Building the Burj Khalifa:

Main: Chronological order
200 Mechanical, electrical and plumbing: air conditioning (temperature),
300 Safety – (getting everyone out) refuge rooms
300 Elevators– mention of transition from steam to motor and latched systems and electrical brakes and coping with load
100 Spire
100 Maintenance - Broadcast and communications floors, Mechanical Floors

Conc:
How it has progressed engineering and enabled more (buttress structure).
Future plans – The kingdom Tower in Saudi (1km into the sky)
Building potential: Space elevator, new arising problems, strength of materials, what that would mean and enable if possible.

Throughout history, progression and advancement in technology has fundamentally separated us from our evolutionary antecedents, enabling a life of greater comfort, extravagance and an increased ability to procreate and sustain ourselves. This improvement is especially apparent in the world of architecture and civil engineering, where there has been an unremitting ambition to surpass the existing boundaries, particularly with regards to height. The most renowned early example of a structure where height was key are the Pyramids of Giza where elevation was crucial in order to radiate power and divine authority. The tallest pyramid, standing at 146.5m, was built more than 4500 years ago, and remained the tallest manmade structure for the next 3800 years, until the 1300s when Lincoln Cathedral was built topping it by only 13.5m [1][2]. Following this, a series of cathedrals and churches continued to break and set new records [2]. The Eiffel tower was the next long term record holder, at a height of 300m, holding the record for the tallest structure up to 1930 when the Chrysler Building exceeded it by 19m [3][4]. Very shortly, after only 11 months, the Chrysler building was then bettered by its close neighbour the Empire State Building which was 381m high [5][6]. When built, the Empire State building had reached a milestone in skyscraper history, as it was the first ever structure that enabled a person to reach terminal velocity prior to hitting the ground should they jump off the top [6]. Following this, many Radio and TV towers were built during the 1950s and 60s [6]. This created stark difference in the expectations of buildings and towers, as while a tower is merely a structure that only needs to stand up and remain in its position, a building is an assembly where 50% of its height comes from floor plates which are habitable [6], thus meaning that it is far more challenging to construct a building compared to a tower or freestanding structure of equal height. Furthermore, it explains why as the record for the tallest buildings has gradually increased from elevated to extraordinary to extortionate with the constructions such as the World Trade Centre in New York (417m), the Sears/Willis Tower in Chicago (442m), the Petronas Towers in Malaysia (451m) and Taipei 101 in Taiwan (509m), all with technologies enabling us to build higher, none topped the Warsaw Radio mast in Poland (646m) and the KVLY-TV mast in North Dakota (629m), which remained the tallest manmade structures in history for 17- 46 years, until the Burj Khalifa was built in 2010 [6][7][8][9][10][11][12].
Taking just under 6 years to create, the Burj Khalifa (Burj Dubai) holds over 18 world records and is the world’s tallest manmade structure and skyscraper ever to exist or have existed at 828m from top to bottom. Until recently the spend on the Burj was a closely kept secret, however now rough figures of around $1.5 billion dollars/ £1 billion have been released. Ultimately, the reason for such an extravagant build was so that Dubai (UAE) received more international recognition as a city that welcomed business and tourism. Since the discovery of large oil reserves not long ago, there has been a continuous effort to diversify the economy by creating one that is tourism based aimed at the superrich. The architectural and engineering firm that took on such an outrageous project was Chicago based Skidmore, Owings and Merrill with the two vital roles of chief engineer and architect being played by Bill Baker and Adrian Smith. Both had countless years of experience under their belt and were eager to take on such a challenge that would test them to their limit. Before even deciding the complete final design and height of the build, the construction team had already begun laying the concrete piles for the foundations. This was unheard of in the construction industry, and was especially peculiar on such a large project where the slightest error could cost millions, however due to the large time constraints, it was necessary to get the project moving as quickly as possible. The project spanned over almost 6 years, and was completed in September 2009 to be opened in January 2010, facing many challenges on its way up through the skies including: wind load, the local geology, the speed of the project, the local temperature, the weight of the Burj on the Earth, ensuring fire safety to all inhabitants, and producing an elevator that was both strong and safe. It is also important to mention that when faced with particularly difficult challenges, such as the ones mentioned above, the engineers often sought inspiration from previous skyscrapers, and in some cases attempted to apply similar technologies on a new level in a unique way.

