As unique as it looks, the Veluwemeer Aqueduct is the world’s shortest and most interesting aqueducts in the world. A stunning water bridge and a creative solution to the Veluwemeer lake crossing, the navigable aqueduct crosses N302 road, near Harderwijk, in the east of Holland, Netherlands. The aqueduct was named after the lake it serves, while the lake was named after the Veluwe region of Gelderland, which is due south of the lake.

The road, a scenic beauty and stunning work of engineering, connects mainland Netherlands to Flevoland — the largest artificial island in the world. Flevoland was constructed from reclaimed land in the region and is surrounded by three man-made lakes. This island is actually made up of two drained sections, Flevopolder and Noordoostpolder, which come together to make up the 374.5 square miles (970 square kilometers) province of Flevoland.

What makes this 25-meter long aqueduct stand out is the fact that people normally think of bridges as roads that cross over water but this one is the exact inverse. Veluwemeer aqueduct is a bridge for the passing ships while those driving in cars go through a tunnel underneath the bridge. In other words, it is an underwater tunnel where the ships sail on the top and the cars travel below it.

Design And Working
Dutch civil engineers and architects put in their creativity and came up with the brilliant idea of the aqueduct. In order to avoid spillage of water onto the road, aqueduct Veluwemeer uses 22,000 cubic meters of concrete to support the weight of the water above the roadway. It also uses steel sheet piling to prevent sediment from bleeding onto the highway. The bridge deck is made of prestressed concrete which allows the concrete beams to hold high loads of not only compression but also tension.

The aqueduct is 25 meters long and 19 meters wide with a water depth of 3 meters allowing small boats and other shallow-draft water vehicles to pass through, effortlessly. Along with the boats passage over the road, pedestrian walkways can be found on both sides, granting access for foot traffic to cross. The road itself also includes designated cycle lanes. 

Unlike drawbridges or other roadway structures, the water bridge design allows for constant traffic flow both on the road and over the aqueduct. An average of around 28,000 – 34,000 vehicles pass each day underneath the aqueduct.

During the design process engineers considered building an underwater tunnel or a high bridge but for this specific case these types of design ideas were proving to be too expensive and/or too obstructive to the landscape. Also, the construction time would have been longer than the water bridge. The construction started in 1998 and took 4 years to finish. The bridge costs 53M Euros or 61M USD.

The lake system was originally constructed to help regulate water levels and the groundwater table in the surrounding areas. Now established, the lakes are also important nature reserves (especially for water birds) and recreational areas for local residents.

Tuhina Chatterjee
Associate Editor
Civil Engineering and Construction Review

The mighty Paraná River located on the border between Brazil and Paraguay is harnessed by one of the largest operational hydroelectric energy producer in the world, the Itaipu Dam. The name“Itaipu” was taken from an isle that existed near the construction site. In the Guarani language, Itaipu means ‘the sounding stone’. The plant is operated by Itaipu Binacional and has an installed generation capacity of 14GW, with 20 generating units providing 700MW each with a hydraulic design head of 118m (387ft). The structure which serves to generate power is about 7.9km long, with a maximum height of 196m is known as one of the seven wonders of the modern world due to its sheer immensity, which costs US$19.6 billion (equivalent to $48.8 billion today).

The construction of the power plant is the result of intense negotiations between Brazil and Paraguay, which started back in the 60s. On April 26th, 1973, the countries signed the Itaipu Treaty, the legal instrument authorizing them to use the Paraná River for hydroelectric purposes. In May, 1974, the company Itaipu Binacional was created to build and manage the power plant. Completed in 1984, it is a bi-national undertaking run by Brazil and Paraguay; each country owns half of the 14,000MW output which the dam produces. The project ranges from Foz do Iguaçu, in Brazil and Ciudad del Este in Paraguay, in the south to Guaíra and Salto del Guairá in the north.

A total of 20 generator units installed, out of which 10 units generate at 50Hz for Paraguay and 10 units generate at 60Hz for Brazil. Since the output capacity of the Paraguayan generators far exceeds the energy requirement in Paraguay, most of their production is exported directly to the Brazilian side, from where 2 600 kV HVDC lines, each approximately 800km (500mi) long, carry the majority of the energy to the São Paulo/Rio de Janeiro region where the terminal equipment converts the power to 60Hz.

Design And Planning

A consortium of US-based IECO and Italy-based ELC Electroconsult carried out the viability studies of the project and its construction. In the planning stages of the Itaipú dam, the project team recognized that sediment blockage and unreliable flows during periods of dry weather which would pose significant challenges to the dam’s efficient functioning and performance. Sediment could potentially be removed from the reservoirs through dredging, yet this activity is expensive, environmentally harmful and would have to be completed at a large scale and at regular intervals.

The situation being completely unsustainable, Itaipú Binacional followed an outcomes-led approach which recognised that the forests and soils could provide benefits. Restoring forests, in particular in a belt along the river, and changing approaches to conventional land management practices that impact water quality, these nature-based solutions could provide water regulation and sediment control.

Forests offer a number of important water-related services like reducing the rate of sedimentation, and can store substantial amounts of water, protecting local catchments through gradual release and helping to regulate water flow. Owing to their expansive root systems, trees can help to stabilize soil, help control soil erosion and act as water filter and purifier. Once in place, nature-based solutions will continue to provide their services until they are removed an often require little to no maintenance. The sustainable solution can be quickly increase in scale as for the Itaipú dam, the services that are provided by nature are simply not feasible to replicate by other engineered solutions while providing a variety of additional benefits, including helping the dam become more resilient to changing climatic conditions and the influence that has on the rate of water flow.

Construction

The construction of one of the biggest dams began in the January of 1975 with an army of 40,000 workers who took 7 years to complete the gigantic hydroelectric energy producer. During its construction, workers shifted the course of the seventh largest river in the world by removing 50 million tons of earth and rock to dig a 1.3-mile bypass. It was biggest diversion canal ever attempted. Mechanical diggers were used to dig the diversion canal which took almost three years for workers to carve a 1.3-mile-long, 300-foot-deep, 490-foot-wide diversion channel for the river. The newly dug channel was used on 20th Oct, 1978 by blasting the concrete blocks. Only half of the river was diverted so cofferdams were built in the way of previous flow.

The Itaipu project included the construction of a 7,919m-long and 196m-high dam. The dam was built to form an artificial lake that accumulates water. Construction of the dam involved installing four rock crushing centres, two on each bank, with a total capacity of 2,430t/h, and six concrete mixing plants with a capacity of 180m³/h each. The site also includes two monorails, seven aerial cableways and 13 tower cranes. The dam used 12.3 million m³ of concrete.

Itaipu’s main dam, as high as a 65-story building, is composed of hollow concrete segments while the auxiliary dams are made from rockfill and earthfill rocks and earth from local excavations. The iron and steel used at Itaipu was enough to build 300 Eiffel Towers. The Dam was designed in such a manner that it was not to be supported by natural or physical features, instead it was to be made so heavy that water would simply not move it. Thus it had to weigh 61 million tons and Itaipu dam was named Gravity dam. The base of dams was wider and stood on sound solid foundations. The walls were made hollow and machinery and powerhouses were also installed therein to make the structure economical. During construction, in June 1979, weak layer of crumbling rock was discovered in the bedrock. The crushing rock was drilled out and replaced with a massive filling of 10 million pounds concrete of extra strength. Water pressure at the wall was estimated to be equal to 4000 bulldozers pushing against them Huge steel structures were erected to be filled in by concrete. As block of concrete was on mammoth size, heat of hydration was also to be equivalent, so aggregate was washed with ice and 4º C concrete was produced and temperature only reached 7º C during pouring.

