Anchor bolt

layout. The channel can be a hot-rolled or a cold-formed steel shape in which a T-shape screw is placed in order to transfer the load to the base material. • Headed stud: consist of a steel plate with headed studs welded on (see also threaded rod). • Threaded sleeves: consist of a tube with an internal thread which is anchored back into the concrete. For all the type of the cast-in-place anchors, the load-transfer mechanisms is the mechanical interlock, or chemical anchors. The anchoring material is an adhesive (also called mortar) The performance of this anchor's types in terms of 'load-bearing capacity', especially under tension loads, is strictly related to the cleaning condition of the hole. Experimental results and creep response. Bonded expansion anchor Bonded expansion anchors are a hybrid of mechanical and chemical anchors. Screw anchors The force-transfer mechanism of the screw anchor is based on concentrated pressure exchange between the screw and concrete through the pitches. Plastic anchors Their force-transfer mechanism is similar to mechanical expansion anchors. A torque moment is applied to a screw which is inserted in a plastic sleeve. As the torque is applied the plastic expands the sleeve against the sides of the hole acting as expansion force. Tapcon screws Tapcon screws are a popular anchor that stands for self tapping (self threading) concrete screw. Larger diameter screws are referred to as LDT's. This type of fastener requires a pre-drilled hole—using a Tapcon drillbit—and are then screwed into the hole using a standard hex or phillips bit. These screws are often blue, white, or stainless. They are also available in versions for marine or high stress applications. Powder-actuated anchors They act transferring the forces via mechanical interlock. This fastening technology is used in steel-to-steel connection, for instance to connect cold-formed profiles. A screw is inserted into the base material via a gas actuated gas gun. The driving energy is usually provided by firing a combustible propellant in powder form. The fastener's insertion provokes the plastic deformation of the base material which accommodates the fastener's head where the force transfer takes place. ==Mechanical behavior==

Modes of failure in tension Anchors can fail in different way when loaded in tension: This kind of failure is typical in pull-out test. • Splitting failure: failure is characterized by a splitting crack which divides the base material into two parts. This kind of failure occurs when the dimensions of the concrete component are limited or the anchor is installed close to an edge. • Blow-out failure: failure is characterized by the lateral spalling of concrete in the proximity of the anchor's head. This kind of failure occurs for anchors (prevalently cast-in-place) installed near the edge of the concrete element. In design verification under ultimate limit state, codes prescribe to verify all the possible failure mechanisms. File:Steel Failure.png|Steel failure The studs are typically so short and stiff that under a direct shear load, they bend causing contemporarily crushing in front of the stud and a crater of concrete behind. In design verification under ultimate limit state, codes prescribe to verify all the possible failure mechanisms. Group of anchors In order to increase the load-carrying capacity anchors are assembled in group, moreover this allow also to arrange a bending moment resisting connection. For tension and shear load, the mechanical behavior is markedly influenced by (i) the spacing between the anchors and (ii) the possible difference in the applied forces. Service load behavior Under service loads (tension and shear) anchor's displacement must be limited. The anchor performance (load-carrying capacity and characteristic displacements) under different loading condition is assessed experimentally, then an official document is produced by technical assessment body. In design phase, the displacement occurring under the characteristic actions should be not larger than the admissible displacement reported in the technical document. Seismic load behavior Under seismic loads and there would be the possibility that an anchor is contemporarily (i) installed in a crack and (ii) subjected to inertia loads proportional both to the mass and the acceleration of the attached element (secondary structure) to the base material (primary structure). (i.e. cracking) and the most un-favorable case for anchor performance is when the crack plane contains the anchor's axis and the anchor is loaded by a positive axial force (constant during crack cycles). == Designs ==

File:Ancor bolt for concrete.JPG|Wedge type - 1 File:Betonanker.jpg|Expansion type File:Fischer FH.jpg|Sleeve type File:Metall-Fensterrahmendübel F10 M132 1756.JPG|Wedge type - 2 File:Bonded Anchor.png|Bonded anchor File:Concrete Screw.png|Concrete screw ==See also==