Multi-Family Wood Frame Construction 1

[andrewu4]

I have (3) buildings, buildings 1 and 2 are (3)-stories over a concrete podium. Building 3 is 4 stories of wood. The issue is, the original designers at my company that did a lot of the lateral design had never designed any type of wood building, and have since left the company. I am the only engineer left and I have also never designed a wood building. On top of that, I am generally working on 10-20 other projects at a given time, putting in 60+ hour weeks and have very little time to devote to this project or learn wood design. We have been looking for another mid level engineer but they are hard to come by in the Northern Va/Baltimore MD area. The job has been on hold for years and I always assumed we would get a new hire by then. The project is suppose to go to permit in a couple weeks in order to avoid a code change to 2018 codes....

I am worried about the lack of attention given to the diaphragms. It appears a lot of effort was given to shear walls, but I could not find much in the calcs or drawings in regards to the diaphragm itself. Also, the original designer kept mixing and matching wood shear walls and masonry shear walls and steel moment frames. I am also concerned about he wood the masonry wall connections in regards to shrinkage. I am also worried about the concrete podiums working as a moment frames.

A couple things to keep in mind,
Almost all exterior walls have brick on them.
The full-height masonry walls are there because they are touching a property line/close to an ex building.

I realize this is a huge ask, and I am being placed in a horrible predicament, but any help would be greatly appreciated in regards to (collectors, drag strut, blocking/strap locations, hold downs, which walls should be shear walls and which ones shouldn't/general detailing). Or any general advice is greatly welcomed.

 

[andrewu4]

Building 3

 

[andrewu4]

Building 2

 

[skeletron]

Dude, I think you need to subcontract this out to someone in your area. Here's the reasoning:

1) You have identified that wood-frame is beyond your limits
2) The previous engineers who designed the drawings had never handled this type of structure
3) You have identified being pressed for time and focus
4) This is an online discussion forum, not a volunteer engineering service platform

Subcontracting this design out will have so many more benefits that even the brightest minds on this forum can't offer.

 

[phamENG]

Ouch. I'd love to help out (I'm down in Hampton Roads), but a 2 week turnaround? Even for just a review of a well put together set of drawings and calcs you'd be hard pressed to find somebody qualified who can fit it in in that time frame.

You need to spell out your concerns in detail and voice them to your supervisor. Some damage control needs to happen quickly with your client. You either release the drawings as is and hope all goes well (I'm not advocating this), or you tell them you won't make the deadline. And really. What changed in 2018 that they are worried about? I get that you have to update references, but there is really a substantive change that took place that will impact the design and cost of these buildings? I went through this on a wood framed podium building at the last code change...nothing in the design of the building changed at all. Could be different this time around, I'm not sure.

 

[kipfoot]

Some damage control needs to happen quickly with your client.

This was my first thought, too: It's better to tell them now that they're not getting a permit set in two weeks.

Even if you were going to run with the design as it is, it looks like there's a enough work that will take a couple weeks to fill in the gaps unless you're going to drop everything and grind on this the whole time. ("column capitals not shown at this time")

 

[andrewu4]

Let me try to give a little back story and clarify some points.
1. I knew this job would be coming back at some point for the last 9 months. I was not sure when. I begged upper management to get rid of this job when we had the chance (client did not pay for a couple years). I also begged to get an immediate hire for the last 9 months and have been met with any potential hires do not fit the bill. I also begged to sub it out. Since the job is out of money, they don’t even want me working on it, let alone subbing it. Last I heard I was to “make the best of a bad situation”.
2. Permit will be 85%. I will make sure it is either unsealed or has not for construction or not for bid on it. It will not be built as is. I also doubt it could ever get permit approval as is, and if it does, that’s pretty scary. There will be several months after this to make changes.
3. The push is to get it grand fathered into a permit using 2015 codes. I am not sure what the big deal is if we don’t get it. Structurally, wind speeds decrease and seismic will increase. There is a 4th building that a concrete automated parking garage that will be controlled by seismic. Seismic will have an effect on out of plane anchorage of the cmu walls on the first 3 buildings. I am assuming they know the other subs will ask for a change order as it probably effects the arch and MEP more. It is a green globes building.
4. The job was on hold for over a year. I have been too scared to work on it as the arch has still been moving walls, columns, floor to floor heights, unit layouts, etc. I also just got the weights of the equipment on the roof which is a big deal since a lot of walls don’t stack and until now I have had no idea what is suppose to be up there. I also have not had any time as I have been concentrating on many other projects. I talked to the engineer who designed the lateral system shortly after he left where he was with it, and he basically told me it was 100% done, other than some detailing and what to do with some cmu walls. This really does not seem to be the case.
5. I am not asking anyone to design anything or solicit free service or waste any substantial amount of time on this. I am at most asking someone qualified with this type of building to take a quick glance and see if what is shown on the drawings makes sense and is something that can be salvaged. An hour phone call or screen share on teams would tell me all I need to know.
6. I am mostly asking for professional advice in what to do with my employer. I need some type of leverage to either sub it out or delay the submission until I can get help. Or if my only way out is to leave, then I would like to know that is the general consensus of my group of peers. Or, if you think what is being asked of me is reasonable, then I will let my employer know the fault is with me.

