External pressure stress coefficient problem
Thread Content
I’m seeking help from everyone. In the calculation of external pressure under GB150, there is an external pressure stress coefficient B, which is obtained by referring to table A based on values such as L/D0; see GB150.3 4.3.2. When it comes to the calculation of the external pressure reinforcement ring, there is another value B, which is determined using a formula, as specified in 4.5.1.2. These two are clearly different; which one should be pressed when there is a reinforcement ring? SW6 follows the first method.
Is this B used to calculate the moment of inertia required for the reinforcement ring, and is it different from the one before? That’s how it should be understood, right?
You’ll know once you do the calculation completely
The calculation of external pressure essentially involves a two-step verification process: first, verify the stability of the container; if this verification fails, add reinforcement rings in appropriate locations； Recheck the stability of the reinforcement ring; if it fails, increase the moment of inertia.
I did the calculations, and it didn’t work. What’s used here is called the B value; a reinforcement ring needs to be added. Once that reinforcement ring is in place, the B value is calculated again – let’s call it B1 – and it’s different from the previous B value. Moreover, I see that the B value shown on SW6 is B, not B1.
I know this step. What I don’t know is that the methods for calculating the two B values before and after are different; why is that?
Show everyone your calculation process and they’ll understand
This post was last edited by zjq1962 on 2019-12-27 at 11:23. The stress coefficient B mentioned earlier is used in the calculations for the external pressure cylinder (it helps determine the structural parameters; B is derived from A, and from this value the allowable external pressure can be determined). The stress coefficient B mentioned later is used when the calculations based on the external pressure of the cylinder do not yield satisfactory results; it is utilized when calculating the inertial moment of the combined section formed by the cylinder and the reinforcing rings added to it. The functions of these two coefficients are different. When the external pressure calculation fails, a reinforcement ring is installed to reduce the calculation length, and then the external pressure calculation for the cylinder passes. However, the reinforcing ring installed may not necessarily meet the requirements for stability under external pressure; therefore, subsequent calculations are required (to determine the structural parameters of the reinforcing ring, calculate B, then obtain A, and finally determine the required moment of inertia).