Choosing Concrete Anchor Bolts
Anchors need to be used in many different types of construction, and the concrete anchor bolt plays a vital part in the integrity of the building.
While this type of hardware can be found in commercial office buildings made of concrete, they are also common in residential uses for anchoring foundation to the framing plates, footers, or directly to a slab. Various types of bolts will be used depending on whether the application is static, dynamic, or will experience frequent or constant vibration.
The installation methods depend on the types of bolts and what they are used for. The most difficult to install, but the strongest, are cast-in-place bolts. These bolts need to be poured on the spot they are used, directly into the concrete, creating an incredibly strong bond. However, this is not very practical for every location, so a wider variety is needed.
Wedge bolts are a hefty alternative. These bolts are designed for heavy loads, and use a machine threaded bolt which expands the anchor as it sinks in. These anchors are low profile for flush mounting. These are inserted into the concrete by drilling holes of the same diameter as the threaded bolt, and then driving the hardware in.
As it is tightened, the action of the nut tightening against the washer causes the pronged end of the shaft to expand and wedge tightly against the inside of the hole. Every wedge has a minimum length it needs to be embedded in order for it to function at its maximum strength; driving the wedge anchor deeper will make it even stronger.
For practical reasons, namely that of building integrity, concrete anchor bolts are coated in rust resistant zinc alloy, and some are even treated to a ‘hot-dipped’ galvanizing process for extra protection. The last thing a contractor wants is for structural problems to occur due to rusting bolts.