Shriyal Sethumadhavan examines the technique behind the construction of tall buildings and whether India is ready for these.
´I am the power that lifts the world´s head proudly skywards, surpassing limits and expectationsà I am Burj Khalifa.´ These lines are ingrained at the entrance of the world´s tallest building that stands at 828 m with over 160 storeys in Dubai. The pride is, indeed, justified.
The construction called for 330,000 cu m of concrete and 39,000 tonne of steel rebar, it would have taken 22 million man-hours. And from the tallest to the best û this year, China´s twisting CCTV Headquarters, designed by Rem Koolhas, was named the best tallest building worldwide by the Council on Tall Buildings and Urban Habitat (CTBUH). Let´s look at the Indian context now. ´Every building taller than 70 m is considered a tall or high-rise building,´ says Ramesh Nair, COO Business, Jones Lang LaSalle India, sharing the Brihanmumbai Municipal Corporation (BMC) definition of a tall building. In his view, the top three cities where the concept of tall buildings is growing are Mumbai, Bengaluru and Delhi. In fact, the top 10 tallest (completed and under-construction buildings) in India are located in Mumbai. He adds, ´Mumbai needs to focus on vertical development because the city´s population is around 20 million and its area only 470 sq km.´ Antony Wood, Executive Director, CTBUH, echoes this perspective when he says, ´While 2 per cent of the earth´s surface is occupied by cities, 53 per cent of the world´s population lives in these cities.´
Advances and trends
International architectural firms are now joining hands with Indian developers to create tall buildings. ´We have started signing JVs with companies based in Dubai, Australia, Canada and Malaysia,´ reveals Sanjeev Kumar Jha, Assistant General Manager, Raheja Developers. ´One such company is Dubai-based Arabtech. The idea is to bring their exposure of building tall structures into India.´ And Nair informs us, ´Innovative structural systems involving tubes, mega frames, core-and-outrigger systems, artificially damped structures and mixed steel-concrete systems are some new developments.´
As of now, concrete seems to be scoring over steel. ´We can reasonably conclude that residential towers made of concrete are the predominant trend in India.´ says Daniel Safarik, Editor, CTBUH. ´The strength of concrete has improved substantially over the past decade, making taller, thinner, lighter structures possible, using less material.´
´Tall buildings are currently being built with high-performance concrete (HPC) as this is preferred from the durability, aging and fire-fighting point of view,´ affirms Mayur Shah, Managing Director, Marathon Realty. ´Also, companies like Putzmeister and Schwing Stetter provide high-powered pumps where you can actually pump concrete up to 40 to 60 floors.´ Alpa Sheth, Managing Director, VMS Consultants, seconds this. Despite experiments in tall steel buildings, she says, ´Concrete structures still rule the roost for super tall buildings owing to their inherent stiffness. These increasingly feature an outer perimeter of concrete peripheral walls to eliminate plastering and other external treatments.´´
At the construction level, modular and lightweight aluminium shuttering has changed the way tall buildings are conceived. ´While we use aluminium shuttering for residential buildings, Peri table formwork is used for commercial high-rise buildings,´ says Shah. He points out that the floor-to-floor cycle takes six days with aluminium shuttering technology, while it takes 21-28 days with the conventional technology. Also, with jump-form technology, you can have the lift shaft, staircase and other services moving ahead of the floor cycle. ´We are constructing a 52-storey building with the use of HPC, aluminium shuttering, RMC plant, tower crane and jump form,´ adds Shah. For his part, Jha says, ´From the standard beam, columns, slabs and brickwork, we are now opting for precast panels, precast slabs and post-tensioning slabs; the use of precast reduces construction time by around 50 per cent.´´
Quite naturally, vertical transportation has evolved in tandem with the demand for tall buildings. Finnish elevator manufacturer KONE has unveiled a new hoisting technology that will enable elevators to travel heights of 1 km - twice the distance than currently possible. ´This implies that the Burj Khalifa, whose longest elevator travels a distance of 504 m, will not remain the world´s tallest building for very long,´ observes Nair. Indian company, Marathon Realty, sources elevators of 4 m per second for its projects from a Korean company.