If the usual method of concrete pouring was to be followed, then, it would not have set properly owing to the large size of concrete blocks. The greater the size of concrete blocks, the higher the heat of hydration produced, causing cracks to appear in the block boundaries, resulting in weakened concrete. Moreover, temperature of Brazil was also 40ºC and during usual setting of concrete the temperature would thus have reached 90º C due to heat of hydration, causing weak spots in dam. Sun dried concrete is weaker so large-scale refrigeration plants were installed to ensure maximum strength of the concrete blocks.

The reservoir was the filled up with water by re-diverting the river. It took 14 days for the river Parana’s water to completely fill the reservoir up to a depth of 100m. To stop the overflow of dam, spillways were built and designed to cope with 64 million liters/second of water. When first tested it was the biggest man made water fall ever. It was 22 times larger than the Niagara Falls. To dissipate the energy of high thrust water, a slope (jump) was provided at the end. The water from the spillway had a high thrust and if it were left to go directly down the stream it would have caused the production of high-energy waves, hence flooding. So, the water was thrown into the air. Hydraulic Engineers found out the angle of jump by scaled models.

Another marvel of Itaipu is its powerhouse – half a mile long, half underwater and containing 18 hydroelectric generators each 53ft. across. Some 160 tons of water per second pour onto each turbine, generating 12,600M. Itaipu currently supplies 28% of all the electric energy in Brazil’s south, southeast and central-west regions, and 72% of Paraguay’s total energy consumption.

Fast Facts

• The total length of the dam is 7235m, with the crest elevation of It is actually several dams joined together – from the far left, an earthfill dam, a rockfill dam, a concrete main dam, and a concrete wing dam to the right.
• Engineers chose a hollow gravity dam because it required 35% less concrete than a solid gravity The hollow dam is still heavy and sturdy enough to resist the thrust of water entirely by its own weight.
• The volume of iron and steel used in the dam would be enough to build 380 Eiffel Towers.
• The dam is a major tourist More than nine million visitors from 162 countries have visited the structure since it was completed in 1991.
• To cure the concrete properly, they had to use large refrigeration units equal to 50,000 deep freezers.
• Itaipu Dam generated 94,684MW in This is the most power that has been produced by a single dam.
• The electric power cables were of such a length that they could run 1-1/2 times around the globe.

Reservoir Water volume at the usual maximum level: 29 billion m³ Extension: 170km Usual maximum level (quota): 220m Area in the usual maximum level: 1.350km² Spillway Maximum outflow: 62.2 thousand m³/s Maximum release capability: 162.200 m³/s Length: 483m Gates: 14 units Gate size: 21m high and 20m wide Dam Height: 196m Total length: 7,919m River Basin Area: 820.000km² Average annual rainfall: 1,650mm Average affluent outflow: 11,663m³/s Generating units Power: 700MW Voltage: 18kV Frequency: 50 to 60Hz Drop: 118.4m Rated outflow: 690m³/s Weight: 6,600t Power House Length: 968m Width: 99m Maximum height: 112m Penstocks Quantity: 20 Length: 142m Inside diameter: 10.5m Rated release: 690m³/s Turbines Outflow: 700m³ of water/s Excavations Volume of soil excavated: 23.6 million m³ Materials Volume of concrete used: 12.7 million m³

Reference

1. https://waboutcivil.org/itaipu-dam-design-construction-facts.html
2. https://wpowerinfotoday.com/america/itaipu-hydroelectric-dam/
3. https://www.itaipu.gov.br/en/press–office/faq
4. https://wresilienceshift.org/case-study/itaipu-dam/

Tuhina Chatterjee
Associate Editor Civil Engineering and Construction Review

Lotte World Tower

The South Korean government, in the past decade, provided a great deal of assistance for a number of tall building projects in lieu of inner city regeneration endeavours. One such project was Lotte World Tower at 1,820 ft. (555m) height located in Seoul, South Korea, stands as the first super tall building with 123-storeys and more than 1.8 times taller than the previous tallest building, located in the nearby city of Incheon. The building culminated in December 2015 and the tower ’s topmast, christened as the “Lantern,” was completed in March 2016. Designed by architects Kohn Pedersen Fox Associates and structural engineers Leslie E. Robertson Associates (LERA) of New York, the $2.5 billion tower and adjacent development features a variety of usages, including office, retail, hotel, officetel (a combination office and apartment common in Korea), parking, museum and observation space.

Building Illustration The tower ’s struc tural system is made of a gravity-resistant and a lateral force resistance system. The tower has a tapering shape with sloping concrete core walls in the middle third of the building and columns sloping in two directions which creates a unique environment on every floor. The office and officetel floors, from the ground level to 71 level occupies the majority of the tower, are steel framed with a slab-on-truss deck. The Hotel floors from levels 87 to 101 are concrete flat slabs with drops. The tower consists of a diagrid structure at the top of the building contains premium office, museum, and observation floors, which are also steel framed with a slab-on-truss deck. With piles reinforcing the ground, the tower sits on top of a 21.3ft. (6.5m) thick mat. Conforming to Korean building regulations, these piles are not connected to the mat. The tapered shape of the building was effective at minimizing wind loads but it led to challenging structural complexities. The primary lateral load and gravity system of the tower consists eight concrete mega-columns, concrete core walls, a series of outriggers and belt trusses located at the mechanical, refuge, sky lobby and hotel amenity floors.

The diagrid “lantern” structure is transferred by the belt trusses to the column configuration of the hotel floors, as well as the columns of the hotel floors to the mega-columns at the officetel and office floors. For tying the perimeter mega-columns to the concrete core, only two levels of outriggers were needed to control the tower’s drift and lateral accelerations due to wind loads.

The 10 ft. 9” X 10 ft. 9” (3.3m X 3.3m) mega-columns at the ground level (unbraced for the first eight levels) are comparatively small compared to other towers of similar height and even qualify as slender members. Higher up the building, the hotel floors are supported by perimeter steel columns that are spaced at the module of the hotel room partitions and transferred through belt trusses. LERA with the architects worked closely to balance out the structural efficiency gained by adding columns and the need to preserve open floor plans. A multitude of structural designs were studied – a system of concrete mega-columns with relatively small intermediate steel columns at the perimeter ; a system of long-span spandrels with clear spans between concrete mega-columns; and a combination of the two. Lotte, the owner, selected a system of long-span spandrels for the office and officetel floors, with spans of up to 80ft. (24.5m) between mega-columns. The building

corners have long-span spandrels cantilever 46ft. (14m) beyond the mega-columns while bending to follow the building’s curved floors. These corners posed significant challenges for meeting the stringent deflection and vibration floor criteria. To overcome this hurdle, LERA designed a series of 1 storey high deflection control posts at every other floor, aligned with the cladding mullions.

Foundation As per a geotechnical repor t, the soil beneath the foundation is made up of soft and hard rocks. The permissible strength bearing of these rocks is 3,000 KPa which is suitable for supporting the building weight. Nevertheless, the area contained fault zones and shear zones which might have lead to settlement and to prevent it, ground strengthening piles were put into use. The piles of 1.0m. dia. were installed using PRD (Percussion Rotary Drilled) method preventing the settlement of the mat foundation and also the uneven settlement under the RC core walls and the megacolumns. To separate the mat foundation from the piles, a sand cushion was installed at the upper part of the piles. With the help of soil engineering specialists, the 6.5m thick mat foundation was designed considering static and dynamic soil springs. This massive foundation consists of 4,200 tons of steel reinforcement, including those with a diameter of 5.1 cm, and 80,000 tons of high strength concrete. In the building’s surrounding area, 1m thick and 27m long cut off collars were installed through the bedrock in order to keep underground water from leaking in. Lateral Load Resisting System As per the design need, lateral loads on the building are resisted by RC core walls, outriggers, belt trusses and megacolumns. A study was conducted which resulted in determining two sets of outriggers and two sets of belt trusses to be the most optimal fixes for the lateral load resisting system. Perimeter frames of typical floors were also changed to a long spandrel girder system connecting the megacolumns.

