SPORTS HALL FOR SCHOOL OF GYMNASTICS AND SPORT, MAGGLINGEN, SWITZERLAND

The lowest four metres of the building, which mostly are below ground, are of concrete construction. The structure above this level is entirely of steel. The roof consists of seven trusses which are prestressed and have a span to depth ratio of 24, which is double that of a standard simply supported plane truss. Each of the seven trusses consists of five longitudinal members, connected by diagonal and transverse members to form a stable space truss. At each end, the truss is supported by two 406mm diameter by 25mm thick round steel tubular columns and, at the end of the three upper members which overhang the columns, a vertical prestressing cable is attached, the three cables being prestressed to a combined force of 300 tonnes and anchored to bedrock. Large-section steel sheets span between the longitudinal members of the truss and at the gable ends, where there are secondary steel columns, the sheets span the 4.20m distance between the truss and the columns and are flexible enough to accept the differential movement between the two. All columns are fixed at the base either by extending the column downward from the gallery to the main floor level or by using a very large foundation.

The prestressing cables cause additional tension in the upper members and compression in the diagonal overhanging members of the truss, which however reduces bending and deflection in the middle of the span. The trusses then function as if they were continuous construc­tions. They are designed to take snow loads of 300 kg per sq metre. Complete failure of the ties was also considered and was the critical factor in sizing many members.

Each space truss was erected in three sections, each of these sections in turn being made up by bolting together transverse members and plane trusses, which were shop fabricated in approximately 18m lengths; the plane trusses are the four containing the diagonal members of the finished space truss. The three sections were lifted by crawler cranes and placed on the columns and two temporary trestles before bolting up.

Apart from the prestressing used, this steel frame is also unusual in having no vertical bracing and no plan bracing in the roof, the former allowed by the fixity of columns at their base, the latter by the diagonal members of the space truss.

Notes:

crawler crane гусеничный кран

fixity n. закрепление

gymnastics n. гимнастика

trestle n. подмости

Ответьте на вопросы к тексту

1. What is the roof structure made of?

2. What does a truss consist of?

3. What is it supported by?

4. What is achieved by the use of the prestressing cables?

5. What was the construction technique used for space truss erection?

6. What else is unusual about this steel frame?