AGG
Volume 28, Issue 3 - May/June 2014

MetalMatters

Everything in its Place
Report Addresses Curtainwall Fastener Selection
by Dean Lewis


The selection and use of proper fasteners is critically important to the safe and satisfactory performance of curtainwall systems. A unique combination of technical data and applications tutorial, the recently updated Technical Information Report AAMA TIR A9-14, provides necessary information to select and specify proper fasteners.

The information provided in this most recent AAMA update has never been more critical. To ensure that their products meet the specifications for which they are designed, it is essential that manufacturers of fasteners maintain excellent quality control procedures in their plants, and that their customers carefully determine that they are, in fact, getting fasteners that meet their specifications.

“The problem of inferior fasteners on the market has become serious over the past few years, with potentially disastrous results.”

Proper Selection
The problem of inferior fasteners on the market has become serious over the past few years, with potentially disastrous results. Many fasteners may be found to be substandard mechanically and dimensionally when checked, even though they are marked as high-performance grades.

Protective coatings on fasteners may also be a problem. As a result of more stringent environmental requirements and tightening economic pressures, fewer manufacturers are applying adequate coatings to their products. The quality and thickness of protective coatings in today’s market, particularly on low priced fasteners, has become somewhat unreliable.

These concerns became so serious in the 1980s that the United States Congress passed the Fastener Quality Act (FQA) in 1990 and amended the act in 1999. This federal law was enacted to protect the public safety where citizens were at risk due to faulty fasteners. However, the FQA covers only bolts, nuts, screws, studs and load indicating washers of ¼-inch diameter or greater or those requiring a grade mark. Products produced under a recognized quality assurance program such as ISO 9000 are exempt from this act. Architects and specifiers should consider adding this requirement to all fastener specifications.

Details Matter
In order to be certain that the fastener needed to meet design criteria is provided, the designer must not only specify fastener size and type, but also material, minimum mechanical properties, thickness and type of protective coating required. The recently published TIR-A9 document offers a fastener specification checklist for this purpose.

Given valid marketplace concerns, architects and specifiers must take into account a variety of factors when selecting proper fasteners to ensure the proper performance of curtainwall systems.


Updates and Additions
Here’s a quick top-five list of some of the updates and new information in the document. AAMA TIR-A9:

1. Adds extensive information on hydrogen embrittlement;

2. Includes a safety factors section with a thorough explanation on how the safety factors were derived for the range of fastener diameters. The intent being to provide safety factors which are conservative, consistent and simplified;

3. Updates information in Fastener Load Tables Commentary found in Section 7.0;

4. Includes tables giving allowable tension, shear and bearing loads for a range of different fastener sizes, for carbon steel and stainless steel alloys; the pull-out strength of fasteners in aluminum substrates is also addressed; and

5. Features updated and expanded information in Pull-out Strength sec-tion to include equations for thick, thin and transition regions and thread stripping of internal and external threads.


Dean Lewis is the educational and technical information manager for the American Architectural Manufacturers Association in Schaumburg, Ill.

 

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