Strong vibration wooden beam ceiling

Good day,
we have built a prefabricated house with a timber frame construction. On the upper floor (children's room), our floor vibrates a lot (currently still without floor covering, only screed). This has also been confirmed to us by two experts. The site manager has shown us the structural calculations, which we do not understand in detail. Is it possible that the structural calculations are correct and the vibrations are still so extreme? I get a queasy feeling in the room when someone else walks in it and you can feel when a truck passes by the house.
I would like to measure the vibrations myself. Is that possible? With which device?
Best regards

Nope. As described, this is not normal and should not be like that. The vibration verification should also be explicitly mentioned in the structural analysis. It's about serviceability after all.

Conclusion: Call in the structural engineer, he signed off on it and is also liable for it. The address is on the structural analysis.

The vibration proof is as follows:

Does that help?

Well, at least. And now you call the structural engineer and ask him why his ceiling is shaking like that.

Hello,

unfortunately, I can’t help you much with the vibrations in wood, whether and how much is permissible.
For the static explanation: the letter "n" stands for the utilization, meaning the value 0.86 stands for 86%. 1.00 or 100% means maximum utilization of the component before it goes from pure deformation to failure. In some trades, even a theoretical exceedance of 3% or n = 1.03 is allowed as a result if sufficiently large safety factors have been taken into account beforehand.

The entire ceiling here has a utilization of 0.95, meaning 95%. There is not much "room" left for deviations.
What I would advise you to check:
Are all beams installed as calculated? -> Check quantity, width, and height!
Is the screed installed as specified in the static calculation? -> Height should, for example, be measurable at the stairs or similar
Very important to check: material quality!
The static calculation must specify the calculated material quality, it could be, for example, "GL24h" or "GL24c". There are certainly others; I don’t have more in mind right now -> request proof from the prefabricated house manufacturer which quality class was used for you

Since the ceiling already seems very soft, every additional kilo must be carefully considered. A waterbed, aquarium, or a fully packed bookshelf can soon become a problem.

The calculation should also include the deflection of the beams. You can check this by, for example, placing a laser on the floor in the hallway, standing in the middle of the room with 2 or 3 people, and measuring from the laser to the top of the finished floor level. I’m curious what you will find out!

This all sounds to me like profiles that are too small have been used in some area. Don’t let the construction company brush you off with statements like "oh, it’s fine!" I wouldn’t want the ceiling to come down later...

Best regards from the steel construction engineer

Hello,
thank you very much for your answers, I spoke with the structural engineer, he assured me that everything is within the standard range and that the subjective perception varies. However, now nothing can be done anymore. The beams are already installed in the ceiling at the factory.

They initially did not have drywall sheets on yet, so we could have checked the beams. Meanwhile, wallpapering has already been done. At most, I can verify by photos whether the number is correct.

@Simon-189 many thanks for your explanation and practical suggestions for checking, that helps me a lot! I will try to determine the screed height (5cm).
I have attached the material quality, is that okay as it is? Although only GL 24c was actually used for the beams in the detailed listing. Is that O.K.?
The deflection of the beams has been calculated, could you please take a look at it as well?

Best regards