ABI Conference 2008- Burj Dubai Tower

The case study on the Burj Dubai towers focuses on the increasing height of buildings around the world, and the competition to be the tallest. Along with this it discusses the problem involved in constructing buildings of such a height, for example the difficulty to vertically pump the thousands of cubic metres of concrete that is required. The Burj Dubai now holds the record for pumping concrete, upto 588metres. The completion height of the building is unknown, but is expected to be above 800 metres, with the higher portion made from a steel frame structure.

Burj Dubai Tower

The finished height of the tower is predicted to be between 800-950 metres, it is been keep secret in attempts to beat other current skyscraper under construction.
The Burj Dubai Tower is due for completion by June 30th 2009.
The structural steel core of the building.
An Giorgio Armani Hotel will occupy the lower 37 fllors. Floors 45 through 108 will have 700 private apartments, while corporate offices and suites will fill most of the remaining fllors. Expected to be a total of 160-189 floors.

Source: www.burjdubaiskyscraper.com

Panel Bracing

It appears that the panels for this building will be load bearing, whereby the rafter will be bolted into the actual panel spaning across to the grey composite columns.

These three panels are not yet tied into the main structure, it is at this stage where stability of the erected panels is critical and as such they must be temporailty braced often using ferrules. The main brace will be bolted into the panel and again into the concrete slab or pier at an acute angle on the ground.
The braces are evenly spaced to ensure uniformity in load bearing, they are usually only designed to take wind loads.

Pre-cast concrete panel construction

This is a commercial builing under construction using pre-cast concrete panels. It is located on Princess Highway (Dandenong Road) in Carnegie. Accoding to the real estate sign above it is going to be a retail showroom, spanning two levels.

As you can see there is very little space to cast the panels onsite, i would assume that they have been made in a specialised factory, delivered to site via truck and lifted into position by a crane.

There are multiple concrete panels inplace to form the back wall, as you can see they are braced together at the edges using plates to support the panels prior to their incorporation into the final structure.

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Joints & Connections

Here is a UB rafter at the knee joint, it also contains a cut UB haunch which are usually required for spans over 20 metres. This unified beam is supported by fly bracing to the 'C' purlins and it is also embedded in the brick pillar.
A standard four bolt cleat is used to connect the rafter and the purlins, in this instance it is replacing a knee joint and the haunch that is usually involved. In fact the majority of connections between the purlins and rafters were done using this technique.
This rigid connection using a cleat plate has allowed for extra bracing in two directions, with one member spanning between the central rafter and the exterior walls purlin and the other cross bracing to a 'c' purlin.

Load bearing brick pillars

The method of transferring the dead and wind loads from the roof downwards is done through the use of brick pillars, whereby the purlins and rafters are built into the brickwork where possible.
Here are two structural members braced together using cleats and two bolts, the rafter is then fixed into the solid brick wall.
This is an example of why portal frames with steel columns are now used, as you can see the purlins is just sitting on top of the brick ledge while the rafter appears to barely restrained by the degraded brickwork.
An extended view of one of the many brick pillars that support the beams and transfer all the loads into the ground.

1970's Portal Frame

This is a 1970's warehouse situated in Clayton, Melbourne. It is now home to a carpet warehouse and Floorworld retail showroom. An immediate difference to that of the design from Bunnings is the extensive use of bricks and windows.
As is evident by the state of the insultation this warehouse is aging. But the same principle still apply, with a long spanning rafters and purlins allowing for uninterupted access that a forklift requires. What is interesting about this design is the long span cross bracing between rafter members, but this is not consistent throughout the warehouse.
The warehouse bares a low pitching roof only spanning approximately 20 metres.