Thickness of seismic RC Wall 1

[ITsSB]

I have a wall in a seismic area that is part of a building and should satisfy the following eurocode provision.

The wall supports a stair and the beginning and end of the stair is connected to the RC frame system and floor diaphragm.

The wall height is 14m (4 floors each 3.5m center to center height). I know it depends on the relative stiffness of the stair, stiffness at the start and end connection to the beam but,...do you consider this wall braced? Originally, I gave it a thickness of 14000/20 = 700mm, which I think is huge.

 

[HTURKAK]

The wall height is 14m (4 floors each 3.5m center to center height). I know it depends on the relative stiffness of the stair, stiffness at the start and end connection to the beam but,...do you consider this wall braced? Originally, I gave it a thickness of 14000/20 = 700mm, which I think is huge.

The wall connected to the floors from one side and braced with landings and stair flights from other side . I do not know if the thick 40 cm architectural requirement but 40 cm more than enough . Structurally , i would choose 20 cm.

 

[ITsSB]

The wall connected to the floors from one side and braced with landings and stair flights from other side . I do not know if the thick 40 cm architectural requirement but 40 cm more than enough . Structurally , i would choose 20 cm.

thank you for your response. 40cm is AR limit but in order to limit span/20 requirement, I was forced to give it 70cm due to code limit. (minimum thickness of wall for medium ductility class in eurocode is max of 0.15m or span/20). If I'm not expected to satisfy that and provide low ductility 20 or 25cm is enough. Since there is no lateral support/connection of the wall to the rest of the building in left and right direction, I couldn't convince myself at the time, let alone convince the people that review and approve my drawings. I hope other people comment on it too.

 

[HTURKAK]

Since there is no lateral support/connection of the wall to the rest of the building in left and right direction, I couldn't convince myself at the time, let alone convince the people that review and approve my drawings. I hope other people comment on it too.

Can you post the structural plan ? Apparently the staircase is located outside of the structure . Is this a fire escape stair ? Are the flights cast in place ?

 

[ITsSB]

Can you post the structural plan ? Apparently the staircase is located outside of the structure . Is this a fire escape stair ? Are the flights cast in place ?

The same thing for the other one too but, that one is on the top right in red. I'm not sure about the fire escape part (I have to ask but looks like it is) regardless the architect doesn't want steel staircase and it has to be cast in situ concrete.

 

[HTURKAK]

The picture attached is architectural plan and the framing is not predictable. However , assuming the frames are moment frames composed of column +drop beams , and considering the no of storey (4) , my approach would be ,

- I would try to consider the subject two walls as secondary’ seismic elements with checking if the contribution of secondary seismic elements to the lateral stiffness should be not more than 15% of the primary seismic elements system ,
- If this does not work , i would calculate the effective height . ( In this case , one end connected to the storey and the other end braced with landings and flights ) The effective height could be predicted as though the wall were a column subjected to bending at right angles to the plane of the wall.
( EC-2 ,5.8.3.2 Slenderness and effective length of isolated members)

I hope my opinion makes sense.