Sosrobahu
Encyclopedia
Sosrobahu is a construction
technique which allows long stretches of flyovers
to be constructed above existing main roads with a minimum of disruption to traffic
. The technique was designed by Tjokorda Raka Sukawati
and involves the construction of the horizontal supports for the highway beside the existing road, which are then lifted and turned 90 degrees before being placed on top of the vertical supports to form the flyover pylons.
This technique is of considerable value in increasing road mileage in large cities where there is restricted space for new roads and where the closure of existing roads for the length of time to build a flyover using normal construction techniques would impose significant economic costs.
was experiencing increased traffic congestion
, and flyovers were seen as one solution to the improving transport infrastructure. One construction company operating at that time was PT Hutama Karya, which was granted a contract to build a highway above bypass A Yani, an extremely important stretch of highway
where it was vital that the road would continue to be open to traffic throughout the period of construction.
In addition to this challenge, PT Hutama Karya were also granted a contract
to build a flyover between Cawang
and Tanjung Priok
in 1987. The most difficult issue was the requirement to support the road with a row of concrete pylons (pier shafts) 30 m apart, on top of which would sit the 22 m wide road supports. The vertical
pier shafts were to be sextagonal in shape with a diameter of 4 m, and were to sit in the central lane of the existing road. The erection of the pier shafts was not difficult; what caused problems were the poured concrete
pier heads. With conventional construction techniques, the pier heads would be moved into place with the help of iron
supports beneath the outspread pier heads, but the use of iron supports would necessitate the closure of the road below. Another option was to support the pier heads from above, but this increased the costs of the project.
In response to these problems, Sukawati had the idea of initially erecting the concrete pier shafts and then building the poured concrete pier heads in the centre lane, parallel
to the existing roadway, and then raising and turning the pier heads 90 degrees into place. The only problem with this idea was that the pier heads weigh approximately 480 tonnes each.
, which he had jacked up so that the back two wheels
were supported on the slippery floor of the garage where some oil had been accidentally spilled. When the car was pushed, it pivoted with the jack as the axis. He noted that it is a principle
of physics
that when friction
is banished it is easy to move even the heaviest of objects.
This event inspired the realization that a hydraulic pump could be used to lift heavy objects and, as long as they were supported by something slippery, the heavy objects could be easily moved. Tjokorda's goal was to lift and move concrete pier heads each weighing 480 tonnes.
Tjokorda conducted trials with cylinders 20 cm in diameter converted into a hydraulic lift and loaded with 80 tonnes of concrete. The weight was successfully lifted and turned slightly, but could not then be lowered as the position of the hydraulic jack had shifted. Tjokorda then made some improvements on the original design
, and in subsequent lifts the hydraulic jack stayed stable even with the full weight of the concrete above it.
Other problems to be overcome included establishing the best type of oil
to use that wouldn't lose its viscosity
. The type of oil was a critical factor because it was the oil which transmitted the force
required to lift the heavy concrete pier heads.
After the trials, Tjokorda finalised his design called the LBPH (the Indonesian acronym for Free Moving Platform) which consisted of a two concrete discs with a diameter of 80 cm enclosed in a container. Although only 5 cm thick, the discs are capable of supporting a weight of 625 tonnes each.
Between the two plates is pumped lubricating oil. A rubber
seal around the edges of the plates protected against the oil escaping under the high forces experienced during the lift. The oil in the container was connected to a hydraulic pump through a small pipe
. This hydraulic system was capable of lifting loads using a pressure of 78 kgf
/cm² (7.6 MPa, although the reasons for this were a mystery to Tjokorda at that time.
On the 27 July 1988 at 22:00 Jakarta time, the hydraulic pump was pressurized to 78 kgf/cm² (7.6 MPa). The pier head, despite lack of iron supports, was lifted and placed on top of the pier shaft and then with a light push was turned 90 degrees into its final position. The oil was then slowly pumped out and the pier head was lowered onto the shaft. The LPBH system was then shut down as it required heavy machinery to move it. Because he was worried that the single pier shaft and head might shift for a lack of support, he propped them up with eight concrete supports, 3.6 m in diameter. The LPBH was then used to raise the other pier heads over their respective shafts.
gave the name Sosrobahu to the new technology. The name was taken from a character in the Mahabharata
, and derives from Old Javanese for thousand (sosro) shoulders (bahu).
Tjokorda's invention
was used by US engineers in the construction of a bridge in Seattle. They placed the oil under a pressure of 78 kg/cm² (7.6 MPa) as per Tjokorda's original theories. Tjokorda himself wanted to investigate further the limits of his invention and built himself a laboratory where he successfully tested the LPBH to a limit of 78.05 kgf/cm² (7.654 MPa).
