Tensile structures @ Academy of Architecture

Tensile structures have always beckoned me starting with my Architecture days at academy. Delving into the recent past  one recalls three instances of  the use of tensile structures, specifically woven meshes.

Use of highly curved surfaces generated between undulating high- and low-points of anchorage ensure minimal unbalanced surface stress and hence the otherwise necessary engineering calculations are avoided.

The elliptical form of the edge balances biaxial different tensions, which result due to the manual induction of stressing the net.

The edges of all these structures are built with a constant rope number all around.

If “n” = number of ropes per meter of the surface edge,

R1, r2, r3… r (n) = radius of (n) edges

Number of ropes in the edge cable = n (edge) = e1.r1, e2.r2…e (n) r (n).

The number of ropes per meter run of the edge is directly proportional to the radii of the edge.

A net built in this manner expands similarly geometrically if stretched out from the corners/ edges. All tension relationships remain the same.

Nets (and membranes) with this type of biaxial different tension and elliptical edges can be constructed in a variety of forms.

(1)     Event: UIA-UNESCO Seminar on affordable Education Spaces.

Year: 1997

Materials: Nylon ropes and steel turnbuckles

Erection time: 8days

During the campus development for the Seminar on Affordable Spaces for Education for All (ASEA)in 1997, the students saw a need towards creating a highlight in the amphitheatre. which was nevertheless shaded by an existing Pipal tree (Ficus religiosa).  A faculty member, architect Khalil Shaikh, guided the team of students in their endeavour. Having decided on the extent of the roof coverage, the form was conceptualized as a cable net with alternating high points and low points along its perimeter, and converging towards the apex- the trunk of the Pipal tree. Setting-out was carried in the adjacent playground, with the initial surface having a simple knotless interspersal of nylon ropes connecting the perimeter cables.

The entire fabrication was later rolled up and carried to the actual place of erection, demonstrating the “a priori”- characteristic of a cable net with regular orthogonal mesh-size that become unequal triangles at the edges. However, this process happened to be one of trial and error due to handling inexperience by the students and also the fact that unrestrained meshes bunched together, causing problems during the unfolding of the roll. The final form generated by suspending and tensioning the mesh from its pre-determined anchorages. After tensioning the edges with turnbuckles, each length of rope along one direction was physically pulled taut and knotted. Due to the mutual perpendicular disposition of the ropes, tensioning in one direction automatically induced stressing in the other direction, generating a tensioned surface structure.

(2)     Event: Zonal convention: National Association of Students of Architecture (NASA)

Year: 1996

Materials: Nylon ropes and steel turnbuckles

Erection time: 8days

As the venue to the Zonal NASA convention, the front and rear open spaces of the college premises provided an uninterrupted linear space for convention events such as on-the-spot games, workshops etc. However, due to lack of shade, these spaces required shade structures of a nature that would complement the mood and the setting.

Hence tensile structure canopies were constructed using jute fabric and jute rope. The building process, under the guidance of architect Khalil Sheikh, followed the sequence of setting out on the ground and the subsequent elevation to the chosen heights of anchorage. The final tensioning using turnbuckles, yielded an undulating and continuous canopy, which was formed without any mesh knots. This allowed the meshes to adjust into spatially curved forms without upsetting the overall geometry of the structure

(3)     Event: Annual convention: National Association of Students of Architecture (NASA)

Year: 2005-2006

Materials: Nylon ropes and steel rods

Erection time: 4 days

The two-dimensional graphical counterpart of the theme "Pulse" was translated into a 3D mesh and formed a part of the main stage backdrop. The mesh was woven by hand by the author, with periodic assistance from the NASA volunteers. The original choice of High density PolyPropylene rope was found to be too slippery for this scale, necessitating an n-th hour change in the final mesh. The high-point of this experience was the performance of Indian Ocean on the very stage.