bejeing stadium design

8/4/2019 Bejeing Stadium Design

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Carryingthe

Torch


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Over the centuries, the Olympic torch has come to symbolize muchmore than an athletic event. As the torch travels around the globe to

the site of the next Olympic Games, it seems to embody the ideals and

aspirations of an entire generation. Perhaps for this reason, the highest

of expectations are placed on Olympic stadia, which are asked not

only to host the games but somehow to embody their spirit. Carrying

the torch this year is an iconic structure that boldly rises to thoseexpectations: Beijings new National Stadium. By Jeff L. Brown


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On Friday, August 8, when the torch is lit and the

games o the XXIX Olympiad begin, the eyes o

the world will be on Beijings Olympic Green, a

vast urban park on the north side o the city. Millions will

watch the opening ceremony on television, but those or-

tunate enough to attend the games in person will enjoy the

best views o all inside Chinas spectacular new National Sta-

dium, where the Olympic torch will burn or the duration

o the competition.

Even beore entering the arena, athletes and onlookers

rom around the world will no doubt pause or a moment

to enjoy the sight. Measuring 330 by 220 m and rising

to a height o 69 m, the recently completed building is a

major addition to Chinas capital city. The saddle-shaped

structuredesigned by a team comprising Herzog & de

Meuron Architekten ag, o Basel, Switzerland, Arup, o

London, and the China Architecture Design & Research

Group, orcag, o Beijingoccupies an area o 21 ha and

contains 258,000 m o oor space. Its seating bowl accom-

modates 91,000 ans.Given its enormous size, the stadium could have been a

aceless monolith, but ortunately it is quite the opposite. Its

steel exterior, a dynamic arrangement o crisscrossing lines,

evokes a sense o movement and excitement. Yet its gentle

curves and lack o rectilinear orms also suggest tranquil-

ity and harmony with nature. In short, the building has a

complex, magnetic personality, as thousands o visitors have

already discovered. Long beore it opened, in act, the site

had already become a local tourist attract ion.

When Herzog & de Meuron frst approached Arup about

entering the competition to design an Olympic stadium or

Beijing, Steve Burrowsa director o ArupSport, Arups

sports architecture companyremembers eeling some

hesitation. The two frms had worked together once beore,

quite successully, on the Allianz Arena, a soccer stadium

in Munich, Germany, that hosted a semifnals game during

the 2006 World Cup. Still, competitions are expensive, and

we were pretty busy at the time, recalls Burrows. The two

ormer partners agreed to enter the competition together,

on the condition that they have some un in doing it,

Burrows says.

In the competition phase, discerning what the clientis really looking or is paramount, says J. Parrish, who

leads ArupSport. In this case, the criteria laid out in

The stadiums porous acade gives spectators plenty o room to stop and enjoy the view; it also provides natural light and ventilation.


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the competition guidelines made one thing quite clear.

They wanted a landmark building, w ithout a shadow o

a doubt. They wanted one that would be the best in the

world, says Parrish. It was a very clear, very attractive

challenge.I the winning design would have to measure up to the

highest international standards o excellence, it would also

need to meet another, equally important criterion: harmony

with Chinese aesthetics. The participation o cag, a Chi-

nese design institute, on the team certainly helped. So did

a creative collaboration with the Chinese artist Ai Weiwei,

who acted as a consultant or Herzog & de Meuron on the

winning design. No matter how wonderul the architectural

scheme appeared, however, there was always this big ques-

tion mark, says Parrish. Was this going to appeal to the

Chinese culture?

In search o a design concept that would be unmistakably

Chinese, the design team drew on a variety o orms or inspi-

ration. Lingbi stonesnaturally occurring rock ormations

prized in centuries past or their symbolic value and inherent

beautywere a particular source o insight. Chinese pottery

and other ancient art orms also inormed the design.

Despite this rich and varied cultural backdrop, a single

image, drawn rom nature, has dominated public perception

o the project rom the very beginning. In act, the stadium

is best known not by its true name but by its unofcial nick-

name: the Birds Nest. The buildings broad appealnot

only to the client but also to the Chinese public in general

is no longer in doubt.

The competition guidelines made it clear that the client

was looking or something truly stunning: a world-class sta-

dium that would seat 100,000 people and accommodate a

retractable roo. The design team knew that the retractable

roo would dominate the design unless it could somehow be

masked rom view. Gradually, an architectura l scheme began

to emerge. Two long, parallel lines along the length o the

stadium were necessary in order to support the tracks or the

roo. But those lines would be disguised by a wild, seem-

ingly random arrangement o crisscrossing lines. Hidden

among those lines, right there on the exterior o the build-ing, would be the load-bearing structure, or exoskeleton, o

the entire building.

