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SPORTS CENTRE, SOKOTO, NIGERIA




 

At spans measuring more than about 50 metres cable trusses can be competitive with the standard rigid plane truss and have a practical span limit of up to about 150 metres, beyond that of the rigid truss. Because cable steel has about five times the strength of normal structural steel and because the cable truss does not suffer from instability all members being prestressed in tension, the cross-sectional areas of the cable truss are very much less than those of the equivalent rigid truss. This being so, the cables are light but still look strong, the appearance reinforced by their curving lines. In fact their flexibility gives them a considerable additional load-carrying capacity over the equivalent rigid structure. One drawback to cables is the cost of anchorages. This design for a sports centre is a proper solution of these problems: while the inherent advantages of the cable truss have been fully exploited, the cost of providing anchorages has been overcome by attaching the cables to the high concrete structure used for the grandstand.

The sports centre can hold 4000 visitors and has an area of 3900 sq m. It contains a 40 x 20 m pitch which is set 4.3m below ground level, with its long axis in the north-south direction. Either side is concrete seating, that nearest being cast directly on the ground and that farthest away being precast and supported by a cast-in-place concrete grandstand structure. The cable roof has a clear span of 71 m across this, the cables running in the long east-west direction of the total plan area covered. This arrangement lets in natural light at either end of the pitch and allows the use of the grandstand as a supporting element for the roof. Emergency staircases are provided at the four corners of the building. The cable roof has eleven cable trusses spaced 5m apart which are attached to the uprights of the grandstand and tensioned from the outside. The cables are covered by an insulated sheet metal roof. The roof has a slight parabolic curve in the short direction, as well as in the long direction, to allow run-off of rainwater. The seating of the grandstand is supported by a series of three-pin concrete frames stabilised in the short direction by nearly vertical concrete walls cast between them.

Working stresses in the cables are 600 newtons per sq mm.

Notes:

cable roof вантовое (висячее) покрытие

cable truss висячая ферма

clear span пролёт в свету/чистоте

grandstand n. трибуна

pitch n. зд. спортивное поле

seating n. места для сидения

 

Ответьте на вопросы к тексту

1. Why were cable trusses used in the structure?

2. What is the drawback of the cables?

3. How was it overcome?

4. Where is the pitch set?

5. How was concrete seating built?

6. What is the roof structure of the sports centre?

7. What are the working stresses in the cables?

 


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