18 October 2019

Table of Contents for Tall Buildings





Guest Article-Capacite

Vertical concerns

 

 

NARAYAN NEELAKANTESHWARAN dilates on the challenges and opportunities in the construction of high rise structures

 

 

Increasing urbanisation is driving the vertical growth of city buildings, leading to the construction of more and more high rise towers the world over. The race to increase the number and height of such skyscrapers is led by Middle Eastern and Chinese cities. In India too, and in Mumbai in particular, we see an increasing trend in the development of high rise buildings to make best use of the limited land area available for development.

 

A tall building entails additional focus on engineering design, construction methods, site logistics, formwork technology, construction planning, resource scheduling, process quality assurance, product quality control, occupational health, construction safety, environmental impact management, climatic considerations, speed and cost of construction, wastage control, productivity control etc.

 

In finalising the engineering design, it is important to ensure due consideration of the construction methods and formwork technology to be adopted besides site logistic constraints if any. Ease of construction is a must for quick execution of the work without compromising on quality.

 

 

A well designed structure combined with positive encouragement from the developer enables casting of successive floor slabs every fifth day in a sustained manner using aluminium formwork, as proven by Capacit'e in the Lodha Splendora Thane project. A less practical approach aimed at minimising the theoretical cost of construction by optimising quantities may render a complicated design that substantially slows down the construction process, benefitting none in the end.

 

 

The construction methods to be adopted, the site logistics and the formwork technology to be adopted need to be established before finalisation of the engineering design. This requires the construction contractor to be engaged at the engineering phase itself, so that value engineering with the contractor’s inputs benefit the project.

 

 

Alliance model of contracting works best in such cases and India would see more and more examples of successful outcomes under this model in the years ahead.Target costing with pain share and gain share features under this alliance model tend to align the interest and motivate all stakeholders to work towards successful completion of the project in minimum time and cost, ensuring compliances. This model has been widely adopted in Australia and some other Commonwealth nations and is best suited where the developer has to engage with multiple entities at a time, including the architect, structural design consultant, contractors for general, civil and mechanical; electrical, plumbing, finishing, interior, façade works besides other agencies and government bodies.

 

 

In terms of construction materials and building technology, the popular choice is among (a) concrete slabs with concrete columns and blockwork/glass walls, (b) concrete walls and slabs, (c) concrete core with structural steel columns and steel deck sheet encased with concrete as slabs. All the three methods have been adopted in various high rise projects undertaken by Capacit'e in India.

 

 

The formwork technology available for use in construction of high rise buildings includes automatic climbing system formwork, aluminium formwork, tunnel formwork etc.

 

 

The automatic climbing system formwork such as the ones deployed by Capacit'e in Lodha Park Worli, LodhaAltamount Road and Four Seasons Residence Projects enable quick rise in the concrete core structures, with their hydraulic jack lifting technology cutting down on the tower crane dependency for vertical movement of formwork at the rate of four lifts per month.

 

 

The aluminium formwork such as the ones deployed by Capacit'e in Transcon Sheth Auris Serenity Malad Project enable all round construction of more than three floor slabs a month, with the potential for further reduction in the cycle time.

 

 

Tunnel formwork such as the one handled by Capacit'e at the Radius Deserve SRA Chembur Project has been successfully used in countries such as Turkey for construction of mass housing as well as high rise structures of over 50 floors, with the advantage being the ability to cast a successive floor slab every fourth day. Weld mesh reinforcement, flexible conduits and quick setting/strength gaining concrete technologies enable such rapid construction.

 

 

Besides formwork technology to be adopted, equipment selection process is crucial as well. For example, pumpability of concrete vertically to reach the upper floors of a tall building is a key consideration in choosing the concrete pump. Similarly, the type of tower crane considering load carrying capacity, luffing feature or self-climbing feature etc. is an important choice to make.

 

 

Site logistics arrangements, including vehicular movement at ground level, material storage, handling and lifting arrangements and safe working zones, debris management etc. need special attention for high rise buildings.