Steel box B – 1600 X 500 X 80 X 20 was used for outrigger diagonal members. As, they mainly support axis loads, the web thickness of the steel box was increased to 80mm and the flange thickness was decreased to 20mm. The top chord of the outrigger penetrated the RC core wall and reach horizontal truss member on the other side so that horizontal forces in the RC core walls can be easily transferred to the outrigger trusses.

Sustainable Features

The Lotte World Tower incorporates sustainable features of the LEED Gold standard.

• Greening of Rooftop
  Lower-floors insulation through greening of rooftop for reducing heating/cooling load and environmental pollution.

• High Insulation Glass (Low0E)
  Reduction of heat loss in winter and blocking of heat in summer.

• Recycling of Heavy Water and Rainwater
  Operation of heavy water treatment facilities (1,200t) and rainwater storage tanks (1,900t) for recycling domestic sewage

• High Efficiency Equipment and Apparatus
  These facilities have been incorporated to achieve savings of 30%.

• Wind Power Generation
  Wind power generator installed in upper floors and around the complex to generate electricity.

• Solar Heat Collector
  Collection of solar energy in rooftop to be used for heating and hot water supply.

Reference

1. https://global.ctbuh.org/resources/ papers/download/2504-challenges[1]and-opportunities-for-the-structural[1]design-of-the-123-story-jamsil-lotte[1]world-tower.pdf
2. https://www.lottepnd.com/en/tower/ safety/method.do#:~:text=This%20 massive%20foundation%20 consists%20of,times%20more%20 concrete%20was%20used.
3. https://w ww.structuremag. org/?p=11393

Lakhta Center

Lakhta Centre, situated in the north western region of Lakhta in Saint Petersburg, Russia; is an 87-storey skyscraper, standing 462m (1,516ft.) tall infront of Baltic Sea, is the tallest building in Russia, the tallest building in Europe, and the fourteenth-tallest building in the world. 30th October 2012 marked the beginning of the iconic building’s construction while it reached its zenith on 29th January 2018. Designed for large-scale  mixed-use development, consisting of public facilities and offices, the project was first undertaken by RMJM, it was then continued by GORPROJECT (2011-2017) based on the RMJM Concept (2011) under the main contractor, Rönesans Holding. The unique spear-shaped tower, featuring a tapering, rotating design, is intended to be the new Saint Petersburg headquarters for Russian energy company, Gazprom.

Structural System

The structure of the tower is shaped around a central circular core wall with 5 equal wings/petals that rotate 90 degrees from the base to the top of the spire which means none of its 89 floors repeat and tapers relative to the tower’s structural center. The overall dimension of the tower is approximately 213.26 ft. (65m) at the base, 220.8 ft. (67.3m) at level 17, 91.2ft. (27.8m) at level 86, and diminishes at the tower pinnacle at 1515.7ft. (462m).

Steel Spire 108m tall Structural Steel Braced Frame assembled with pipe/tube sections. Composite Outrigger Composite Steel Outrigger (Steel Truss encased in Concrete) linking the reinforced concrete core wall with the composite columns to create the Mega Frame structure. Composite Columns Composite Columns/Steel Reinforced Composite Columns (SRCC) consisting of Structural Steel Sections encased in Concrete and reinforced bars. – Hi Star Steel Columns/C80 Concrete/A500 Rebar – Column sizes vary from 1500X1500 to 1000X1000 – Using SRCC to minimize differential Shortening between Core wall and SRCC Typical Floor Framing System – Composite Steel floor framing with 150 slab on corrugated metal deck – All Steel beam to receive cementitious fireproofing to achieve the required fire rating

• Reinforced Concrete Core Wall System
  RC core + Composite Steel Outrigger connected to Composite Columns at 5 locations along with the building height. (17-18, 33-34, 49-50, 65-66 and 83)

• Box Foundation System
  Consisting of 3.6m thick bottom raft (Bottom Flange @ TOS EL = 17.65m) connected to 2m thick slab (Top Flange @ TOS EL : -4.65) with Fin walls to provide very stiff foundation box section to distribute the tower loads to the 2m dia. piles that extend to 65m and 55m within and outside the core area respectively.

Façade Construction

The façade comprises of 1,550 metric tons of aluminium and 1,100 metric tons of steel, whereby the outer façade has an area of approx. 73,000m² and the inner façade approx. 25,000m². The latter is mainly made of glass walls for the inner closure of the entrance. The elements of the outer façade are mainly in the shape of a parallelogram; at 4.2 x 2.8m, they weigh up to 790 kg. In total, there are over 16,500 different and partly bent elements. The aluminium-glass façade is fastened to steel girders in the entrance area; these girders span two storeys despite the twisting of the floor slabs. A total of six different types (WT1 – 6) were produced for the tower façade’s construction. The main façade is made up of the WT1 glass façades of the office areas, the WT2 glass façades of the atriums and the WT3 of the corner façades with stainless steel casing.

High Grade Sustainability The Lakhta Center’s energy-efficient design highlights advanced heating, waste, and lighting systems and an “intelligent facade” that reduces energy consumption earning Platinum certification. Rain water is recycled for irrigation, and the building uses a pneumatic-vacuum waste-disposal system. Inside, infrared radiators replace conventional heaters; excess heat generated by the building’s plumbing equipment, mechanical and electrical equipment is channelled into the heating system. A computerized LED-lighting system maximizes light energy, both inside and out.

Reference

1. https://redshift.autodesk.com/lakhta-tower/
2. https://www.skyscrapercenter.com/building/lakhta[1]center/12575
3. https://www.researchgate.net/publication/349076674_The_Structural_Engineering_Design_And_Construction_Of_
   The_Tallest_Building_In_Europe_Lakhta_Center_St_Petersburg_Russia

Tuhina Chatterjee
Associate Editor
Civil Engineering and Construction Review

Known as the Lærdal Tunnel (or Lærdalstunnelen in Norwegian), the construction time lasted five years and was completed in 2000, surpassing the world’s second longest tunnel, the St. Gottard Tunnel in Switzerland, by five miles. The idea to come up with a tunnel instead of repairing the already existing roads was to avoid harsh terrains where rock falls were common and the roads risky. From environmental point of view, it was well founded to invest in the new tunnel so as to preserve the untouched natural beauty.

Fabrication

During the tunnel’s construction from 1995 to 2000, a total of 2,500,000 cubic metres (3,300,000 cubic yards) of rock was removed. The tunnel starts just east of Aurlandsvangen in Aurland and runs through a mountain range before ending 5.5 km (3.4 mi) south of Lærdalsøyri in Laerdal.

It was a daunting challenge for Norwegian Public Roads Administration (NPRA) to design a tunnel in such a fashion so that people did not find the 20-minute-long drive monotonous, thereby losing concentration during the long journey. The working group were led by psychologists at SINTEF (the Industrial and Technological Research Association) and to find fitting lightings, advantageous designs and gradual curves with shorter straight sections, simulators were brought into play

Strict adherence to guidelines for safe viewing distance was implemented so as to not breach them in any fashion. At any given point in the tunnel, the safe viewing distance is 1,000 m or more. At every 125 m, fire extinguishers are provided and 15 turning areas are incorporated for semi-trailers and buses. At every 500 m, emergency bays are available.

The tunnel has been designed while keeping in mind the mental strain of the drivers and to prevent them from falling asleep. Hence, the tunnel is divided into four segments which are separated by three large mountain caves at 6 km (3.7 mi) intervals. The caves have blue lights and yellow lights on the borders which look like sunrise; the main tunnel has white lights. The caves have been incorporated in the design to break the monotony of driving such a long stretch. It provides the drivers with short rests and rejuvenating scenery.

