Have you seen this? Malta Tower. 12

[MIStructE_IRE]

This is an amazing structure no doubt.

I’m not sure I’d have the cojones for it!!

Malta seems to be relatively low in terms of seismic activity and I guess a very stiff central core would take care of any torsion etc.. But still.. I think I’ve realised the limits of my engineering bravery!

In terms of redundancy... I’m guessing that steel ‘truss’ can span two bays if you lose one of the raking struts at the lower transfer level. If you lose a truss diagonal however I’m not sure what happens. Would love to hear others thoughts on progressive collapse.

 

[MIStructE_IRE]

Why would the circled columns be bigger than the one below it? This seems to be the way it was done in the photos also.

 

[Agent666]

Why would the circled columns be bigger than the one below it? This seems to be the way it was done in the photos also.

Graduate:"the model said so, model does not lie".....

 

[Tomfh]

Far out. I couldn’t handle designing something like that. The little “you missed something” voice would drive me insane.

 

[Trenno]

I've seen the whole bigger column on top of smaller column thing done for architectural purposes.

Those embed plates at the transfer levels must be wild.

 

[goutam_freelance]

I think they need to offer a discount if they need to sell it or put it on rent.

Engineers, think what we have done to the environment !

https://www.linkedin.com/in/goutam-das-59743b30/

 

[jk2017]

Why would the circled columns be bigger than the one below it? This seems to be the way it was done in the photos also.

Not sure, but in one of the photos on the engineer's site it looks like they're embedding a steel post inside the concrete column immediately above the steel truss level, so the thickness may be lower than that above...I'm not convinced, but just an idea!

 

[kostast88]

The corner columns appear to have a steel column embedded inside them, right above (and below) the steel truss.

Right on top of the steel column there is a larger number of anchors/dowels than the intermediate wall/column elements ([highlight #EF2929]red[/highlight]). That is not the case at the bottom.

That brings us to the the thicker column elements, where these anchors are embedded. A simple explanation would be: they needed more concrete area to prevent concrete failure at the connection when subject to lateral forces/moments. There's a lot of rebar in there but the force must pass on to the truss (compression) and you need as much concrete as possible.

Another explanation is that there is more compression going on and the thicker section is required. However with the steel column embedded inside, there is no need for a bigger section. The steel column works in a composite way with the RC column.

My only issue with the whole philosophy would be the bottle shape bent rebar in the columns, which would require considerable anchorage lengths. Perhaps this is what they are doing in the 2-storey thicker columns. They provide a lot of space for anchorage and carry downwards only the necessary reinforcement, relying on the embedded steel sections. That would be quite smart and economic to do.