The Chinese — Three Gorges Dam

The Three Gorges Dam is a hydroelectric dam that spans the Yangtze River by the town of Sandouping, located in Yiling District,Yichang, Hubei province, China. The Three Gorges Dam is the world’s largest power station in terms of installed capacity(22,500 MW). The dam is the largest operating hydroelectric facility in terms of annual energy generation, generating 83.7 TWh in 2013 and 98.8 TWh in 2014, while the annual energy generation of the Itaipú Dam in Brazil and Paraguay was 98.6 TWh in 2013 and 87.8 in 2014.  

IMAGE OF THE THREE GORGES DAM WITH OPEN FLOOD GATES

Being the world’s largest hydropower project, this dam has created many “Firsts” such as the   

• Most efficient dam in flood control
• The most difficult construction work
• The largest migration project in the world.

CONSTRUCTION

The dam project is composed of the dam, the hydropower stations and the navigation facility. It measures 607 feet tall and the top is 3,319 yards wide. It has taken 17 years to finish the construction of the whole project, which started in 1992 and includes three stages.  

1. The first stage took five years from 1992 to 1997. During this period, the cofferdam construction and the excavation of a diversion channel in the first stage were finished. Meanwhile, a temporary ship lock on the left bank of the river and some preparation work was also completed.
2.  The second stage lasted six years from 1998 to 2003, was undertaken at the same time as the construction of the permanent ship lock and the navigation buildings. The power station facilities construction and the installation of machinery on the left bank were also completed.
3.  The third stage of the project began in 2003 and has been completed in 2009. During this period, the installation of all machinery, the construction of the power station and the dam on the right bank are finished. Now, a 3,861 square miles canyon-reservoir dam is presented to the world.

MAP SHOWING THE LOCATION OF THE DAM

 

Layout of Three Gorges Dam

Spillway

The Three Gorges Project is designed with a concrete gravity dam with a crest elevation of 185 meters and maximum height of 175 meters. The dam axis runs 2, 309. 47 meters long, which is even longer than the noted Grand Coulee Dam of US.

• The 483-meter spillway, located in the middle of the main dam, has 23 bottom outlets dimensioned at 79 meters. Each of its 22 surface sluice gates measures 8 meters wide. The maximum discharge capacity of the TGP is 116,000 cubic meters, the biggest in the world.
• Left Powerhouse Two powerhouses, flanking the spillway, accommodate altogether 26 sets of turbine-generators. As the world’s biggest unit ever made, each has a generating capacity of 700MW. The 643.6-meter-long left powerhouse, 60 meters longer than the 584.2-meter-long right one, houses 14 sets of generators. With all these huge generators, the TGP is designed to generate electricity of 84.7 TW/h.

 

BENEFITS OF THREE GORGES DAM

POWER GENERATION   Hydropower is clean energy and environmental friendly. The operation of the Three Gorges hydropower station can reduce the emissions of ten million tons of carbon dioxide, one to two million tons of sulfur dioxide, 300,000 to 400,000 tons of oxynitride, 10,000 tons of carbon monoxide and 150,000 tons of dust.The total capacity of the Three Gorges Dam Project is 18.2 million kilowatts and the annual power generation is 84.7 billion kilowatt hours, which greatly relieves the electricity pressure in middle and eastern China.   NAVIGATION
Located in the middle reach of Yangtze River, the Three Gorges Dam will largely improve the waterway conditions from Yichang City to Chongqing City. In the dry season, the water in the lower reaches of Gezhouba Water Control Project can get ample supply, and the navigation in the upper and middle reaches of Yangtze River will be well developed.   TOURISM   After the completion of the dam project, visitors will be delighted to see a wonder in the Yangtze River where a calm lake sits among the steep gorges      

