Shell structures- advanced building construction

SHELL STRUCTURES

INTRODUCTION

LATTICE AND PORTAL FRAME BUILDINGS CONSIST OF A STRUCTURAL FRAME WHICH SUPPORTS SLAB, ROOF AND WALL

COVERING. THIS FRAME SERVES PURELY AS THE STRUCTURAL SUPPORT AND PROVIDES PROTECTION AGAINST WEATHER.

THE ROOF AND WALL COVERING ADD NOTHING TO THE STRENGTH THE RIGIDITY OF STRUCTURAL FRAME.

A SHELL STRUCTURE IS A THIN CURVED MEMBRANE OR SLAB USUALLY OF REINFORCED CONCRETE THAT FUNCTIONS

BOTH AS STRUCTURE AND COVERING.

THE TERM “SHELL” IS USED TO DESCRIBE THE STRUCTURES WHICH POSSESS STRENGHT AND RIGIDITY DUE TO ITS THIN,

NATURAL AND CURVED FORM SUCH AS SHELL OF EGG, A NUT, HUMAN SKULL, AND SHELL OF TORTISE.

SHELLS OCCURING IN NATURE

SINGLE OR DOUBLE CURVATURE SHELLS

SINGLE CURVATURE SHELL: ARE CURVED ON ONE LINEAR AXIS AND ARE A PART OF A CYLINDER OR CONE IN THE FORM OF

BARREL VAULTS AND CONOID SHELLS.

DOUBLE CURVATURE SHELL: ARE EITHER PART OF A SPHERE, OR A HYPERBOLOID OF REVOLUTION.

THE TERMS SINGLE CURVATURE AND DOUBLE CURVATURE DO NOT PROVIDE A PRECISE GEMOETRIC DISTINCTION

BETWEEN THE FORM OF SHELL BECAUSE A BARREL VAULT IS SINGLE CURVATURE BUT SO IS A DOME.

THE TERMS SINGLE AND DOULBE CURVATURE ARE USED TO DISTINGUISH THE COMPARITIVE RIGIDITY OF THE TWO

FORMS AND COMPLEXITY OF CENTRING NECESSARY TO CONSTRUCT THE SHELL FORM.

BARREL VAULT

CONOID

HYPERBOLOID PARABOLOID

DOME

FORMS OF CURVATURE:

SURFACES OF REVOLUTION ARE GENERATED BY THE

REVOLUTION OF A PLANE CURVE, CALLED THE MERIDIONAL

CURVE,

ABOUT AN AXIS, CALLED THE AXIS OF REVOLUTION.

IN THE SPECIAL CASE OF CYLINDRICAL AND CONICAL

SURFACES, THE MERIDIONAL CURVE CONSISTS OF A LINE

SEGMENT.

E.G. : CYLINDERS, CONES,

SPHERICAL OR ELLIPTICAL DOMES,

HYPERBOLOIDS OF REVOLUTION, TOROIDS.

SURFACES OF REVOLUTION:

FORMS OF CURVATURE:

SURFACES OF TRANSLATION ARE GENERATED BY SLIDING A PLANE CURVE ALONG ANOTHER PLANE CURVE, WHILE

KEEPING THE ORIENTATION OF THE SLIDING CURVE CONSTANT.

THE LATTER CURVE, ON WHICH THE ORIGINAL CURVE SLIDES, IS CALLED THE GENERATOR OF THE SURFACE.

IN THE SPECIAL CASE IN WHICH THE GENERATOR IS A STRAIGHT LINE, THE RESULTING SURFACE IS CALLED A

CYLINDRICAL SURFACE.

SURFACES OF TRANSLATION :

SURFACES OF TRANSLATION WITH RECTANGULAR PLAN:

(A) ELLIPTIC PARABOLOID (B) CYLINDRICAL PARABOLOID (C) HYPERBOLIC PARABOLOID

FORMS OF CURVATURE:

IF TWO PARABOLAS ARE SIMILAR, THE SURFACE BECOMES A SURFACE OF REVOLUTION, CALLED PARABOLOID OF

REVOLUTION.

