•PNEUMATIC STRUCTURES ARE ESSENTIALLY MEMBRANE STRUCTURES WHICH ARE STABILISED BY THE PRESSURE OF COMPRESSED AIR AND ARE TENSILE SKINNED • ITS STABLIZATION IS DONE BY PRESTRESSING THE MEMBRANE EITHER BY:a)PPLYING AN EXTERNAL FORCE WHICH PULLS THE MEMBRANE TAUT b) INTERNAL PRESSURIZING IF THE MEMBRANE IS VOLUME ENCLOSING. SUCH STRUCTURES ARE CALLED “PNEUMATIC STRUCTURES” .
• THESE STRUCTURES CAN CREATE ARTIFICIAL ENVIRONMENTS ADAPTABLE TO HUMAN USE .
• THE PNEUMATIC FORMS ARE BOUND TO INCREASE N POPULARITY, OWING TO THE TREMENDOUS FREEDOM THEY PROVIDE TO THE ARCHITECTS IN DESIGNING LARGE FREE SPACES
WITHIN THEM.
1) ITS PRINCIPLE IS THE USE OF RELATIVELY THIN MEMBRANE SUPPORTED BY A PRESSURE DIFFERENCE. 2) THROUGH INCREASING THE INSIDE AIR PRESSURE NOT ONLY THE DEAD WEIGHT OF THE SPACE ENVOLPE IS BALANCED, BUT THE MEMBRANE IS STRESSED TO A POINT WHERE IT CANNOT BE INDENTED BY ASYMMETRICAL LOADING .
THE TECHNOLOGY BEHIND PNEUMATIC STRUCTURES HAS BEEN LONG KNOWN TO US. BUBBLES HAVE AROUSED PEOPLE‟S CURIOSITY FOR LONG. THE MORE IMMEDIATE USE OF PNEUMATICS HOWEVER LIES IN THAT HAVE GRACED OUR SKIES IN THE RECENT PAST. THAT WAS ROLLED INTO PLACE WHEN IT RAINED. ‟, WHICH HOUSED LARGE RADAR ANTENNAE.
THEY CAN PART OF THE WORLD.
IN ANY
BUILDING WITH PNEUMATIC ROOF
LIGHT WEIGHT:a) THE WEIGHT OF THE STRUCTURE AS COMPARED TO THE AREA IT COVERES IS VERY LESS ) THE WEIGHT OF THE MEMBRANE ROOF , EVEN WHEN IT IS STIFFENED BY CABLES, IS VERY SMALL 3) LOW AIR PRESSURE IS SUFFICIENT TO BALANCE IT 4) EVEN WITH SPANS OF MORE THAN 100MTS, THE WEIGHT OF THE STRUCTURE DOES NOT EXCEED 3KG/SQUARE METRE .
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:FOR A BUILDING, THEN THE LIMITATION IS 500 FEET SPAN DUE TO ITS SELF WEIGHT.
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ANOTHER ADVANTAGE OVER OTHER STRUCTURES IS THAT, FOR PNEUMATIC MEMBRANE , THERE IS NO THEORTICAL MAXIMUM SPAN AS DETERMINED BY STRENGTH, ELASTICITY, SPECIFIC WEIGHT OR ANY OTHER PROPERTY.
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IT IS HARDLY POSSIBLE TO SPAN A DISTANCE OF OVER 36KM. WITH A STEEL CABLES AS THEY WOULD FAIL BECAUSE OF THEIR INABILITY TO SUSTAIN THEIR OWN WEIGHT. BUT WITH PNEUMATICS, SUCH SPANS ARE POSSIBLE.
:- PNEUMATIC STRUCTURES ARE SAFER THAN ANY OTHER STRUCTURE. HOWEVER, PROPER CARE SHOULD BE TAKEN WHILE ESTABLISHING •
ACCIDENTAL CIRCUMSTANCES ARE AVOIDED AS THEY ARE VERY LIGHT. • THERE ARE WARNING SIGNALS WHILE THE RELEASE OF RETURN VALVE. SAFETY FACTOR+ WARNING TIME IS QUIET LONG AS COMPARED TO OTHER STRUCTURES. • PNEUMATIC STRUCTURES CANT BE DESTROYED BY FIRE QUICKLY AND TOTALLY. :- IT IS VERY SAFE NO BODY CAN OR PASS THROUGH A PNEUMATIC STRUCTURE. IF AN AIR BAG IS CUT WITH A KNIFE/ PIN, A BANG IS PRODUCED.
