Structures Seminar

The Gherkin, London

Norman Foster

Client: Swiss Re Project Manager: RWG Associates Architect: Foster and Partners Structural Engineer: Arup Building Services Engineer: Hilson Moran Partnership Cost consultant: Gardiner & TheoboldFire Engineering: Arup Fire

Presented By :Akshay AmanCharu KumariManisha NimeshSharda BhagatVikram Bengani

Disclaimer

This is not an academic paper. This is a case study performed as part of a High Rise Structures

Seminar as part of the B.Arch. Programme at School Of Planning & Architecture.

The authenticity of the data/information cannot be guaranteed with certainty. However, the information is fairly accurate and has been collected from the internet while spatial analysis has

been performed by the authors. The various sources have been cited in the ‘Sources’ page.

This presentation is a condensed version of the author’s learnings and all the information available on the internet.

HISTORYFROM BOMBING OF BALTIC EXCHANGE TO THE BUILDING OF THE GHERKIN

The beginning of the Gherkin's birth starts in 1992 as an explosion rocked the financial district of London. The Provisional IRA detonated an explosive device near the Baltic Exchange and catastrophically injured the building. The building was torn down and city officials decided to put a larger tower in its place.

The Gherkin began as a much larger building that was dubbed the "Millennium Tower" but which failed to materialise. The original design of the building raised fears that it could negatively impact air traffic from Heathrow. There were also concerns that it may interfere with the sight-lines of St. Paul's Dome from certain parts of the city. Once the original design was shot down, Norman Foster created the scaled-down version that now sits at 30 St Mary Axe.

Construction began in 2001 and the Gherkin was finished in December of 2003. It didn't open for the public until almost half of a year later.

In response to Norman Foster's Millennium Tower and 30 St Mary Axe Proposal, the English Heritage supported newer buildings, but perceived threat of tall buildings. SAVE Britain's Heritage also played a heavy opposition role over construction of any new architecture.

With demand for space for new offices, Swiss Re claimed that it should be allowed to build "the Gherkin" on the site, with economic benefit of its jobs, and a huge investment in the UK economy back to mainland Europe.

Second IRA bombing. St. Mary Axe street facade of Baltic exchange was completely blown off. APRIL 1993

Foster started working on the Millennium Tower right after English Heritage accepted demolition of the The Baltic Exchange.(MARCH 1996)London Millennium Tower(400m) planning application. August 1996

Entire project of the Millennium Tower abandoned when it was decided that Swiss Re will buy the site from Kvaerner on condition that planning permission to knock down Baltic exchange was granted. Late 1997

Swiss Re hinted that unless it was allowed to build Norman Foster's distinctive circular tower ('the Gherkin') on the site of the old Baltic Exchange, it would take itself, its jobs and its huge investment in the UK economy back to mainland Europe. Early 1998

First IRA bomb close to The Baltic Exchange10th April 1992

THE GHERKIN: HISTORY IN THE CONSTRUCTION OF THE BUILDING

•Height to top of dome: 179.8 m•Height to highest occupied floor level: 167.1 m•Number of floors above ground: 40•Number of basement levels: single basement across whole site•Largest floor external diameter (lvl 17): 56.15 m•Site area: 0.57 hectares (1.4 acres)•Net accommodations areas:

• Total = 64,470 m²• Office 46,450 m2• Retail 1,400 m2

•Office floor-floor: 4.15 m•Gross superstructure floor area (incl. lightwells): 74,300 m2•Tower Structural Steelwork•Total weight of steel (from Arup Xsteel model): 8,358 tonnes of which:

• 29% is in the diagrid• 24% core columns• 47% beams

•Total number of primary steel pieces: 8 348•Total length: 54.56 km•Diagrid column sizes:

• Ground – level2: 508mm f, 40mm thick• Level 36–38: 273mm f, 12.5mm thick

•Foundations 750mm diameter straight-shafted piles into London Clay•Number of piles: 333•Total length of piles: 9 km•Total design capacity: 117,000 Tonnes•Design Capacity/Weight of Steel = 14tonne Load/tonne of steel•Design Capacity/Built Area =1.814tonne load/sqm•Load on Pile = Average 351 Tonne Load/Pile•Hoop design tension at level 2: 7 116 kN•Perimeter column maximum design load: 15,460 kN•Core column maximum design load: 33,266 kN•Occupancy = 4,000 workers

SITE PLAN

Ground floor and first floor consist of reception and a series of shops at outer edge of the building with the arcade.