SURFACES OF TRANSLATION :

FORMS OF CURVATURE:

RULED SURFACES ARE GENERATED BY SLIDING EACH END OF A STRAIGHT LINE ON THEIR OWN GENERATING CURVE.

THESE LINES ARE NOT NECESSARILY AT RIGHT ANGLE TO THE PLANES CONTAINING THE END CURVES.

RULED SURFACES :

COOLING TOWER, GENERATED BY STRAIGHT

LINES GOULD 1988

CONOID, GENERATED BY STRAIGHT LINE TRAVELING ALONG ANOTHER

STRAIGHT LINE AT ONE END AND CURVED LINE AT OTHER END. JOEDICKE

1963

SHELLS

SINGLY CURVED (DEVELOPABLE SHELLS)

DOUBLY CURVED (NON DEVELOPABLE SHELLS)

SURFACES OF REVOLUTION

SURFACES OF TRANSLATION/ RULED SURFACE

CIRCULAR CYLINDER

(BARREL)

CONES

CIRCULAR OR

NON CIRCULAR CYLINDER

CONES

SYNCLASTIC ANTYNCLASTIC



CIRCULAR DOMES

ELLIPSOID OF

REVOLUTION

ELLIPTIC

PARABOLOIDS

PARABOLOIDS OF

REVOLUTION PARABOLOIDS OF

REVOLUTION



HYPERBOLOIDS OF

REVOLUTION OF

ONE SHEET

HYPERBOLIC PARABOLOIDS

CONOIDS

HYPERBOLOIDS OF

REVOLUTION OF

ONE SHEET

FORMS OF CURVATURE:

SURFACES WITH DOUBLE CURVATURE CANNOT BE DEVELOPED, WHILE THOSE WITH SINGLE CURVATURE CAN BE

DEVELOPED.

DEVELOPABLE AND NONDEVELOPABLE SURFACES :

IN OTHER WORDS, SURFACES WITH POSITIVE AND NEGATIVE GAUSSIAN CURVATURE (I.E. SYNCLASTIC AND ANTICLASTIC

SURFACES) CANNOT BE DEVELOPED, WHILE THOSE WITH ZERO GAUSSIAN CURVATURE CAN BE DEVELOPED.

DEVELOPED

(A) POSITIVE GAUSSIAN (B) ZERO GAUSSIAN (C) NEGATIVE GAUSSIAN

TYPES OF GAUSSIAN CURVATURE.

NONDEVELOPED

FORMS OF CURVATURE: DEVELOPABLE SURFACES (SINGLY CURVED) :

DEVELOPABLE SURFACE IS A SURFACE THAT CAN BE UNROLLED ONTO A FLAT PLANE WITHOUT TEARING OR STRETCHING

IT.

IT IS FORMED BY BENDING A FLAT PLANE, THE MOST TYPICAL SHAPE OF A DEVELOPABLE SHELL IS A BARREL, AND A

BARREL SHELL IS CURVED ONLY IN ONE DIRECTION.

BARREL :

ARCH ACTION & BEAM ACTION TOGETHER MAKE A BARREL.

THERE ARE MAINLY TWO TYPES OF BARREL :

- LONG BARRELS , ARCH ACTION IS PROMINENT

- SHORT BARRELS, BEAM ACTION IS PROMINENT

STRUCTURAL BEHAVIOR OF SHORT BARREL SHELLS: THESE SHELLS ARE TYPICALLY SUPPORTED AT THE CORNERS AND CAN BEHAVE IN ONE OR A COMBINATION OF THE FOLLOWING WAYS:

STRUCTURAL BEHAVIOR OF LONG BARREL SHELLS: THESE ARE TYPICALLY SUPPORTED AT THE CORNERS AND BEHAVE STRUCTURALLY AS A LARGE BEAM.

THEY ARE MAINLY CLASSIFIED AS : 1) SYNCLASTIC 2) ANTICLASTIC

SYNCLASTIC SHELLS:

THESE SHELLS ARE DOUBLY CURVED

AND HAVE A SIMILAR CURVATURE IN EACH DIRECTION. E.G. DOMES

A DOME IS A GOOD EXAMPLE OF A SYNCLASTIC SHELL, IT IS DOUBLY CURVED AND CAN BE FORMED BY ROTATING A

CURVED LINE AROUND AN AXIS.