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IN MOST CASES, PRESSURE OF NOT MORE THAN 80-100mm AND NOT LESS THAN 60mm.BUT MAN CAN WITHSTAND PRESSURES BETWEEN 0.20 ATM TO 3 ATM. THEREFORE NO HEALTH HAZARD IS PRESENTED BY CONTINOUS STAY IN A PNEUMATIC STRUCTURE. :- SUITABLE FOR TEMPORARY CONSTRUCTIONS BECAUSE THEY ARE AS EASY TO DISMANTLE AS TO ESTABLISH. 1 SQ.KM. OF AN AREA CAN BE BROUGHT DOWN IN 6 HOURS. AND ESTABLISH IN LESS THAN 10 HOURS. THE 4 HOURS DIFFERENCE IS DUE TO ESTABLISHMENT OF PEGS ETC.
:- IT IS NOT EXPENSIVE WHERE IT IS USED FOR SHIFTING STRUCTURES. FOR PERMANENT STRUCTURES, IT IS VERY EXPENSIVE. OTHERWISE THE COST PER SQURE FOOT OF AIR SUPPORTED STRUCTURES IS AMONG THE LOWEST FOR LARGE SPAN ROOFS. :- GIVES GOOD NATURAL LIGHT AS TRANSLUCENT/TRANSPARENT PLASTIC SHEETS ARE USED TO COVER AIR BAGS.WE CAN EVEN BRING THE WHOLE SUN INSIDE. THERE IS A LOT OF FLEXIBILITY IN GETTING SUN LIGHT(50%-80%).
CLASSIFICATION OF PNEUMATIC STRUCTURES: PNEUMATIC STRUCTURES ARE FURTTHER SUBDIVIDED BASED ON : TYPE OF DIFFERENTIAL PRESSURE
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DEGREE OF DIFFRENTIAL PRESSURE
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TYPE OF SURFACE CURVATURE
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PROPORTIONS
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TYPES OF PNEUMATIC STRUCTURES:IT CONSIST OF A SINGLE MEMBRANE(ENCLOSING A FUNCTIONALLY USEFUL SPACE) WHICH IS SUPPORTED BY A SMALL INTERNAL PRESSURE DIFFERENCE.THE INTERNALVOLUME OF A BUILDING AIR IS CONSIQUENTLY AT A PRESSURE HIGHER THAN ATMOSPHERIC. THE AIR SUPPORTED STRUCTURE USES A LOW POSITIVE PRESSURE TO SUPPORT A MEMBRANE OVER A GIVEN AREA. AIR MUST BE SUPPLIED CONTANTLY BECAUSE OF THE CONTINOUS LEAKAGE, PRIMARILY THROUGH THE BUILDINGS USED MOST OFTEN BECAUSE OF: . THEIR RELATIVELY LOW COST . THEIR SIMPLICITY OF DESIGN AND FABRICATION
IT IS SUPPORTED BY PRESSURIZED AIR CONTAINED WITHIN INFLATED BUILDING ELEMENT. THE INTERNAL VOLUME OF BUILDING AIR REMAINS AT ATMOSPHERIC PRESSURE. THE PRESSURIZED AIR IN THE PILLOW SERVES ONLY TO STABLIZING THE LOAD CARRYING MEMBRANE . THE COVERED SPACE IS NOT PRESSURIZED . ADVANTAGES OF AIR- INFLATED / AIR FRAME STRUTURE :. THE ABILITY FOR SELF SUPPORT . THE POTENTIAL TO SUPPORT AN ATTACHED STRUCTURE
1. CLASSIFICATION TYPE OF DIFFRENTIAL OF PNEUMATIC PRESSURE:-. STRUCTURES:a)PNEUMATIC PNEUMATICSTRUCTURES STRUCTURESCAN USEBE EITHER FURTHER SUBDIVIDED AS:1)TYPE OF DIFFRENTIALOR PRESSURE . 2)DEGREE OF DIFFRENTIAL PRESSURE 3)TYPE b) IN (+) OF PRESSURE SURFACE CURVATURE SYSTEM,THE MEMBRANE 4)PROPORTIONS IS ALWAYS CURVED OUTWARDS, IN NEGATIVE PRESSURE SYSTEMS THE MEMBRANE IS CURVED INWARDS. c) BEING CURVED INWARDS THERE IS A TENDENCY OFWATER LOGGING & SNOW ACCUMULATION . d) MOREOVER,NEGATIVE PRESSURE SYSTEMS REQUIRE HIGH SUPPORTS AT THE EDGE OR IN THE CENTRE WHICH MAKES IT MORE EXPENSIVE.
