High-rises are changing the skyline of cities, and how
A deep look into the construction of high-rises and its nuances
Technology is an amazing game-changer. What seemed impossible a few decades ago has transformed into something routine. So is it with India’s rapidly changing skyline that has witnessed the emergence of high-rises. The successful construction of these structures can be largely credited to modern technologies, and also green that has evolved.
High rise buildings are becoming prominent these days due to scarcity of land, and increasing demand for business and residential space. There has also been technological advancement and innovations in construction methods which are being adopted. Rakesh Reddy, director, Aparna Constructions & Estates, says, “From an engineering perspective, as high-rise buildings get taller, their design becomes increasingly influenced by factors that are otherwise less significant for shorter buildings. The structural systems of high-rise buildings must carry vertical gravity loads, as well as lateral loads, such as those due to wind and earthquakes.”
Adding to the construction of high-rises, Sachin Bhandari, CEO, VTP Realty, says, “While constructing tall buildings, concrete caisson columns bearing on rock or building on exposed rock itself is used along with bearing piles and floating foundations. The lateral stiffness is a major consideration in the design. Another factor is creep and shrinkage due to climatic conditions of the location, and the cumulative vertical movements that could cause distress in the structure and induce forces into horizontal elements especially in the upper regions.”
High-rise buildings are typically over 15m in height, and are exposed to both static and dynamic loads. There are safety measures for the building and occupants as well. Mahesh Khaitan, director, Salarpuria Sattva Group, says, “As per the National Building Code (NBC), even before the developer applies for plan sanction, they should have NOCs from airport authorities, BWSSB, BESCOM, electricals, earthing systems, fire departments, etc.”
In terms of design and construction, they are need to create safe and habitable spaces. Amitabh Kumar, senior VP, engineering, Puraniks, says, “High-rises require special materials like high strength steel, higher speed of elevators, strong glass, and special fittings for windows/cladding. They also require a special design approach for MEP like zoning on plan and building elevation, drenchers and fire check floors. Features like fire check floor, BMS with a network of fire detectors and sprinklers are used for fire detection and suppression. Sustainability is gaining ground in high-rise design and construction with reduced embodied energy of the building, zero energy/net positive energy buildings (using wind turbine and solar panels on cladding) and vertical forest (typically on social spaces) spread on building elevation.”
Interestingly, high-rises possess specific design challenges for structural and geotechnical engineers, mainly if located in a seismically active region or if the underlying soils have geotechnical risk factors such as high compressibility or bay mud. Ashok Mohanani, chairman, EKTA World, says, “New and old building designs, building systems like the building standpipe system, HVAC systems, fire sprinkler system and other equipment create striking problems. In order to allocate less wind contact, pass on more daylight to the ground and be more lean, many high-rises have a design with hindrances. It is more of a common concept in Asian countries like India, China, Singapore, Japan, etc.”
Hard act to follow
With modern technology available ready at hand, developers are adopting new materials for quicker and better construction.
Yashodhan Tere, head design, The Wadhwa Group, says, “When it comes to high-rises, the whole approach towards adoption of materials needs to be different. Most of the walls apart from structure members such as columns or reinforced concrete shear walls are non-structure concrete walls. It helps to gain speed since it gets built along with the structure. It goes without saying that flexibility of clients to do the interiors as they want to must be considered. Glass used for the façade requires high quality specification to withstand wind pressure and stop the heat or sun rays entering the interiors.”
Vendors have also designed unique products for high-rises. Atin Thacker, marketing director, Geeta Aluminium, says, “Under the product range, Geeta Series Plus, we have introduced combination windows. This concept has been specially created for high-rises with top sliding and bottom fixed windows. With these windows, the cost of reinforcing the interlock is reduced as the height of the sliding is reduced due to the fixed portion below. The coupling profile attached below the sliders gives more strength to the whole structure. They also reduce the wind pressure impact on the interlocking of windows/doors due to less height of sliding windows.”
Elevators are another unique aspect of high-rises. Sebi Joseph, President, Otis India, says, “The Otis SkyRise system, designed for the world’s tallest buildings, uses the SkyMotion machine, which is highly energy efficient. The machine’s lighter weight makes it easier to install and its smaller footprint saves building space. In addition, all SkyRise elevators come standard with the Otis SkyBuild self-climbing construction elevator. And once construction is complete, SkyBuild goes directly into service as a SkyRise elevator.”