A DOME CAN BE SPLIT UP INTO TWO DIFFERENT DIRECTIONS; VERTICAL SECTIONS SEPARATED BY LONGITUDINAL ARCH

LINES (ALSO CALLED MERIDIANS), AND HORIZONTAL SECTIONS SEPARATED BY HOOPS OR PARALLELS.

STRUCTURAL BEHAVIOR :

SIMILAR TO ARCHES UNDER A UNIFORM LOADING THE DOME IS UNDER COMPRESSION EVERYWHERE, AND THE STRESSES

ACT ALONG THE ARCH AND HOOP LINES.

FORMS OF CURVATURE: NON-DEVELOPABLE SURFACES (DOUBLY CURVED) : E.G., SPHERE OR HYPERBOLIC PARABOLOID.

ANTICLASTIC SHELLS : ARE DOUBLY CURVED BUT EACH OF THE TWO CURVES HAVE

THE OPPOSITE DIRECTION TO THE OTHER. E.G. SADDLE POINTS.

CONOIDS, HYPERBOLIC PARABOLOID AND HYPERBOLOIDS ARE ALL CONSIDERED TO

THE ANTICLASTIC SHELL BECAUSE THEY ARE SADDLED SHAPE WITH DIFFERENT

CURVATURE IN EACH DIRECTION AND STRAIGHT LINES CAN BE DRAWN OF THE

SURFACE.

CONOIDS: FORMED BY MOVING A ONE END OF A STRAIGHT LINE ALONG A CURVED

PATH AND THE OTHER ALONG A STRAIGHT PATH.

HYPERBOLOIDS: FORMED BY ROTATING A STRAIGHT LINE AROUND A VERTICAL AXIS.

FORMS OF CURVATURE: NON-DEVELOPABLE SURFACES (DOUBLY CURVED) :

ANTICLASTIC

CONOID

HYPERBOLOID PARABOLOID

HYPERBOLIC PARABOLOID:

FORMED BY SWEEPING A CONVEX PARABOLA ALONG A CONCAVE

PARABOLA OR BY SWEEPING A STRAIGHT LINE OVER A STRAIGHT PATH AT

ONE END AND ANOTHER STRAIGHT PATH NOT PARALLEL TO THE FIRST.

STRUCTURAL BEHAVIORS:

DEPENDING ON THE SHAPE OF THE SHELL RELATIVE TO THE CURVATURE,

THERE WILL BE DIFFERENT STRESSES.

SHELL ROOFS, HAVE COMPRESSION STRESSES FOLLOWING THE CONVEX

CURVATURE AND THE TENSION STRESSES FOLLOW THE CONCAVE

CURVATURE.

FORMS OF CURVATURE: NON-DEVELOPABLE SURFACES (DOUBLY CURVED) :

FORMS OF CURVATURE:

FIG. (A) REPRESENTS A DOUBLY CURVED SHELL WITH NO AXIS OF SYMMETRY,

SHOWS A SPHERICAL DOME SUPPORTED ON A WALL.

WHENEVER THE SHELLS ARE SUPPORTED VERTICALLY AT THEIR EDGES, A TENSION

TIE IS REQUIRED AROUND THE PERIMETER AT THE INTERSECTION OF THE DOME

AND THE WALL.

HOWEVER, IT IS IMPORTANT TO NOTE THAT THE TIE WILL BE FUNICULAR FOR ANY

SHAPE OF EITHER THE PLAN OR

ELEVATION.

FIG. (B) THE SHELL HAS POSITIVE CURVATURE AND

CONTINUOUS VERTICAL SUPPORT.

TENSION TIE :

FORMS OF CURVATURE:

THE SUPPORT MAY BE A CONTINUOUS WALL OR STIFF BEAMS

BETWEEN ADEQUATELY SPACED COLUMNS. IT IS INTERESTING THAT

THE STRAIGHT PARTS OF THE TIE IN FIG. (C) DO NOT REQUIRE TIES

ACROSS THE BUILDING.

THE THRUSTS ARE TAKEN BY SHEAR FORCES THROUGH THE WIDTH

OF THE SHELL, AND ONLY TENSION FORCES EXIST IN THE TIE.