PROBLEMS CAUSED BY GORGES DAM

    SEDIMENT PROBLEM
Sediment problem is always a heavy emphasis on the discussion of the Three Gorges Project. It is measured that the river sediment concentration of the upper stream is about 1.2kg per cubic meter. The total sediment passing the dam site is above five hundred million a year. Before the dam project, the mud and sand deposited largely in Jingjiang River, which has lifted the water level and menaced the safety of Jianghan (Yangtze River and Hanjiang River) Plain and Dongting Lake Plain   ENVIRONMENTAL PROBLEM   The Three Gorges Project has a great influence on the environment and ecology of the reservoir area and the Yangtze River. The biggest concern is the pollution of the reservoir. After the water storage, due to the steady state of the fluent, the contaminant cannot down rush in time and store up in the reservoir, which would deteriorate water quality and cause refuse floating, and probably trigger the epidemic. At present, some towns have started collecting potable water in other area, and while a great number of migrants are opening up the wasteland, the soil erosion and water pollution are growing in intensity.   MIGRATION PROBLEM   Migration problem is the biggest difficult point of the Three Gorges Dam Project. The fund for migration covers 45% of the total investment. After the water storage, about 129 cities and towns including Wanxian and Fuling are flooded. The migrants surpass 1200,000, relating to 20 cities and counties in Hubei and Chongqing. They were allocated to Hubei (outside the reservoir area), Chongqing (outside the reservoir area), Anhui, Hunan, Sichuan, Jiangxi, Jiangsu, Zhejiang, Shanghai, Fujian and Guangdong provinces to make a living.   LANDSCAPE LOSS    the water storage of the Three Gorges Dam, the rising Yangtze River has flooded a part of the landscape. Scenery changes a lot compared before the dam construction. According to a survey, the flooded natural scenery includes Military Books and Precious Sword Gorge, Dragon Gate Gorge, Ox Liver and Horse Lung Gorge, Hanging Monk Rock, Bayan Gorge, Guandao Gorge, Water Curtain Cave and Phoenix Spring. The flooded cultural sights include Quyuan Temple, White Crane Ridge, Daxi Culture, Zhangfei Temple, Dachang ancient city, Fengjie ancient city, Kongming Tablet, Chalk Wall, Mengliang Stairway, Dragon Backbone Stone and Qutang Gorge ancient plank road. The partly submerged natural landscape includes Bawu Gorge, Dicui Gorge, Wu Gorge, Qutang Gorge, Kongdong Gorge and Luyou Cave. 

FOR VIDEO SHOWING THE CONSTRUCTION CLICK HERE

WORLD’S TALLEST BRIDGE

 THE MILLAU VIADUCT

Located in Southern France, the Millau Viaduct is the tallest bridge in the world. Constructed in three short years, the bridge is an engineering and architectural marvel. At its highest point, the bridge soars 343 meters (1,125 ft) above ground, that’s 19 meters (62 ft) taller than the Eiffer Tower!

This is a cable stayed bridge.

THE MILLAU VIADUCT – RECORD FIGURES
Length: 2,460 m (8,071 ft)
Width: 32 m (105 ft)
Maximum height: 343 m (1,125 ft), or 19 m higher than the Eiffel Tower
Slope: 3.025 %, going up from north to south in the direction Clermont-Ferrand – Béziers
Curve: 20 km (12.4 miles)
Height of the tallest pier (P2): 245 m (804 ft)
Height of the pylons: 87 m (285 ft)
Number of piers: 7
Length of the spans: Two end spans of 204 m (669 ft) each and six central spans of 342 m (1,122 ft) each.
Number of stays: 154 (11 pairs per pylon laid out in one mono-axial layer)
Tension of the stays: from 900 t to 1,200 t for the longest
Weight of the steel deck: 36,000 t, or 5 times that of the Eiffel Tower
Volume of concrete: 85,000 m3, or 206,000 t
Cost of the construction: 400 Million Euros (585 m USD)
Contract duration: 78 years – 3 years for construction and 75 years of operations
Structural guarantee: 120 years

CONSTRUCTION

Raising the piersBridge rests on 7 piers the highest of which rises upto 245 meters.
Throwing the deckEighteen sliding operations brought the two parts of the deck together above the tarn.
Joining the deckThen the decks were joined and happened successfully. This was the first time where throwing the deck technique was used to make the deck as lifting the deck was not possible to such a height.
Installing the pylonsThe pylons were brought to the deck lying on their sides by four self propelled trailers.The staysEleven pairs of stays were installed face to face on each pylons inside the protective sheaths, several dozen steel strands were placed under tension.
The finishingThen the finishing touch was given to the bridge like street lights and was opened for traffic.

The bridge received the 2006 International Association for Bridge and Structural Engineering Outstanding Structure Award.

THE TALLEST MARVEL BUILT

BURJ KHALIFA

It is the tallest artificial structure in the world, standing at 829.8 m (2,722 ft)building gained the official title of “Tallest Building in the World” at its opening on January 4, 2010. It is followed by the Tokyo Skytree, as the tallest tower, and the KVLY-TV mast.

DESIGNING THE TALLEST STRUCTURE

ARCHITECTURE

The architecture features a triple-lobed footprint, an abstraction of the Hymenocallis flower. The tower is composed of three elements arranged around a central core. The modular, Y-shaped structure, with setbacks along each of its three wings provides an inherently stable configuration for the structure and provides good floor plates for residential. Twenty-six helical levels decrease the cross section of the tower incrementally as it spirals skyward.

