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Vertical development is the ideal solution to meet the demand of land for the fast growing urban population globally and in India. It is the construction of tall structures such as high-rise buildings, sky scrapers and sky towers etc., rather than constructing laterally to accommodate large population in quiet a lesser area. However the construction of high-rise buildings are highly complex and requires advanced construction techniques and equipment. One of the most important requirements is the advancement in forming technology. Though the conventional or traditional method of forming high-rise building is economical, it suffers seriously on the time, quality, safety and sustainability factors. Therefore, the advanced systems of formworks known as climbing formwork, slip-form formworks, Tunnel formworks etc. were introduced later.

Formwork is unquestionably important in any construction; its fundamental benefit is that it cannot be substituted by any other technology. Concrete structures can be built rapidly and at a low cost by employing formwork. A formwork provides suitable access and working platforms throughout the construction process, significantly improving worker’s safety, employees' safety & also scaffold safety.

By reducing the floor-to-floor building cycle time, formwork aids in the reduction of project timelines and costs, allowing more projects to meet their budgetary requirements. Formwork enables construction managers to provide precise on-time shuttering and de-shuttering of formwork resources, resulting in increased project efficiency and resource utilisation.

Climbing formwork

Climbing formwork, also known as jumpform, is a special type formwork for vertical concrete structures that rises with the building process. While relatively complicated and costly, it can be an effective solution for buildings that are either very repetitive in form (such as towers or skyscrapers) or that require a seamless wall structure (using gliding formwork, a special type of climbing formwork).

Best known in the construction of towers, high-rise buildings and other tall vertical structures, it allows the reuse of the same formwork over and over for identical (or very similar) sections / storeys further up the structure. It can also enable very large concrete structures to be constructed in one single pour (which may take days or weeks as the formwork rises with the process), thus creating seamless structures with enhanced strength and visual appearance, as well as reducing construction times and material costs (at the joints which would otherwise require extra reinforcement / connectors).

The climbing formwork structure normally does not only contain the formwork itself, but also usually provides working space / scaffolds for construction crews. It may also provide areas for machinery and screens for weather protection, up to being fully enclosed while yet staying modular around a changing building structure.

Various types of climbing formwork exist, which are either relocated from time to time (generally with crane), or can even move on their own (usually on hydraulic jacks, required for self-climbing and gliding formworks).

Crane-Climbing Formwork: in this type of climbing formwork, the formwork around the structure is displaced upwards with the help of one or more cranes once the hardening of the concrete has proceeded far enough. This may entail lifting the whole section, or be achieved segmentally.

Self-Climbing Formwork

In this type of formwork, the structure elevates itself with the help of mechanic leverage equipment (usually hydraulic). To do this, it is usually fixed to sacrificial cones or rails emplaced in the previously cast concrete. Self-climbing formwork is an automatic climbing system that is lifted without using a crane. Instead, it has hydraulic rams that lift the scaffold, formwork, and secondary formwork to the next pouring cycle. Since self-climbing formwork does not require any lifting equipment, it can significantly help reduce overall costs and labour. Another advantage is that it allows builders to continue their work even when it is very windy.

Gliding Formwork

This type of formwork is similar to the self-climbing type above. However, the climbing process is continuous instead of intermittent, and is usually only interrupted for a very short time (for example to fix the mounting mechanisms to new anchoring points). The advantage is that it will produce seamless structures, but it requires a continuous, uninterrupted process throughout, with serious potential quality and stability problems if the pour has to be stopped.

Slipform Formwork

Slipform construction technique has been gaining a lot of popularity over the years in the construction of high-rise buildings because of the many advantages it has to offer.

Slipform construction technique is normally adopted for the centrally located service core of a high-rise building. The service core or simply core of a high-rise building is normally located at the central portion of the building which hosts facilities not meant for dwelling or renting purposes but for common uses of all the occupants or users of the building and are integral parts of any such building. These include the elevator shafts, public restrooms or toilets, ventilation & electrical shafts, stairwells etc.

There are several reasons of slipform construction being economical for tall buildings or structures. The key reason is the repetitive nature of the method itself. Once installed, the formwork need not be dismantled and reinstalled again for further use. The same setting continues till the job, in this case the core structure of a high-rise, is complete. Even in the case of a very tall building where the core is sometimes reduced abruptly at certain elevations for various reasons, change in settings of the slipform structure need to be done only at those few particular elevations. This results in saving a great deal of time, manpower as well as materials and thus becomes more economic than conventional methods. The method of construction requires a much smaller group of highly skilled workers as compared to other usual methods including jump-form method. It also needs lesser quantity of forms.

The starter walls, meant for commencing installation of slipforms, must have all the necessary embedments/provisions including the jack-rods on which the entire slipform unit would climb up. The walls also must have all the vertical reinforcing steel bars with adequate projections.

This entire unit consisting of the slip-forms, cross-beams, platforms etc. are raised in synchronisation along the jack rods by means of hydraulic jacks of suitable capacities. The jack rods, which are usually embedded in the concrete walls of the core itself, can be either sacrificed or removed later on if so planned.

Besides fixing re-bars, these platforms are also used for fixing doors and window frames, inserts/embedments, keeping provisions for supports and other openings and so on.

Lowermost platform is used mostly for quality related purposes such as monitoring concrete quality, continuous surface finishing of freshly stripped concrete surfaces, curing, rectification of shortcomings, if any, and so on.

The rate of lifting of forms primarily depends upon the rate of setting of the poured concrete. The lowermost portion of the poured concrete inside the slipform must set sufficiently in order to gain enough strength to support itself as well as the layers above it (upto the top of forms) without getting deformed/damaged while the forms are slipped up. At the same time, it should not set too hard and thus resulting in excessive friction between the forms and the concrete surface. That could lead to difficulties in lifting the forms which in turn could damage the still-fresh surface of the concrete as well.

Tunnel Formwork

Tunnel form is a formwork system that allows the contractor to build monolithic walls and slabs in one operation on a daily cycle. It combines the speed, quality and accuracy of factory/offsite produced ready-mix concrete and formwork with the flexibility and economy of cast in-situ construction. Tunnel formwork system is one type of construction techniques used for multi storied building construction to reduce cycle time. Its usefulness also stems from the fact that no starter concrete is required for walls; it allows easy alignment and de-shuttering, hot air curing to enable early stripping and favours a standardized working sequence to improve labour productivity.

A recent trend in the building industry in India, as well as in many countries with increasing city populations, is toward utilizing the tunnel-form (shear wall) construction system for development of multi-storey residential units. This has been driven basically by the need to construct earthquake resistant multi-storey reinforced concrete (RC) buildings with considerable ease, speed and economy. The tunnel-form system is an industrialized construction technique in which structural walls and slabs are cast (in situ) simultaneously using steel forms composed of vertical and horizontal panels set at right angles. To expedite the construction, non-structural components such as facade walls, stairs and chimneys are commonly produced as prefabricated elements. Tunnel-form buildings generally have a symmetrical configuration in horizontal and vertical planes that enables continuous flow of construction and better quality assurance. Besides the constructive advantages, tunnel-form buildings provide superior seismic performance compared to conventional RC frame and dual systems, which suffered significant damage and total collapse in many regions during devastating earthquakes in India.