Outsiders often think of the Benelux countries— Belgium, the Netherlands, and Luxembourg—of Northern Europe as being fairly similar. While they do have many cultural and historic links, their tower crane markets are markedly different from each other.
Heavy towers
Frank Crombe, marketing manager for Kranenbouw explains, “Belgium tends to use a lot of self-erectors of all sizes, mainly for private houses and small buildings. It uses a lot of city cranes from 70tm to 120tm for apartments and renovation works in cities and at the Belgium coast, in cities like Oostende and Knocke. As thesecranes’ operators can work without a permit it has made the use of this size of cranes popular.
“Brussels is an exception, where big projects using pre-cast concrete and with short building time call for heavy duty cranes. This is a mixed market with contractors still purchasing cranes. Rental in Belgium accounts for approximately 70% of the market.
“In the Netherlands, it is the contrary. Up until recently, crane drivers were very expensive to use in the Netherlands: up to EUR1,600 a week. The reason is that crane drivers needed a license, which was a long (1 year or more) and difficult process to get. This has favoured the use of heavy pre-casts and heavy benches, forms and even some special techniques such as the’ tunnel forms’’ for apartment building. Therefore, tower cranes tend to be heavy duties. For example, the rental fleet of Kranenbouw in the Netherlands is mainly composed of 120tm–400tm tower cranes.
“Self-erectors are seldom used in the Netherlands, except on crawlers or on trucks (Spierings, MTC) for the same reason: crane drivers are too expensive to be used on self-erectors. Around 90% of the Dutch tower crane market is rental. Nowadays it is much easier and quicker (about three weeks) to get a crane’s license, so we see more and more self-erectors coming to the Netherlands.
“Luxembourg is more like the French and Belgium market with a mix of self erectors and standard tower cranes. The construction market here has been very good and stable for the last ten years with a lot of official and office buildings: the Kirchberg plateau [home to many European banks and EU parliamentary buildings] near the airport is a good example. The Luxembourg tower crane market is 90% rental.”
Van der Spek sells and rents Liebherr’s complete range of tower cranes in the Netherlands, as well as batching plants and truck mixers, and a complete range of other construction equipment. In Belgium it also sells Liebherr mobile cranes. Managing director Erik Lubbers says, “Pre-cast concrete is used a lot in the Netherlands, a lot more than in Belgium and Germany.
“Most of the time, customers try to do everything in pre-cast pieces: beams, walls and floors. The only pouring that takes place on site is the connections between the pieces.
“A good example of this type of construction is the Het Strijkijzer (the ‘Hot Iron’ or, as in the famous Manhattan building, ‘Flatiron’, because of the footprint of the building) project in The Hague. On this project they were able to build two floors a week. A job like that, in the middle of a busy city like The Hague, with limited access, takes very detailed planning. They could only have one truck on site at a time; as soon as one truck left, the next was waiting to enter the site. It shows how quickly you can build using pre-cast if you get the logistics right.
“Everything has to be just in time. The elements have to be right every time. There is no chance to change anything once the job has started. The preparation is longer, but the execution is shorter.
“The Netherlands is a typical concrete country. Contractors don’t use steel in high-rises, and don’t have much experience working with it. They think in terms of concrete.
“The advantage is that, once the job has started, it is much quicker. You also need less labour on site,” Lubbers says. “Labour is very expensive in the Netherlands, particularly over the last few years.
“As well as the price advantages, there are a lot of established suppliers that can make the concrete elements.
“The contractors want to make the elements as big as they can transport, so up to 25t. Sometimes we have to tell them that the crane won’t be able to lift that: you can lift up to 25t, but not at all the distances they want.
“The biggest elements will be the beams and floors. Elements can have a complete finish, such as a layer of bricks, on the exterior. They can even include windows frames and glass, the water, electric and sewage systems are already in the floors and walls sometimes.”
The sizes of the pre-cast elements that need to be lifted influence the type of cranes popular among Dutch contractors. Crombe says, “At Kranenbouw, we have seen that cranes with capacities of 300tm and above, such as Liebherr 256 HC, 280 EC-H, Comansa 290 LC and 400 LC, Jost JT 312.12, Peiner SK 315 and SK 415 are almost constantly rented. We have, for example, rented recently two Comansa 400 LCs on the Rijks museum in Amsterdam, which is quite a prestigious job site. Half of our fleet is over 300tm cranes, so we are also able to answer the needs for big job sites in Belgium and Germany. We have provided the cranes for the Leverkusen Stadium in Germany, all 300tm cranes and above.