Design and Structure – Buttress Core Design:
The architectural design and structure of a skyscraper is fundamentally important to the building’s aspects, functionality and stability, particularly when a greater height is concerned and the wind becomes the largest acting load as the elevation of the structure rockets. This is why throughout history we have seen architects and civil engineers continue to make breakthroughs in the structures and designs used when making buildings enabling us to build further and further. We have seen this with the empire state building, the Sears tower, Taipei 101 particularly with regards to earthquake protection and on a whole new level with the Burj Khalifa. Materials and weight are also intrinsically linked with the design and structure of a building as all three variables play a key job in ensuring the permanence of the construction with regards to coping with the three main loads, load of the building (dead load), load of the people (live load), and most important with tall buildings, load of the wind.
When creating the design and structure of a building, the main considerations that are taken into account are the stability: this includes the gravity of the structure and the way the live and dead load are spread among the columns of concrete to produce an even load as well as coping with the wind load; the functionality: this includes the ability to maintain the Burj in its perfect state and the practicalities of living with a permanent design as well as providing the inhabitants of the Burj the best possible experience while they live there: and the aesthetics; this includes the way the Khalifa appears and affects the local skyline while part of the design is linked to the past of the surrounding area. The greatest of all the considerations is the wind, as while most of the way the live and dead load of a building are down to the type of foundations and ground work and materials used, and the functionality and the aesthetics of the assembly are something that can be worked around, the way the wind affects a construction is directly down to how the building was designed and structured and if not done correctly could deem the building uninhabitable.
Wind affects a building through a process known as vortex shedding. On a stereotypical rectangular shaped building such as the empire state building, as wind passes from one side to the other, the wind is pushed around the building as it is unable to pass through it, and in turn small tornados known as vortices form either side of the building. These areas of low pressure that form (why low pressure?) suck the building from side to side causing it to sway (the Bernoulli principle), reducing the stability of the building and potentially causing the inhabitants to feel sick. This is exactly what happened to the Hancock building in Boston, resulting in a major redesign, showing it is incredibly important to take into account the effects of wind. The engineers of the Willis Tower formerly the Sears tower faced a similar problem as in Chicago winds can reach up to 80kph. This can severely affect steadiness especially at a height of 412m. When considering the available opportunities, it was clear that a traditional internal steel structure wouldn’t be enough in protecting against the wind when testing was conducted. Instead an exoskeleton shape where most of the steel was moved from the inside of the building to reinforcing the outside was opted for. Furthermore the structure was separated into 9 separate pieces of different heights all with their own exoskeleton structure that were then put together to form one rock solid rigid structure that once constructed only swayed by only 15cm at the top, and was available to withstand winds of up to 90kph. Aside from being a design feature, altering the height of the individual pieces also plays a vital role in reducing the effect of vortex shedding on the building and was a technique also used by the engineers on Burj Khalifa in an effort to deal with the wind which will be later elaborated on. The Sears/Willis tower is an important example to observe, as it shows that with clever manipulation of design and materials extremely tall buildings are possible even in areas of high speed winds like Chicago.
