Introduction What is Dome structure? A Dome may be defined as a self-supporting structural element of architecture that resembles the hollow upper half of a sphere . Domes are in architectural terms particularly demanding structures. Domes have been popular in the construction of buildings since ancient times. This particular design has the important characteristic of withstanding adverse climatic conditions such as earthquakes, tornadoes, floods, hurricanes, or even tropical storms. Earlier domes were used only in religious buildings, however its usage has now been seen in constructing residence buildings as well. Houses with dome construction are usually found in regions which experience heavy winds and extreme climatic conditions. The trend is speedily catching up in constructing residential buildings and public structures.
Transcript
Introduction
What is Dome structure?
A Dome may be defined as a self-supporting structural element of architecture that resembles the hollow upper half of a sphere . Domes are in architectural terms particularly demanding structures.
Domes have been popular in the construction of buildings since ancient times. This particular design has the important characteristic of withstanding adverse climatic conditions such as earthquakes, tornadoes, floods, hurricanes, or even tropical storms. Earlier domes were used only in religious buildings, however its usage has now been seen in constructing residence buildings as well. Houses with dome construction are usually found in regions which experience heavy winds and extreme climatic conditions. The trend is speedily catching up in constructing residential buildings and public structures.
A corbel dome is different from a 'true dome' in that it consists of purely horizontal layers. As the layers get higher, each is slightly cantilevered, or corbeled, toward the center until meeting at the top.
Onion dome
The onion dome is a bulbous shape tapering smoothly to a point, strongly resembling an onion, after which they are named, and exemplified by Saint Basil's Cathedral in Moscow and the TajMahal. They are found mostly in eastern architecture, particularly in Russia, Turkey, India, and the Middle East. An onion dome is a type of architectural dome usually associated with Russian Orthodox churches. Such a dome is larger in diameter than the drum it is set upon and its height usually exceeds its width.
Oval dome
An oval dome is a dome of oval shape in either plan or profile or both. The term comes from the Latin ovum, meaning "egg". Although oval domes have been dated at least as far back as the Middle Ages, many Renaissance and Baroque domes are of this type, notably those of Bernini and Borromini.
Parabolic dome
A parabolic dome is a unique structure, in which bending stress due to the UDL of its dead load is zero. Hence it was widely used in buildings in ancient times, before the advent of composite structures. However if a point load is applied on the apex of a parabolic dome, the bending stress becomes infinite. Hence it is found in most ancient structures, the apex of the dome is stiffened or the shape modified to avoid the infinite stress.
Polygonal dome
A polygonal dome called domical vaults, or cloister vaults, these are domes which maintain a polygonal shape in their horizontal cross section. The most famous example is the Renaissance octagonal dome of Filippo Brunelleschi over the Florence Cathedral.
Sail dome
Also called sail vaults, pendentive domes, or Byzantine domes, this type can be thought of as pendentives which, rather than merely touching each other to form a circular base for a drum or compound dome, smoothly continue their curvature to form the dome itself. The dome gives the impression of a square sail pinned down at each corner and billowing upward.
Saucer dome
A saucer dome is the architectural term used for a low pitched shallow dome which is described geometrically as having a circular base and a segmental (less than a semicircle) section. A section across the longer axis results in a low dome, capping the volume. A very low dome is a saucer dome. Many of the largest existing domes are of this shape.
Gaining in popularity from the 18th century onwards, the saucer dome is often a feature of interior design. When viewed from below it resembles the shallow concave shape of a saucer. The dome itself, being often contained in the space between ceiling and attic, may be invisible externally.
Umbrella dome
Also called pumpkin, melon, scalloped, or parachute domes, these are a type of dome segmented by ribs radiating from the center of the dome to the base. The material between the ribs arches from one to the other, transferring the downward force to them. The central dome of the Hagia Sophia uses this method, allowing a ring of windows to be placed between the ribs at the base of the dome. The central dome of St. Peter's Basilica also uses this method.
