Burj DubaiReport about Concept, Design, And Construction of Burj Dubai.

Instructor Student Name

: :

Prof. Ossama El-Saeed Ahmed Essam, Mostafa Atteya,

Ramez Nazir, Mohamed Salah.

Contents Introduction Structural Analysis Foundations Wind Engineering Construction References

IntroductionThe Burj Dubai Project is a multi-use development tower with a total floor area of 460,000 square meters that includes residential, hotel, commercial, office, entertainment, shopping, leisure, and parking facilities. The Burj Dubai project is designed to be the centerpiece of the large scale Burj Dubai Development that rises into the sky to an unprecedented height of 828 meters and that consists of more than 160 floors. Burj Khalifa (formally Dubai) is the new tallest tower in the world. Construction began on 21 September 2004 & was completed on 1 October 2009. The building was officially opened on 4 January 2010. The Client of Burj Dubai Tower, Emaar Properties, is a major developer of lifestyle real estate in the Middle East; Emaar put a total investment of US$ 1.5 billion in the Burj Dubai project. The tower is designed by Skidmore, Owings and Merrill (SOM), Turner International has been designated by the owner as the Construction Manager, and Samsung Joint Venture (consisting of Samsung, Korea base contractor; Besix, Belgium base contractor; and Arabtec, Dubai base contractor) as the General Contractor. The design of Burj Dubai Tower is derived from geometries of the desert flower, which is indigenous to the region, and the patterning systems embodied in Islamic architecture. Tallest Building in the world

From the head start , it has been intended that the Burj Dubai be the Worlds Tallest Building. Burj Dubai fulfils all three criteria for tall buildings of the Council on Tall Buildings and Urban Habitat (CTBUH). The CTBUH ranks the worlds tallest buildings based on Height to Architectural Top, Height to Highest Occupied Floor and Height to Tip. Burj Dubai is the tallest skyscraper to top of spire: 828 m Building with highest occupied floor in the world163rd floor Highest outdoor observation deck in the world (124th floor) at 452 m World's highest elevator installation, situated inside a rod at the very top of the building World's fastest elevators at speed of 64 km/h (40 mph) or 18 m/s Highest vertical concrete pumping (for a building): 606 m World's highest installation of an aluminum and glass facade, at a height of 512 m World's highest New Year fireworks display

Architectural ConceptThe context of the Burj Dubai being located in the city of Dubai, UAE, drove the inspiration for the building form to incorporate cultural and historical particular to the region. The influences of the Middle Eastern domes and pointed arches in traditional buildings, spiral imagery in Middle Eastern architecture, resulted in the tri-axial shape of the building

Main Components of the towerBurj Dubai includes163 habitable floors plus 46 maintenance levels in the spire and 9 parking levels in the basement, with a Floor Area of 309,473 m2. The Residences The worlds most prestigious address will be home to a select few. With 900 residences including studios and one, two, three and four-bedroom apartments, The Residences at Burj Dubai are designed for the connoisseur. The homes are spread over levels 19-108 of the tower. For the convenience of homeowners, the tower is divided into sections with exclusive Sky Lobbies on Levels 43, 76 and 123. There are state-of-the-art fitness facilities including jacuzzis on Levels 43 and 76. The Sky Lobbies on 43 and 76 both have swimming pools and a recreational room that can be utilised for special gatherings and receptions. Other facilities for residents include a private library, an upmarket convenience store, The Gourmet Market, and a meeting place. Valet parking will be provided for guests and visitors alike. The Corporate Suites The Corporate Suites are located on the highest levels of the tower. They occupy 37 floors, with the top three floors merged into a single office. The entrance lobby is at the Concourse of the tower. In addition to valet parking, express lifts take office visitors directly to a lounge lobby at Level 123.

