"Creativity has no limits because imagination has no boundaries." -Dr Shraddha Shukla.

Construction and Digital Technology advancements and material explorations have encouraged and equipped designers, engineers and fabricators to stretch beyond their ‘limits’ and explore. The need of spaces for larger gatherings, flexibility of space within, activities where visibility is important, where large movable objects are to be housed led to the concept of Long Span Structures or Wide Span Structures. Long-span structures create unobstructed, column-free spaces greater than 30m for a variety of functions. Use of long span structural systems are commonly seen in – auditoriums, covered stadiums, exhibition halls, railway stations, certain types of manufacturing facilities, aircraft hangars, etc.

Steel for Long Span Structures

The structural system needs to be carefully designed keeping a balance of several aspects like its weight, deflections (sway), foundation forces, etc. There are many materials and combinations for designing large spans, like RCC, timber, steel, conventional steel truss & RCC column combination, steel truss & steel columns, Pre-engineered building (PEB), etc. Steel is the major material for long-span structures. It is most often preferred due to its high strength and because it will not spread fire over its surface (after required treatment). Steel is cost effective, requires less maintenance than other traditional building methods, use of prefabricated steel members makes it an optimal solution in control and management (PEB), good durability - It can withstand extreme forces or harsh weather conditions, and is unreceptive to rust (after required treatment) and, unlike wood frames, they are not affected by termites, bugs, fungi, etc.

Structural steel components connect with one another to hold loads and supply full rigidity. Because of the high strength grade of steel, the structure is reliable and requires less raw materials compared to concrete and timber structures. Depending on each project’s applicable specifications, the steel sections may have various shapes, sizes and gauges made by hot or cold rolling, others are made by welding together flat or bent plates. Common shapes include the I-beam, Channels, Angles, Plates, etc.

Classification

1. One-way spanning structures

  • - Truss or lattice girder/ stanchion frames
    - Portals and Arches
    - Cable or Tie stayed lattice girder roof
anchient people

Steel Arches

- ©Pixabay.com

2. Combination portal or cable stayed spine frame with lateral lattice girders
3. Two-way spanning trusses - Vierendeel girders or space deck systems
4. Domes springing from circular or polygonal bases
5. One-way spanning cable girder and two-way spanning cable net roofs
6. Air supported roofs
7. Retractable roof structures

Case Study – Polycab Wired UH3 Plant, Halol, Gujarat

know your terminologies - steel history

- ©TataSteel

About the Company –

The company Polycab Wires Pvt. Ltd., a wire and cable manufacturing company in India. It has an annual turnover of around Rs. 4,500 crore.

Type of Contract -

Design and Build - Turnkey Contract

Contractor -

Devam Enterprises & Shree Prefab Steel Pvt. Ltd., a business development partner for Tata Structura in Gujarat.

Total Area -

40,000 sq. metre

Objectives -

Fast project completion, cost effective solution, Factory controlled quality, Solution that requires less maintenance, Flexibility for expansion, Energy efficient wall and roof systems, Eco Friendly building, Increase in structural stability, No sag rods for purlins, Increased torsional capacity

Structural System –

Portal frame structure

Material Used -

Tata Structura Hollow sections

Span –

120m (with five intermediate columns)

Height -

Maximum height at center -14m, Eaves height at the end is 8.5m

Steel section details –

HR (Hot Rolled) plates were used for the web and Tata Structura steel hollow sections were used for the flanges and had better stiffness against warping. Lateral bending capacity of the section was better, which indirectly enhanced the vertical bending permissible compressive stresses.

Advantages of using Tata Structura products –

weight reduction, cost savings due to reduction in weight, fabrication, transportation, painting cost all reduce due to weight reduction, ease of fabrication, ease of maintenance, etc.

This innovative design concept was fabricated to perfection. The project was completed within the stipulated time. Tata Structura steel hollow sections enhanced strength and stability of the structure and also enriched the aesthetic value and beauty of the structure.

Conclusion

Steel is a very versatile material. It is best suited for long span structures. The versatility of steel stimulates the designers and engineers to explore it and use it to suit their aspirations of creativity and ideas. I would like to end with a quote by Joseph B Strauss, ‘Ask of the steel, each strut and wire, . . . what gave it force and power.’

know your terminologies - steel history

- ©Y.Yukta

About this author
Arti Daga
Arti Daga

An alumna of Sir J.J. College of Architecture and NICMAR, Arti is a passionate and perseverant designer, academician, and fitness enthusiast. She believes, ‘Pursue your passion’ is the key to happiness and success.

About this author
Arti Daga
Arti Daga

An alumna of Sir J.J. College of Architecture and NICMAR, Arti is a passionate and perseverant designer, academician, and fitness enthusiast. She believes, ‘Pursue your passion’ is the key to happiness and success.