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The Bandra-Worli Sea Link Now officially known as The Rajiv Gandhi Sea Link was constructed by Hindustan Construction Company, with design and project management by DAR Consultants.The Sea Link is the  project of Maharashtra State Road Development Corporation (MSRDC).The Estimated cost being Rs. 1600 crore ($ 400 million approx.)

The Sea Link was built to reduce the  travel time between Bandra and Worli from 45–60 minutes to 7 minutes.The link has an average daily traffic of around 37,500 vehicles per day, about half the pre-opening estimate of 70,000.,Although the number of vehicles is increasing in large numbers on a daily basis.

The spectacular Bandra-Worli Sea Link was opened after 10 years of expectations , delays and, of course, extensive planning and labour.The sea Link is a cable-stayed bridge with pre-stressed concrete viaduct approaches.

Highly variable geotechnical conditions,highly uneven foundation bed & Presence of Intertidal Zone were one of the main Engineering challenges in Foundation.

The Construction of  the cable stay bridges have been attempted for the first time  on open seas in India.Also,the  characteristics of the pylon tower made  it complex and challenging from the point of view of constructability.The sea-Link offers a new route between the island city and the western suburbs. Till now, the Mahim Causeway was the only route.

The sea-link is one of its kind in the Western Region,especially in Mumbai.The sea-link is guarded with a dedicated Police force,which is reinforced with a large number of all weather,multi-purpose Cameras.From the Sea,the Coast Guard Provides 24x7 Protection.

The Construction of the Sea Link is a proof to the increasing innovation & Indigenous technology adopted by the Indian Construction Industry.The Sea-link also stands as a Testimony of the never-dying Spirit of the Commercial Capital of India(Mumbai) to Progress at a Rapid rate.

The sea-link has set an example for more challenging Constructions in other Regions of the Country.The cable-stayed portion of the Bandra channel is 600 metres in overall length between expansion joints and consists of two 250-metre cable supported main spans flanked by 50 metres conventional approach spans. A centre tower, with an overall height of 128 metres above pile cap level, supports the superstructure by means of four planes of cable stay in a semi-harp arrangement. Cable spacing is 6.0 metres along the bridge deck.The cable-stayed portion of the Worli channel is 350 metres in overall length between expansion joints and consists of one 150 metres cable supported main span flanked by two 50 metres conventional approach spans. A centre tower, with an overall height of 55 metres, supports the superstructure above the pile cap level by means of four planes of cable stay in a semi-harp arrangement. Cable spacing here is also 6.0 metres along the bridge deck.The Overall Length consists of 4.7 Kilometres.

The Construction of the Sea-Link has changed the Face of Mumbai.The Sea-link brings inspiration in the minds of Indians as to the Determination,commitment & dedication of India & her citizens towards a Technologically,Economically,Enviornmentally & Socially Progressive Future.It Brings Pride to the Nation.

JAI HIND!

The Eiffel Tower is a 19th century iron lattice tower located on the Champ de Mars in Paris that has become both a global icon of France and one of the most recognizable structures in the world. The Eiffel Tower, which is the tallest building in Paris, is the single most visited paid monument in the world; millions of people ascend it every year. Named after its designer, engineer Gustave Eiffel, the tower was built as the entrance arch for the 1889 World’s Fair.

The tower stands at 324 m (1,063 ft) tall, about the same height as an 81-story building. It was the tallest structure in the world from its completion until 1930, when it was eclipsed by the Chrysler Building in New York City. Not including broadcast antennas, it is the second-tallest structure in France, behind the Millau Viaduct, just completed in 2004. And while the Eiffel Tower is a steel structure, and weighs approximately 10,000 tonnes, it actually has a relatively low density, weighing less than a cylinder of air occupying the same dimensions as the tower.

The tower has three levels for visitors. Tickets can be purchased to ascend either on stairs or lifts to the first and second levels. The walk to the first level is over 300 steps, as is the walk from the first to the second level. The third and highest level is only accessible by lift. Both the first and second levels feature restaurants.

The tower has become the most prominent symbol of both Paris and France. The tower is a featured part of the backdrop in literally scores of movies that take place in Paris. Its iconic status is so established that it even serves as a symbol for the entire nation of France, such as when it was used as the logo for the French bid to host the 1992 Summer Olympics.