Third to sixteenth floor is the office of swiss re insurance company.

There are private dining area at 38-40 floors.

The basement is used for the parking (only two wheelers , no four wheelers are allowed in the parking).

The design provides column-free floor space, light and views, and incorporates many sustainable building design features.

Spiralling light wells allow the maximum amount of sunlight to flood the interiors.

Atria between the radiating fingers of each floor link together vertically to form a series of informal break-out spaces. Each floor rotates 5 degrees from the one below.

INTRODUCTION

6TH FLOOR PLAN

21ST FLOOR PLAN

33RD FLOOR PLAN

39TH FLOOR PLAN

40TH FLOOR PLAN

FRAMING PLANS

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Background of "diagrid" structure

The early era, tall building relied on portal frame and fix

joint to resist lateral and wind load. Latter the structure

build higher, more load and forces have to consider in the

structure. Additional bracing in the form of diagonal placed

in between the structure to take the lateral load. Portal

frames are insufficient in the lateral forces for the tall

building. Diagonal bracing make the structure resist wind forces instead creating stronger frame connection.

When the building built higher, K and X bracing was added

to resist moment from beam to column. This structure was

place internally near the core to reduce the obstructive of

façade design or internal layout.

The idea of exterior diagonal bracing simply used as secondary member to provide rigidity to the building.

The braced tube structure John Hancock Building in Chicago was designed by Fazlur Kahn in, 1968.

Brace tube Structure

Brace Tube Structure

John Hancock Building,

Chicago

Brace Bundle Tube Building

Brace Bundle Tube is creating a perimeter bracing tube

structure to support the tall building. The plan of the

building is divided into large grid and the volume is

reducing back toward the top to reduce wind resistance while providing larger and stronger connection at base.

Brace Bundle Tube Building

DiA-GRiD = DiAgonal + GRiD

free standing structure without internal core.

The presence of this civic

structure has influenced Norman

Foster & Arup explore diagrid

system in the future. The diagrid

structure began appear in

contemporary steel design after

initial example project – The

London GLA, Gherkin Tower (Swiss Re) and Hearts Tower.

Water Tower by Valdamir Shukov

How diagrid works?

Original diagonal bracing member laid over exterior structure as supplementary

support. However, the current diagrid system that used in exterior structures is

primary mean of support.

Diagrid tower is model as vertical cantilever. The size of diagonal grid is defined by the dividing tower height into series of modules.

How diagrid works?

Diagrid “tube” does not have the sufficient strength to achieve stability in the

structure. Ring beam connection to the floor edge can tied diagrid with the floor and

the core.

Normally multiple floors interesting with each long diagonal of the grid, these

intersections will occur at the nodes as well as the several instances along the

diagonal.

When the diagonal bracing extends over several stories, each floor’s edge beam can

frame into the diagonal members providing connection the core to support the floor edge beam.

“diagrid is a series of triangle that combine gravity and

lateral support into one, making the building to be stiff,

efficient, and lighter than a traditional high rise”

Cantor Seinuk from WSP

These diagonals were affected by the width and height ratio.

The base of the building have to designed to resist moment while the top have to

resist the shear force. As a result, the foundation of a diagrid system is more concentrate on a point to reach stability

The diagonal members in diagrid carry shear and moment. The optical angle of

the diagrid will dependent on the building height and module. The expected

optimal angle for diagonal members for diagrid structure will fall in the range of 60° to 70°.

“ a pure steel diagrid tower doesnot require a core for lateral resistance ”

Diagrid nodes

(1) pin node

Not rigid pin connection can be used in the symmetrical structure since the

structure have balance load.

(2) Rigid Node

the needs of rigid nodes to assist the structure to support during the construction

process.