Patents have been granted for the invention from Indonesia, Japan
, Malaysia, and the Philippines
, and has been applied for in South Korea
. The Indonesian patent was granted in 1995, while the Japanese patient was granted in 1992. The technology has been exported to the Philippines, Malaysia, Thailand
and Singapore
. The longest stretch of overpass built using this technique is in Metro Manila
, Philippines
at the Villamor/Bicutan link located at the southern part of the metropolis. In the Philippines, 298 supports have been erected, while in Kuala Lumpur
, the figure is 135. When the technology was introduced to the Philippines, the President of the Philippines, Fidel Ramos commented: "This is an Indonesian invention, but is also an ASEAN invention".
A second version of the technology has been developed. Whereas the first version used a steel anchor inserted in a concrete base, the second version uses a single plate with a hole in the middle which is not only simpler, but also significantly speeds up the time it takes to erect a pylon from 2 days to 45 minutes. It is expected that the lifespan of flyovers constructed using the Sosrobahu method will be approximately 100 years.
According to Dr. Drajat Hoedajanto, an expert from the Bandung Institute of Technology
, Sosrobahu is a very simple solution to the problem of erecting flyover pylons and is suitable for use in the construction of elevated toll roads which have traffic running underneath them. Sosrobahu is clearly a useful and versatile technology.
Construction
In the fields of architecture and civil engineering, construction is a process that consists of the building or assembling of infrastructure. Far from being a single activity, large scale construction is a feat of human multitasking...
technique which allows long stretches of flyovers
Overpass
An overpass is a bridge, road, railway or similar structure that crosses over another road or railway...
to be constructed above existing main roads with a minimum of disruption to traffic
Traffic
Traffic on roads may consist of pedestrians, ridden or herded animals, vehicles, streetcars and other conveyances, either singly or together, while using the public way for purposes of travel...
. The technique was designed by Tjokorda Raka Sukawati
Tjokorda Raka Sukawati
Tjokorda Raka Sukawati is an Indonesian engineer who invented Sosrobahu.-External links: at kamusilmiah.com at jakarta.go.id...
and involves the construction of the horizontal supports for the highway beside the existing road, which are then lifted and turned 90 degrees before being placed on top of the vertical supports to form the flyover pylons.
This technique is of considerable value in increasing road mileage in large cities where there is restricted space for new roads and where the closure of existing roads for the length of time to build a flyover using normal construction techniques would impose significant economic costs.
Background
By the 1980s, JakartaJakarta
Jakarta is the capital and largest city of Indonesia. Officially known as the Special Capital Territory of Jakarta, it is located on the northwest coast of Java, has an area of , and a population of 9,580,000. Jakarta is the country's economic, cultural and political centre...
was experiencing increased traffic congestion
Traffic congestion
Traffic congestion is a condition on road networks that occurs as use increases, and is characterized by slower speeds, longer trip times, and increased vehicular queueing. The most common example is the physical use of roads by vehicles. When traffic demand is great enough that the interaction...
, and flyovers were seen as one solution to the improving transport infrastructure. One construction company operating at that time was PT Hutama Karya, which was granted a contract to build a highway above bypass A Yani, an extremely important stretch of highway
Highway
A highway is any public road. In American English, the term is common and almost always designates major roads. In British English, the term designates any road open to the public. Any interconnected set of highways can be variously referred to as a "highway system", a "highway network", or a...
where it was vital that the road would continue to be open to traffic throughout the period of construction.
In addition to this challenge, PT Hutama Karya were also granted a contract
Contract
A contract is an agreement entered into by two parties or more with the intention of creating a legal obligation, which may have elements in writing. Contracts can be made orally. The remedy for breach of contract can be "damages" or compensation of money. In equity, the remedy can be specific...
to build a flyover between Cawang
Cawang
Cawang is administrative village at Kramat Jati subdistrict, North Jakarta. The border of Cawang are :* MT Haryono Street in the north* Ciliwung River in the west* General Sutoyo Street in the east...
and Tanjung Priok
Tanjung Priok
Tanjung Priok is a subdistrict of North Jakarta, Jakarta, Indonesia. It hosts the western part of the city's main harbour, the Port of Tanjung Priok...
in 1987. The most difficult issue was the requirement to support the road with a row of concrete pylons (pier shafts) 30 m apart, on top of which would sit the 22 m wide road supports. The vertical
Vertical direction
In astronomy, geography, geometry and related sciences and contexts, a direction passing by a given point is said to be vertical if it is locally aligned with the gradient of the gravity field, i.e., with the direction of the gravitational force at that point...
pier shafts were to be sextagonal in shape with a diameter of 4 m, and were to sit in the central lane of the existing road. The erection of the pier shafts was not difficult; what caused problems were the poured concrete
Concrete
Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...
pier heads. With conventional construction techniques, the pier heads would be moved into place with the help of iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
supports beneath the outspread pier heads, but the use of iron supports would necessitate the closure of the road below. Another option was to support the pier heads from above, but this increased the costs of the project.
