Civil Engineering Tips - Civil Engineering news and articles

Nicaragua Plans a Big Pacific-Atlantic Canal

The News:

On October 3 2006, Nicaraguan President Enrique Bolanos formally announced ambitious plans to construct the �Grand Inter-Oceanic Nicaragua Canal� through their country to connect Pacific and Atlantic.

Introduction:

The age old idea was revived ten years ago by a consortium of European, Japanese and North American construction giants. They carried out feasibility studies. The idea is not new. It is in the air since when the Spanish rulers and traders dreamt for the first time of having a short route to Far East and Pacific through the isthmus of the Americas.

Colonial powers� trade and imperial interests always had a special place to these sea canal short cuts. Success of Suez Canal only helped their dreams of an American Canal. So, naturally when anyone decided to give it a try, they would survey for different alignments. And Nicaragua was also considered way back in 1849 at the height of Californian Gold Rush. The Americans were desperate to cross the isthmus to reach the west with men and goods, instead of trudging past the treacherous western desert lands.

American realtors invested heavily in lands in Nicaragua in anticipation of a canal be built through it. Reportedly, the US even paid Nicaragua $3 million but the Panama Canal deal was clinched and the Nicaragua canal never took off.

What it Takes and Gives?

The inputs and time span are certainly huge, given Nicaragua Canal is going to be longer than Panama Canal. It would cost some estimated $20 billion over a minimum of 10 years. But as the Murphy�s Law says these are things that can go wrong and indeed they may go wrong. On technical side, it involves construction of 270 km canal with a draft of m and a series of giagantic locks with up to 32 metres lift to join Lago Cocibolca (Lake Nicaragua). The canal alignment mostly follows the San Juan River and also have to negotiate Mt Momotombo, an active volcano!

As if these technical and traffic difficulties are not enough, there are serious ecological concerns. It is feared that apart from destroying large areas of forest, it would also open up the interior of the most forested country in Central America to exploitation. Another certainty is the destruction of beautiful coral reefs and fishing grounds by the deep-water ports, in addition to threat to the breeding grounds of sea turtles, potential risk of pollution by oil spills and waste discharges.

The areas that would immensely benefit from it are east and west coasts of North America; a day or 800 km will be saved by Nicaragua Canal against Panama Canal. On the other hand, for Europe, Brazil large-scale sea traffic involving large ships heading for Pacific like China, Japan and South Korea would benefit. Now, the large ships are taking the Magillan Straights route as Panama canal is too narrow accommodate them. At present, Panama Canal is handling ships up to 79,000 ton only. Even after the planned upgrade, it could handle ships up to 120,000 ton only against the planned 250,000 ton for Nicaragua Canal.

It is small wonder that the formal announcement was greeted with trepidation by Panama. At a time when the Panama Canal Authority is planning a massive $5 billion project to widen its canal, Nicaragua canal could threaten its main source of income. There is speculation on whether there would be enough traffic to justify this investment. However, President Bolanos alleys these fears stating there was room for two major canals! He asserts that for every 100 ships headed for Americas, only seven were using the Panama Canal and if a Nicaraguan canal could be built much of this traffic can be attracted, resulting in great economic benefits. Officials at Panama Canal Authority maintain that there would not be enough traffic to support both a widened Panama Canal and a Nicaraguan canal.

Freedom Tower and New Plans for WTC, New York

The News:

Architects have presented striking new plans for the site of former WTC twin towers in Lower Manhattan in New York, USA. These are in addition to the freedom tower and Ground Zero.

The Background

On September 11, 2001, the majestic twin towers of WTC, which constituted the very face of the New York, the greatest city human have ever built, along with the Statue of Liberty, The Brooklyn Bridge and the Downtown Manhattan Skyline as a whole, came crashing down to the religious extremism.

Let us leave the political dissemination of extremism to other fora but the plot of 9/11 came as a rude shock to every one. The idea of using fully fuelled long distance flights filled with passengers to blast the twin towers adorning the New York skyline is somewhat perplexing, perhaps even to the hyper-creative Hollywood. It never predicted this kind of terror plot. The 9/11 struck at the root of America and its economy and forever, changed the course of nations as we can witness today.

The thousands of gallons of ATF (Aviation Turbine Fuel) burning in a few moments gave enough heat to bring down the otherwise sturdy civil engineering marvel. The building is reportedly supported on steel stanchions which melted away under intense heat, making the superstructure of tower loose. As with any multistory building, the collapsing top floors� weight and force only made it easy for the lower floors to give way. The towers came down like packs of cards within a few minutes gap.

The debris weighing thousands of tones took weeks to clear and finally, Ground Zero, the lowest level of the twin towers exposed. The site has since been preserved like a national monument. Rain or shine, American and international tourists keep pouring to this memorial every day. It witnessed an emotional fifth anniversary earlier this month.