“This is the reason why Kranenbouw started a joint venture with Jost Cranes in 2006, assembling the JT 312.12 (300tm) and JT 352.12 (350tm) which we believe to be the best quality/price ratio tower cranes in the market.”
Lubbers agree: “These jobs call for cranes with capacities over 400tm: the Liebherr 420 ECH 16 or 20, 550 ECH 20, or 630 ECH 20, 25, 40 or 50. The model used depends on the distance the heavy elements will need to be lifted to. The Strijkijzer project just used one crane, but it was a small site: other sites may use multiple cranes. The building regulations in Holland allow you to fly over other sites, so there’s rarely a need for luffers, except where there are space restrictions.”
Jacco Veldhuizen, Van der Spek’s international rental and used tower crane sales manager, points out that the cranes for these don’t just need to be big, they need to be precise: “Positioning the elements needs to be very precise. This is where the Litronic system on Liebherr cranes is a big advantage. It has frequency control of the hoist, trolley and slewing, for easy, millimetre-precise, positioning. If the crew where the load is being delivered wants the load lifted or lowered by a millimetre, they can signal the operator, and he can do this easily.”
Hot iron
For the architect and contractor that Vander Spek worked with on the Strijkijzer, the benefits of the technology are clear. A P Bontebal, lead architect for the project at AAArchitecten, was trying to achieve something very special with the building, on a narrow, restricted site: “Architecture is always an adventure; you’re taught to think differently about traditional ways of building. This was the first time we’d worked on a building this high, and it was very well-received, both by the city and by our colleagues[the tower won the 2007 Emporis skyscraper award].
“The choice of building techniques has to do with the market. You have to consider the availability of suppliers, the qualities of the building, its height, and the time available for the job. This building, in our view, was made for pre-cast.
“The housing association, Vestia, had wanted a building that made a statement, and the city had planned a view of the city that made a disposition for this type of high rise building. We were looking to create a building that reacted to both daylight and night. At night, you just see the windows. In the day, the special shape reflects the light in different ways through the day: the building changes colour from pink, to blue, to black, to white. We were able to do that because of the shape of the building, and because of the cladding.
“I’m pleased with the unusual picture the building delivers. The black building, with its iron cladding, on a 33m x 33m ground plan, is remarkable. It fits the country it is in, and makes the public space more live able; it makes what was an undefined place more certain.
“It is important that it is not an office, but housing, that it is not a monoculture, but that it offers a range of facilities for the students, and public spaces like restaurants. The ground floor of a building should contribute to the public space. We did a lot to make it open and transparent. That was quite a job: on a building like this, the delivery of energy, of municipal facilities, of fire brigade access, all need to take up space. We were able to move these out of the way, and keep the front of the building.”
Although Bontebal’s vision for the building had been that it would be built in pre-cast, the original contractor had insisted that it would have to be built in poured concrete. Marcel Poolman, spokesman for Boele & van Eesteren, thecontractor who eventually built Het Strijkijzer, says, “The initial contractor had insisted that it could only be built with in situ pouring: they had refused to use pre-cast for a residential building over 75m. We had to demonstrate to the client that we could build this high in pre-cast; we really had to convince them.
“The original contractor had thought it was possible to use pre-cast at this height for an office, but not for a residential building. Residential buildings need to be a lot more rigid: if an office sways by a metre or so in the day, it doesn’t matter, you will barely notice it; if a residential building does the same, you will get seasick when you try to sleep in it.
The original contractor did not think you could get a building this high rigid enough in pre-cast.” The original contractor backed away from the project, before building started, giving pre-cast another chance. Poolman says, “Vestia gave us drawings for an in situ poured concrete structure, but said that, if we could find a faster way to do the job, we were free to offer alternatives. For every month earlier that the construction work was complete, they would subtract a certain amount of money from the price of the bid, to reflect the extra rent they would be able to earn.
“Wemade one bid for in situ construction working in single shifts, as the owner insisted on including that option. We offered three alternatives: in situ, working in double shifts, and pre-cast in both single and double shifts. The precast double shift option was 12months faster than the in situ single shift bid.”
WillemThoen, Boele & van Eesteren‘s project manager on Het Stijkizer, says, “The developer chose our pre-cast bid: it was a bit more expensive, but a lot faster.
