Anchor Bolts

Anchor bolts are usually used to connect non-structural and structural elements to concretes. The connections are made by an assembling of different components such as: steel plates, anchor bolts, and stiffeners. Anchor bolts are designed for transferring different types of loads like tension forces and shear forces. The connection between structural elements are represented by steel column attached to the reinforced concrete foundation. Usually, non-structural elements are attached to a structural one which is represented by the connections between facade systems and the reinforced concrete walls.

Types

Cast in place

The strongest and simplest form of an anchor bolt is cast-in-place. Its embedded end consisting a standard hexagonal washer and head bolt, 90 bend, forged or welded flange. They are used in concrete – steel composite structures as shear connectors. Other fields of use include anchoring machines to poured concrete floors and buildings to concrete foundations. Many typical disposable aids are produced to secure and align these anchors to concrete. Their position must be coordinated with the reinforcement layout. Various types of CIP anchors might be distinguished.

  • Lifting inserts: Which are used for lifting operations of pre stressed or plain RC beams.
  • Anchor channels: Which are used in precast the concrete connections. The channel can be hot-rolled or cold-formed steel, shaped in as T screw is placed to transfer the load to the base material.
  • Headed Studs: Which consist a steel plate with headed studs welded.
  • Threaded sleeves: Which consist a tube with an internal thread. Which is anchored back into the concrete.

For all types of cast in place anchors, the load transfer mechanisms is a mechanical interlock, the embedded part of anchors in concretes transfer and the apply load with bearing pressure at the contact zone. At failure condition, the level of the bearing pressure can be higher than 10 times of the concrete compressive strength, if pure tension force is transferred, Cast-in-place anchors are also utilized in masonry applications, placed in wet mortar joints during cast blocks and laying of brick.

 

Post-installed

Post installed anchors can be installed in any required position of hardened concretes after drilling operations. Distinction can be made according to principle of the operation.

Mechanical Expansion anchors

 

Force transfer mechanisms are based on friction of the mechanical interlock, guaranteed by expansion forces.

  • Torque controlled: inserted into the hole and secured by a torque to the head of the bolt or nut with a torque wrench.
  • Displacement controlled: consists a conical expansion plug and an expansion.

 

Undercut anchors

Force transferring mechanisms are based on the mechanical interlocks. Drilling operation allows to create a contact surface between the anchor head and the hole’s wall where bearing stresses are exchanged.

Bonded anchors

Force transferring mechanisms are based on the bond stresses provided by binding materials. Both threaded rods and ribbed bars can be used and change of the local bond mechanisms can be appreciated experimentally. On ribbed bars, the resistances are prevalently due to shear behavior of the concrete between two ribs whereas threaded rods friction prevails. Bonded anchors are referred as chemical anchors or adhesive anchors. Anchoring materials are adhesives, usually consisting of vinyl, polyester or epoxy resins. This anchor’s performance types of load bearing capacity under tension loads, is related to cleaning conditions of holes. Experimental results shows that the reduction of the capacity is up to 60%. The very same applications also for moisture condition of concrete. For wet concrete the reduction is using 20% polyester resin. Other issues are represented by high temperatures behaviors and creep responses.

Screw anchors

The force transferring mechanisms of the screw anchors are based on the concentrated pressures exchange between the screws and the concretes through the pitches.

Tapcon screws

Tapcon screws are popular anchors which stand for self-threading concrete screws. Larger diameter screws are called as LDT’s. This type of fastener requires pre-drilled holes using a Tapcon drill bit and then screwed into holes using a standard hex or Philips bit. These screws are often white, blue, or stainless. They are also seen in marine or high stress applications.

Plastic anchors

Their force transferring mechanisms are similar to mechanical expansion anchors. Torque moments are applied to screws which are inserted in plastic sleeves. As torques are applied, the plastic expands the sleeve against the sides of the holes acting as expansion forces.

Powder-Actuated anchors

They act as transferring the forces with mechanical interlocks. This fastening technology is used in steel to steel connections, for instance to connect cold formed profiles. A screw is inserted into the base material with a gas actuated gas gun. The driving energy is provided by firing a combustible propellant as powder form. The 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

  • Steel failure: Weak parts of the connections are represented by the rod. The failure corresponds to the tensile breakout of the steel as in case of tensile testing.
  • Pull out: Anchors are pulled out from drilled holes partially damaging the surrounding concrete. When the concrete is damaged the failure is also indicated as pull through.
  • Concrete cone: after reaching the load bearing capacity, a cone shape is formed. Failures are governed by cracks growth in concretes. These failures are usually occurs in pull out test.
  • Splitting failure: Characterized by a splitting crack which divides the base material into two parts. These failures occur when the dimensions of the concrete components are limited or anchors are 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. These failures occur when anchors installed near the edge of the concrete elements.

 

Modes of Failure in shear

  • Steel failure: Rods reach the yielding capacity, then rupture occurs after development of large deformations.
  • Concrete edge: Semi conical fracture surfaces develop originating from the point of bearing up to the free surfaces. These failures occur when anchors in the proximity of the edge of the concrete members.
  • Pry out: Semi conical fracture surfaces develop characterize the failures. The pry out mechanisms for cast in anchors usually occur with very short, stocky studs. The studs are typically so short and stiff that under a direct shear load. Their bend causing contemporarily crushing in front of the stud and a crater of concrete behind.

