- hace 2 días
Categoría
📺
TVTranscripción
00:01Es una de las grandes marcas de arquitectura de la mundo.
00:06China es la ciudad de Forbidense,
00:08una gran colección de edificios, todos los que se han hecho principalmente de wood.
00:13Es el mayor complejo de edificios de edificios de edificios en el mundo.
00:18Dice que tenía más de 9,000 habitantes,
00:21era un lugar de poder de gran poder,
00:24a los ciudadanos de China por 500 años.
00:27Fue lleno de trastornos.
00:36Plante por una década,
00:38la construcción de mayor solo 4 años,
00:41pero se ha levantado muchas preguntas.
00:43¿Cómo se construyó?
00:45¿Dónde los recursos se ven para crear algo tan vasto?
00:52Behind este gran edificio,
00:54era una gran superpodería.
00:57Ning Dynasty China.
01:01They had the most powerful economy
01:04and technology much more in advance of the West.
01:09But can scientists decode this ancient wonder,
01:13unravel its engineering secrets,
01:15and discover how it withstood one of nature's great forces,
01:21earthquakes.
01:23Earthquakes.
01:25Earthquakes are frequent here,
01:27so they pose a huge threat to our heritage.
01:32What's it going to take to knock this thing down?
01:39Closed to the world for centuries.
01:42Now open to reveal the secrets of the Forbidden City.
01:51Right now on Nova.
01:55The Forbidden City in the heart of Beijing.
01:58The Forbidden City in the heart of Beijing.
02:00The Forbidden City in the heart of Beijing.
02:22It's about the size of 140 football fields and has at least 800 buildings.
02:35Completed in the year 1420, it was a pleasure palace,
02:40an impregnable fortress and a technological marvel.
02:51With the top craftsmen, top carpenters and top materials,
02:55so it's the best example of the technology at that time.
02:59A seat of immense power and mystery.
03:05Economically important, politically important,
03:07and militarily important.
03:09The most important site in the whole of Asia for the last 500 years.
03:15That power was embodied in the Forbidden City's awe-inspiring grandeur.
03:21This is the largest palace complex in the world,
03:26and not just the largest palace complex that survives,
03:29but the largest palace complex built at any time in history.
03:36The scale of what we see here is unparalleled in the world at the time.
03:41And everyone was struck by this,
03:43because they would never ever see anything like this in their lives.
03:47And they knew this. They knew that this was unique in the world.
03:56Built primarily of wood, the complex follows a clearly laid-out plan,
04:01aligned on a north-south axis.
04:06It was home to vast halls,
04:11the private quarters of the imperial family,
04:14temples reflecting the many forms of worship observed there,
04:18including Buddhism, Daoism, and Confucian philosophy.
04:26And it was built at an incredible pace.
04:30Major construction of the original Forbidden City buildings
04:33took just four years.
04:36In comparison,
04:38the great cathedrals of Europe
04:40took decades, even centuries to complete.
04:43There are two pressing questions at the heart of the Forbidden City.
04:49How was it built on such a massive scale so quickly?
04:53And how has it survived the powerful earthquakes
04:56that have repeatedly struck the region over the centuries?
05:02China's extensive imperial documents go back thousands of years,
05:05recording everything from battles to earthquakes.
05:07They enable researchers to build up a detailed picture of China's seismic history.
05:20This is the earthquake fault map of northern China,
05:24and Beijing is located here, right by this fault.
05:28All the red stars are earthquakes that occurred in the past 3,000 years or so,
05:34recorded in the historical books.
05:37So since the construction of the Forbidden City,
05:40we can see four large earthquakes.
05:43They really jump around from fault to fault.
05:47In 1976,
05:49a massive earthquake shook Beijing.
05:52At magnitude 7.8,
05:53it was centered in Tangshan City,
05:56around 90 miles east of the capital.
06:00In just 15 seconds,
06:02it killed at least a quarter of a million people.
06:07The highest death toll of any earthquake in the 20th century.
06:10But in this earthquake-prone region,
06:22the Forbidden City has never been brought down.
06:28What is the secret of its resilience?
06:33No Ming Dynasty plans for the original great structure have survived.
06:37But builders and engineers have gained a wealth of knowledge
06:44as they have restored this aging complex.
06:47All of the main buildings have a supporting wooden structural frame at their heart,
06:52with walls made of brick and great tiled roofs.
06:56But why and how was the Forbidden City built?
06:59It was the idea of one man,
07:05a military commander,
07:07emperor,
07:08and visionary,
07:09known as Yongle.
07:14Without the Yongle Emperor,
07:16you simply would not have had a Forbidden City that we see today.
07:21Chinese history would have taken a completely different path,
07:25and China would not have a civilization
07:28that lasted down to the present day.
07:35Ruling from 1402 to 1424,
07:39he was the third emperor of the Ming Dynasty.
07:41The Ming drew on earlier technologies unique to China.
07:54Most importantly, it was printing,
07:58paper,
08:00gunpowder,
08:02and also nautical technology.
08:04These were all things that were unknown in the West,
08:11even lavatory paper.