TENSION TIE :

CYLINDRICAL SHELL COMBINED WITH SPHERICAL SHELL

TYPES OF SHELL STRUCTURES:

THE DISTINGUISHING FEATURE OF THE FOLDED PLATE IS THE EASE IN FORMING PLANE

SURFACES. A FOLDED PLATE MAY BE FORMED FOR ABOUT THE SAME COST AS A

HORIZONTAL SLAB AND HAS MUCH LESS STEEL AND CONCRETE FOR THE SAME SPANS.

THE PRINCIPLE COMPONENTS IN A FOLDED PLATE STRUCTURE CONSIST OF :

1) THE INCLINED PLATES

2) EDGE PLATES WHICH MUST BE USED TO STIFFEN THE WIDE PLATES

3) STIFFENERS TO CARRY THE LOADS TO THE SUPPORTS AND TO HOLD THE PLATES IN LINE

4) COLUMNS TO SUPPORT THE STRUCTURE IN THE AIR.

FOLDED PLATE SHELLS:

FOLDED PLATE TRUSS

TAPERED FOLDED PLATES

CANOPIES

Z SHELL

THREE SEGMENT FOLDED PLATE


BARREL VAULTS ARE PERHAPS THE MOST USEFUL OF THE SHELL STRUCTURES BECAUSE THEY CAN SPAN UPT O 150 FEET

WITH A MINIMUM OF MATERIAL. THEY ARE VERY EFFICIENT STRUCTURES BECAUSE THE USE THE ARCH FORM TO REDUCE

STRESSES AND THICKNESSES IN THE TRANSVERSE DIRECTION.

CYLINDRICAL BARREL VAULTS:

MULTIPLE BARRELS - OUTSIDE STIFFENERS UNSTIFFENED EDGES CORRUGATED CURVES THE LAZY S


A DOME IS A SPACE STRUCTURE COVERING A MORE OR LESS

SQUARE OR CIRCULAR AREA. THE BEST KNOWN EXAMPLE IS

THE DOME OF REVOLUTION, AND IT IS ONE OF THE EARLIEST

OF THE SHELL STRUCTURES. EXCELLENT EXAMPLES ARE STILL

IN EXISTENCE THAT WERE BUILT IN ROMAN TIMES. THEY ARE

FORMED BY A SURFACE GENERATED BY A CURVE OF ANY

FORM REVOLVING ABOUT A VERTICAL LINE. THIS SURFACE

HAS DOUBLE CURVATURE AND THE RESULTING STRUCTURE

IS MUCH STIFFER AND STRONGER THAN A SINGLE CURVED

SURFACE, SUCH AS A CYLINDRICAL SHELL.

DOMES OF REVOLUTION:

SPHERE SEGMENT

HALF SPHERE

DOMES - SQUARE IN PLAN

MOST SUITABLE MATERIAL

THE MATERIAL MOST SUITED FOR CONSTRUCTION OF SHELL STRUCTURE IS CONCRETE BECAUSE IT IS A HIGHLY PLASTIC

MATERIAL WHEN FIRST MIXED WITH WATER THAT CAN TAKE UP ANY SHAPE ON CENTERING OR INSIDE FORMWORK.

SMALL SECTIONS OF REINFORCING BARS CAN READILY BE BENT TO FOLLOW THE CURVATURE OF SHELLS.

ONCE THE CEMENT HAS SET AND THE CONCERETE HAS HARDENED THE R.C.C MEMBRANE OR SLAB ACTS AS A STRONG,

RIGID SHELL WHICH SERVES AS BOTH STRUCTURE AND COVERING TO THE BUILDING.

CENTERING OF SHELLS

CENTERING IS THE TERM USED TO DESCRIBE THE NECESSARY

TEMPORARY SUPPORT ON WHICH THE CURVED R.C.C SHELL

STRUCTURE IS CAST.

THE CENTERING OF A BARREL VAULT, WHICH IS PART OF A

CYLINDER WITH SAME CURVATURE ALONG ITS LENGTH; IS

LESS COMPLEX. THE CENTERING OF CONOID, DOME AND

HYPERBOLOID OF REVOLUTION IS MORE COMPLEX DUE TO

ADDITIONAL LABOUR AND WASTEFUL CUTTING OF

MATERIALS TO FORM SUPPORT FOR SHAPES THAT ARE NOT

OF UNIFORM LINEAR CURVATURE.