Domes can also be classified
Influential domes
Domes that have been disproportionately influential in later architecture are those of the Pantheon in Rome, Hagia Sophia in Constantinople (modern Istanbul), and the Dome of the Rock in Jerusalem. In Western architecture, the most influential domes built after the early Renaissance exploit of Brunelleschi's Florentine dome have been those of St. Peter's Basilica in Rome and Jules Hardouin-Mansart's dome at Les Invalides in Paris. The dome of St. Paul's Cathedral in London was the inspiration for the United States Capitol in Washington, which in turn inspired domes of most of the US state capitols.
Domes in buildings of worship
The Green Dome built above the tomb of Muhammad, Abu Bakr and Umar in the Al-Masjid al-Nabawi (Prophet's Mosque) in Medina, Saudi Arabia, dates back to at least the 12th century.
Domes also play a very important part in places of worship where they can represent and symbolize different aspects of the religion. Eastern Orthodox churches, for example, have domes
which represent heaven. The dome's purpose is to remind people that to gain God's blessing it is necessary to accept salvation through Christ. Domes can also be found in Islamic places of worship, called mosques. In an Orthodox church the domes have pictures of Jesus, while mosque domes have geometric patterns or Arabic calligraphy, as Islam rejects the use of images of Muhammad or other Muslim prophets. The domes are traditional in Islam, and also make the building clearly recognizable from a distance.
Advantages of Dome Buildings
Strength
The Monolithic Dome has many different aspects that make it the best choice in construction. Domes are extremely durable and strong. While the average building life is measured in decades, the Monolithic Dome can be measured in centuries. They are fire, water, and wind resistant, making them impervious to hurricanes, tornadoes, fires and other threatening natural disasters. In one instance, after Hurricane Frances hit the coast of Florida, a dome built right on the shore was one of the only buildings left standing. The residents simply closed their hurricane shutters and let the storm pass, their home suffering very little damage.
Fireproof
In another case in California, fire-fighters took refuge in a dome home to escape a ravenous forest fire surrounding it. The fire caused only minimal damage to the home. In one industrial example in Channelview, Texas, an electrical fire caused 300 gallons of transformer oil to ignite and burn three wood-framed structures while the Monolithic Dome storage unit remained intact, preserving the materials inside.
Energy Efficiency
The Monolithic Dome is not only disaster proof, but also extremely efficient. The dome structure allows for a wide variety of floor plan designs because it needs no interior support. This allows you to take advantage of the wide open space of your building. Because of the structure's tightness, they conserve vast amounts of energy, making them more cost effective to run and heat. In a regular stick home, the amount of airflow going through the home is equal to having a door open all the time. The Monolithic Dome, however, is so well insulated and tight that the airflow amounts to an opening the size of two pencils.
Low Maintenance
A dome is also significantly easier to maintain than a regular building. There is no worry about roof repairs, wood rot, termite damage or any other sort of inconvenient maintenance required in a conventional structure.
The dome is a structurally sound design. These days they often made of concrete and reinforced by steel. The main advantage of this style of design is that as it’s heavier in weight, it is difficult to lift it off its base. Moreover, besides the weight of steel and concrete, the shape of the dome itself makes it a very solid structure. According to architects, the arches of the dome are naturally strong and are hardly influenced by extreme external forces like tornadoes. Also with no flat walls, these kinds of structures have very few seams, leading to less penetration of water in the construction especially during tropical storms. Moreover, using archways as gates on either side of the building can also help water to run straight off without causing any lasting damage.
Challenges in Design and Construction
• Weight
• Construction
• Material of use
• Span
• Installation
• Interior illumination
• Fire safety
Oita Stadium Japan
In Oita Japan, stands the largest dome on earth. It is an architectural marvel built from steel Teflon and titanium.
It covers a stadium to comfortably seat over a 40000 spectators. At the flick of a switch the roof can open like gigantic eye.
