Falsework & Formwork: Bespoke solutions
By Sandy Guthrie21 November 2011
The falsework and formwork sectors are as affected by the global financial situation as any other part of the construction industry, and there is concern in many parts of Europe over how public spending cuts will hit the market.
At Harsco Infrastructure, marketing director Babette Bargatzky said, "There is still uncertainty because of the debt crisis, and public spending is difficult."
She said there were many projects lined up in Europe for the future, "in Germany, the Czech Republic and Hungary, while Poland is a good market - but the question is when will public sector spending end? Generally, I would say I am slightly optimistic about the future."
She added that she had seen a trend towards rental in some markets, and there has been pressure on prices. In Germany and Austria, she said there had been relatively restricted market growth.
Harsco has a range of wall formwork, slab falsework, shoring, climbing and bridge construction equipment. It has been involved in a number of high-profile projects recently - for example its self-climbing formwork on the world's longest cable-stayed bridge, the Russky Island Bridge in Vladivostock, Russia - and for many of these, the key has been to find solutions to particular problems, and to make those solutions attractive to the customer.
Ms Bargatzky said, "In western Europe, the focus is on labour-saving solutions, for example larger panels and just-in-time delivery."
There is always a need to keep moving forward, and product development is as important as it has ever been.
Ms Bargatzky said that one area that had been worked on was a result of concrete pressures. "Because there is a need to pour faster, the formwork needs to be more rigid."
Among the projects that Harsco has been involved in recently is a project to create a new, 1,500-seat theatre building on a site with a restricted footprint and limited access.
Harsco was able to design and construct a bespoke support girder system which overcame the restrictions of the site and allowed the construction of a number of key structural elements of the new building.
The new theatre, in Bordeaux, France, is being built on a site surrounded by existing buildings. Harsco was asked to provide a support system to carry formwork for the construction of a number of 1.8m wide, 2.1m high, 32m long in-situ concrete beams. These beams needed to span the stage area and also support a further five floors of apartments and office accommodation being built above.
The girder systems supplied by Harsco varied in length - the longest being 30.9m - and needed to be lowered, relocated, and in some cases altered in length before work on the next beam could begin.
Flexible and reliable
Working on behalf of Portuguese contractor Buildin, Harsco said it was able to devise a bespoke H33 braced truss-girder system which was sufficiently flexible and reliable to do the job.
Harsco added that this proved to be a faster, more cost-effective and practical solution than other alternatives. However, a severe lack of working space on the site meant that Harsco also had to adapt the traditional methods used to construct such a system.
Harsco's Ingo Schnelting said, "We actually did much of the construction work on the girders about 10km away from the site itself. This meant that we could prefabricate the girder sections under more controlled conditions, which made it far easier to ensure that they complied fully with the drawings."
Harsco was then able partially to dismantle the girders for transportation and deliver them to site. Lack of on-site storage space meant that Harsco had to adopt a just-in-time schedule for these deliveries.
"We had to remain flexible in our approach to every aspect of this project," said Mr Schnelting. "The different lengths of concrete beam that the building required meant that we sometimes had to remove the girders from the building and transport them the 10km back to the construction area. There we were then able to re-configure their length before delivering them back to site and using hydraulic jacks to raise them into place, ready to support the formwork required to make the next beam."
Meanwhile, a new publication from Harsco Infrastructure has been designed to help construction industry professionals re-appraise their safety procedures for operations which involve working at height.
The new Harsco Infrastructure Guide to Working at Height is intended for use by client and contractor staff at all levels.
For Meva, the German-based family-run formwork company, its aim is to be a one-stop shop formwork supplier, providing a complete solution.
It was the company's founder, Gerhardt Dingler, who looked to standardise formwork. He founded the company in 1970 and claims to have been the first to introduce standard formwork in different sizes. Before that, everything was built specifically for a job.