08:13The vast Ming Empire stretched from what is now Vietnam,
08:17almost to Mongolia.
08:19Both a scholar and a military commander,
08:23Emperor Yongle built the Forbidden City as the center of his new capital at Beijing.
08:28It was an historic decision,
08:30built to shift control into his own northern power base,
08:34and to be close to the troublesome border plains occupied by the Mongols.
08:39But unbeknownst to him,
08:40Beijing is in an earthquake zone.
08:45Not only are earthquakes here frequent,
08:47their causes are not clearly understood.
08:50By contrast,
08:51a massive 20th century earthquake took place in 1906 in San Francisco,
08:56followed by a deadly fire.
08:59The city was virtually flattened,
09:00and the reason is clear.
09:02San Francisco sits beside the San Andreas Fault,
09:05which penetrates deep into the earth between two tectonic plates,
09:09the North American and Pacific.
09:11The two plates are moving against each other,
09:15in particular Pacific plates are moving northward relative to North America.
09:21These plates move past each other,
09:23but when they become stuck, tension builds up.
09:26When it's released, the result is an earthquake.
09:30If you look around the world,
09:3290% of the earthquakes occurred along boundaries between plates.
09:38So North China, which sits in the middle of a plate,
09:42should be stable, but it's not.
09:44You have to keep in mind that this area is far away from plate boundaries.
09:50So this is a very peculiar place to have earthquakes inside the plate.
09:58In North China,
09:59the earth's crust is unusually thin and weak,
10:03giving rise to faults within the plate itself.
10:05These are known as intraplate faults.
10:10And the North China plane is cut into three pieces by three long faults.
10:17So sometimes the energy is released on this fault,
10:20sometimes on that one,
10:22sometimes on this one.
10:23Over the centuries,
10:25the Beijing region has been hit by several quakes of similar size
10:29to the San Francisco killer,
10:32and scores of smaller ones.
10:36Dr. Zhou,
10:37the Forbidden City's resident seismologist,
10:40believes the Forbidden City was designed with earthquakes in mind.
10:46They had a lot of experience with earthquakes,
10:49which shaped the building of the Forbidden City.
10:53In the centuries before the Forbidden City was built,
11:00the Chinese had learned to create resilient structures using wood.
11:15American woodworker Richard Weiborg
11:19has long made a study of China's ancient wooden structures
11:23that were built.
11:24I saw a photograph of a man sitting on the roof of a pagoda
11:28and in comparison to the size of the timbers,
11:32he looked tiny.
11:33And just the massive quality of the wood,
11:36the intricacy,
11:37the number of pieces connected together.
11:41A light went on and I said,
11:42I've got to find out more about this.
11:44A resident of San Francisco,
11:47Richard wants to understand
11:49how the buildings of the Forbidden City
11:51have withstood earthquakes.
11:53Today he's visiting Tai Miao Temple,
12:00the Temple of Ancestral Worship,
12:03built by Emperor Yangler in 1420.
12:09This huge hall was where sacrifices were made
12:12to honor the emperor's ancestors
12:14in the hope of bringing good fortune.
12:24Richard climbs up to the ceiling
12:26to investigate some of the key structural elements
12:29of Ming architecture.
12:30Here we are in a place I never imagined I'd be,
12:3520 feet off the ground
12:36in a Ming imperial building.
12:40High up,
12:41Richard gets right next to a set of brackets
12:44that link the timber frame to the roof.
12:48These are called dogong
12:50and they support a roof
12:52and stabilize the building.
12:55A bracket set is a complicated puzzle,
12:58many different parts that fit together
13:00to make a whole.
13:01And what we're hoping to discover
13:03is A, how they're made
13:06and B, why they were made.
13:08Simple dogong brackets
13:10go back 3,000 years.
13:12They gradually became more and more complex.
13:15By the time the Forbidden City was built,
13:18they had become essential structural elements.
13:21Every building has a forest of dogongs
13:25linking the columns and beams
13:27to the roof.
13:33In Beijing's architecture museum,
13:35Richard Weiborg takes one of these brackets apart.
13:41Now, after taking a deep breath,
13:44we'll try and put this back together again.
13:49The only things holding it together
13:51are precise carpentry
13:53and layers of interlocking pieces.
13:55You can see this isn't,
14:00even for somebody who's done it a few times,
14:02it's complicated.
14:04One piece goes in the front here.
14:08There you have it, a bracket set.
14:11So you can see,
14:12it's a little bit flexible.
14:14It's very strong pressing down.
14:18It can take a tremendous amount of weight.
14:20It ties together with other parts of the building
14:24and is a beautiful,
14:27creative feature of Chinese architecture.
14:30A key function of the dogong brackets
14:35is to distribute the heavy weight of the tiled roof.
14:37They do that by channeling the load evenly
14:41onto horizontal beams
14:43and down through the narrow columns
14:45supporting the roof.
14:46The dogong has the role
14:50of connecting the columns
14:52to the perling
14:54and the rafter that forms the roof.
14:56The dogong is like an element
14:59that funnels in all the loads
15:01and redistributes it on the top of the column
15:04in a very uniform way.
