Understanding Forces in Solid Structure Surface Structure (Core Studies)

PROJECT 2: UNDERSTANDING FORCES IN SOLID STRUCTURE SURFACE STRUCTURE BUILDING CONSTRUCTION 2 [ARC 2513] BACHELOR OF SCIENCE (HONS) IN ARCHITECTURE SEM 3/AUG 2014 NAME

STUDENT ID

KRISTINE YONG

0311297

TAN MING LONG

0311069

PHANG JUNE EE

0311954

TAN CUI ZHI

0320826

CHEAH EE VON

0308719

LECTURER: MR BRUCE LEE XIA SHENG 1

TABLE OF CONTENTS NO. 1

TITLE INTRODUCTION -

PAGE 2-4

FORM

2

SCHEMATIC DRAWINGS (PLAN)

5

3

SCHEMATIC DRAWINGS (SECTION & ELEVATION)

6

4

EXTERNAL BRACING -

5

DIAGRID NODE

FAÇADE -

7-9

10 - 11

AIR LATERAL LOADING

6

CORE STRUCTURE

12 - 13

7

FLOOR DESIGN

14 - 15

8

DOME -

9 10

FLOOR FRAMING 16 - 18

PROCESS METHOD

MODELLING PROCESS BIBLIOGRAPHY

19 - 20 21 2

INTRODUCTION           

LOCATION: LONDON, ENGLAND LATITUDE/LONGITUDE: N51.54°/W0.3° ANNUAL PRECIPITATION: ~52" PER YEAR BUILDING TYPE: COMMERCIAL HIGH-RISE STATISTICS: RENTABLE SPACE 252,025 SQ. FT. ESTIMATED ACTUAL AREA ~500,000 SQ. FT. FLOORS: 40 FLOORS HEIGHT: 179.8 METERS COMPLETION DATE: SEPTEMBER 2003 CLIENT: SWISS RE REINSURANCE COMPANY DESIGN TEAM: FOSTER AND PARTNERS

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30 ST MARY AXE IS LONDON‟S FIRST ECOLOGICAL TALL BUILDING. IT IS THE HEADQUARTERS FOR SWISS RE. THE 40 STOREYS HIGH BUILDING HOUSES 46,400 SQUARE METRES NET OF OFFICE SPACE WITH AN ARCADE OF SHOPS & CAFES ACCESSED FROM A NEWLY CREATED PIAZZA. THE SUMMIT IS A CLUB ROOM WITH AN AMAZING 360DEGREE PANORAMA VIEW ACROSS HE CAPITAL.

FORM

VASARI DIAGRAM

THE PROFILE HELPS DEFLECT WIND COMPARED TO A RECTILINEAR TOWER OF SIMILAR SIZE. A COMFORTABLE ENVIRONMENT IS MAINTAINED AT GROUND LEVEL, CREATING EXTERNAL PRESSURE DIFFERENTIALS TO CREATE A SPECIAL SYSTEM OF NATURAL VENTILATION.

FORM SKETCHING

BASED ON A RADICAL APPROACH, THE BUILDING‟S PROFILE WIDENS & TAPERS TOWARDS ITS APEX AS IT RISES. THE DISTINGUISHING FORM RESPONDS TO THE RESTRAINTS OF THE SITE: THE BUILDING LOOKS MORE SLENDER THAN A RECTANGULAR BLOCK OF THE SAME SIZE AND THE SLIMMING OF ITS PROFILE TOWARDS THE BASE MAXIMISES THE PUBLIC REALM AT STREET LEVEL.

VOLATILE WINDS ARE REDUCED AT PEDESTRIAN LEVEL. AIR FLOWS SMOOTHLY THROUGHOUT THE AREA RESULTING IN LOWER HEAT LOSS OVER SURFACE OF BUILDING. THE LOW PRESSURE SYSTEM ENABLES LARGE LIGHT WELLS TO BE BUILT AT IMPOSSIBLE HEIGHTS. DUE TO THE REASON THE BUILDING DEPENDS ON OFFICE QUIPMENT AND OCCUPANTS FOR HEAT GAIN, THE DESIGN TEAM PREDICTED THAT THE BUILDING WOULD BE NATURALLY VENTILATED 40% OF THE YEAR. 4

SCHEMATIC DRAWINGS [PLAN OF SIGNIFICANT FLOORS, n.t.s.]

