Urban population is growing at the rate faster than expected and hence the providing residential units is one of the most important challenges of the developing countries like India. The precast technology is spreading its wing from infrastructure projects such as tunnels, bridges and flyovers, underpasses etc., to residential sector. Precast construction is one of the most appropriate solutions for managing construction needs of urban areas. Benefits of precast construction and requirement of mass housing is expected to make the technology popular. Present paper provides an insight into the sequence of entire process of precast construction for residential application with a multistoried precast housing apartment in Bangalore as a case study.
Raj Pillai, Bharathi Ganesh, Deepthi M, Neelavathi S, Alice Priya A
Introduction
The 2014 revision of the World Urbanization Prospects by UNDESA’s Population Division notes that the largest urban growth will take place in India, China and Nigeria. These three countries will account for 35 percent of the projected growth of the world’s urban population between 2014 and 2050. By 2050, India is projected to add 404 million urban dwellers, China 292 million and Nigeria 212 million (1).
Today, 54 per cent of the world’s population lives in urban areas, a proportion that is expected to increase to 66 per cent by 2050. Projections show that urbanization combined with the overall growth of the world’s population could add another 2.5 billion people to urban populations by 2050, with close to 90 percent of the increase concentrated in Asia and Africa, according to a new United Nations report launched in 2014(1) and in 2018(1).
“Managing urban areas has become one of the most important developmental challenges of the 21st century. Our success/failure in building sustainable cities will be a major factor in the success of the post-2015 UN development agenda,” said John Wilmoth, Director of UN DESA’s Population Division (1).
The 12th Plan Working Group on Financing Urban Infrastructure estimated the urban housing shortage in India at about 29 million units. The demand for affordable housing is likely to rise from 25 million households to more than 38 million units by 2030, by when the urban population is likely to surge to 600 million. Poverty, the sheer scale of population growth and the huge rates of urbanization as people move from the countryside into the cities will add to the housing shortages (1).
India being a fast growing country, is changing its construction process in residential, commercial and infrastructural projects gradually from cast-in-situ to precast construction techniques. The technology is not just limited to infrastructure projects such as tunnels, bridges and flyovers, underpasses etc., but extending its wing widely into residential sector catering to the huge housing and infrastructure demand. The mode of changing scenario is encouraging Indian Reality Sector to adopt modern and innovative construction technology and practices (2).
The challenges of construction technology in thickly populated urban areas and fast developments over upcoming decades will have dramatic change in the sector due to the influence of various developments in information processing, global communication, industrialization, automation etc., in the field of construction. Precast construction technique, one such option is gaining popularity worldwide at a faster rate due to various merits of the construction process in comparison with that of cast-in-situ process.
Addressing the major concern of sustainability, precast technology reduces the huge amount various forms of waste generation of construction industry and optimises the utilisation of water and resources. It has also passed rigorous safety standard around the world for seismic and structural testing as well as fire safety, and is environmentally sound.
The precast technology is cost-effective and efficient when used in mass affordable housing, an answer to India’s affordable housing requirements. It helps to enable the investors to meet the expected boom in demand for mass affordable housing across India. A shortage of skilled labor in the building construction sector on one hand, increase of nearly 20 percent in the cost of labor and materials on the other hand has made precast technology an attractive solution to several contractors and developers.
The three broad categories in precast concrete construction practice are components, panels and volumetric. However, currently the residential building market in India is taking advantage of just the first of these options. Whilst companies have studied the potential for panelized or volumetric precast in their designs for housing applications as the most popular use for precast concrete, however, is in components. This includes walls, beams, floors, columns, panels, and stairs (1). The connections of precast structural joints are most critical parts to resist gravity loads and also lateral loads due to wind and earthquake forces. Performance of structure is assured only through an appropriately designed connections of precast structural members with adequate strength and ductility.
History of Precast Construction
Stonehenge, perhaps the world’s most famous prehistoric monument is the typical example of precast construction built in several stages about 5,000 years ago. Yet another unique stone circle, a precast unit was erected in the late Neolithic period about 2500BC (3). Precast technology is in practice in India from ancient time, the best examples are the ancient temples. Precast concrete was initially accredited in 1905 and John Alexander from Liverpool was the first to develop perfect idea of using precast concrete in modern design.
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