The Rise in ‘High-Rise’
India is urbanizing at unprecedented rates, setting forth a challenge unlike any other. India is faced with reducing in equality amongst its citizens, providing adequate housing solutions, reducing smog and other pollutants in its cities, and as well as, providing a sustainable urban transport network that can not only handle the existing overload but also provide for the future as well. To further put the challenge into perspective; approximately, every sixth person on Earth lives in India and nearly 40 percent of these people will or will have already moved to megacities in India, the UN estimates(1). Recognizing this, developers are increasingly looking at high-rise structures as means to accommodate the increasing population in cities. It is therefore, accurate to say, the increasing urbanization of economic clusters, across the major metros, is putting the rise in ‘high-rise’ construction in India.
Amongst the various solutions being looked at to address the above-mentioned challenges, especially providing adequate housing solutions, high-rise construction is one that is increasingly being employed. High-rise construction enables the use of the third dimension in space to increase the density of the population in a particular area. This solution is continually finding application across the major metros in India, as people continue to move to these economic clusters in search of jobs and opportunities, while the land available stays constant.
Across the eleven designated metropolitan areas in India(2); Bangalore, Chennai, Delhi, Hyderabad, Kolkata and Mumbai were considered for the purpose of this article. High-rise projects (above 100m), completed or that are under construction alone were considered to analyze and get a fair understanding of the growth of high-rise construction in India. The result of the analysis is seen in figure 1 below.
As it seen in the graph above, Mumbai has the most concentration of high-rise buildings in India. Incidentally, Mumbai is also the most populous city in India with a population density of approximately 73,000 per square mile(3). Further, Mumbai has a total of 78 high-rise buildings under construction and scheduled for completion between 2020 and 2022. This massive need and construction of high-rises in one of the world’s most densely populated cities, highlights high-rise as the solution that is being adopted to cater to the housing and infrastructure demand. It therefore, stands to reason, as population in other economic clusters in India increases, the skylines of these areas across India will increasingly get dotted with high-rising structures.
While high-rise construction stock throughout the country is on the rise, much more is needed, and as well as at a faster pace in order to be able to cater to the burgeoning demands of urbanization. It is estimated that there is already a shortage(4) of 18.78 million households for the EWS (Economically Weaker Sections) and LIG (Low Income Groups) which forms 95 percent(4) of the urban housing shortage in India. Data from Parliament, however, reveals “since the launch of the PMAY-U 1.26 million homes have been constructed(5).” Clearly, the rate of construction of high-rises across the country must pick up.
As high-rise construction stock gradually increases throughout the country, the technology used in its development, especially against the backdrop of environmental preservation, becomes of great significance. Presently, the construction of high-rises has seen the implementation and development of ground breaking technology that has enabled the development of structures exceeding the 800m mark height. However, unfortunately, many of these technologies are yet to foray into developing countries like India and problems like labour, low level of mechanization, long construction periods, high costs and environmental pollution deter the construction of such structures. In this article, we therefore look at the various technologies that are being implemented for high-rise construction in India and shed light on some advances in the field.
Technologies being Implemented
As established earlier in the article, there is a dire need for the faster output of ‘high-rise’ structures in India. Under this agenda, however, quality of the structure, impact on the environment and safety of the developers and occupants cannot be compromised. With these criteria in mind, the CPWD, a Principal Engineering Organization of the Government of India has approved 16 new and emerging technologies for inclusion in the construction of new projects(6). These technologies can be broadly classified into the following categories; monolithic construction, pre fab/precast RCC construction, LGFS construction, hybrid construction, pre-fabricated sandwich panel system, masonry with recycled waste technology, reinforced soil technology, high-performance concrete and energy efficient technologies. For the purpose of this article, we briefly take a look at some of these technologies being implement in high rise construction and the associated equipment for their implementation.
Monolithic Construction for High-Rise
Monolithic construction is a shuttering/ formwork dependent process. Typically, in monolithic construction, in-situ casting of slabs, beams and columns/walls is carried out in specialized shuttering/formwork after the reinforcement and service lines are placed. As a result, there is an upfront expenditure, in terms of procuring the required shuttering/formwork involved with monolithic construction. However, in the case of ‘high-rise’ structures, that have an increased number of repetitions, the initial costs are extended over a longer period of the construction, resulting in a faster and cheaper completion rates.
