The International Building Code released in 2006 states that structural anchors used in buildings must be designed using the “Ultimate Strength Design” method. In simple terms, this code ruling means that if conditions exist where concrete is likely to crack, any building fasteners used in that concrete must meet certain specifications.
Cracked Concrete Causes
Designers and contractors must specify and install specialty building fasteners when crack-causing conditions are discovered. Cracks commonly occur when concrete is under tension, such as on the bottom of a concrete slab.
External loads, such as extremely windy conditions or seismic activity, can cause cracking, even when those loads are only present in the short term. Extreme swings in temperatures can cause cracking, as can significant shrinking while the concrete is in the curing stage.
Specialty Building Fasteners To Be Used
Wedge anchors and sleeve anchors are often used in concrete applications, as are drop-in anchors and tapcon screws. Other types of screw anchors may be used as well.
When a high risk of concrete cracking is present, only building fasteners that have been tested for use in cracked concrete should be used. Specialty bits may be required, although some manufacturers have introduced stronger product lines that are installed with standard bits.
Look for wedge anchors with stainless steel clips. Not only will these products offer better corrosion resistance, but stainless steel is also known to have an improved memory, which increases performance when the space around the anchor opens up due to cracking.
Adhesives can also be used for anchoring on concrete, and the same method applies. Ultimate Strength Design states that stronger adhesives should be used where the risk of cracking is high. Look for products that have been approved for use with all types of concrete applications, including those that will experience movement, pressure and external loads.
The 2006 IBC covers many different situations where specialty building fasteners need to be used. Designers and contractors should be aware of the conditions that exist on site, and when the risk of concrete cracking presents itself, the specialty fasteners outlined above are required by code.
Started my career in the fastener world in 1969 at, Parker Kalon Corp. a NJ based screw manufacturer located in Clifton, NJ working in inventory control, scheduling secondary production and concluding there in purchasing. In 1971 I accepted a sales position at Star Stainless Screw Co., Totowa, NJ working in inside sales and later as an outside salesman, having a successful career at Star I had the desire with a friend to start our own fastener distribution company in 1980 named: Divspec, Kenilworth, NJ. This was a successful adventure but ended in 1985 with me starting Melfast in August 1985 and have stayed competitive and successful to date. Melfast serves the OEM market with approximately 400 accounts nationally.