According to the Council on Tall Building and Urban Habitat, The Burj Khalifa is the world’s tallest building based on height to top, height to highest occupied floor, and height to architectural top. The building is a multi-use Burj Dubai development tower with an approximate total area of 460,000 meters squared. It includes parking facilities, shopping malls, entertainment centers, offices, hotel, and residential (AL-KODMANY 2013, p. 12). The decision to construct this building was initiated by government’s idea to diversify from an oil-based economy to one that is tourism and service oriented. It is 828 meters tall and comprises three basement levels and one hundred and sixty-two floors. The construction of this tower commenced in January 2004, with excavation works. In 2003, Emaar properties intended to build the world’s tallest building. In this pursuit, they approached several architects who were capable of performing the design works. Therefore, they held a two-week completion and Smith emerged the best contestant (Abdelrazaq 2008, p.35).
The tower employ’s a record-breaking 142,000 square meters of glass 330,000 cubic meters of concrete, 39,000 metric tonnes of steel rebar, and the man-hour that was involved in building was 22 million man hours. The structure below the spire is entirely concrete reinforced while steel is employed in the spire above the observation floor. Architecturally, the tower is a transition from a stable base expression to a vertically expressed middle section polished stainless steel projected metal fins and glass. The tower is located at the center of downtown Dubai, United Arab Emirates (BENNETT 2008, p.13).
The design of the Tower was derived from geometry of the desert flower that is indigenous to the region and its patterning systems embody the Islamic architecture. The tower massing is organized around a central core with three wings. Each of these wings has four bays and at every seventh floor of the tower one of the outer bays setback from the structure as the building spirals upward the sky. This flower’s “Y” shape design makes the tower capable of minimizing wind loads and provides a simple structural design plan to facilitate its construction (KALLEN 2014, p. 43). The design is such that the lateral forces acting on the wings are counteracted by the supporting central core. The tower central core and wings have rigorous geometry that aligns them in such a manner that provides the structure with adequate strength to overcome torsion forces and also provides natural light and maximizes the viewing space. The thickness of central core walls vary from 1300mm to 500mm and are linked through composite link beams at each level. The link beam’s depth is limited and thus in particular areas of the core wall ductile composite link beams are provided. They are made of steel shear plates or I-shaped structural steel beams that have embedded shear studs in the concrete section (BINDER 2006, p. 23).
Figure 1: Burj Khalifa Building
The framing system of hotel and residential consist of 200mm to 300mm concrete reinforced flat plate slabs that span nearly nine meters between the central core wall and the exterior columns. As the wind is critical to the stability of the tower, the foundation system of the tower is pile supported raft foundation (KALLEN 2014, p.23). The tower was constructed with high-performance steel reinforced concrete mixed in such a way as to low-permeability and to provide high-durability in the building columns and walls. The tower is elected on a 3700mm thick high performance reinforced concrete pile supported raft foundation. Concrete has become highly competitive in the construction of high-rise buildings. The availability of high-strength concrete, high-flow concrete, and advances in technology made it easier to plan. In addition, concrete requires less skilled labor thus it was quite appropriate for this in Dubai as the skilled labor in the region is scarce (THOMAS 2009, p. 45).
Concrete was also viable in this project since it is easily to predict with a high degree of accuracy the structural behavior of concrete made structures without fully application of computer analytical tools. The exterior cladding of the tower is designed of textured stainless steel and reflective aluminum panels with a number of smaller fins tubes. This design was critical in this building in order to resist high temperatures in the desert where it is located. Furthermore, the glass panels that were each hand-cut were used in cladding the exterior of the structure to reduce the temperatures (BINDER 2006, p.34).
Some of the significant risks factors included lifting and carnage of materials to such a height. In this regard, sophisticated equipments were used, and prior analysis was carried out to ensure that the systems could not fail. The consistency of the concrete mix is essential for maintaining the stability of the structure (BRUNN 2011, p. 145). Notably it was not possible to create a concrete mix that could withstand the high temperatures and at the same time bear the enormous weight. Therefore, the concrete was poured at night when the humidity was high, and the air was cooler. Steel and aluminum are vulnerable to corrosion if exposed to extreme weather conditions. This issue can result to collapsing of the building that can culminate to serious safety problem.