Topography And Augmentation

The dominant type of rock in the Laerdal tunnel is Precambrian Gneiss. The rock is mostly solid, but there were a few zones where it was broken and cracked. A few were so distinct at tunnel level that major safety initiatives were necessary while drilling the tunnel. While passing through a weak zone 10 km from Aurland, there was a huge fall from the roof of the tunnel. A total of around 1,000 cubic metres of rock fell. In order to continue, the entire site of the fall was filled with concrete and a new tunnel was then drilled through the fallen rock and concrete.

The Laerdal tunnel runs deep inside the mountain, with up to 1400 m of rock above the tunnel. The large masses of rock above the tunnel exert immense pressure. This, combined with the stresses from the horizontal tension in the earth’s crust, can lead to large chunks of rock falling from the tunnel’s ceiling and walls. This phenomenon is known as “rock burst”. The size of rock burst debris varies from small, thin flakes to huge blocks of stone. The builders of the Laerdal tunnel faced this problem frequently.

Construction

Works on the construction of the tunnel began from three positions at the same time and was divided into four stages:
* Drilling
* Blasting
* Loading and Transport
* Excavating and Landscaping

Computer controlled drilling of the tunnel with drilling jumbos, traditional drilling and blasting was carried out with great precision to make sure that the tunnel sections met more than 10 km into the rock and 1000 m under the mountain and maintain geometric precision. To determine fixed survey points on which other measurements inside the tunnel were based, navigation satellites were utilised.  Inside the tunnel, bearings were indicated using laser beams. A computer on the drilling jumbo captured the laser beams and positioned the drilling equipment automatically, according to a set pattern. Each drilling jumbo contained three automatic hydraulic drills.

Computer controlled drilling of the tunnel with drilling jumbos, traditional drilling and blasting was carried out with great precision to make sure that the tunnel sections met more than 10 km into the rock and 1000 m under the mountain and maintain geometric precision. To determine fixed survey points on which other measurements inside the tunnel were based, navigation satellites were utilised.  Inside the tunnel, bearings were indicated using laser beams. A computer on the drilling jumbo captured the laser beams and positioned the drilling equipment automatically, according to a set pattern. Each drilling jumbo contained three automatic hydraulic drills.

To transport the excavated materials out of the tunnel, wheel mounted loaders were utilized. Also, a permanent road was built in parallel to the ongoing tunnelling work, increasing efficiency and reducing pollution of the transport vehicles.

Ventilation

Aside from its remarkable length, the Lærdal Tunnel is also the first to come up with its own air treatment plant. Better air quality in the tunnel is achieved in two ways: ventilation and purification. Located in a 328-foot (100 m) chamber about 9.5 km (5.9 mi) northwest of Aurlandsvangen, the tunnel is longitudinally ventilated. There is only one ventilation air exhaust shaft, 18 km from the Aurland end of the tunnel. About 10 km from the Aurland end of the tunnel, a cleaning plant for the tunnel ventilation air is installed in a short side tunnel which cleans the flowing air for polluting components. Constant cleaning from this plant maintains an acceptable air quality throughout the tunnel even during heavy traffic. The cleaning plant comprises of an electrostatic precipitator which removes particulate impurities, followed by a gas cleaning plant that removes heavy polluting gaseous components from the air.

The upstream electrostatic precipitator is proven technology especially developed for tunnel air cleaning purposes by the Norwegian company CTA, and is highly efficient. It will remove 90-95% of the respiratory particles (PM10) in the air. The downstream gas cleaning system, delivered by ABB Miljø AS, removes 85-90% of the nitrogen dioxide (NO2 ) gas and absorbs 60% of the VOC gases (Volatile Organic Compounds — un-combusted remains from gasoline and diesel gases) including 75% or better removal of components like Benzene, and similar aromatic and polyaromatic hydrocarbons (PAHs). Ozone (O3) is removed to 100%.

The tunnel shaft exhausts the residual air in a non-populated area. For city tunnels, where pollution problems are primarily related for the city air quality in general, this air cleaning technology can advantageously be used to clean the polluted ventilation air from the tunnel before discharge into the urban environment.

Reference

1. https://www.engineering.com/story/laerdal-tunnel
   2. https://www.geotech.hr/en/lighting-effects-in-the-longest-road-tunnel-in[1]the-world-the-laerdal-tunnel-norway/
   3. https://www.atlasobscura.com/places/laerdal-tunne 

The Flatiron Building is located at 175 Fifth Avenue in the Flatiron District neighborhood of the borough of Manhattan, New York City. It is a triangular 22-story, 285-foot-tall (86.9 m) steel-framed building which is considered to be a groundbreaking skyscraper.

The Flatiron building was originally called The Fuller Building, named after George A. Fuller who was an architect often credited as being the “inventor” of modern skyscrapers and the modern contracting system.

This building was designed by Daniel Burnham and Frederick Dinkelberg. Its construction was completed in the year 1902 and was one of the tallest buildings in the city. It was the most recognizable early steel skyscraper construction in the United States. It is known for its triangular structural composition which also gave the building its name.

The triangular block formed by Fifth Avenue, Broadway, and East 22nd Street – where the building’s 87-foot (27 m) back end is located – with East 23rd Street grazing the triangle’s northern peak. As with numerous other wedge-shaped buildings, the name “Flatiron” derives from its resemblance to a cast-iron clothes iron.

The building anchors the south end of Madison Square and the north end of the Ladies’ Mile Historic District. The neighborhood around it is called the Flatiron District after its signature building, which has become an icon of New York City.

The building was designated as a New York City landmark in 1966. It was also added to the National Register of Historic Places in 1979, and designated a National Historic Landmark in 1989.

Construction

Once construction of the building started, it proceeded at a quick pace. The steel was so meticulously pre-cut that the frame went up at the rate of a floor each week. By February 1902 the frame was complete, and by mid-May the building was half-covered by terra-cotta tiling. The building was completed in June 1902, after a year of construction. The Flatiron Building was designed by Chicago’s Daniel Burnham as a vertical Renaissance palazzo with Beaux-Arts styling. The Flatiron Building epitomizes the Chicago school conception. Like a classical Greek column, its facade – limestone at the bottom changing to glazed terra-cotta from the Atlantic Terra Cotta Company in Tottenville, Staten Island as the floors rise – is divided into a base, shaft, and capital. Early sketches by Daniel Burnham show a design with an (unexecuted) clockface and a far more elaborate crown than in the actual building. Working drawings for the Flatiron Building remain to be located, though renderings were published at the time of construction in American Architect and Architectural Record.

The building was considered to be bizarre, with drafty wood-framed and cooper-clad windows, no central air conditioning, and a heating system which utilized cast-iron radiators, an antiquated sprinkler system, and a single staircase should evacuation of the building be necessary. The triangular shape of the structure driven to a “rabbit warren” of oddly-shaped rooms. Additionally, to reach the top floor – the 21st, which was added in 1905, three years after the building was completed – a second elevator has to be taken from the 20th floor.

Steel skeleton

Building the Flatiron was made attainable by an alter to New York City’s building codes in 1892, which eliminated the prerequisite that masonry be utilized for fireproofing contemplations. This opened the way for steel-skeleton construction. Since it utilized a steel skeleton – with the steel coming from the American Bridge Company in Pennsylvania – it may well be built to 22 stories (285 feet) relatively easily, which would have been difficult using other construction methods of that time.

It was a technique familiar to the Fuller Company, a contracting firm with significant skill in building such tall structures. At the vertex, the triangular tower is only 6.5 feet (2 m) wide; viewed from above, this pointed end of the structure portray an acute angle of about 25 degrees. The structural engineers Purdy and Henderson, strengthened the structure to deal with the wind load, as the building was quite narrow and therefore had less volume to resist it. They designed it so that, in theory, the building would turn compactly before any failure could occur in the metal structure.