Diagrid Joint

(i) diagrid structure sit external and the envelope or curtain wall will clad on floor structure,

(ii) diagrid structure sit internal and the envelope have to clad on the diagrid.

There are two main joint for the diagrid structure: welding or

bolting. This have to rely on the what appearance require for

the design. for example when the structure to be expose,

welding cans provides better aesthetic value.

In the contrast, if the structure will be expose to external

and cannot be visible, bolt and nut will be the better choice.

Awelding connection is needed if the diagrid structures

decided to architectural exposed it but required more skillful

workers .

Somehow, if the structure are to be clad or concealed like

Hearts Tower, the diagrid can choose to bolted on site for speed erection.

Welding joint for the Swiss Re

Tower interior

The gravity and vertical load from the building will distribute toward the apex of the

diagonal structure. Somehow, it will affected by the height and angle of the

diagonal.

The vertical forces will be divide/disperse into the other diagonal member.

Compression and tension result in the diagonal will transfer into the bottom section.

Vertical Load

the lateral load happened toward the "flange" of the structure receiving directional

wind load. this will result the lateral load into two part; windward and leeward.

As a consequence, these diagonal members receiving two different direction of

force load. It will respond relatively. The structure able to resist both force and achieve equilibrium.

Lateral Load

DEMERITS OF DIAGRIDS:

1) As of yet, the Diagrid Construction techniques are not thoroughly explored.

2) Lack of availability of skilled workers . Construction crews have little or no

experience creating a DiaGrid skyscraper.

3) The DiaGrid can dominate aesthetically, which can be an issue depending upon

design intent.

4) It is hard to design windows that create a regular language from floor to floor.

5) The DiaGrid is heavy-handed if not executed properly.

MERITS OF DIAGRIDS:

1) The Diagrid structures have mostly column free exterior and interior, hence free and

clear, unique floor plans are Possible.

2) The Glass facades and dearth of interior columns allow generous amounts of day lighting

into the structure.

3) The use of Diagrids results in roughly 1/5th reduction in steel as compared to Braced

frame structures.

4) The construction techniques involved are simple, yet they need to be perfect.

5) The Diagrids makes maximum exploitation of the structural Material.

6) The diagrid Structures are aesthetically dominant and expressive.

Diagrid (diagonal + grid) is a design for constructing large buildings with steel that

creates triangular structures with diagonal support beams. It requires less structural

steel than a conventional steel frame.Hearst Tower in New York City, designed by

Sir Norman Foster, reportedly uses 21 percent less steel than a standard design.

The Diagrid also obviates the need for large corner columns and provides a better distribution of load in the case of a compromised building.

The perimeter ‘diagrid’ structure The perimeter steel structural solution was developed specifically for this building in order to address the issues generated by the unusual geometry in a manner that was fully integrated with the architectural concept and generated the maximum benefit for the client.

The final solution was one of a number of approaches that were assessed in detail for overall structural efficiency, internal plannning benefits, buildability, cost and risk. The design avoids large cantilevers and keeps the light-wells free of floor structure by inclining the perimeter columns to follow the helical path of the six-fingered floors up through the building.

A balanced diagrid structure is formed by generating a pattern of intersecting columns spiralling in both directions. The addition of horizontal hoops, which connect the columns at their intersection points and resist the forces arising from the curved shape, means that the perimeter structure is largely independent of the floors.

The hoops also turn the diagrid into a very stiff triangulated shell, which provides excellent stability for the tower. This benefit of the diagrid means that the core does not need to resist wind forces and can be designed as an openplanned steel structure providing adaptable internal space.

Foundation loads are also reduced compared with a building stabilised by the core.

STRUCTURAL ELEVATION

41

DIAGRID SYSTEMINTERLOCKING DETAILS

A-frame • Aluminum coated tube steel • series of two-stories-high, end to end arrangement. • one full diamond is four-stories tall.

There is a special connector that transfers loads, both vertically and horizontally at the “nodes” which are rigid monolithic and welded together.

The diagonals are CHS members, with cross section between 508 x 40 mm at the lowest floors and 273 x 12.5 mm at the top, while the chord members have RHS, 250 x 300 mm with wall thickness of 25mm. The circular central core, which has constant diameter along elevation, does not contribute to the lateral resistance and rigidity, being a simple frame structure.

