Where does a Moment Frame ends and a Shear Wall begins ?
Where does a Moment Frame ends and a Shear Wall begins ?
(OP)
Let me start with a story - My client has recently bought a hotel building. The building was bought along with an empty plot of land behind it. The previous owner intended to expand the hotel on the plot of land and has already paid for the architectural & structural design to commence. The expansion was planned to be a U-shaped 4 story reinforced concrete building. My client is planning on constructing the building expansion based on the issued drawings. Please keep in mind that this project in a relatively high seismic zone - Ss of 1g and S1 of 0.4g.
I'm tasked with reviewing the structural drawing along with a senior engineer. The senior engineer brought it to my attention that the "columns" are inappropriately sized for seismic application. The "columns" are T-shaped and L-shaped with a thickness of 140mm and "legs" ranging from 300mm to 700mm. This is based on ACI 318's provision Chapter 21.6.1.1 for Special Moment Frame Systems. The only thing is - I'm not sure if this is considered a "Special Moment Frame System". There are a couple of shear walls in the building for the elevator shafts. I couldn't find any reference in ACI to the minimum thickness of a Shear Wall and I'm wondering if 140mm is thick enough. From a constructibility standpoint, there is very little room for the rebars at 140mm :
10mm(Transverse Reinforcing) x 2 = 20mm
19mm(longitudinal Reinforcing) x 2 = 38mm
20mm (Concrete Cover) x 2 = 40mm
There is a 40mm space in between the longitudinal reinforcing. When there's a column splice, the whole thing is going to be full of rebar and it doesn't really make sense.
Is there a minimum thickness on shear wall? Can the "columns" be considered a shear wall or are they "columns" ?
I'm tasked with reviewing the structural drawing along with a senior engineer. The senior engineer brought it to my attention that the "columns" are inappropriately sized for seismic application. The "columns" are T-shaped and L-shaped with a thickness of 140mm and "legs" ranging from 300mm to 700mm. This is based on ACI 318's provision Chapter 21.6.1.1 for Special Moment Frame Systems. The only thing is - I'm not sure if this is considered a "Special Moment Frame System". There are a couple of shear walls in the building for the elevator shafts. I couldn't find any reference in ACI to the minimum thickness of a Shear Wall and I'm wondering if 140mm is thick enough. From a constructibility standpoint, there is very little room for the rebars at 140mm :
10mm(Transverse Reinforcing) x 2 = 20mm
19mm(longitudinal Reinforcing) x 2 = 38mm
20mm (Concrete Cover) x 2 = 40mm
There is a 40mm space in between the longitudinal reinforcing. When there's a column splice, the whole thing is going to be full of rebar and it doesn't really make sense.
Is there a minimum thickness on shear wall? Can the "columns" be considered a shear wall or are they "columns" ?






RE: Where does a Moment Frame ends and a Shear Wall begins ?
RE: Where does a Moment Frame ends and a Shear Wall begins ?
Sounds a bit like some of the tilt-up I've worked on. Is this a precast / tilt-wall / tilt-slab extension?
RE: Where does a Moment Frame ends and a Shear Wall begins ?
150mm thick wall
10mm x2 transverse reinforcement
13mm x2 longitudinal reinforcement
20mm x2 cover
10mm+13mm+20mm )x2 = 96mm
We have 150 - 96 = 54mm to play with, which isn't much.
We're trying to get the structural engineer to change it to a rectangular column instead of a shear wall, but I believe there will be some problems in the ETABS model due to the seismic lateral load if we do this. For some reason, my senior engineer doesn't think that a single layer of rebar in the shear wall will work. Is there a minimum on a shear wall's thickness ? These are two designs from two different projects from two different structural engineering consulting companies in Indonesia. I'm beginning to doubt myself
RE: Where does a Moment Frame ends and a Shear Wall begins ?
RE: Where does a Moment Frame ends and a Shear Wall begins ?
RE: Where does a Moment Frame ends and a Shear Wall begins ?
RE: Where does a Moment Frame ends and a Shear Wall begins ?