coupled shear wall

[sag04]

Good day to every one
My designer designed a 31 storey tower with Two core shear walls are interconnected by a syastem of slab ( span 2 meter). Slab system Flat slab. Bottom and top bars of slab 25mm dia anchored into shear for a length of 2 meter both ends top and bottom. Contractor questioning this anchorage length becos of parctical difficulty at site.He has to cast 2 meter height of shear wall along with slab.please comment

 

[dik]

If I understand you properly the vertical wall reinforcing is in conjunction with the slab reinforcing is causing the contractor problems?

I've often terminated the wall at the U/S of the slab and had vertical wall reinforcing extending above. The slab reinforcing can be dowelled into the slab to develop it and the wall reinforcing can be used to 'clamp' the slab.

Am I understanding the problem?

Dik

 

[sag04]

Thanks DIK
The slab top reinforcing dowelled down in to the wall for a length of 2 meter down & slab bottom rebars bended up in to the wall for a height of 2meter of shear wall. So you have to terminate the shear wall at 2 meter down from U/S of slab and cast this length along with slab. This is causing problem to contractor. He is questioning this development ( anchorage) length of rebars pointing the Table 3.27 BS 8110 Ultimate anchorage bond lengths as multiples of bar size. ( for M40 concrete – 35 Dia).
THanks

 

[csd72]

Sag04,

I am not sure I fully understand, but I will give it a go.

Would it solve the problem if you used a mechancal screw splice at the change in pour (try a lenton coupler, I think they supply them in the UK). This can be cast up against the formwork so that when the form is stripped you have a threaded hole to screw the remainder of the bar in.

This will develop the full strength of the bar without disrupting the por sequence.

3 problems to look out for though:
1. if the new bar to be screwed in has a cog, then this may not be able to be screwed in due to adjacent formwork, reo, e.t.c.
2. The bars going into the coupler need to be prethreaded for the particular coupler that you are using.
3. You need to check the british standards for requirements regarding seismic ductility, coupler extension e.t.c. to check that there are no restrictions on the use of these at this location.