The observatory On level 123, At the Top, Burj Dubai, is a must-see attraction and offers breathtaking views of the city and the surrounding emirate. The Offices A complement to The Corporate Suites is The Offices, a 12storey annex with direct access to Burj Dubai and The Dubai Mall. Parking spaces for The Offices will be offered at the mall and the tower for the convenience of tenants. The Offices have a total area of 337,000 sq ft. Armani Hotel Dubai The world-first Armani Hotel Dubai. From the room designs to the carefully selected textiles and fabrics, to the impeccable service, every aspect of the Armani hotel experience will bear the signature of fashion legend Giorgio Armani. Offering 160 guest rooms and suites, restaurants and a spa, and covering more than 269,000 sq ft, Armani Hotel Dubai brings to life the Stay with Armani promise, an exceptional experience defined by the highest standards of aesthetics and service excellence. Mechanical Floors Seven double-storey mechanical floors house the equipment that bring Burj Dubai to life. Located every 30 storeys, the mechanical floors house the electrical sub-stations, water tanks and pumps, air-handling units etc, that are essential for the operation of the tower and the comfort of its occupants. Broadcast and Communications Floors The top four floors have been reserved for communications and broadcasting. These floors occupy the levels just below the spire.

Architectural plan of a typical residential floor

Main Structure & DesignThe tower superstructure of Burj Dubai is designed as an all reinforced concrete building with high performance concrete from the foundation level to level 156, and is topped with a structural steel braced frame from level 156 to the pinnacle. Designers purposely shaped the structural concrete Burj Dubai Y shaped in plan to reduce the wind forces on the tower, as well as to keep the structure simple and foster constructability. The structural system can be described as a buttressed core. Each wing, with its own high performance concrete corridor walls and perimeter columns buttress the others via a six-sided central core, or hexagonal hub. The result is a tower that is extremely stiff laterally and torsionally similar to a closed tube. The crowning feature of Burj Dubai is its telescopic spire comprising more than 4,000 tonnes of structural steel. It can be seen from 95 km (60 miles) away. The spire was built inside the building and jacked to its full height of over 200 meters (700 feet) using hydraulic strand jacks. The spire is integral to

the overall design, creating a sense of completion for the landmark. The spire also houses communications equipment .It utilizes a diagonally braced lateral system. The structural steel spire was designed for gravity, wind, seismic and fatigue in accordance with the requirements of AISC Load and Resistance Factor Design Specification for Structural Steel Buildings (1999). The exterior exposed steel is protected with a flame applied aluminum finish. Each tier of the building sets back in a spiral stepping pattern up the building. The setbacks are organized with the towers grid, such that the building stepping is accomplished by aligning columns above with walls below to provide a smooth load path. This allows the construction to proceed without the normal difficulties associated with column transfers. The setbacks are organized such that the Towers width changes at each setback. The advantage of the stepping and shaping is to confuse the wind. The wind vortices never get organized because at each new tier the wind encounters a different building shape. The center hexagonal walls are buttressed by the wing walls and hammer head walls which behave as the webs and flanges of a beam to resist the wind shears and moments. The core walls vary in thickness from 1300mm to 500mm. The core walls are typically linked through a series of 800mm to 1100mm deep reinforced concrete or composite link beams at every level. For the design of reinforced concrete link beams: 1. The conventional deep beam design method in the ACI 318-992

2. Strut-and-tie method in ACI 318-023 were used, with Appendix A enabling the design of link beams somewhat beyond the conventionally designed maximum deep beam stress limit. 3. In the case of members subjected to very large shear forces, embedded built-up structural steel sections were provided within the core of the concrete link beams to carry the entire shear and flexure demand.

The residential and hotel floor framing system of the Tower consists of 200mm to 300mm two-way reinforced concrete flat plate slabs spanning approximately 9 meters between the exterior columns and the interior core wall. Outriggers at the mechanical floors allow the columns to participate in the lateral load resistance of the structure by linking them to the shear walls; hence, all of the vertical concrete is utilized to support both gravity and lateral loads.

Structural AnalysisThe structure was analyzed for gravity (including P-Delta analysis), wind, and seismic loadings by ETABS version 8.4 . The three-dimensional analysis model consisted of the reinforced concrete walls, link beams, slabs, raft, piles, and the spire structural steel system. The full 3D analysis model consisted of over73,500 shells and 75,000 nodes. The reinforced concrete structure was designed in accordance with the requirements of ACI 318-02 Building Code Requirements for Structural Concrete.

