BUILDING CONSTRUCTION

PNEUMATIC STRUCTURES

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Pneumatic Structure

Pneumatic (greek word) “pneuma”(meaning breath of air).

A very lightweight enclosed structure,

Impervious material and Supported by the difference in air

pressure between the exterior and interior of the structure.

Atmospheric air supplied by pumping instruments(fans , blower ,compressor).

Pneumatic structures

Air inflated structure

Types of Pneumatic Structure

Air Supported Structure1. Air under low pressure is

directly fed under envelope.2. Network of cables stiffens the

fabric3. Rigid ring at the edge. Air Inflated Structures1. Air under high pressure 2. Fills the supporting elements .

Properties Light weight: The weight of the structure as compared to the area it covers

is very less. Low air pressure is sufficient to balance it. Span:    For pneumatic membrane, there is no theoretical

maximum span as determined by strength, elasticity, specific weight or any other property. 

Safety: Accidental circumstances are avoided, as they are very light. Pneumatic structures cannot be destroyed by fire quickly and

totally. Quick erection and dismantling: Suitable for temporary

constructions because they are as easy to dismantle and establish.

 Economy Good natural : There is a lot of flexibility in getting sun light (50%-80%)

Hubert H. Humphrey Metrodome

Located at Minneapolis U.K. Air supported pneumatic

structure Architectural style :

modernism Structural engineer : David.

H .Geiger Building Type : Stadium. Height (tip) 59.44 m Length 227.08 m Width 192.64 m

Metrodome Roof (Materials)

The roof is made of two layers: the outer layers : Teflon

coated fiberglass the inner layer : acoustical fabric. By design, the dead air space

between the layers insulates the roof; in winter, warm air is blown into the space between layers to help melt snow that has accumulated on top.

Teflon-coated fiberglass : 1/16" thick. Liner material: 1/32" thick woven

fiberglass. The cables used are 3 in. in diameter. Air supplied by 20 ninty horse power

fans.

Construction Mechanism The compression ring that runs

around the upper rim of the stadium to distribute the stress from the restraining cables

 Metrodome has a ring that slopes up to follow the angle of the rising roof fabric

Cables are fastened to compression ring that angles upward to match fabric roof's slope

CABLES

TIE DOWNS

TEFLON FABRICATED ROOF

Construction mechanism

The fabric roof compression rings have been supported by an earth berm or a precast wall that was structurally independent of the stadium's seating.

Tiedowns and rocking supports allow compression ring to move.

To give the compression ring the necessary independence, the engineer used pairs of pin-ended steel supports that form movable bents and allow the ring to float above the stands.

Each of the bents is braced by a 12-in.dia. steel tiedown that helps pass the roof cable loads into the stadium's foundation.

The tiedowns also act as lateral springs that keep the ring in equilibrium.As the compression ring moves in response to stress, the tiedown bends in and out and forces the ring back into its equilibrium position..