Pryout failure is a failure mode where anchors having limited embedment depth and loaded in shear exhibit sufficient rotation to produce a pryout fracture whereby the primary fracture surface develops behind the point of load application . This failure mode does not depend on the presence of free edges .
Pullout failure is a failure mode in which the anchor pulls out of the concrete without development of the full steel or concrete capacity .
Pull-through failure is a failure mode in which the anchor body pulls through the expansion mechanism without development of the full steel or concrete capacity .
Side face blowout strength is the strength of anchors with deeper embedment but thinner side cover corresponding to concrete spalling on the side face around the embedded head while no major breakout occurs at the top concrete surface .
Steel failure is a failure mode in which the steel anchor parts fracture .
Supplementary reinforcement is reinforcement that acts to restrain the potential concrete breakout area but is not designed to transfer the full design load from the anchors into the structural member .
Torque controlled expansion anchor is a post-installed expansion anchor that is set by the expansion of one or more sleeves or other elements against the sides of the drilled hole through the application of torque , which pulls the cone ( s ) into the expansion sleeve ( s ). After setting , tensile loading can cause additional expansion ( follow-up expansion ).
Undercut anchor is a post-installed anchor that derives tensile holding strength by the mechanical interlock provided by undercutting the concrete , achieved either by a special tool or by the anchor itself during installation .
3.1.2 ANCHORS IN CONCRETE AND MASONRY
Post-installed anchor bolts are used for a variety of construction anchoring applications including column baseplates , supporting mechanical and electric services , fixation of building facades and anchoring guardrails . Critical connections , i . e ., those that are either safety-related or whose failure could result in significant financial loss , require robust anchor solutions capable of providing a verifiable and durable load path . In turn , the selection of a suitable anchor system and its incorporation in connection design requires a thorough understanding of the fundamental principles of anchoring . While a general overview is provided here , additional references can be found at the conclusion of this section .
3.1.3 ANCHOR WORKING PRINCIPLES
Anchors designed for use in concrete and masonry develop resistance to tension loading on the basis of one or more of the following mechanisms :
Friction : This is the mechanism used by most post-installed mechanical expansion anchors to resist tension loads , including the KWIK Bolt TZ , HSL-3 and HDI anchors . The frictional resistance resulting from expansion forces generated between the anchor and the wall of the drilled hole during setting of the anchor may also be supplemented by local deformation of the concrete . The frictional force is proportional to the magnitude of the expansion stresses generated by the anchor . Torque-controlled expansion anchors like the KWIK Bolt TZ and HSL-3 anchors use follow-up expansion to increase the expansion force in response to increases in tension loading beyond the service load level ( preload ) or to adjust for changes in the state of the base material ( cracking ).
Keying : Undercut anchors and , to a lesser degree , certain types of expansion anchors , rely on the interlock of the anchor with deformations in the hole wall to resist the applied tension loading . The ( bearing ) stresses developed in the base material at the interface with the anchor bearing surfaces can reach relatively high levels without crushing due to the triaxial nature of the state of stress . Undercut anchors like the Hilti HDA offer much greater resilience to variations in the base material conditions and represent the most robust solution for most anchoring needs .
Bonding ( adhesion ): Adhesive anchor systems utilize the bonding mechanism that takes place between the adhesive and the anchor element , and the adhesive and the concrete , to transfer the applied load from the anchor element into the concrete . The degree of bonding available is influenced by the condition of the hole wall at the time of anchor installation . Injection anchor systems like Hilti ’ s HIT-HY 200 V3 offer unparalleled flexibility and high bond resistance for a wide variety of anchoring applications .
Hybrid anchor elements like the Hilti HIT-Z threaded rod combine the functionality of an adhesive anchor system with the working principle of a torque-controlled expansion anchor for increased reliability under adverse job-site conditions .
Shear resistance : Most anchors develop resistance to shear loading via bearing of the anchor element against the hole wall close to the surface of the base material . Shear loading may cause surface spalling resulting in significant flexural stresses and secondary tension in the anchor element .
14 Anchor Fastening Technical Guide Edition 22 | 3.0 ANCHORING SYSTEMS | 3.1 ANCHOR PRINCIPLES AND DESIGN Hilti , Inc . 1-800-879-8000 | en español 1-800-879-5000 | www . hilti . com | Hilti ( Canada ) Corporation | www . hilti . ca | 1-800-363-4458