Seismic LoadsDubai is situated towards the eastern edge of the geologically stable Arabian Plate and separated from the unstable Iranian Fold Belt to the north by the Arabian Gulf. The site is therefore considered to be located within a seismically active area. The Dubai Municipality (DM) specifies Dubai as a UBC97 Zone 2a seismic region with a seismic zone factor Z = 0.15 and soil profile Sc. The seismic analysis consisted of a site-specific response spectra analysis. Seismic loading typically did not govern the design of the reinforced concrete tower structure, but governed the design of the steel spire. Dr Max Irvine developed site-specific seismic reports for the project, including a seismic hazard analysis.

Dynamic AnalysisThe dynamic analysis indicated the first mode is lateral sidesway with a period of 11.3 seconds ,the second mode is a perpendicular lateral sidesway with a period of 10.2 seconds, torsion is the fifth mode with a period of 4.3 seconds

FoundationsHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system. The Tower foundations consist of a pile supported raft. The solid reinforced concrete raft is 3.7 meters (12 ft) thick and was poured utilizing C50 (cube strength) self-consolidating concrete (SCC). The raft was constructed in four separate pours (three wings and the center core). Each raft pour occurred over at least a 24 hour period. Reinforcement was typically at 300mm spacing in the raft, and arranged such that every 10th bar in each direction was omitted, resulting in a series of pour enhancement strips throughout the raft at which 600mm x 600mm openings at regular intervals facilitated access and concrete placement . Soil Investigation in 4 stages included 23 boreholes, in situ SPTs, 40 pressuremeter tests in 3 boreholes, installation of 4 standpipe piezometers, laboratory testing, specialist laboratory testing and contamination testing, 3 geophysical boreholes with cross-hole, tomography geophysical surveys. The groundwater in which the Burj Dubai substructure is constructed is particularly severe, with chloride concentrations of up to 4.5%, and sulfates of up to 0.6%. The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water. Due to the aggressive conditions present due to the extremely corrosive ground water, a rigorous program of measures was required to ensure the durability of the foundations. Measures implemented include specialized waterproofing systems, increased concrete cover, and the addition of corrosion inhibitors to the concrete mix, stringent crack control design criteria and an impressed current cathodic protection system utilizing titanium mesh. A controlled permeability formwork liner was utilized for the Tower raft which results in a higher strength / lower permeable concrete cover to the rebar. Furthermore, a specially designed concrete mix was formulated to resist attack from the ground water.

PilesThe Tower raft is supported by 194 bored cast-in-place piles. The piles are 1.5 meter in diameter and approximately 43 meters long with a design capacity of 3,000 tonnes each. The Tower pile load test supported over 6,000 tonnes.

The C60 (cube strength) SCC concrete was placed by the tremie method utilizing polymer slurry. When the rebar cage was placed in the piles, special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption, which greatly simplified the raft construction. The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25% fly ash, 7% silica fume, and a water to cement ratio of 0.32. The concrete was also designed as a fully self-consolidating concrete.

Piles Tests:1. Static load tests on seven trial piles prior to foundation construction.

2. Static load tests on eight works piles, carried out during the foundation construction phase (i.e. on about 1% of the total number of piles constructed). 3. In addition, dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium, i.e. on about 5% of the total works piles. 4. Sonic integrity testing was also carried out on a number of the works piles.

SettlementA detailed 3D foundation settlement analysis was carried out (by Hyder Consulting Ltd., UK) based on the results of the geotechnical investigation and the pile load test results. It was determined the maximum long-term settlement over time would be about a maximum of 80mm (3.1). This settlement would be a gradual curvature of the top of grade over the entire large site. When the construction was at Level 135, the average foundation settlement was 30mm (1.2).

The Wind Engineering of the Burj Dubai TowerWIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique. In this well established technique, (Tschanz, 1980), the model itself is rigid and is mounted on a fast response force balance. It is then tested in a boundary layer wind tunnel where it is subjected to a simulated wind in which the full scale wind profile and wind turbulence are properly reproduced at model scale. The advantage of the technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated. modal forces acting on the tower. The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towers dynamic response and the overall effective wind force distributions at full scale. For the Burj Dubai the results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towers stiffness and mass distribution. The building has essentially six important wind directions. Three of the directions are when the wind blows directly into a wing. The wind is blowing into the nose or cut water effect of each wing (Nose A, Nose B and Nose C). The other three directions are when the wind blows in between two wings. These were termed as the tail directions (Tail A, Tail B and Tail C). It was noticed that the force spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing, see Figure 2, than from the opposite direction (tail). This was born in mind when selecting the orientation of the tower relative to the most frequent strong wind directions for Dubai: northwest, south and east. Several rounds of force balance tests were undertaken as the geometry of the tower evolved and was refined architecturally. The three wings set back in a clockwise sequence with the A wing setting back first. After each round of wind tunnel testing, the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clients program. In general, the number and spacing of the set backs changed as did the shape of wings. This process resulted in a substantial reduction in wind forces on the tower by confusing the wind. Figure 3 is a plot of the response of original building configuration and the response after several refinements of the architectural massing. In these plots, the horizontal axis is the wind tunnel model frequency that canbe related to the recurrence interval for wind events and the vertical axis is proportional to the resonant dynamic forces divided by the square of the wind velocity. Towards the end of design aeroelastic model tests were initiated. An aeroelasatic model is flexible in the same manner as the real building, with properly scaled stiffness, mass and damping. It is more accurate than a force balance study since the aeroelastic interaction between the structure and wind is fully simulated, including such effects as aerodynamic damping, and also the statistics of the dynamic response can be measured directly providing a more accurate determination of the relationship between peak response and RMS response. For the Burj Dubai the modal deflection shapes were similar to those of a tapered cantilevered column.

Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single

machined metal spine in the model with outer shell segments attached to it. The aeroelastic model was able to model the first six sway modes. Bending moments were measured at the base as well as at several higher levels. Accelerations were also measured in the upper levels. In comparing the aeroelastic model test results with the more approximate force balance results it was found that the base moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results. A part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number. On a very tall slender tower like Burj Dubai, the challenge in the force balance method is to keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds, which entails reducing the Reynolds number. However, most of the differences between the force balance method and the aeroelastic method on Burj Dubai were due to approximations in the force balance procedure as applied to a highly tapered towered. Figure 4 illustrates the relative change in mean base moment coefficient on the aeroelastic model as a function of wind tunnel test speed for two wind directions. The fact that the moment coefficient dropped with test speed was a sign that Reynolds number effects were present. It can be seen, that the results tended to flatten out at higher test speeds indicating an asymptotic trend.

Figure 4 Effect of test speed on mean base moment coefficient for two wind directions relative to north On a circular cylinder the mean drag coefficient also drops at a certain critical Reynolds number but then climbs again as the Reynolds number is further increased. To be sure a similar phenomenon did not occur on Burj Dubai, special high Reynolds number tests at 1:50 scale were initiated using the model shown in Figure 1b. Due to size limitations of the NRC 9 m x 9 m wind tunnel the 1:50 scale model was limited to the top part of the tower only. The tests were run at wind speeds up to 55 m/s Measurements were made of the mean and instantaneous pressure distributions around six crosssections of the tower and were compared with similar measurements made at 1:500 scale in RWDIs 2.4 m x 1.9 m wind tunnel. Fig. 5 compares the sectional force coefficient on one of the crosssections at the two model

scales and shows very little difference. On the 1:500 scale model, tests were made both with and without vertical ribs that are a feature of the towers wall system in order to understand how much their effect was. At 1:500 scale the ribs were very small and thus had been left off for the main test program. The conclusions from the comparison of the high Reynolds number results with those at normal test Reynolds number were that the aerodynamic coefficients did indeed reach asymptotic values and that the 1:500 scale aeroelastic model and pressure model tests had reached high enough Reynolds numbers for the asymptotic state to be achieved closely enough for

engineering purposes. Thus no special Reynolds number corrections were needed. Furthermore, the 1:500 results with and without ribs showed that the effects of the ribs were very minor.

BUILDING MOTIONSBased on the High-Frequency-Force-Balance test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range. Initial predictions obtained in May 2003, at over 37 milli-g for the 5 year return period were well above the ISO standard recommended values. However, through a combination of reorienting the tower, adjusting its shape, modifying the structural properties, and more in-depth studies of the wind statistics for the region the predictions came down By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period and at a slightly higher level. About half of this improvement came about as a result of improved knowledge of the wind statistics and the rest through re-orientation, structural improvements and shape adjustments. improved. Several variations of tower height were tested using aeroelastic models. The accelerations were found to be significantly less than indicated by the force balance tests, down in the range of 12 milli-g. Part of this was due to the lower Reynolds number of the force balance tests, which put them in a range where Reynolds number effects