“It was more expensive because of the market for pre-cast concrete. The costs depend on how many suppliers are available, and there are less suppliers of pre-cast than of in situ. The engineering can make pre-cast more expensive too. On a project like this, we had to reengineer the whole building. On in situ poured buildings, the forces can go every way through the building. On a pre-cast building, you have to work out how the forces will pass through each element and be transferred to the ground.
“It was quite unique to build a tower of this height in pre-cast. It takes a lot of engineering planning, which requires a lot of computer-aided design. Without modern computing power, you couldn’t engineer a building of this size in pre-cast. We’re lucky that one of our sister companies, through our parent Volker Wessels, is an engineering firm with a lot of experience with pre-cast structures.
“We’ve built four or five buildings this way, but this was the first of this height. We also recently built a pre-cast building in Rotterdam that was 110m high. Each building shape is different; we have to make sure that the engineering will work each time.
“As well as engineering the structure, the two biggest challenges were engineering the elements and the logistics of delivery. Het Strijkijzer is a very narrow building on a very tight site, so it would have been logical to have to think closely about the materials delivery schedule anyway.”
Poolman says, “We worked a six day week: we built one floor on Monday, Tuesday and Wednesday, then the next floor on Thursday, Friday and Saturday. On the first day of each floor—Monday and Thursday—the crane was lifting the floor elements; on the next two days, it was lifting the wall elements.”
Thoen adds, “The schedule was so tightly planned, if I looked out of my window and saw an element going up, I could tell which day and what time it was. “We were able to build two floors a week, taking about 80 deliveries a week. For many of the elements, we could only carry two elements per truck. Some elements needed to use special transport, so we could only deliver them before 6am. To attach some of the façade elements to the front of building, we had to stop the tram, so we couldn’t work on them in the rush hour between 7am and 9am.” Poolman says, “We only had to close—rather than stop—the trolley for a few night shifts. We had to build a steel shelter over the trolley line to protect it from small pieces falling from the site, which took five nights. When we installed the crown of the building, we had to lift some pieces that weighed as much as 25t. We had to strengthen and increase the power of the crane to do that, and had to close the trolley for another six nights while we worked. On the 26th floor of the façade, there is a 24t iron structure. That was welded on site, and then put up at night; again, the trolley had to be closed for that.
“When [local trolley operator] HTM closes the trolley, they only allow a tight schedule: the power goes off at 1am, and you can start work at 1.30. At 5.30, you have to stop; the power goes back on a 6am, and five minutes later the first trolley runs past the building. You only have five hours to complete the work.”
Most of the elements lifted in pre-cast construction are heavier, but they are also smaller. Thoen says, “One of the advantages of working with pre-cast is that you have fewer problems with wind and rain: you can always set the elements, whatever the weather. It’s a lot better for safety: because the elements are smaller and heavier they can be lifted very smoothly. When you pour concrete in situ, you have more iron, more air and electricity supplies, and more formworks that have to go up, so you have a lot more lifts. The weight and form of the pre-cast elements gives you much more control of the lift.
“It’s the best way to make a building of this height on such a small site. You have much more control of all the lifts.”
That consistency of work benefits the architects. Bontebal says, “With poured concrete, you need to use large formworks, and in a windy city like The Hague that adds risk. With pre-cast, you can use smaller elements, which are less likely to sway in the wind.
“We can make much more advanced details, working in pre-cast with millimetre precision, rather than to the centimetre. Pre-cast offers continuous quality, not just dependent on the weather conditions on the job site.”
Achieving millimetre precision takes planning. Thoen says, “Each element needed to be engineered to precisions of 10mm; the window frames and façade had even lower tolerance, of 5mm. The pre-cast supplier delivered great quality, and our engineering team did a very good job as well, so we had no problems. For a job like this, you need the right people doing the right tasks.”
Bontebal adds, “Using pre-cast elements saved us more than a year in construction time. We have to do a lot more in the office: we have to make all the drawings and decisions in advance. All of the insulation, the connections, need to be put into place in the element before it is positioned. But, time spent in the office is a lot more agreeable than time spent on site.”
Building in pre-cast doesn’t just make each lift safer and cut the number of lifts needed, it cuts risk across the job site. Poolman says, “When you work in precast, you only have five people working at the top of the building. When you pour in situ, you might need 30 people working on the top floor. That is something else that makes it a lot safer. You’re only ever working on one floor at a time when you work in pre-cast, rather than two or three floors at a time with in situ pouring.”