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Structural Grammar

Design

With the world’s eyes now trained on India as the next design-strong economy, Savitha Hira examines the country’s technological architectural language and discovers untold benefits in the use of structural steel to frame tall storeys.

The term ‘structural steel’ instantly conjures up vivid images of post-modern architectonic marvels like Santiago Calatrava’s Turning Torso in Sweden, Zaha Hadid’s Dancing Towers in Dubai, Rem Koolhas’ CCTV Headquarters in Beijing and the world’s largest steel structure, Beijing’s Bird’s Nest Stadium – among other iconic buildings that dot the international landscape.

Closer home, we have the airports in Mumbai, Bangalore, Hyderabad, Delhi; Rajiv Gandhi National Stadium in Delhi, Patni Computers’ corporate office in Chennai, Infosys in Mysore and Pune, Turbhe Railway Station in Navi Mumbai.
These all-steel structures constitute some of the most futuristic compositions grounded in elemental and conformist theories of construction and design. Steel structures expound a vocabulary that not only pushes the architectural envelope in terms of formal design, but is commemorative of the socio-cultural and technological renaissance of the ‘tall’ building.

This beatific vision is partially challenged by the distressing 26/11 collapse of the World Trade Centre, New York. The twin towers were the first super-tall buildings designed without any masonry, made wholly in tube-frame steel structural system.

Of course, it’s highly debatable whether the towers finally buckled due to the tremendous heat generated from the extensive raging fire inside the upper floors. (While the fire would not have been hot enough to melt any of the steel, the strength of steel drops markedly with prolonged exposure to fire and the elastic modulus of the steel reduces, increasing deflections.)  Yet, structural steel has managed to establish a distinct dialect with the urban skyline.

In the Beginning: It was in the late 1700s, when iron supports were first used in a British mill, that metal began to be used in building construction. After almost a century, steel technology that was a known solution for industrial, agricultural and automobile sheds, bridges, dams and other infrastructural projects, began to be used in high-rise applications based on engineering developments of the 1880s.

The 285 foot (87 m)-tall Flatiron Building in New York was one of the first to use a steel skeleton in 1902. This was furthered by Mies van der Rohe, an influential and world-renowned architect who played a leading role in the new glass and steel architecture of the time. Significantly, structural steel was used in the historic Esplanade Hotel in Mumbai in 1869 as well as for the steel and stone edifices of the Victoria Terminus Railway station in Mumbai in 1887.

A rapid expansion of the steel building industry was observed in the early 1940s when the military began using aircraft hangars constructed from 100% steel. Quonset huts (a take-off from the portable Nissen huts used largely during World War I) also became standard during this period.

The Armed Forces acquired these curved roof shelters to serve as barracks and shops, while the general public used them as storage. Thousands of these structures were built, as their assembly called for just a few workers and hand tools. Besides, they could easily be taken apart and relocated later if necessary.

Following World War II, quick construction and bargain purchase prices of pre-fabricated steel structure systems were emphasised with no regard for visual appeal. So, while industrial-use sheds were cost-effective options, architects like Mies van der Rohe’s steel skeleton extravaganzas with large-scale glass curtain walls such as the Seagram Building in New York (1958) or the National Gallery in Berlin (1968) became icons of modern architecture.
 

Pre-engineered steel buildings dramatically improved over time in terms of quality, weather resistance and aesthetic appeal; and gradually the techno fad caught on across the globe. Lord Foster’s St Mary Axe in London (2004), also known as the Gherkin and Swiss Re Building, was a statement that redefined high-rise construction and gave an impetus to a new vocabulary in multi-storey buildings.

Design-wise
The foremost plus point of designing with steel is to achieve large column-free spans. Though this is ideally suited to a commercial or corporate set-up, it is also increasingly being used in bungalows and stand-alone homes across the country. Next in line is the tremendous flexibility it offers in terms of design. “Of course, one has to design within the standard prescribed availability of sections,” says Abhin Alimchandani of STUP Consultants.
 

“But the beauty of designing the structure lies in the lightweight nature of steel construction and the expressiveness of the material via its detailing; while precision-engineering controls the project from its onset.” Moreover, since the sections are prefabricated, execution is speedy and quality control is assured – unlike the long-drawn-out vigilant process of the RCC construction.

Also, apart from the whole building being in steel, there are several structures like space frames that utilise a multidirectional span and are often used to accomplish long spans with few supports. Larger portable stages and lighting gantries are also frequently built from space frames and octet trusses.

The use of high-performance steel construction in high-rise buildings addresses both strength and flexibility issues. It strengthens the design by preventing large sideways movement (lateral drift). Flexibility prevents structural damage, while resistance ensures comfort for the occupants of the building and protection of glass, curtain walls and other features.

Design manifestations in the form of high-tensile steel chords used for suspension of various features become both a structural and aesthetic highlight in a project – thus paving the way for lighter, freestanding design elements that enhance spaciousness and visual appeal. Several miniscule parts especially used for joinery can be applied exposed in their original format, drawing out the raw appeal of the structure.

Finally, the variety of sections available helps the designer to experiment with an array of sizes and shapes. Steel tubes are of special interest to architects from a design-effectiveness viewpoint and to engineers from a structural-effectiveness viewpoint.

