The Burj (Dubai) signifies one of the marvels of the present civilization. Considering the fact that it towered 800m above the ground level, it set a new record to be shattered. Looking at it from a layman’s eye, it seems an impossible engineering fit, which until its realization might have seemed same to the tutored eyes (the eyes of the engineers).
Presently, looking at it through our eyes as engineers, we cannot afford not to marvel at own accomplishment at our own time. This is a structure that depending on the weather condition, may seem to vanish into the high havens. The builders of the tower of Babel would have been awed by the ingenuity that went into its realization.
Coming back home, let’s take a rough and preliminary look at this structure. It is a tall slender structure as such is very susceptible to lateral or horizontal load that could be induced by such agent as wind or seismic wave etc. It is composed mainly of the occupiable spaces (the floors) and the towers (spaces used principally for the support of plants/equipment). The slabs and the beams do not form the most critical structural elements. The design of typical sets of slab/beam arrangement could serve any and/or all the floors of the building. But for each floor, there exists the possibility of designing individual columns. This is due to the fact that any successive floor above each plan adds to the load to be carried by the underlying or the supporting column. If we assume that up the height of 800m of the structure is composed of the occupiable floors and that the average floor height is 3m, then we have about 267 floors above the ground level.
Let the live load be 3KN/M^2
Let the dead load from the slab/beam (represent by 200mm thick reinforced concrete, though the floor is most likely to be of steel deck with light weight concrete as such will weigh less than that assumed, but putting into consideration the actual weight of the floor, the weight of the supporting beams, the partitioning, the fittings etc) be 25 x 0.2 + 1 = 6 KN/M^2.
Assuming that the lifts, shafts and towers (above the 800m level are supported by the shear walls or the shafts that housed the lifts but served principally as the horizontal force resisting structure)
Assume that the columns are arranged in a network of 4.5m x4.5m. Then floor area supported by a typical column = 4.5m x4.5m = 20.3m^2
At the ultimate limit state, the design load for the column per each floor supported = 20.3 (gG x 6 + gQ x 3). If the load factor for the dead load gG = 1.3 and that for the live load gQ = 1.5 (I am using the Italian code), then the ultimate design load (vertical load only) = 20.3 (1.3 x 6 + 1.5 x 3) = 20.3 (7.8 + 4.5) = 249.1KN.
This implies that at the foundation level, a typical column carries a load = 249.1 x 267 = 66426.67KN. This did not include the self weight of the column. Assuming 5% of the load carried as the weight of a line of the column, then a typical column carries 1.05 x 66426.67 = 69748KN (including its own weight).
If we use a typical steel section that has an ultimate capacity of 460N/mm^2, then the cross-sectional area of steel required to bear this load = 69748 x 10^6/ (0.85 x 460) = 1.78 x 10^8mm^2
TO BE CONTINUED
Regards
Teddy
(01-04-2010, 10:52 AM)chigozie Wrote: [ -> ]The world’s tallest building, the BURJ (Dubai) is to be inaugurated today (the 4th of January 2010). It is estimated to be of more than 800m tall!!. Could we discuss the conception, analysis/design and the realisation of the project (the construction), if possible model it with the noted (or the popular) soft wares as to compare their similarities, divergence and also to propose possible discrepancy in the results?
Regards
Teddy
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