With the rising of populations, changing lifestyles and environmental issues, the adequacy of Europe鈥檚 ageing infrastructure has long been a concern.

The barrel shutter in place inside the King George鈥檚 Park shaft to form the connection tunnel. (Photo: Kwikform)

The good news is that recent years have seen both state and private construction spending on public buildings and infrastructure rise, and this investment now being further increased to combat the economic downturn brought on by the pandemic.

Formwork for older substructures

And while this means that many new structures are being built to replace outdated ones, existing older structures are also being updated, augmented or scaled back. And for those involved, these types of projects present complex challenges.

A case in point is RMD Kiwkform鈥檚 recent work on the new Thames Tideway Tunnel currently being built in London, UK, by contractors Bam Nuttall, Morgan Sindall and Balfour Beatty (BMB).

Known as the city鈥檚 鈥渟uper sewer鈥�, the 25km long tunnel is an upgrade to the city鈥檚 Victorian sewer system. It is designed to capture, store and then divert 鈥渕ore than 95% of the sewage spills鈥� away from the river Thames.

Kwikform鈥檚 scope of works covered the project鈥檚 Dormay Street and King George鈥檚 Park shafts in West London, for which the company had to ensure that their systems would enable construction and demolition works to be carried out within the shafts at the same time, to keep the project schedule on track.

Kwikform provided temporary systems for forming concrete elements on all aspects of the shafts - including shaft linings built via slipform construction, as well as formwork for the surface and internal shaft structures鈥�.

In particular, the vertical drop pipes that intercept existing spillways into the Thames and transport the discharge down the drop shafts to the newly constructed tunnels.

Amy Hogg, BMB site agent for Dormay Street and King George鈥檚 Park, explains, 鈥淭he biggest challenge was installing the vortex drop tubes 鈥� these huge stainless-steel tubes fill approximately two-thirds of the shaft.鈥�

Horizontal soldier props stabilise the encasement shutter at King George鈥檚 Park. (Photo: Kwikform)

鈥淏uilding the temporary works that would support the weight of these tubes and keep them in position, as well as enabling the build of all the structures around it, was quite a complicated process.鈥�

To install the drop pipes BMB鈥檚 team had to break out the sewer鈥檚 vortex safety grill chamber, which controls the flow of sewage and wastewater into the tunnel. Five separate levels of concrete had to be cut and removed from the shaft, while avoiding nearby ground shoring props.

To accommodate the project鈥檚 complex geometry and construction works, Kwikform provided its Alshor, Rapidshor and Megashor falsework systems, and its Superslim Soldier primary formwork beams, aluminium beams, heavy-duty Maxima wall formwork panels, and Trapeze panels for curved wall formwork.

鈥淎 support grid of Soldiers was assembled using six-way connectors, with Alform beam decks at each of the five levels needed for the breaker and saw to operate,鈥� the company explains.

鈥淭he inherent strength of the Soldier structure then provided a strong anchor point for the removal of the sawn concrete blocks, allowing every single process to take place on a single deck.

鈥淲hen the cutting and removal was completed at the top level, that Soldier deck was unbolted from the main Soldier grid, leaving a new deck at exactly the right level below. This was the case for each of the five levels. As a result, the breakout could immediately continue, saving a full day鈥檚 labour at each level.鈥�

What are the key challenges of bridge construction?

While expanding existing substructures such as this present significant support challenges, so to does the construction of new bridges.

Currently under construction in western Poland, Expressway S3 runs for a total of 480km from the port of 艢winouj艣cie to the Czech Republic boarder in the south.

P茅cs market hall occupies a 1,750m虏 footprint. (Photo: Meva)

Formwork specialist Peri was contracted to provide support for the 75km-long section of the roadway running between Legnica and Lubawka, comprising three bridges with two superstructures each.

鈥淎 major challenge in the project was the planning and implementation of various structures and bridge girders with high demands on the quality of the concrete surface,鈥� explains Peri.

鈥淭he bridges differ in their length between 435m and 589m and in their radius, meaning that the concreting work was carried out in different numbers of concreting sections spanning 25m each.鈥�

Known as WS49, WS52 and WS54, the bridges were built using a 鈥渃oordinated formwork and scaffold solution鈥� using the company鈥檚 VARIOKIT Incremental Launching Facility, VARIO GT 24 and TRIO Column Formwork systems, as well as the PERI UP Scaffolding System.

The Variokit formwork system was used for the abutments, high bridge piers, and for the construction of the incremental launching basement, as well as the external, internal and slab formwork for the superstructures.

The system鈥檚 units feature a striking mechanism that pushes the external formwork outwards in a horizontal direction, when the incremental launching basement is lowered.

鈥淭his provided the necessary distance between the hardened structure and the struck formwork when moving the superstructure, which is necessary for narrower bridge radii,鈥� the company explains.

鈥淲hen the incremental launching basement was raised, the mechanism automatically pulled the external formwork back into the concreting position. This meant that no additional alignment of the external formwork was necessary and the site personnel could start directly with the next work steps.鈥�

When it came to slab formwork in the trough, the construction team used Peri鈥檚 VIL Wall Support with Roller Drophead, which was used to implement the movable slab formwork system via an additional quick striking mechanism.

Peri says, 鈥渢he shuttering method of the VIL System allowed the slab formwork to be moved independently into the concreting position by means of pulling鈥�, allowing the 25m-long slab formwork to be 鈥減ulled into the new cycle and aligned within half an hour鈥�. This allowed the bridges鈥� contractors to keep to the works on schedule.

Bespoke formwork system

Unlike Kwikform鈥檚 underground works on the sewer and Peri鈥檚 bridge contract, the construction of a new market hall in the Hungarian city of P茅cs required an altogether different approach.

Germany-based formwork specialist Meva was contracted to the P茅cs market hall project by main contractor B. Build & Trade.

Featuring a mix of modern and classical architecture, the design of the structure incorporated curved openings and long sequences of arches to maximise light.

Mammut 350 elements and steel lattice vaults, which give the arcades their shape, lie on the MEP shoring and H20 girders. (Photo: Peri)

鈥淚t comprises two series of 11 smaller arches, each with a clear width of 8.10m, on the longitudinal fronts,鈥� explains Meva.

鈥淪tanding perpendicular to these are two external and 12 internal arches which are even bigger, with a clear span of 13.6m, and lend the interior an airy feel.鈥�

Meva provided its Mammut 350 wall formwork system, its modular MEP shoring tower and Triplex heavy-duty bracing system for the construction project.

For the market hall鈥檚 curved openings, the company used two custom-made semi-circular steel-mesh brackets, measuring 13.6m and 8.1m wide respectively.

The brackets were placed between the top edges of the precast concrete piers and supported by the MEP shoring towers at a height of 4m.

The company then mounted its high-performance Mammut 350 formwork panels on and over the steel-mesh brackets. The symmetrical tie hole feature and the formwork panels鈥� joint pattern of the Mammut 350, which enables the panels to be used horizontally or vertically, meant that B. Build could ensure the concrete surfaces met market hall鈥檚 鈥渁esthetic criteria鈥�.

Stabilised by the Triplex braces, Meva鈥檚 modular MEP shoring tower carried the weight of the steel-mesh brackets, formwork and concreted walls, which together stood 13m tall.