What is an anchor bolt?
Cast-in-place anchors, such as headed, J-shaped or L-shaped bolts, are positioned in the formwork before the concrete is poured and develop their strength by bearing against the concrete. Post-installed anchors are fitted into drilled holes afterwards and hold by expansion, undercut or an adhesive resin. Their load capacity depends on the anchor size and depth, the strength and condition of the concrete, and the spacing and distance from the concrete edge.
Listed manufacturers
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List your companyAnchor Bolt or ordinary bolt?
An ordinary bolt joins two steel parts through holes. An anchor bolt must transfer load into concrete, so it depends on embedment, the concrete strength and the distance to edges, and its design and installation need more care.
What to specify when you ask for a quote
- Type: cast-in, expansion, undercut or chemical anchor.
- Diameter, length and embedment depth for the load.
- Material and grade, and the coating or galvanising for the environment.
- The loads: tension, shear and combined, and any seismic or fatigue effects.
- Concrete strength and condition, spacing and edge distances.
- Approvals or test data for post-installed anchors, and the installation procedure.
Where it is used
- ConstructionFixing columns, plates and equipment to concrete.
- Industrial MachineryAnchoring machines and frames to foundations.
- Renewable EnergyFixing structures and towers to foundations.
Frequently asked questions
What is the difference between cast-in and post-installed anchors?
Cast-in anchors are set before pouring and give high loads when placed correctly. Post-installed anchors are fitted into drilled holes later, which gives flexibility when positions change or for retrofit.
What affects anchor strength?
The size and embedment, the concrete strength, the edge distance and spacing, and the quality of installation, including hole cleaning for chemical anchors.
How should anchors be protected from corrosion?
With galvanising or stainless steel where exposed to moisture or chemicals, and by sealing the base properly. Choose the protection for the environment.
Who designs anchor connections?
A structural engineer should design them for the loads and the concrete, following the applicable code, and the installer should follow the manufacturer’s instructions closely.