were beginning to become significant, but aerodynamic damping and a lower kurtosis in the dynamic response were also contributors. This indicates the importance of considering aeroelastic effects in cases where building motions are having important consequences. A range of damping values was considered in the test program. The acceleration results quoted above were all evaluated assuming a damping ratio for the building of 1.5% in its fundamental modes of vibration for each direction. This is a likely value for a slender concrete structure such as the Burj Dubai. For higher modes, which involved significant flexing of the upper part of the tower, lower damping values were examined also since the upper part of the tower is primarily steel. Higher modes contributed little to motions in the residential levels. Studies were also undertaken to examine adding supplementary damping systems such as tuned mass dampers but for the residential units the wind tunnel predictions indicated the motions would be well within acceptable limits without supplementary damping. The upper reaches of the spire are quite slender and supplementary damping systems are still under study for controlling those motions.

CLADDING LOADSCladding loads were evaluated through testing a 1:500 scale model instrumented with 1142 pressure taps and using the methodology described by Irwin, 1988. The procedures were essentially the same as for a tower of lesser height and the predicted 50 year peak suctions, including an allowance for internal pressures and stack effect, ranged from 2.0 kPa to 5.5 kPa. Most 50 year suctions were in the range 2.0 kPa to 3.5 kPa. The highest suctions were seen, as might be expected, near discontinuities in the surface geometry. Peak positive pressures ranged from 1.5 kPa to 3.5 kPa with the great majority being in the range 1.5 kPa to 2.5 kPa.

WIND CLIMATE STUDIESTo make full use of wind tunnel data so as to predict the dependence of wind loads and wind response on return period a good statistical model of the joint probability of wind speeds and direction is needed. In the course of the Burj Dubai studies local ground based data from several weather stations in the region were used, including most importantly the data from Dubai International Airport. Other stations examined were Abu Dhabi, Sharjah, Ras al Khaimah, and Doha. Gust data from all stations were merged into the equivalent a super-station to obtain an enlarged database and were analyzed using extreme value fitting methods to produce a relationship between gust speeds in the region and return period. The 50 year 3 second gust from this analysis was estimated to be 37.7 m/s in standard open terrain at the 10 m level. In addition the mean hourly data from Dubai were used to obtain a model of the parent distribution of hourly winds, from which mean hourly wind speed versus return period could be predicted. The analysis took account of the terrain around the airport, adjustments being made to correct the anemometer data for non-ideal exposure conditions using ESDU (1982) methods. This yielded a 50 year mean hourly speed of 23.5 m/s, again in standard open terrain conditions at 10 m. Depending on exactly which method one used to estimate the relationship between mean and gust speeds the corresponding gust was estimated to be in the range 35.7 m/s to 37.6 m/s. This agreed well with the value obtained from the super-station analysis. Therefore the parent distribution from Dubai International Airport was adopted as the appropriate statistical model to use with the wind tunnel results. An important question when designing a tower of over 600 m height is the nature of the wind velocity profile and wind turbulence in the upper levels. It is a large extrapolation to go from ground based data at the 10 m height to heights of over 600 m using standard assumptions about planetary boundary layer profiles. Therefore for Burj Dubai more direct measurements of upper level winds were sought. The closest station with balloon records was Abu Dhabi, where about 16 years of data were available taken on average about twice per day. The balloon readings gave wind speeds at various milli

bar levels. An interpolation procedure was used to extract out wind speeds at heights of 600 m, 1000 m and 1500 m, from which wind speeds versus return period could be estimated. However, this approach gave a considerably lower 600 m level 50 year wind speed than deduced from the ground based data and standard boundary layer models and it was conclude that the sparseness of the balloon data was probably the main reason. With only two readings a day it was unlikely that the balloons had captured the highest wind speeds in the period of record. A method of correcting for this was sought and the method adopted involved advanced meso-scale modeling techniques (Qiu et al, 2005). Information on upper-level winds can be obtained from the National Center for Atmospheric Research / National Centers for Environmental Prediction (NCAR/NCEP) global reanalysis data set. These data are based on world-wide meteorological observations interpolated to a 3-dimensional grid by means of meteorological modeling. The NCAR/NCEP Global Reanalysis combines 4-dimensional data assimilations of surface and upper air meteorological observation data, and provides outputs at six hour intervals on the global grid. Horizontal and vertical grid resolutions are too coarse on the global grid for a through study of local wind profiles at the study site (2.5 degree latitude by 2.5 degree longitude for most of the historical record, improving to 1 degree grids since 1997). To improve resolution for the Burj Dubai project the NCAR/NCEP reanalysis data was combined with a high resolution numerical meteorological model to reproduce high-resolution 3-D wind fields for a selection of historical high wind events in the UAE area, including a number of Shamals. The model known as the Fifth-Generation Penn State/NCAR Mesoscale Model (MM5), was used to predict mesoscale atmospheric circulations (Grell et al, 1995). MM5 is a widely used meteorological model that is based on solving the fundamental equations of atmospheric motion on a 3-dimensional grid. The model incorporates parameterizations for the various grid and subgrid scale physical processes that influence atmospheric conditions such as convection, cloud formation, precipitation, radiation, surface heat transfer and moisture flux etc. The main results of the MM5 studies can be summarized as follows. When stronger surface winds occur the ratio of 600 m mean winds to 10 m mean winds asymptotes towards a value of about 1.6 to 1.7, see Figure 5. This is slightly lower than the value of about 1.8 implied by the standard boundary layer assumptions. Comparing the peak winds at the upper levels computed by the MM5 method with the balloon records at Abu Dhabi indicated that the balloons generally missed the peak winds of each storm event resulting in an underestimate of extreme upper level wind speeds by about 15% on average. With this correction the balloon data indicated a 600 m level 50 year wind speed of about 36 to 38 m/s, compared with the value 41.7 m/s predicted from the ground data using standard boundary layer assumptions. The MM5 simulations also showed that the relationship between ground and upper level winds at Dubai was essentially the same as at Abu Dhabi. For design purposes it was decided to retain the standard boundary layer model assumptions. Thus the main benefit of the detailed MM5 studies was to lend confidence that the design wind assumptions used for the Burj Dubai were, if anything, slightly conservative, which is not inappropriate for such a monumental structure.

PEDESTRIAN WIND ENVIRONMENTThe comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information. Two aspects of pedestrian comfort were considered: the effect of the mechanical force of the wind and thermal comfort, bearing in mind air temperature, relative humidity, solar radiation and wind speed. The general methodology has been described by Soligo et al, 1997, and in the ASCE state of the art report on Outdoor Human Comfort and Its Assessment (ASCE, 2003). Initial wind tunnel tests used 1:500 scale models. Subsequently three 1:250 scale partial models were employed to

examine ground level areas, lower level terraces and higher level terraces in more detail, and to develop detailed mitigation measures.

Initial results from the thermal comfort study highlighted the need to introduce shade structures to avoid the strong adverse impact of solar radiation on thermal comfort in Dubai. A number of canopies and other types of shade structure were architecturally designed at ground level. Initial tests on the bare terraces indicated the potential for frequent uncomfortably strong winds. Further tests on the terraces showed that significant improvements could be obtained through a combination of parapet walls, overhead trellises, and vertical screens.

Construction of the Tower SuperstructureCurrently the tower is under construction and the foundation system (pile & raft) were completed in February 2005, including pile foundation and the raft foundation. The tower superstructure construction started in April 2005.

Tower Raft Foundation

The original construction program is very tight. To complete the project within 48 months, Samsung, Besix, Arabtech Joint Venture (SBAJV) established the following strategic approach: Achieve a three (3) day-cycle for structural works. Develop optimum transportation systems with large capacity high speed equipment. Utilize optimum formwork system to accommodate various building shapes along the building height. Develop organized logistic plans throughout the construction period. Apply all high-rise construction technologies available at the time of construction. Since the construction planning is extensive and cannot be covered in detail in this paper, only a brief summary of the major construction planning works will be covered in this paper.

Planning for the Concrete WorkPrior to the construction of the tower, extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved. The testing regimes included, but were not limited to the following programs: Trial mix designs for all concrete types needed for the project. Mechanical properties, including compressive strength, modulus of elasticity, and split tensile strength. Durability tests which included initial surface absorption test and 30 minute absorption test. Creep and shrinkage test program for all concrete mix design. Water penetration tests and rapid chloride permeability test. Shrinkage test program for all concrete mix designs. Pump simulation test for all concrete mix design grades up to at least 600 meters. Heat of hydration analysis and tests.