15:06But what role do the dogong play
15:09in protecting the buildings
15:10of the Forbidden City
15:11from the region's powerful earthquakes?
15:23A unique scale model
15:25of a classic Forbidden City structure
15:27one-fifth the original size
15:29will reveal the answer
15:31when tested
15:32under simulated earthquake conditions.
15:34The model has four key structural elements
15:42vertical columns
15:43and horizontal beams
15:45that make a timber frame.
15:48So we're seeing a column
15:50and a horizontal beam
15:51go together.
15:53Well done.
15:56This frame holds the dogong
15:58that will support the large tiled roof.
16:02This is the base block
16:04of a bracket set.
16:05And like the brackets
16:06in the Forbidden City itself
16:08this set is assembled
16:09without any fasteners.
16:11There are no nails,
16:12screws or glue.
16:14It's sort of like a wooden puzzle
16:16that's so fabulously complex.
16:19Take it, take it.
16:20This is a wonderful combination
16:22of form and function.
16:24You know, very artistic,
16:25very imaginative
16:27and very strong.
16:29It's a very sophisticated
16:32piece of woodworking
16:34and we're going to see
16:35what will happen to it
16:36when we subject it
16:37to the extreme forces
16:40of the earthquake test.
16:46This model is patterned
16:47on a building
16:48in the private area
16:49of the Forbidden City.
16:50The Palace of Longevity
16:52and Health.
16:56It's a typical
16:57Forbidden City structure.
16:59What you immediately notice
17:02is this huge golden roof
17:05that curves outwards
17:07away from the building
17:08in a way that you just
17:09don't see in European
17:10architecture.
17:11Looking up here,
17:14what we have
17:16is these elegantly
17:18coloured crossbeams
17:19decorated with
17:20imperial dragons
17:21and phoenixes
17:22and they're there
17:24to support
17:25these huge red columns
17:27that bear the structural
17:28load of that
17:29massive roof.
17:31If you look up here
17:32in between
17:33the crossbeams
17:34and the roof
17:35underneath that mesh
17:36there's these
17:37flower-shaped dogon.
17:39Together,
17:42these four structural
17:43components
17:44columns
17:45beams
17:47dogongs
17:49and roof
17:51somehow protect
17:53these buildings
17:54from earthquakes.
17:58But how do they
17:59work together?
18:03To find the answer
18:04the scale model
18:05is reassembled
18:06in a seismic lab.
18:08Ready for a series
18:13of shake table tests
18:14that will subject it
18:17to dozens
18:18of simulated earthquakes.
18:19These will push
18:22the columns
18:23beams
18:24brackets
18:25and roof
18:26to their limits.
18:28Wow,
18:29the roof is so big.
18:31It's amazing.
18:32Yes,
18:33it is.
18:34It is.
18:34This is a very authentic,
18:36traditional timber frame
18:37building.
18:39The model
18:40has traditional
18:41Ming-style
18:42brick walls.
18:43Two layers
18:44of brickwork
18:45with rubble
18:46between.
18:47Yes,
18:48we are ready to start.
18:49OK,
18:50let's go.
18:52Altogether,
18:53it weighs
18:53over three tons
18:54and could endanger
18:56anyone standing
18:57nearby.
18:58So a safe zone
19:01is created
19:02around the shake table
19:03in all directions.
19:05Go on.
19:06Test one.
19:07Start.
19:08As the test begins,
19:09the shake table
19:10moves horizontally,
19:11replicating the energy
19:12and impact
19:13of an earthquake.
19:14Gradually,
19:16the acceleration
19:17increases.
19:18Finally,
19:19three tons
19:20of Ming-style
19:21architecture
19:22starts to move.
19:24The engineers
19:25have never tested
19:26a model like this
19:27before.
19:30No one knows
19:31how long
19:31it will last.
19:36An earthquake's
19:37size
19:38is defined
19:39by its magnitude,
19:40the amount
19:41of energy
19:42released.
19:44Magnitude 4
19:45is generally
19:46considered a weak
19:47earthquake.
19:48that most modern
19:49structures can survive.
19:50But what about
19:51the model,
19:52based on an
19:53ancient design?
19:54The magnitude
19:56rises gradually.
19:58The model
19:59survives a 4
20:00and then a 4.5.
20:02The sound was
20:05like the creaking
20:06of a ship,
20:07with compressing,
20:08twisting,
20:09groaning,
20:10but no obvious
20:12damage.
20:13Next is magnitude
20:155,
20:16a massive increase
20:17with over 30 times
20:19the energy
20:20of a 4.
20:21Start.
20:26The movement
20:26piles pressure
20:27onto all
20:27the structural
20:28components.
20:31As the magnitude
20:32progresses
20:32beyond 5,
20:34the sideways
20:35movement
20:35proves too much
20:36for one
20:37of the brick walls.
20:38the walls.
20:46Maybe we'll take one step
20:47back.
20:48Yes,
20:48we are worried.
20:49It's unpredictable.
20:51While the timber frame
20:53flexes,
20:54the walls are just too
20:56brittle.
20:58The second wall topples.
