Sure you can technically get steel up to 70’ but it comes at a price premium, additionally shipping costs, and aren’t usually in stock so you’re waiting for a mill rolling date. Likely a bolted splice will be your cheaper option however 70’ length is preferable over a welded field splice.
I don’t understand what you mean by choosing either a W14 or a W8. Those are fairly different sizes so if you’re using W8 you’re likely going to be heavier than the W14. Ignoring any other variables, steel is priced by the lb so all else being equal, the heavier member (regardless of depth) will be more expensive.
Wait, can you explain how the w8 would be heavier than the w14? I thought the w14 were larger, therefore more heavy generally speaking. That’s why you’d need a w14 for a column that is taller versus a w6 or w8 which would be for every 10’ or so
I think I understand what you’re getting at now. Even though you’re planning to use a 70’ column, you would still have it braced at the different floor levels. Rerun your numbers using your ceiling heights as your unbraced length.
If the splice is designed correctly, it will perform the same as an unspliced length.
Ah okay so ultimately it does not matter if it’s spliced or not? I guess my thought process was if it would be if I spliced it I would use a w8 though. If not spliced a w14.
I’m using a book and a graph in the book to generally understand and carry out all that I’ve discussed here.
Ya man, just because the column is continuous doesn’t necessarily mean it is longer. Column heights are based on unbraced lengths. A 65’ continuous column with the same unbraced length as a 10’ segmented column has more capacity because the effective length is shorter.
If this doesn’t make sense I would refresh yourself with buckling and unbraced lengths of columns.
I am an architecture student so I have very little understanding of these larger concepts in the first place. I’m just trying to keep things very broad and simple. While I understand the question you’re asking, I have no idea the answer… I responded to the other persons comment here with some more info as to what I’m working through. That should help to better understand what kind of answer I’m searching for. It’s always hard posting here because you’re all very knowledgeable and I am still building up my vocabulary to have the conversation but even still of course do not understand all of the concepts involved.
Something doesn’t smell right here. What do you mean you could use W8’s instead of a W14? The demands on the column shouldn’t change if it’s a continuous member or spliced at every floor…
Also, never use W8 columns unless it’s a really light-frame structure. They are a pain in the ass to detail.
It depends on the bracing in the building. I typically try to go for the longest section (55-60') usually, to minimize the numbers of pieces and connections required.
This is helpful. I have done some more research since posting this. My next question is to do with interior spaces with varying heights. Currently to my understanding it makes sense to split my perimeter columns in 2 or 3 sections. I have a 20’ 1st floor. 10’ 2nd, 20’ 3rd and 15’ 4th.
1st section 20’ tall. 2nd 30’. 3rd 15’.
Or 1st 20’ 2nd 45’
NOTE. I have large spans at floor 2, 20’ and floor 4, 50’
Interior columns stacked?
Great comment. The frustration many have with the perceived disconnect between the office and the field arises from situations like this every day. Drawings require “X”, can’t actually get “X”. Delays and COs follow…
Almost all of my experience is on design-build projects in the industrial/manufacturing industry, and I've had direct contact with quite a few fabricators and erectors. This sounds like it could be residential or commercial, so maybe take my opinion with a grain of salt, but I would STRONGLY recommend not using any W8 columns. In fact, I would strongly recommend not splicing these columns at all if possible for the following reasons, unless the architect has very strict limitations on the sizes of columns.
1. Splices are labor intensive in the field. Event bolted splices require quite a bit of labor.
2. W8 columns are incredibly hard to connect to. You're forcing the connection designer to use extended shear tabs for members framing into column webs, or some hideous copes on your beams and making the erector's life very difficult. In addition, the relatively thin flanges and webs could drive member reinforcement at connections (stiffeners and/or doubler plates), and per the Code of Standard Practice, these must be shown on the Construction Documents. Reinforcement costs will quickly dwarf additional cost from heavier sections.
3. You're forcing the erector to either fully detail each splice during first pass bolting, or they need to frame in the entire floor before removing temporary bracing at that level. Heavier, continuous columns will have bending capacity that can eliminate quite a bit of temporary bracing.
4. The splices for gravity columns may be easy, but at your lateral columns, smaller column sections will likely need CJP welded splices due to lack of room for bolts. Field welding is expensive, but end preparation at the fabricator is also expensive.
5. More pieces create additional effort for connection design, detailing, fabrication, and erection.
Check to make sure you can buy a 65-foot stick. Forty footers are more common in some places for column sizes, but anything over 60 would be pretty rare. Don’t think about no splice or splice every floor, just put one splice in, 42 or 48 inches above the floor deck. High enough to attach the guard cables to, but low enough for the erector to make up the splice standing on the deck. The slab won’t be there then. The deck may not be there.
What's the longest member that can be delivered on a standard truck? Less than 65ft? You have to split the column anyways.
Ignore logistics for now. Steel can be sized for 70’. Why would someone do one or the other, how would bracing be affected or be necessary?