THE ATTRACTION OF SHELL STRUCTURES LIES IN THE

ELEGANT SIMPLICITY OF CURVED SHELL FORMS THAT UTILISE

THE NATURAL ATRENGTH AND STIFFNESS OF SHELL FORMS

WITH GREAT ECONOMY IN THE USE OF MATERIALS.

THE DISADVANTAGE OF SHELL STRUCTURE IS THEIR COST.

THE SHELL STRUCTURE IS MORE EXPENSIVE DUE TO

CONSIDERABLE LABOUR REQUIRED TO CONSTRUCT THE

CENTERING ON WHICH THE SHELL IS CAST.

CONSTRUCTION OF R.C.C BARREL VAULT

THE BARREL VAULT IS THE MOST STRAIGHT FORWARD

SINGLE CURVATURE SHELL CONSTRUCTION. IT IS THE PART

OF A CYLINDER OR BARREL WITH SAME CURVATUREALONG

ITS LENGTH.

ANY NUMBER OF CONTINUOUS BARRELS OR CONTINUOUS

SPANS ARE POSSIBLE EXCEPT THAT EVENTUALLY

PROVISION IS MADE FOR THE EXPANSION OF THE JOINTS

IN A LARGE STRUCTURES.

THE BARREL VAULTS ARE USED AS PARKING, MARKET

PLACE, ASSEMBLY HALL ,ETC.

TYPES OF BARREL VAULTS

1. SHORT SPAN BARREL VAULTS

2. LONG SPAN BARREL VAULTS

CONSTRUCTION OF R.C.C BARREL VAULT

SHORT SPAN BARREL VAULT

SHORT SPAN BARREL VAULTS ARE THOSE IN WHICH SPAN IS

SHORTER THAN ITS WIDTH. IT IS USED FOR THE WIDTH OF

THE ARCH RIBS BETWEEN WHICH THE BARREL VAULT SPAN.

LONG SPAN BARREL VAULT

LONG SPAN BARREL VAULTS ARE THOSE IN WHICH SPAN IS

LARGER THAN ITS WIDTH.

STRENGTH OF THE STRUCTURE LIES AT THE RIGHT ANGLES

TO THE CURVATURE TO THAT SPAN IS LONGITUDINAL TO

THE CURVATURE.

USUAL SPAN OF THE LONGITUDINAL BARREL VAULT IS

FROM 12-30 M WITH ITS WIDTH BEING ABOUT 1/2 THE SPAN

AND RISE IS 1/5 OF THE WIDTH.

TO COVER LARGER AREAS MULTIBAY ,MULTI SPAN ROOFS

CAN BE USED WHERE THE ROOF IS EXTENDED ACROSS THE

WIDTH OF THE VAULT AS A MULTIBAY .

CONSTRUCTION OF R.C.C BARREL VAULT:

UNDER LOCAL LOADS THE THIN SHELL OF THE BARREL

VAULT WILL TEND TO DISTORT AND LOSE SHAPE AND EVEN

COLLAPSE IF THE RESULTANT STRESSES WERE MORE. TO

STRENGTHEN THE SHELL AGAINST THIS POSSIBILITY,

STIFFENING BEAMS OR ARCHES ARE CAST INTEGRALLY

WITH THE SHELL.

THE COMMON PRACTICE IS TO PROVIDE A STIFFENING

MEMBER BETWEEN THE COLUMN SUPPORTING THE SHELL.

DOWNSTAND STIFFENING RCC BEAM IS MOST EFFICIENT

BECAUSE OF ITS DEPTH, BUT THIS INTERRUPTS THE LINE OF

SOFFIT OF VAULTS, FOR THIS UPSTAND STIFFENING BEAM

IS USED.

THE DISADVANTAGE OF UPSTAND BEAM IS THAT IT BREAKS

UP THE LINE OF ROOF AND NEED PROTECTIONS AGAINST

WEATHER.