Apart from the traditional steel shuttering systems, monolithic casting of RCC walls, beams and slabs can also be achieved with tunnel formwork, aluminum formwork, jump formwork, plastic or plastic-aluminum formwork. While plastic, plastic-aluminum and formwork of other similar materials is cheaper to procure, they have a disadvantage when it comes to number of repetitions when compared to aluminum or tunnel formwork. As such, monolithic construction using aluminum and plastic-aluminum formwork was added to the list of approved technologies by the CPWD.
Various shuttering/formwork types for monolithic construction include:
Jump Form Shuttering
In this technique the central core is typically constructed ahead of the wings of the structure by using a climbing formwork system. The wings and the rest of the structure is then constructed around the central core. In jump form shuttering, typically, a steel frame is constructed over the central core. Steel formwork panels are then hung from this frame. After the concrete walls are poured, the formwork is released and rolled back from the concrete face. Jacks then lift or climb the whole frame up one level. Once the climbing formwork is in position, the formwork panels are closed and the next concrete wall is poured. The cycle times in such a process is dependent on the construction of the floor slabs, which is typically done as a separate process(7). Jump form shuttering, here taken to include systems often described as climbing form, is suitable for construction of multi-storey vertical concrete elements in high-rise structures, such as: shear walls, core walls, lift shafts, stair shafts and bridge pylons.
Aluminum formwork has only relatively recently begun to make strides in India but is, however, rapidly gaining in popularity. This is because Aluminum formwork panels can be designed for any condition/ component of buildings, and as well as for special architectural features including projections, cornices, planters, curved beams, etc. Additionally, this type of formwork is relatively easy to handle, and does not require the services of a crane for vertical or horizontal movement.
Further, inputs from industry suggests that the implementation of this system results in a monolithic structure that is strong, accurate and consists of high-quality finished surfaces. This system also tremendously improves the cycle time, resulting in enhanced cost effectiveness, especially when used with repetitions.
The tunnel formwork system is an innovative construction method that was invented only 50 years back, in Turkey for the construction of multi-unit residential apartments. This type of formwork system comes in half units in the form of an inverted “L”. When the two halfs are bolted together, they form a tunnel like structure, and hence the name. This type of formwork system is also fitted with hot air butane heaters which accelerates the setting of the concrete by maintaining a sufficiently high temperature. This facilitates single day cycles i.e., enabling the removal of the formwork within 24 hours.
The components of the tunnel formwork system include(8) (see Figure 2);
– The vertical, deck and back panel system to retain fresh concrete until it gets set and cured;
– A stripping platform, gable end platform and a working platform for movement, working and machinery handling;
– Push-pull props and wheeled props for tunnel line and level maintenance;
– Lifting triangle, placed at the formwork’s centre of gravity for lifting by tower crane;
– Kicker form provided at the slab level to maintain position of next level tunnel form;
– A slab stop end and a wall stop end to retain fresh concrete up to wall and slab line;
– Fixed block outs at vertical panels for door, window and ventilation installations in walls.
Apart from aluminum, jump form and tunnel formwork system, plastic and aluminum-plastic formworks can also be used for monolithic construction. However, in terms of economic value, reports suggest tunnel formwork to have the highest returns. It is estimated that tunnel formwork can be re used form about 500 to 1000 cycles. In comparison to aluminum formwork, it is seen that the reusability is somewhere in the range of 250 cycles.
Stay in Place (SIP) Formwork System
The Stay in place (SIP) formwork systems derives its name from its application methodology. As the name suggests, this formwork system is kept in place after the concrete is poured and set. Typically, SIP formwork is made on-site from prefabricated and fibre-reinforced plastic forms and this type of formwork is known to provide better environmental and corrosion resistance to the concrete.
Three main types of SIP formwork systems have been approved by the BMTPC for the construction of mid to the high-rise structures. They are:
1. Coffer system
2. Expanded polystyrene double wall system
3. Insulated concrete formwork (EPS interlocking blocks)
The SIP formwork system is said to have the potential to simplify and accelerate the construction process to a great extent. Apart from ease, it is also said to enable a higher speed of construction, improved site safety and reduced long-term maintenance in corrosive environments.
Prefabricated/Precast Construction in High-Rise
It is well established that the area available for construction is on a continuous decline. Land availability for projects, especially within urban centres in developing countries like in India, continues to be amongst the leading challenges resulting to delays in project completion. As a result, developers are increasingly looking at building leaner, taller structures in shorter periods of time. While the returns on investment on such a system is no doubt higher, these structures pose their own engineering challenges as developers look to maximize floor space within a much smaller time frame.
