven types of epoxy-resin bonding systems, specifying Type IV as those that are for use in load-bearing applications for bonding hardened concrete to other materials, but Type IV is not specifically identified for epoxies used in adhesive anchor systems.
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8adhesive and the anchor and/or the concrete and a smaller bond area reduces bond strength. Section 1.6 of the Florida Department of Transportation's (FDOT)
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9 Type of Concrete. The concrete mix design can affect the bond strength of the adhesive anchor.
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10 fied effects. According to Messler (2004)
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11 Radiation Test. This test evaluates the radiation resistance of an adhesive anchor system.
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12 Concrete temperature readings are conducted during the test and if the concrete temperature falls below the minimum temperature for more than 24 hours, the test duration is extended to account for the total time below the minimum temperature. The test is continued for 42 days (1,000 hours)
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13 Test series 13 through 14 evaluated the critical and minimum edge distances for shear loading. Test series 15 was a combined tension and shear static test in which the direction of loading was at a 45° angle from the concrete.
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14 greater than 80% of the average tension load of the control specimens. Freezing and Thawing Test (optional)
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15 • Permitted drilling methods. Evaluates installations in holes created with rotary hammer drill with carbide tip, core drill, and rock drill.
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16 Assessment Approach. Section 10.4.4 addresses the requirements on load-displacement behavior.
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17 where –tu,i = mean bond stress from reliability test series in concrete batch or test member i, –to,i = mean bond stress from reference test series in concrete batch or test member i, tk,i = characteristic bond stress from reliability test series in concrete batch or test member i calculated in accordance with §10.3, tk,o,i = characteristic bond stress from reference test series in concrete batch or test member i calculated in accordance with §10.3, and areq = controlling value for reliability tests and service- condition tests where calculation of a is required. The reference value (areq)
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18 Sensitivity to Crack Width, High-Strength Concrete (ACI 355.4 §7.14)
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19 Tension Tests in Uncracked and Cracked Concrete (ACI 355.4 §8.4)
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20 the anchor under the sustained preload portion shall stabilize prior to static tension testing. Establishment of Cure Time at Standard Temperature (ACI 355.4 §8.7)
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21 is opened to the maximum crack width during the seismic test and a static tension test is conducted in accordance with ASTM E488 until failure. For acceptance, the anchors must complete the seismic loading cycle without failure.
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22 The nominal characteristic bond stress for each servicecondition test (tk,nom(cr,uncr)
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23 CALTRANS Standard Specifications Section 75 "Miscellaneous Metal" of the CALTRANS (2006b) Standard Specifications lists the requirements for resin capsule anchors tested under CALTRANS (2001)
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24 New York State Department of Transportation Standard Specifications New York State Department of Transportation (NYSDOT)
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25 of 5⁄8" (16 mm) , and an embedment of 4" (102 mm)
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26 systems use #5 epoxy coated 60 ksi rebar. The following tests are conducted: Dry Conditioning.
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27 rather Section 1.3 references other previously discussed standards such as: • EOTA ETAG 001, • ICC-ES AC308, and • ACI 355.2. Other Test Methods The following section presents various alternate test methods that can potentially evaluate sustained load performance of adhesive anchor systems.
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28 cheaper, and quicker than tests that involve the entire adhesive anchor system installed in concrete. It is understood that the interaction of the adhesive with the concrete is an important variable to creep resistance and is essential to be included in the testing.
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29 Time–temperature superposition works well for polymers within the linear viscoelastic region where compliance is independent of stress. For materials whose compliance increases as stress increases, time–temperature superposition is not appropriate.
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30 E″, and tan delta curves (respectively) generated by the researchers.
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31 Source: Chin et al.
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32 (c) Pullout strength of cast-in, post-installed expansion or undercut anchor in tension; (d)
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33 Bond strength of adhesive anchor in tension. The nominal bond strength of a single adhesive anchor (Na)
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34 The value (futa) used in Eq.
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35 where Nua = factored tension force, lbs; Nn = nominal strength in tension, lbs; Vua = factored shear force, lbs; Vn = nominal strength in shear, lbs; and j = strength reduction factor. AASHTO LRFD Bridge Design Specifications The AASHTO (2010b)
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36 the researchers' opinion that if ACI is conservative for the cases examined, then it should be conservative for AASHTO to use ACI design provisions for adhesive anchor design. Load Factors.
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37 adhesive anchors. FDOT does not allow adhesive anchors for overhead or upwardly inclined holes.
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38 In this design approach, the anchor bolts are only designed for shear. The number of anchor bolts is determined by dividing the base shear at the bearing by the allowable shear force per anchor.
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39 shear loading. The design methodology is only applicable for anchors with a predominate static load.
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40 (MPII) were also reviewed for an understanding of what is typically required in adhesive anchor installations.
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41 provides guidance for installation and construction inspection. While this report only addresses cast-in-place anchors and not adhesive anchors, most of the information covers the casting of anchor bolts in concrete and tightening of the anchor bolt following concrete curing.
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42 (2007) Standard Specifications for Road and Bridge Construc tion that the installation of adhesive anchors and the equipment used for the installation must be in accordance with the manufacturer's specifications.
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43 and the products chosen were not necessarily what were used in the testing program of this research project. Manufacturer's specifications contain information regarding storage conditions (temperature and humidity ranges)
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44 water, brushed, and then flushed with water again. The standing water must be removed prior to inserting the adhesive.
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