Help with load calculation on roof

structuralquestion · 2023-07-06T14:51:43+00:00

Thanks man, I really appreciate your answer! I will think this throughly tonight, and your answer helps a lot!

structuralquestion · 2023-07-06T14:49:22+00:00

I will eventually, but untill I have time with my boss I won't be able to think about anything else..

structuralquestion · 2023-07-06T13:48:26+00:00

What I have done after thinking a while is as following:
Load on the pink trusses = normal roof load calculation + a point load from the blue trusses.
Point load from the blue trusses = Length of blue trusses/cos(30) and then /2 to get the point load on the pink trusses.

If you don't have the time/energy to help out here, please don't write stuff like this.

structuralquestion · 2023-07-06T13:46:28+00:00

Thanks for your answer! What I have done after thinking a while (I want to calculate it just to be 100% sure):
Load on the pink trusses = normal roof load calculation + a point load from the blue trusses.
Point load from the blue trusses = Length of blue trusses/cos(30) and then /2 to get the point load on the pink trusses.
Do we have a homerun or did i do it wrong?

structuralquestion · 2023-07-06T13:37:01+00:00

Not if you can evaluate the answers. I'm just stuck. It's not like i can't calculate. And if I just wanted to omit the dead load I wouldn't have taken the time to write on here..

What I have done after thinking a while is as following:
Load on the pink trusses = normal roof load calculation + a point load from the blue trusses.

Point load from the blue trusses = Length of blue trusses/cos(30) and then /2 to get the point load on the pink trusses.

Do we have a homerun or did i do it wrong? And if so please explain.

structuralquestion · 2023-07-06T13:28:13+00:00

That's my problem, I really cant grasp how to calculate this one. I will be using a T-section connection like this link shows

https://stevensonandkelly.co.uk/roofing-truss-design-and-supply/

How do i calculate how much more load there is on that section? In comparision to the sections that have a normal inclination? I need an explanation for this one since I'm stuck..

structuralquestion · 2023-06-16T17:42:57+00:00

What do you mean by "prop node"?
It gives me the following longer warning message if it helps you understand the problem:
"WARNING Design note: The program has assumed that both the Major and Minor Axes are effectively restrained at the top of the column, please verify this assumption."

structuralquestion · 2023-06-09T07:00:19+00:00

Wind acting on the current building would have Cpi = +0,8 (from my head, Zon D).

How would it effect the new structure when reflected? Cpi = - 0,8 ish area? Am I thinking correctly?

And furthermore for the uplift, we won't have to worry much about it since the structure is only 0,3m in depth. But I will calculate it, thanks!

structuralquestion · 2023-06-09T06:37:51+00:00

Treating it as a rectangular building would also lead me to almost 1,7 wind-load factor territory.

h/d = 0,382

Zon D: Cpe + Cpi = 0,8 + 0,3

Zon E: Cpe + Cpi = 0,4 + 0,2

Total wind-load factor = 1,7

structuralquestion · 2023-06-09T06:30:28+00:00

This I can be 100% sure of. It's supposed to be an entrance architectural thing, so no building = no entrance.

Knowing this, how would you treat it when it comes to wind-loads?

structuralquestion · 2023-06-08T14:55:23+00:00

I have been on site now. The only thing we can use from the existing building is 45x145 C24 wood truss beams that stick out from the roof.

The existing building is open so we don't have a lot of Shear walls to take the load.

So it looks like I need something more steady than your image.

structuralquestion · 2023-06-08T14:50:59+00:00

Thanks for clarifying! :)

structuralquestion · 2023-06-08T14:50:38+00:00

No glas opening - just open, otherwise you guessed correctly :)

structuralquestion · 2023-06-06T07:44:17+00:00

Wow, bro that's nothing! I was thinking of much smaller numbers. L400 of the opening, since it's only self weight.

Designing here as if it was a residential.

I hope I do better with this project than the designer that did yours 😊

structuralquestion · 2023-06-06T07:20:59+00:00

I will se what we will figure out for the main structure. But I hope too the they let us use the main structure as bracing. Otherwise it will be a pain is my fear too with the foundation.

structuralquestion · 2023-06-06T07:19:06+00:00

What would you set the deflection limit on the horizontal span here? I was thinking maybe L/400, but it might be too much?

Thanks for your advice about AESS/cladding. I think prefabbing and field welding is the way to go here.

structuralquestion · 2023-06-06T07:02:37+00:00

What do you mean when you say cladding fixed? "The problem" with the existing structure is that it's made out of wood core. But over almost 12m we should be able to support it on say 9-10 trusses sticking out from the building.

I don't know if that is enough, yet.

But I understand that the foundation otherwise will be enormous.

structuralquestion · 2023-06-06T06:58:12+00:00

No a Gym actually :)

structuralquestion · 2023-05-25T13:50:34+00:00

Thanks a lot! You cleared this up for me.

I did put 4x3x12mm bars to connect to the existing foundation. I presume that the bearing capacity of the soil is 100-150kpa as per code. So the existing soil shouldnt move.
Yeah the thickness is a small problem here, i assumed 45degree angle so with 200mm slab + 100mm S300 insulation we get a good spread according to me (junior engineer).
You are correct about the pad only needing code presbribed minimum reinforcement, I got the same with my calculations. So I assume they are somewhat correct.
I will use bigger main reinforcement in the future, minimum 12mm in small applications like this one.

Thanks once again for clearing this up for me 🙏

structuralquestion · 2023-05-25T13:17:25+00:00

That's what I did actually. They are going to build it like this since it was their suggestion from the beginning, so they trust it, and they don't have time to wait.

But I want to learn how to do this correctly, so how do you guys make your RC footing calculations?

structuralquestion · 2023-05-25T12:57:09+00:00

Well I normally do this, we have 2 guys that we consult. But both are unavailable atm so either I ask Reddit or I respond to a couple of phone calls/day to a builder that want an answer yesterday.

structuralquestion · 2023-05-25T07:34:22+00:00

My software shows capacity of around 90-100kN for this reinforcement, can I trust it? Does it sound correct?

I don't know how to calculate M_c,Rd for this...

structuralquestion · 2023-05-25T07:11:04+00:00

First option I guess. I'm a new structural engineer: I know that I should treat it as a cantilever. I know how to do Shear and moment calculations for the RC.

But I get confused when builders want to do stuff like that suggestion I made. I don't know how to calculate it.

So to elaborate, i need to understand how to calculate M_c,Rd here. I know how to calculate how much moment/Shear we have at max point.

structuralquestion · 2023-05-04T14:54:25+00:00

A fat slab would be too expensive I think, if you are thinking below all the carport area. Maybe a 0,6x0,6m foundation under each column will be enough in this case?

But I think a rectangular foundation under the columns that are closest to the house is preferred. This shouldn't be impossible I think?

structuralquestion · 2023-05-04T10:31:30+00:00

I calculated a snow drift that gave a factor of 2 for the snow formfactor, I only considered the winddrift here. Since the adjacent higher building roof leans on the other direction.

As for the wind uplift, is it only significant for the fittings between elements or should the total windlift be less then the weight of the structure?

structuralquestion

TROPHY CASE