Prefabrication and precasting, along with modular construction are technologies that specifically address these challenges and enable the construction of taller and cheaper high-rises, within a shorter span of time. In fact, all over the world, volumetric prefabricated building construction is growing. For example, in Sweden the market share of prefabricated building systems in the housing industry is more than 80%(9). Precast and prefabrication in Denmark have become more and more viable in the last 60+ years as the preferred solution for buildings. Today, in Denmark, almost all residential and commercial buildings incorporate a very high percentage of precast technology.
Aarhus City Tower – A 100% Precast High-Rise
The Aarhus City Tower is a good example of precast construction where effective use of precast and offsite construction has generated a viable solution. The 93-meter mixed-use Aarhus City Tower contains 34,000 square meters of commercial and hotel space combined with a penthouse apartment at the top of the building. Aarhus City Tower is one of the highest fully precast structures in Denmark and challenges the height limit for precast structures using limited vertical connections across floors. The structural concept is a shear wall system utilizing the central core for stability combined with a double-tiered façade column for the vertical load. The hollow core deck slabs were designed for diaphragm action without the use of structural topping.
One of the key challenges in precast construction is the shear strength of the wall-to-wall connection. This is solved by an intelligent use of a combination of post-tension cables and non-tensioned reinforcement in corrugated pipes. The innovative precast sandwich façade solution combines precast concrete, beam action, insulation, colored concrete and sustainable photovoltaic panels all in one unit. This design approach required a strong focus on connections and reinforcement detailing. Extensive use of 3D-modelling of the precast elements as well as of the reinforcement elements was key in implementing effective solutions for this project(10).
In India, several technology providers are pioneering and promoting this technology. One of the largest projects currently underway in India to incorporate precast technology is the residential project by the City and Industrial Development Corporation of Maharashtra Ltd (CIDCO) which aims to construct 23,432 dwelling units at various locations in Navi Mumbai. L&T, the company that has bagged this project has confirmed that it would be using precast to complete this project as it was awarded based on stringent timelines.
Light Gauge Steel Frame Systems for High Rise Construction
Light gauge steel (LGS) frame construction systems are also known as CFS (Cold Formed Steel) constructions. In a day and age where sustainability and recyclability of building materials is increasing being brought under inspection, the LGS system offers an advantage. All LGS constructions can be disassembled after the building’s useful life and be reused orrecycled as all joists and material used are100% recyclable leaving no waste behind(11).
There are many successful cases where LGS systems were used for low-rise and mid-rise buildings up to 10floors as it was perceived that cold-formed steel (CFS) can only be used to frame buildings up to 10 stories. However, in April 2016, at an American Iron and Steel Institute meeting, Patrick Ford, P.E., principal at Matsen Ford Design in Waukesha, Wisconsin, and technical director at SFIAunveiled the SFIA Matsen Tower, a 40-story residence named after his late partner, John P. Matsen. At the event, Ford was quotted saying, “CFS’s gravity and lateral-resisting properties make it perfect as the load-bearing material for mid-rise structures. While 10 stories is the current perceived height limit for CFS C-studs and joists, the SFIA Matsen Tower proves otherwise(12).”
The materials used in structural framing for this project included lightweight EPDM on metal deck roof, lightweight 1-1/2” gypsum concrete on structural 0.6 C deck floor, lightweight exterior wall finishes of architectural metal, EIFS, or finished exterior cement board panels. Repetitive C studs and joists were provided for the primary gravity load-carrying frame. Wind force resistance for this project was provided by reinforced, cast-in-place concrete shear cores at the elevators and stairs(12).
High Performance Concrete (HPC) for High Rise Construction
In recent times, the use of admixtures in ready mix concrete has increased significantly. High performance concrete (HPC) is one of the many types of concrete that can be achieved through the use of admixtures, commonly by adding superplasticizers with high-strength mixtures. In the case of high rise construction, HPC offers not only structural but economic advantages as well. By using HPC, developers can reduce member sizes, reduce the overall weight of the structure, complete constructions faster due to HPC’s high early-age gain in strength, increase the length of the spans while reducing the number of beams, reduce axial shortening of compression supporting members, increase the long term service performance of the structure, decrease the amount of creep and shrinkage and reduce maintenance and repair costs(13).