For Burrows, the concept was bold, even heroic. But ther

were practical considerations as well. As the complexity o

the design became increasingly apparent, Burrows recall

asking, I we end up winning this competition, how are w

going to draw it? The team concluded that such a projecwould be impossible without the use o a three-dimensiona

parametric model. The team selected the sotware packag

catia, developed by Dassault Systemes, which has been used

to design airplanes, automobiles, and a growing number o

buildings.

Once the competition had been won, it was t ime or th

design process to begin in earnest. The early phases o sche

matic design generally took place in Europe as team mem

bers met in Herzog & de Meurons Basel headquarters as wel

as in Britain in Arups ofces in London and Manchester

Over time, the work gradually shited rom one continen

to the other. Teams rom Europe began working in Beijing

transerring more and more responsibility or the project to

cag. As required by Chinese law, the local design institute

produced the fnal construction documents. It was an inte

grated design team, says Parrish.

To a large extent, team members attribute the success o

the project to the highly integrated design process. From th

projects inception, the architects and engineers had a close

working relationship. This unifed approach directly inu

enced the stadium design. In many ways, the architecture

and the structure are the same thing, says Michael Kwok

Arups project director, who worked in the frms Beijing

ofce. It is almost like sculpture.

Early on, the team real ized that the stadiums location

in a seismically active region would have a major inlu

ence on the overall design scheme. Although it would

seem unwise rom a seismic design perspective to incor

porate a large retractable element in such a long-span

roo, the design worked because the roo was to be so

lexible that it would be capable o absorbing a huge

amount o energy, Burrows explains. However, an earth

quake would cause the relatively sti, short-span con

crete seating bowl and the relatively lexible, long-span

steel roo to behave quite dierently, he notes. For thireason, the team completely separated the roo structur

rom the concrete bowl.

If the winning design would have to measure

up to the highest international standardsof excellence, it would also need to meet

another, equally important criterion:

harmony with Chinese aesthetics.


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The team chose steel or the roo not only or its load-

carrying capacity but also because it would make it possible

to design a structure that could be abricated and erectedby Chinas unique construction industry. The design is

well suited to Chinas strong steel abrication and erection

capabilities, observes Kwok. In act, every detai l o the steel

roo design, down to the sizes o the individual plates, was

designed with constructability in China in mind.

To the casual observer, the structure o the steel exo-

skeleton appears chaoticin act, it is deliberately designed

to look that waybut the reality is just the opposite. The

structural system is actually quite simple, says Kwok. It has

a very logical pattern o support with very clear load paths.

The structural system is hierarchical, consisting o primary,

secondary, and tertiary members, he explains. The key to

understanding the structural system is to begin with the pri-

mary, load-bearing members.

The real workhorses o the system are the 24 columns

that are arranged at regular intervals along the perimeter

o the building, orming an ellipse. The steel trusses that

make up these main columns defne the plane o the acade,

which is not strictly vertical but rather leans outward at

a slight angle (approximately 13 degrees) as it rises, lend-

ing the building its di stinctive saddle shape. These columns

rise to the u ll height o the stadium to join the 12 m deep

horizontal trusses that span the roo. The main elements o

the columns and trusses take the orm o steel box sections

measuring 1.2 by 1.2 m.

Instead o extending straight across the roo rom one side

to the other, the roo trusses ollow a diagonal path, criss-

crossing each other to leave an opening above the athletic

feld in the center o the arena. In essence, then, the columns

and trusses orm a series o interlocking portal rames that

efciently distr ibute loads to the oundations. In principle, it

is frst-year college structural engineering, says Burrows

although he goes on to admit that it is a bit more complex

than that to put together.

As one would expect in a portal rame structure, thegreatest orces are concentrated at the shoulders or joints

where the beams transmit their loads to the columns, says

Kwok. Accordingly, the steel plates at these locations are

approximately 100 mm thick. A series o struts transer axial

loads rom the curving members o the truss to the verticalcolumns.

While the arrangement o the primary structural mem-

bers is quite regular, the secondary and tertiary members are

deliberately laid out in a seemingly haphazard way to create

an illusion o randomness. Although structurally less impor-

tant, the steel boxes that make up the secondary and tertiary

members have the same 1.2 by 1.2 m dimensions as the pri-

mary members, making it nearly impossible or passersby to

spot the dierence.

