China Central Television Headquarters (CCTV) Tower – Structural Perspective
This building might be a little familiar if you’ve watched the karate kid film. This building is shown along with the stadiums that were constructed in china for the Olympics. It is a recent striking addition to the Beijing skyline. It became a prominent member of Beijing’s new skyline.
![[IMG]](proxy.php?image=http%3A%2F%2Fwww.crazyengineers.com%2Fwp-content%2Fuploads%2F2011%2F03%2F2.png&hash=34d6c0447e24a2ef170b5eed130bea9a)
In the #-Link-Snipped-# I’ve discussed the#-Link-Snipped-#. Now lets see how exactly this wonder was constructed.
The design was so complex not only because of it’s shape but also because of the irregular stress distribution and the inclinations and slopes. The design process for this structure is made even challenging because it has no other such structures to look for examples and directions for design. Even the computational tools were not sophisticated enough to support this massive engineering. This project is 50% Chinese and 50% international.
![[IMG]](proxy.php?image=http%3A%2F%2Fwww.crazyengineers.com%2Fwp-content%2Fuploads%2F2011%2F03%2F3.png&hash=681743def1a998017740405b55b76440)
The above picture would give an idea about the structural details of the buildings. Do note that one tower is taller than the other so there is a slope in the overhang from the taller tower to the smaller one.
Any skyscraper’s general principle is to have a strong core which could itself support the whole building. But here the weight of the overhangs over the two towers tries to make the two towers bend in the direction of the overhangs. So a net slope of 10<sup>0</sup> has to be accommodated here. They first thought of an option of having a sloping core but it was immediately rejected because it would make even the lifts move diagonally which would cause a lot of discomfort to the users. So the core starts at one corner at the bottom and as it reaches the uppermost floor it would have reached the other corner.
Construction details:
The building was built as two separate towers that were later combined once both towers were fully supported. The real challenge for these engineers was connecting the two towers and the construction of the cantilevers. The reason is that the building of the two cantilevers continued the two towers had a gradual increase in load causing it to bend and sway. So the engineers considered the options at hand. One was they could use a jack to lift whole built-up sections or they could make the scaffoldings support the overhang in one corner or the can proceed the cantilever way. The engineers chose the last option. It was a big challenge when they had to tie the two cantilevers together. One early morning before the steel diagrids could heat up and expand this job was finished.
Now coming to the structural members, lets see what type of foundation, beams, columns the building had.
There are some places which are heavy loaded zones. These places were made strong by doubling the number of beams. In the light loaded zones they decided to half the number of beams.
The building has pile foundations beneath the concrete raft. The raft was 7m thick and extended to an area larger that the building to provide more support. The rafts were thicker under the towers than in the rest areas. The piles are 1.2m in diameter and 52 m long.
The second picture shows the different columns in the building. The internal columns were the composite ones which had concrete encased structural steel where there was an advantage of an additional 3-4 hours fire protection and an additional 30% compressive strength. The columns here have varying heights and end as they reach the façade.
The testing:
Some 3-D models were made and tested for the loadings. They were tested to see if the buildings could withstand earthquake forces.
They made a 1:20 model. It was erected in the building’s car parking site and tested using the shake table apparatus. It had withstood the test. The Chinese codes of practice didn’t prescribe seismic design. So this performance based test was carried out. Their objectives were that the building should have no structural damage for the level one earthquake, for a level two earthquake it must have only repairable structural damage, and finally for the third level earthquake it can have structural damage but the building must not collapse.
But to make sure that all could believe that the structure was a safe one, the engineer showed it’s high degree of redundancy. They proved that even if three columns were damaged the design was such that the loads would redistribute by itself.
![[IMG]](proxy.php?image=http%3A%2F%2Fwww.crazyengineers.com%2Fwp-content%2Fuploads%2F2011%2F03%2F4.png&hash=9191e1663c90009efb5b318d0a95d821)
The diagrids were tested using the available software and the result showed that only the diagonal members of the diagrids were taking the load. The following picture is a computer image showing that only the diagonal members take the stress.(shown in green color)
The building was completed in 2008. Thus this marvel was made a reality by the ingenious architects and engineers!
Image Credits: Oma | #-Link-Snipped-# | #-Link-Snipped-#
In the #-Link-Snipped-# I’ve discussed the#-Link-Snipped-#. Now lets see how exactly this wonder was constructed.The design was so complex not only because of it’s shape but also because of the irregular stress distribution and the inclinations and slopes. The design process for this structure is made even challenging because it has no other such structures to look for examples and directions for design. Even the computational tools were not sophisticated enough to support this massive engineering. This project is 50% Chinese and 50% international.
The above picture would give an idea about the structural details of the buildings. Do note that one tower is taller than the other so there is a slope in the overhang from the taller tower to the smaller one.
Any skyscraper’s general principle is to have a strong core which could itself support the whole building. But here the weight of the overhangs over the two towers tries to make the two towers bend in the direction of the overhangs. So a net slope of 10<sup>0</sup> has to be accommodated here. They first thought of an option of having a sloping core but it was immediately rejected because it would make even the lifts move diagonally which would cause a lot of discomfort to the users. So the core starts at one corner at the bottom and as it reaches the uppermost floor it would have reached the other corner.
Construction details:
The building was built as two separate towers that were later combined once both towers were fully supported. The real challenge for these engineers was connecting the two towers and the construction of the cantilevers. The reason is that the building of the two cantilevers continued the two towers had a gradual increase in load causing it to bend and sway. So the engineers considered the options at hand. One was they could use a jack to lift whole built-up sections or they could make the scaffoldings support the overhang in one corner or the can proceed the cantilever way. The engineers chose the last option. It was a big challenge when they had to tie the two cantilevers together. One early morning before the steel diagrids could heat up and expand this job was finished.
Now coming to the structural members, lets see what type of foundation, beams, columns the building had.
There are some places which are heavy loaded zones. These places were made strong by doubling the number of beams. In the light loaded zones they decided to half the number of beams.
The building has pile foundations beneath the concrete raft. The raft was 7m thick and extended to an area larger that the building to provide more support. The rafts were thicker under the towers than in the rest areas. The piles are 1.2m in diameter and 52 m long.
The second picture shows the different columns in the building. The internal columns were the composite ones which had concrete encased structural steel where there was an advantage of an additional 3-4 hours fire protection and an additional 30% compressive strength. The columns here have varying heights and end as they reach the façade.
The testing:
Some 3-D models were made and tested for the loadings. They were tested to see if the buildings could withstand earthquake forces.
They made a 1:20 model. It was erected in the building’s car parking site and tested using the shake table apparatus. It had withstood the test. The Chinese codes of practice didn’t prescribe seismic design. So this performance based test was carried out. Their objectives were that the building should have no structural damage for the level one earthquake, for a level two earthquake it must have only repairable structural damage, and finally for the third level earthquake it can have structural damage but the building must not collapse.
But to make sure that all could believe that the structure was a safe one, the engineer showed it’s high degree of redundancy. They proved that even if three columns were damaged the design was such that the loads would redistribute by itself.
The diagrids were tested using the available software and the result showed that only the diagonal members of the diagrids were taking the load. The following picture is a computer image showing that only the diagonal members take the stress.(shown in green color)The building was completed in 2008. Thus this marvel was made a reality by the ingenious architects and engineers!
Image Credits: Oma | #-Link-Snipped-# | #-Link-Snipped-#
0