A range of advanced materials have made construction materials lighter, more energy efficient to produce, and multifunctional. Some of these are self-healing concrete, illuminating cement, cooling bricks, air-cleaning bricks and cigarette butts. Rajendra Varma, director, Omkar Realtors & Developers, says, “These new materials and applications are innovations in building materials and not only enhance the quality of construction but also reduce outlay, offer energy-efficient solutions, provide better mechanical characteristics, and infuse sustainability in construction. Till yesterday, construction industry used synthetic materials such as wood, cement, aggregates, plastics, metals, bricks, concrete, clay, and sand, as the most common building materials.”
The functional demands of high-rises include the use of durable materials. Apart from the basic structural materials, modern projects require a variety of secondary materials. Rajat Rastogi, executive director, Runwal Group, says, “These are for a variety of purposes such as construction chemicals, waterproofing materials, durability, etc. Concrete design and construction practices are strength driven. We use M70 grade concrete for our projects. High performance concrete is also used in high rise structures. Besides this, there is Alccofine and GGBS for better strength.”
High-rises require high strength cement for building a strong foundation of the structure which is processed and mixed with the help of advanced machinery. Shivamurthy KB, associate VP, projects, Adarsh Group, says, “High-rises are built with steel or reinforced concrete frameworks and curtain walls of glass or polished stone. Light weight blocks were used for economical design of the structures and thus reduce the cost of construction. Similarly, centralised gas bunk, and garbage chute (waste collection system) is more economical in terms of operational aspect in high rises.”
Adoption of new methods
Another developer that has adopted advanced construction methodology is Kalpataru. At its project Kalpataru Avana, the company has used advanced engineering techniques in its design and architecture, like cross bracing and outrigger technology, that provide for larger living spaces and substantially reduce wastage of space with few columns inside the apartments. A spokesperson from the company says, “We were among the early ones to use wind tunnel testing (WTT) in India and still remain among the few who do this. WTT helps design and engineer buildings that can withstand gale force winds (very heavy winds) without causing undue stress on the building elements. Instead of estimating wind induced forces based on generic wind codes, it provides accurate and factual information of natural forces impacting the building, leading to a design that is perfectly optimised. It also helps design and create living spaces that offer the highest resident comfort and safety as it enables the testing of various parameters under real time conditions.”
Kalpataru has also used an advanced BMU (building maintenance unit) by CoxGomyl, Australia, so that each of the two wings of Kalpataru Avana have separate façade cleaning systems.
Similarly, Srinivasan Gopalan, CEO, Ozone Group, says, “We are using software such as STAAD and ETABS to calculate the building´s movement. As the building gets higher, some columns may shorten; to observe this and to check verticality, we are using a GPS monitoring system for our project The Autograph in Mumbai. The tools for structural analysis enable designers to economise without compromising on safety.”
The difference starts with the project planning. Design requires longer duration as building geometry and arrangement of vertical elements requires multiple coordination. The process is further prolonged when specialist consultants such as wind studies, vertical transport and façade step in. Manoj Kothari, director, Sheth Creators, says, “Every project is unique and requires adoption of a new technology, ideas. Use of aluform shuttering is advantageous and has now become the new normal for high-rises. In Mumbai, construction of basement, variation in strata are other challenges tackled using sheet pile walls or adopting pile foundation, etc. Usually pile cap or raft requires huge thickness of 2500mm or more. In such cases, ice concrete is used to counter increase in temperature due to early thermal reaction. Similarly, gravity based system such as water supply and drainage requires accessories to control the pressure.”
There is a lot of research being carried out in improving cement as well as steel used in construction. Tushar Srivastava MRICS, president, business development & marketing, Capacit’e Infraprojects, says, “Another area which is rapidly gaining the attention of developers is pre-cast which is supposed to facilitate faster construction and drastically reduce the requirement of skilled manpower. However, this technology is still in the early stages of acceptance in India and will require some more time before we can assess its benefits.”
With newer and advanced technologies coming in, construction of high-rises has become easier. Modern construction technology is a process to produce more, better quality homes in less time.