What the casual observer cannot see is that the structur-

ally less signifcant members are designed to use much less

steel. In act, the plate thicknesses range rom 100 mm to as

little as 10 mm, depending on the load requirements, says

Kwok. In this way, the illusion o uniormity among the pri-

mary, secondary, and tertiary members is maintained while

the amount o steel is minimized.

Although they do not carry the bulk o the load, these

secondary and tertiary members do ulfll several important

unctions. For instance, they play a vital role in the seismic

design. Even in a severe earthquake, the primary structure

will remain elastic, says Kwok. The secondary and tertiary

members, however, are designed to yield. In this way, the

building is designed to respond to seismic orces in a way

that minimizes damage to the main load-bearing structure.

To test the design, the team subjected a computer model o

the stadium to simulated ground motion.

Another unction o the secondary and tertiary members

is to support the roo cladding, which comprises two layers.

The outermost layer, a lightweight ethylene tetrauoroeth-

ylene (etfe) membrane, protects the seating bowl rom the

wind, rain, and the suns ultraviolet rays. This outer mem-

brane, with a total area o approximately 38,000 m, covers

the entire seating bowl. It does not extend over all the con-

courses, however, because the designers wanted to provide

natural ventilation during the hot Beijing summers.An inner membrane o polytetrauoroethylene (ptfe)

orms the acoustic ceiling o the stadium, reducing

To the casual observer, the structure

of the steel exoskeletonappears chaoticin fact,

it is deliberately designed

to look that way

but the reality is just the opposite.


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noise pollution and ensuring an even distribution o sound

throughout the arena. This inner membrane covers an area

o 53,000 m.Although the exterior appearance o the building under-

standably receives most o the attention, the stadium was

in a sense designed inside out, says Parrish. Ater all, the

stadiums primary unction was to

house the Olympic Games, so it had

to accommodate a track and other

acilities that met precise geometric

requirements.

Beyond meeting those require-

ments, the stadium is also designed

to give every spectator an enjoy-

able experience. At a minimum, thismeans giving every spectator a view

o the events unolding on the feld.

However, the quality o the experi-

ence is about more than just sight

lines. The atmosphere you create is

all important, says Parrish.

With this principle in mind, the

team used a parametric design tool

developed by Parrish to optimize the

size and shape o the seating bowl.

The goal was to give 100,000 spec-

tators the best possible view o the

feld while aiming or the eel o

a smaller, more intimate arena. The

bowl went through 32 iterations

beore it assumed its fnal orm. (At

the clients request, the number o

seats was later reduced to 91,000, that

is, 80,000 permanent seats and 11,000

temporary seats or the Olympics.)

The bowl itsel is a relatively con-

ventional structure o reinorced

concrete. It provides six levels o

aboveground space and two and a hal

levels below grade. Expansion joints

divide the bowl into six segments,

creating room or expansion and con-

traction in response to temperature

changes as well as to seismic motion.

Many o the outermost columns in the

concrete bowl are inclined in order to

echo the chaotic eel o the exterior

steel structure.

Construction began on Decem-

ber 24, 2003, and or several monthsproceeded apace. Five months later

came an event that shocked the con-

struction world and gave pause to everyone involved in th

project: the partial collapse o Paris Charles de Gaulle Inter

national Airport.Designed by the French architect Paul Andreu, the air

port had opened to critical acclaim in the summer o 2003

Its breathtaking design emphasized long spans and wide ope

The stadiums exoskeleton, a dynamic arrangement o crisscrossing lines, is designed to evoke a sens

o movement and excitement. Many o the outermost columns inside the building also lean at unex

pected angles, echoing the chaotic eel o the exterior structure.


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spaces. On May 23, 2004, a 30 m long section o Terminal

2Ea tube-shaped building composed o concrete, metal,

and glasssuddenly collapsed, killing our people. Two o

the dead were later identifed as Chinese.

At the time, the National Stadium was just one o many

high-profle building projects in Beijing, a city in the process

o remaking itsel. For many in Chinas capital, the airport col-

lapse raised serious questions. Had everything necessary been

done to ensure the structural integrity o the citys own con-

struction projects? Panels o experts were convened to review

the designs o every major project. On July 31 construction o

the National Stadium came to a temporary halt.

The expert reviewers ound no cause or concern withregard to the stadiums structural integrity. During the con-

struction hiatus, however, the client also asked the design

team to examine ways o reducing project costs. Ater con-

sidering a number o options, the team recommended the

removal o the retractable roo, leaving in its place a larger,

permanent opening. We elt that was probably the best way

o reducing costs without changing the overall design o the

stadium, says Kwok.