The Oita dome is pinnacle of structural engineering.Oita owes its secret of success to six iconic domes at the heart of each lays a major technological innovation that allowed engineers to build a bigger dome.
One by one travelling back in history we will reveal the incredible stories behind these challenges and the inventions that allowed them to span ever greater distances.
Ancient Rome
In 2nd century AD Emperor Hadrian wanted to build a temple to Roman gods. The PANTHEON and insists to be capped with biggest dome in the world.
Roman discovered that if they take lumps of rock and embed them in special mortar they end up with a substance which is extremely tough and can be formed into any shape, they call it concrete.
The PANTHEON (43mts)
Concrete is very durable but also very heavy. If Dome is built with concrete it could weigh over 20000 tons. Such an enormous weight would cause base of the dome to splay outwards, resulting in catastrophic failure.
To reduce the weight, concrete must be made lighter. Using volcanic rock aggregate like basil was common during those days which is very strong and makes concrete very strong but also made it very heavy.
So romans used Pumice which is very light in weight as there aggregate in concrete to build PANTHEON.
Leap 1: Weight
Using light weight concrete helped in cutting weight concrete by a 1/3rd .To reduce much more weight masons cut down the concrete where ever they can. They tapered the walls of the dome making thickest at the base and thinnest at the crown. They even left the apex open to save concrete and hollowed out the panels which formed the ceiling of the dome.
This overall helped them in cutting weight to 5000 tons which is a mere 1/4th of original weight. But engineers are worried still that the base could splay outwards.
So they strapped 7 concrete rings around it these tension rings hold the walls in like hoop reinforcement.
This dome is 2000 years old and it is still the biggest unreinforced concrete dome structure in the world.
Showing thickness of walls
Tension rings of concrete
The Pantheon
Thanks to lightweight concrete and heavy weight thinking Hadrian managed to build the PHANTHEON.
This dome is 2000 years old and it is still the biggest unreinforced concrete dome structure in the world
Florence 14th century
It took more than 1000 years to someone try to build a much bigger dome than PANTHEON. In late 14th century in the city of FLORENCE the officials of city wanted to finish their existing 40m high cathedral with a big brick dome.
The FLORENCE CATHEDRAL 45m wide dome.
Like the PANTHEON the dome in FLORENCE CATHEDRAL need wooden scaffolding to support the structure during construction.
Leap 2: Construction
The engineers calculated that they need more than 700 trees some of them over 100m tall but there are no trees around Florence this tall. So they have to figure out a different solution to how they build the dome.
Different options were considered. Like trying to fill the structure with earth or soil to build the dome supporting it and later to remove the earth after construction but this was dropped later. The years drive by the cathedral is still without a roof and constructing a dome without scaffolding seemed impossible.
But in 1418 a local clock maker named FILIPPO BRUNELLESCHI stepped forward. He developed a unique method of laying bricks which becomes a key to build the dome.
The biggest problem comes when the brick layers reach the top of the dome where the walls start leaning forward. To build on such a steep slope Brunelleschi plans to lay some of bricks vertically so that they stick out of work face.
These vertical bricks would act as bookends that hold the horizontal bricks in place. But to put his plan in action he needs to find a way to place the first row.
Solution
He uses a small piece of wooden cradle support which hung it of the wall which is already there and placed the first row. But even with Brunelleschi clever method it takes 300 men 15 years to build the dome.
FLORENCE CATHEDRAL is finally finished in 1446 which is to till date the largest brick dome ever built.
Scaffolding required which is over 100m tall
Brick placing technique
Florence cathedral
FLORENCE CATHEDRAL is finally finished in 1446 which is to till date the largest brick dome ever built.
Indiana West Baden Hotel
At the turn of the 20th century local entrepreneur LIAISON CLARET wanted his hotel to have finished with the biggest dome in the world
LIAISON CLARET wanted a 200feet wide dome, many people thought he was crazy to build West Baden hotel in Indiana Engineers would have find a better building material. Claret’s architect knows he can’t build a dome with brick, concrete.
