The Galvanizers Association of Australia has released a best practice guide on bolted structures and their characteristics, advantages and economics.
With galvanized bolting being a widely-used economical, reliable and easy way to fasten structures, this guide is a must-have for engineers working with steel. This best practice guide also covers a range of Australian Standards that apply to design, construction and fasteners.
In bolted steel structures, the bolts, nuts and washers are all critical items on which the integrity of the structure depends. Bolting is the major alternative to welding for connecting structural steel. The main advantage over welding is that bolted structures are easier to maintain or dismantle and reuse for projects with a circular economy focus.
According to a recent guide from Austroads, road authorities in Australia prefer bolted connections as the quality of site welds can be more difficult to guarantee and welding may also damage the protective coating. Other advantages of using bolted connections include the cost, speed and ease of erection, reliability in service and requirement for fewer and less highly skilled operators.
For bolting, a number of Australian Standards apply. These cover off design and construction standards and those for fasteners. The guide outlines each one and shows some of the major updates that have been made recently, as well as their international equivalent. Fastener standards have been updated in major revisions to the Australian Standards, such as AS/NZS1252 which was revised in 2016. There have also been follow-on updates to other standards such as AS/NZS 1214 Hot dip galvanized coatings on threaded fasteners (ISO metric coarse thread series) so that these align with the changes. The guide also includes a review of the recent European research on slip factors, showing the methods required to obtain an increased slip factor for galvanized steel structures.
Dr Peter Key at the Australian Steel Institute has led the development of updates to Standards before, most notably around AS/NZS 5131 for structural steelwork fabrication.
“From time to time, we do revise national standards, as we uncover new information, data or circumstances that require changes to the standard. It’s important to stay up-to-date and with changes to a number of the Australian Standards that involve bolting, a guide like this one from Galvanizers Association can help keep you across the critical components,” said Peter Key, National Technical Development Manager, Australian Steel Institute.
“In the case of AS/NZS 1252 High Strength Steel Bolts with associated nuts and washers for structural engineering, revision was necessary because most of the bolts are no longer made in Australia. As companies are still demanding that quality needs to be shown as a forethought across various building sites, it was necessary to better define product conformance and how to assess it in the Standard,” added Key.
The Galvanizers Association of Australia is the industry association for hot dip galvanizing companies in Australia. It provides free technical publications and practical assistance on design, application, process, bolting, welding and painting of galvanized steel.
The guide provides an overview of the Australian Standards as well as best practice for bolted steel structures, structural fasteners and bolting techniques, design details, tightening procedures, inspection of fasteners and covers a range of selection of zinc coatings for bolts. It also provides additional notes about the influence of hot dip galvanized coating on design, particularly for slip factors, fatigue behaviour, bolt relaxation and torque and induced tension in tightening.
You can download the Bolting Best Practices guide from the Galvanizers Association of Australia under the Design Guides section at gaa.com.au/technical-publications.