20:59In traditional Chinese
21:00buildings,
21:01the walls have
21:02only the role
21:03of defining
21:04and dividing
21:05the space.
21:06They don't really
21:07have a structural
21:08role.
21:09Because they are
21:10not supporting
21:11the roof,
21:12their failure
21:13does not threaten
21:14the overall
21:15stability
21:16of the structure.
21:17That was pretty exciting.
21:28We can see the walls
21:29have completely
21:30collapsed.
21:31But the traditional
21:32timber frame
21:33is still standing
21:34strong.
21:35As the test proceeds
21:37to magnitude 7,
21:39the model is shaking
21:42but it remains intact.
21:44What role
21:47do the dogong
21:48brackets play
21:49in this?
21:50The timber frames
21:51are moved
21:52during the earthquake
21:53because of the dogong
21:55and because of this
21:56very particular
21:57connection.
21:58Through their
21:59ingenious design,
22:00the dogong disperse
22:01the energy
22:02of the tremors.
22:03So as the
22:04vibration comes
22:05through the columns
22:06and into the dogong,
22:08each of the dogong
22:09parts move
22:10relative to each other.
22:11So,
22:12through friction
22:13this movement
22:15will dissipate
22:16the energy
22:17reducing
22:18the overall
22:19effects
22:20of the
22:21airquake
22:22on the integrity
22:23of the structure.
22:28In addition to
22:29structural elements,
22:30to build the
22:31Forbidden City,
22:32Ming architects
22:33and engineers
22:34had to come up
22:35with ideas
22:36and innovations
22:37on an enormous scale.
22:38Before the
22:39main building phase
22:40could begin,
22:41a decade of preparation
22:42was needed
22:43to set up a vast
22:44and complex
22:45system of logistics,
22:46to conscript
22:47a huge labor force
22:49and create a massive
22:50supply chain
22:51across China.
22:52Because Beijing
22:54lacks natural resources,
22:56virtually everything
22:57had to be brought
22:58here,
22:59including much
23:00of the wood.
23:01The
23:04Forbidden City's
23:05palaces,
23:06temples,
23:07and the Emperor
23:08Yongle's
23:09great halls
23:10are dominated
23:11by tall,
23:12wooden columns.
23:22In the ancestral hall
23:23at Tai Miao Temple,
23:2542-foot-tall columns
23:27sparkle
23:28as if speckled
23:29with gold.
23:31Look at this
23:32magnificent column,
23:33so round
23:34and so smooth.
23:38Imagine how big
23:39the tree was
23:40that this came from.
23:43In fact,
23:44we have 68 columns
23:45in total
23:46for this hall
23:47and they're supporting
23:49the structure
23:51and they look good
23:52for us as well.
23:54This is a single log
23:55of a Nanmu tree.
23:57Today,
23:58one of the rarest
23:59of Chinese woods.
24:00It's straight,
24:01dense,
24:02and resistant
24:03to rot.
24:05Just one of these
24:06great logs
24:07weighed over 40 tons.
24:10But Nanmu trees
24:11grow more than
24:12a thousand miles
24:13from Beijing,
24:14in Sichuan,
24:15to the southwest,
24:17hidden deep
24:18in mountainous forests.
24:22Felling the trees
24:23and then dragging
24:24the heavy logs
24:25to the Yangtze River
24:26for transportation
24:27was treacherous.
24:31According to a local
24:32saying,
24:331,000 people
24:34go into the mountains
24:35and only 500
24:36come out.
24:37The mortality rate
24:38was terrible.
24:40Despite the cost
24:41and risks,
24:42the emperor
24:43demanded nearly
24:44100,000 logs
24:45to be imported
24:46from the southwest.
24:47These alone
24:49could take
24:50four years
24:51to reach Beijing.
24:56The Forbidden City
24:57also needed golden-colored
24:58floor tiles
24:59made with special clay
25:01in Jiangsu province,
25:02600 miles away.
25:04Perfectly polished,
25:06each tile
25:07took more than a year
25:08to make.
25:0980 million bricks
25:10were produced
25:11in kilns
25:12on an industrial scale
25:13outside
25:14Beijing.
25:16And piles
25:17of gold leaf
25:18hammered
25:19by hand
25:20to 1,500th
25:22the thickness
25:23of a human hair
25:24produced in specialized
25:25workshops
25:26in distant Nanjing.
25:27But how did all these supplies
25:40reach Beijing
25:41at the right time?
25:43To accomplish this,
25:44the emperor's engineers
25:45extended China's
25:46ancient Grand Canal.
25:48A simpler version
25:49was constructed
25:50over a thousand years
25:51earlier.
25:52But Yangle
25:53revitalized the
25:54and expanded it
25:55into a water superhighway
25:56able to carry
25:57everything needed
25:58to Beijing.
25:59The Grand Canal
26:00is both longer
26:01and older
26:02than the Panama Canal
26:03and the Suez Canal.
26:04They really solved
26:05a very large problem
26:06of canal engineering
26:07at the time.
26:08The Grand Canal
26:09is both longer
26:10and older
26:11than the Panama Canal
26:12and the Suez Canal.