Leap 3: Steel
Claret finds inspiration at cutting edge of 19th century technology. Claret went to bridge engineer to construct his dome.
The engineer locked 6 bridge trusses across a central hub to create a dome structure. These support a roof made from tiles and glass.
Steel is very strong and light but it expands due to heat .If the steel dome is fixed to masonry base or concrete column structure on hot days steel could expand and could tear the roof from the support and lead to failure.
To prevent this engineers attached rollers to base of each truss this allows horizontal movement of truss due heat expansion and cooling.
Six trusses attached to a central hub
Roller supports allowing expansion and contraction
Indiana West Baden Hotel
In 1902 LIAISON CLARET showed that steel was the key to make domes bigger
Huston Texas-ASTRODOME
In late 1950’s Huston Texas baseball team wanted an indoor stadium to play baseball. So the engineers planned a 196m wide dome which could keep the weather out and let the light inside. They call it ASTRODOME.
This dome is glazed by a Perspex which was commonly used in aircrafts cockpits during world war 2.Perspex was a new type of plastic which weight ½ of glass .It is light, strong and clear so light rays pass through which created a problem .The unimpeded sunlight which cast harsh shadows on the field which could trouble the players
Leap 4: Light
To solve the problem the designers add microscopic layer of prisms to the Perspex which diverges the rays and diffuse the light .They fit 5000 panels of Perspex to the roof to spread the light evenly across the stadium.
It opened in April 1965 it was hailed as architectural triumph. One player tried to catch high ball was nowhere near it, he blames the glare of the Perspex roof.
In astrodome the inside of the dome is relative darkness compared to outside which causes glare when you look up.
The ASTRODOME finally concedes defeat and they simply paint over the Perspex panels. Now players can see the ball but the lack of light kills the grass. So finally they lay field made of AstroTurf instead of grass.
Harsh shadows due to usual glass roof
Prism used to diffuse light
Astrodome
Back in 1960’s the success of Huston ASTRODOME inspired stadium designers to build much bigger domes.
ATLANTA Georgia Dome (227m)
In 1990 the designers of the Georgia dome 227m have to make sure their stadium didn't become a death trap.
In England May 1985 brad pit city football club stand caught fire when it was packed with 3500 people, and around 56 lose their lives.
So architects designing the Georgia dome 5 years later knew such a fire even would be worse in enclosed space.
Leap 5: Fire
The engineers of Georgia dome put powerful fans in strategic positions, as soon fire is detected the emergency ventilation system kicks into action.
Fans mounted in the ceiling begin to spin simultaneously air intake open up an run to create a through draft, thus smoke dispersed harmlessly outside.
Exhaust system used in Georgia dome
Olympic Stadium- Montreal.
Leap 6: Retractable roof
The first attempt to build a retractable roof was made in 1986 in Olympic stadium in Montreal.
Engineers built a hollow tower nearly a 100m high. They tread steel cables down through the tower and wind then on wrenches and the other end is attached to the roof which is an enormous sheet of Kevlar weighing 65 tons.
On sunny days technicians can wind the cables an raise the roof to let the light and air inside in cold weather they simply can drape the sheet back over the stadium.
It’s a beautiful design but only on paper when one day when it’s raised the sheet rips off and over the years if rips off number of times so it’s finally replaced with a fixed roof.
Retractable roof arrangement
Oita Stadium Japan
Today in Oita engineers face the similar problem as the men who built the PHANTEON. They too should make sure the dome will not collapse on its own weight.
Because of its gentle curve shape the edge of dome meets at a shallow angle. This Tremendous sideways pressure on the concrete foundation.
Tension rings
• If the engineers simply put the dome on the ground it would splay out and collapse.
• So like HADRIAN architects they need to use concrete tension ring to hold the walls in.
• But to contain there 12000 ton dome they need to build a huge ring which could block the access to the stadium .
• So they decide to dig down and use the surrounding bed rock to provide the extra bracing.