Heat of Hydration Mockup Test

Creep Test

Pump Simulation Test

Site Logistic PlanThe Burj Dubai site area is approximately 105,600m2 and encompassing the tower, the office annex, the pool annex, and the parking areas, divided into three zones (Zone A, Zone B, and Zone C).

Snap Shot of Site Logistic Plan (M+14)

Technologies used to achieve 3-day cycle The tower consists of more than 160 floors and is expected to be completed within a very tight schedule and 3-day cycle. Hence, the following key construction technologies were incorporated to achieve the 3-day cycle set for the concrete works: Auto Climbing formwork system (ACS) Rebar pre-fabrication High performance concrete suitable for providing high strength, high durability requirement, high modulus, and pumping Advanced concrete pumping technology Simple drop head formwork system that can be dismantled and assembled quickly with minimum labor requirements Column/Wall proceeding method, part of ACS formwork system Sequence of Construction and ACS Figures 9 and 10 depict the construction sequence of the tower and show the auto climbing formwork system (ACS), designed by Doka. The ACS form work is divided into four sections consisting of the center core wall that is followed by the wing wall construction along each of the three tower wings. Figure 10 also demonstrates the following construction sequence: the center core wall construction is followed by the center core slab construction; the wing wall construction is followed by the wing flat plat slab construction; and the nose columns are followed by flat plate and flat slab construction at the nose area. In addition, the core walls are tied to the nose columns through a series of multi-story outrigger walls at each of the mechanical levels. The construction of these outrigger walls are complex and time consuming because of the congestion of reinforcing bars at the connection zones. Therefore, the reinforcing bars are now replaced with structural steel sections to help resolve the design forces more effectively at the joints, eliminated the reinforcing bar congestion issues, and most importantly ensuring the joint integrity. These levels were constructed at a later stage and taken out of the critical path.

Figure 9: Sequence of Construction

Figure 10: Sequence of Construction

Rebar Pre-fabricationMost of the reinforcing bars for the core walls, wing walls, and the nose columns were prefabricated at the ground level. This rebar fabrication and pre-assembly method resulted in man quality control advantages and reduced the number of workers going up and down the tower. Moreover, whenever possible, the rebar was assembled in double story modules to speed up the vertical element construction time.

Rebar Prefabrication

Composite Link BeamsIn addition to connecting the vertical core wall elements rigidly for maximum strength and stiffness for the lateral load resisting system, the link beams are also used as means of transferring and equalizing the gravity loads between the vertical members (core-wall elements and nose columns). This equalizes stresses and strains between the members. Because the link beams are subject to large shears and bending moments, many of the link beams had to be composite (steel members encased in high strength concrete). Thus the steel beams imposed special demands on the cranes, pre-assembly and lifting methods.

Composite Link Beam Installation

Slab Formwork SystemFigure 13 shows a drop head system (also known as slab support system is specially designed to sustain a large combination of grid sizes, resulting in maximum reusability of formwork & economy) used for the slab construction. Meva Deck Drop Head slab formwork system was selected because of its installation simplicity, lightness, panel formwork material and strength, prop strength and stiffness, system flexibility and suitability for the slab hanging geometry, and allowance for cambering where needed.

Figure 13: Typical Slab Formwork System

The slab shoring system consists of four levels of shores and one level of re-shore to control the maximum loads in the slabs at the lowest level. However, the shoring props at the upper-most slab were left undisturbed Figure 14 provides an outline of the slab construction methodology used.

Figure 14: Outline of slab Construction Method.

Concrete PumpingThe utilization of high strength concrete and concrete pumping technologies was critical in the construction of the project. See Table 1 for a summary of the concrete types used for both the vertical and horizontal members.Table 1. Grade of Concrete in Tower

Direct concrete pumping and delivery methods required considerations for the following: selecting an optimum concrete mix design with excellent flow characteristics to minimize/avoid blockages; choosing equipment that has enough capacity to deliver concrete to the highest level, more than 160 floors up; designing a pipe line that can be installed with maximum construction efficiency; selecting equipment and pipe line system that work well with the sites overall logistics and planning; and maintaining quality control of the pumping system and placement method by monitoring all components of the system and ensuring the concrete properties required. A horizontal pump simulation test, shown in Figure 6, was performed, using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction/connections/concrete type, etc..