The elements of the facade.: Openable glass screen.Perforated aluminium louvers (internal sun-screen).A column casing of aluminium.Façade frame of extruded aluminium.

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DIAGRID SYSTEMINTERLOCKING DETAILS

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Finesoils

MSILT

coarse0.02 - 0.06 mm

medium0.006 - 0.02 mm

fine0.002 -0.006 mm

CLAY < 0.002 mm

Month of year

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year

01 02 03 04 05 06 07 08 09 10 11 12 1-12

Dominant Wind dir.

Wind probability>= 4 Beaufort (%) 34 31 35 31 37 28 32 35 27 30 28 33 31

AverageWind speed(kts) 10 9 10 9 10 9 9 9 9 9 9 9 9

Average air temp. (°C) 7 7 9 13 15 19 21 20 18 14 9 7 13

FORM OF THE BUILDING: THE GHERKIN The design for 30 St Mary Axe was actually developed from ideas

that were used in the Climatroffice design by Buckminster Fuller in the 1970s. This building was never constructed, but it was supposed to be a free-form glass skin which allowed the building to have its own microclimate.

It would have been very difficult in the 1970s to design and build such a complex structure. However, thirty years later, Foster was able to use advanced parametric modeling to design 30 St Mary Axe whose final design is very reminiscent of the Climatroffice design

The shape of the tower is influenced by the physical environment of the city. The smooth flow of wind around the building was one of the main considerations.

The variation of the diameter of the plants is significant, it measures 49 meters at the base, 56.5 at its widest, narrowing to 26.5 on the top floor, which is what gives it the appearance of "Rocket" or "cucumber" as the Londoners have been baptized.

The fact that the tower bulges out in the middle, reaching its maximal diameter at the 16th floor, also helps to minimise winds at its slimmer base.

Environmentally, its profile reduces wind deflections compared with a rectilinear tower of similar size, helping to maintain a comfortable environment at ground level, and creates external pressure differentials that are exploited to drive a unique system of natural ventilation

COMPUTER SIMULATION OF WIND FLOW FLOWS AROUND THE BUILDING

SKETCHES SHOWING THE WIND MOVEMENT AROUND THE BUILDING.

THE GHERKIN: FORM OF THE BUILDING

BUILDING USE AND FUNCTIONALITY

At a time 4000 workers can be accommodated.

Net accommodations areas:Office 46,450 m2

Retail 1,400 m

Total weight of steel : 8,358 tonnes of which:

29% is in the diagrid24% core columns47% beamsThe designers and owners of the building also wanted to discourage motor vehicle use by the building’s tenants. The basement of the building provides three times the bicycle space, 118 spaces, than the minimum required [1][13]. The building does not have car parking for visitors or employees, just 5 handicap spaces and 52 motorcycle spaces

The total weight of steel used is approximately 11,000 tones.

DIVERSE OCCUPANTS In the past couple of years, the Gherkin has changed from a

bespoke owner-occupied London headquarters for insurance company Swiss Re, to a prime multi-let office building, with all but one floor occupied.

On the downside, the building is not very spatially efficient. The central lift, services core and six spiralling light wells around the perimeter mean that only 63% of its gross floor area is useful space.

CELLULAR OFFICES FOR LAWYERS The building is extremely popular with law firms, because the

rectangular spaces can take cellular offices Originally, the circular floor plates were conceived of as open-plan spaces, but this was not practical for lawyers, who need to have confidential one-to-one discussions with clients. In addition, the open lightwells allow sound to travel between six floors at a time, which could compromise confidentiality.

SHARED FLOORS The 19th floor is shared by four companies, the smallest of

which is the five-strong Primus Guaranty, which has a tiny dealing floor and three cellular offices in one rectangular finger.

Sharing this floor called for an internal corridor to be wrapped around the central core of the building to reach the lift lobby.

RESTAURANTS AND RECEPTION DOME Tenants make regular and enthusiastic use of the restaurants

and glass dome at the peak of the building to entertain clients. The 65-cover restaurant and five private dining rooms are

reserved for tenants and members of the exclusive London Capital Club. The reception room in the dome can be hired by outsiders.

