Lateral System for Open Structure? 2

[Lion06]

What kind of lateral system would you use for an open structure that is really just posts with a roof? This is a structure to cover a patio? It can't lean on anything.

My first thought was knee braces, but the posts are steel clad in wood. So my next thought goes to simple cantilevered columns. My only hesitation is that the footings will end up being very large for a large uplift and overturning moment.

I know there's not an easy way to get a reliable moment connection between a steel post and a glulam beam, so are cantilevered columns my only other choice?

 

[dhengr]

By the way, having read a few of your other posts lately, you have my permission to take the rest of the evening off, unless you are getting time and a half for this work.

 

[Lion06]

Ha! That's funny! I put in 9 hours today. I'll put in another probably 4 tomorrow. That would be 13 UNpaid hours this weekend on top of the extra 8 I put in during the week.

 

[hokie66]

That's not funny, but it reminded me of my early days in a small design office. Did get a nice bonus at year end, though, until one year...

 

[Ron]

Lion06...don't know all your conditions, but your uplift seems high relative to the moment. Your structure is relatively heavy for an open structure.

I'm guessing your footings are in the 4' square range and will have to be fairly thick for OT moment resistance.

What wind area is this in?

 

[Lion06]

Ron-
It's a 120 mph wind area. The OT moment isn't terribly high because there's only 1'-6" of actual wind surface for the wind to act on laterally. So I essentially have 11' cantilevered columns with around 700# acting on the most highly loaded one. Also, the lateral wind load is less than the uplift.

I actually have the footings at 6'-6" square x 1'-6" thick to get stability under control (with the 0.6DL + WL combination). The bearing pressure is extremely low, even in the non-uplift condition.

 

[Ron]

Looked back at your orig. post and since you're not transferring any beam moment...makes sense.

 

[ToadJones]

Using some frame action or knee braces would certainly help, no?

I think you could use some HSS4 knee braces that were also clad in wood.
Your HSS is already wider than the glulam which might look a little funny architecturally (man, did I just say that?)

You could add knee braces with HSS 4's or 4x6 timber then, cover the entire knee brace, column, beam connection with wood, so you'd essentially have a knee brace connection that has sheathing on it for a really rigid connection. It may also look nice architecturally (ouch, hate that word).

I have built a few pavilions like this in the past (builder style, no calcs, just build it for the homeowner).
The large timber posts were sitting on piers and the bottom of the post was slotted and a welded up "T" shape was bolted to the pier with the stem sticking up. The post was slotted to accept the "T" stem and bolted thru with a single large pin/bolt. The base was truly pinned and the stability was all from the knee braced joints. Again, this was cowboy style and maybe the calcs wouldnt have checked out, but they are still there after 10 yrs or so.
Mostly just throwing ideas out there...
I'll see if I can find some pictures.

 

[ToadJones]

By the way Lion-
The more you work for free on the weekends, the deeper you are digging your hole. There is some saying I have heard guys use that goes something like "the more you do, the more you they'll give you to do". I always thought that was a lazy man's comment, but it is true in many ways. In the end, the result is really just a very bad personal life.
I love engineering, but my work is a far off distant second or third to family. There will always be another job somewhere. Other things aren't quite as easy to fix...
I'll shut up now.

 

[gte447f]

Lion06, how much dead load (unfactored) do you have on the columns?

 

[Ron]

TJ..I'll refrain from hijacking this thread to respond to your second post, but if it ever shows up in the "soft" forums...pack a lunch.

 

[Lion06]

Toad,

I hear you. I'm at a bit of a loss for what to do. I'm trying to learn new software while in the midst of a huge design project. Then I get more stuff piled on.

The software, even in the opinion of the developer is difficult, and no one in the office knows it. I'm the guinea pig and am supposed to disseminate the information.

I feel like a heel saying, "sorry, this just isn't going to get done". This goes back to a recent comment someone had about the different personality types in engineering.

 

[Lion06]

There's about 400# max DL on the most heavily loaded post.

 

[ToadJones]

Ron-
I didn't mean offend anyone.
Sorry for the hi-jack. The topic gets me going.
I don't know what "soft" forums are.
Hope I didn't break the rules here.

 

[ToadJones]

I could be way off base here, but for a column with just 400# load, a footing that is 6'-6" in plan seems unreasonable. I don't doubt the numbers at all, but it seems like a moment frame or knee braced frame would be more economical.
I guess I look at it like a structure with really stiff legs that you're just trying to keep from blowing away.

 

[Lion06]

Toad,
I think Ron is referring to the "How to Improve Myself to Get Ahead at Work" forum. I do appreciate the input, though.

 

[Lion06]

It's not the 400# DL that's the problem, it's the 7 K uplift.

 

[ToadJones]

yea, dumb by me...sorry.

 

[ToadJones]

how do you approach the 0.6 Dead term in the combination as far as factoring the footing weight itself? Do you account for soil overtop the footing?
I know there is some debate over this.
Do you actually multiply the weight of the footing by 0.6?

 

[Lion06]

I do multiply the footing self weight and the souls overburden by 0.6. I also did consider the soil overburden in this case. I typically ignore it unless I feel the footings are just getting too big by not including it, which is why I included it here.

 

[abusementpark]

Ha! That's funny! I put in 9 hours today. I'll put in another probably 4 tomorrow. That would be 13 UNpaid hours this weekend on top of the extra 8 I put in during the week.

I hear you. I'm at a bit of a loss for what to do. I'm trying to learn new software while in the midst of a huge design project. Then I get more stuff piled on.

The software, even in the opinion of the developer is difficult, and no one in the office knows it. I'm the guinea pig and am supposed to disseminate the information.

I feel like a heel saying, "sorry, this just isn't going to get done". This goes back to a recent comment someone had about the different personality types in engineering.

They must serve some potent kool-aid where you work.