The metal structure of the Eiffel Tower weighs 7,300 tonnes while the entire structure including non-metal components is approximately 10,000 tonnes. Depending on the ambient temperature, the top of the tower may shift away from the sun by up to 18 cm (7.1 in) because of thermal expansion of the metal on the side facing the sun. As demonstration of the economy of design, if the 7300 tonnes of the metal structure were melted down it would fill the 125 meter square base to a depth of only 6 cm (2.36 in), assuming a density of the metal to be 7.8 tonnes per cubic meter. The tower has a mass less than the mass of the air contained in a cylinder of the same dimensions, that is 324 meters high and 88.3 meters in radius. The weight of the tower is 10,100 tonnes compared to 10,265 tonnes of air.

At the time the tower was built many people were shocked by its daring shape. Eiffel was criticised for the design and accused of trying to create something artistic, or inartistic according to the viewer, without regard to engineering. Eiffel and his engineers, however, as renowned bridge builders, understood the importance of wind forces and knew that if they were going to build the tallest structure in the world they had to be certain it would withstand the wind. In an interview reported in the newspaper Le Temps, Eiffel said:

Now to what phenomenon did I give primary concern in designing the Tower? It was wind resistance. Well then! I hold that the curvature of the monument’s four outer edges, which is as mathematical calculation dictated it should be [...] will give a great impression of strength and beauty, for it will reveal to the eyes of the observer the boldness of the design as a whole.

The shape of the tower was therefore determined by mathematical calculation involving wind resistance. Several theories of this mathematical calculation have been proposed over the years, the most recent is a nonlinear integral differential equation based on counterbalancing the wind pressure on any point on the tower with the tension between the construction elements at that point. That shape is exponential. A careful plot of the tower curvature however, reveals two different exponentials, the lower section having a stronger resistance to wind forces. The tower sways 6–7 cm (2–3 in) in the wind.

Maintenance of the tower includes applying 50 to 60 tonnes of paint every seven years to protect it from rust.

In order to maintain a uniform appearance to an observer on the ground, three separate colors of paint are used on the tower, with the darkest on the bottom and the lightest at the top. On occasion the colour of the paint is changed; the tower is currently painted a shade of brownish-grey. On the first floor there are interactive consoles hosting a poll for the colour to use for a future session of painting.

The only non-structural elements are the four decorative grillwork arches, added in Stephen Sauvestre’s sketches, which served to reassure visitors that the structure was safe, and to frame views of other nearby architecture

The original lifts to the first and second floors were provided by two companies. Both companies had to overcome many technical obstacles as neither company (or indeed any company) had experience with installing lifts climbing to such heights with large loads. The slanting tracks with changing angles further complicated the problems. The East and West lifts were supplied by the French company Roux Combaluzier Lepape, using hydraulically powered chains and rollers. Contemporary engravings of the lift cars show that the passengers were seated at this time but it is not clear whether this was conceptual. It would be unnecessary to seat passengers for a journey time of around a couple of minutes. The North and South lifts were provided by the American Otis company using car designs similar to the original installation but using an improved hydraulic and cable scheme. The French lifts had a very poor performance and were replaced with the current installations in 1897 (West Pillar) and 1899 (East Pillar) by Fives-Lille using an improved hydraulic and rope scheme. Both of the original installations operated broadly on the principle of the Fives-Lille lifts.

The Fives-Lille lifts from ground level to the first and second levels are operated by cables and pulleys driven by massive water-powered pistons. The hydraulic scheme was somewhat unusual for the time in that it included three large counterweights of 200 tonnes each sitting on top of hydraulic rams which doubled up as accumulators for the water. As the lifts ascend the inclined arc of the pillars, the angle of ascent changes. The two lift cabs are kept more or less level and indeed are level at the landings. The cab floors do take on a slight angle at times between landings.

The principle behind the lifts is similar to the operation of a block and tackle but in reverse. Two large hydraulic rams (over 1 metre diameter) with a 16 metre travel are mounted horizontally in the base of the pillar which pushes a carriage (the French word for it translates as chariot and this term will be used henceforth to distinguish it from the lift carriage) with 16 large triple sheaves mounted on it. There are 14 similar sheaves mounted staticly. Six wire ropes are rove back and forth between the sheaves such that each rope passes between the 2 sets of sheaves 7 times. The ropes then leave the final sheaves on the chariot and passes up through a series of guiding sheaves to above the second floor and then via a pair of triple sheaves back down to the lift carriage again passing guiding sheaves.

This arrangement means that the lift carriage complete with its cars and passengers travels 8 times the distance that the rams move the chariot which is the 128 metres from the ground to the second floor. The force exerted by the rams also has to be 8 times the total weight of the lift carriage, cars and passengers plus extra to cater for various losses such as friction. The hydraulic fluid was water, normally stored in the 3 accumulators complete with counterbalance weights. To make the lift ascend, water was pumped using an electrically driven pump from the accumulators to the two rams. Since the counterbalance weights provided much of the pressure required, the pump only had to provide the extra effort. For the descent, it was only necessary to allow the water to flow back to the accumulators using a control valve. The lifts were operated by an operator perched precariously underneath the lift cars. His position (with a dummy operator) can still be seen on the lifts today.