The buildings are gone but spirit would never. In keeping with popular sentiments and obligations, the authorities decided to give a befitting answer, in the form of a still taller tower, tentatively named as the Freedom Tower in the WTC site. The Ground Zero was also retained in the scheme of things, as a memorial.

Current Plans:

Plans and design for new structure were called for soon after overcoming the trauma and clearing the site. A few plans were selected and modified. Finally they seem to zero in on one design for the freedom tower.

As per current plans, there will come three more major towers besides Freedom Tower at the 6.5 hectare WTC site by 2012. The details are given below.

The Freedom Tower: Together with the roof top antenna, it is poised to become the highest structure in the world when it is completed, with 541 m height.

Tower 2: With 78 storeys raising over 382 m, this structure designed by architect Norman Foster (Britain) will have four interconnected towers with square cross sections. Their roofs are specially designed to look as if obliquely cut by a giant knife to form diamond shaped edges and are formed to point to the memorial from the north east side.

Tower 3: Soaring to 352 m in 71 storeys, this slender building with visible brace structure lying to the east of Ground Zero, designed by Richard Rogers (Britain), will have four spires on four corners at roof top.

Tower 4: Designed by Japanese architect, Fumihiko Maki, this perforated aluminium clad building will have 61 storeys in 281 m height on the eastern edge of site.

A 228 m tall new WTC building has already been built and opened in 2006 in the extreme north. A fifth tower of almost the same height is also planned in the southern edge of the site apart from a small visitors� center and performing arts center near Ground Zero.

Besides these, A beautiful and stunningly designed winged steel ribbed and glass domed structure will be built to be used as a transit hub in the site between the towers 2 and 3.

Among all these, the footprint of the ill-fated twin towers, the Ground Zero, will not be destroyed. These two depressions will be converted into pools, located 9m below street level, amidst a 3.2 hectare memorial park being developed here.

California Scientists Test Earthquake Safety

The news:

Scientists in California, USA are experimenting with freeway overpasses for seismic safety by applying strong forces to full scale models of structures to assess their reaction and survivability of big quakes.

The background:

When the ground below the structures shakes, the otherwise strong and stable structures experience different set of forces and stresses causing it to fail. Differential settlements, failure of columns by snapping of lateral ties, collapse of un-reinforced masonry, extreme deflections rendering the structure unserviceable are a few issues.

Earlier, the shear reinforcement in structures built in seismic regions, arguably, got a raw deal. The highway overpasses, very high flyovers that criss-cross in complex patterns at intersections in cities like Los Angeles and San Francisco. With increasing knowledge of shear reinforcement failure in columns, the retrofitting of these over passes has been undertaken in a massive scale in the state of California. The retro fit may take the following components.

The size and mass of bridge footings is increased, additional piles driven and anchored securely into the ground.

Thick cables hold sections of the freeway together and secure them to the support pillars.

Support columns of existing bridges are covered with a thick coat of cement grout and a jacket of thick steel to prevent outward buckling of main steel bars and snapping or opening up of lateral ties.

Many overpasses that did not got their retrofit yet failed during the 1994 Northridge quake.

Current Efforts:

As California spends billions of dollars retrofitting freeway overpasses and public buildings, efforts were being made test to their strength in the absence of a real quake. It became imperative to conduct these tests, as the older regulations of structures failed in earthquake safety and the behaviour and survival rate of retrofitted structures is hard to predict in real terms.

Scientists are building elaborate models of freeways and office towers and testing how they would respond to extreme shaking. The Los Angeles Times has reported that researchers spent some $1 million building the foundation of a highway overpass near the Los Angeles International Airport and on put it to the test.

They gave the foundation a heavy lateral thrust of 2 million pounds (more than 900 tons) of force to assess the damage. Surprisingly, it held up the shove better than expected by moving only an inch and a half. Scientists plan to factor such data into future computer models for simulation of bridge behaviour in earthquakes.

Earlier tests include at almost full sized model testing s of every part of the new San Francisco-Oakland Bay Bridge and a seven-story custom built building on a massive shake table at UC, San Diego. These shakings are to replicate the effect of the 1994 Northridge earthquake.

The work is important not only to develop structural regulations and codes but even for architectural designs and insurance industry.

However, there is a catch. There may be huge variation in how the real soil mass and structures built on it will behave in real earthquake. Simple mathematical models based on many assumptions may just not work, particularly because the data represents only a single effort to move one piece of a complex overpass. Also, there is a question of how to correlate the magnitude earthquake with the 2 million pounds or so of force applied. More over, the structures fail not only in foundation.

What to expect?:

The bright side of the news is that Network for Earthquake Engineering Simulation, a network of 15 universities and researchers throughout the country promises on its website to "revolutionize earthquake engineering research and education�. The goal is to combine the results of engineering tests on structures with realistic tests on soil and rock under shaking, to improve the understanding of how the ground and the structures built on it will behave in earthquakes.