In August 2004 the retractable roo was ofcially deleted

rom the design, a change that let the athletic feld open to

the elements but brought with it a number o advantages. In

the original design, the roo opening had been kept as small

as possible to minimize the size o the retractable element.

Now, that opening could be enlarged by about 30 percent,

shortening the spans in the space rame and greatly reducingthe amount o steel required or those spans.

Another consequence o enlarging the roo opening was

Steel proved the ideal material or the roo and acade structure o the stadium. Structurally, its load-carrying capacity was well suited both to the long

spans o the roo and to the shorter, curving girders that bridge the gaps between the primary members and give the structure its random appearance.

Just as important, by employing steel the design team took advantage o the unique strengths o Chinas construction industry. In act, every detail o

the steel roo design, down to the sizes o the individual plates, was designed with constructability in China in mind. Construction began in December

2003 and was completed in plenty o time or the Olympics, despite a fve-month hiatus during which the building was partially redesigned.

Arup


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a signifcant reduction in the overall weight o the roo. The

weight reduction was achieved both by shortening the spans

and by removing the retractable roo element, which itsel

had been quite heavy. Because o this reduction in weight,

plate thicknesses in many locations also could be reduced,

which saved even more steel. All in all, the elimination o

the retractable roo cut the amount o steel in the roo by

approximately 30 percent, says Kwok. The result was an

approximately 10 percent reduction in overall project costs.

Furthermore, the deletion o the retractable roo enhanced

the appearance o the stadium, notes Burrows. In the origi-

nal design, two long parallel lines extended the length o

the stadium, revealing the presence o the long truss beams

required to support the tracks o the moving roo. Once

the roo had been removed, those lines could be eliminated

as well. The roo opening is still defned by a ring-shaped

truss 10 m deep, but the parallel lines extending beyond that

opening are gone, thus enhancing the random appearance o

the exterior structure.

The elimination o the retractable roo would have been

nearly impossible without the use o the catia model, says

Burrows. Every single part o this building is derived rom

a mathematical equation. Because o that, i you changesomething, everything that relies upon it changes as well

in the parametric model. The roo design was so complex

that i the team had been workin

rom a set o conventional drawings

it would have been difcult even todetermine which drawings needed

to change, Burrows says. Instead

changes were automatic and could b

shared instantly with the abricato

and contractor, who also had acces

to the model.

Construction o the stadium

resumed on December 28, 2004

Despite the fve-month hiatus, th

project was completed in May 2008

in plenty o time to prepare the acil

ity or the Olympic Games.As constructed, the roo structur

employs 42,000 metric tons o steel

while the stadium as a whole con

tains 110,000 metric tons o steel

all o it produced and abricated in

China. While some have criticize

the stadium or employing exces

sive amounts o steel, Kwok fnd

the criticism misguided. Beijing ha

always been a cultural and politica

center, but the unique design o th

National Stadium and other recently

completed projects gives the city a new image o creativity

and innovation. It will also draw people to the city or year

to come. This is someplace people will want to visit, jus

like the Great Wall, Kwok says. The economic beneft i

ar greater than the cost o the building.

I the fnished building has been benefcial, so too ha

the process o designing and constructing it. As the projec

moved rom conception to completion, team partners in both

Europe and Asia were introduced to new methods o design

construct ion, and inormation management. A lot has bee

learned, says Kwok, and I think a lot o this knowledge can

be applied to other projects around the world. n

Project Credits

Client: National Stadium Company, Ltd., Beijing

Design consortium: Herzog & de Meuron Architekten ag, Base

Switzerland; Arup, London; and China Architecture Design &

Research Group, Beijing

Main contractor: Beijing Urban Construction Group Company, Ltd

Beijing, and citic International Contracting, Inc., Beijing

Steel contractor: JingGong Construction Industry Group, Zhejiang Provinc

China; Beijing bucg JingGong Steel Structure Engineering Company

Ltd., Beijing; Hu Ning Steel Company, Jiangsu Province, China; JiangNan Heavy Industry Company, Ltd., Shanghai; and ZhongZhi Group

BaoYe Construction, Shanghai

A view o the primary members reveals the buildings essential structure. Twenty-our perimeter col-

umns rise to join the horizontal trusses that span the roo. The roo trusses ollow a diagonal path,

crisscrossing each other to leave an opening above the athletic feld in the center o the arena. In

essence, the columns and trusses orm a series o interlocking portal rames that efciently distribute

loads to the oundations.

Arup


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bejeing stadium design

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