The central core emerges at the top and culminates in a sculpted spire. A Y-shaped floor plan maximizes views of the Arabian Gulf. Viewed from the base or the air, Burj Khalifa is evocative of the onion domes prevalent in Islamic architecture.

WIND TUNNEL TESTING

Over 40 wind tunnel tests were conducted on Burj Khalifa to examine the effects the wind would have on the tower and its occupants. These ranged from initial tests to verify the wind climate of Dubai, to large structural analysis models and facade pressure tests, to micro-climate analysis of the effects at terraces and around the tower base. Even the temporary conditions during the construction stage were tested with the tower cranes on the tower to ensure safety at all times.

Stack effect or chimney effect is a phenomenon that effects super-tall building design, and arises from the changes in pressure and temperature with height. Special studies were carried on Burj Khalifa to determine the magnitude of the changes that would have to be dealt with in the building design.

FLOOR PLAN

Concourse level to level 8 and level 38 and 39 will feature the Armani Hotel Dubai. Levels 9 to 16 will exclusively house luxurious one and two bedroom Armani Residences.

Floors 45 through 108 are private ultra-luxury residences. The Corporate Suites occupy fill most of the remaining floors, except for level 122 which houses At.mosphere and level 124, the tower’s public observatory, At the Top, Burj Khalifa.

For the convenience of home owners, the tower has been divided in to sections with exclusive Sky Lobbies on Levels 43, 76 and 123 that feature state-of-the-art fitness facilities including a Jacuzzis on Level 43 and 76. The Sky Lobbies on 43 and 76 additionally house swimming pools and a recreational room each that can be utilized for gatherings and lifestyle events. Offering an unparalleled experience, both pools open to the outside offering residents the option of swimming from inside to the outside balcony.

Other facilities for residents include a Residents’ Library, and Lafayette Gourmet, a gourmet convenience store and meeting place for the residents. Valet parking is provided for guests and visitors.

CONSTRUCTION OF THE MARVEL

Over 45,000 m3 (58,900 cu yd) of concrete, weighing more than 110,000 tonnes were used to construct the concrete and steel foundation, which features 192 piles buried more than 50 m (164 ft) deep. Burj Khalifa’s construction will have used 330,000 m3 (431,600 cu yd) of concrete and 39,000 tonnes (43,000 ST; 38,000 LT) of steel rebar, and construction will have taken 22 million man-hours.

Exterior cladding of Burj Khalifa was a vast project involving more than 380 skilled engineers and on-site technicians. At the initial stage of installation, the team progressed at the rate of about 20 to 30 panels per day and eventually achieved as many as 175 panels per day.

The tower accomplished a world record for the highest installation of an aluminium and glass façade, at a height of 512 metres. The total weight of aluminium used  is equivalent to that of five A380 aircraft and the total length of stainless steel bull nose fins is 293 times the height of Eiffel Tower in Paris.

The highest reinforced concrete corewalls were pumped using 80 MPa concrete from ground level; a vertical height of 601 metres. Smashing the previous pumping record on a building of 470m on the Taipei 101; the world’s second tallest tower and the previous world record for vertical pumping of 532 metres for an extension to the Riva del Garda Hydroelectric Power Plant in 1994. The concrete pressure during pumping to this level was nearly 200 bars.

The amount of rebar used for the tower is 31,400 metric tons – laid end to end this would extend over a quarter of the way around the world.

Foundation

The superstructure is supported by a large reinforced concrete mat, which is in turn supported by bored reinforced concrete piles. The design was based on extensive geotechnical and seismic studies. The mat is 3.7 meters thick, and was constructed in four separate pours totaling 12,500 cubic meters of concrete. The 1.5 meter diameter x 43 meter long piles represent the largest and longest piles conventionally available in the region. A high density, low permeability concrete was used in the foundations, as well as a cathodic protection system under the mat, to minimize any detrimental effects form corrosive chemicals in local ground water.

Exterior Cladding

The exterior cladding is comprised of reflective glazing with aluminum and textured stainless steel spandrel panels and stainless steel vertical tubular fins. Close to 26,000 glass panels, each individually hand-cut, were used in the exterior cladding of Burj Khalifa. Over 300 cladding specialists from China were brought in for the cladding work on the tower. The cladding system is designed to withstand Dubai’s extreme summer heat, and to further ensure its integrity, a World War II airplane engine was used for dynamic wind and water testing. The curtain wall of Burj Khalifa is equivalent to 17 football (soccer) fields or 25 American football fields.