The Fives-Lille lifts were completely upgraded in 1986 to meet modern safety requirements and to make the lifts easier to operate. A new computer controlled system was installed which completely automated the operation. One of the three counterbalances was taken out of use, and the cars were replaced with a more modern and lighter structure. Most importantly, the main driving force was removed from the original water pump such that the water hydraulic system provided only a counterbalancing function. The main driving force was transferred to a 320 kW electrically driven oil hydraulic pump which drives a pair of hydraulic motors on the chariot itself thus providing the motive power. The new lift cars complete with their carriage and a full 92 passenger load weigh 22 tonnes.

Due to elasticity in the ropes and the time taken to get the cars level with the landings, each lift in normal service takes an average of 8 minutes and 50 seconds to do the round trip spending an average of 1 minute and 15 seconds at each floor. The average journey time between floors is just 1 minute.

The original Otis lifts in the North and South pillars in their turn proved inferior to the new (in 1899) French lifts and were scrapped from the south pillar in 1900 and from the north pillar in 1913 after failed attempts to re-power them with an electric motor. The north and south pillars were to remain without lifts until 1965 when increasing visitor numbers persuaded the operators to install a relatively standard and modern rope hoisted system in the north pillar using a rope hauled counterbalance weight, but hoisted by a block and tackle system to reduce its travel to one third of the lift travel. The counterbalance is clearly visible within the structure of the North pillar. This latter lift was upgraded in 1995 with new cars and computer controls.

The South tower acquired a completely new fairly standard electrically driven lift in 1983 to serve the Jules Verne restaurant. This was also supplied by Otis.

A further 4 tonne service lift was added to the south pillar in 1989 by Otis to relieve the main lifts when moving relatively small loads or even just maintenance personnel.

The east and west hydraulic (water) lift works are on display and, at least in theory, are open to the public in a small museum located in base of the East and West tower, which is somewhat hidden from public view. Because the massive mechanism requires frequent lubrication and attention, public access is often restricted. However, when open, the wait times are much less than the other, more popular, attractions. The rope mechanism of the North tower is visible to visitors as they exit from the lift.

The original lift from the second to the third floor were also of a water powered hydraulic design supplied by Léon Edoux. Instead of using a separate counterbalance, the two lift cars counterbalanced each other. A pair of 81 metre long hydraulic rams were mounted on the second level reaching nearly half way up to the third level. A lift car was mounted on top of the rams. Ropes ran from the top of this car up to a sheave on the third level and back down to a second car. The result of this arrangement was that each car only travelled half the distance between the second and third levels and passengers were required to change lifts halfway walking between the cars along a narrow gangway with a very impressive and relatively unobstructed downward view. The 10 tonne cars held 65 passengers each or up to 4 tonnes.

One interesting feature of the original installation was that the hoisting rope ran through guides to retain it on windy days to prevent it flapping and becoming damaged. The guides were mechanically moved out of the way of the ascending car by the movement of the car itself. In spite of some antifreeze being added to the water that operated this system, it nevertheless had to close to the public from November to March each year.

The original lifts complete with their hydraulic mechanism were completely scrapped in 1982 after 97 years of service. They were replaced with two pairs of relatively standard rope hoisted cars which were able to operate all the year round. The cars operate in pairs with one providing the counterbalance for the other. Neither car can move unless both sets of doors are closed and both operators have given a start command. The commands from the cars to the hoisting mechanism are by radio obviating the necessity of a control cable. The replacement installation also has the advantage that the ascent can be made without changing cars and has reduced the ascent time from 8 minutes (including change) to 1 minute and 40 seconds. This installation also has guides for the hoisting ropes but they are electrically operated. The guide once it has moved out of the way as the car ascends automatically reverses when the car has passed to prevent the mechanism becoming snagged on the car on the downward journey in the event it has failed to completely clear the car. Unfortunately these lifts do not have the capacity to move as many people as the 3 public lower lifts and long queues to ascend to the third level are common. Most of the intermediate level structure present on the tower today was installed when the lifts were replaced and allows maintenance workers to take the lift half way.

The replacement of these lifts allowed the restructuring of the criss-cross beams in upper part of the tower and further allowed the installation of two emergency staircases. These replaced the dangerous winding stairs that were installed when the tower was constructed.

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