40TH FLOOR

21ST FLOOR

39TH FLOOR

6TH FLOOR

33TH FLOOR

GROUND FLOOR

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SCHEMATIC DRAWINGS [n.t.s.]

SECTION

ELEVATION

6

EXTERNAL BRACING

DIAGRID STRUCTURES WERE CHOSEN COMPARED TO CONVENTIONAL EXTERIOR-BRACED FRAME STRUCTURES TO ELIMINATE CONVENTIONAL VERTICAL COLUMNS. THIS IS POSSIBLE BECAUSE THE DIAGONAL MEMBERS IN DIAGRID STRUCTURAL SYSTEMS CAN CARRY GRAVITY LOADS AS WELL AS LATERAL FORCES DUE TO THEIR TRIANGULATED ARRANGEMENT IN A DISTRIBUTIVE AND EVEN MANNER. DIAGRID STRUCTURES CAN ALSO MINIMIZE SHEAR DEFORMATION MORE EFFECTIVELY THAN CONVENTIONAL FRAMED TUBULAR STRUCTURES WITHOUT DIAGONALS. THIS IS BECAUSE THEY CARRY SHEAR BY AXIAL ACTION OF THE BENDING OF THE VERTICAL COLUMNS AND HORIZONTAL SPANDRELS (MOON, 2005)

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DIAGRID THE DIAGRID IS THE MAIN STRUCTURE OF 30 ST MARY AXE. IT CONSISTS OF TWO MIRRORED A FRAMES MADE OF ALUMINIUM COATED STEEL. THEY ARE TWO STOREYS HIGH AND IS PLACED IN A END-TO END ARRANGEMENT. ONE FULL DIAMOND IS FOUR STOREYS TALL. THE UNUSUAL GEOMETRY OF THE TOWER AND ITS PERIMETER STRUCTURE GIVES RISE TO SIGNIFICANT HORIZONTAL FORCES AT EACH NODE LEVEL, ACTING PREDOMINANTLY IN A RADIAL DIRECTION. THE RESOLUTION OF A VERTICAL FLOOR LOAD INTO A RAKING COLUMN REQUIRES A HORIZONTAL RESTRAINT FORCE. A HORIZONTAL CURVEATURE IS ADDED TO THE DIAGRID IN WHICH THE COLUMNS ARE WRAPPED AROUND THE PLAN FORM ENABLES THE COLUMN LOAD TO CHANGE DIRECTION AT EACH NODE. HENCE, A CYLINDRICAL FORM OF DIAGRID GENERATES AN OUTWARD SPREADING FORCE AT NODE POINTS.

A FRAME SKETCH

TOWER WAS ASSEMBLED IN CONSTRUCTION CYCLES OF TWO STOREYS, WITH ONE CYCLE EVERY TWO WEEKS. DIAGRID SKELETON STRUCTURE

CLOSE UP OF A FRAME

CONSTRUCTION PROCESS

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NODE CONNECTOR DETAILS

DOME

DETAILS LOAD DISTRIBUTION

THE PRODUCED NODE IS PREFABRICATED IN FACTORY. THE HEART CONSISTS OF A SOLID BLOCK OF STEEL OF 240 BY 140MM.

SCHEMATIC REPRESENTATION OF THE PERIMETER DIAGRID STRUCTURE SHOWING RIGID NODE CONNECTIONS AT INTERSECTING MEMBERS

THERE IS A SPECIAL CONNECTOR THAT TRANSFERS LOADS, BOTH VERTICALLY AND HORIZONTALLY AT THE „NODES‟ WHICH ARE RIGID MONOLITHIC AND WELDED TOGETHER.THE LOCAL GEOMETRY OF THE CONNECTION VARIES AT EACH FLOOR, DUE TO THE DIFFERING FLOOR DIAMETERS. THREE INTERSECTING PLANES RELEVANT TO A NODE, AS OPPOSED TO SIX INDIVIDUAL ELEMENT ORIENTATIONS IS TAKEN INTO CONSIDERATION. ONE PLANE IS DEFINED BY AXES OF HORIZONTAL LOOPS; ONE IS COMMON TO UPPER COLUMNS AND ONE TO LOWER COLUMNS. PRINCIPAL COMPRESSION LOADS ARE TRANSMITTED THROUGH MILLED END BEARING SURFACES, AND TENSION THROUGH BOLTED SPLICES (VICTORBUYCK, 2006)

