Question about the TIA-222-G (urgent)
Question about the TIA-222-G (urgent)
(OP)
Good afternoon,
someone can explain me the checks required by TIA-222-G for minimum bracing Resistance (page 69).
I understand that the bracing must satisfy the condition of Ps, however I do not understand why Pr determine the minimum
required design and Strengths of multiple connecting members.
I wish I could explain the calculation procedure.
Cumpz, thanks
someone can explain me the checks required by TIA-222-G for minimum bracing Resistance (page 69).
I understand that the bracing must satisfy the condition of Ps, however I do not understand why Pr determine the minimum
required design and Strengths of multiple connecting members.
I wish I could explain the calculation procedure.
Cumpz, thanks






RE: Question about the TIA-222-G (urgent)
The main provision is that the total brace strength in the direction braced should be between 1.5% and 2.5% of the maximum design axial force in the supported member.
The idea that the supported member will require more support (Ps = 2.5%) when it is more slender seems rational to me.
RE: Question about the TIA-222-G (urgent)
1)which is a support member in TIA?
2)I have to check the condition of PS in leg members? In my opinion as Pe is high is not necessary to check buckling problems, the geometric characteristics of own section. Thus, not understand the use of Pr, since it is a check for the leg members.
3)Someone can explain me the procedure of calculation I have to ralizar to check the conditions of 4.4.1, to better understand.
It may be a simple concept, but I'm with difficulties in understand the elements of the verification procedure.
Thanks.
RE: Question about the TIA-222-G (urgent)
If you run an analysis by hand (or even using a computer) some of the forces in these secondary members may be very low. Therefore, there is a tendency to use the smallest possible members for these horizontal and diagonal braces. However, as the primary member approaches its buckling load, it will tend to push against its the secondary members at the brace points. These memberse must be strong enough to survive that loading.
Therefore, the Ps value is for the design of these SECONDARY bracing members. If they cannot resist that Ps force (between 1.5% and 2.5% of the total axial force in the primary member) then they will fail before the primary leg member and the leg will fail before it reaches its calculated design loading.
RE: Question about the TIA-222-G (urgent)
RE: Question about the TIA-222-G (urgent)
RE: Question about the TIA-222-G (urgent)
But a doubt still stands related to what control value should be used for the required design quantity of the diagonal minimum strength given by 1.15 x Ps x 0.5 / cos(orientation angle) ?
I would appreciate a clear answer to this fact.
Regards.
JAlmeida (FEUP, Porto)
RE: Question about the TIA-222-G (urgent)
The restraining force (Ps) needs to be perpendicular to the primary member. If you look at table 4-2, the cos(theta) term just resolves that force into a force in the direction of the brace (which is not perpendicular to the primary member).
The restraining force need NOT be taken by a single member. If there are multiple secondary members restraining the primary member (which happens all the time for triagular towers) then each secondary member can be designed for a lower force. This is the basis of the 0.5 factor that you seen in table 4-2.
When you are dealing with triagular tower, you know the horizontal angles are 60 degrees, right? Well, the 0.707 numbers in Table 4-1 are merely the square root of 2 and the 0.866 values are merely the sin of 60 degrees. That's where your 1/0.866 = 1.15 values comes from.... again basic trigonometry.
RE: Question about the TIA-222-G (urgent)
RE: Question about the TIA-222-G (urgent)
What for angles greater than 60 (without affecting the coefficient 1.5), automatically 0.5xPr/cos value (angle) falls outside the range 1.5% to 2.5%.
I can not have bars above 60 º?
RE: Question about the TIA-222-G (urgent)
Last post is not relevant, because I already knew. thank you
RE: Question about the TIA-222-G (urgent)
If the tower is triangular:
sin (alpha) = Ps / Pr <=> Pr = 1.15 x Ps
As I have a brace in diamond, the diagonals have:
cos (theta) = (0.5 x Pr) / Nresistant <=> Nresistant Pr = 0.5 x / cos (theta)
Nresistant - resisting force of the diagonal member Nresistant
Psx0.5x1.15/cos = (theta)
Apart from my section to resist this effort, the Ps must be within the range 1.5 to 2.5 Fs/100.
Example (extreme situation):
angle: 60
Fs (effort of the leg member) = 1203 KN
KL / r = 120 (threshold to be 2.5%)
N = 46 KN (effort-diagonal)
Nresitance = 34.6 KN
therefore does not check the condition in question. This is an example of the checks that do not occur, which is almost all.