Bryan Carroll discusses 'The design and installation of anchors' – an Irish Concrete Society and Engineers Ireland joint technical seminar that will be held on February 25.
Use of connections employing fasteners for the transfer of heavy and concentrated loads in concrete structures is routine practice for designers. A myriad of different types of cast-in and post-installed fasteners are available to cover the wide range of structural fastening applications both safely and economically.
Improves productivity on the construction site
The correct use of fasteners is beneficial in the construction process and improves productivity on the construction site. Their safe performance in their field of application is verified by means of prequalification and assessment procedures issued by approval bodies and stated in corresponding European Technical Product Specifications such as European Technical Assessments (ETAs) presuming proper installation.
The understanding of the behaviour of structural fastening systems, the range of the fields of applications and the design methods and installation procedures have made significant advances in the past three decades.
Although a large number of fasteners are installed every day, understanding in the engineering community about their working principles and design is very limited even though study programmes and in-service training modules exist. Therefore, fasteners are not always best used in daily practice.
In my daily work I still encounter installers who don’t fully understand the correct method of installing anchors and design engineers who don’t fully understand the content of EN 1992-4.
Many of the anchor suppliers offer installation training via 'toolbox talks' and 'lunch and learn' sessions to help installers better understand how to correctly install cast-in and post-installed fasteners.
They also offer CPD seminars to enable design engineers to better understand the prequalification and assessment procedures as outlined in EN 1992-4.
Many suppliers offer software to verify that the proposed anchor system can safely satisfy the design requirements provided by the design engineer in the intended conditions, presuming proper installation.
These software packages generate reports for the designer following the prequalification and assessment procedures as outlined in EN 1992-4. The reports will look similar to the illustration shown here. Unfortunately, in many cases the designer cannot follow the content of the report as they have little knowledge of the content of EN 1992-4.
Integrity of software
This, of course, makes it impossible for the designer to have any degree of confidence in the content of the report leaving many having to put their confidence in the integrity of the software.
The purpose of the webinar will be to further explain the prequalification and assessment procedures as outlined in EN 1992-4 so that the designer can have a greater understanding and be totally confident with the content of any such report. They may even learn to generate their own reports.
When any steel to concrete connection covered by the scope of EN 1992-4 is loaded in tension to the point of failure, the failure mode could be any of a number of possible failure modes. Mostly it will fail by way of concrete failure. Table 7.1 of EN 1992-4 outlines all the possible failure modes in tension and the required verification for each.
In the pages following table 7.1 the code explains in detail how to calculate for each mode of failure. After checking the possible failure modes relevant to your application, the one with the least capacity becomes decisive. It determines the design resistance in tension of the connection in that application.
Changing things like the concrete strength or condition (tension or compression) can greatly influence the design resistance of the connection.
When any steel to concrete connection covered by the scope of EN 1992-4 is loaded in Shear to the point of failure, the failure mode could be any of a number of possible failure modes. Mostly it will fail by way of concrete failure. Table 7.2 of EN 1992-4 outlines all the possible failure modes in shear and the required verification for each.
In the pages following table 7.2 the code explains in detail how to calculate for each mode of failure. After checking the possible failure modes relevant to your application, the one with the least capacity becomes decisive. It determines the design resistance in shear of the connection in that application.
Changing things like the concrete strength or condition (tension or compression) can greatly influence the design resistance of the application.
A better understanding of the correct design and installation of anchors by all duty holders will ensure successful connections and a higher level of confidence and safety.
Click here for more information on the upcoming Irish Concrete Society and Engineers Ireland joint seminar – The Design and Installation of Anchors on February 25 or contact the Engineers Ireland CPD Training team at +353 1 6651305 or email: cpdtraining@engineersireland.ie
Author: Bryan Carroll, managing director, Masonry Fixings. This is the sixth of my Anchor Watch articles, if you have missed any of the previous five you can access then on https://www.masonryfixings.ie/articles