 

 

Enabling work arrangements besides safety requirements particularly in respect of electrical lines to the upper floors, water pipelines to / drains from the upper floors, mobile toilets and fire fighting arrangements need detailed planning and implementation for optimising cost and productivity.

 

 

Construction safety is of utmost importance in high rise construction. A rigorous selection and training process is called for, including the conduct of vertigo test to determine suitability of labour force for working in heights. Personal protection equipment is must for all, including safety belts as necessary. Safety screens including hydraulic system assisted ones are a standard feature in high rise buildings. Safety nets for fall protection augment the prevention of accidents. A well detailed and specifically drafted Project Safety Plan, covering the occupational health, construction safety and environment impact management aspects, besides emergency response planning, hazard identification and risk assessment registration is must, custom made for the high rise project. Its dissemination through tool box talks and its enforcement through robust communication are of utmost importance in ensuring a safe and secure work place. 

 

 

Climatic conditions in general and the effect of winds and stormy weather conditions in particular need special care while designing and executing the tempoww rary or enabling works and while establishing and operating the assets. For example, the horizontal wind load effect at an elevation of 200 m in a coastal city like Mumbai requires appropriate strengthening in the safety screen design and appropriate factoring in the free standing height of tower crane mast.

 

 

Working time restriction is a significant factor in construction planning and tower crane hook time scheduling, so that productivities are optimised across various functions and in material movement. This is especially so in view of the combination of restriction of heavy vehicular movement in urban areas, limited storage area available at the project sites and the restrictions imposed by the surrounding commercial/residential/institutional entities particularly with respect to construction noise control.

 

 

Process quality assurance is essential for product quality control. The cost of rectification, repair and rework gets prohibitively high as the building rises upwards. Generation of such wastage does not add value to the end customer and hence it needs to be eliminated in line with lean construction principles. It is therefore necessary to do things right the first time, every time. A well detailed and specifically drafted Project Quality Plan, covering the technical specifications, construction methods, material selection and testing process control, work inspection and testing plan etc. is must, custom made for the high rise project. Its dissemination through training and its enforcement through robust practiceby the internal quality team of the civil contractor are of utmost importance in ensuring process control.

 

 

Surveying activity is crucial in high rise buildings construction. As the number of floors increase, the verticality, the line and levels, the angular dimensions and alignments require closer monitoring using lased guided survey equipment.

 

 

The pace of progress of work is grossly different between the non-typical and the typical floor reaches of a high rise building. Whereas the progress is quick in the typical floors once a particular rhythm is achieved, in the non-typical floors, the speed is dictated by the constructability aspect of the engineering design rendered.

 

 

The challenges in construction of tall buildings are many but the advantages they provide in the residential, commercial and institutional space are humongous. With the proper acquisition of the skill set by pooling a competent team of architect, structural design consultant and civil contractor, this can be well managed by a developer to successfully construct tall buildings.

 

 

In constructing high rise buildings in India, best global industry practices are adopted now. However, the focus on cost reduction and the seasonal variation in labour availability in India make high rise construction opportunities a tricky affair. High degree of project management skills and resilient cash flow planning are essential to meet the challenges in this regard. The quality of human capital accumulated by a contractor and its financial strength therefore form primary factor in selection of contractor by the developer of a high rise building project.

 

 

Tall buildings add to a city’s pride, besides providing additional space for meeting the residential, commercial and institutional requirements.With the ease of construction permits and the Government’s thrust on development of Smart Cities, bulk of which are on redevelopment of congested urban spaces, there is bound to be an increase in the construction of high rise buildings in these locations in the coming years. Economies of scale are easily achieved in tall buildings and they occupy less land area than would have been the case in accommodating such floor space in buildings of less than 15 m height. High rise buildings in packed smart city districts with well-connected multi modal transport systems are therefore going to be the preferred choice across cities in India in the years ahead.

 

 

The author is Whole Time Director, Capacit’e Infraprojects

 




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