Major EquipmentTower Cranes Three high capacity self climbing luffing type tower cranes were optimally selected and located at the center core of the tower.

Tower Crane Types and Location.

Tower Main Hoist The figure shows the location of the main hoists and the hoist specifications. The hoists were installed in three different phases following the construction sequence of the tower. Additional Jump hoists were installed in accordance with the specifications shown in figure

Concrete Pumping Equipment While the horizontal concrete pump simulation test was very successful and indicative that re-pumping was not required, pumping the concrete vertically and under different environmental conditions could potentially present unexpected complications. Therefore, a secondary pump at level 124 was in place in case of an emergency situation. Three major pumps were placed at the ground level as shown in Figure. Pumping line 1 situated at the center core, with pumping lines 2, 3 and 4 at the south, west, and east wings of the core. An additional pumping line 5 was located at the center core area for emergency use. At of the time of writing this paper, the secondary pump has not been used and most of the concrete has been pumped directly to the highest concrete elevation, that in excess of 585m.

Tower Pump Equipment and Pipe Lines

Spire Erection and Pinnacle Assembly and Lifting Method.At Level 156, the reinforced concrete core wall will reach its highest point and serves as the foundation for the spires structural steel works. The central pinnacle structure, which consists of 1200mm-2100mm diameter structural steel pipe, varies in thickness from 60mm at the lowest level to 30mm at the top. The structural steel works above level 156 consists of the spire structure surrounding the central spine pinnacle structure, and provides the basis for its lateral support and stability. The spire structural system consists of an exterior diagonal braced frame system to provide for the lateral stability system. The erection of the spire and the pinnacle starts from level 156, and the erection of the spire was done in traditional steel construction method. However, the pinnacle pipe sections are stacked from level 156 and lifted to the final position from within the spire as shown in Figure.

Spire & Pinnacle Erection and the Pinnacle Lift-up method The lift of the pinnacle will occur in three steps. After each lifting step, the cladding on the pinnacle will be completely installed. The sequence of the pinnacle installation is shown in Figure below and as follows: Erection of the spire structure Installation of the support beam Installation of the lifting block and assemblies Installation of the lifting equipment and assemblies Lifting the pinnacle in a three step process Installing cladding after each lift Completing lift of the pinnacle and all connection connections (gravity and lateral) Completion of the cladding installation

Fire ResistanceBurj Dubai has built in fire protection as its concrete back bone is naturally fire resistant but how will people go out in an emergency? The answer they dont The Burj Dubai contains 9 special rooms build throw layers of reinforced concrete and fire proof sheeting The walls of these rooms will stand the heat of a fire for 2 hours Each room has special supply of air pumped throw fire resistant pipes, sealed fire proofed doors stop smoke from leaking in There is 1 of these rooms in about every 30 floors How they prevent the smoke from blocking the access route to the rooms? Early warning system: Fire activate a smoke detector Heat sensor Water sprinklers Network of high power fans kick in Fans force new clean cool air throw fire resistant ducts into the building The fresh air pushes the smoke out of the stair way keeping the evacuation route clear.

Cladding30000 glass panels of high quality European glass enough to cover 17 football fields, The glass is thicker at the top to resist the high wind. Its designed to let the maximum light in and to keep heat out. Tests on Cladding Test 1 : Air infiltration test To measure how much air gets in through the joints Test 2 : static water test Water is spread evenly for 15 minutes from nozles attached to the glass Transducers measures how much water gets in The data is transferred to computer for analysis Test 3 : Dynamic water Test Its a simulation for a desert Storm The wind is Generated by a giant Fan and its Spread water against the glass for 15 minutes Test 4 : Earthquake Test Earthquake Simulation which move the mock-up floor of curtain walls 10 mm in two directions With this test the know that curtain wall wont break

Faade MaintenanceThe tower's primary window washing and facade maintenance system consists of three permanently-installed, track-mounted, telescopic building maintenance machines located in internal "garage" positions on uppermost levels. it will take 36 workers three to four months to clean the entire exterior faade.

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