In the upcoming Marathon Futurex, elevators have been installed to cover each floor within a second; so, 40 seconds for 40 floors. The fastest elevator in the world, made by Toshiba, takes passengers from ground to roof in 30 seconds, rising 33.7 m per hour through the Taipei 101. ´This surpasses the speed of the Burj Khalifa´s Otis elevator, which travels at a mere 22 m per hour,´ Nair adds.
Bringing international expertise to India is Jeremy Lester, Chief Executive, Grocon International, who is executing projects for Lodha Group and Omkar Realtors. He perceives distance control as a key development in high-speed elevators. ôYou can cross a lift that services a different floor level and then get into another high-speed lift for your specific destination,´ he says.
Wind tunnel testing
Determining wind loads on cladding and fixtures is a crucial aspect of tall building design. An increasing number of buildings are being tested in wind tunnels internationally and in some national laboratories. ´For Marathon Futurex, we are using complete fatade work from outside that is being designed to withstand winds of 200 km per hour,´ shares Shah. ´However, as wind tunnel testing of a facade is not available in India, this has been done in Singapore.´ ´A Y-shaped building can reduce wind forces to a great extent,´ explains Jayprakash Rao, Director- Corporate Marketing Strategy, Shapoorji Pallonji Construction. ôWind force analysis needs to be carried out. Shape of the building greatly influence in reducing the wind forces and thereby achieving the value engineering in design of structure. While the Y-shape has been used in the construction of Burj Khalifa, in the UK, dampers are provided in high rise buildings, which is another innovative approach to let wind pass through and reduce the pressure.´
Meanwhile, Sheth says, ´There is awareness that the prescriptive wind code may not be able to adequately predict wind behaviour on buildings. Local labs will need to come up to speed if they would like a larger piece of the pie in terms of wind tunnel testing projects.´
Testing aside, do Indian building codes address the question of tall buildings? ôPresent Indian codes are not suited to tall buildings,´ responds Sheth. ôThere is a new tall buildings code under preparation. I happen to be the convenor of the sectional committee for the code.´ And while Rao agrees that the codes need an upgrade, Jha says,´As tall buildings over 50 and 60 storeys are still relatively new developments, the codes fall short but we hope the situation changes in the next three to five years.´ Lester too believes the future bodes well with ôIndia witnessing a consistent adoption of international best standards of safety and quality´. However, he points out that the implementation of codes and standards depends on all of the stakeholders the developer, investor, builder and regulator to ensure consistency across the industry.
Additionally, Sheth points out that most architects are not conversant with the special needs of tall buildings. ôIt is important to communicate special issues involved in the design of tall buildings and the governing parameters for an optimised structure,´ she says.
In Jha´s view, the challenge lies in adaptation of technology. For real-estate consultant Nair, one of the biggest limitations in the construction of tall buildings is the highly limited FSI. As he points out, ´The Ministry of Environment is proposing that the height of the building should be related to the width of the road on which it is constructed. For instance, a 60 m building should have an appurtenant road with a width of at least 30 m to help reduce congestion in the city.´ However, he emphasises that there is no one-size-fits-all method. Hence, the decision on how tall a building should be constructed must be left to local authorities who are more aware of the city´s problems.
