Handling 16m long glulam beams (roof beams)

[bossespecial]

Thank you!
Just outside Hässleholm (Skåne).
I will definitely take a look at it, I don't want to miss this. I love working with large spans.
Unfortunately, there is no alternative support. The owner is determined and has discussed this with the architect.

Ok, I thought it was you who were going to expand. I assume you are helping them with calculations? If it's decided that it should be glue-laminated timber and, as a result, requires a continuous beam for it to work, then I wouldn't worry about transport or cranes, etc. It's just a consequence of the requirements.
Regarding the support pressure, I would suggest making a casting at the top of the wall where the wooden beams are placed.

 

[HEA260]

Ok, thought it was you who would be building out. I assume you are helping them calculate? If it's decided to use glulam, and as a result, there's a requirement for a continuous beam for it to work, then I wouldn't worry about transport and cranes, etc. It's just a consequence of the demands. Regarding the bearing pressure, I would suggest doing a casting on top of the wall where the wooden beams will be placed.

Exactly, I am helping them calculate. Yes, I have to let it cost according to the demands. But I still want to try to save as much as possible since I want to budget for a geotechnical survey (40-50 thousand). As I am not quite sure about the ground bearing capacity.

Very good idea with casting on top of the center support. You imagine it as a smaller beam? It would be easy to attach some angle irons, for example. And concrete bonds well to Leca blocks. Thanks for that!

 

[Lulaua]

Have you looked at takelement? Like the ones from svenska Takelement? No idea about the cost but it can handle the span, and you'll quickly get a finished roof.

 

[bossespecial]

Exactly, I help them with the calculations. Yes, I must let the cost reflect the requirements. But I still want to try to save as much as possible because I want to have a budget for a geotechnical survey (40-50 thousand). Since I'm not entirely sure about the ground's bearing capacity.

Very good idea with casting on top of the central support. You mean like a smaller beam? It becomes easy to attach some angle irons, for example. And concrete adheres well to Leca blocks. Thank you for that!

What makes you unsure about the ground's bearing capacity? How are the surrounding houses founded? In areas around Hässleholm, there's a lot of moraine, sand, and gravel, and it's no problem to lay the foundation for a one-story house. Get someone to dig some test pits to see what the soil looks like. If you calculate with 50kPa, you'll go far considering the small loads.
What is the reason for a 120-slab with so much reinforcement, exposed concrete floors?

 

[Stefan1972]

Now I'm not an engineer, but can someone explain the idea and need for beams in a single length in such a construction? Are they part of keeping walls upright so that there are also tensile forces, or what? Personally, I only see roof loads that are directed downwards, and in that case, it doesn't matter much if a beam is in several parts if the supports are accordingly.

 

[prototypen]

With full lengths, you get a fixed clamped end at the mid-support so the load tries to bend the beam over the support.
With a spliced beam, the support just becomes like a hinge.

Protte

 

[Gabbe1]

I'm not a designer, but can someone explain the thought and need for beams in one whole length in such a construction? Are they a part to keep walls upright so there are also tensile forces or what? I only see roof loads directed downwards, and then it doesn't matter if a beam is in several parts if the supports are accordingly.

No, it has nothing to do with horizontal (tensile) forces. Imagine a 16m beam supported on three supports, one at each end and one support in the middle. If the beam is 2x8m and thus divided at the middle support, the maximum moment occurs in the middle of each beam. (4m from the supports) If the beam is continuous instead, the maximum stress occurs right above the support. You could say that because the beam is not divided over the support, it will resist when the load from above wants to bend the beam over the support. This resistance results in the beam bending down significantly less between the supports. The beam can thus be a more slender model and still provide the same deflection as a larger, but divided beam.

 

[Stefan1972]

Yes, but don't they size the supports down to the floor/warehouse so that it doesn't move there? Natural movement is one thing, but they don't expect it to move excessively there, do they? You can look at many glued laminated timber halls. It's not uncommon to have long beams, but often they are divided at each support point? Like posts down to the foundation.

 

[Gabbe1]

But isn't the support configured down to the floor/storages so that it doesn't move there? Natural movement is one thing, but surely you don't expect it to move significantly there? You can go and look at many glulam-built halls. Long beams are not unusual, but they are often divided at each support point, right? Like posts down to the foundation.

The supports are assumed to stand firm and without movement.
I think you misunderstand the purpose of a continuous beam; in these cases, what is sought is higher material utilization of the horizontal (roof) beam. I tried to describe it in my previous post.

 

[HEA260]

Have you looked into roof elements? Like from Swedish Takelement? No idea about the cost but they can handle the span, and you'll quickly have a finished roof.

No, we haven't looked into that, will check it out as time permits. Thanks for the tip.

 

[HEA260]

What makes you uncertain about the ground's load-bearing capacity? How are the foundations of the surrounding houses constructed? In the areas around Hässleholm, there's a lot of Morön, sand, and gravel, so there shouldn't be any problem with laying the foundation for a single-story house. Get someone to dig some test pits and see what the ground looks like. If you calculate based on 50kPa, you'll be in a good position considering the small loads.
What's the reason for a 120-slab with so much reinforcement, exposed concrete floors?

SGU's website says "glacial sediment" and the client talks about a lot of water in the ground. I'm worried about silt. I thought the same as you, try to design for 50kPa. But the central support requires a large footing. I need to do some more calculations on that. A geotechnical expert said he wouldn't dare to load the ground with 100kPa without a geotechnical survey.

Regarding the 120-slab: there's a lot of water in the ground, the client wants hydronic floor heating, several uncertainties, the project is in the planning permission stage, and I am new. I’d rather go with a 120 slab and reinforcement 10150 now, which can be reduced to a 100-slab and reinforcement 8150/6150 later, than to write a too low number now, I think. Then I don't know if a crane should be used and where to place it.

What would you decide knowing the above?

 

[bossespecial]

Is the sole really that large if you calculate at 50kPa?

Then you can take other measures with the ground to "relieve". But with test pits and an experienced digger, you can go a long way since there is a lot of money to save on a geotechnical survey.
In this situation, I would have started from 100mm, 6s150 (if it's not going to be an exposed concrete floor) and assumed there are no radon issues. The crane would have to stand next to the slab.

 

[HEA260]

Does it really become such a big foundation if you calculate at 50kPa? Then other measures can be taken with the ground to "relieve". But with test pits and a somewhat experienced digger, you can get far since there is a lot of money to save on a geotechnical investigation. In this situation, I would have started from 100mm, 6s150 (if it's not supposed to be an exposed concrete floor) and assumed no radon problems exist. The crane would have been placed next to the slab.

I have q_d = 32kN/m from the roof beam on the center support (wall_x). Then you have to add the weight for wall_x and the weight of the foundation. I haven't had time to calculate it more than roughly, requested drawings for the existing foundation. I want to calculate what the current load on the ground is.

If I get the opportunity, I will follow the project and calculate the final foundation after excavation has started.

I am also calculating the slab; you're probably right that it can be reduced to 100mm, 6s150.

Thank you for sharing your experience! It is a great help!

 

[Gabbe1]

I assume you are aware that there is more load on the middle support when using a continuous beam?
It is easy to assume that with evenly distributed load on the beam, the loads are distributed on the supports according to: 1/4, 2/4, 1/4, which is also correct if the beam is split at the middle support. But with a continuous beam, this is no longer correct.

 

[prototypen]

The question of raising the beams involves using a wheel loader with pallet forks if you can position the beams before the gable wall is built. Alternatively, a wheel loader can place them just inside the gable wall, and then you have to slide the beams.

Pouring 150 mm feels thick, more suited for a tank garage.

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