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Anchor Rod
An anchor rod (also called an anchor bolt) is used to attach objects or structures to concrete. There are many types of anchor rods, consisting of designs that are mostly proprietary to the manufacturing companies. All consist of a threaded end, to which a nut and washer can be attached for the external load. Anchor bolts are extensively used on all types of projects, from standard building to dams and nuclear power plants.
The simplest anchor bolt is a cast-in-place anchor. Most designs consist of a standard bolt with a hexagonal head, which is cast in the wet concrete before it sets. There are other designs, some consisting of a bent bolt with a hook on the end, or some other sort of bending. Cast-in-place anchor bolts are the strongest type of fastener, but the casting is difficult, and they are usually only used with base plates on steel columns or heavy machines mounted on poured concrete floors. Another use of this anchor bolt is to connect the concrete foundation of a building to its wall. With this, the building is more resistant to earthquakes.
Once the concrete has been poured and set, the only other types of bolts that can be used are mechanical and epoxy bolts. Epoxy bolts are the strongest, but can be very tricky to install, since the epoxy has to be mixed to exact specifications, the hole must be very clean, and the set time has to be watched. As well, there must be a rigorous testing program. In Boston's Big Dig project, these procedures were not well carried out, which resulted in a large concrete slab crushing a motorist.
The use of the term anchor rod as opposed to anchor bolt is a relatively new development brought about by the apparent inability by design engineers to distinguish between ASTM specifications for bolts and rods. Many engineers call for A325 bolts when specifying anchor rods only to find that you cannot purchase two foot long A325 bolts with six inch long threads. AISC is adamant about using the term “anchor rod” instead of “anchor bolt” in order to clear up the misunderstanding of many people between the specifications for bolts and anchor rods. ASTM F1554 is the governing specification for anchor rods. This specification covers both materials and manufacturing for anchor rods as opposed to material and manufacturing for bolts. A307 and A36 are rod specifications that may be used. A449 is a material specification that may be used. A325 and A490 are specifications that govern high strength structural bolts, not anchor rods.
Detailers should lead the way in asserting that “anchor rod” is the correct terminology as we are usually in the forefront of correcting misunderstanding in the steel industry. We pay attention to the “details.”