STIFFENING BEAMS AND ARCHES:


DUE TO SELF WEIGHT AND IMPOSED LOAD THE THIN SHELL WILL TEND TO SPREAD AND ITS CURVATURE FLATTEN OUT. TO

RESIST THIS RCC EDGE BEAMS ARE CAST BETWEEN COLUMNS.

EDGE BEAMS MAY BE CAST AS DROPPED BEAMS OR UPSTAND BEAMS OR PARTIALLY AS BOTH. IN HOT CLIMATE THE

DROPPED BEAM IS USED WHEREAS IN TEMPERATE CLIMATE UPSTAND BEAM IS USED TO FORM DRAINAGE CHANNEL FOR

RAIN WATER.

IN MULTI-BAY STRUCTURES, SPREADING OF THE VAULTS IS LARGELY TRANSMITTED TO THE ADJACENT SHELLS, SO DOWN

STAND AND FEATHER VALLEY BEAM IS USED.

EDGE AND VALLEY BEAMS:


THE CHANGE IN TEMPERATURE CAUSES THE

EXPANSION AND CONTRACTION IN CONCRETE

STRUCTURES, WHICH CAUSES THE STRUCTURES TO

DEFORM OR COLLAPSE.

TO LIMIT THIS CONTINUOUS EXPANSION JOINTS ARE

FORMED AT THE INTERVAL OF ABOUT 30M, ALONG THE

SPAN AND ACROSS THE WIDTH OF THE MULTI-BAY AND

MULTI-SPAN BARREL VAULT ROOFS. LONGITUDINAL

EXPANSION JOINTS ARE FORMED IN A UP STAND

VALLEY.

EXPANSION JOINTS:


TOP LIGHT CAN BE PROVIDED BY DECK LIGHT FORMED IN THE CROWN OF VAULT OR BY DOME LIGHT. THE DECK LIGHT

CAN BE CONTINUOUS OR FORMED AS INDIVIDUAL LIGHTS.ROOF LIGHTS ARE FIXED TO AN UPSTAND CURB CAST

INTEGRALLY WITH THE SHELL.

ADVANTAGE OF THE SHELL IS THAT ITS CONCAVE SOFFIT REFELECTS AND HELPS TO DISPERSE LIGHT OVER AREA BELOW.

DISADVANTAGE IS THAT TOP LIGHT MAY CAUSE OVER HEATING AND GLARE.

ROOF LIGHTS:

SHELLS MAY BE COVERED WITH NON-FERROUS SHEET METAL, ASPHALT, BITUMEN FELT, A PLASTIC MEMBRANE OR A

LIQUID RUBBER BASE COATING.

ROOF COVERING:

THE THIN SHELL OFFERS POOR RESISTANCE TO TRANSFER OF HEAT. THE NEED TO ADD SOME FORM OF INSULATING

LINING ADDS CONSIDERABLY TO COST OF SHELL.

THE MOST SATISFACTORY METHOD OF INSULATION IS TO SPREAD A LIGHT WEIGHT SCREED OVER THE SHELL.

DIFFICULTIES OF PROVIDING INSULATION AND MAINTING THE ELEGANCE OF CURVED SHAPE MAKES THESE STRUCTURES

LARGELY UNSUITED TO HEATED BUILDINGS IN TEMPERATE CLIMATE.

ROOF INSULATION:

ADVANTAGES AND DIS-ADVANTAGES OF SHELLS:

1. VERY LIGHT FORM OF CONSTRUCTION. TO SPAN 30.0 M SHELL THICKNESS REQUIRED IS 60MM

2. DEAD LOAD CAN BE REDUCED ECONOMIZING FOUNDATION AND SUPPORTING SYSTEM

3. THEY FURTHER TAKE ADVANTAGE OF THE FACT THAT ARCH SHAPES CAN SPAN LONGER

4. FLAT SHAPES BY CHOOSING CERTAIN ARCHED SHAPES

5. ESTHETICALLY IT LOOKS GOOD OVER OTHER FORMS OF CONSTRUCTION

ADVANTAGES:

1. SHUTTERING PROBLEM

2. GREATER ACCURACY IN FORMWORK IS REQUIRED

3. GOOD LABOUR AND SUPERVISION NECESSARY

4. RISE OF ROOF MAY BE A DISADVANTAGE

DIS-ADVANTAGES:

CASE STUDY- SYDNEY OPERA HOUSE:


THE SYDNEY OPERA HOUSE SPANS UP TO 164 FEET.