There are 18 passenger lifts in the building. 378 people can be vertically transported

through the building at speeds up to 6m per second at any time.

In addition, there are goods and firefighter elevators, as well as a car park elevator to the reception from the basement.

Two special shuttle elevators serve the top floors of the building.

KONE Alta™ fulfilled the architects’ requirements for customized elevator cars and signalization. 3 different levels:

Low rise go from lobby to level 12. Medium rise lifts go from lobby to

22 stopping from level 11. High rise lifts go from lobby to 34

stopping from level 22. Shuttle lift goes from level 34 to

level 39.ELEVATORS

IN THE CORE

ELEVATORS

ELEVATORS IN BUILDING

FIRE FIGHTING METHODS:• Swiss Re falls within the guidance of inner London Section 20 requirements for fire

safety.• Every sixth floor , the atria feature gardens which control and purify air movements as

well as dividing the building into fire compartments.• The unusual light well arrangement leads to a fire escape strategy based on a variation

of phased evacuation.• In this case all six floors linked by a set of light wells are evacuated in the case of a fire on

any one of them.• Where only two floors are linked then those two constitute the first phase. So the light

wells are designed following the guidance for simultaneous evacuation, which allows them to be open to the accommodation.

• Because the light well base floors are protected by sprinklers on the overhanging soffits above, they can be used as office space too.

• A system of smoke curtains form smoke reservoirs in the light wells, and others delay the transport of smoke from accommodation into the light wells.

• Natural ventilation is used for smoke clearance for the light wells and the accommodation.• The building is sprinkle red, including arrays of window sprinklers on part of the façade of levels 2 and 3, to protect a glazed opening in the

compartment floor of level 4, directly above.• However sprinklers have not been fitted in the 12m high domed space that forms the very top of the building.• The Tower has two firefighting shafts with dedicated lifts.• The use of dedicated smoke detectors in each lobby which cause the vent to open in that lobby, as well as at the top of the smoke shaft and the

top of the stair.• During a fire temperatures can be such that the window glazing may break and thus allow cool air to enter and hot gas to escape.• Alternatively, temperatures may be such that the fire has not engulfed a large area and is not severe enough to actually break the glass.• In both cases the temperature reached in the compartment and the duration of a fire is dependent on the amount of ventilation, and it is

assumed that sprinkler activation has not prevented the fire from growing.

FIRE FIGHTING IN THE BUILDING

The spiral lightwell arrangement allows for a fire escape strategy based on a variation of phased evacuation. The building is divided into fire safety zones at every sixth and second floor . this allows for the evacuation of one area at a time as opposed to a whole building at once.

Installation of over smoke curtain barriers. Concealed within the ceiling voids of each of the 39 floors, the Smoke Stop™ smoke curtain barriers were developed to deploy in the event of fire, channelling smoke away from occupant and out of the building. This effective strategy for containing and channelling smoke would ensure that Gherkin’s 41 floors were protected from filling with smoke and provide occupants with a safe means of escape. THE SYSTEM OF SMOKE CURTAIN FORMS THE SMOKE RESERVOIR IN THE LIGHTWELL. NATURAL VENTILATION IS USED FOR THE SMOKE CLEARANCE FROM THE LIGHTWELL.

The smoke containment curtain is automatically lowered by a control signal to a desired height, or the entire opening is closed, thus closing can be programmed for two phases.Suitable for the fire-proof fire closing of horizontal and vertical surfaces.

Appearance: The frame structure and the top box is normally galvanized, powder coated in any desired RAL colour. Can be mounted also above suspended ceilings.

Applications: factories, warehouses, shopping centres, buildings with lobby and atria

VERTICAL SMOKE CURTAIN BARRIERS IN THE GHERKIN

WORKING OF THE SMOKE CURTAIN BARRIER

DESIGN AND CONSTRUCTION

The Gherkin is essentially an elongated, curved, shaft with a rounded end that is reminiscent of a stretched egg. It is covered uniformly around the outside with glass panels and is rounded off at the corners. It has a lens-like dome at the top that serves as a type of observation deck.

