From Tents to Large Span Structures – Discussion 15

As in the case of most innovations, the inspiration always lies in history. The case with the awe-inspiring large span structures of today is no exception. The cutting edge technology behind these finds its roots in the logic of ancient sails which enabled the renaissance sailors to explore the world.

It was this fascinating story of tensile structures that was presented before our discussion forum in the form an admirably well-documented presentation by Ashwathi.

The presentation sought to give answers to specific questions like -

What is a tensile structure?

Tensile structure deals only with tensile force and not compression. The most important feature of these is that it can cater large span without a need to break the space with columns.

Then how is it supported?

Most of these structures are supported by steel cables whose size is determined by the span of the structure, some are even suspended

What make it so flexible? Is it the fabric used?

Though it is called tensile fabric, in reality these are sandwiched panels coated by weather proofing material whose size is determined by specialized software. The software converts 3d roof structure to flattened images and divides them to form panels.

These basic questions out of the way , she launched into an a series of examples to illustrate the various ways in which architects have utilized the potential of tensile materials.

She began the illustration by aptly quoting the master of Tensile structure,   Frei Otto who designed the Olympic Stadium of Munich. It had an acrylic cable net roof, a translucent structure which symbolized the new democratic and optimistic Germany.

Next in line was the . Millennium Dome designed by Richard Rogers which had an extremely eye-catching suspended roof . The roof was suspended by twelve 100m high pylons which denoted twelve months of a year or each hour of a clock face. Sydney Myer designed by Barry Patten is an example where the roof is supported by steel cable , 21.3m pivoted down the earth. Cable consisted of 173m long ropes of 9cm diameter each.

Jeddah International airport designed by SOM architects was very interesting as it is the world’s largest roof. The roof is divided into ten modules consisting of 21 tent units each supported by 46m high four cables in the corners. Two groups of five modules each on both sides of the central access road accentuate the pathway.

Burnham pavilion designed by Zaha Hadid for an artist, Thomas Gray was of a totally different technology. The temporary structure had 7000 bent pieces in which no two pieces were alike. Skylights were provided to create light and shadow effects  inside the pavilion. German pavilion designed by Frei Otto which took the shape of the contour to create a manmade landscape and Shukhov Rotunda designed by Vladimir Rotunda which is the first membrane roof were the other examples

What makes these structures free from sagging was a common doubt that arose after the presentation. As a part of clearing the doubt Aswathi explained how the structure is erected on site. In fact the structure is pretensioned as a prt of its erection on site and this makes it free from sagging.

The discussion was entertaining and informative and provided us a glimpse of the creativity that a wonder-material stimulated in inspired minds all over the world.

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