In response to these problems, Sukawati had the idea of initially erecting the concrete pier shafts and then building the poured concrete pier heads in the centre lane, parallel
Parallel (geometry)
Parallelism is a term in geometry and in everyday life that refers to a property in Euclidean space of two or more lines or planes, or a combination of these. The assumed existence and properties of parallel lines are the basis of Euclid's parallel postulate. Two lines in a plane that do not...
to the existing roadway, and then raising and turning the pier heads 90 degrees into place. The only problem with this idea was that the pier heads weigh approximately 480 tonnes each.
Inspiration from a hydraulic car-jack
One day Tjokorda was working on his 1974 Mercedes-BenzMercedes-Benz
Mercedes-Benz is a German manufacturer of automobiles, buses, coaches, and trucks. Mercedes-Benz is a division of its parent company, Daimler AG...
, which he had jacked up so that the back two wheels
Wheel
A wheel is a device that allows heavy objects to be moved easily through rotating on an axle through its center, facilitating movement or transportation while supporting a load, or performing labor in machines. Common examples found in transport applications. A wheel, together with an axle,...
were supported on the slippery floor of the garage where some oil had been accidentally spilled. When the car was pushed, it pivoted with the jack as the axis. He noted that it is a principle
Principle
A principle is a law or rule that has to be, or usually is to be followed, or can be desirably followed, or is an inevitable consequence of something, such as the laws observed in nature or the way that a system is constructed...
of physics
Physics
Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...
that when friction
Friction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and/or material elements sliding against each other. There are several types of friction:...
is banished it is easy to move even the heaviest of objects.
This event inspired the realization that a hydraulic pump could be used to lift heavy objects and, as long as they were supported by something slippery, the heavy objects could be easily moved. Tjokorda's goal was to lift and move concrete pier heads each weighing 480 tonnes.
Tjokorda conducted trials with cylinders 20 cm in diameter converted into a hydraulic lift and loaded with 80 tonnes of concrete. The weight was successfully lifted and turned slightly, but could not then be lowered as the position of the hydraulic jack had shifted. Tjokorda then made some improvements on the original design
Design
Design as a noun informally refers to a plan or convention for the construction of an object or a system while “to design” refers to making this plan...
, and in subsequent lifts the hydraulic jack stayed stable even with the full weight of the concrete above it.
Other problems to be overcome included establishing the best type of oil
Oil
An oil is any substance that is liquid at ambient temperatures and does not mix with water but may mix with other oils and organic solvents. This general definition includes vegetable oils, volatile essential oils, petrochemical oils, and synthetic oils....
to use that wouldn't lose its viscosity
Viscosity
Viscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...
. The type of oil was a critical factor because it was the oil which transmitted the force
Force
In physics, a force is any influence that causes an object to undergo a change in speed, a change in direction, or a change in shape. In other words, a force is that which can cause an object with mass to change its velocity , i.e., to accelerate, or which can cause a flexible object to deform...
required to lift the heavy concrete pier heads.
After the trials, Tjokorda finalised his design called the LBPH (the Indonesian acronym for Free Moving Platform) which consisted of a two concrete discs with a diameter of 80 cm enclosed in a container. Although only 5 cm thick, the discs are capable of supporting a weight of 625 tonnes each.
Between the two plates is pumped lubricating oil. A rubber
Rubber
Natural rubber, also called India rubber or caoutchouc, is an elastomer that was originally derived from latex, a milky colloid produced by some plants. The plants would be ‘tapped’, that is, an incision made into the bark of the tree and the sticky, milk colored latex sap collected and refined...
seal around the edges of the plates protected against the oil escaping under the high forces experienced during the lift. The oil in the container was connected to a hydraulic pump through a small pipe
Pipe (material)
A pipe is a tubular section or hollow cylinder, usually but not necessarily of circular cross-section, used mainly to convey substances which can flow — liquids and gases , slurries, powders, masses of small solids...
. This hydraulic system was capable of lifting loads using a pressure of 78 kgf
Kilogram-force
A kilogram-force , or kilopond , is a gravitational metric unit of force. It is equal to the magnitude of the force exerted by one kilogram of mass in a gravitational field...
/cm² (7.6 MPa, although the reasons for this were a mystery to Tjokorda at that time.