The design of the Gherkin is heavily steeped in energy efficiency and there are a number of building features that enhance its efficiency.

There were open shafts built in between each floor that act as ventilation for the building and they require no energy for use.

The shafts pull warm air out of the building during the summer and use passive heat from the sun to bring heat into the building during the winter. These open shafts also allow available sunlight to penetrate deep into the building to cut down on light costs. It has been said that 30 St. Mary Axe uses only half of the energy that a similarly-sized tower would use.

Architectural style21st century contemporary iconic design

sustainable design features:• maximising natural daylight and ventilation; • minimising heating and cooling through a ventilated double-skin façade.

Windows open when the external temperature is between 20 degrees Celsius to 26 degrees Celsius and wind speed is less the 10 mph.

VENTILATION: AIR MOVEMENT THROUGH THE LIGHTWELL

On each floor, a series of interstices with 6 pipes made of natural ventilation system, functioning as a double glazing.

Pipes used for cooling in the summer, drawing warm air from the building, and for heating in winter. They also allow for easier entry of light, with a consequent reduction in the cost of lighting.

The systematic internal microclimate and solutions for energy savings have led to a 50% reduction in energy consumption in any case necessary for a building of this size.

The façade consists of two layers of glass (the outer one double-glazed) enclosing a ventilated cavity with computer-controlled blinds. A system of weather sensors on the outside of the building monitors the temperature, wind speed and level of sunlight, closing blinds and opening window panels as necessary.

The building's shape maximises the use of natural daylight, reducing the need for artificial lighting and providing impressive long-distance views even from deep inside the building

SUSTAINABLITY : THE GHERKIN

The tower is aerodynamically designed to reduce wind load on the structure, whilst the lower part tapers so that wind wraps around the tower.

The six fingers of accommodation on each floor, configured with light wells in between, maximize daylight penetration.

The façade design with advance glazing technologies, ventilated cavities and blinds , provides up to 85% solar protection.

Gas is the main fuel used hence it will only generate half the carbon emission.

Overall energy serving is up to 50%.

The ventilation system reduces conventional air conditioning use due to the aerodynamic shape of the building, which creates air pressure differentials in the double skin and moves air up the building and across offices, as seen in the computer generated ventilation models to the left.

Additionally, lights are on level and motion sensors, reducing unnecessary lighting. All of this helps to reduce the building’s heating and cooling loads and its total energy needs. Within the double skin façade are blinds that can intercept solar radiation, at a 15% solar transmission rate, and the building can then reclaim heat from the solar radiation or reject it depending on the cooling or heating needs of the building

The glass panels in the atriums are also tinted to reduce glare and solar gain

THE SERVICE CORE THE ELEVATORS- 18

PASSENGER LIFTS

THE OFFICE AREA

Core area at centre

This building has a core 9 meters wide and 36 meters long split into five separate sections to provide additional strength

THE CORE

The core takes a portion of the vertical gravity loads and is a secondary structure to the diagrid.

The core acts as a tie back to the hoop structure preventing splay. The structure system of the core is rigid using moment frames.

Provides rigidity

Resists torsion

Increases stiffness

• 35 km of steel, 10 thousand tons were used to build the Swiss Re• 24,000 square meters of glass were used for the exterior of the

building, equivalent to five football fields.• The building was designed to use recycled or recyclable materials

whenever possible

MATERIALS

• The glazing to the office areas consist of a double –glazed outer and a single –glazed inner screen.

• Sandwiched in between is the ventilated cavity which reduces heating and cooling requirements.

• The solar-control blinds intercept solar gain before it enters the office environment.

• The façade is clad with double-paned glass that is filled with argon.

The elements of the facade.• Openable glass screen.• Perforated aluminium louvers (internal sun-screen).• A column casing of aluminium.• Façade frame of extruded aluminium.

Distance between each floor:4200mmEach closed steel frame height: 16800mmEach glass height: 4200mmOther than one curved , other glass are all flat.

Gherkin London. Windows open on the outer skin to allow air to enter the cavity between the inner and outer skin.

SITE TEMPERATURETemperature range:• 22 degrees in December• 94 degrees in June

The change in temperature effects the expansion of the steel members.

