How to Choose Anchor Bolts: ASTM F1554 Grades, Shapes, Embedment and Galvanizing

ASTM F1554 is the standard specification for anchor bolts in North American structural work, and it is widely used in projects around the world. It has three grades defined by their yield strength: Grade 36 (36 ksi, about 250 MPa), Grade 55 (55 ksi, about 380 MPa) and Grade 105 (105 ksi, about 725 MPa). Grade 36 is the general-purpose, low-cost choice and is easy to cut, bend and weld. Grade 55 is used when the design needs more capacity from the same diameter, and Grade 105 is used for heavily loaded base plates, such as tall masts, wind towers and large equipment.

Grade 55 can be supplied with a weldability supplement (S1) that controls the carbon equivalent, which is essential if anything will be welded to the bolt. Grade 105 is not weldable and should not be heated or bent on site. In Indian projects IS 5624 covers foundation bolts, and for metric work you will also see ISO 898-1 classes 4.6, 5.6 and 8.8 used for anchor bolts.

Always give the grade and the standard in the order. 'Anchor bolt M24' without a grade usually gets the cheapest option, which may be below what the engineer designed.

The shape decides how the bolt holds in the concrete. An L-bolt has a 90-degree bend at the bottom and a J-bolt has a bend with a larger radius, and both are cheap and common in light structures, signs, fences and small columns. The weakness of hooked bolts is that their pull-out strength relies on the bearing of a small bend against the concrete, and under heavy tension the hook can straighten and the cone of concrete breaks out.

A headed bolt, with a forged or welded hex head or a square plate, or a bolt with a nut and washer plate at the bottom, spreads the load over a large area and is the right choice for high tension, such as columns that resist uplift or overturning. Where the bolt must carry both pull-out and shear, headed anchors are the standard answer for structural steel base plates.

• L-bolt / J-bolt: light structures, fencing, signs, equipment pads under low uplift.
• Headed bolt or plate anchor: steel columns, tanks, towers, crane rails and any joint with significant uplift.
• Straight bolt with nut and plate: when the bolt may need to be adjusted or when a template is used for accuracy.

The total bolt length is the sum of three parts: the embedment depth in the concrete, the projection above the concrete, and the thread length for the nut. The embedment depth is set by the structural engineer from the load, the bolt diameter and the concrete strength. The projection must cover the grout thickness, the base plate, the washer, the nut and about two to three threads of extra length beyond the nut.

A common site problem is a bolt that is too short by a few millimetres, because the grout gap was larger than expected or the double-nut levelling system was not allowed for. Add this allowance when you specify the length, and agree with the contractor whether the length is measured from the underside of the head or the plate.

• Thread length at the top end: enough for the leveling nut, the base plate, the top nut and the extra threads.
• Edge distance and spacing: the bolts must sit far enough from the concrete edge, which the designer controls.
• Template: use a steel or plywood template so the bolt group lands where the base plate holes are.

Anchor bolts often live where water collects: at the foundation, below the grout. Plain steel bolts embedded in sound concrete are protected by the alkaline concrete, but the exposed top part and the area just below the surface can rust. Hot-dip galvanizing to ASTM F2329 or ASTM A153 gives the top section a long life in outdoor, coastal or industrial conditions, and is the usual standard for bolts we supply.

Galvanized bolts need nuts that have been tapped oversize to fit, so order nuts and washers together with the bolts. Galvanizing the embedded section is useful in humid or corrosive ground, but note that it affects the bond between the concrete and a straight bolt, which is why designers rely on the head or plate for pull-out rather than on adhesion.

Heavy hex nuts to ASTM A563 (see our hex nuts guide) are the usual match for F1554 bolts: grade A with Grade 36, and grade DH or C with Grade 55 or 105 where the design calls for it. Add a hardened flat washer under the nut (see our washers guide), particularly if the base plate has oversize holes. Most erectors use two nuts under the base plate for levelling and one above, so order three nuts per bolt unless told otherwise.

Check the diameter, the overall length, the bend radius and the thread length against the drawing. Ask for a mill test certificate that shows the grade and the heat number. If the bolt is galvanized, check the coating thickness with a gauge and look for runs, bare spots and thread damage. Mark and bundle the bolts by type and length, with a tag that carries the project reference, because a bundle of mixed lengths on site is hard to sort.

For weldable or special-grade bolts, make sure the certificate includes the supplementary requirements you ordered, such as S1 for weldability or S5 for charpy impact tests in low-temperature service.

Global Fasteners Exports is a trading and export company: our anchor bolts are made by partner factories and we handle inspection, packing, documents and shipping. Because we buy in volume from those factories, prices are typically up to 30% lower than the market price.

For anchor bolts, a bolt schedule with shape, grade, diameter, length and thread length is the best enquiry; we quote galvanizing, nuts and washers with it.

Anchor bolts can be up to several metres long, so we pack them in bundles or wooden crates sorted by length and mark, with threads protected. Send the drawing or a bolt schedule and we confirm lead time, galvanizing and the container load.

• Samples or detailed photos can be arranged before a bulk order; sample and courier costs are normally adjusted against the first order.
• Standard payment terms are 50% advance to confirm the order and the balance before dispatch.
• Documents: commercial invoice, packing list, certificate of origin and bill of lading, plus mill test certificates and inspection reports on request.
• Different products can be combined in one consolidated FCL or LCL shipment.