S02 E12 - Ho Ho Vienna - Richard Woschitz, Woschitz Group

Adam Jones

HoHo Vienna, is the world's tallest wooden tower, standing at 24 floors and 84 metres in height, and is a great example of how we can combine concrete and timber, to achieve the best solution for mid to high-rise buildings. Richard Woschitzoschitz started The Woschitz Group and is a structural engineer for the project. Today we're going to speak to him about the structural system and the feasibility for high-rise timber buildings, the importance of including fire authorities for innovative projects, and managing moisture during the construction process. I thoroughly enjoyed the conversation with Mr. Woschitz, I'm sure you're going to enjoy, too. So, without any further ado, here is the interview.

Richard Woschitz

Yes, Hoho is something, because it is very interesting project. Was built in Austria in a new district, called the Lake City from Aspen. It's a special district of Vienna. And the government says, "How can we make some very interesting pilot project for the future of this place?" Then our company has make the structural engineering, making the idea, how can we make a skyscraper, or wood high-rise buildings in wood construction. The architecture was Professor Rudy Galina, before he planned this great building, he didn't plan as much great buildings in wood. Here I was, 1996, an Assistant of the Institute for Timber Structural Instruction Engineers at the Technical University of Vienna.

And I told employees when I started, our first idea of our own, we must look how we can work together because must be always be in semblance between the architecture and the engineer before we started this great building. And I told them please, give all my information for the engineering and also for the material we put in this project. And we do this and plus we say, how can we make this project easy? The main idea was keep it simple. Keep it simple to understand. How can it flex? How can it be in the construction? Simple to understand what happened. But what happened with this special project, we wanted to find out only four elements. This is columns of the ceilings which was a hybrid between wood and concrete. This was the walls, was always prefabricated within the windows elements. And we have around all storeys a precast beam and then we connected it, this four elements without screws and without metal joining.

The second one was did you say what happened with the stability for this project is we make this combined between concrete and wood. But surely, it's not really wood construction but I think both material concrete and wood have... one to do this and one to do this... and I think it is necessary to find out how can we find and combinate between concrete and wood for being efficient element. And I think we do this on this project because for stability we take first the vertical core and make this in place with reinforcement concrete and at the same time when we make this in place in the factory we can make all pre-fabricated elements. The pre-fabricated elements was the columns, walls and lower laminated timber. These were precast each beams and these are always precast hybrid slabs.

Adam Jones:

For the stability system, so you've got a concrete core and using glulam bracing in the four... the four sides of the building as well?

Richard Woschitz

Yes correct because I think the precast... we make all precast elements in the factory. And on site we make all vertical cores with the concrete and do this in place.

Adam Jones

And you mentioned you use timber concrete composite floors, why did you choose this system out of all the ones you could have chosen?

Richard Woschitz

I chose this system because this is much more advantageous because it is better to have... you can make much more span and also have much more mass for the vibration. And I think it is a lot of much more quantitative to combinate these two materials.

Adam Jones

And you mentioned simplicity, can you talk a little bit more about what you, how you design the building so it would be more simple maybe in you know the decisions about connections.

Richard Woschitz

To conduct connections is very easy because you have only one details. And the details was on a section point that you put the columns and then we get the beams and on the beams you get the ceilings elements. And this connected very easy so that we can need only all the grout but not a metal connection.

Adam Jones

So, for the developer at the start of this project, was this going to be more expensive or less expensive than say traditional construction? And if it was... if it is more expensive why why did they choose timber too for this project?

Richard Woschitz

He wants to find a pilot project to make a point for the future on this place and offers the connect. The developer says how can you find some special idea? Can it be make a special project like architecture but it's just no, we must find much more. And then makes the deal. He wants to make this building in a wood or in a hybrid wood with construction. Sustainability is one of the point will say so the owner gives a chance for build some this big projects with the material wood. And it is one of the point and this next one, how can we work very fast, very fast on the building side and you can just do it when you make much more prefabricated, great elements. And this was the second reason that says the developer. Yes, we do this in this art of conception.

Adam Jones

So let's talk about the speed of construction. How quickly did you build this building per floor?

Richard Woschitz

Yes, we do this very quickly because we can take one week, one floor, and the whole you must say, there are five blocks. And two blocks we start in the year 2017. And I'm very interested for the legal principle. And because I find it very, very good, because you take one bricks to another and I was told to this example, please give child some Lego bricks and told him please make some skyscrapers and he will begin to the works take one bricks to another and then he will look maybe 20 centimetres or 30 centimetres, oh it looks instability in one direction and what does she do here, turn it around 90 degrees and also start with the second system. And so easy this works so easy. This was one of the idea from our construction principle. And we do this also very fast in inside so we can finish this in always one store in one week. And before we start with December all people must be much fast and fast and faster. Like it was very, very fast on the 24 stores.

Adam Jones

Yeah they keep learning.

Richard Woschitz

Keep learning and keep learning to process between two pre-fabricated that the logistic and internet support. And this was one of the best learning from all people.

Adam Jones

Can you talk about logistics and transport and how you did it and maybe some of these learnings from from this process?

