Sosrobahu is a
road construction technique which allows long stretches of
flyovers to be constructed above existing major roads with minimum disruption to traffic. The technique was designed and invented by Indonesian engineer
Tjokorda Raka Sukawati
Tjokorda Raka Sukawati (May 3, 1931 – November 11, 2014) was an Indonesian engineer who invented Sosrobahu. He was born and died in Ubud, Bali
Bali () is a province of Indonesia and the westernmost of the Lesser Sunda Islands. East of Jav ...
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 the 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 limited
right-of-way for new roads and the closure of existing roads throughout the flyover's construction using normal techniques would impose significant economic costs. The term ''sosrobahu'' was derived from
Old Javanese
Old Javanese or Kawi is the oldest attested phase of the Javanese language. It was spoken in the eastern part of what is now Central Java and the whole of East Java, Indonesia. As a literary language, Kawi was used across Java and on the island ...
which means "thousand shoulders".
Background
By the 1980s,
Jakarta was experiencing increased
traffic congestion
Traffic congestion is a condition in transport that is characterized by slower speeds, longer trip times, and increased vehicular queueing. Traffic congestion on urban road networks has increased substantially since the 1950s. When traffic de ...
, 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 Jalan 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
Cawang is an administrative village ('' kelurahan'' in Indonesian) at Kramat Jati subdistrict, East Jakarta. The borders of Cawang are:
* MT Haryono Road in the north
* Ciliwung River in the west
* General Sutoyo Road in the east
* Kalibata Ro ...
and
Tanjung Priok
Tanjung Priok is a district of North Jakarta, Indonesia. It hosts the western part of the city's main harbor, the Port of Tanjung Priok (located in Tanjung Priok District and Koja District). The district of Tanjung Priok is bounded by Laksamana Y ...
in 1987. The most difficult issue was the requirement to support the road with a row of concrete pylons (
pier
Seaside pleasure pier in Brighton, England. The first seaside piers were built in England in the early 19th century.">England.html" ;"title="Brighton, England">Brighton, England. The first seaside piers were built in England in the early 19th ...
shafts) apart, on top of which would sit the wide road supports. The vertical pier shafts were to be sextagonal in shape with a diameter of , 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, Tjokorda 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.
Inspiration from a hydraulic car-jack
One day Tjokorda was working on his 1974
Mercedes-Benz, 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
An axis (plural ''axes'') is an imaginary line around which an object rotates or is symmetrical. Axis may also refer to:
Mathematics
* Axis of rotation: see rotation around a fixed axis
*Axis (mathematics), a designator for a Cartesian-coordinate ...
. 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
Hydraulics (from Greek: Υδραυλική) is a technology and applied science using engineering, chemistry, and other sciences involving the mechanical properties and use of liquids. At a very basic level, hydraulics is the liquid counter ...
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
An oil is any nonpolar chemical substance that is composed primarily of hydrocarbons and is hydrophobic (does not mix with water) & lipophilic (mixes with other oils). Oils are usually flammable and surface active. Most oils are unsaturated ...
to use that would not 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 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
Lubrication is the process or technique of using a lubricant to reduce friction and wear and tear in a contact between two surfaces. The study of lubrication is a discipline in the field of tribology.
Lubrication mechanisms such as fluid-lubrica ...
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 KGF or ''kgf'' may refer to:
*Keratinocyte growth factor
*King George's Fields, UK, recreation grounds
* Kolar Gold Fields
*The IATA code for Sary-Arka Airport, Karaganda, Kazakhstan
* ''K.G.F'' (film series), Indian Kannada-language film series ...
/cm² (7.6
MPa
MPA or mPa may refer to:
Academia
Academic degrees
* Master of Performing Arts
* Master of Professional Accountancy
* Master of Public Administration
* Master of Public Affairs
Schools
* Mesa Preparatory Academy
* Morgan Park Academy
* Moun ...
), 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 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
Indonesia gave the name Sosrobahu to the new technology. The name was taken from
a character in the
Ramayana, and derives from
Old Javanese
Old Javanese or Kawi is the oldest attested phase of the Javanese language. It was spoken in the eastern part of what is now Central Java and the whole of East Java, Indonesia. As a literary language, Kawi was used across Java and on the island ...
for 'thousand shoulders'.
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
A patent is a type of intellectual property that gives its owner the legal right to exclude others from making, using, or selling an invention for a limited period of time in exchange for publishing an enabling disclosure of the invention."A p ...
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 patent 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
Metro Manila Skyway
Skyway, officially known as the Metro Manila Skyway System (MMSS), is an elevated highway which is the main expressway in Metro Manila, Philippines. It connects the North (NLEX) and South Luzon Expressways (SLEX) with access to Ninoy Aquino ...
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
ASEAN ( , ), officially the Association of Southeast Asian Nations, is a political and economic union of 10 member states in Southeast Asia, which promotes intergovernmental cooperation and facilitates economic, political, security, military ...
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
The Bandung Institute of Technology ( id, Institut Teknologi Bandung, abbreviated as ITB) is a national research university located in Bandung, Indonesia. Since its establishment in 1920, ITB has been consistently recognized as Indonesia's premier ...
, 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.
References
Further reading
"Sosrobahu Bertumpu di Atas Piring" Gatra, 21 August 2004; in Indonesian, requests payment
External links
About Sosrobahu in Indonesian
Video on Sosrobahu rotation
Hydraulic tools
Road construction
Science and technology in Indonesia
Indonesian inventions
{{portal, Engineering