 

[gte447f]

Yikes! This reminds me of all the things I do not miss about working for a manager in structural engineering consulting firm. In my opinion, this post belongs in the business practices forum or similar, to gather feedback on how to manage this project. Also maybe to gather feedback for the OP's employment conditions, with respect to relationship with and expectations from upper management, job responsibilities, resources, etc. It sounds like you are in a very tough spot, being leaned on heavily without adequate assistance, resources, time, or support. As for the technical aspects of the structural design and construction drawings, I think the scope of this request is entirely too broad and therefore inappropriate for this or any internet forum. I would urge the OP not to succumb to pressure to push this through prematurely or without adequate technical aptitude devoted to the design and drawings. Insist that you get the help that you need from your management team. Please note: none of my comments are intended as a critique of your competence as an engineer. You are simply in a bad spot. It sounds to me like it is your managers (who are probably engineers also?) who have botched this.

 

[milkshakelake]

I looked at these drawings for about 15 minutes. Bruh, it's going to take a lot, lot longer than that to review it and give worthwhile advice. From my quick review, it looks like these drawings have a lot of the basics down (and keep in mind that it's a very quick review, mostly jotting down thoughts):
-Shear wall schedule is laid out, there is nail spacing and holdowns specified (sheathing type, like APA-rated plywood or OSB, is missing but maybe I didn't see it).
-There is a typical shear wall detail with nailing patterns shown and anchors specified.
-Connection to CMU walls is there. Honestly don't recommend it due to shrinkage, but it works for lateral. Your collector is the rim joist, which is taking shear from the diaphragm using edge nail (probably should show the edge nailing directly on the detail) and conveying it to the CMU wall with bolts (probably should specify the type of bolt).
-There is lateral blocking or rim board where joists end, which act as collectors to the shear wall.
-From a quick glance, nail spacing looks ok, but keep in mind that it's an extremely quick glance.

Some things that need work:
-Detail 7 parapet detail doesn't make sense, you are interrupting a plate. That is impossible to construct.
-Detail 4 setback relieving angle needs to be connected to the structure.
-Virendeel frame needs more info about how things are attached to it and transfer shear.
-Quick look at footings looks like it's missing shear transfer, but maybe I missed it.
-It is not 100% clear how your collectors terminate. Since this is a flexible irregular diaphragm for all 3 buildings, there should be clear and easy to follow details about how they end/terminate
-Shear wall openings should be on plans

 

[XR250]

Andrew,

This is not your problem and why do you work 60+ hour weeks? You have already stated there is a shortage of SE's in your area. Should be easy to find another job if you decide to put your foot down.

 

[andrewu4]

My original manager and coworker that did the lateral design were engineers with 30 years experience each. They mismanaged it early by bowing to every request by this absurd architect and owner/developer. Currently, there is not one employee other than myself who has any structural engineering experience. My current manager is a Vice President who is a construction manager. The only people above me are VPs/Corporate. The last 9 months has been stressful to say the least.
I have no intention to send this out before it is ready. I already said I would refuse to seal it unless we either hired someone, subbed the whole thing out, or got a 3rd party review on it. The leverage in the situation is all mine.

 

[andrewu4]

I agree detail 7 does not make much sense and I’m going to switch it to normal platform framing with a kicker. If the arch refuses, then I’ll have to balloon frame it with a ledger like at the balcony. Good call on the other items too.
As for shear transfer at the footings, the issue is I am still not certain which, if any, cmu walls are shear walls. I am also not really decided on if the 2 concrete podium buildings should really be moment frames or if they should be cmu shear walls at the party walls and stair/elevators. I kind of need slab support at those areas anyways and it might be tricky to not end up accidentally making a shear wall. If any of the foundations with micro piles end up with shear, I would batter some piles.
I also questioned using the cmu walls for shear and was wondering peoples preference. All those cmu walls end up bounded by 3.5” studs to hide the cmu anyways. Seems like I could just add some plywood and make them shear walls.

