f someone were to ask what some of the unsung heroes of large steel projects are , be they highrise buildings or infrastructure construction , a lot of things might come to mind . One thing that many people do not think of , however , are the anchor bolts that keep the structures tethered to their concrete and steel supports . Anchor bolts are meant to adhere steel structural supports to concrete foundations and are used everywhere , from building columns to bridges and highway signs .
Often , people think that the footer or the foundation is what provides all of the support to a building . While that is true , it is only partially so . The main reason large pier pads or footers exist is to act as counterweights to help anchor the building to the ground by weighing it down . Metal buildings , as hard as it may be to believe , act like kites in high winds , and the only thing keeping them to the ground is the tether ( in the form of the foundation ). Thus , the anchor bolts — combined with the piers , footers , and foundation — help to tie the design of the structure together . The installation of bolts is typically optimized in the planning stages of a project and can influence the design of the foundation .
Common types of anchor bolts include L-shaped bolts , J-shaped bolts , and castin-place bolts , the last of which allow for flexibility in the location of the anchors and can be installed after the concrete has already cured . Bolts are typically
METAL BUILDINGS , AS HARD AS IT MAY BE TO BELIEVE , ACT LIKE KITES IN
HIGH WINDS , AND THE ONLY THING KEEPING THEM TO THE GROUND IS THE TETHER secured to foundations in groups of four , with each individual anchor in the group being placed through predrilled holes in a template to help maintain the correct alignment . Concrete is then poured , envelops the anchor bolts , and secures them in place . The larger the diameter of the bolt being used , the less likely the final product will be bent or headed .
The most important guideline for the use of anchor bolts is American Society for Testing Materials ( ASTM ) F1554 , which covers design , application , and types of structural steel anchor bolts . Originally introduced in 1994 , these specifications are meant to comprehensively cover the topic of anchor bolts designed for structural supports affixed to concrete foundations . They serve two primary functions : to stabilize framing during initial construction and to help with the transference of vertical and horizontal loads from the framing to the foundation after the structure is complete .
There are a few things F1554 does not cover . Omissions include requirements for the following :
• Powder-activated studs and nails
• Anchor bolts fabricated from deformed bars
• Mechanical expansion anchors
Three grades of anchor bolts are outlined , all of which designate the minimum yield strength of the steel being adhered to :
• Grade 36 : 36 ksi minimum yield strength
• Grade 55 : 55 ksi minimum yield strength
• Grade 105 : 105 ksi minimum yield strength
The end of each bolt that projects outward from the concrete it is adhering to has a color code assigned to it which designates what grade it is : grade 36 being blue , grade 55 being yellow , and grade 105 being red . Permanent grade identification markings and permanent manufacturer markings can also be specified when inquiries or purchase orders are made , but only the color coding is required .
Where the anchor bolts are positioned is also important . If they are placed incorrectly — too high or too low — they may not function properly . Many remedies exist , including extensions with couplers , cutting and rethreading , the addition of epoxy , or redrilling . The other remedy , and by far the most costly , is to remove existing concrete and repour with the bolts positioned in the right place .
Successful use of anchor bolts in a foundation comes down to following a combination of building codes , standards , and working closely with the bolt manufacturer and the foundation contractor . Everyone should work from the same benchmarks to ensure communication amongst all levels of the project .
Anchor bolts are not glamorous , but they are vital to the completion of most projects involving structural steel . Knowing what they are for and how they are used , including what applications they are right for , is vital . Ensuring that they meet the right specifications for each project and that they fall in line with ASTM F1554 is the first step in accomplishing that . Many builders wait until the last minute , unfortunately , and are left scrambling to get the right parts at the right price . It pays to include pricing and purchasing in the advanced planning phase to ensure the project builds have what they need when they need it . +
For more information about structural steel construction and the specifications outlined in ASTM F1554 , visit their website at : www . astm . org / Standards / F1554 . htm
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