New code of practice for steel construction
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The much awaited IS 800 is the basic code and the prime document for any structural design and has influence on many other infrastructures, writes A.R.Santhakumar
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On the safe route: Steel has become an integral part of a durable structure. Photo: Nagara Gopal
Technology has been one of the main drivers of business and societal change and globalisation. Recently the Bureau of Indian Standards has brought out the long awaited modern state of the art code of practice for general construction in Steel IS 800:2007. Steel has become an increasingly integral and important part of our daily lives – at work, at home and for making durable infrastructure.
IS 800 is the basic code and the prime document for any structural design and has influence on many other infrastructures such as bridges, chimneys, cranes, tanks, structures, cold formed light gage steel section etc. in addition to multi-storey buildings. The revised standards will enhance the confidence of designers, engineers, and architects and the whole building industry. It has opened a new era for building architecturally sleek but safe and economical construction in steel.
Major modifications
The current code is in line with international concepts of design and will enable globalisation through participation of our engineers and designers in multi-national and overseas projects. In particular
i) The code permits the use of any variety of structural steel if the provisions of the standards are complied with. This will enable free use of the new varieties of medium and high tensile steel now being produced in the country.
ii) Special provisions for earthquake resistance, fatigue, durability and fire resistance have been included.
iii) The provisions of the standard are based on limit state method incorporating latest international developments in steel design in Europe, USA, Japan etc and the research done in various laboratories in India.
Basis of design
The objective of design is the achievement of an acceptable probability that the structure will perform satisfactorily for the intended purpose during design life. With an appropriate degree of safety, they should sustain all the loads and deformations, during construction and use and have adequate resistance to certain expected accidental loads and fire. The structure should be stable and have alternate load path to prevent collapse under accidental loads.
Recycling
Steel is one of the world’s most recycled materials. Buildings made with recycled materials do not have to be ugly. The strength and formability of steel allow the construction of curtain walls, roofs with stunning aesthetics, minimal maintenance and long service life. Steel structural members and sections are highly recyclable. At the eventual end of its life, the structural steel in building can be recycled and returned to use as new steel with lasting value.
The use of this standard is expected to promote economy in the use of structural steel by establishing rational, efficient and optimum designs for structural steel fabrication and construction. The provisions of this standard are such that the serviceability requirements have been appropriately revised for various types of structural use of steel.
Flexibility in design
Structural steel will enable use of long spans and slender columns in multi-storey buildings. Also the dead load will be much smaller than concrete buildings. This will affect savings in foundation costs. In addition, the ductility of steel can be cleverly used for earthquake resistance.
It is important to reduce the time required for construction. In concrete structure, considerable delay takes place because of the requirement of curing. Concrete structures take about a fortnight to complete each floor where as this cycle time can be reduced to about a week if structural steel is used. There will be a major advantage for infrastructural projects such as bridges. A four-storey building can be completed with in 45 days if steel intensive construction is adopted.
Avoiding waste
Steel intensive construction avoids waste. The site of construction is neat. There is no requirement of sand. There is no requirement of form work. The life cycle cost of steel is less. Environmental pollution at site is less and construction is less noisy. Overall steel construction is amenable for adoption of all modern technologies.
Use of high strength steel and cold form steel will enhance the economy further. The total material consumption is less. With modern painting technologies, corrosion problem can be entirely taken care of. Use of Steel concrete composite construction can bring in further advantages to the construction industry.
The use of the new code will ensure economy, safety, durability, fire resistance, and earthquake resistance aesthetics and recycle ability. The structures such as bridges and flyovers will be sleek and invite people to use them. In short it will lead to a technological revolution in economical use of resources for building our infrastructure and at the same time save the precious natural resources to the future generations.
The author is emeritus Professor, Department of Civil Engineering,
IIT, Madras and former Dean,
Anna University.
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