Due to the geography of the site, with Broadway on one side, Fifth Avenue on the other, and the open expanse of Madison Square and the park in front of it, the wind currents around the building could be treacherous. Wind from the north would split around the building, downdrafts from above and updrafts from the vaulted area under the street would combine to make the wind unpredictable. Nevertheless, the wind was a factor in the public attention the building received.

The steel bracing enabled the building to withstand four times the amount of wind force it could ever be expected to endure, there was no possibility that the wind would knock over the Flatiron Building.

Spanning the East River between the boroughs of Manhattan and Brooklyn, the Brooklyn Bridge is the first hybrid cable-stayed/suspension bridge in New York City.

The Brooklyn Bridge was opened on May 24, 1883. At the time of its opening, it was the longest suspension bridge in the world, with a main span between the two suspension towers is 1,595.5 feet (486.3 m) long, 85 feet (26 m) wide and a deck 127 ft (38.7 m) above mean high water (MHW).

Suspension Span

The bridge widens and contracts between the extremes of temperature from 14 to 16 inches. Navigational clearance is 127 ft (38.7 m) above MHW.

There is 930 feet (280 m) long gap between each suspension tower and each side’s suspension anchorages.

Structure containing six trusses supports the main span and side spans. This structure runs parallel to the roadway, each of which is 33 feet (10 m) deep. The Brooklyn Bridge is able to hold a total load of 18,700 short tons (16,700 long tons) with the help of the trusses. These trusses are supported by suspender ropes, which hang downward from each of the four main cables. Crossbeams run between the trusses at the top, and diagonal and vertical stiffening beams run on the outside and inside of each roadway.

An elevated pedestrian and cycling promenade that is 10 to 17 feet (3.0 to 5.2 m) wide, runs in between the two roadways and 18 feet (5.5 m) above them. It typically runs 4 feet (1.2 m) below the level of the crossbeams, except at the areas surrounding each tower. Here, the promenade rises to just above the level of the crossbeams, connecting to a balcony that slightly overhangs the two roadways.

Approaches

The approach ramps are connected to each of the side spans. The 1,567-foot (478 m) approach ramp from the Manhattan side is longer as compared to the 971-foot (296 m) approach ramp from the Brooklyn side. The Renaissance-style arches made of masonry supports the approaches; the arch openings themselves were filled with brick walls, with small windows within. The approach ramp contains nine arch or iron-girder bridges across side streets in Manhattan and Brooklyn.

Construction

Construction of the Brooklyn Bridge began on January 2, 1870. The first work entailed the construction of two caissons, upon which the suspension towers would be built.

Caissons

The caissons are made of southern yellow pine on which the towers rest on underwater. Both caissons contain interior spaces that were used by construction workers. The Manhattan side’s caisson is slightly larger as compared the Brooklyn side’s caisson. The Manhattan’s side caisson which is located 78.5 feet (23.9 m) below high water & Brooklyn’s side caisson located 44.5 feet (13.6 m) below high water, measures 172 by 102 feet (52 by 31 m) and, measures 168 by 102 feet (51 by 31 m) respectively. The caissons were designed to hold at least the weight of the towers which would exert a pressure of 5 short tons per square foot (49 t/m2) when fully built, but the caissons were over-engineered for safety. Compressed air was pumped into the caisson, and workers entered the space to dig the sediment until it sank to the bedrock. On March 6, 1871, the caisson had reached its final depth of 44.5 feet (13.6 m). At its final depth, the caisson’s air pressure was 21 pounds per square inch (140 kPa). The Manhattan caisson was lined with fireproof plate iron. It was launched from Webb & Bell’s shipyard on May 11, 1871. After the Manhattan caisson reached a depth of 78.5 feet (23.9 m) with an air pressure of 35 pounds per square inch (240 kPa), Washington Roebling deemed the sandy subsoil overlying the bedrock 30 feet (9.1 m) beneath to be sufficiently firm, and subsequently infilled the caisson with concrete in July 1872.

Cables

There are four main cables that supports the Brooklyn Bridge, which descend from the top of the suspension towers and help support the deck. Two are outside the bridge’s roadways and two are in the median of the roadways. The main cables measures 15.75 inches (40 cm) in diameter and contains 5,282 parallel, galvanized steel wires wrapped closely together in a cylindrical shape. These wires are bundled in 19 individual strands, with 278 wires to a strand. The first temporary steel wire which was provided by the Chrome Steel Company of Brooklyn, stretched between the towers on August 15, 1876.

The wire was then stretched back across the river, and the two ends were interwoven to form a traveler, a lengthy loop of wire connecting the towers, which was driven by a 30 horsepower (22 kW) steam hoisting engine at ground level.The wire was one of two that were used to create a temporary footbridge for workers while cable spinning was ongoing. A second traveler wire was stretched across the span, a task that was completed by August 30 1876.Anchorages

The bridge consists of an anchorage for the main cables. The Manhattan anchorage rests on a foundation of bedrock while the Brooklyn anchorage rests on clay.

The anchorages are trapezoidal limestone structures situated inland of the shore, measuring 129 by 119 feet (39 by 36 m) at the base and 117 by 104 feet (36 by 32 m) at the top. Each anchorage weighs 60,000 short tons (54,000 long tons).

The anchorages both have four anchor plates, one for each of the main cables, which are located near ground level and parallel to the ground. The anchor plates measure 16 by 17.5 inches (410 by 440 mm), with a thickness of 2.5 inches (64 mm) and weigh 46,000 pounds (21,000 kg) each. Each anchor plate is connected to the respective main cable by two sets of nine eyebars, each of which is about 12.5 feet (3.8 m) long and up to 9 by 3 inches (229 by 76 mm) thick. The chains of eyebars curve downward from the cables toward the anchor plates.

Towers

The bridge’s two suspension towers are 278 feet (85 m) tall with a footprint of 140 by 59 feet (43 by 18 m) at the high water line. They are built of limestone, granite, and Rosendale cement. The Manhattan tower contains 46,945 cubic yards (35,892 m3) of masonry and the Brooklyn tower has 38,214 cubic yards (29,217 m3) of masonry.

Each tower contains a pair of Gothic Revival pointed arches, through which the roadways run. The arch openings are 117 feet (36 m) tall and 33.75 feet (10.29 m) wide. The tops of the towers are located 159 feet (48 m) above the floor of each arch opening, while the floors of the openings are 119.25 feet (36.35 m) above mean water level, giving the towers a total height of 278.25 feet (84.81 m) above MHW.

After the caissons were completed, piers were constructed on top of each of them upon which masonry towers would be built. The towers’ construction was a complex process that took four years. Since the masonry blocks were heavy, the builders transported them to the base of the towers using a pulley system with a continuous 1.5 – inch (3.8 cm)-diameter steel wire rope, operated by steam engines at ground level. The blocks were then carried up on a timber track alongside each tower and maneuvered into the proper position using a derrick atop the towers.

Construction on the suspension towers started in mid-1872, and by the time work was halted for the winter in late 1872, parts of each tower had already been built. By mid-1873, there was substantial progress on the towers’ construction. The arches of the Brooklyn tower were completed by August 1874. The tower was substantially finished by December 1874 with the erection of saddle plates for the main cables at the top of the tower. The Manhattan tower was completed in July 1876. The saddle plates atop both towers were also raised in July 1876.

Costing

The project depleted its original $5 million budget in the year 1875, while it was under construction. So, both the bridge commissioners, one each from Brooklyn and Manhattan, petitioned New York state lawmakers to allot another $8 million for construction. At the end, the legislators passed a law authorizing the allotment with the condition that the cities would buy the stock of Brooklyn Bridge’s private stockholders.

The bridge had cost US $15.5 million in 1883 dollars to build, of which Brooklyn paid two-thirds. Rehabilitation of the bridge cost about $153 million. As part of the project, the bridge’s original suspender cables installed by J. Lloyd Haigh were replaced by Bethlehem Steel in 1986, marking the cables’ first replacement since construction.