The building is equipped with visual monitors and communication system that can disseminate emergency information to both non-affected and the affect occupants as part of the fire emergency system. The information the system can release includes the immediate incidence situation and instructions to the building occupants (THOMAS 2009, p.122). The emergency instructions are designed to circulate via live or pre-recorded messages within the entire building or in some sections of the tower. The tower has 58 elevators of which ten are enhanced for emergency evacuation. Three are designed for use by the firefighter emergency rescue, and only one of these three can reach floors above 111th while the rest can only reach 111th floor. The tower has several outlets in each floor connecting to pressurize and fire rated exit staircases.
In constructing this tower, dimension stones could have been used since they have similar properties to concrete. However, dealing with stone is not an easy task and thus it was not practically possible to use stones in its construction. Another factor to consider is the availability of the stones and the labor. Stones are a rear commodity in Dubai. In addition, both concrete and stone are weak in tension and thus a reinforcement is required if they are to be used in an area where they will encounter considerable tensile stress. With the concrete, it is easier to mold and to include rebar while pouring (CARTER 2006, p.103). This technique cannot be applicable while stone and thus stone could not be used. Wood could have been used as an alternative to steel and aluminum as it has excellent properties. However, despite its unique properties, a lot of wood would be required to achieve an enormous amount of strength. In addition, wood may easily be damaged by fire, and it is also less stable. Consequently, concrete was the material of choice because its properties could also be modified to meet the desired standards.
In today’s construction contractors and project developers commence the process of development by managing out risks at the initial stages. A high concrete mix blend along with other measures for ensuring the durability of the building was employed in the first phase. Economic, cultural, environmental, and sociological factors have a high impact what useful life span of building could be (SCHULTE-PEEVERS 2010, p. 56). The changing need of the government and the changing face of the Dubai city will at one time cause the building to be obsolete. The designer’s life span is in most cases imprecise due to factors such as
The environment surrounding the building
The quality of the initial construction works
The degree and the quality of maintenance
It is good to acknowledge that these factors may vary from place to place and in the structure itself. Therefore, the life cycle of the Burj Dubai toe will greatly be influenced by these factors. Appraisal of the tower at various stages in its life may provide a clear picture of its life cycle. A post-construction assessment indicates that the building can last for 100 years. In the Dubai and the Gulf area substructures are exposed to a shallow water table with a high level of salinity. The salinity is likely to cause corrosion to the embedded steel framework that will cause the building to weaken. At this stage, the building will not be able to perform remarkably well under wind as per the initial design (BRUNN 2011, p.12). Probably the foundation will also not be in a position to withhold the enormous weight of the structure. A mid-life tower appraisal needs to be done in order to determine the maintenance work that will be required to make sure that it reaches its design life. Ideally, the tower will have outlived its original purpose. Therefore, flattened will eventually be done (CARTER 2006, p.42).
The systems and material employed in building Burj Dubai are not particularly new. What can be termed new are the technology and the innovative ways in which the materials have been combined or used to fulfill the client’s needs and to optimize the performance. Hence, the designing of material could have been altered at an early stage to expand the life span of this tower. The natural monumentality of tall building resulting from their size makes their architectural appearance critical in any urban context where they rise. Therefore, constructing any tall structure requires careful study of artistic competence of the new structure within the existing urban environment. Some structural systems for tall structures have had critical implications for the building esthetics as others have had only minor impacts. Innovative structural systems could be incorporated into sustainable construction. Finally, evolving the system must be seriously investigated in terms of structural economy and efficiency. Cost analysis can be done to determine the comparative cost- effectiveness of altering the systems while considering a variety of geometric parameters. Such a study may indicate whether the complexity involved in this building would justify the alteration of the structural material and still remain within the constraint of limited resources.
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