Richard Woschitz

Yes, we do something on the on this three elements like the logistics, like the transport and also can do all the assembly work on the construction. And we wanted to complete first we start with some simple elements in the fabric and then we start here on building side. But it keeps very, very good. So this, our idea was keep makes it very easy. And after three, four months, it works very good. Our supplier for this project was it calls Handler, now, it is a company in Austria and work with them some another projects together and told them please we, we need only the same person from the beginning to the end. But I think it's very necessary for this special project to have a team between all persons who wants to make this special project. No, I think a good project has been done when we work at first and together and our engineers makes all this data calculation and also the technical requirements and then we goes all section sketches also vertical and some special details and we're also makes a model in a 3d model from the construction. And then we give this to the, to the suppliers engineers and they makes the detail in drawings and for also the rough drawings and then to give to us to say it's okay or not okay. These are the cooperation between our engineers, peoples with the suppliers engineers.

Adam Jones

We'll touch on the fire engineering as well where we can. How much timber was left exposed in the building?

Richard Woschitz

I think it's also necessary because the fire systems I think all over the world, the same problem. And the other says what is the real problem? Because we knows that the wood burns. But especially, we knows how it burned. We start before we begin with to plan we start with the fire department and fire thought is take this all in the first idea from the planning but the thing it is what was a good idea because the people say what you can do and for the project in Hoho, we have a fire system for 90 minutes and you can you must make a sprinkler system and in Austria the regular says that you have some maximum area field. It is 800 square metres for a closed system. And we said okay, we take it better, we only make much, much smaller areas than allowed so it makes 400 square metres area.

And this is one of the seven points who had spoke with the fire department before we begin to spend... before to begin to plan and they told us please can make some fire test before you start and we'll make two fire test. One at first before we begin the planning and the second before we begin to build in place. And those fire test was very positive. So the fire department authority was also glad and I also and all my colleagues because it's good to see how what happens when it's burned 90 minutes and we only have one special connected and the fire departments said over, no it must show that not burns inside on this connection. And it doesn't.

Adam Jones

It's probably another benefit of simple design meaning the fire testing process would be much more simple as well is that right?

Richard Woschitz

Yes, I think it must be all simple whole over the project. I think the simple idea because we have three blocks that can stability together and also the process was very simple and also the the fire test was simple. I'm take for one that's very interesting because the attention we and also the developer wants to seal the surface of the port. So, in the Hoho, the surface inside is always wood like the walls outside, all the columns, and these are the special elements for the fire resistant and this is exactly that they hit the resistant for 90 minutes. And the new record one we also have it called repost hide from the structure. So maybe one of each other columns can be failed and doesn't collapse the whole system.

Adam Jones

I'd like to talk a little bit about construction as well. How is moisture managed in the timber as it's going up?

Richard Woschitz

No, I told all the company we must finish on one day some structure because we have walls and columns and the ceilings and it will be closed and after one day on the surface we also have pin-type metres also for the water when it's raining maybe in the night. Has been measured the water in the water and we have 12% because we must look always I think it is much more problem when we have water problem, much more well.

Richard Woschitz

When it burn, we know how it burns. But when the water is entered of the wood structure, it can be really, very, very bad. So we must be looking always for all protection or for the assembly inside that we don't became water into the wood structure. Because I'm also afraid that we just see all surface for from the wood structure. Maybe like the CLT or see the glue eliminated construction, whatever. And because when this is an office I can look what happens when you have some water problem, what happens when I have some fire problem and so on. I'm not offended to collapse with chips and so on because they don't can look what happens in the construction. So I was saying it is necessary to see all open surface for the wood structure. And when the water comes in the wood structure and also about there's no problem with the wood construction. A problem has happens when it is inside and cannot outside.

Adam Jones

Yeah.

Richard Woschitz

This is the great problem for the wood structures.

Adam Jones

So we're coming toward the end now Richard. For you, what do you think the future is for timber construction?

Richard Woschitz

I think if you listen all news for the for the climate warming and seeing it is a big change for this very important material, wood because wood is produced in the friendly fabric in the forest and I see all the time is good for the future for the wood structures and I think with the Hoho, what I thought the construction system and pilot for the future. Now we have no problem to go in much more than 10 or 20 or 30 stories. It is not the static problem and I think wood structure have the big change which can mean this big advantages is that you can pre-fabricate greatest elements. And I hope, I know, because we make the idea from the Hoho, also for the next structures engineering for them how in Amsterdam.

Adam Jones

Okay, that's a very famous project as well. How tall could we build with this system using a concrete core and glue embracing at the facade, how big can we go?

Richard Woschitz

I think we can go when we do this very intelligent, I think we can go 150, 200 metres. Why not?

Adam Jones

So that's about 40 stories? 45 stories?

Richard Woschitz

This... 45 stories.

Adam Jones

So very tall buildings, okay.

Richard Woschitz

Yep, maybe can be 50 stories. Because Japanese people want to makes until 2014 a great high rise building with 300 or 350 metres high.

Adam Jones

Yeah I saw that as well. I thought maybe it was good marketing rather than reality but maybe it's reality.

Richard Woschitz

The reality I think now Hoho shows how it's gone. Has doing for 84 metres and seeing double sizes all and make this.

Adam Jones

That's exciting. Maybe a challenge for any engineers listening for this.

Richard Woschitz

Yes of course is it.

Adam Jones

If you've got a project coming up and you're not sure whether it should be timber, then the mid rise advisory programme will be able to help. One of the things we can do is a feasibility analysis. So looking at the project, from the point of view of fire costing, structural engineering, the supply and building and installation and so forth to work out whether the project is right for timber. If this is something you're interested in, then get in touch with me at Jones@woodsolutions.com.au and I'll put you in touch with the right team member.