Alternatives to goal post steel frame to avoid steel columns 2

[Jack2023]

I’m new to the forum so apologies in advance if I get something wrong!

I’m building a double storey extension and the SE has designed a goalpost frame to go where the original rear wall of the house currently is. There are 2 main issues with this design - 1. The columns will stick out into the room, albeit boxed in.
2. Digging up 1m3 where each column will go for PAD01 will be a pain.

I asked about lengthening the beam so it’s supported by the cavity walls and doing away with the columns but apparently this isn’t possible as the steel columns are needed for horizontal integrity, to stop the beam pushing outwards and to tie the new and old walls together. Is there an alternative which means I can avoid putting the steel columns in?

Picture of the SE plans attached

 

[driftLimiter]

Goal Post Frame = Portal Frame?

The reason your seeing that frame is likely due to the large openings and the relatively narrow remaining segments of shear wall that are left.
This is very common at garage doors and large openings, particularly when working with existing buildings.

Another possible solution would a wood portal frame system. Some manufacturers here in the states make these products to be used instead of steel.

Good structural designer would try all wood solutions before going to steel.

The foundation work would likely be about the same for the wood solution as the steel solution (if a wood solution works). There is a breaking point for the wood solutions where they just wont work and a steel frame is needed.

Simpson Portal Frame (wood)

Odds are that steel is the only way to safely have such large openings and fit within the building.

 

[Jack2023]

Thanks. Yeah, I get that but surely the sitting room one side and the garage the other gives it the horizontal stability? The upstairs is tied together above with studwork rather than steel but in the UK they do love a bit of steel!

The portal frame you are suggesting, that’s the same thing but made from wood rather than steel no so wouldn’t I still have the same issues?

 

[driftLimiter]

There are a lot of details and things to consider about the project that I'm not privy to. Its possible the adjacent walls aren't sheathed adequately, or they dont have tie downs, or there is no clear way for the forces to migrate over to them.

Like I said a prudent designer would explore all possibilities before going to steel.

The wood portal frames are a bit slimmer than typical steel frames as they are designed to pack into the studwall.

To really nail this one down you need to talk more with the designer who specified the frame. There may well be a very good reason that it is needed.

 

[Jack2023]

Thanks. I have spoken to him and his rationale was that the columns don’t just hold up the steel beam, they provide vital horizontal integrity to the external wall that would have been held by the existing wall being removed. It will also prevent the steel beam from pushing outwards on the wall and also tie in the new and old walls.

Surely there are alternative ways to achieve this though and the point of my post was to get some alternative ideas that I can put to him as I don’t like the current solution.

 

[driftLimiter]

Yes, I can get on board with the rationale, it really comes down to the numbers. Your assumption : "Surely there are alternative ways to achieve this " Its not always true given a certain set of constraints sometimes the steel frame is the only (or the best) solution.

In principle you have removed strength / rigidity from the building. Chances are that removed strength needs to get made up for somewhere else.

If you think about it you have removed say 10 feet worth of wall at the base, you basically need to provide 10 more feet of wall (worth of strength and rigidity) somewhere else to offset that reduction.
The problem is compounded if your adding more loads to the existing building than the original design.

 

[Jack2023]

Not meaning to be rude but you’ve not actually added anything other than stating the obvious. I’m aware of the rationale - I put it in my original post!

It’s not the only way of doing it - I can sink the columns into the wall, I can keep the brick return etc. I was hoping for some better ideas then rather than, “hey, there’ll be a reason!”

 

[jayrod12]

The problem is, we're not privvy to all of the constraints, nor are you paying us to go through them.

There could be some good reasons that wood wouldn't work, or that the rooms adjacent don't help. We don't have the full picture.

For us to know whether there truly are other options available, we would need to know all of the details of the project. The problem with that is, we're relying on you, a non-engineer, to provide what you think are the pertinent information. And you're also being slightly combative in the sense that you're receiving responses that are telling you we can't give much more answers, but you're ignoring them.

Since we aren't there, boots on the ground, with all of the information handy, we can't help you the way you want to be helped. You want a full second opinion, so pay another engineer to review and give you an actual opinion. Don't come to a forum that is meant for engineers to help each other with technical issues, and complain when we won't give you free engineering.

 

[BridgeSmith]

Any modification to the structural system needs to go through the SE. If you want changes, talk to your SE.

 

[driftLimiter]

You can spitball ideas all day and night, but if they don't work out with the loading and the code requirements then there is no point.

I think it is an error to assume that there are other means to achieve the same result that don't involve the same (or more) amount of work.

I've done a lot of this type of work, quite often we end up with a steel frame and new footings just like what you have shown. That is because we vetted out the alternatives and found this solution to be the ideal.

Here are some more spitball ideas for you:
Building a new concrete wall to take the lateral loads. Build new competent footing for wall.
Build a new cmu wall to take the lateral loads. Build new competent footing for wall.
Extend the length of adjacenet wood shear walls. Build new competent footing for wall.
Use light gauge steel shear panels with hold downs. Build a new competent footing for wall.
Use exterior diagonal tie wires down to new deadman anchors to resist the lateral loads.
Use interior shear walls and three sided diaphragm assumption.
Offer to stay at the site for the rest of your life and personally hold up the wall against lateral loads.
Don't make such big openings.

 

[LittleInch]

That right hand one maybe lunch through the wall and put the bean and fitting in the garage?

Or maybe build a brick pillar inside the garage to provide some lateral support and put the steel on it.

On the LHS, think you've just not got enough on the end of that little stub wall between the living room and the dining room. The steel column is probably the smallest intrusion into the space your going to get I think.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[phamENG]

Offer to stay at the site for the rest of your life and personally hold up the wall against lateral loads.
Don't make such big openings.

I'm not sure which of these is my favorite.

 

[GeorgeTheCivilEngineer]

You could extend the beam and put the steel columns into the width of the wall, reducing the distance they intrude into the room. If suitable metal to masonry frame cramps are used this should not affect the walls.

I see why the engineer has put in a frame there and agree with the other comments (for the American engineers - as this is UK it'll likely be an unreinforced masonry building).

 

[BAretired]

Review your concerns with the Engineer of Record. If you don't like his response, retain an expert.

 

[hokie66]

Based on the limited information we have, I would say your engineer is giving you good advice.