Use of Steel

A permanent contract was awarded, the builders ordered 30 short tons (27 long tons) of wire in the interim, 10 tons each from three companies, including Washington Roebling’s own steel mill in Brooklyn. In the end, it was decided to use number 8 Birmingham gauge (approximately 4 mm or 0.165 inches in diameter) crucible steel. In January 1877, a contract for crucible steel was awarded to J. Lloyd Haigh, who was associated with bridge trustee Abram Hewitt.

Opening

The Brooklyn Bridge was opened for use on May 24, 1883. Thousands of people attended the opening ceremony, and many ships were present in the East River for the occasion. Officially, Emily Warren Roebling was the first to cross the bridge. The bridge opening was also attended by U.S. President Chester A. Arthur and New York mayor Franklin Edson.

Renovation

The first major upgrade to the Brooklyn Bridge commenced in 1948, when a contract for redesigning the roadways were awarded to David B. Steinman. The renovation was expected to double the capacity of the bridge’s roadways to nearly 6,000 cars per hour, at a projected cost of $7 million. The renovation included the demolition of both the elevated and the trolley tracks on the roadways, the removal of trusses separating the inner elevated tracks from the existing vehicle lanes and the widening of each roadway from two to three lanes, as well as the construction of a new steel-and-concrete floor.

Conclusion

The Roeblings family are largely responsible for the conception, design, development and execution of the bridge.

This bridge was designated a National Historic Civil Engineering Landmark in 1972.

At the time of construction, contemporaries marveled at what technology was capable of, and the Brooklyn Bridge was seen as a symbol of optimism and aspiration in the field of engineering upon its completion in 1883 and it remains an inspiration till date.

Reference

1. https://en.wikipedia.org/wiki/Brooklyn_Bridge
2. https://www.britannica.com/topic/Brooklyn-Bridge

The Space Needle is an observation tower in Seattle, Washington, United States. Considered to be an icon of the city and the Pacific Northwest, it has been designated a Seattle landmark. Located in the Lower Queen Anne neighbourhood, it was built in the Seattle Center for the 1962 World’s Fair, which drew over 2.3 million visitors. Nearly 20,000 people a day used its elevators during the event.

The Space Needle was once the tallest structure west of the Mississippi River, standing at 605 ft (184 m). The tower is 138 ft (42 m) wide, weighs 9,550 short tons (8,660 metric tons), and is built to withstand winds of up to 200 mph (320 km/h) and earthquakes of up to 9.0 magnitude, as strong as the 1700 Cascadia earthquake. It also has 25 lightning rods.

The Space Needle features an observation deck 520 ft (160 m) above ground, providing views of the downtown Seattle skyline, the Olympic and Cascade Mountains, Mount Rainier, Mount Baker, Elliott Bay, and various islands in Puget Sound. Visitors can reach the top of the Space Needle by elevators that travel at 10 mph (16 km/h), completing the ascent in 41 seconds [they are slowed to 5 mph (8.0 km/h) on windy days]. On April 19, 1999, the city’s Landmarks Preservation Board designated the tower a historic landmark.

Architecture

The architecture of the Space Needle is the result of a compromise between the designs of two men, Edward E. Carlson and John Graham, Jr. The two leading ideas for the World Fair involved businessman Edward E. Carlson’s sketch of a giant balloon tethered to the ground (the gently sloping base) and architect John Graham’s concept of a flying saucer (the halo that houses the restaurant and observation deck). Victor Steinbrueck introduced the hourglass profile of the tower. The Space Needle was built to withstand wind speeds of 200 mph (320 km/h), double the requirements in the building code of 1962. The 6.8 Mw Nisqually earthquake jolted the Needle enough in 2001 for water to slosh out of the toilets in the restrooms. The Space Needle will not sustain serious structural damage during earthquakes of magnitudes below 9.1. 

Also made to withstand Category 5 hurricane-force winds, the Space Needle sways only 1 in (25 mm) per 10 mph (16 km/h) of wind speed. For decades, the hovering disk of the Space Needle was home to two restaurants 500 ft (150 m) above the ground: the Space Needle Restaurant, which was originally named Eye of the Needle, and Emerald Suite. These were closed in 2000 to make way for SkyCity, a larger restaurant that features Pacific Northwest cuisine. SkyCity rotates 360 degrees in exactly forty-seven minutes. In 1993, the elevators were replaced with new computerized versions. The new elevators descend at a rate of 10 mph (16 km/h).

On December 31, 1999, a powerful beam of light was unveiled for the first time. Called the Legacy Light or Skybeam, it is powered by lamps that total 85 million candela shining skyward from the top of the Space Needle to honour national holidays and special occasions in Seattle. The concept of this beam was derived from the official 1962 World’s Fair poster, which depicted such a light source although none was incorporated into the original design. It is somewhat controversial because of the light pollution it creates. Originally planned to be turned on 75 nights per year, it has generally been used fewer than a dozen times per year. It did remain lit for eleven days in a row from September 11, 2001, to September 22, 2001, in response to the September 11, 2001 attacks.

A 1962 Seattle World’s Fair poster showed a grand spiral entryway leading to the elevator that was ultimately omitted from final building plans. The stairway was eventually added as part of the Pavilion and Spacebase remodel in June 2000. The main stairwell has 848 steps from the basement to the top of the observation deck. At approximately 605 ft (184 m), the Space Needle was the tallest building west of the Mississippi River at the time it was built by Howard S. Wright Construction Co., but is now dwarfed by other structures along the Seattle skyline, among them the Columbia Center, at 967 ft (295 m). Unlike many other similar structures, such as the CN Tower in Toronto, the Space Needle is not used for broadcasting purposes.

Construction

The earthquake stability of the Space Needle was ensured when a hole was dug 30 ft (9.1 m) deep and 120 ft (37 m) across, and 467 concrete trucks took one full day to fill it. The foundation weighs 5,850 short tons (5,310 metric tons) (including 250 short tons or 230 metric tons of reinforcing steel), the same as the aboveground structure. The structure is bolted to the foundation with 72 bolts, each one 30 ft (9.1 m) long.

With time an issue, the construction team worked around the clock. The domed top, housing the top five levels (including the restaurants and observation deck), was perfectly balanced so that the restaurant could rotate with the help of one tiny electric motor, originally 0.8 kilowatts (1.1 hp), later replaced with a 1.1 kilowatts (1.5 hp) motor. With paint colours named Orbital Olive for the body, Astronaut White for the legs, Re-entry Red for the saucer, and Galaxy Gold for the roof, the Space Needle was finished in less than one year. It was completed in April 1962 at a cost of $4.5 million. The last elevator car was installed the day before the Fair opened on April 21. During the course of the Fair nearly 20,000 people a day rode the elevators to the Observation Deck. 

Upon completion, the Space Needle was the tallest building in the western United States, replacing the Smith Tower in downtown Seattle as the tallest building west of the Mississippi since 1914. In 1982, the SkyLine level was added at the height of 100 ft (30 m). While this level had been part of the original plans for the Space Needle, it was not built until this time. Today, the SkyLine Banquet Facility can accommodate groups of 20–360 people. Renovations were completed in 2000 at a cost ($21 million) approximately the same in inflated dollars as the original construction price. Renovations between 1999 and 2000 included the SkyCity restaurant, SpaceBase retail store, Skybeaminstallation, Observation Deck overhaul, lighting additions and repainting.

A renovation of the top of the Space Needle began in the summer of 2017, to add an all-glass floor to the restaurant, and replace the observation platform windows with floor-to-ceiling glass panels to more closely match the 1962 original concept sketches, as well as upgrades and updates to the internal systems. Called the Century Project, the work was scheduled to finish by June 2018, at a cost of $100 million in private funds. The designer is Olson Kundig Architects and the general contractor is Hoffman Construction Company. The rotating restaurant’s motor was replaced, the elevator capacity was increased by adding elevators, or double -stacking them, and the energy efficiency of the building was improved with the aim of achieving LEED Silver Certification. The temporary scaffold’s 28,000-pound (13,000 kg), 44,650-square-foot (4,148 m2 ) platform under the top structure was assembled on the ground, and then lifted by cables 500 ft (150 m) from the ground to the underside of the structure, controlled by 12 operators standing on the platform as it was raised. The platform was made by Safway Services, a company specializing in unique construction scaffolding.

