STRUCTURAL SYSTEMS Submitted by: L.Siva deepti reddy b.arch. 8 th sem SIMPLY CURVED SUSPENDED ROOFS

CABLES the rope and the cable have long been used in one dimensional suspension structures or in double curved surfaces. In nature, such structures can be found in a spiders web or a fly’s wing. A fish net is also a membrane like structure. Membranes made out of fabric, such as sail, the tent and the umbrella, employ the structural properties of rope and cloth. The cable is ideal for lightweight bearing structures over long spans.the best known earlier works using cable structures are suspension bridges. These elegant, almost floating structures make full use of the tensile properties of steel cables and result in enormous spans. The idea of building with cables has recently extended to roof construction.

Thomas Telford's Suspension Bridge This was the first iron suspension bridge of its kind in the world The road and arches on the Menai Suspension Bridge

SIMPLY CURVED SUSPENDED ROOFS Suspended roofs with simple curvature behave like a group of cables suspended in parallel.each cable deforms under its own load, independently of its neighbours. Curved roofs of this kind have also been cast in concrete. The result is a simply curved suspended shell. Such simply curved concrete shells, for this is how they act ratherc than as suspended roofs, are relatively heavy, whereas the chance of achieving lightness is the most attractive thing about a genuine cable structure.

Under load each cable deforms independently Under asymmetrical loading the structure will be unstable. Complete stability can only be ensured by tying down the ends of the transverse stiffeners Transverse stiffeners are introduced

EXAMPLES Frederick Severud, with architect Matthew Nowicki, made possible the design of the suspended roof of the Raleigh Arena in North Carolina (1952). With its unique saddle shape, it fast became a pilgrimage stop for engineers. it is a nonlinear space, breaking away from the rigid grid. One of nowici’s preliminary designs shows how the impression that the roof is supported by the perimeter wall The raleigh arena saddle, stretched between its two tilted arches thus became a prototype of the suspended roof or more correctly the stressed cable roof curved in two mutually opposed directions.

SKETCHES OF RALEIGH ARENA

Sports arena, paris The roof is a doubly curved network of cables spanned between two compression arches which run in the longitudinal direction of the arena. The saddle shaped roof, spanning between two longitudinal compression arches and the side walls consist of network of cables apart from the concrete arches,cables are the only structural elements employed. The plan and the section show how the arch thrusts are transferred to common foundations tied together beneath the stadium floor.