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The Bird's Nest, officially known as the National Stadium, caused quite a stir when it was unveiled in 2008. It was both hated and loved, but for architects, engineers and construction workers around the world, it inspired another emotion – awe. This project was enormously detailed, and could not have been achieved in as short a time, with as low costs and little room for error, had it not been for building information modeling technology. We look at how BIM made it possible for the structural engineers, steel detailers and construction team to put the Bird's Nest together in time for the Olympics.
Vital statistics for the Bird's Nest
* 332m long, 297m wide, 69m high
* Site area: 204,278 sq. m.
* Structure contains 36km of unwrapped steel length
* Largest steel truss spans 343m
The Bird's Nest Challenges
To some people it might look like a tangled ball of discarded wire. To the people that built it, there was much more involved than finding leftovers. Some of the issues that building information modelling helped solve quickly for the structural engineers and steel detailers included:
* Weight minimization
* Reducing construction costs
* The saddle-shaped, ellipse based roof
* An outward incline of the external surface of 13 degrees from vertical
* As you see in the vital statistics, the largest steel beam is 343m long, and the structure used 36km of unwrapped steel length.
How BIM helped
One of the most difficult parts of the building for the structural engineers was the roof. The enormous weight of the steel showed in their calculations that a full steel roof was simply not possible. It took over a year for Chinese steel detailers and fabricators (two firms – Huning and Jinggong) to produce symmetrical 3D views of the connections and members. Good building information modeling software has mirroring functions, which took a lot of the legwork out of this project. The connections are almost impossible to visualize mentally – but this is not required, with the advent of 3D modeling for construction.
Another of the Bird's Nest's major features that would not have been possible without BIM is the cushion system of the inner spaces of the building's facade. It was not only support that had to be considered in the design; the structural engineers used building information modeling to predict how the structure would react to wind, sunlight and weather. The solution ended up being to fill some spaces strategically with ETFE, a translucent material used to construct the ‘Bubble Building' also in the Chinese Olympic Park.
Obviously, the appearance of the building is it's most important factor. It is different, unusual and culturally significant; as well it is ‘anti-technocratic' (according to the designers). This would not have been possible without the aid of building information modelling.
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Source by Paul P McLeod