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FACADE THE FAÇADE DESIGN WITH ADVANCE GLAZING TECHNOLOGIES, VENTILATED CAVITIES AND BLINDS, PROVIDES UP TO 85% SOLAR PROTECTION. IT‟S CONSTRUCTED ON A DIAGRID STRUCTURE AND MADE OF 5,500 GLASS PANELS. THE WINDOWS AND BLINDS ARE COMPUTER CONTROLLED. THE SOLAR BLINDS ARE TO RECLAIM OR REJECT HEAT FROM ENTERING THE BUILDING. THE AIR CONDITIONING SYSTEM IS INCREASED WITH THE ASSISTANCE OF NATURAL VENTILATION THROUGH THE WINDOWS IN THE LIGHT WELLS OPENING AUTOMATICALLY. THIS SYSTEM ALLOWS THE BUILDING TO SAVE ENERGY FOR UP TO 40% OF THE YEAR. THE ELEMENTS OF THE FAÇADE CONSIST OF: - OPERABLE GLASS SCREEN - PERFORATED ALUMINUM LOUVERS (INTERNAL SUNSCREEN) - A COLUMN CASING OF ALUMINUM - FAÇADE FRAME OF EXTRUDED ALUMINUM

CONSTRUCTION OF FACADE

DIAGRAM SHOWING OPENED WINDOW CONTROLLED BY COMPUTER.

FAÇADE OF ST MARY AXE

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AIR LATERAL LOADING

STRUCTURAL DIAGRID REINFORCES THE CENTRIFUGAL SPIRAL AFFECT OF THE FORM

SPIRALING INTERIOR AIR SHAFTS ARE USED FOR STACK VENTILATION OF THE TOWER

THESE LOADS ARE ALL ABSORBED THROUGH THE GLASS FAÇADE AND EVENTUALLY TRANSFERRED TO THE DIAGRID. THE PRESSURIZED AIR FROM THE WIND PASSES INTO THE BUILDING THROUGH A NATURAL VENTILATION SYSTEM, WHICH IS INCORPORATED THROUGH A DOUBLE SKIN.

CONSTRUCTION OF FACADE

DIAGONAL AREAS OF DARK GLAZING FOR THE AIR SHAFTS VERSUS CLEAR GLAZING FOR OFFICE SPACES REINFORCES THE SPIRAL AFFECT

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CORE STRUCTURE 30 ST MARY AXE IS A HIGH RISE BUILDING WITH 40 STOREYS REACHING AT A HEIGHT OF 18 METER. (MUNRO, 2014, PAGE 36). AT SUCH GREAT HEIGHT, THE RISK OF THE BUILDING TOPPLING OVER WAS THE BIGGEST PROBLEM FACED BY THE ARCHITECTS AND ENGINEERS. TO KEEP THE STRUCTURE UPRIGHT, THIS MULTIPLE COMPLEX BUILDING HAS A CORE STRUCTURE WHICH IS CONSTANT IN SIZE. THIS CORE PRIMARY RESISTS THE VERTICAL GRAVITY LOAD AND SECONDARY RESISTS THE LATERAL LOAD. IN THE CASE WHERE VERTICAL ELEMENTS MAY DESIGNED TO WITHSTAND ONLY GRAVITY FORCE OR ONLY LATERAL FORCE, NEVETHERLESS MOST WERE DESIGNED TO RESIST BOTH. GRAVITY LOADS ARE CONSTANT IN MAGNITUDES WITH AN APPROXIMATE VALUE OF 9.81 M/S2, AND FIXED IN DIRECTION THAT ACT PERMANENTLY ON THE BUILDING. THE CENTRAL CORE STRUCTURE IS A GRAVITY FORCE-RESISTING SYSTEM TRANSFERRING BOTH LIVE AND DEAD LOADS TO THE GROUND. THE ABOVE ILLUSTRATION SHOWS THE VERTICAL GRAVITY FORCE ACTING ON THE COMPOSITE STRUCTURE.

THE RIGHT SKETCH DIAGRAMS A VERTICAL BUILDING ELEMENT UNDER GRAVITY LOAD.

THE RIGHT SKETCH DIAGRAMS A VERTICAL BUILDING ELEMENT UNDER LATERAL LOAD.

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CORE STRUCTURE THE SKELETAL CONSTRUCTION OF THE CENTRAL CORE STRUCTURE IS IMPERATIVE IN UPHOLDING 30 ST MARY AXES. EACH MEMBER OF BEAMS AND COLUMNS WORK TOGETHER TO RESIST THE UNBALANCED FORCES BY PREVENTING SPLAY, COMBATING TORSION, AND INCREASING STIFFNESS TO PROVIDE STABILITY AND RIGIDITY TO THE BUILDING.

THE ABOVE ILLUSTRATION SHOWS THE SKELETAL CONSTRUCTION OF THE STRONGHOLD BUILDING ELEMENTS.

THE LEFT SKETCH DIAGRAMS A HIGH RISE MOMENT FRAME UNDER GRAVITY LOAD.

THE RIGHT SKETCH DIAGRAMS A MOMENT FRAME UNDER GRAVITY LOAD.

THE CORE STRUCTURE IS A RESULT OF MOMENT FRAMES ARRANGED IN A CIRCULAR AND UPWARD POSITION. MOMENT FRAMES ARE DESIGNED TO EFFECTIVELY RESIST GRAVITY AND LATERAL LOAD IN BENDING AND COMPRESSION SITUATION. THEY ARE DERIVED FROM A MUTUAL INTERACTION BETWEEN MOMENT RESISTING BEAM TO COLUMN CONNECTIONS.

THE RIGHT SKETCH DIAGRAMS A MOMENT FRAME UNDER LATERAL LOAD.

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FLOOR DESIGN THIS CIRCULAR PLAN IS THE KEY FEATURE OF THE VENTILATION STRATEGY AS IT IS ROTATED ON EACH FLOOR BY 5 DEGREE TO CREATE SIX SPIRALLING ATRIUMS. THESE ATRIUMS, ENCHANCED BY THE PRESSURE VARIATION, ACT AS THE „LUNGS‟ OF THE BUILDING, PROVIDING NATURAL VENTILATION WITH AIR ENTERING THROUGH MONITORED OPENING WINDOWS WHERE THE POSITIVE OCCURS. THIS SYSTEM REDUCES THE BUILDING‟S RELIANCE ON AIR CONDITIONING AND TOGETHER WITH OTHER SUSTAINABLE MEASURES, MEANS THAT IT USES ONLY HALF THE ENERGY CONSUMED BY A CONVENTIONAL AIR-CONDITIONED OFFICE TOWER.

MONITORED OPENING WINDOWS

SPIRALLING VOID CREATED FROM ATRIUMS OF EVERY FLOORS

DEVELOPMENT OF FLOOR DESIGN FROM A RECTANGLE INTO A CIRCULAR PLAN

SPIRALLING ATRIUMS / AIR SHAFTS ARE USED FOR STACK VENTILATION OF THE TOWER

SIX ATRIUMS OF THE FLOOR

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FLOOR FRAMING THE CIRCULAR FLOOR PLATES ARE FRAMED BETWEEN THE CORE AND PERIMETER STRUCTURE USING RADIAL BEAMS ON 10 DEGREE CENTRELINES. THIS LEADS TO A RANGE OF SPANS FOR THE COMPOSITE FLOOR SLAB OF UP TO 4.75M BETWEEN BEAMS AT THE PERIMETER ON THE LARGEST FLOORS, 17TH FLOOR. THE OVERALL SLAB THICKNESS IS 160MM WITH A SIMILAR WEIGHT TO THE MORE CONVENTIONAL 130MM, AND INCREASED RIB STIFFNESS THAT IMPROVED OVERALL FLOOR PLATE VIBRATION DYNAMICS. THE BEAM DEPTH IS THE MOST CRITICAL IN THE PRIMARY SERVICES DISTRIBUTION ZONE AROUND THE CORE, WHILE THERE IS A LESS CRITICAL FIT AT MID-SPAN. THIS ENABLES THE BEAMS TO BE SPECIFIED WITHOUT PRECAMBER, WHEREAS MAINTAINING SUFFICIENT CLEARANCES FOR SERVICES. THE BEAM SPANS WITHIN THE CORES ARE MUCH REDUCED, ALLOWING THE HORIZONTAL SEPARATION OF STRUCTURAL AND SERVICES ZONES.

