Need Quick Advise From You Construction Types

[copb8tx]

(Admin, if in wrong session please feel free to move or delete)

I have a carport shed over my boat that is 14' x 14' x 30'. It sits on a very sandy base and only has auger posts into the ground to hold it down. That's the way I bought the spot in the park and appears to be how each unit is secured.

My issue is the cover sways very significantly from side to side when the winds are very high. My plan is to run SS guy wires from the peak of the roof to the side posts to triangulate the structure. I'd use turnbuckles to create tension on the wires. I think this would add sway resistance but still have some 'give' so it won't rip out the anchors.

So the question is, what size cable should I use? 1/4", 3/8", or ??? Which size in manageable to work with but still provides minimal stretch when each run is about 10-12'?

 

[Stee6043]

I think you may find you get minimal benefit from cable in this scenario. You can create tension on the structure but the impact on its overall rigidity is likely to be marginal.

Before you invest in SS cabling and turnbuckles go throw a couple of ratcheting tie straps on it when it's windy the next time. See if you can make it sway less. This might inform your next steps in a very low cost manner.

 

[copb8tx]

That's excellent advise. Thank you

 

[paulswagelock]

Agree with above, test it first.
The wires will likely help but you will probably need them on many of the support channels, not just a couple. 3/8 would be plenty strong for this use.

 

[copb8tx]

Thanks guys.

I can only make them do long without them interfering with the boats t'top and lights. In the back braces I can go with 10' runs on each side. Forward of that 8' or less will be the max.

 

[ttmott]

First, is the structure rated for the wind loads in the area installed? There should be a placard on it for the rating compliance. Ok, from an engineering perspective the bending strength on the legs (from the picture) is probably the weak link. So, to cross-brace as you are asking would no doubt make it a stiffer structure but doesn't resolve the strength of the legs especially in the mid section. What I would consider is to double up all the diagonal bracing connecting lower on the legs and more towards the roof center. This will serve to better resist racking and transfer the loads lower on those legs. Secondly, look at how the siding is attached as that is the racking strength in the longitudinal direction. If the structure is flexing in that direction look to add fasteners / replace the fasteners on that siding.
You could also look to double-up the legs towards the inside of the structure.

 

[Skybolt]

Your going to need to do an "X" and not a triangle. But to @ttmott Tom's point, the middle of the structure is also going to need to be strengthened. Not sure how to do that because of the augers. if the base were held down much like a building is with a footing that would help things a lot. Putting too much pressure on the cables could also buckle the building. So anything more the "taught" might be too much. Not an easy thing to fix.

 

[Woody]

Looks like a couple of the angled corner braces on the right side aren't attached on both ends. Maybe a check of existing connections is due first.

 

[copb8tx]

You're correct. They were just tap screwed in and pulled out last could days of high wind. We're going to redo them with through-bolts

 

[scoflaw]

Seeing you don't need all that height and width, longer angle brackets would work

 

[Stee6043]

You're correct. They were just tap screwed in and pulled out last could days of high wind. We're going to redo them with through-bolts

I bet you'd see a significant improvement if you found a local tig welder and had them weld those braces. 98.736% of the reason that thing is swaying is because those are bolted connections.

That said, once welded you might identify a weakness elsewhere in the structure that required the bolted vs welded connections . I doubt that though. I assume they are bolted for ease of transport and cost...

 

[Lazy Daze]

I agree that anything that is "pulling" the corners together is going to cause issues and buckle the building. However, if the red lines that Sky drew were SOLID pieces like a pipe or angle iron, and secured to each other in the middle, then that should help. The trick is making this easy to do. Pipes would likely be more secure over that run than angle iron. If you could make each red line out of two pipes - one fitting inside the other - then that would be a little easier. The upper pipe could be fastened more securely, yet allowed to pivot so that when not used, it would simply fall vertically against the building. Where the two pipes meet (slid over each other... and sliding over each other 2 or 3 feet would be ideal), there could be some holes drilled to be secured by bolts/wing nuts or even some trailer coupler pins (easier/faster). The bottom pipe could secure to a small bracket that you fab out of L-channel and again use a trailer pin. One you had this figured out and done, it would probably take all of 2 minutes to secure or unsecure.

 

[copb8tx]

I just climbed up each post and reattached any loose crossmembers and tightened all the existing loose screws holding the square tubing together, which was a lot. The stiffness of the structure was definitely improved, but not dramatically.

So, I'm hearing that the cable solution will be destructive because it'll put constant tension on the structure and eventually warp/bend it, correct? That leaves steel crossmember reinforcing bars. My concern with these are that if they shear their connection they'll pivot down onto the boat and I won't know that for a month or two, probably causing significant damage. I think maybe I'll do the large X at the back of the unit as described by Sky and then shorter braces that come down the sides more and meet at the peak over the tongue of the trailer. That way I can come and go without disassembling anything. We also already plan on through-bolting those the existing angle supports, which are currently just tap screwed.

I really appreciate everyone's help. I was 100% going down the cable route before hearing from y'all. Thank you.

 

[dwna1a]

Lazy, please correct me if I’m wrong.

Then structure seems to have plenty of height, if joists were added, not at every spot but maybe every other two. Basically 4’ centers. Wouldn’t that tighten up the structure by transferring the side loads from the wind? Also it’s in sand, could the auger points have worked themselves up a bit from the wind blowing it around?

 

[ttmott]

Don't weld on it.
Assuming it is aluminum welding will remove about half of the structural properties (tempering).

 

[mrsrobinson]

If he adds crossmember reinforcing bars how will he get the boat out?

...

 

[Woody]

How is that thing built? If you follow the 'studs' up to the angled corner what is that? Is one thing sliding into the other?

 

[Nater Potater]

I'm in the same camp as @dwna1a for adding joists to the existing. They started with the right idea along the peak, but didn't run them nearly far enough, allowing most of the roof to flex unchecked. Were it me, I'd run horizontal stringers to triangulate the roof proper, then tie everything together with the side stringers to move the hinge point further down the vertical walls. This would help by removing most/all flex from the roof, then stiffening the walls so as to move their force transfer point closer to the base, thus reducing the leverage they have on the ground augers. In other words, triangulate the snot out of it!

 

[copb8tx]

The structure is build with 2" square typing with sleeves in between pieces and then screwed through the connection.

On the fence about Lazy's approach. Can see it would ad great rigidity but seems pretty complex and a bit of PITA to work with and align when it comes to hooking it back up after opening it. That said, with some padlocks it would add some security but that isn't a priority since the unit is behind a manned 24/7 guard shack.

I like Nater's horizontal cross member approach but would need to see what clearance I have for running lights/antennas on the roof of the t-top. The diagonals are what my initial approach was going to be, and has risen back to my preferred first approach.

 

[Timeflys]

Could you take out a couple of the side panels or create slots to allow the wind through? … reduce the sail area and resistance…I’m assuming the shelter is for sun and not so much for rain.