The space reopened in August 2018 as the Loupe, an indoor observation deck.

A skywalk extends out over the Grand Canyon in this view from the incomplete building that houses the skywalk, on the Hualapai Indian Reservation, Arizona February 28, 2012. The tiny Hualapai nation, in a bold move that could serve as a test of the limits of the sovereign power of Native American tribes over non-members, exercised its right of eminent domain last month to take over the management of the site and kick out the non-Indian developer. The dispute over the potentially lucrative Skywalk — which all agree could draw up to 3,000 visitors a day — pits the tribe’s sovereign rights over a site it sees as its economic lifeblood against a developer’s contractual right to manage the attraction for 25 years and share the profits. REUTERS/Robert Galbraith (UNITED STATES – Tags: BUSINESS SOCIETY TRAVEL)

The Grand Canyon Skywalk is a horseshoe-shaped cantilever bridge with a glass walkway at Eagle Point in Arizona near the Colorado River on the edge of a side canyon in the Grand Canyon West area of the main canyon. USGS topographic maps show the elevation at the Skywalk’s location as 4,770 ft (1,450 m) and the Colorado River’s elevation in the base of the canyon as 1,160 ft (350 m). They show that the height of the precisely vertical drop directly under the skywalk is between 500 ft (150 m) and 800 ft (240 m).

In 2015, the attraction passed one million visitors. Commissioned and owned by the Hualapai Indian tribe, it was unveiled on March 20, 2007, and opened to the general public on March 28, 2007. It is accessed via the Grand Canyon West Airport terminal, or a 120-mile (190 km) drive from Las Vegas. The Skywalk is east of Meadview and north of Peach Springs, with Kingman being the closest city of some size.

Design And Construction

David Jin, an entrepreneur who had been involved with tourism and the Hualapai Nation for some time, had the idea of extending a platform out over the edge of the Grand Canyon. With the help of architect Mark Ross Johnson, that idea evolved into a rectangular walkway and eventually the “U”-shaped walkway that has now been constructed.

The overall Skywalk width is 65 feet (20 m). The Skywalk length extending out from the post supports closest to the canyon wall is 70 feet (21 m). The outer and inner 32-inch-wide (810 mm) by 72-inch-deep (1,800 mm) bridge box beams are supported by eight 32-by-32-inch (810 mm × 810 mm) box posts having four posts on each side of the visitor’s centre, once completed. The eight posts are anchored in pairs into four large concrete footings that are in turn anchored to the bedrock by ninety-six 2 1⁄2-inch-diameter (64 mm) DYWIDAG (acronym pronounced Doo-Wee-Dag) high strength steel threaded rod rock anchors grouted 46 feet (14 m) deep into the rock.

The Skywalk deck has been made with four layers of Saint-Gobain Diamant low iron glass with DuPont SentryGlas interlayer. Deck width is 10 feet 2 inches (3.10 m). The Skywalk glass sidings are made with the same glass as the deck, but fewer layers (two) bent to follow the walkway’s curvature. The glass sidings are 5 feet 2 inches (1.57 m) tall and designed for high wind pressures. The Skywalk deck was designed for a 100-pound-per-square-foot (490 kg/m2 ) live load along with code-required seismic and wind forces.The foundation can withstand an 8.0 magnitude earthquake within 50 miles (80 km).

 Fine-tuning of the project occurred after a wind loading and pedestrian induced vibration analysis. Two tuned mass dampers were installed inside the outer box beam and one inside the inner box beam at the furthest extension of the Skywalk to reduce pedestrian footfall vibration. The walkway can carry 822 people that weigh 200 pounds (91 kg) each without overstress, but maximum occupancy at one time is 120 people.

The Skywalk was assembled on top of the canyon wall in line with its final placement and moved into final position by a jack and roll rig. The Skywalk infrastructure itself weighs a little over 1,000,000 pounds (450,000 kg), without counterweights, but including the tuned mass dampers, railing hardware, glass rails, glass deck and steel box beams. At the time of roll-out, the Skywalk weighed approximately 1.6 million pounds (730,000 kg). The process was completed in two days.

Astronauts Buzz Aldrin and John Herrington attended the opening ceremony on March 20, 2007. A National Geographic documentary film on the construction of the Skywalk has been published.

Cornerstone Of A Larger Plan

According to Hualapai officials, the cost of the Skywalk was $30 million. Future plans for the Grand Canyon Skywalk complex include a museum, movie theatre, VIP lounge, gift shop and several restaurants, including a high-end restaurant called The Skywalk Café, where visitors will be able to dine outdoors at the canyon’s rim. The Skywalk is the cornerstone of a larger plan by the Hualapai tribe, which it hopes will be the catalyst for a 9,000-acre (36 km2 ) development to be called Grand Canyon West; it would open up a 100-mile (160 km) stretch along the canyon’s South Rim and include hotels, restaurants, a golf course, casinos, and a cable car to ferry visitors from the canyon rim to the Colorado River, which has been previously inaccessible.

Tourism, Access, And Protection

Access to the Skywalk can be made from Las Vegas, Nevada in the north of Kingman, Arizona, in the south, via Highway 93. The routes converge (at CR 7/Buck and Doe Rd) near Diamond Bar Road.

There are several packages available for purchase at the airport terminal visitor centre. Every package includes parking at the terminal and shuttle bus transportation to the two scenic viewing areas and the Hualapai Ranch. As of 2015, the final 9 miles (14 km) of the county-maintained road to the attraction has been paved and is now accessible to everyone. In addition to admission, visitors may purchase professional photographs of their visit to the Skywalk in the gift shop, as personal cameras are not allowed on the Skywalk itself. Along with other personal property, they must be stored in a locker before entering the Skywalk. Besides the Skywalk, the Eagle Point offers other activities, i.e., Native American dances in the amphitheatre, Native American gift shop, and Native American Village with dwellings of the region’s indigenous tribes such as Hualapai, Plains, Hopi, Navajo, and Havasupai. Buses connect all the points within the Grand Canyon West area.

Amrita Batra
Associate Editor
Civil Engineering and Construction Review

Your first glimpse of Bosjes Estate just might jolt you out of your seat. It might look like a spaceship in the middle of the Cape Winelands’ Breede Valley. Just a 90-minute drive from Cape Town and you will arrive at  South Africa’s newest hotel and restaurant, which opened in February on a historic 2,500-acre farm. It is unlike anything the wine country has ever seen, thanks to a futuristic new chapel.

The new chapel, set within a vineyard, is designed by South-African born Coetzee Steyn of London-based Steyn Studio. The construction started in 2013 and was completed in December 2016. Its serene sculptural form emulates the silhouette of surrounding mountain ranges, paying tribute to the historic Cape Dutch gables dotting the rural landscapes of the Western Cape. The 6 m high building was conceived as a lightweight, dynamic structure that appears to float within the valley, an effect accentuated by an adjacent reflective pond.

Rainwater is discharged from the middle of the roof via a submersible pump with sump, through a pipe cast into the concrete whose outlet is hidden under the lowest part of the roof, where it meets the reflection pond.

Construction

The crisp white form is conceived as a lightweight and dynamic structure that appears to float within the valley. A reflective pond emphasises the apparent weightlessness of the structure. Elevated upon a plinth, the chapel rises from the flat land it sits upon, providing a hierarchical focal point within its surroundings. 