BEAM CONNETTING CORE AND PERIMETER STRUCTURE

SECTION OF FLOOR STRUCTURE

FLOOR PLATE FRAMED BETWEEN THE CORE AND PERIMETER STRUCTURE

STRUCTURAL PLAN NEAR MID-HEIGHT OF BUILDING (SHOWING ARRANGEMENT OF CLEAR-SPAN RADIAL FLOOR BEAMS ALIGNING WITH PERIMETER COLUMN POSITIONS AND LIGHT WELL EDGES)

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DOME

THE TOPMOST OF GHERKINS TOWER IS A PANORAMIC DOME, WHICH IS ALSO KNOWN AS THE “LENS”. IT PROVIDES A 360 DEGREE VIEWS OVER LONDON. THESE LEVELS ARE ENCLOSED WITH A STEEL AND GLASS DOME STRUCTURE OF 30M DIAMETER, RISING 22M FROM THE SUPPORT ON THE TOP OF THE PERIMETER DIAGRID. THE STEELWORK OF THE DOME IS A FULLY WELDED LATTICE OF INTERSECTING FABRICATED TRIANGLE PROFILES. THE EFFICIENCY OF THE STRUCTURAL ARRANGEMENT RESULTS THE MINIMAL STEEL ELEMENTS THAT ARE ONLY 110MM X 150MM IN SECTION.

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THE “LENS” STRUCTURE

PROCESS THE ERECTION SEQUENCE PROGRESSED IN TWO-STOREY BANDS WITH THE FOLLOWING STEPS WHICH ARE :-

ERECT CORE STEEL COMPLETE WITH ACCESS STAIRS AND A SMALL AMOUNT OF TEMPORARY BRACING. IN DECK CORE AND ESTABLISH SURVEY POINTS. ERECT DIAGRID COLUMNS AND NODES AS A-FRAMES. ERECT RADIAL BEAMS AND PLUMB A-FRAMES, INSTALL HOOP MEMBERS TO COMPLETE DIAGRID. COMPLETE FLOOR FRAMING AND DECKING, INCLUDING CRANE TIE BRACING WHERE REQUIRED. CONCRETE FLOOR. 17

METHOD THE ERECTION OF THE FULLY WELDED FREE-STANDING DOME LATTICE STEELWORK REQUIRED A DIFFERENT ERECTION APPROACH. OFF-SITE WELDING OF TRANSPORTABLE-SIZED SUB-ASSEMBLIES ENSURED THAT SITE WELDING WAS KEPT TO A MINIMUM. JIGS WERE SET UP ON THE PLAZA SLAB ALLOWING TWO ADJACENT SUBASSEMBLIES TO BE JOINED TOGETHER TO FORM SECTIONS OF THE DOME MEASURING APPROXIMATELY 12M BY 8M WHICH WERE ERECTED ONTO TEMPORARY LOCATING JIGS AT THE TOP OF THE BUILDING. SITE WELDING THE MEMBERS BETWEEN ERECTED SECTIONS COMPLETED THE DOME FRAMING IN TWO LEVEL STAGES, BEFORE THE REMOVAL OF THE TEMPORARY SUPPORTS. THE TOP „SPIDER‟ SECTION WAS ERECTED AFTER THEN. 18

MODELLING PROCESS

CIRCULAR FLOORS AT VARYING DIAMETERS

COLUMNS PREPARATION

COLUMNS OF CORE STRUCTURE

DIAGRIDS PREPARATION

CLADDINGS READY TO BE ATTACHED ON DIAGRIDS

PASTING THE FAÇADE ON THE DIAGRID

SETTING THE DIAGRIDS SURROUNDING THE FLOOR SLABS

ROTATING FLOOR SLABS AT 5 DEGREE EACH FLOOR

DOME IN PROGRESS

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MODELLING PROCESS

IT STARTED WITH PLACING THE VARYING DIAMETER FLOOR SLABS ROTATING AT EVERY 5 DEGRESS ANGLE AS EACH STOREY ASEND TO THE TOP. THIS MAKES THE MODELLING PROCESS AN EXCITING EXPERIENCE; NEVERTHELESS WE DID FACE SOME UNUSUAL CHALLENGES DURING THE MAKING OF THE DIAGRIDS AND CLADDING IT ONTO THE CURVATURE OF THE BUILDING. THE DIAGRIDS ITSELF CONSISTS OF TUBULAR PLASTIC SECTIONS AS REPRESENTATIVE OF THE TUBULAR STEEL SECTIONS IN REAL. EACH PROCEDURE HELPED TO MAKE THE PROCESS OF GOING FROM THE DRAWING TO THE MAKING AS SIMPLE AS POSSIBLE. FINALLY AS WE REACH TO THE TOP OF THE BUILDING, THE DOME LATTICE STEELWORK IS REPRESENTED WITH CUT AND SCALED AEROSOL SPRAYED PAINT MODEL BOARD.