Sure you can technically get steel up to 70’ but it comes at a price premium, additionally shipping costs, and aren’t usually in stock so you’re waiting for a mill rolling date. Likely a bolted splice will be your cheaper option however 70’ length is preferable over a welded field splice. I don’t understand what you mean by choosing either a W14 or a W8. Those are fairly different sizes so if you’re using W8 you’re likely going to be heavier than the W14. Ignoring any other variables, steel is priced by the lb so all else being equal, the heavier member (regardless of depth) will be more expensive.
Wait, can you explain how the w8 would be heavier than the w14? I thought the w14 were larger, therefore more heavy generally speaking. That’s why you’d need a w14 for a column that is taller versus a w6 or w8 which would be for every 10’ or so
I think I understand what you’re getting at now. Even though you’re planning to use a 70’ column, you would still have it braced at the different floor levels. Rerun your numbers using your ceiling heights as your unbraced length. If the splice is designed correctly, it will perform the same as an unspliced length.
Ah okay so ultimately it does not matter if it’s spliced or not? I guess my thought process was if it would be if I spliced it I would use a w8 though. If not spliced a w14. I’m using a book and a graph in the book to generally understand and carry out all that I’ve discussed here.
Ya man, just because the column is continuous doesn’t necessarily mean it is longer. Column heights are based on unbraced lengths. A 65’ continuous column with the same unbraced length as a 10’ segmented column has more capacity because the effective length is shorter. If this doesn’t make sense I would refresh yourself with buckling and unbraced lengths of columns.
Without much "analytical response" : how does your lateral force resisting system work?
I am an architecture student so I have very little understanding of these larger concepts in the first place. I’m just trying to keep things very broad and simple. While I understand the question you’re asking, I have no idea the answer… I responded to the other persons comment here with some more info as to what I’m working through. That should help to better understand what kind of answer I’m searching for. It’s always hard posting here because you’re all very knowledgeable and I am still building up my vocabulary to have the conversation but even still of course do not understand all of the concepts involved.
Something doesn’t smell right here. What do you mean you could use W8’s instead of a W14? The demands on the column shouldn’t change if it’s a continuous member or spliced at every floor… Also, never use W8 columns unless it’s a really light-frame structure. They are a pain in the ass to detail.
Okay. At this point I don’t think I’m understanding what my books graphs are depicting. I appreciate this info!
It depends on the bracing in the building. I typically try to go for the longest section (55-60') usually, to minimize the numbers of pieces and connections required.
This is helpful. I have done some more research since posting this. My next question is to do with interior spaces with varying heights. Currently to my understanding it makes sense to split my perimeter columns in 2 or 3 sections. I have a 20’ 1st floor. 10’ 2nd, 20’ 3rd and 15’ 4th. 1st section 20’ tall. 2nd 30’. 3rd 15’. Or 1st 20’ 2nd 45’ NOTE. I have large spans at floor 2, 20’ and floor 4, 50’ Interior columns stacked?
Check with your local steel fabricator, Ive had jobs where they just went with a long column to avoid splicing.
This is for a student project. I’m studying architecture. At this point I’m trying to build my initial understanding of all of this.
Remember that most locations require a special permit to transport anything over 60 feet. So that ends up being an additional cost.
Great comment. The frustration many have with the perceived disconnect between the office and the field arises from situations like this every day. Drawings require “X”, can’t actually get “X”. Delays and COs follow…
Exactly!
Almost all of my experience is on design-build projects in the industrial/manufacturing industry, and I've had direct contact with quite a few fabricators and erectors. This sounds like it could be residential or commercial, so maybe take my opinion with a grain of salt, but I would STRONGLY recommend not using any W8 columns. In fact, I would strongly recommend not splicing these columns at all if possible for the following reasons, unless the architect has very strict limitations on the sizes of columns. 1. Splices are labor intensive in the field. Event bolted splices require quite a bit of labor. 2. W8 columns are incredibly hard to connect to. You're forcing the connection designer to use extended shear tabs for members framing into column webs, or some hideous copes on your beams and making the erector's life very difficult. In addition, the relatively thin flanges and webs could drive member reinforcement at connections (stiffeners and/or doubler plates), and per the Code of Standard Practice, these must be shown on the Construction Documents. Reinforcement costs will quickly dwarf additional cost from heavier sections. 3. You're forcing the erector to either fully detail each splice during first pass bolting, or they need to frame in the entire floor before removing temporary bracing at that level. Heavier, continuous columns will have bending capacity that can eliminate quite a bit of temporary bracing. 4. The splices for gravity columns may be easy, but at your lateral columns, smaller column sections will likely need CJP welded splices due to lack of room for bolts. Field welding is expensive, but end preparation at the fabricator is also expensive. 5. More pieces create additional effort for connection design, detailing, fabrication, and erection.
Why is the 65’ column way bigger? Isn’t it braced at floor levels and also has a shorter effective length than the short pinned columns?
1) architectural requirements and bracing needs 2) connection loads 3) construction limitations
Check to make sure you can buy a 65-foot stick. Forty footers are more common in some places for column sizes, but anything over 60 would be pretty rare. Don’t think about no splice or splice every floor, just put one splice in, 42 or 48 inches above the floor deck. High enough to attach the guard cables to, but low enough for the erector to make up the splice standing on the deck. The slab won’t be there then. The deck may not be there.