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Anchors_2_17.qxp_Layout 1  8/21/17  2:52 PM  Page 86

                                                                                                    ANCHORS




            INTRODUCTION                                             REQUIREMENTS FOR POST-INSTALLED ANCHORS
            INTRODUCTION
        ANCHORS  The term post-installed anchor is used to          Table 1704.4 of the IBC provides special inspection

                                                                    requirements for concrete construction. Anchors
            describe devices installed in holes drilled in
            hardened concrete for the purpose of
                                                                    installed in hardened concrete are listed as requiring
            transferring loads. Post-installed anchor types
            include expansion, undercut, screw, grouted             periodic special inspection. Periodic special inspection is the
                                                                    inspection of construction or work by an approved special
            and adhesive anchors.                                   inspector who is intermittently present in the area when and
                                                                    where the construction or work has been or is being performed.
            Torque-controlled expansion anchors are set by
            the application of a defined torque to the anchor bolt. This generates the  The inspection requirements for post-installed anchors are
            necessary expansion force in the anchor and preloads the bolt. Torque-  generally derived from the manufacturer’s published installation instructions
            controlled expansion anchors re-expand upon the application of tension  (MPII) and from the relevant evaluation report (ICC-ES ESR) for the product.
            loads in excess of the preload in the bolt, a mechanism referred to as   Typical inspection procedures consist of reviewing the type of anchors that
            follow-up expansion.                                    will be installed prior to the commencement of work and determination of
                                                                    what aspects of the installation are critical from an inspection standpoint.
            Special inspection is the inspection of construction activities requiring
                                                                    This varies from anchor type to anchor type. Generally, inspection focuses on
            unique expertise or where additional assurance of quality is deemed
                                                                    verification that the anchor is in accordance with the project specifications,
            necessary. Concrete placement, masonry construction, structural welding
                                                                    that the installation procedure is in accordance with the MPII, and that the
            and high strength bolting are common special inspection items. These
                                                                    anchor size, placement and embedment are in accordance with the contract
            inspections are in addition to the normal progress inspections performed
                                                                    documents.
            by the building department inspectors.
                                                                    Where required by the contract documents, procedures to avoid existing
            TYPES OF POST-INSTALLED ANCHORS                         reinforcing bars in the concrete during drilling are reviewed by the inspector.
                                                                    Where core drilling is used, this is particularly important. Measures to
            Mechanical anchors comprise undercut anchors, expansion anchors  be taken if reinforcing bars are encountered or damaged may include
            and screw anchors. In their usual form, undercut anchors interlock  relocation of the anchor and will usually involve consultation with the EOR.
            with the concrete at the base of the drilled hole. They derive tension
            resistance by bearing. Expansion anchors derive tension resistance
            via the friction generated by expansion forces against the wall of the  POST-INSTALLED MECHANICAL ANCHORS
            drilled hole. Two types of expansion anchors, torque-controlled and
            displacement controlled are identified. Torque-controlled expansion  The special inspector must verify that the installation is in accordance with
            anchors are set by the application of a defined torque to the anchor bolt.  the requirements of the approved construction documents, applicable
                                                                    evaluation report and the MPII, including verification of the location of the
            This generates the necessary expansion force in the anchor and  anchor, edge distance and spacing requirements. Pre-installation inspection
            preloads the bolt. Torque-controlled expansion anchors re-expand  of post-installed mechanical anchors usually consists of verification of anchor
            upon the application of tension loads in excess of the preload in the  type, material, size and length, drilling method, drill bit type and size, hole
            bolt, a mechanism referred to as follow-up expansion.   cleaning procedures, and anchor installation and setting procedures. Special
            Displacement-controlled expansion anchors are set by driving the   attention to aspects of the installation may be required depending on the job
            expansion cone or the anchor sleeve through a defined displacement,  conditions. For example, where anchors installed in a slab on grade, it may be
            which results in a corresponding level of expansion force.   necessary to check that the hole drilling procedures do not result in breaking
                                                                    through to the underside of the slab.
            Displacement-controlled expansion anchors don’t generate additional
            expansion force upon loading. Screw anchors derive tension resistance   Use of a properly calibrated torque wrench is required for setting of many
            via the interlock of the screw threads with the concrete. Adhesive   types of anchors, and is also required to avoid over-torqueing of anchors
            anchors derive tension resistance via the bond of the adhesive with   during subsequent assembly. Prior to application of torque, anchor threads
            the concrete surface in the drilled hole and with the steel anchor   are inspected for damage or fouling. During setting of torque-controlled
            element. Hybrid anchors, such as torque-controlled adhesive anchors,   expansion anchors, the inspector will note the number of full turns required
            combine the working principle of expansion and adhesive anchors.  to achieve the required torque. the threads.
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           800 456-2658         email: sales@tannerbolt.com        www.shoptanner.com
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