Field trials
The new technique had not yet been trialled because of time constraints, however Tjokorda was certain that it would work and was willing to bear the responsibility should the concrete pier heads not be able to be turned 90 degrees as required for the construction of the flyover.On the 27 July 1988 at 22:00 Jakarta time, the hydraulic pump was pressurized to 78 kgf/cm² (7.6 MPa). The pier head, despite lack of iron supports, was lifted and placed on top of the pier shaft and then with a light push was turned 90 degrees into its final position. The oil was then slowly pumped out and the pier head was lowered onto the shaft. The LPBH system was then shut down as it required heavy machinery to move it. Because he was worried that the single pier shaft and head might shift for a lack of support, he propped them up with eight concrete supports, 3.6 m in diameter. The LPBH was then used to raise the other pier heads over their respective shafts.
Naming the technique and the granting of a patent
In November 1989, President Soeharto of IndonesiaIndonesia
Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...
gave the name Sosrobahu to the new technology. The name was taken from a character in the Mahabharata
Mahabharata
The Mahabharata is one of the two major Sanskrit epics of ancient India and Nepal, the other being the Ramayana. The epic is part of itihasa....
, and derives from Old Javanese for thousand (sosro) shoulders (bahu).
Tjokorda's invention
Invention
An invention is a novel composition, device, or process. An invention may be derived from a pre-existing model or idea, or it could be independently conceived, in which case it may be a radical breakthrough. In addition, there is cultural invention, which is an innovative set of useful social...
was used by US engineers in the construction of a bridge in Seattle. They placed the oil under a pressure of 78 kg/cm² (7.6 MPa) as per Tjokorda's original theories. Tjokorda himself wanted to investigate further the limits of his invention and built himself a laboratory where he successfully tested the LPBH to a limit of 78.05 kgf/cm² (7.654 MPa).
Patents have been granted for the invention from Indonesia, Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
, Malaysia, and the Philippines
Philippines
The Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam...
, and has been applied for in South Korea
South Korea
The Republic of Korea , , is a sovereign state in East Asia, located on the southern portion of the Korean Peninsula. It is neighbored by the People's Republic of China to the west, Japan to the east, North Korea to the north, and the East China Sea and Republic of China to the south...
. The Indonesian patent was granted in 1995, while the Japanese patient was granted in 1992. The technology has been exported to the Philippines, Malaysia, Thailand
Thailand
Thailand , officially the Kingdom of Thailand , formerly known as Siam , is a country located at the centre of the Indochina peninsula and Southeast Asia. It is bordered to the north by Burma and Laos, to the east by Laos and Cambodia, to the south by the Gulf of Thailand and Malaysia, and to the...
and Singapore
Singapore
Singapore , officially the Republic of Singapore, is a Southeast Asian city-state off the southern tip of the Malay Peninsula, north of the equator. An island country made up of 63 islands, it is separated from Malaysia by the Straits of Johor to its north and from Indonesia's Riau Islands by the...
. The longest stretch of overpass built using this technique is in Metro Manila
Metro Manila
Metropolitan Manila , the National Capital Region , or simply Metro Manila, is the metropolitan region encompassing the City of Manila and its surrounding areas in the Philippines...
, Philippines
Philippines
The Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam...
at the Villamor/Bicutan link located at the southern part of the metropolis. In the Philippines, 298 supports have been erected, while in Kuala Lumpur
Kuala Lumpur
Kuala Lumpur is the capital and the second largest city in Malaysia by population. The city proper, making up an area of , has a population of 1.4 million as of 2010. Greater Kuala Lumpur, also known as the Klang Valley, is an urban agglomeration of 7.2 million...
, the figure is 135. When the technology was introduced to the Philippines, the President of the Philippines, Fidel Ramos commented: "This is an Indonesian invention, but is also an ASEAN invention".
A second version of the technology has been developed. Whereas the first version used a steel anchor inserted in a concrete base, the second version uses a single plate with a hole in the middle which is not only simpler, but also significantly speeds up the time it takes to erect a pylon from 2 days to 45 minutes. It is expected that the lifespan of flyovers constructed using the Sosrobahu method will be approximately 100 years.
According to Dr. Drajat Hoedajanto, an expert from the Bandung Institute of Technology
Bandung Institute of Technology
The Bandung Institute of Technology or Institute of Technology, Bandung is a state, coeducational research university located in Bandung, Indonesia. Established in 1920, ITB is the oldest technology-oriented university in Indonesia....
, Sosrobahu is a very simple solution to the problem of erecting flyover pylons and is suitable for use in the construction of elevated toll roads which have traffic running underneath them. Sosrobahu is clearly a useful and versatile technology.
Sources
"Sosrobahu Bertumpu di Atas Piring", Gatra Magazine, 21 August 2004; in Indonesian, requests paymentExternal links
- About Sosrobahu; in Indonesian
- Posting on the SkyscraperCity Forum with diagram; in Indonesian
- About Tjokorda Raka Sukawati and Sosrobahu; in Indonesian