Control flow Concrete for High Rise Construction
Control flow concrete is aninnovative and relatively new type of concrete that aims to merge the benefits of self-consolidating concrete (SCC) and conventional concrete by bridging the gap between them (see figure 4). SCC is a type of concrete that is made from conventional concrete materials and, in some cases, with a viscosity modifying admixture. SCC is highly flowable, non-segregating concrete that can spread into place, fill formwork, and encapsulate the reinforcement without any mechanical considerations. However, much like in the case with conventional concrete mix, SCC poses challenges and is difficult to produce.
As seen in figure 4, control flow concrete aims to merge the advantages of conventional concrete with the advantages of SCC. Therefore, control flow concrete is a segregation-resistant mix can have both high compressive strength and high passing ability, meaning it discharges quickly and can be placed more easily than conventional slump concrete. This new type of ready mix concrete provides architects more freedom in the design of complex structures, since the concrete can more easily flow into hard to reach areas and around complex support systems.
Infrastructure development drives our economy. In order to leverage the multitude of opportunities available in India, the speed, quality and durability of our structures must enhance. New and emerging technologies that enable faster, better and sustainable structures will find its way into India due to the large scale of requirements in the country. Presently, many of these technologies that enable faster, better and sustainable construction are still not implemented to their full potential. For instance, precast, modular and pre fabrication. These technologies have the potential to enhance the speed, quality and durability of our structures multi-fold. More efforts must be made to increase the market penetration of these technologies and make them common practice. Recently, IIT(M) conducted a round table discussion in an attempt to understand the challenges that face the widespread adoption of such technologies. Through such efforts, from all stakeholders of the industry, modern technologies can be incorporated across projects in India and enable the country to realize its potential.
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(2) List of Metropolitan Areas in India, Available at:https://en.wikipedia.org/wiki/List_of_metropolitan_areas_in_India
(3) Mumbai Population 2019, Available at: http://worldpopulationreview.com/world-cities/mumbai-population/#targetText=The%20population%20density%20of%20Mumbai,populated%20cities%20in%20the%20world.
(4)Report of the Technical Urban Group (TG-12) on Urban Housing Shortage 2012-17, Ministry of Housing and Urban Poverty Alleviation, September 2012
(5) Sneha Alexander, Vishnu Padmanabhan, Has NDA-II addressed India’s housing challenge?, Available at: https://www.livemint.com/industry/infrastructure/has-nda-ii-addressed-india-s-housing-challenge-1554057013108.html
(6) Dr KM Soni, Divakar Agarwal (2019) ‘New Construction Technologies Approved by CPWD’, in (ed.) Use of Innovative Technologies & Materials in Construction. : , pp. 13.
(7) The Jump Form System, Available at: http://www.cityu.edu.hk/CIVCAL/production/advanced/jump_form.html
(8) Mr. Manas A. Shalgar, Mr. Tejas D. Aradhye (2017) ‘Introduction to advanced TUNNEL Formwork system: Case study of ‘Rohan – Abhilasha”, International Research Journal of Engineering and Technology (IRJET), 04(03), pp. [Online]. Available at: https://www.irjet.net/archives/V4/i3/IRJET-V4I397.pdf
(9) Satheeskumar Navaratnam, Tuan Ngo, Tharaka Gunawardena and David Henderson (2019) Performance Review of Prefabricated Building Systems and Future Research in Australia, : MDPI.
(10) Tim Gudmand-Høyer () Aarhus City Tower – A 100% Precast High-Rise, Available
(11) AlhalabiZinah Shuman (2019) The Study of Light Gauge Steel for High-Rise Buildings and Business Centers, Availableat:https://www.researchgate.net/publication/330457917_THE_STUDY_OF_LIGHT_GAUGE_STEEL_FOR_HIGH-RISE_BUILDINGS_AND_BUSINESS_CENTERS
(12) (2019) How High Can You Construct a Building with Cold-Formed Steel Framing? The Answer May Surprise You, Available at: https://www.buildsteel.org/architect-profession/high-can-construct-building-cold-formed-steel-framing-answer-may-surprise/
(13) Gopal Mishra () Advantages of High Performance Concrete (HPC), Available at: https://theconstructor.org/concrete/advantages-of-high-performance-concrete/6097/
(14) The Rheology of Control Flow Concrete, Available at: