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Construction : Cover Story | August 2016 | Source : CW-India

India’s Tall buildings | High on technologies and systems

With Indian cities witnessing a surge of high-rise developments, CW PROPERTY TODAY features technologies and systems that are essential to build tall.
According to the Council on Tall Buildings and Urban Habitat (CTBUH), global stats for tall buildings set a new record: 106 skyscrapers rising 200 m or above completed in 2015.

In fact, from 2010 to 2015, the number of ´supertalls´ has doubled. With increasing population, especially in developing countries, skyscrapers may well become the new normal. This trend is also gaining prominence in India; the recently released Model Building Bye-Laws 2016 define buildings higher than 15 m of height without stilts and above 17.5 m of height with stilts as high-rise. (Read ´Provisions for High-rises´.) However, challenges in execution remain. Nayan Raheja, Executive Director, Raheja Developers, highlights one: ´Breaking the old rules of construction and limitations in introducing the latest technologies´. Building contractor Ani Ray, Managing Director, ACC (Arabian Construction Company), that is doing the tallest buildings in Mumbai, Delhi and Kolkata, adds, ´In tall, you have to decide the methodology and equipment upfront; so, flexibility is less for any subsequent changes. Also, shortage of experienced technical and skilled manpower.´

Jairam Panch, Managing Director, Turner Project Management India, lists some: Safety issues such as fire considerations, wind issues, open shafts, falling materials, adjacent pedestrian and vehicle traffic; logistical challenges such as phasing, deliveries, material and transport stacking and traffic movements, workforce transport and evacuation, egress and welfare provision, temporary power and water; having approvals and permits in a timely manner; optimising cranage strategy to allow efficient movement of materials; and concrete placement up to the higher floors.

All considered, CW PROPERTY TODAY lists technologies and systems that are essential to build tall.

Smart plan
Elements in a smart design or plan include foundation design, geometry of the building, wind load testing, fire-fighting and alarm systems, vertical transportation, and appropriate selection of materials. ´Focusing on these and the involvement of the project team - clients, contractor, consultant and project manager - from an early stage of design ensures a well co-ordinated, efficient and constructible design,´says Panch. To this, Raman Sapru, President-EPC, Omkar Realtors & Developers, adds, ´Success also depends on how well you manage logistics.´

Structural analysis
Modern computer software determines a structure´s behaviour of the building frames under various loading conditions.

´These tools enable designers to economise without compromising on safety,´shares Kamal N Hadker, Chairman & Managing Director, Sterling Engineering Consultancy Services.

He adds, ´Structural engineers are required to take into consideration various Indian Standards for designing all the structural elements. Detailed structural designs are prepared to ensure safety against wind and earthquake forces.´And, advances in parametric design and computer modelling - with platforms such as Rhino and Grasshopper linked to structural finite element analysis programmes - have kept structural designers in pace with challenging architectural designs. Panch says, ´We advocate utilisation of performance-based design, a procedure for designing with actual forces and building responses without utilising overly conservative prescribed code provisions.´

Omkar has used software such as STAAD and ETABS to calculate the building´s movement. Sapru adds, ´As the building gets higher, some columns may shorten; to observe this and to check verticality, we have used a GPS monitoring system in Omkar 1973 in Mumbai.´

Wind tunnel test
At the preliminary design stage, wind pressures on glass facades, wind loads on structural frames and building motions can be determined with local codes or standards. For buildings beyond 120 m height and having an aspect ratio of more than five, it is necessary to get a wind tunnel testing done. ´If such a specialised agency is appointed right from the concept design stage, valuable suggestions received from them can save overall cost of construction,´shares Hadker. And, senior wind engineering consultant K Suresh Kumar, Principal and Managing Director, RWDI Consulting Engineers (India), says, ´The scaled model should be tested in a wind tunnel to determine wind-induced responses accurately.´Wind tunnels are long boxes with a fan at one end and instrumented model at the other; when the wind blows, the building´s response parameters are measured and analysed with recommended design loads. The wind tunnel-derived loads supersede code-derived loads and are used for the final design. ´Once constructed, the pressures and motion of the building can be monitored using equipment. But at this stage, these measured quantities are only useful to compare with wind tunnel-derived numbers and for the betterment of wind tunnel simulation,´adds Kumar.

Formwork
Advancement in formwork includes self-climbing systems, wall panels, grid element slab form, circular formwork and monolithic formwork. The shuttering system is the heart of a high-rise. Recommending aluminium shuttering, which is also now available for columns, Dr HM Raje, Director, Raje Structural Consultants, says, ´The box-type methodology has better structural stability to protect horizontal deformation.´Omkar 1973 has used Grocon and Doka shuttering systems procured from an Australian and Austrian company respectively. Also, they have procured aluminium scaffolding from an Irish company. Lodha World One is using column formwork, hybrid systems and jump-form from Grocon, Peri and others. Ray informs, ´In jump-form, which costs about Rs 60,000-80,000 vertical per sq m, the shutter automatically goes up after the casting is done, assuring verticality.´

Precast technology
Precast is not just easy to manage but reduces risk factors too. Using precast products under ideal conditions allows to rely on the quality of the end product. ´But, the main difficulty is the cost of transporting and erecting precast panels, especially in high-rise buildings,´says Hadker. While the technology is yet to be optimally used in India, Kumar Bharat, Director, BCC Infrastructures, says, ´It eliminates the need for a large workforce, thus addressing the concern of sourcing skilled labourers.´The company has been using this technique in its ongoing project in Ghaziabad-Bharat City. Bharat adds, ´The construction process is organised and standardised, and dimensions are more accurate, rendering a superior finish essential for robust high-rise structures.´Raheja Developers has also been adopting precast technology in building its latest projects. Raheja shares: ´Its main advantages are quality, speed of construction and a value-for-money product. The technology helps save up to 64 per cent of construction time compared to normal methods.´

Tower cranes
Cranes work at high altitudes and need to be flexible as, sometimes, there is insufficient space in high-rise buildings. ´Generally, high-quality cranes can cost between Rs 6-7 crore,´says Ray. Tower cranes or boom cranes mounted on demountable structures offer the best combination of height and lifting capacity. ´They can be mounted on a movable or fixed platform and reach all around as per boom length and work in all weather conditions; only checks and balances are required,´says Raheja.

While Lodha World One and Supernova are using luffing crane with highest capacity and flexible boom length, Omkar 1973 has used Liebherr 180 HCL 8/16, 50 m boom length luffing cranes.

Concrete pumps
Pumps, placer booms and pipelines may incur about 5 per cent of project cost. Panch explains, ´The large floor plates of a high-rise tower are usually split into an even number of pour cycles to achieve a repetitive pouring process.´Ray explains: ´High-rise requires pumping of various concrete from high grade to lower grade at different height levels.´So right concrete mix is crucial to avoid jamming the placer boom and pipeline.

´In Lodha World One, M95 grade has been used,´informs Ray. And Sapru adds, ´Flowability of concrete in Omkar 1973 was a challenge. We have used Schwing Stetter Concrete pumps, Putzmeister articulated boom placer at the top. Further, we made use of an automatic climbing system (C) for the core and columns. We could achieve five to six days a slab cycle, pumping 15,000 cu m a month.´Ray shares, ´In India, we have cast a floor in seven days.´

Putzmeister´s BSA 1408 HD is a very popular and reliable concrete pump for high-rise projects. It has completed various projects successfully all across India and particularly in Mumbai, where most of the new buildings are of +200 m height. Every component of this pump is suited for high-rise application. BSA 1408 HD was used to effectuate the World Crest-Prince Tower project at Worli in Mumbai.

´Maintaining the cohesiveness and homogeneity at this height was no problem,´says Wilfried Theissen, Managing Director, Putzmeister Concrete Machines. ´BSA 1408 HD has mastered heights, but this was the first time that the machine has pumped 50,000 cu m concrete of higher grades to a height of 350 m.´BSA 1408 HD has some remarkable features, which makes it stand out among the present stationary concrete pumps available in the market. Some of its features include Putzmeister original S valve technology, which is most suited for abrasive concrete and high delivery pressure with low wear and tear. Also, Putzmeister´s 1408 HD has chrome delivery cylinders and FFH hydraulic technology to name a few, which result in better efficiency with lesser maintenance in Indian conditions.

High-quality materials
Seventy per cent of the project cost is spent on materials for the structure, shares Ray. For building tall, concrete grade between M60 and M100 is used. ´Also, for smooth pumping of concrete, high grade admixtures and superplasticisers are needed,´shares Raje. ´And, for speed, high-tensile grade of steel, now available up to 550 D, is required. Corrosion inhibitors are also used in concrete to avoid corrosion, thus increasing the life span of the structure. Also, cathodic protection, done at the foundation level itself, eliminates corrosion activities thoroughly.´Today, capsules of inhibitors are available that can be injected in RCC structure, which converts into vapours and this protects the steel from corrosion. ´Further, lightweight materials such as dry walls and blocks with a density of about 700-800 kg per m are used to reduce weight,´explains Raje. And, Sapru adds, ´We have imported special Mitsubishi-made aluminium composite panels (ACP) from Japan, which are fire-retardant and have high durability, and hence, longetivity. High-grade concrete for the building helped us reduce the size of the columns and build a leaner structure. And use of post-tensioning in slabs makes the building lighter.´Omkar has also used low E coating for the glass, used epoxy-coated pipes and variable frequency drives for Motors to make the building durable and efficient. Also, for Raheja Revanta, high-quality materials in cladding, external doors and windows and glass and steel in railings as well as in pipes and conduits have been used.

Safety and security Generally, safe features comprise about 2-3 per cent of the project cost. ´Water sprinkler, fire hydrant, fire notifier, smoke detectors, pressurisation in lift wells and staircases, etc, are used,´shares Sapru.

´Importantly,´says Raje, with floating column systems and girders, dampers or shock absorbers are used.´The taller the building, the higher the displacement in an earthquake or wind. ´To avoid these, dampers and outriggers are used,´Raje adds. Outriggers can be used at 1/3rd or 2/3rd of the height. ´Another system, yet to come to India, is base isolation,´Raje points out. ´With this, during large earthquakes, the structure vibrates horizontally, like a building on wheels.´

Elevators
Good elevator design should be based on an independent traffic study - computerised analysis or simulation - based on estimated building population.

As Amit Maitra, Managing Director, Lerch Bates, explains, ´An optimum number of lifts is imperative in terms of capacity and speed, conforming to the National Building Code, including fire lifts, and appropriate fire evacuation procedures should be ensured. As buildings get taller, larger-capacity lift cars at higher speeds become needed.´(Read more on the planning and latest advancements in elevators for high-rises on page 122). Elevator is the lifeline of a building and the breakthroughs in elevator technology have made it possible for buildings to grow tall. Antony Parokaran, CEO, Schindler India, adds, ´For high-rise buildings, it is critical to plan the correct number of elevators considering the type of building, its tenancy, population, etc.´Schindler´s advanced traffic analysis tool based on real-time simulation helps plan the optimum elevator configuration while designing buildings. ´Our expertise in high-rise projects is evident from Schindler installations in landmark high-rise buildings such as Shreepati Arcade, Antilia, Imperial Towers, Omkar Altamonte, etc.´

Also, the Lodha World Towers will be equipped with high-speed Schindler elevators (S 7000), some of them running at a speed of 8 m per sec, the fastest in India.

Glazing and facades
Every day, there are new advancements in the glazing and facades for building; what is essential is that these products adhere to basic design parameters and find their way into the design in a manner to help make the building sustainable. As Manit Rastogi, Founder Partner, Morphogenesis, says, ´A building needs to be designed keeping orientation and shading in mind. Hence, the latest products in glazing and facades need to understand U-values and solar heat gain coefficient to make buildings more sustainable.´Ray adds, ´Double-glazed toughened glass is generally preferred.´And, Sapru says, ´Double-glazed glass with low-E coatings reflects the heat back, thus further reducing HVAC load.´

Construction software
Building Information Modelling (BIM) helps visualisation, fabrication, coordination and construction planning using one universal model. ´During and after construction, it helps in facilities management, improving life-cycle performance and reducing costs,´shares Rastogi.

Speaking on Building Management Systems (BMS), Ray says, ´BMS incorporates features such as access control for parking, public address system, fire alarms, electrical, plumbing and all other services.´Sapru adds, ´The objective of an Integrated Building Management System (IBMS) is to operate and monitor the various systems from one remote location of the building, collect data, analyse it, and ensure efficiency on a continual basis.´

Smart buildings
Energy-efficient solutions for high-rises that are cost-effective and deliver comfortable environment for occupants are imperative. Johnson Controls has developed innovations to make buildings smarter and more sustainable. Shrikant Bapat, Country General Manager and Managing Director, Building Efficiency India, Johnson Controls, shares, ´Metasys Building Automation System is an intelligent system that connects a building´s HVAC, lighting, security and protection systems, enabling communication on a single platform and delivering critical information to facility managers to make savvier decisions.´The system has an installed base of over 100,000 systems globally, including landmark buildings such as the Shanghai World Financial Center in China and Abeno Harukas in Japan. Also, a solution from Johnson Controls, in partnership with Microsoft, connects data streams from sensors on equipment such as smart connected chillers to the cloud, allowing unprecedented insight into building operations. And, Bapat shares, ´Tri-generation, a fully automated system, allows for the simultaneous generation of electricity and useful heat and cooling in a single process, providing improved energy-efficiency and reduced emissions.´

In conclusion
While there are several technologies that make skyscrapers a success, building tall is no cakewalk for India. Ray urges the need for a proper pan-India committee for high-rises to ensure standardisation. Further, CW believes modifying the Indian Building Code to include requirements of high-rises, followed by a proper implementation process, will be the true foundation to build tall.

Quick Bytes

  • Tall buildings are becoming the new normal and gaining prominence in India.
  • New provisions for high-rises under the recently released Model Building Bye-Laws 2016.
  • Need of the hour: A pan-India high-rise committee, modification of the Indian Building Code to include requirements of high-rises, followed by a proper implementation process.

PROVISIONS FOR HIGH-RISES
As per the recently released Model Building
Bye-Laws 2016, buildings higher than 15 m of height without stilts and above 17.5m of height with stilts shall be considered high-rises. Provisions include:

  • Plot area
  • Means of access
  • Peripheral open spaces including set backs
  • Parking spaces
  • Doorways
  • Revolving doors
  • Stairways
  • Lifts
  • Basements
  • Compartmentation
  • Ramps
  • Corridors
  • Glass fatade, service ducts, shafts, refuge area, vents
  • Staircase and corridor lighting
  • Electrical services
  • Alternate source of electric supply
  • Air-conditioning
  • Transformers
  • Gas supply
  • Boiler room
  • Helipad
  • Disaster management or fire safety
  • Sustainable environment and buildings
  • General such as architectural elements
  • Structural safety

- Seraphina D´souza
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