New planting, including a vineyard and pomegranate orchard creates a lush green oasis on the otherwise exposed site. Steyn Studio was asked to design a chapel to be built on the vast grounds of the estate. The necessary conditions were that Bosjes Chapel would become an iconic building, a landmark in its category. And this is what the architects delivered, drawing on haughty sources of inspiration: the shape of the mountains that provide the backdrop.

The Roof

To achieve this visual result, the entire building had to be simple, unifying and fluid, while structurally efficient. Constructed from a slim cast concrete shell, the undulating roof rises to form six peaks – one at each corner and one in the middle of each long elevation. It is supported at four points where it falls dramatically to meet the ground. Here, expanses of glazing are framed in timber to give the appearance of crucifixes.

The intricate roof of the Bojes chapel measures 20 m long by 12 m wide and 6 m high at the top apex. The professional and project team selected shotcrete as the chosen project construction with a 1:50 concrete demo ‘cup’ constructed in the PERI Cape Town yard. The concrete demo proved invaluable in the planning of the project.

Interiors

Inside, a large and open assembly space is created within a simple rectangular plan. Highly polished terrazzo floors reflect light internally. The undulating whitewashed ceiling casts an array of shadows that dance within the volume as light levels change throughout the day. This modest palette of materials creates a neutral background to the impressive framed views of the vineyard and mountains beyond.  To allow for thermal movement, the roof and floor structures are completely separated by a service channel around the perimeter at the point where the glass meets the floor.

Structure

Inspired by the simplicity of the Moravian Mission Stations established on Cape Dutch farms in the 19th century, the chapel lacks a spire – relinquishing a sense of significance in relation to its impressive natural surroundings. An open embrace that invites in, the chapel is also a space that extends outwards into the valley and mountains beyond, raising the awareness of God’s creation in the immediate environment.

In order to keep the structural form of the roof and assembly space pure, other elements of the building’s functional programme are either hidden within the plinth or discretely within the outer corners of the surrounding garden. To permit assembly, the entire surface was divided into eight mirror sections, and no less than 130 sections were designed as a guide. The roof’s simple yet complex shape required the use of 584 braces and more than 3 km of wooden slats installed on the trusses of the frame.

Lastly, the whole structure was covered with plywood, which had first been soaked for 24 hours to give it enough flexibility to follow the curves of the design. After this, 8,175 kg of steel rods were combined with spray-cast concrete to effectively create the roof. Though the structure appears weightless, the entire weight of the chapel rests on four hidden buttresses, each of which supports a vertical load of more than 50 tonnes.

Formwork

Despite the building’s apparent simplicity, the conception and construction of the roof was anything but banal. All formwork was purposemade and was designed as a system of prefabricated trusses with a bent plywood skin. It took almost five months to construct the formwork on site. A 1:2 scale sample section of the roof was constructed in the contractor’s Cape Town yard to workshop all details and finishes.

Due to the unusual form of the shell, each reinforcing bar (top and bottom) had to be individually cut and hand-bent to fit. The concrete was poured in the form of shotcrete – pneumatically projected at high velocity through a hose. This had to be done from mobile platforms and was frequently delayed by strong winds and rain, taking six weeks instead of the two allowed in the original programme.

Amrita Batra
Associate Editor
Civil Engineering and Construction Review

The Empire State Building is a 102-story Art Deco skyscraper in Midtown Manhattan in New York City. It was designed by Shreve, Lamb & Harmon and built from 1930 to 1931. Its name is derived from “Empire State”, the nickname of the state of New York. The building has a roof height of 1,250 feet (380 m) and stands a total of 1,454 feet (443.2 m) tall, including its antenna.

The skyscraper, featuring 2.1 million square feet of rentable office space, stood as the world’s tallest building until the construction of the World Trade Centre in 1970; following its collapse in 2001, the Empire State Building was again the city’s tallest skyscraper until 2012. As of 2020, the building is the seventh-tallest building in New York City.

Construction

The design of the building changed 16 times during planning and construction, until it was ensured to be the world’s tallest building. But 3,000 workers completed the building’s construction in record time: one year and 45 days, including Sundays and holidays. Construction started on March 17, 1930, and the building opened afterward on May 1, 1931.

The construction itself is a model of efficiency, based on the emerging principles of industrialism, assembly lines and division of labour. To maintain the strict schedule, pieces like steel beams and stonework were prepared off-site, then delivered ready to be inserted into place by workers. A series of hoists and narrowgauge tracks inside the building moved the pieces to the topmost floors, while large external winches were used for heavy stone pieces. Workers perched hundreds of feet above street level as they riveted steel girders. While the project was considered very safe for the era and complexity, six workers died. As many as 3,000 workers were at the job site at one time, with the weekly payroll sometimes approaching $250,000. Because it would have been impossible to get all the workers down from the site, then back up again in a timely manner for their lunch break, food concessions were placed every few floors.

While the project was considered very safe for the era and complexity, six workers died. As many as 3,000 workers were at the job site at one time, with the weekly payroll sometimes approaching $250,000. Because it would have been impossible to get all the workers down from the site, then back up again in a timely manner for their lunch break, food concessions were placed every few floors.

The 80th, 86th, and 102nd floors have places where people can look at the city from high above. There is a steel mast on the top of the Empire State Building. The builders wanted to have an airship station on the roof, but the station was not opened.

Steel Structure

The Empire State Building is composed of 60,000 tons of steel, 200,000 cubic feet of Indiana limestone and granite, 10 million bricks, and 730 tons of aluminium and stainless steel. With its steel columns and beams, 62,000 cubic yards of concrete, 6,514 windows, and 73 elevators in 7 miles of shafts, the Empire State Building is a feat of 20th-century engineering.

The steel columns and beams form a stable 3-D grid throughout the entire structure. But since such closely spaced column grids obstruct open spaces in buildings, there are virtually no open spans, or column-free spaces, on each floor of the Empire State Building.

The steel frame of the building was protected by iron oxide and linseed oil paint when it was delivered from the steel mill, and then it was covered with an asphalt coat to resist it from breaking down when it was brought into contact with cement. All the steel columns were fireproofed with cinder concrete, so all the steel is encased in concrete, which, of course, makes the building not only strong, but fireproof.

Exterior The Empire State Building’s art deco design is typical of pre–World War II architecture in New York. The modernistic, stainless steel canopies of the entrances on 33rd and 34th Streets lead to two-story-high corridors around the elevator core, crossed by stainless steel and glass-enclosed bridges at the second-floor level. Further, the exterior of the building is clad in Indiana limestone panels sourced from the Empire Mill in Sanders, Indiana, which give the building its signature blonde colour. Interior The Empire State Building was the first building to have more than 100 floors. It has 6,514 windows; 73 elevators; a total floor area of 2,768,591 sq. ft (257,211 m2 ); and a base covering 2 acres (1 ha). Its original 64 elevators, built by the Otis Elevator Company, are in a central core and are of varying heights, with the longest of these elevators reaching from the lobby to the 80th floor. As per the final specifications of the building, the corridor is surrounded in turn by office space 28 feet (8.5 m) deep. Each of the floors has 210 structural columns that pass through it and provide structural stability.

Innovative Systems The fact that the building is considered a New York City and National Historic Landmark has not slowed down its progress. In 2011, the Empire State Building was awarded LEED Gold for Existing Buildings certification as further recognition from the $550 million Empire State ReBuilding program. The Empire State Building is the tallest and most well-known building in the U.S. to receive LEED certification.

The Present Today, visitors can ascend to the Empire State Building’s observation deck for an unequalled view of New York City. It is open from 8:00 AM to 2:00 AM, seven days a week, and costs $18 for an adult ticket. This allows access to the 86th floor observatory. The 102nd floor is accessible as well but costs an extra $15. You can enjoy the view for free with the official Empire State Building Web cams.

Amrita Batra
Associate Editor
Civil Engineering and Construction Review