Combined tension/shear

When contemporarily tensions and shear loads are applied to anchors, failures occur earlier with respect the uncoupled cases. In current design codes, a linear interaction domain is assumed.

Group of anchors

In order to increase load carrying capacities, anchors are assembled in groups, moreover, this allows also to arrange a bending moment resisting connection. For tension and shear load, mechanical behaviors are markedly influenced by the spacing between the anchors and the possible differences in the applied forces.

Service load behavior

Under service loads, anchors’ displacements must be limited. Anchor performances under different loading conditions are assessed experimentally. In design phase, displacements occurring under the characteristic actions should not be larger than admissible displacement.

Seismic load behavior

Under seismic loads, there would be a possibility that anchors are contemporarily installed in a crack and subjected to inertia loads proportional both to the mass and the acceleration of attached elements to base materials.

  • Reverse Shear load: force perpendicular to anchors’ axis, positive and negative depending on arbitrary sign conventions.
  • Cyclic Crack: RC primary structures undergo in severe damage conditions and the most unfavorable cases for anchors’ performances are when the crack planes contain the anchors’ axis and the anchors are loaded by positive axial forces.

Exceptional loads behavior

What differs Exceptional loads from ordinary static loads is their rise time. High displacement rate is involved in impact loading. Regarding to steel to concrete connection, some examples consist in collision of vehicles on barriers, connected to concrete base and explosions. Apart from these extraordinary loads, structural connections are subjected to seismic actions, which rigorously have to treat with dynamic approach. Seismic pull out action on anchors can have 0.03 seconds of rise time. On the contrary, in a quasi-static test, 100 second may be assumed as time interval to reach the peak load.

 

These anchor bolts are driven into the supporting structure, like a wall or the like and rigidly secured therein.

That is another object of the invention to provide stated anchor bolts these can be rapidly and easily driven directly into the supporting structure without boring a hole. These type of anchors are simple in construction, and economical.

These types are sufficiently strong to withstand deformation upon driven into a supporting structure, such as drywall construction, plasterboard, plywood or the like and does not damage surrounding area of supporting structure. With the objects in view, the invention resides in the novel features of arrangement, construction, form and combination of parts.

This described invention, which is claimed and desired to secure by Letters Patent is:

  1. Anchor bolts are comprising an elongated tubular sleeve, which is formed of malleable metal and including first and second axially spaced collars. These are integrally connected by a plurality of axially extending bands. First collar is having a plurality of outwardly extending wall engaging flanges. These wall penetrating prongs mean integrally formed on each flanges and extending toward. Second collar, each of axially extending bands are consisting two angularly inclined relatively straight sections. One section is connected to first collar and the other is connected to second collar. The point of connection of two band sections is forming a common apex section that is having a preformed indentation. The band section connected to the second collar is having a longer axial length than the band section connected to the first collar. The band section is connected to the second collar also which is having the band section connected to the first collar. An internally threaded nut is rigidly and permanently secured to one end of the second collar, nut is having an external tapered end portion projecting axially from the second collar. With a direction away from the first collar and a bolt axially extending through the sleeve. Mentioned bolt is having a threaded portion which is adapted for removable engagement with the nut. This bolt is being integrally formed with a piercing point that has a plurality of flat surfaces. So, that lines of intersection arranged between adjacent flat surfaces are approximately continuations of the tapered end portions of the nut. The Piercing point is being adapted to extend through and project beyond the nut. Whereby the bolt, nut and sleeve can be driven as a single unit through an initially imperforate wall forming element, such as plaster, plywood, wallboard or the like.
  2. These types of anchor bolts, which have a nut that is welded within the second collar like defined in claim 1.
  3. An anchor bolt is comprising an elongated tubular sleeve formed of malleable metal. It is including first and second axially spaced collars, which are integrally connected by a plurality of axially extending bands, mentioned first collar is having a plurality of outwardly extending wall that is engaging flanges. Wall penetrating means that formed on each of the mentioned flanges and extending toward the mentioned second collar. Each of mentioned axially extending bands that are consisting of two angularly inclined relatively straight sections. One of the mentioned sections connected to the mentioned first collar and the other mentioned sections is connected to mentioned second collar. The point of connection of mentioned two band sections are forming a common apex section which is having a preformed indentation. The band section is connected to the second collar which is having a longer axial length than the band section that is connected to the first collar. The band section is connected to the second collar that is also having a minimum circumferential width, which is greater than the maximum circumferential width of the band section that is connected to the first collar. An internally threaded nut rigidly and permanently secured within the one end of the second collar. Mentioned nut having an external convergent tapered end portion projecting axially from the second collar in a direction away from the first collar and a bolt axially extending through the sleeve. Mentioned bolt is having a threaded portion that is adapted for removable engagement with the nut. Mentioned bolt is being integrally formed with a piercing point that is having a plurality of flat surfaces, so that is arranged that the lines of intersection between the adjacent flat surfaces are approximately continuations of the tapered end portions of the nut. Mentioned piercing point is being adapted to extend through and project beyond the nut, whereby the bolt, nut, and the sleeve can be driven as a single unit through an initially imperforate wall forming element such as wall board, plaster, plywood, or the like.

As seen, Anchor bolts are used in variety of places as a fastener. Especially, Anchor Bolts are commonly used in construction field. It is very important to be served by experienced supplier of anchor bolts, because this supremely important field must be managed by professional engineers and experts. Kasko Makine will provide you the right products you need with high quality options. Please contact us for your needs and check our website for further details and other products.

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