When the engineers of the Burj Khalifa set about how they were going to stop the wind from causing the Burj to sway, they realised that rather than trying to resist the effect of the wind, it would be far easier to prevent the process of vortex shedding from occurring, as with winds of up to 240 kph in the Arabian desert, it would be unrealistic to try and battle the elements. So instead of a stereotypical rectangular shape, the architects designed a curved shaped structure in collaboration with the engineers that would “confuse” the wind, disrupting the power of the vortices due to the unpredictable shape of the structure and thus resulting in an even distribution of pressures surrounding the building and significantly reducing the effect of the wind on the building. To reach the conclusion as to what would be the best possible design, the engineers did over 40 tests in the wind tunnel. This led them to make 3 significant modifications to what was already a strong structure. The first was reducing the width of the tower higher up, i.e. setting the wings back in a spiral to provide a variety of different sized floor plates. This contributed to the effect of “confusing” the wind and made it difficult for the wind vortices to organise themselves as the shape of the building regularly changed. Furthermore the setbacks were cleverly planned so that all the concrete columns throughout the Burj were cleverly aligned to create a smooth load path throughout the building thus enabling the building to cope with the effect of gravity better. The second modification was to alter the position from which the Burj stands relative to the wind direction thus causing its effect of wind confusion to be maximised on the strongest most violent wind, in turn meaning maximum safety from wind. The final major modification to the design was softening the edges of the outer buttresses at both ground level and setback levels thus maximising the effect of wind confusion as suggested by the wind tunnel tests. (Why?)
This entire Design and structure is known as the Buttress Core and was essential to building and engineering of the Burj Dubai. The buttressed core represents a modified and developed design of the Tower Palace III also designed and engineered by Skidmore, Owings & Merrill LLP (SOM). As well as being able to cope with wind effects it also has an enormous outer surface area, thus providing the inhabitants with maximum ability to see outside windows and enjoy the view. Furthermore its unique design (based of the hymenocallis flower) and structure which has a central hexagonal core which is buttressed by 3 wings that extend from it terminating in thickened hammer head shaped walls, provide it with all the torsional resistance necessary to cope with such a large structure. (The torsional resistance of an object is its ability to resist twisting under strong force.) Together, all the unique features and characteristics of the buttress core design come together to provide a stable, aesthetic and practical design that is both cost-effective and feasible.

Foundations, Groundwork and Podium:
Foundations and groundwork are a vital part to building as they provide the base layer to which the entire assemble will be held on and kept in position by. Without stable foundations a building could subside and potentially collapse. When foundations are being laid a particularly important consideration as well as lateral movement is also vertical movement as the weight and force of the building presses down on to them resulting in them sinking. The level of sinking can vary depending on the quality of the foundations and the approach that has been taking when laying the foundations and groundwork. Traditional building foundations work by sinking large piles down deep enough for them to sit on hard rock and be held in place by the immovable hard rock. These piles will then act as anchors to the building keeping them in place.
An interesting example to look at when considering foundations is the Empire State Building, because being a building in New York, where there is a significant amount of Granite within the ground it makes it significantly easier to lay down foundations. Piles were merely driven 4-5 metres deep where they reached the granite and sat in place. This is known as end bear piling. The Burj however was significantly more difficult to create strong foundations for as the underlying rock was incredibly weak and wouldn’t have the strength to remain still under the use of traditional techniques. Beneath the initial 3-4 m of desert sand, lies weak sandstone followed by weak limestone, none of these are suitable to for placing traditional piles into for 3 main reasons. Firstly because due to the weak rock, there will be a significant lack of friction between the piles and the rock, thus meaning that the piles will be very easily subject to movement and therefore won’t be stable. In addition, the weak rock will be very easily moved by small changes in the weather and climate, thus making the piles susceptible to movement. Thirdly, as holes are created for the concrete to be poured into once the piles have been placed into the ground using one of the variety of techniques available, before the concrete has been given a chance to enter the pile, the hole has already been filed with some of the sand/weak rock that lies within the ground. This was a unique problem that required a unique solution. To tackle all 3 problems, a special method was used, where holes were drilled and filed with a unique special flexible polymer (name was kept hidden as a trade secret) that stopped any sand or rock from entering the holes however enabled the drill to continue digging down to 50m. At this point the drill was removed and a concrete pump was send through the polymer down to the bottom of the 50m whole where concrete was pumped to fill up the whole and set into a pile. Due to the unique nature of the polymer, the concrete was able to displace it without mixing with it and thus causing the polymer to gradually rise out of the ground as the concrete filled up the hole. This was done 192 times to create incredibly strong concrete foundations which enabled a massive amount of friction between the 2 surfaces, anchored the piles into position due to the depth making them practically immovable in local weather, and made sure the only concrete made up the pile. This type of piling technique is known as skin friction piling.
