shear wall - frame interaction: large link beam forces
shear wall - frame interaction: large link beam forces
(OP)
Hello:
Can anyone give advice on my problem below?
Under lateral seismic, I am developing very large shears and moments in short beams (about 1 meter length) connecting shearwalls and the framing system. My lateral force system is only shearwalls, so the framing system is designed for gravity loads. That is, the framing system has to be able to deform under the seismic load without yielding. The current connection I have between the beam and the wall is a moment connection.
My concerns are below:
1. Is the moment connection right, or do I use moment releases?
2. To me, the large forces on these beams makes it seem like a "coupled wall" type of response.
3. If it is ok to model these beams as hinged, how are they detailed in that way? Also, is this detailing better done at both sides of the beam, or only on the side of the wall?
Thanks






RE: shear wall - frame interaction: large link beam forces
RE: shear wall - frame interaction: large link beam forces
RE: shear wall - frame interaction: large link beam forces
What about wind, do you need to have these shears walls acting as coupled shear walls under wind loading?
1. I think your moment would be correct.
2. I agree if you are taking high moment and shears from one shear wall to another it is a coupled response.
1b & 3. I don't want to answer 1b and 3 since i live in a world where we don't have high requirements on detailing for seismic events. It would be helpful to know where you are, the codes that you need to comply with ect. Then we may be of assistance.
Arguing with an engineer is like wrestling with a pig in mud. After a while you realize that them like it
RE: shear wall - frame interaction: large link beam forces
1. Thanks for your response. No, wind is not an issue. This is a 4-storey building in a medium-to-high seismic area.
2. Design is with Eurocode 8, which requires that all secondary members (not primary resisting elements) must be able to safely carry gravity loads under seismic load. Actually, all major seismic codes require this.
3. Please note that I did not mean a beam connecting two shear walls to form a coupled shear wall. What I meant is the beam that connects the shear wall and the rest of the concrete moment framing system.
Hope my problem is clearer.
RE: shear wall - frame interaction: large link beam forces
RE: shear wall - frame interaction: large link beam forces
Arguing with an engineer is like wrestling with a pig in mud. After a while you realize that them like it
RE: shear wall - frame interaction: large link beam forces
RE: shear wall - frame interaction: large link beam forces
RE: shear wall - frame interaction: large link beam forces
Also, rotational ductility diminishes with the structural depth of the standing member. This is easily understood: atop a steel flange or top rebar, for whatever limit strain of the ductile steel behaviour (upper strain of the yield plateau), the rotated angle at the joint is inversely proportional to the depth of the member or slab. Hence by just using the smaller depth compatible with the wanted structural behaviour, you are enhancing the rotational ductility. Again, this may have more value for steel structures and connections that are required to undergo at full strength the complete earthquake rotational excursions, but for concrete structures it is seen that allowing for such extreme ductility is inconsistent with the convenient design and behaviour of the structures and the contrary path of limiting the lateral excursion under earthquake force is taken. This way we design for concrete structures having higher response to earthquake, more stiff and showing less lateral displacement, requiring less ductility at connections, and, out of the lesser displacement allowed, more likely to sustain with the required integrity the earthquake event. So if you have actually designed stiff shearwalls, your earthquake excursion must be controlled and likely you will be able to design the smaller depth members you can that, through confining action of close closed stirrups or hoops, may pass efficiently your forces from your floor to the shearwall.