26:13They really solved
26:14a very large problem
26:15of canal engineering
26:16at the time.
26:17The Grand Canal
26:18ran over a thousand miles
26:19from commercial Hangzhou
26:20across the Yangtze
26:21and Yellow Rivers
26:22before reaching Beijing.
26:23This is the main channel
26:24of the Grand Canal.
26:25To the south
26:26is Hangzhou.
26:27To the north
26:28is Beijing.
26:29Today,
26:30this section
26:31is mostly dry,
26:32but it's still
26:33popular.
26:34The Grand Canal
26:35and the Suez Canal
26:36and the Suez Canal
26:37and the Suez Canal.
26:38They really solved
26:39a very large problem
26:40of canal engineering
26:41at the time.
26:42The Grand Canal
26:43ran over a thousand miles
26:44from commercial Hangzhou
26:45across the Yangtze
26:46but it's still possible
26:47to see the remains
26:48of the Ming's
26:49water engineering.
26:52This is what
26:53it would have looked like
26:54600 years ago.
26:57It would have been
26:58full of barges
26:59carrying workers,
27:00soldiers,
27:01materials,
27:02and grain supplies
27:03north
27:04to feed
27:05the huge
27:06Beijing building site.
27:09But before this
27:10could happen,
27:11the Ming faced
27:12an enormous
27:13engineering challenge.
27:14Standing in the way
27:15of the canal,
27:16was a series of hills.
27:19The high point
27:20of the canal
27:21was at Nanwang,
27:22300 miles south
27:24of Beijing.
27:25This point here
27:26is approximately
27:27the watershed
27:29between the north
27:30and south section
27:31of the Grand Canal.
27:32So,
27:33if we were to drop
27:34water here,
27:35water on this side
27:36of the line
27:37would flow north,
27:38water on this side
27:39of the line
27:40would flow south.
27:41to get the canal traffic
27:42over the high ground
27:43at Nanwang
27:44meant that millions
27:45of gallons
27:46of water
27:47had to be diverted
27:48from nearby rivers.
27:50Here we are
27:51at the center
27:52of the Nanwang
27:53water diversion project,
27:55part of the
27:56Grand Canal system.
27:59This Ming dynasty map
28:00shows how rivers
28:02were dammed
28:03to feed water
28:04into huge locks
28:05at Nanwang.
28:06These large enclosures
28:09could be flooded
28:10and drained
28:11to raise
28:12and lower barges
28:13allowing them
28:14to get over
28:15the high ground.
28:17To fill the locks
28:18and raise the barges,
28:19water had to be
28:20diverted
28:21from the Wen River
28:22and stored
28:23in three huge
28:24man-made lakes.
28:25Barges traveling
28:28up the canal
28:29to Nanwang
28:30entered a series
28:31of locks
28:32over three miles long.
28:33The river water poured in
28:35to raise the barges
28:36so they could proceed
28:37step-by-step
28:38over the high ground
28:39toward Beijing.
28:40As a modern-day engineer,
28:41I think the main reason
28:42why this is so impressive
28:43is partly because
28:44of the size
28:45but also because
28:46of the complexity
28:47of trying to manage
28:48the water
28:49over such a large area.
28:50That's a huge achievement
28:51even in modern times
28:52in the world.
28:53It's also because
28:54of the size
28:55and also because
28:56of the complexity
28:57of trying to manage
28:58the water
28:59over such a large area.
29:00That's a huge achievement
29:02even in modern-day
29:03engineering terms.
29:06And for just this section
29:07of the canal
29:08there was
29:09300,000 laborers
29:11conscripted
29:12working for a period
29:13of 200 days
29:15constantly.
29:16And they created this
29:17with only the most
29:18rudimentary
29:19hand tools.
29:21But how could the Ming
29:23afford this?
29:25The cost was borne
29:27by the emperor's
29:28subjects in money,
29:30materials,
29:33and lives.
29:34Tens of thousands
29:35of people
29:36starved to death.
29:37He worked convicts,
29:40he worked the military,
29:41he worked ordinary
29:42peasants,
29:43he squeezed as much
29:45as he could
29:46out of the taxes
29:47in order to build
29:48their capital.
29:49The result was
29:51an engineering masterpiece.
29:53Much of the Grand Canal
29:55is still in use today.
29:57This massive infrastructure
29:59project changed China
30:00forever.
30:01Just as building
30:02the Forbidden City
30:03altered the landscape
30:04of Beijing itself.
30:05This hill gives us
30:06an amazing aerial view
30:07of the Forbidden City.
30:08What's more incredible
30:09is that prior to the
30:10construction this hill
30:11didn't even exist.
30:12It was actually built
30:13using the earth excavated
30:14from the moat.
30:15All this was produced through
30:16the meticulous planning
30:17Emperor Yongle demanded.
30:18He insisted on controlling
30:19each step of the
30:20vast project himself.
30:21but there were some forces
30:22neither he nor his successors
30:23could control.
30:24He insisted on controlling
30:25each step of the vast
30:26project himself.
30:27But there were some forces
30:28neither he nor his successors
30:29could control.