2. DEGREE OF DIFFERNTIAL PRESSURE:-
LOW PRESSURE SYSTEMS THESE SYSTEMS ARE PROVIDED WITH LOW PRESSURE AIR ;HENCE HAVE TO BE PROVIDED WITH CONTINUOUS SUPPLY OF AIR.EG-AIR SUPPORTED STRUCTURES.
HIGH PRESSURE SYSTEMS USED FOR EASY ERECTION & DISMANTLING ; THE PRESSURE DIFFERENCE IS B/W 2000-7000MM OF WATER PRESSURE (100 TO 1000 TIMES) LOW PRESSURE SYSTEMS.THESE HIGH PRESSURE AIR INFLATED SYSTEMS ARE EITHER HAVING A SINGLE VALVE SYSTEM OR A DOUBLE VALVE SYSTEMS WHICH AVOIDS IT‟S COLLAPSE.
:- THESE STRUCTURES CAN ALSO BE CLASSIFIED ACCORDING TO THE TYPES OF CURVATURE ON THE OUTER SURFACEa) SINGLE CURVED b) DOUBLY CURVED IN THE SAME DIRECTION OR SYNCLASTICS c) DOUBLY CURVED IN OPPOSITE DIRECTION OR ANTICLASTIC 4.
:- ON THE BASIS OF DIFFERENT PROPORTIONS, PNEUMATIC STRUCTURES CAN BE: TWO DIMENSION OF SIMILAR SIZE AND ONE LARGER DIMENSION, EG:“TUBES”,”MASTS”,”COLUMNS”,”TOWERS”. TWO DIMENSIONS OF SIMILAR SIZE AND ONE SMALLER DIMENSION, EG:- “CUSHIONS”,”LENSES”, ”DISCUSS”,”MATTRESSES”. THREE DIMENSIONS OF SIMILAR SIZE, EG:- “BALOONS”,”BALLS”,”SPHERES”, ”BUBBLES •
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MATERIALSS
MATERIALS:PLASTIC FILMS:- THESE ARE PRIMARILY PRODUCED FROM PVC, POLY ETHYLENE, POLYESTER, POLYAMIDE ETC. FABRICS:- THESE MAY BE MADE OF GLASS FIBRES OR SYNTHETIC FIBRES WHICH ARE COATED IN A PVC, POLYESTER OR POLYURETHENE FILM. RUBBER MEMBRANE:- THEY ARE THE LIGHTEST AND MOST FLEXIBLE. METAL FOILS:- THEY POSSESS A VERY HIGH GAS DIFFUSION RESISTANCE AND HIGH TENSILE STRENGTH . ONE OF THE MAJOR PROBLEMS IN THE USE OF METAL FOILS IS IN NEED TO PRODUCE VERY EXACT CUTTING PATTERNS.
:. EXAMPLES ARE:WOVEN FABRICS:- THEY HAVE TWO MAIN DIRECTION OF WEAVE. THEY CAN BE MADE OF:. ORGANIC FIBRES EG:- WOOL,COTTON OR SILK. . MINERAL FIBRES EG:- GLASS FIBRES. . METAL FIBRES EG:- THIN STEEL WIRES. . SYNTHETIC FIBRES EG:- POLYAMIDE, POLYESTER AND POLYVINYLE.
LIGHT WEIGHT THE POSSIBILITY OF COVERING LARGE SPANS WITHOUT INTERNAL SUPPORTS, COMPLETE PREFABRICATION RAPID ASSEMBLY PORTABILITY TRANSPARENCY TO LIGHT AND RADIO WAVES LOW COST • •
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NEED FOR CONTINUOUS MAINTENANCE OF EXCESS PRESSURE IN THE ENVELOPE THE RELATIVELY SHORT SERVICE LIFE THE POOR FIRE RESISTANCE AND ACOUSTIC INSULATION. •
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THE USE OF PNEUMATIC STRUCTURES IS EXPEDIENT FOR PERMANENT AND TEMPORARY BUILDINGS FOR A VARIETY OF PURPOSES (PRODUCTION AND STORAGE AREAS, AS WELL AS HALLS FOR PERFORMANCES, SPORTS, TRADE, OR EXHIBITIONS), MOBILE BUILDINGS (MAINTENANCE STATIONS, MEDICAL AID STATIONS, CLUBHOUSES, AND LIBRARIES), TRANSPORTATION AND HYDRO-ENGINEERING STRUCTURES (BRIDGES, DAMS, AND GATES), AND AUXILIARY FACILITIES IN
