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A tensile structure is a structure elements carrying only tension and no compression or bending. A tensile membrane structure is most often used as a roof, as they can economically and attractively span large distances. These type of structure is commonly found in sports facilities, warehousing and storage buildings, and exhibition venues.

## History of Tensile Structures

The first development of practical  calculations of stresses and deformations of tensile structures, shells and membranes by a Russian engineer  Vladimir Shukhov.  he designed eight tensile structures and thin-shell structures exhibition pavilions for the Nizhny Novgorod Fair of 1896, covering the area of 27,000 square meters.

In recent days, tensile structures have found great popularity and have been used in many places. Some of the notable building are Munich OlympiaPark, The Millennium Dome London and Ashford Designer Outlet United Kingdom.

Fig 1 : OlympiaPark at Munich

Fig 2 : The Millennium Dome in London

## Types of Tensile Structures

The classification of tensile structures are made on the plane in which the tensile forces are acting in the structure. On this basis, the tensile structure are divided into following types.

### 1. Linear Tensile Structures

Linear tensile structures are the structure in which the all the member are in linear tensile forces. This linear members are supported by the compression members , but the major loads are carried out by tensile members. Common example of these structure is cable suspended bridges. The main pillars acts as compression members, but the whole load is carried out by the cables which are in tension.

Fig 3: Tensile forces acting on suspended bridge.

Linear tensile structures are further classified into following types,

• Suspension bridges
• Draped cables
• Cable-stayed beams or trusses
• Cable trusses
• Straight tension cables

### 2. Three-dimensional Tensile Structures

Three-dimensional tensile structures, is a compilation of elements that are primarily in tension, with the compression being transferred to a central mast and down into the ground.  The most common occurrence of three-dimensional tension can be seen at sports arenas and usually serve as roofs for these structures.

Fig 4: Tensegrity Tensile Structures

Three-dimensional tensile structures are further classified into following types,

• Bicycle wheel (can be used as a roof in a horizontal orientation)
• 3D cable trusses
• Tensegrity structures

### 3. Surface-Stressed Tensile Structures

Surface-stressed tensile structures are same as other 2 tensile structure, but the surface members are tension bearing members. Fabric tensile structures are the great examples of Surface-stressed tensile structures, where the vertical pillars hold the special deisgned fabric which is in tension.

Fig 5: Fabric Tensile structure

Surface-Stressed tensile structures are further classified into following types,

• Fabric structure
• Prestressed membranes
• Pneumatically stressed membranes
• Gridshell

## Shapes of Tensile Structures

The four basic shapes used in the tensile structures are,

### 1. Conical Tension Structure

Highly effective for covering large areas, a conical tension structure is easily identified by its tent-like shape. Conical designs can feature either single or multiple masts. For both design options, membranes are tensioned between a ring at the pinnacle and the lower perimeter support columns. Cones are especially effective in areas that need to comply with high rain or snow load regulations.

Fig 6: Conical Tension Structure

### 2. Hypar or Anticlastic Structure

As one of the most common of all tensioned membrane structures due to its aesthetically pleasing look, hypar (hyperbolic paraboloid) shapes are notable for their excellence with shape retention and water runoff. These structures rely on two opposing curvatures, also known as anticlastic, for their stability. This type of structure is ideal for shade over seating areas or high traffic walkways.

Fig 7: Hypar or Anticlastic Structure

### 3. Parallel Arch or Barrel Vault Structure

These symmetrical curved parallel arch designs form an incredibly functional tensioned membrane canopy that can span long distances such as a sports arena or smaller areas such as an entryway.  Depending on the spans, a barrel vault system can be a very cost-effective way to incorporate tensile membrane on a project due to the repetitive nature of the design and efficiencies of materials.

Fig 8: Parallel Arch or Barrel Vault Structure

### 4. Cable Net & Membrane Structure

For long-span tensile membrane roofing applications typically found in stadiums or large spaces, 3D cable net or cable grid structures are an efficient solution for lightweight tensile architecture.

Fig 9: Cable Net & Membrane Structure

1. Shelter of environment (sun, rain, wind)
2. Translucency in general, possibilities to design light effects
3. Light weight & Durability
4. Endless form possibilities, catching character
5. Short building time, off site manufacturing of structure, less site interruption time
6. Large spans
7. Recyclability and Eco friendliness
8. Adaptability to exciting building technologies (steel, glass, cement, stone)
9. Simplicity of maintenance  & Easy repair or replacement

Read More : Types of Tension Members in Structural Steel Construction

#### Gopal Mishra

Gopal Mishra is a Civil Engineer from NIT Calicut and has more than 10 years of experience in Civil Engineering and Construction. He is the founder of The Constructor.