On the foundations sit a 3.7m thick podium of self-consolidating concrete constructed over 4 separate pours (three buttress wings and the core). The raft itself required 12500 cubic metres of concrete and had regular steel reinforcement placed in the centre of it at intervals of 12 inches. This podium will act as the base of the entire structure being the junction between the 500 thousand tonne structure itself and the 50m deep concrete piles that anchor the Burj in place.
Construction:
When building large structures the key aspects which need to be taken into account are the strength of materials, the speed at which they can be erected, and their effect on the foundations (weight). When constructing the Monadnock building in Chicago, stone was used as the main building material. This was incredibly problematic and it resulted in an extremely heavy building which eventually sank by half a metre, clearly showing architects and engineers that an alternative material was required. Later on, when the same architect was then commissioned to build the Fuller building in New York, he decided to instead use a giant structure of steel made water resistant by a thin layer of masonry on the surrounding walls. This made the building both very strong and light, allowing thin walls to be used and therefore better cost efficiency as more floor space was available for use.
The engineers took this one step further and used a structure made of concrete reinforced with steel, making it rigid and solid. However, with such a large structure, they now faced the problem of speed. As a result they turned to the Empire State Building for inspiration, which employed as special technique of prefabricating large sections of the building and merely craning them into the correct position thus making construction far quicker and less stressful. This was then taken one step further with the Burj Dubai, where a relatively new system known as Jump forming was used to create walls and floors at a rocket pace of up to 1 floor every 3 days. The system worked by starting at the bottom of the building where workers assemble steel cages that form the skeleton for floors and walls. It is important to note that special anchor bolts where used to connect floors with each other. Anchor bolts are regularly placed pieces of steel that protrude from the previous floor/wall that act as the glue between two walls/floors keeping them together. Once complete special Australian cranes known as Kangaroo cranes hoist the cage up to the appropriate floor and slot them into place on top of the anchor bolts of the previous floor and into already placed moulds known as Jump forms. The mould is then filled with concrete which takes about 12 hours to dry, at which point the jump form is released and is slid vertically upwards to act as the mould for the next floor. This transition from one floor to the next usually takes about two hours and is done by hydraulic pistons. Due to the extreme temperatures of Dubai, several measures had to be taken to ensure that the concrete doesn’t set before reaching the appropriate point. Firstly, ice and water were mixed into the concrete mix to make sure that it remains cool. Furthermore, the concrete we only pumped at night where the temperatures were cool enough for the concrete to not set too early. These were the two main measures that ensured the concrete set properly to form strong rigid walls and floors that could be continued to be built on.
External Cladding:
The external cladding of any building is important as not only does it make up a large part of the aesthetics of the structure but it also plays a central role in ensuring that the construction maintains the initial function that it is made for. In the Burj Dubai’s case, the main concern will be the temperature of the inside of the building, as with particular types of cladding such as glass, the structure can turn into a greenhouse, baking those inside. This effect would be exacerbated by the fact that temperatures in Dubai generally hover around 45 degrees centigrade in the shade, thus making it critical that within the tower, the inhabitants remain cool. When considering the options available, it was decided relatively early that glass would be the preferred option as it meets the aesthetic requirements of the client and complements the local skyline rather than acting as an eyesore. However to stop the boiling of the residents of the Burj, special glass was used that cleverly reflected the heat of the sun while maintaining a great view looking from and onto the Khalifa. The outer pane of each piece of glass cladding is coated with a thin layer of metal which reflects Ultra Violet rays from the sun which would normally enter the building while the Inner pane then reflects the Infra-Red radiation emitted from the desert sand with a thin layer of silver. Both of these layers work together to ensure that the inhabitants of the Burj Dubai remain cool.