30:30Back at the seismic lab, Dr. Joe
30:31and Richard Weiborg are ready to
30:32continue the shake table tests
30:33on the scale model of a
30:34Forbidden City building.
30:35All this was produced through
30:37the meticulous planning
30:38Emperor Yongle demanded.
30:40He insisted on controlling
30:41each step of the vast
30:42project himself.
30:43But there were some forces
30:45neither he nor his successors
30:47could control.
30:48Back at the seismic lab,
30:51Dr. Joe and Richard Weiborg
30:54are ready to continue
30:55the shake table tests
30:57on the scale model
30:58of a Forbidden City building
30:59They're still there too.
31:01Having reached magnitude 7
31:03with only the brick walls
31:04falling,
31:05they now want to see
31:06if the model can withstand
31:08the force of an even
31:09greater earthquake.
31:10Magnitude 7.8.
31:12This matches the size
31:15of the 1976 Tangshan
31:17City earthquake
31:18that killed a quarter
31:20of a million people
31:21east of Beijing.
31:22It's a massive human
31:23disaster.
31:24And many, many,
31:26the whole families
31:27are not a single person
31:28survived this event.
31:32In just 15 seconds,
31:3485% of the structures
31:36in the city were destroyed.
31:38The Tangshan area
31:40has this tradition
31:41of stone type of buildings.
31:44So basically all the walls,
31:46all the houses,
31:47they were all constructed
31:48by very heavy rocks.
31:50Good for insulating heat
31:52and cold,
31:53but they're not very good
31:55at resisting earthquakes.
32:01If the heavy stone buildings
32:02of Tangshan failed to resist
32:04a magnitude 7.8 earthquake,
32:06how will the wooden model
32:11perform under a similar assault?
32:13Get ready to jump.
32:17Whoa!
32:18It scared me, I'll tell you.
32:23Will the columns and beams,
32:27the dogong brackets,
32:29and the heavy tile roof
32:31stand up to such powerful shaking?
32:34Amazingly, even after a period
32:39of 30 seconds longer than many
32:41real life earthquakes,
32:43they do.
32:44What's it going to take
32:45to knock this thing down?
32:50When Dr. Zhou and Richard examine the model,
33:01they find one more secret
33:03to its resilience,
33:05the columns.
33:07This red line shows the column's
33:09position before the earthquake.
33:11We can see that after the earthquake,
33:14the column has moved over here.
33:16The model replicates the way
33:18the columns stand in the Forbidden City itself,
33:22resting freely on stone foundation plinths.
33:28If they were pounded deep into the stone,
33:31they would break if overwhelmed
33:33by the shaking of an earthquake.
33:35Instead, by being left free to move,
33:39they can ride out the tremor.
33:41The model shows how the columns move,
33:44dispersing energy and helping the whole building
33:47withstand the shaking.
33:50What we see here is the effect of the shaking
33:53on the columns.
33:55We can see that all the columns rotate slightly.
33:58This helps to dissipate energy
34:01and to isolate the movements to the roof.
34:04And in that way, the structure is still surviving.
34:08But what about the large heavy roof?
34:13Its curved shape is a tradition that dates back 2,000 years.
34:17To build the roof, timber boards are laid onto the rafters.
34:23On the outside, layers of red clay are used to waterproof it
34:29before glazed tiles are pushed into the clay and overlapped.
34:33The colorful roof tiles and mythical beasts that adorn them
34:41are still produced in kilns outside Beijing using traditional methods.
34:47The area's unusual clay produces long-lasting tiles,
34:51but they are heavy.
34:54The roof of a big hall in the Forbidden City
34:57is estimated to weigh 2,000 tons.
35:02All that weight resting on the Dogong brackets
35:05connecting it to the columns below.
35:08Exactly the same tiles and construction technique
35:12have been used on the 1-5th scale test model.
35:16Look at the roof moving.
35:20It swings back into place, helping it to recover.
35:24Because of the interlocking construction,
35:27the Dogong, roof, and frame are connected
35:31but can move independently, isolated from each other.
35:35The timber frame is moving at higher speeds
35:40while the roof is moving at a much lower speed.
35:44Slow motion reveals how the movement of the roof
35:52lags behind the timber frame.
35:56And while the bottom of the structure shifts in one direction,
36:00the roof moves the opposite way,
36:03countering the effect of the shaking.
36:05There is almost like a recentering action here,
36:10because as the timber frame tends to move out in one direction
36:14and the roof is still moving in the opposite direction,
36:17it pulls it back towards resting position.
36:20The roof acts as a counterweight,
36:24balancing the structure and saving the building from collapse.
36:28But state-of-the-art engineering, carpentry, and logistics alone
36:41did not satisfy the ambitions of the Ming Emperor Yangle.
36:45He also demanded artistry.
36:52The centerpiece of the Hall of Preserving Harmony
36:55is a magnificent grand staircase.
37:00It's the largest stone sculpture in the Forbidden City,
37:07showing dragons playing in the clouds.
37:11Hand-carved from a single vast block of marble,
37:15more than 50 feet long,
37:17it weighs over 300 tons,
37:20more than two jet airliners.
