3D reinforcement is easy now

Have you tried working with 3D reinforcement before? Although it’s been pretty hard to do in the past, these days it’s possible to make it fairly easy. This post covers some reasons it hasn’t been common practice and how new techniques can give us a better way of communicating concrete design.

Current Practice

Reinforcement is currently communicated as either formal drawings or sketches.

Formal documentation of reinforcement is usually taken care of with schedules, standard details and 2D section cuts in tricky areas. It’s usually considered too time consuming and difficult to model and almost never is.

Sketching is done with pencil and paper or more increasingly PDF markups in programs such as BlueBeam. Sometimes Engineers will draw sketch details in CAD but they will never model it.

Why is reinforcement not modelled?

Up until recently, communicating reinforcement has been hard.

The only way to sketch by hand effectively is by cutting sections and that’s very time consuming. It’s hard to get your head around the different beam and site levels and how each bar will fit with the others. It’s hard to communicate it too. Often, not enough sections are cut to truly understand the 3D reality that will exist on site.

Formal documentation of all of those 2D sections also takes a lot of time. The marking up and checking process is labour intensive and current documentation software hasn’t really bothered to support it to date. The newest software can do it but is is pretty slow and tricky to use.

Then incorporating changes to the design makes it exponentially more time consuming to deal with because all of the 2D work has to be re-done.

Based on this experience, most Engineers would say they want to avoid 3D reinforcement at all costs. It’s so hard to document it normally today that you would think a 3D version would be much harder.

I wouldn’t say this is true with today’s software however as I will explain further below.

Why it’s better to model reinforcement

The number one reason modelled reinforcement is better is that it’s the best way of communicating the design. They say a picture tells a thousand words and I would say a model can tell a thousand pictures.

Currently practice documents 80% of the reo intent but leaves problem areas to be found once things don’t fit on site. These problem areas then have to be dealt with through RFI’s and site instructions. As experienced engineers know, getting into the detail early reveals problems that can be solved before they become critical later on. And there is no better way of finding potential clashes and buildability problems than seeing every bar in 3D.

The extra level of detail will also mean that more accurate reinforcement can be made. There should therefore also be less off-cuts and additional bars required to make up for omissions and cost estimates should also be more accurate and require less provisioning for waste.

Programme should be less slowed by hold ups on site.

On the design side, documentation and re-documentation can be reduced. Not only can the Engineer quickly model the bars in 3D for sketching, but the models can be transferred directly to formal drafting programs (such as Revit), which reduces double handling.

Future Practice

It’s definitely becoming easier to model reinforcement than it has been before. Software’s getting better although leading programs are still slow to make things simple or quick in my opinion.

There is one powerful way to generate structural geometry these days however and I believe it’s ideally suited to reinforcement. That technique is called Parametric Design, or Generative Design. Instead of proscribing geometry directly like you would when you draw something by hand, you instead create rules and allow the geometry to be drawn automatically.

It’s the first time it’s been easy for an ordinary Engineer to generate 3D reinforcement quickly and easily that I am aware of. It also makes it just as easy to generate formal documentation.

One of the key advantages to generating reinforcement with this method is the ability to use an ‘object model’. Rather than generating loose bars that are individually hard to control, the bars can be locked into a relationship to a structural element such as a beam or column. Then if the element moves or changes, the bars will then move and rotate to suit the rules of their placement.

Another reason modelled reinforcement may be adopted is the industries steady march towards a future without drawings. There have already been trial projects where drawings were banned and only the rebar models were used. Although this will likely be a slow movement, it will happen eventually.

Conclusion

Will the advantages of 3D modelled reinforcement convince the industry to adopt it? Or will it stay in the ‘too hard basket’ as it has in the past?

I suspect it will become much more common in the near future.

It’s already quicker, cheaper and communicates the design better so it only seems like a matter of time.