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BIBLIOGRAPHY BUYCK, V. (2014). SWISS RE´S BUILDING, LONDON. VICTORBUYCK. RETRIEVED 17 NOVEMBER 2014, FROM HTTP://WWW.VICTORBUYCK.BE/UPLOADS/PROJECTS/DOC_14.PDF CHRISTIAANSE, K. (2007). 30 ST. MARY AXE. 30 ST MARY AXE.BUILT IDENTITY: SWISS RE‟S CORPORATE ARCHITECTURE (PP. 139-166). BASEL: BIRKHÄUSER. D. MUNRO. (2004). SWISS RE‟S BUILDING, LONDON. PAGE 36 – 43. RETRIEVED 17TH NOVEMBER 2014, FROM HTTP://WWW.VICTORBUYCK.BE/UPLOADS/PROJECTS/DOC_14.PDF FOSTER + PARTNERS. (2014). PROJECTS 30 ST MARY AXE LONDON, UK 1997 – 2004. FOSTER + PARTNERS. RETRIEVED 17TH NOVEMBER 2014, FROM HTTP://WWW.FOSTERANDPARTNERS.COM/PROJECTS/30-ST-MARY-AXE/ F. WHITE. (JUNE 14, 2012). INSPIRATIONAL BUILDINGS NO. 1, THE NATURAL VENTILATION STRATEGY OF 30 ST. MARY AXE. PIDCOCK. RETRIEVED 17TH NOVEMBER 2014, FROM HTTP://WWW.PIDCOCK.COM.AU/BLOG/2012/6/14/INSPIRATIONAL-BUILDINGS-NO1.ASPX GLASS SKYSCRAPER - GHERKIN. (2013, MARCH 1). GLAZETTE. RETRIEVED NOVEMBER 17, 2014, FROM HTTP://WWW.GLAZETTE.COM/GLASS-SKYSCRAPERGHERKIN-412.HTML JOHAR, N. (2014) „LECTURE ONE: LOAD AND FORCES‟. TAYLOR‟S UNIVERSITY MALAYSIA. LARSEN, E., DICKINSON, M., MAYFIELD, A., VINSON, J. AND WEATHERLY, W. (2014). [ONLINE] AVAILABLE AT: HTTPS://ATTACHMENT.FBSBX.COM/FILE_DOWNLOAD.PHP?ID=804423749603695&EID=ASTDRW9FOLNNM1FD1QZI38KXTUMWLL6FXWINQRPVAGWYTUXCL ML8BFO57QZVI4A-5F0&INLINE=1&EXT=1416223093&HASH=ASUB037MXEYZ4MCV [ACCESSED 17 NOV. 2014].

MILLER, J. P., & ANTHOLZ, R. D. (2006, NOVEMBER). STRONG DIAGONALS. CIVIL ENGINEERING, 76, 60.

MOON, K. (2005). DYNAMIC INTERRELATIONSHIP BETWEEN TECHNOLOGY AND ARCHITECTURE IN TALL BUILDINGS. UNPUBLISHED PHD DISSERTATION,MASSACHUSETTS INSTITUTE OF TECHNOLOGY STÅLBYGGNAD, N. (2014). [ONLINE] AVAILABLE AT: HTTP://WWW.VICTORBUYCK.BE/UPLOADS/PROJECTS/DOC_14.PDF [ACCESSED 17 NOV. 2014].

SUTTON YOUNG. 30 ST MARY AXE LONDON. RETRIEVED 17TH NOVEMBER 2014, FROM HTTP://WWW.SUTTONYOUNG.COM/30-STMARY-AXE.HTML Y. BRAZHKINA, M. ARCH, LEED AP. (2011- 2013) GHERKIN – STRUCTURE IN SHAPE OF A DONUT. EVERYONE‟S ARCHITECT. RETRIEVED 17TH NOVEMBER 2014, FROM HTTP://EVERYONESARCHITECT.COM/DIAGRID/DONUT2/

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