37:23This marble came from quarries 40 miles from Beijing.
37:28But getting the raw stone from the quarry to the Forbidden City
37:32was a major challenge.
37:34After the stones were quarried,
37:37they were too large for human labor to move.
37:40So, what did they do?
37:42Beijing's climate is harsh,
37:45and in the winter, the area freezes over.
37:48Ming records describe an ice road,
37:53shaped by engineers to cross any obstacle.
37:58But how did the Ming move the massive marble blocks
38:01along the ice roads?
38:03Rob Dwyer-Joyce is an engineer who researches friction.
38:07He has designed an experiment to answer this question.
38:11What we have is a wooden sled,
38:14and we've loaded it with stone
38:17weighing about a tonne, 1,000 kilograms or 2,200 pounds.
38:21And we're going to do an experiment
38:22to try to pull this along by hand on the ice.
38:25This is going to be quite difficult because it's...
38:31No, we can't get shifted.
38:33As they struggle,
38:35a whole ice hockey team comes to the rescue.
38:38But even these strong athletes have a hard time getting it moving.
38:52Whoa!
38:55So how much force does it take
38:57to get a one-ton sled moving across the ice?
39:01So now we've put a load cell in front of the sled,
39:04and we're going to measure the force on this load cell
39:06as the guys start pulling.
39:08And now let's have some more skaters.
39:11And again.
39:14What we can see here is a force versus time graph.
39:17As we added a player,
39:19you can see it increases in the steps,
39:21and then it gets to a certain force,
39:23and then drops.
39:25And this drops because the sledge starts to slide.
39:27And when we do that,
39:28the force required to pull the sledge along plateaus.
39:31It takes a team of players to get the sled moving,
39:50but only one to keep it moving.
39:54So the challenge is to get it started.
39:57We know from historical sources that the Chinese had water supplies along the route that were moving the stones.
40:04And it's not quite clear what they used that water for.
40:07Ancient documents describe wells dug at 550-yard intervals along the ice road.
40:13Rob has a theory that the wells provided water to help get the huge marble blocks moving along the road.
40:21I'm going to put some water down there.
40:23See how many we need when we've slightly wetted the ice.
40:27Go on, pull it, pull the ice.
40:32The water acts as a lubricant between the ice and the sled, making it easier to get it to start.
40:39And once it's moving, continuing pressure melts the ice, keeping the sled going.
40:46The Chinese move these large lumps of stone on a much bigger scale than what we've done today.
40:52I'd rather admire them for having done that several hundred years ago to realize that once the sled was moving, it generated friction, but they probably needed water to form that film between the sled and the ice to get started in the first place.
41:05This level of engineering skill made it possible for artists to carve the magnificent marble staircase at the Hall of Preserving Harmony.
41:17New discoveries about the Forbidden City's paint are now coming to light.
41:19New discoveries about the Forbidden City's paint are now coming to light.
41:20The Hall of Mental Cultivation was built in a quiet, private space.
41:21Another artistry is found throughout the Forbidden City.
41:25This is epitomized by the use of a vast array of colors, turquoise, blue, and green, both inside and outside the buildings.
41:39New discoveries about the Forbidden City's paint are now coming to light.
41:46The Hall of Mental Cultivation was built in a quiet, private area of the Forbidden City, which is being restored.
41:56Dr. Lei and his team are working to identify the precise pigments used in the paints.
42:06The paint is falling off, so first of all, we need to find out what type of paint it is.
42:14The scanner emits X-rays, which are reflected back in a unique frequency for each element in the pigment.
42:22Back in his lab, Dr. Lei uses both the scan data and a microscopic examination of paint fragments to identify the precise pigments used.
42:35It looks like a man-made pigment. It's called smolt.
42:41Blue smolt is not a naturally occurring pigment, and it wasn't made in China.
42:46It's a synthetic color, made by adding cobalt oxide to molten glass.
42:53It was made in Europe after China's Ming period, so these layers of paint were likely applied during a later restoration,
43:02and may be evidence of international trade and exchange.
43:05It also suggests that no expense was spared to decorate the Forbidden City with the world's finest materials.
43:19Today, the Forbidden City is a world heritage site that attracts 16 million visitors a year.
43:26But 600 years ago, these halls and courtyards were reserved for the elite.
43:33The name itself, the Forbidden City, indicates that ordinary people were not welcome here.
43:40It took over a million laborers to build the expansive complex.
43:51In December 1420, it was complete.
43:55Diplomats and dignitaries arrived from across Asia for its grand opening ceremony.
44:00Visiting ambassadors describe how elephants flanked the main gate.
44:07A hundred thousand people from the Ming Empire and beyond filled the Great Square.
44:14They've never seen this level of craftsmanship.
44:18They've never seen the scale of Beijing or the Forbidden City.
44:22They're overwhelmed by just the physical space.
44:25And of course, that is the intention of building the Forbidden City.
44:27It's this statement of political power.
44:30The power of the dynasty, but also the power of the emperor.
44:32The man who sits on the throne.
44:34And for most people at the time, they were persuaded.