´My understanding is that the main limiting factor of tall building construction in India is fundamentally poor infrastructure, particularly in overcrowded places like Mumbai,´ reasons Safarik. ôWhile many buildings are under construction, their quality will not achieve international standards until the infrastructure in their immediate surroundings improves.´
No talk of construction would be complete without an analysis of the costs. ´As tall projects are generally high-end projects with higher specifications, the cost of construction for the developer is around Rs 3,800 to 4,200 per sq ft,´ explains Jha. As for Shah, he says, ´Technically, we go around Rs 6,500 per sq ft for commercial buildings; for residential, this may increase. Structure cost is typically around Rs 3,000 per sq ft. Parking also contributes to the total cost.´
´One best practice to control cost is to maintain the timeline as we have seen an over 200 per cent rise in building material prices in the past four years,´ adds Jha. ´For instance, today, we procure steel at Rs 40,000 a tonne and cement at Rs 220 a bag. After three to four years, steel per tonne could cost around Rs 60,000.´
So, going forward, how ready is India to travel upward, literally, with its buildings?
For her part, Sheth is unsure whether super tall buildings are the way to go for India. ´They´re appropriate for dense cities like Mumbai but not in B cities where space may still not be a critical issue,´ she reasons. ´Both initial investment, services and long-term maintenance costs are higher. At present, I would say we have rushed in where angels fear to tread. We need to be more judicious about where to build buildings greater than 25 to 30 storeys. We begin to stumble beyond this height. Also, the quality control mechanisms, inspection and testing regimen that should precede such construction are still lacking.´ Meanwhile, Nair sees it differently. ´Apart from the fact that vertical development is the only option for land-constrained cities, changing lifestyles owing to rapid urbanisation also add an aspirational value to skyscrapers. Hence, I see the market growing very rapidly. In terms of technology, India might not be fully equipped to execute the construction of tall buildings at a rapid pace. But we sure are getting there.´ Lester endorses this by calling tall buildings a ´highly relevant solution´ for India.
Indeed, the future can be both tall and lofty, according to Wood from CTBUH, who shares a new vernacular for the skyscraper. He says, future tall buildings should relate to the physical, environmental and cultural characteristics of place; vary with height in form, texture and scale; accommodate new and multiple functions; provide significant communal, open, recreational space; maximise layers of usage on all systems and materials; introduce more facade opacity (and variation or texture) in skin or envelope; embrace organic vegetation; and introduce physical, circulatory and programmatic connections, such as sky bridges.´
A tall order? Let´s wait and watch.
Completion: November, 2010 (A&B Wing),
March, 2012 (C Wing),
Height: 198 m ,
No. of floors: 48 (1 basement + 2 podiums + ,
GF + SF + 48 upper storey + terrace),
Highlights: This 648-ft tall residential tower is located amid large pristine landscaped terrain in Mumbai with a gently contoured sea-wave inspired fatade; a wave-like roof element makes for a stunning elevation.
Vertical transport: Mitsubishi elevators (four per wing); speed: 4 m per second Materials: A normal RCC framed structure building, the roof crown is in structural steel (hot deep galvanised) and clad with aluminium composite panel (ACP) at top. The fatade is designed for high wind pressure above 2.5 Kpa for windows. It features a laminated glass railing and sky gardens with a vertical green wall. Refuge areas are enclosed with up to two hours fire-resistant rated glass.
Technologies: MIVAN shuttering for formwork renders homogenous construction of the floor without joints and superior finish of formwork. In addition, the slab cycle has reduced from 15 days to seven to nine days.
USP: Bellissimo C features nine duplex penthouses, each with its own private swimming pool and jacuzzi. The building also has an on-site concierge, ´Quintessentially´. The property features Club B, a 20,000-sq-ft clubhouse spread over three levels designed by renowned architect Geoffrey Bawa. Further, the 8,000-sq-ft luxurious spa by L'Occitaine, Spa la Vie, was for the first time in Mumbai here.
Completion: March 2012
Height: 175 m
No. of floors: Basement + Ground + 40 floors
Vertical transport: High-speed elevators from OTIS
Highlights: This commercial tower offers a very clean floor plate without any columns and beams in between. Commanding a 270¦ view of the city and the Arabian Sea, the tower comprises a basement, entrance lobby at ground floor, upper parking floors (floors 1-5) and 35 upper office floors (floors 6-40).