THE ARCHES ARE SUPPORTED BY OVER 350KM OF

TENSIONED STEEL CABLE.

THE SHELL THICKNESS GOES FROM 3 TO 4 INCHES.

ALL SHELLS WEIGHT A TOTAL OF 15 TONS.

THIS INVOLVED LAYING THE FOUNDATIONS AND BUILDING A PODIUM 82 FEET (25 M) ABOVE SEA LEVEL. MORE THAN

39,239 CUBIC FEET (30,000 M3) OF ROCK AND SOIL WERE REMOVED BY EXCAVATORS.

THE FOUNDATION WAS BUILT ATOP A LARGE ROCK THAT SAT IN SYDNEY HARBOUR. THE SECOND STAGE SAW THE BUILDING

OF THE SHELLS, THE PODIUM STRUCTURE, THE STAGE TOWER, AND THE NECESSARY MACHINERY.

CABLE BEAMS WERE BUILT AND REINFORCED BY STEEL CABLES TO RELEASE THE STRESS OF THE WEIGHT. THE STRENGTH OF

THE CABLES WAS TESTED BY LOADING ADDITIONAL WEIGHTS. WHEN THE BUILDERS WERE SATISFIED THAT THE CABLES

WOULD SUPPORT, THE BEAMS WERE MADE EXTENDABLE BY OTHER BEAMS.

SYSTEM SPANS AND EFFECTIVE SPANS:


THE "SHELLS" WERE PERCEIVED AS A SERIES OFPARABOLAS SUPPORTED BY PRECAST CONCRETE RIBS. THE FORMWORK FOR

USING IN-SITU CONCRETE WOULD HAVE BEEN PROHIBITIVELY EXPENSIVE, BUT, BECAUSE THERE WAS NO REPETITION IN ANY

OF THE ROOF FORMS, THE CONSTRUCTION OF PRE-CAST CONCRETE FOR EACH INDIVIDUAL SECTION WOULD POSSIBLY HAVE

BEEN EVEN MORE EXPENSIVE.

THE DESIGN TEAM WENT THROUGH AT LEAST 12 ITERATIONS OF THE FORM OF THE SHELLS TRYING TO FIND AN

ECONOMICALLY ACCEPTABLE FORM (INCLUDING SCHEMES WITH PARABOLAS, CIRCULAR RIBS AND ELLIPSOIDS) BEFORE A

WORKABLE SOLUTION WAS COMPLETED. IN MID-1961, THE DESIGN TEAM FOUND A SOLUTION TO THE PROBLEM: THE SHELLS

ALL BEING CREATED AS SECTIONS FROM A SPHERE. THIS SOLUTION ALLOWS ARCHES OF VARYING LENGTH TO BE CAST IN A

COMMON MOULD, AND A NUMBER OF ARCH SEGMENTS OF COMMON LENGTH TO BE PLACED ADJACENT TO ONE ANOTHER,

TO FORM A SPHERICAL SECTION.

SYSTEM SPANS AND EFFECTIVE SPANS:

CASE STUDY- SYDNEY OPERA HOUSE: CONSTRUCTION:


1. SYDNEY OPERA HOUSE STEEL REINFORCING 2. SYDNEY OPERA HOUSE ON COMPLETION OF PODIUM 1

3. SYDNEY OPERA HOUSE ON COMPLETION OF PODIUM 2 4. SYDNEY OPERA HOUSE SHELL RIBS


ACTUAL CLAY, BRICK, AND STONE VENEER GRANITE OR MARBLE CLADDING EXPOSED AGGREGATE FINISH SAND BLASTED FINISH FORM LINER PATTERNS THE SYDNEY OPERA HOUSE USES WHITE GLAZED GRANITE TILES. 1,056,000 TILES WERE USED TO COVER THE MASSIVE STRUCTURE.

FINISHES:

Shell structures- advanced building construction

Education

Transcript of Shell structures- advanced building construction