Unique architectural characteristics are easily executed in steel. Overall, the direct advantage lies in precision-driven engineering that predetermines the design to a near-perfect on-site ratio and facilitates the material being pre-ordered down to the smallest detail, without wastage, time loss or inconsistent labour.

Tech-wise
“The architect was once a virtuoso; today he is a conductor,” says Kamal Malik, a renowned architect based in Mumbai but working with a global wherewithal. “Unless he has the requisite expertise, his designs cannot be translated into the real idiom. To realise this, the architect has to be driven by design relevance and meticulousness in engineering and execution.”

Facilitating such a mindset are several steel companies like Tata Structura, Corus Group, etc., that manufacture wall cladding, roofing, colour-coated steel products and a variety of sections, plates, tubes and pipes, sheets, joists, purlins, building envelopes and the like in accordance with building codifications and quality standards. 
 

“We manufacture high-tensile steel up to 70 mpa strength, the use of which could reduce the weight of the structure without compromising on strength and safety,” informs Vikram Amin, executive director, Essar Steel Limited. “We also have facilities to fabricate girders, box girders; castellated beams, etc., that help reduce construction time.”

Rajesh Maheshwari, head of Technical Marketing (Coated Steel), Tata BlueScope Steel, expounds on the eco-friendly virtues of steel: “Earlier, steel-making processes used to be energy intensive; but over a period of time, energy inputs per tonne of steel have been considerably reduced by process innovations and improvements. Steel can be used as a more eco-friendly material as it is 100% recyclable and provides great opportunities for reuse. At times, it can be reused without any modification. Similarly, its consumption can be reduced, e.g. by using thinner, higher strength steel instead of thick, low strength – which in turn further improves other related efficiencies. Steel processing also provides opportunities for the use of eco-friendly chemicals. For instance, the usage of shot blasting instead of pickling; or water as a solvent in a paint system instead of hydrocarbons.”

Penny-wise
“We’re evolving as an industry,” insists Malik. “Now, the client examines capital expense vs. operational costs and makes an informed decision.” The construction of steel structures is quick, saving on installation costs and ensuring early occupation of the building.

The lifecycle cost of steel is also less due to reusability and recyclability.  Another facet to a structural steel framework is that, in its exposed form, it doubles up as a design element for the interiors as well, negating the application of an elaborate interior design and thus compensating costs.

Adds Amin: “Using steel can reduce construction time by about 30%. By using good steel structural design, INSDAG (Institute for Steel Development & Growth) has recently proved that a 40-storey building can be built at a cost 10% lower than otherwise.”

The downside expressed by developers and architects alike is the additional cost of fireproofing steel. Instances where budgets are high do not pose a hindrance to costs, and the best intumescent coatings may be used. Shabbir Kanchwala, VP Project Coordination, K Raheja Corp, Mumbai, opines that it is cost-effective to build in steel when the material is procured in large quantities for infrastructure projects – but not when a variety of steel sections are required in small and medium quantities for a residential building.

Vivek Garg, Senior Associate Engineer with Mahimtura Consultants Pvt. Ltd., among the oldest structural engineers and architects involved in large-scale design-build projects, refutes the notion that steel structures are 2.5 to 3 times more expensive than conventionally-built RCC structures. Speaking about the lifecycle of a residential or commercial building, he maintains that one needs to look at costs through a wide-angled lens to obtain a clear view.

The Hybrid Persona: Steel has a wonderful quality to contrast and combine with different materials to form composite structures. “The need for steel in a structure is immediately felt when you have to refurbish an old building, connect two buildings, add elements of design like space frames, canopies, create a central atrium, a lightweight freestanding interior staircase, elevational features and the like without additional dead load on the structure,” says Seema Puri, an upcoming architect who is working with steel elements as hybrid combinations with glass and concrete.

Steel with concrete makes for the best composite design and is most prevalent. Whilst steel coated with fireproofing agents constitutes a stand-alone feature, it is often encased in concrete to offer additional strength and longevity. Steel augments formal architectural language when partially exposed in combination with different materials like wood, glass and fabric.

Several architects are fascinated with the material, but deterred by the costs of fireproofing steel or even bogged down by the dearth of a skilled workforce. This is where a composite design effectively fulfils all parameters of design vs. cost. Dome, Arch, Hexagon, Polygon are shapes that can be fabricated as per requirement and can be clad with polycarbonate sheets, fibre sheets, toughened glass, etc. Combinations of steel with wood, with glass, with fabric are aplenty and can be commonly seen at malls, hotels, parks, etc. Again, the visual impact is determined by the strength of its design.

Future Stock
The extent of awareness and knowledge is a clear indication of the positive and negative sway of this pendulum. While some builders who are majorly into the residential segment feel that steel merely adds on to their costs and does not offer flexibility in design, those involved in large commercial and corporate set-ups prefer the alternative of a steel structure.

The bottom line lies in predetermination and relevance of design and not in mindless aping: what type of building is being built and for what purpose; does the design really merit the use of steel and to what extent – as a core feature or a hybrid element; availability of a skilled engineering team; timeline of the project, budget and the like. As Alimchandani reaffirms, “In India, structural steel is being used more often in building projects, as recycled steel is an effective sustainable solution for green buildings.

The demands of better quality and greater speed of construction makes steel a more viable material. Of course, steel fabrication requires greater skilled labour and more complex manufacturing; but as the construction industry in India progresses, more refined steel structures would grace the urban skyline.”

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