The growing demand for accommodation has created a boom in the real estate sector and has led to an increase in high-rise buildings. With the recent modification in the norms of FSI with plots now having built-up area 2.5-8 times its size is surely paving the way for soaring high-rises.
Broadly speaking, there are two types of building structures. One is residential and other is commercial. Both types of structures have their specific needs to be taken care of during construction level itself as the requirements are highly different. For a commercial space, factors necessary are large open space, natural light, heat absorbing façade, fast and large elevators, etc. Whereas in a residential structure one needs to take care of the layout of the apartment, the material used for the flooring of kitchen, fittings in the bathroom, among other things.
There are some factors that are common in both the structure and these are universal safety features like fire fighting system, use of fire resistant paint and wirings, features that take care of outside temperature, humidity and ventilation, safety railings for height, and safety in terms of security is also essential.
Raj Pillai, executive director, concrete products division, Sobha Limited, says, “Adequate safety precautions need to be taken in order to ensure that high-rises are comfortable. Most importantly, we need to ensure that the building is maintenance friendly. With increased number of floors, the effort and cost for maintenance goes up. Regular quality checks done during the construction process will ensure that the buildings are maintenance-free to a large extent.”
For comfortable living the developers should design such buildings which provide amenities that can help to carry out normal household chores in an easy manner. Gaurav Shah, director, marketing and sales, Ravi Group, says, “For example, ultra-luxurious residencies can have trash chutes that can dispose the waste in a hygienic way. Apart from this, the tower should maintain ample ventilation slots as the oxygen pressure decreases.”
A faulty design and construction practice at the pre-planning stage often leads to repair and maintenance problems in high-rise buildings. “Some common problems which a buyer should look out for is water stagnation within the construction, cracks in the walls, fungal growth. These problems can cite poor architectural detailing in design or usage of defective materials which doesn’t have the ability to water proof,” says Nimesh Bhandari, co-founder and CEO, RealtyCompass.
High-rises go through a detailed structural analysis supported by wind tunnel testing and simulation study as these are impacted by wind pressure which could make the building sway. “Based on the said study the structure is designed which determines the material usage and different types of technology which can be considerably different compared to the traditional ones,” says Rajendra Varma, director, Omkar Realtors & Developers.
Structural analysis for high-rise structures is performed on some of the sophisticated Finite Element Method (FEM) packages. High-rise structural analysis involves solving numerous numerical problems and in such situations, use of advanced solvers reduces time for analysis and gives efficient results. Rohit Mohan, head of design, Emaar MGF Land Ltd, says, “Base isolation and passive energy dissipation devices are frequently used in high-rise structures to reduce the response of structure to earthquake forces. Seismic and wind forces play a very critical role in design of high-rises.”
It is mandatory to have safety measures as high-rises have 1,500-2,000 residents living in them. Various problems like longer egress times and distance, evacuation strategies, fire department accessibility, smoke movement and fire control are a major concern for developers while designing the building. In such cases there should be multiple exits or fire emergency exits as residents need to evacuate the building immediately. These tall sky scrapers should also provide with backup generators during electricity or power cuts which shall ensure safety of the residents using the elevators or the stairway, adds Shah of Ravi Group.
Some of the fundamental measures undertaken for high-rises are formwork design and planning, application consultation, training for site managers and foremen, technical and safety-related documentation, on-site project support and supervision of work flows.
Hiral Sheth, director, marketing & sales, Sheth Creators, says, “The high-rise tower’s plot size should be at least 1,000 sq-m. It should have two separate staircases. The width of the approach road to the proposed structure should be 18 metres. Providing gas supply through inbuilt pipeline has become mandatory to avoid intensive damage.”
Safety is a major concern during the construction of a tower. Safety towards the workers and for the people who are going to reside there needs to be incorporated at the planning stages itself. Towers are often more expensive to build. Besides the high cost of construction, towers require high maintenance. Manju Yagnik, vice chairperson, Nahar Group, says, “The tallest towers make use of new technologies like special lightweight building materials, shock absorbers and mass dampers to prevent excessive swaying during earthquakes. All of these systems add to the cost of a tower, making it economically feasible only in certain cases. But there are necessary safety features. Thanks to the technology today, there are materials available for exterior and interior, which are light weight and yet strong and durable.”
Safety measures in high-rises primarily include structural design with respect to seismic and wind forces, and fire and lift safety measures. Mohan says, “These include increased structural integrity, enhanced fire resistance of various materials, provision of egress in case of fire, assembly areas such as refuge terraces, helipads, electrical wiring and design properly done and executed taking a higher level of precaution and safety measures, smoke sealing of the building at all possible locations such as shafts, facade etc., fire zoning, pressurisation of vertical transportation, site planning to enable fire tender movement, and access on all sides. Efficient fire detection and fire fighting system such as addressable fire alarm system, smoke extraction system, automatic fire fighting system, wet risers, fire hydrants, water curtains, etc. also play a very important role.”
Apart from mandatory code compliance related to structural design and fire safety norms, factors which can make high-rise experience more comfortable and safe are efficient vertical transportation planning, reliable power back-up system, efficient disaster planning, appropriate signage design, enhanced security and access control system.
There are several techniques specifically related to the structural analysis and design, which are effective in helping the achievement of sustainability objectives for high-rise building projects without affecting building performance. These techniques help evaluating the building orientation
and massing. The results of such an analysis typically include support reactions, stresses and displacements. The materials technology is subject to specific loadings such as axially loaded bars, prismatic beams in a state of
pure bending, and circular shafts subject to torsion.
Mivan technology is an excellent replacement to the conventional technology with marked advantages of quality, time and requirement of skilled resources, as the structure is generally designed as load-bearing walls and slabs. The whole assembly is shuttered and poured monolithically giving it an advantage in terms of structural stability, both on lateral movements, seismic forces and effect of wind forces on high-rise building, adds Sheth.