bhiggins
Structural
- Oct 15, 2016
- 152
Hey eng-tips!
I have an old CMU/brick structure 150'x50' (low seismic area). This is a tenant finish out where the client wants to remove a center CMU wall and place additional openings at the existing facade. There are a number of issues that I wanted an opinion of:
There is a center CMU wall that the client wants to remove completely to open the space up. Based on the building geometry and layout it clearly looks like a bracing wall, but at my site visit there does not seem to be any connection to the roof diaphragm, it is only butted against the brick at the ends and possibly tied into the center column. The CMU wall is a different material than the original brick which makes me believe the wall was added after the initial construction, but there is no way of knowing for sure. This appears to be a 3-sided diaphragm situation because the front facade is completely open and most likely wood-framed.
I will most likely suggest to leave 10'-15' wall segments on each end, but this doesn't solve the connection to roof diaphragm issue. The ceiling joists are 12" bar joists so I'd prefer if there was a beam as a drag strut instead of a joist but that seems like too much work and cost to swap out a joist for beam. Is there a possible way to retrofit the bar joist to act as a drag strut? I'm wondering if anyone had a different opinion on how to proceed.
Another issue- I am not familiar with this type of roof deck. It seems to be made out of flat panels around 4' wide. It seems to be really dense when I poke it with my measuring tape, possibly a precast concrete material (I didn't have a ladder). Is anyone familiar with this roof deck material? I'm wondering whether to model the diaphragm as more flexible or more rigid.
I've attached some photos of the center CMU wall and layout of the building. Thanks for reading.
I have an old CMU/brick structure 150'x50' (low seismic area). This is a tenant finish out where the client wants to remove a center CMU wall and place additional openings at the existing facade. There are a number of issues that I wanted an opinion of:
There is a center CMU wall that the client wants to remove completely to open the space up. Based on the building geometry and layout it clearly looks like a bracing wall, but at my site visit there does not seem to be any connection to the roof diaphragm, it is only butted against the brick at the ends and possibly tied into the center column. The CMU wall is a different material than the original brick which makes me believe the wall was added after the initial construction, but there is no way of knowing for sure. This appears to be a 3-sided diaphragm situation because the front facade is completely open and most likely wood-framed.
I will most likely suggest to leave 10'-15' wall segments on each end, but this doesn't solve the connection to roof diaphragm issue. The ceiling joists are 12" bar joists so I'd prefer if there was a beam as a drag strut instead of a joist but that seems like too much work and cost to swap out a joist for beam. Is there a possible way to retrofit the bar joist to act as a drag strut? I'm wondering if anyone had a different opinion on how to proceed.
Another issue- I am not familiar with this type of roof deck. It seems to be made out of flat panels around 4' wide. It seems to be really dense when I poke it with my measuring tape, possibly a precast concrete material (I didn't have a ladder). Is anyone familiar with this roof deck material? I'm wondering whether to model the diaphragm as more flexible or more rigid.
I've attached some photos of the center CMU wall and layout of the building. Thanks for reading.