TOWER STRUCTURAL STEEL WORK

Total weight of steel: 8,358 ton of which:• 29% is in the diagrid• 24% core columns• 47% beams

Steel in foundation:• 750mm diameter straight-shafted piles into London clay• Number of piles: 333• Total length of piles: 9km• Total design capacity: 117,000 tonnes

Because of site restrictions and in order to create a monolithic foundation, all piles and pile caps were poured in one day.

The heart consists of a solid block of steel of 240 by 140 mm.

• Despite its curved shape, there is actually only one piece of curved glass – the lens at the top of the building which is 2.4m in diameter and weighs 250kg.

• The glass dome at the top of the building provides 360 degree views of London

Façade material:

7,429 glass panes for external skin(recycled glass) made from intersecting tubular steel sections which give vertical support to the floors, rendering them column free. The grid is highly resistant to wind loading and weighs 2,500

EXTERNAL CLADDING SYSTEM

OVERVIEW OF THE FAÇADE:

The building’s exterior cladding systems consists of full glazed, double-skinned façade comprising approximately of 5,500 flat triangular and diamond shaped glass panels. These metal and glass prefabricated panels are fixed to the diagrid.

• The smooth flow of wind around the building was one of the main considerations.

• Minimum impact on the local wind environment.• The tower is aerodynamically designed to reduce

wind load on the structure, whilst the lower part tapers so that wind wraps around the tower.

AIR LATERAL LOADING

• 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.

An aerodynamic form, reducing effects of wind

WIND

SHAPE

Wind load

The overall cylindrical shape allows for the wind to move around the building.

How does this shape effect the horizontal wind loads?• Decreased buffeting• Reduced vibrations• Diminished fluttering

CONNECTIONS

Diagrid• There is a special connector that transfers

loads, both vertically and horizontally at the “nodes” which are rigid monolithic and welded together.

• Rigid node connections at intersecting members.

Core• Rigid connections of steel beams and

columns.

Ventilation for the entire building is heavily dependent on the six shafts that span the entire building. The natural ventilation and air circulation that occurs within these shafts supplements the air conditioning in the building for about 40% of the year

NATURAL VENTILATION AND LIGHTING SYSTEM

Differing air pressures and double skin façade allow for natural ventilation•Six spiralling light wells allow daylight to flood down onto the floors•Windows and blinds are computer controlled•Solar blinds to reclaim or reject heat•Windows open when external temperature is between 20°C and 26°C and wind speed is less than 10 mph

The shafts are essentially light wells in that light travels through these wells and naturally light the six radial fingers of the building.

Sourceshttp://www.archinomy.com/case-studies/669/30-st-mary-axe-the-gherkin-london

https://prezi.com/sxt_dfdzmijt/case-study-for-the-gherkin/

http://www.webpages.uidaho.edu/arch504ukgreenarch/casestudies/swissre1.pdf

http://www.coopersfire.com/system/files/private/CaseStudy_The_Gherkin.pdf

http://skyscrapercenter.com/building/30-st-mary-axe/2369

http://faculty.arch.tamu.edu/media/cms_page_media/4433/30StMaryAxe_1.pdf

http://www.greendesignetc.net/Buildings_09/Building_Shen_Yuming_paper.pdf

http://www.engagingplaces.org.uk/teaching%20resources/art63639

http://www.engagingplaces.org.uk/teaching%20resources/art63639

http://www.archinomy.com/case-studies/669/30-st-mary-axe-the-gherkin-london

http://www.sustainablebuild.co.uk/sustainable-building-around-world.html

http://brandondonnelly.com/post/67910871416/who-knew-gherkins-were-so-aerodynamic

http://www.fosterandpartners.com/projects/30-st-mary-axe/gallery/

http://www.building.co.uk/30-st-mary-axe-a-gherkin-to-suit-all-tastes/3111783.article

http://www.skyscrapernews.com/swiss.htm

http://www.slideshare.net/adadarmon/swiss-re-building-london

http://faculty.arch.tamu.edu/media/cms_page_media/4433/30StMaryAxe_1.pdf