Until 2000, Meva used heavy steel facings or plywood. Increasingly, Meva introduced plastic, which it said had the advantages of plywood in that it could be nailed into, while it didn't shrink or stain.
Since 2004, Meva has not used plywood, unless specifically requested by a customer. It uses a plastic material called alkus. It claims that it has unlimited re-uses and is 100% recyclable. It also says it can be cleaned on site with a high-pressure washer, damage can be repaired on site, and it can be welded to create large forming sheets. Crucially, it can be shaped and bent. It has a seven-year warranty which Meva said had never yet been claimed.
In a recent project, Meva was set a task with a number of criteria which it felt would suit alkus. A new bus terminal in the town of Merseburg in eastern Germany, required a flat roof standing on steel columns 5.88m high to protect a traffic and passenger island 86m long and 13m wide from rain and snow.
The architects designed the roof in concrete and shaped like an M for Merseburg. Glass and steel elements complete the structure. The concrete roof was designed in architectural concrete to remain exposed as poured, with a seamless and jointless white concrete finish. No touching-up or remedial work was allowed.
Discolouration was not acceptable, nor was any prior treatment of the facing surface. There could be no rust or dirt marks and stains. The surface had to be absolutely even.
The very particular specification also demanded that there should be no drill holes, no nail or screw holes, no shrinking or swelling, no scratches and no cement haze.
Any wooden facing - irrespective of type, grade or coating - was excluded on technical grounds. According to Meva, only alkus could be welded and fulfilled the requirements without any restrictions.
It said the facing could be fully welded on all sides, stripped after the pour and - importantly for economic reasons - would be re-used as facing sheet afterwards.
First, the geometry of the roof was optimised to correlate with standard alkus sheet formats. The sheets were cut to size and transported to the site, where they were placed on the support grid and aligned in rows with a continuous 2mm gap between each panel.
Each panel was fixed to a screw bracket attached to the cross beam. Inserting the screw from behind prevented any surface damage or bulging on the facing which would have made welding the panels together difficult, said Meva.
A mobile 6m tent was set up to enable welding work to be done in any weather. A custom-made holding apparatus helped handle the welding gun smoothly along 900m of running joints.
In order to achieve an evenly-coloured finish, the entire forming surface including the edge sheet was smoothed with a rotation cleaner and special pads. Test pours showed that the best results were achieved when using no release agent, so site management decided to do without a release agent altogether.
The formwork for pouring the 36cm edge of the roof was pre-assembled by joining 2m alkus sheets to form 8m to 10m long strips which were then set up against wooden brackets and screwed to them from behind.
After rebar work was completed, the entire forming area was flooded to remove any residues of dust, flying rust and other dirt. The flooding also provided a thermal cushion that prevented the sheet and joints from cracking below 0°C, which is not unusual during the winter months.
Meva said this procedure would not have been possible with any other forming material. The actual concrete pour was done in a single cycle after the water had been siphoned off and the forming surface cleaned with a high-pressure washer. In addition, the surface was kept clean by vacuuming it constantly.
After the concrete works were completed, the all-plastic facing sheet was cut into small transportable sheets. The screw holes were repaired and smoothed down before the sheets were fitted into standard formwork panels.
Meva said recycling the forming sheet made the use of the alkus sheet economically feasible.
Cantilevers without support
Austrian-based Doka has come up with what it describes as an efficient way of forming cantilevers without ground support - ParaTop.
It said the crucial advantage of this ingenious system solution was that all the worksteps - reinforcing, forming and pouring - were carried out from the bridge superstructure.
It claimed there was no need for any extra working platforms, saving time and cutting costs. It added that the large influence widths of the brackets reduced the amount of equipment needed, and speed up the workflow.
The company said, "Because the formwork is so quick and easy to hang into place, less crane-time is needed and assembly operations on the bridge deck are made very much easier."
Doka's ParaTop is already doing being used on worksites in Ireland, the UK and Poland, as well as South Africa and Panama.ce