The engineers at OITA cannot afford such a failure like in Montreal
• So they picked a simple design, which is spherical geometry. Which allowed the easy movement of the roof which is sphere moving over a sphere.
• They wanted to build the roof in 2 section which open and close like a giant eye.
• They installed 50 trolleys to carry sections which run on rails built into the trusses and wrenched along by cables.
• A high-tech rail moving over 2000 tons of steel, Kevlar and glassfibre.
Trolley system
• The steel rails might expand due to heat and the trolley system might be thrown out of alignment and mechanism may be jammed, so they installed sensors that compare the position of trolleys on each rail and auto adjusted by computer if any of them are out of sync.
• The sliding system is bigger than 3 football pitches.
With the structural elegance and multitude of high-tech features the OITA DOME is truly an elite of its own.
• OITA DOME is the ultimate super dome in the world.
Conclusion
• Use of light weight concrete helps in reduction of overall weight
• Use of tension ring to hold the structure in place.
• Development of new techniques minimizes the use of scaffolding.
• Steel trusses can be used for long span domes.
• Use of roller supports to allow expansion and contractions.
• A good composite material can be use to cover the roof elements.
• Using modern technologies in fire prevention.
Iota today
Iota today
• On the scale of OITA the tension ring is still big.
• They reinforce the concrete tension ring . Pouring the concrete for the tension ring took 6 months .
• They embed the support for roof truss into tension with at most precision.
• Thanks to lightweight concrete and heavy weight thinking Hadrian managed to build the PHANTHEON.
oita today
• At Oita stadium Japanese engineers have also found a way to build there structure without a forest of scaffolding.
• They do most of their work on ground, they weld together hundreds of sections to form main trusses for the roof.
• But now they have to lift the sections and slot them into place.This is quiet a job where each truss can weigh up to 110tons.
• Conventionally tower cranes are used to lift the sections , but at Oita these cranes have to stretch over 300m to reach the far edges of building site. The crane with the boom this long will not be stable.
• So developers put there crane on tracks so that it can move around the site,to stop it from toppling they put a heavy counter weight at the back of the crane to lower its Centre of gravity.
Back in 1446 Brunelleschi dome for FLORENCE Cathedral pushed mortar and bricks to the limits
Iota today
• The legacy of bridge design can be seen at OITA Stadium today.
• For the roof structure at OITA engineers decided to use steel.
• Steel is strong ,can span large distances and have good strength to weight ratios.
• As OITA is 4 times bigger than the West Baden dome here simple hub and spoke design cannot be followed because it would make roof heavy so it could collapse under its own weight.
• So OITA needed clever geometry to make its roof stand up.
• 7 bridge like trusses form the core of the roof.
• A ring of steel binds the bridge trusses together.
• A huge spine truss runs the whole length of the stadium to lock all the elements to solid steel skeleton.
• Finally its strong enough to carry its 12000 tons roof.
• To lighten the whole structure hollow sections are used.
In 1902 LIAISON CLARET showed that steel was the key to make domes bigger
• Soon stadium designers began to take notice
Iota today
• Today at oita designers wanted natural grass for their field, their roof will have to let in the light without blinding the players.
• First they build the steel matrix onto which the roof membrane needs to be fixed, constructed on ground and craned into position.
• When its complete the engineers should find a material to cover it.
• They choose a sturdy glass fiber membrane coated with Teflon.
• Light rays enter the outer Teflon layer and scatter when they hit glassfibres inside, the amount of light passing through can be controlled by adjusting the density of glassfibres.
• This way they can provide a perfect condition for their pitch.
Back in 1960’s the success of Huston ASTRODOME inspired stadium designers to build much bigger domes.
But bigger crowds brought a new challenge.
Today
• Oita stadium can hold up to 43000 people so the prospect of their dome filling with smoke is terrifying.
• Because the roof can open up the smoke can disperse easily, but designers have gone a stage further which can snuff out fire with a clever system which senses infrared radiation of fires an automatically extinguished with robotic water guns.
