As you can imagine, much innuendo stemmed from the name. We also relished the impressive “˜Ceremony of the Tool’ that required at least two of us uni students to lift the thing. The spanner was so massive it could have withstood a direct nuclear strike.
Unfortunately, life at university didn’t get much more interesting than that. The reputation of university students for “˜wine, women and song’ was won largely by the arts students, with the doctors following close behind. With about 35 contact hours a week and almost no female engineers in our class, there just wasn’t much incentive for excessive fraternisation.
Alas, life in the building industry is all about work, with very few extra-curricular activities. My wife, who works in the pharmaceutical industry, has had trips to all manner of places around the world and endless freebies. In almost 30 years of engineering practice, I once got a free chicken lunch from Humes.
And so, alas, this article is about something as equally dry as my study days. But like our work, it’s important.
The issue of balustrade safety is one that continues to haunt the building industry. If an element of a building is likely to kill a bunch of people, it is as likely to be the failure of a balustrade as much as any other element. The “˜other element’ could include regular building failures, such as metal corrosion or timber degradation. With issues regarding balustrade, failure could be due to a crowd load pressing against a dodgily constructed balustrade.
Even for a domestic situation, the required failure load for a balustrade is about 50 kg horizontal load per metre length of handrail. This could happen when people at a party (no doubt of the aforementioned arts students) get a bit wild and crowd against the balustrade to see some raucous sight below.
If your post spacing is 3 m, this means each post has about 150 kg horizontal at its top. And with a height of 1 m the post is applying a twist onto the floor structure close to the maximum torque that our students’ Rigid Tool ever managed to apply in anger.
If it takes a massive steel tool to apply that torque in a workshop, you can imagine that it’s really quite difficult to resist that twist when you are connecting to the end or sides of some timber floor joists. The strength of the fixings are the limiting feature.
The required load to be resisted is even higher in public spaces and it is simply massive if the area of the building is susceptible to crowd loads. And so the design problem gets harder. In fact, these connections are problematic even with steel structures.
If you are providing a floor frame and there is some sort of proprietary balustrade system, then I think it should be up to the balustrade provider to make sure it can be connected for adequate strength to the floor. They will most likely need some sort of bracket running along the floor joists or some very considered detailing.
Having said that, there is a fair chance that the balustrade supplier will make no attempt to ensure an adequate fixing beyond providing some bolt holes in a base plate. And so the problem occurs at the interface between trades and suppliers. In this situation, it could well be in your interests to make sure that it is clear who is designing the balustrade and its fixing system.
However, if you are fabricating and supplying dwarf stud walls as balustrading and the floor structure then, in my opinion, the responsibility to ensure a safe structural design falls fair and squarely in your court. It’s not just something that you can farm off “as per AS1684″ because those details just aren’t in there.
In fact, its nigh on impossible to get a good enough structural connection between a balustrade that has been framed like a stud wall and a floor system without introducing some additional structural elements. We need balustrades to last safely. If you are supplying the balustrade, in my opinion you need to get the structure and its connections engineered.
My university days are a mere memory now, along with legwarmers, Boy George and Ronald Reagan. But I have absolutely no doubt that the Rigid Tool mascot still survives at my uni. It will be there until the apocalypse! Paul Davis is an independent structural engineer managing his own consulting firm Project X Solutions Pty Ltd. The views in this column are Paul’s and do not reflect the opinions of TimberTrader News.
Phone: 02 4576 1555 I Email: pauldavis@timbertradernews.com
