What does timber quality "T200" correspond to in today's quality measures?

[Ahmada]

Hello,

Question according to the title, what would wood quality T200 (on a drawing from 1974) correspond to according to today's quality standards?

 

[justusandersson]

C 20.

 

[Ahmada]

C 20.

I had hoped for C24. With C20, I get a utilization rate of 0.94 (simultaneous normal force and bending moment), which makes me nervous. Used k_mod = 0.60 though and exaggerated in other places.

Writing PM.

 

[justusandersson]

If the timber is from 1974, I wouldn't be too worried. In BABS 1960 (the building code), they only mention T100 and T70, while BABS 1967 has raised the standards to T300, T200, and Ö-timber. I suspect that this development is more a reflection of changed sorting and testing regulations than actual quality differences. If you want to delve deeper, google "T-virkesföreningen".

 

[Ahmada]

If the timber is from 1974 I wouldn't be too worried. In BABS 1960 (the building code) they only mention T100 and T70, while BABS 1967 raised the standards to T300, T200, and Ö-timber. I suspect this development is more a reflection of changed sorting and testing rules rather than actual quality differences. If you want to delve deeper, google "T-timber association".

Thank you very much for a detailed answer. I'll continue googling and reading up a bit more. If you have the time and energy, I would appreciate it if you could look at the PM I sent you. I'll also paste parts of the PM here in case anyone else has opinions/finds it interesting.

Current outer wall:


i.e., posts 90x120 mm c-c 2.31m are current.

We currently have a load on the post from the following roof beam:


The roof is a lightweight outer roof (felt covering + 20mm raw board + 45x95mm timber cc1.2m + 170mm insulation + 45x220mm roof truss cc1.2m). As well as an inner ceiling (13mm gypsum board + 45x70 +13mm gypsum board). Which I've estimated at 0.4 kN/m^2

Snow load: 0.98 kN/m^2

Wind load:
0.633 kN/m^2
Roof height 2.5m.

The desired extension adds a point load of 4.32 kN over each post in the outer wall (2 roof trusses with point load 2.16 kN. With cc 1.2m, this gives on the outer wall's posts, which have cc 2.31m -> 2 pieces * 2.16 kN).

This gives me the following normal force on the outer wall's posts:


i.e., N_Ed = 13.1 kN
And the wind load gives (after calculation of second order moment) M_Ed = 1.91 kNm

N_Rd is calculated for C20 90x120mm to 49kN (Where K_mod = 0.6 for safety's sake)
M_Rd is calculated for C20 90x120mm to 1.99 kNm (Where K_mod = 0.6 for safety's sake)

Check simultaneous moment and compressive force:

k_m * (M_Ed/M_Rd) + (N_Ed/N_Rd) = 0.7 * (1.91/1.99) + (13.1/49) = 0.94

Is it safe to proceed with this?

 

[justusandersson]

I have replied to TS in a PM that the best option is if he can verify the quality of the timber in reality. The next best option is to consider various forms of reinforcements.

 

[Ahmada]

Problem solved! Thanks to help from Justusandersson. After gaining a lot of new knowledge, I have arrived at a utilization rate of 75% (For C14 - i.e., the weakest possible option) for columns 90x120mm (current column).