Structural System

In addition to its aesthetic and functional advantages, the spiraling “Y” shaped plan was utilized to shape the structural core of Burj Khalifa.  This design helps to reduce the wind forces on the tower, as well as to keep the structure simple and foster constructability. The structural system can be described as a “buttressed core”, and consists of high performance concrete wall construction. Each of the wings buttress the others via a six-sided central core, or hexagonal hub. This central core provides the torsional resistance of the structure, similar to a closed pipe or axle. Corridor walls extend from the central core to near the end of each wing, terminating in thickened hammer head walls. These corridor walls and hammerhead walls behave similar to the webs and flanges of a beam to resist the wind shears and moments. Perimeter columns and flat plate floor construction complete the system. At mechanical floors, outrigger walls are provided to link the perimeter columns to the interior wall system, allowing the perimeter columns to participate in the lateral load resistance of the structure; hence, all of the vertical concrete is utilized to support both gravity and lateral loads. The result is a tower that is extremely stiff laterally and torsionally. It is also a very efficient structure in that the gravity load resisting system has been utilized so as to maximize its use in resisting lateral loads.

As the building spirals in height, the wings set back to provide many different floor plates. The setbacks are organized with the tower’s grid, such that the building stepping is accomplished by aligning columns above with walls below to provide a smooth load path. As such, the tower does not contain any structural transfers. These setbacks also have the advantage of providing a different width to the tower for each differing floor plate. This stepping and shaping of the tower has the effect of “confusing the wind”: wind vortices never get organized over the height of the building because at each new tier the wind encounters a different building shape.

Spire

The crowning touch of Burj Khalifa is its telescopic spire comprised of more than 4,000 tons of structural steel. The spire was constructed from inside the building and jacked to its full height of over 200 metres (700 feet) using a hydraulic pump. In addition to securing Burj Khalifa’s place as the world’s tallest structure, the spire is integral to the overall design, creating a sense of completion for the landmark. The spire also houses communications equipment.
Mechanical Floors

Seven double-storey height mechanical floors house the equipment that bring Burj Khalifa to life. Distributed around every 30 storeys, the mechanical floors house the electrical sub-stations, water tanks and pumps, air-handling units etc, that are essential for the operation of the tower and the comfort of its occupants.
Window Washing Bays

Access for the tower’s exterior for both window washing and façade maintenance is provided by 18 permanently installed track and fixed telescopic, cradle equipped, building maintenance units. The track mounted units are stored in garages, within the structure, and are not visible when not in use. The manned cradles are capable of accessing the entire facade from tower top down to level seven. The building maintenance units jib arms, when fully extended will have a maximum reach of 36 meters with an overall length of approximately 45 meters. When fully retracted, to parked position, the jib arm length will measure approximately 15 meters. Under normal conditions, with all building maintenance units in operation, it will take three to four months to clean the entire exterior facade.
Broadcast and Communications Floors

The top four floors have been reserved for communications and broadcasting. These floors occupy the levels just below the spire.
Mechanical, Electrical & Plumbing

To achieve the greatest efficiencies, the mechanical, electrical and plumbing services for Burj Khalifa were developed in coordination during the design phase with cooperation of the architect, structural engineer and other consultant.

The tower’s water system supplies an average of 946,000 litres (250,000 gallons) of water daily
At peak cooling, Burj Khalifa will require about 10,000 tons of cooling, equal to the cooling capacity provided by about 10,000 tons of melting ice
Dubai’s hot, humid climate combined with the building’s cooling requirements creates a significant amount of condensation. This water is collected and drained in a separate piping system to a holding tank in the basement car park
The condensate collection system provides about 15 million gallons of supplement water per year, equal to about 20 Olympic-sized swimming pools
The tower’s peak electrical demand is 36mW, equal to about 360,000 100 Watt bulbs operating simultaneously

Fire Safety

Fire safety and speed of evacuation were prime factors in the design of Burj Khalifa. Concrete surrounds all stairwells and the building service and fireman’s elevator will have a capacity of 5,500 kg and will be the world’s tallest service elevator. Since people can’t reasonably be expected to walk down 160 floors, there are pressurized, air-conditioned refuge areas located approximately every 25 floors.

Elevators & Lifts

Burj Khalifa will be home to 57 elevators and 8 escalators The building service/fireman’s elevator will have a capacity of 5,500 kg and will be the world’s tallest service elevator
Burj Khalifa  first mega-high rise in which certain elevators will be programmed to permit controlled evacuation for certain fire or security events. Burj Khalifa’s Observatory elevators are double deck cabs with a capacity for 12-14 people per cab. Traveling at 10 metres per second, they will have the world’s longest travel distance from lowest to highest stop.