Developments in Steel Construction in India
Summary of State Of The Art
Prof. C.N. Yadunandan
Historical
Pre independence: - 1900-1950 before establishment of large scale steel units.
Post independence: - The dominance and development of concrete upto 1990.
1990 onwards: - Advent of multinationals – Revival of steel structures – New forms and materials.
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Recent developments in steel construction
Pre-engineered building systems - Advent of multinationals, offering pre-engineered building frames transformed our industrial constructions from drab looking sheds to attractive, economic and fast build options. Apart from a low slope built up gable frame at 5-7.5m spacing with spans from 12-60m.
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The PEB’S included other new features like;
- Colour coated steel and galvalum sheets for roof & side cladding.
- Light gauge purlins.
- Flashings, gutters, turbo ventilators etc
Some pictures of PEB’S general c/s, features are all shown
- These frames are made in parts in factory and assembled using quality tools.
- A large number of local companies also offer PEB’S now solutions for total systems start from Rs 350 to Rs 650/sqft depending on the span.
Light gauge steel sections - New sheet processing and production gave way to thin cold formed sheets extruded into various stiff forms drastically reduced the weight of support systems and structure required for purlins and small scale building and portable cabins are now economically viable using light gauge framing. Tata Bluescope pioneered this development.
Developments in sheet technology - Long lasting protection system, drawability into very thin corrugated shapes led to galvalums and colour coated sheets of 0.2-0.6mm thickness to be used for roofs and claddings. Other developments such as;
- Tap screwing
- Standing seam sheets
- Crimped sheets to suit curved shapes
- Insulated double layers sheets
- Standing to shapes like tiles and other designs have increased the scope of applications of metal sheets offering more durable, fast and economic solutions.
Decking sheets - Even though composite floors were developed many years back, local production of decking sheets cost of shuttering and increasing labour costs have made composite floors an acceptable option for commercial buildings.
Advantages of composite floors are
- Avoiding shuttering
- Avoiding finishes
- Reduction in time of construction
Sheets of 0.8-1.2mm thickness with various profiles are offered in the Indian market.
Closed tube structurals- Developments in production technology made way for closed tubes- circulars, square and rectangular. It an alternate to open sections like angles and channels. Closed structural's have the advantages of;
- Higher strength due to production methods
- More efficiency offering economy due to symmetry in c/s
- Durability against corrosion
- Ease of fabrication as sections can be directly welded on to each other.
- Companies take Tata structure now offer a large range of closed tube sections.(structures made with closed structurals)
Self supporting truss less curved sheet roofing - Advances in sheet bending and forming led to this form of roofing where large spans can be roofed without supporting trusses by using;
- Thicker sheets
- Deeper corrugations
- Bending to curvature
This is now widely adopted already and established roofing alternate spans of the order of 15-60m are possible.
Developments in bolting and welding technology - High strength steel bolt making technology and new generation tools for bolting and welding have improved quality and precision of connections. Bosch, hilti etc are companies making specialized tools. Carbon dioxide welding, submerged are welding etc have made construction of built up sections and connections of good quality possible in India now.
Development in fabrication technology - Drilling, cutting, stamping tools, CNC machine based lathes have transformed steel fabrication process. Improved pipe and section bending tools and jigs have made profile bending of steel elements to curved and bent shapes increasing the scope of applications.
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Software for steel design- A steel detailing and joint design using computer aided design has now been sophisticated and many design firms have been detailing with just joint design and detailing for various types of structures. Web connectivity has helped designers to outsource detailing jobs.
Corrosion protection and fire proofing - Advances in corrosion protection and fire resistance. Various technologies have developed coatings to enhance corrosion resistance and fire resistance so that steel structures are more durable and have therefore a lower life cycle cost.
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New structural types - Due to changing technological developments, new steel structural types such as communication towers, Petrol service station roofs, bunker houses, mobile office cabins, Roadside kiosks, bus stop shelters etc. have been effectively used.
Information management and organization - One significant development on the last decade is the formation of INSDAG – Institute for Steel Development and Growth. It has put together all steel industries hub between the industry, consultant and user. It has been instrumental in updating Indian codes for steel design and providing handbooks and design data books for design of various types of steel structures. It has significantly contributed to the steel sector since its establishment a decade ago. With all the developments the steel construction sector is regenerated and growing with vigour. The future is very bright for steel structures.
Acknowledgement: This article was presented by Prof. C.N. Yadunandan, M/s Yasha’s Consultants, at the National Seminar on Steel Structures- Steelcon, held at Mysore on 26th and 27th of April, 2013.