 

[andrewu4]

I am not worried at all about finding a job. I get to work from home a lot and am basically in charge. I am getting an opportunity now that people with twice my experience don’t get. Also, if I find a way to weather the storm, this would obviously be the only multi family project we would ever end up with.

 

[milkshakelake]

I agree w/ other posts that somebody else should get involved, because there's a lot here to review and unpack. It looks okay on the surface but every time I look a little deeper, I find some important thing missing. Through no fault of your own, you could easily skip something that no amount of reading NDS code or textbooks will help with. With that disclaimer...

I would personally change all the CMU walls to wood shear walls. The reason is because of shrinkage incompatibility. There are NDS formulas to calculate how much wood will shrink. Your CMU won't shrink, and wood will, causing a slope in joists. There are ways to control shrinkage, like using kiln dried wood and covering the whole structure during rainfall, or with careful CMU detailing, which will never happen.

I didn't really look at the podium level since I assumed the question is about the wood. But if the only walls there are CMU, then yes, they are acting as shear walls. I wouldn't rely on the concrete columns + slab as moment frame since the punching shear will be gravity+lateral and your 12" slab might not be enough, not to mention seismic drift with deflection amplification. It's also questionable to use the CMU as shear or bearing walls, since that's not standard practice and your slab design would be different (i.e. pinned at those supports) but it's possible. However, I'd personally turn some of the CMU walls to concrete shear walls, thus ensuring quality control and rebar detailing w/ shop drawings, and make the CMU as non-bearing w/ a 1/2" or so (calculated from deflection) gap with an upside down U channel to keep it in place laterally. The footings under concrete shear walls will need batter piles for this.

Some things I thought about since then:
-Shear wall holdowns should have shrinkage compensating devices. I think something like Simpson RTUD or ATUD.
-End posts of shear walls should be clearly defined since they are taking a large amount of tension.
-You need header and jamb schedules, and also show them on plan. Otherwise, contractor will just use double stud, which will be grossly underdesigned.
-Unless I'm missing something, I actually don't see a stud design and wood species, or any member sizes besides joist and rim joist.

Edit:
-Also combining steel HSS posts with LVL, not only is there another shrinkage incompatibility concern, but it seems unnecessary since the same purpose can be served with a wood jamb or post. It's also bringing in 2 contractors.
-16" TJI seems a bit deep for this span, maybe reduce that depth and use a heavier TJI.
-You're using 14" LVL beams with 16" joists by the way, which also seems unnecessary but maybe it's to pass plumbing through the bottom. At least it should be considered why it's like that.
-LVL to CMU needs a connection detail, it's not the same as a TJI joist.
-There should be a typical wood diaphragm detail.
-Typical roof guardrail base: I recommend putting the support below the roof instead of above it. You're interfering with the insulation.

 

[andrewu4]

In regards to the podium,
I had run through a ram Concrete/frame combined with a ram concept analysis at least on building 2. It did ok, but I was not thrilled with it as the code is a little mum on a flat plate structure acting as a moment frame and I was basically relying 100% on software. The slab is 12” but it will be 16” at the drop caps. I did use some walls as gravity/pinned to support the slab. I wanted to turn some walls into shear walls but my old boss wouldn’t allow it to give the owner greater flexibility in the future. The walls shown as cmu on some exterior walls are slammed against ex buildings/property lines. They basically have to be cmu (per the arch) and be built from the inside. The arch at one point also said those walls could not be connected to and had to free stand during a fire…..I don’t think they can be switched to concrete to support the podium as they might not have enough room to form them. Above the podium the wood wall right in front of it could be a shear wall, same for all the cmu walls since they have a wood wall in front of them.

I am not sure why there are hss posts supporting short span lvls. I questioned it too.
The arch/owner/MEP don’t know if they want 14” or 16” framing (higher ceilings versus being able to cut bigger holes in TJIs for MEP)

 

[andrewu4]

milkshakelake Thanks for all your help and everyone else’s. I think at this point this has gone about as far as it can go.

I’m going to let my boss know the options are to
1. Get out of it somehow.
2. Sub it out.
3. Delay permit and hire someone quickly with multi family experience.

 

[dhengr]

Andrewu4:
Re: “multi family experience...,” do you mean bigamy?

 

[andrewu4]

dhengr:
Thanks for lightening the mood.