Materials: This is a composite structure with service core in RCC and office space in structural steel. The office space has structural steel columns only on the periphery. The structure also has braces bolted to the columns and beams visible in the office dTcor. It also has cladding in structural glazing and ACP. Aluminium extrusions are used to reflect structural braces that are a vital part of elevations and the ´crown´ as a feature element to enhance the glory of the tower that lights up the sky at night.
Technologies: Vermiculate plaster is used for the steelwork above the false ceiling. The service core area is carried out using Mivan shuttering, which offers fine quality and fast working speed with great convenience. This has been procured from China and Turkey.
USP: Distinction of being India´s tallest structural steel building.
Mantri Pinnacle Completion: 2014
Height: 153 m
No. of floors: 2B+G+45
Highlights: Excellent facilities including high-end mini theatre and designer pool with aqua gym; smart digital homes powered by Cisco; VRV (variable refrigerant volume) air-conditioned; sky lounge-cum-coffee shop on 41st floor; observatory on 42nd floor; high-speed biometric elevators; incorporates Gold standard green building features; GEBRIT solvent plumbing single-stack system.
Vertical transport: No. of lifts - 4; passenger lifts - 3; capacity - 900 kg; speed - 2.5 m per second; service lift - 1; capacity -1,020 kg; speed - 2.5 m per second.
Materials: Aerocon blocks, an eco-friendly and lightweight material; chemical adhesive for block work construction instead of cement mortar; GI lintel instead of RCC lintels to expedite progress; sustainable approaches: fly ash and GGBS used to minimise the cement content and reduce usage of virgin material.
Technologies: Snehal Mantri, Director-Marketing and HR, Mantri Developers, says, ôFlat slab design has been done for all typical floors entertaining the use of table formwork for construction. No beams in typical floor dwelling units to achieve faster progress and slab cycles. ACS PERI formwork has been used for core wall construction (faster progress, better finish of RCC and verticality maintained). DGUs are being used for building fatade works meeting IGBC requirements, reducing indoor temperature. Scissor staircase has been designed as per fire norms.´
Challenges: Adopting innovative and cost-effective technology; identifying and selecting competent consultants with high-rise expertise; construction of architectural features at 40th floor level; transverse slab designed at penthouse level and executing the same with formwork; cost-effective construction methods keeping tab on time, quality and safety; timely completion of project from concept design to handing over; construction of three-floor-height flower bed on the periphery of the building.
USP: Southern India´s tallest residential tower with double-glazing features.
CCTV Television Station And Headquarters, Beijing
Completion: 2012 Budget: 5 billion RMB
Site: 20 hectare in new Central Business District
Facilities: Program total - 599.548 sq m; CCTV total - 473.000 sq m; administration - 64.200 sq m; multipurpose - 54.900 sq m; news production - 65.800 sq m; broadcasting - 31.800 sq m; program production - 105.400 sq m; staff facilities - 30.000 sq m; parking - 61.500 sq m; service building - 15.000 sq m
Highlights: Two towers rise from a common production studio platform, the Plinth; Tower 1 serves as editing area and offices and the lower Tower 2 is dedicated to news broadcasting. They are joined by a cantilevering bridge for administration, the Overhang. Instead of competing in the race for ultimate height and style within a traditional two-dimensional tower ´soaring´ skyward, CCTV´s loop poses a three-dimensional experience, culminating in a 75-m cantilever. Visible from most of Beijing, it sometimes comes across as big and sometimes small, from some angles strong and from others soft.
Design features: The self-supporting hybrid facade structure features high-performance glass panels with a sun shading of 70 per cent open ceramic frit, creating the soft silver-grey colour that gives the building a surprisingly subtle presence in the Beijing skyline. The forces at work within the structure are rendered visible on the fatade: a web of triangulated steel tubes ´ diagrids ´ that, instead of forming a regular pattern of diamonds, become dense in areas of greater stress, looser and more open in areas requiring less support. The fatade itself becomes a visual manifestation of the building´s structure.