Module Prepared and Presented by ITW Red Head Powers Fasteners EVERGREEN PREFERRED SUPPLIERS ACI 355.2 “Cracked Concrete” Test Standards International Building Code 2003/2006 Impact on the Manufacturing/Construction/Construction Supply Industry Module Prepared and Presented by ITW Red Head Powers Fasteners

What is “Cracked Concrete” It may be an exaggeration that cracked concrete issues are sweeping the construction industry, but there have been enough questions from vendors, specifiers and end-users to warrant some clarification.

What is “Cracked Concrete” The term “cracked concrete,” as it relates to concrete anchors, comes from the new building code that requires special design considerations and prequalification on anchors installed in concrete that has a possibility of cracking.

What is “Cracked Concrete” Determining which portions of concrete are susceptible to cracking is fairly complicated but, in general, cracking is expected where: 1. The concrete is in tension. A typical example of this is the underside of a suspended slab or ceiling. This is a common area of application for post-installed anchors used to support overhead bracing and hanging rod for suspended systems. 2. The concrete is located in a geographic region of moderate or high seismic risk. Structural concrete anchors in these regions are designed assuming “cracked concrete” conditions.

“CRACKED CONCRETE” Anchor is weakened As a result of crack When load is applied…the concrete deck bends & Tension is created ANCHOR STRESS CONE CRACK OCCURS in the Tension Zone TENSION (pull) TENSION (pull) Anchor is weakened As a result of crack CONCRETE FOUNDATION

What Has Changed? The Uniform Building Code (UBC) is Obsolete and is In 2003/06 the International Building code(s) (IBC) introduced “state-of-the-art” requirements for design, testing and evaluation of mechanical and adhesive anchoring systems (requirements absent from prior U.S. building codes). The Uniform Building Code (UBC) is Obsolete and is No Longer Being Enforced. The 2003/06 International Building Code (IBC) is now in place…in virtually every U.S. jurisdiction. EVERGREEN

Within the IBC International Building Code 2003/2006 There exists a requirement that mechanical & adhesive anchoring systems perform in what has been termed… “Cracked Concrete”.

The qualification and design of concrete anchors under these new criteria and requirements differ substantially from past practice, challenging designers and manufacturers to develop new products to meet the more stringent standards. As a result, concrete anchoring will be safer and end users will have a more reliable product, further preserving the structural integrity and longevity of buildings.

SO NOW IT’S HERE… What is the ACI Test Standard It is…“A Test Method for Evaluating the Performance of Post-Installed Anchors in Concrete” This important focus on the cracked concrete anchorage concept began with the introduction of the American Concrete Institute’s Standard ACI 355-2, which prescribes a comprehensive testing program to ascertain design parameters for post-installed concrete anchors used in cracked or uncracked concrete. Following ACI’s lead, the Evaluation Service of the International Code Council (ICC-ES) developed specific criteria for the testing of these structural products to meet ACI 355-2. The latest editions for post installed anchors meeting the requirements of the 2003 and 2006 International Building Code (IBC) are AC193 for mechanical anchors and AC308 for adhesive anchors.

ICC Criteria Both AC193 and AC308 permit evaluation of post-installed anchorage in cracked concrete, including seismic performance factors not previously addressed. As of January 2007, all evaluation reports on mechanical wedge anchors must comply with AC193, and by January 2008 adhesive concrete anchors must comply with AC308.

Per the (IBC) International Building Code 2003 & 2006 For purposes of concrete anchoring…the ALLOWABLE STRESS DESIGN method has been replaced with the LRFD (Load Resistance Factored Design) or the STRENGTH DESIGN method. The STRENGTH DESIGN method yields a more reliable result…than ALLOWABLE STRESS DESIGN.

Allowable Stress Design Safety Factors [OLD METHOD ] Ultimate loads were determined by testing…and then applied against a factor of safety. Fallowable = Fultimate ÷ 4 (Plus edge and space reductions…if they apply) A single anchor in concrete “TO GIVE YOU AN IDEA OF WHAT HAS CHANGED…AND HOW IT WILL AFFECT YOUR WORLD”……This is the formula for the older ALLOWABLE STRESS DESIGN method…the method that has been used by the design community for the last half century. Allowable load is an Ultimate load divided by 4…where “F” equals “Load”. Influence Cone

Based on all of these developments, it’s quite evident that the design of anchors under the new codes requires submitting a significant amount of new information. The ACI has developed a precise formula as detailed in ACI 318 Appendix D that requires specific calculations in determining the total strength of the anchor for the specified location. The anchor performance categories are used by ACI 318 to assign capacity reduction factors and other parameters.

STRENGTH DESIGN…[ NEW METHOD ] General Strength Requirements for Tension ФNn ≥ Nua Nn = the lowest value of: Nsa (Steel strength) Ncb (Concrete Breakout ) Npn (Pullout strength) Nsb (Concrete side-face blowout strength) Nua = factored tensile force applied to anchor or group General Strength Requirements for Shear ФVn ≥ Vu Vn = nominal shear strength the lowest value of: Vsa (Steel strength) Vcb (Concrete Breakout ) Vcp (Pryout strength) Vu = factored shear force Ncbg = ANc yec,N ψed,N yc,N ycp,N Nb A Nco (Load) Nu ≤ ΦNn (Resistance) Nb = kc f’c hef1.5 This is the formula for the new STRENGTH DESIGN method…and as you can see…it is considerably more complex than the older ALLOWABLE STRESS DESIGN method. (Load) Vu ≤ ΦVn (Resistance) IS SIGNIFICANTLY MORE COMPLEX 4 HOURS!! f’c = compressive strength hef = effective embedment depth kc = calibration factor = 24 for cast-in-place = 17 for post-installed The designer must work through a similar set of calculations for: SHEAR – COMBINED LOAD - SEISMIC

Some of the potential advantages of post-installed anchors qualified for the strength design method under the new code include: Increased reliability. It is expected that specifying engineers will become more confident in post-installed anchors that have obtained the new approvals based on the more stringent testing requirements. 2. Greater efficiency. One primary benefit of the strength design method is that it gives a designer the ability to control the failure mode of the anchor (whether the concrete fails, the steel breaks or other failure mode). By doing so, appropriate levels of safety can be applied using statistical analysis. Accounting for reinforcement. The new strength design method allows the designer to increase the capacity of anchors that are near reinforcement for cracked and uncracked concrete. This previously was not an option.

In Summary Professional engineers who specify anchors for use in commercial projects must now consider additional factors other than the anchor’s ultimate load. In order to determine an anchor’s load value, specifiers will need to address the different categories of testing (reference, reliability, service conditions) and failures such as steel failure, concrete failure and pull-out failure. Manufacturers can make it easier for professionals by providing their test data and creating tables within specific guidelines. Because of new standards and criteria, anchoring in concrete is safer now. Well-engineered products that meet ACI requirements by the criteria of ICC will be in high demand. Manufacturers will be forced to spend more time in their labs creating new products, improving old products and revising formulas. It will be time well-spent. As a result, professional engineers, architects and designers will have a safer, more reliable product.

Thank You ITW Red Head Powers Fasteners At Evergreen… your Preferred Suppliers ARE READY for Cracked Concrete anchoring!! Thank You ITW Red Head Powers Fasteners