44:37Yeah, that's right.
44:38This is the most powerful man in the world.
44:43The Emperor's Day typically began at the Palace of Heavenly Purity.
44:48This courtyard and the palace behind me is the most sacred location in the entire Forbidden City.
45:00This was Yanglu's residence.
45:02And every morning he would rise at about four o'clock and he would come down this central pathway.
45:12Only he could pass along the central line for the dawn audience.
45:16At daybreak, hundreds of officials would gather in silence to kowtow before His Majesty.
45:33Filling the courtyard in front of the city's grandest structure, the Hall of Supreme Harmony.
45:39In the very center is the throne.
45:51And above, you have the symbol of the heavens.
45:56And the throne is directly underneath the heaven.
46:00Why?
46:01Because the emperor is the son of heaven.
46:03China's traditional belief system demanded that the emperor constantly prove he had the mandate of heaven.
46:15And he had to demonstrate as well that he was worthy to rule by maintaining a careful balance between the earthly and cosmic orders.
46:24But that harmony could be disrupted by nature.
46:27Fire, caused by accidents or lightning strikes, was a constant threat to these mainly wooden structures.
46:38The Hall of Supreme Harmony itself burned down many times.
46:47But another great fear was earthquakes.
46:50On the morning of September 2nd, 1679, Beijing was struck by disaster.
47:00The city was hit by one of the biggest earthquakes in its entire history.
47:11Imperial records suggest it killed around 15,000 people.
47:15China's detailed historic records hold valuable clues, which Professor An Yin uses to work out the magnitude and nature of ancient earthquakes, including the one in 1679.
47:32There is some kind of tombstone, which is supposed to face to one direction, usually face to south, but that tombstone rotate.
47:42So that's very important to geologists because we can use those historical records to determine the way the earthquake was generated, whether it's moving up and down or sideways.
47:52So for this one, it has to be moved by the sideways.
47:55Imperial records suggest the 1679 quake was a magnitude eight.
47:59It destroyed thousands of stone structures, including the original white pagoda or stupa.
48:07For Buddhists, a place of meditation.
48:10So here we see the white stupa constructed originally in 1651 and then destroyed in a massive earthquake, but then almost immediately rebuilt.
48:19The restored stupa still towers over the imperial park and Beijing.
48:26But while the original stupa collapsed in 1679, records indicate that the forbidden city just 500 yards away suffered only minor damage, mainly to the brick walls.
48:37Most of the descriptions focus on the city walls and the city gates.
48:43It seems like the major palaces, architectures are not damaged.
48:48But can the model in its final seismic test withstand a force even greater than the 1679 earthquake?
49:02The scientists will now expose the model to magnitude 8.2, the power of the largest earthquake ever to hit the Beijing region, and stronger than the 1906 earthquake that destroyed San Francisco.
49:19Magnitude 8.2.
49:20Magnitude 8.2.
49:21Begin.
49:22Now the quake is getting stronger.
49:23The frame is shaking badly.
49:24Pretty darn strong.
49:25The test moves to magnitude 8.6, the strongest earthquake to hit this part of Asia.
49:42It shook Tibet in 1950, destroying over 70 villages and causing massive landslides.
49:52As the magnitude increases and the shake table delivers more energy, the structure sways dramatically, but it remains standing.
50:02This is incredible.
50:04After a series of escalating shocks, the test moves beyond 9.5, the largest quake in recorded history.
50:18This devastated Chile in 1960, causing a tsunami as far away as Hawaii.
50:25Magnitude 10.1.
50:26Begin.
50:27In this final phase, the shake table peaks at magnitude 10.1, as high as the technology can go.
50:43The test must come to an end.
50:55Test finished.
50:56We wanted to break this building, and it wouldn't break.
51:00So, wonderful test.
51:02What was most surprising to me was how much the building could move, how flexible it was.
51:11This is a fabulous proof of the genius of Chinese traditional architecture.
51:23To build the Forbidden City 600 years ago, the Ming Chinese had to meet a vast array of challenges.
51:31Mastering logistics on land, water, and ice.
51:36Applying engineering ingenuity and carpentry skill.
51:40And demonstrating artistry of color and design.
51:43It cost thousands of lives, and the toil of a nation.
51:49But they built a city unique in all the world.
51:53At least 800 buildings, mainly all out of wood.
51:57It was the Ming Dynasty's most enduring creation.
52:02The beating heart of their empire.
52:06The Forbidden City.
52:08The Forbidden City.
52:09The Forbidden City.
52:11The Forbidden City.
52:13The Forbidden City.
52:14The Forbidden City.
52:15The Forbidden City.
52:16The Forbidden City.
52:17The Forbidden City.
52:18Gracias por ver el video.
52:48To order this program on DVD, visit Shop PBS or call 1-800-PLAY-PBS.
52:56Episodes of Nova are available with Passport.
52:59Nova is also available on Amazon Prime Video.
53:18睡ed up on Amazon Prime Video.
53:30New Dimensions
53:32New Dimensions
53:34New Dimensions
53:36New Dimensions
53:38New Dimensions
Sé la primera persona en añadir un comentario