| Applies To | |||
| Product(s): | AutoPIPE, | ||
| Version(s): | ALL | ||
| Environment: | N/A | ||
| Area: | Analysis | ||
| Original Author: | Bentley Technical Support Group |
Problem:
Simply, the support at this location, is a V-stop support, with coefficient of friction of 0.3. The largest load in the horizontal at this location can is the largest downward load multiplied by coefficient of friction. In this case, probing the 'Restraint Loads', max downward load on the support, is -27221N, with this, and coeff of friction of 0.3, the side ways load on this support can only physically be 8166.3N?? Anything past this limit of friction the pipe will slide on the support and this load will instantly reduce?
Yet we have a sideways load of 15409N…
What are your thoughts on why this sideway load is greater than it possible can be, and secondly, why is this linked to thermal only, and when you take a combination of thermal, gravity and pressure loadings, this reduces to 7210N from 15409? Seems that the software is calculating the load incorrectly.
Solution:
AutoPIPE is correctly calculating the loads.
Correct that the lateral load cannot be greater than the largest downward load multiplied by coefficient of friction.
As usual, for non-linear load sequences the result of an individual load case may not make sense if load sequence is ignored. Therefore, from the output report consider only the operating conditions (i.e. GT1P1, GT1E1, GT1W1, etc..) and ignore the individual load cases (i.e. Gr, T1, P1, E1). Consider the individual load cases when the results of the operating condition are being questioned. Keep in mind that individual load case(s):
A. Displacements can be larger than a gaps on a support allows
B. Support may have a load in a direction of a gap that is not touching anything. However, when the individual load cases are added in a valid combination, the results of non-linear load sequencing are correct.
C. Etc..
Upon closer look at this example, from the output report found the load sequence of combination GrT1P1 = Gravity then Temperature then Pressure.
Gravity was the initial case found to be 8143 N to the Right, Downward force at that time is 27,222 N downwards. This when multiplied by the friction coefficient gives 8167 N which is the maximum resistance the friction can give. 8143 N < 8167 N OK
Temperature case was then applied, it first cancels out the existing gravity load by force = 8143 N to the left , and then continue to act in the left direction developing friction force on the support = 7301 N. (7301 < 8167 OK).
The results for GT1{1} combination would make more sense in this case showing that now the lateral load on the support is 7301 N (< 8167 N, the downward force * friction coefficient limit). However the total forces for T1 load case was reported as = 8143 N + 7301 N = 15,444 N to the left.
Pressure load case was then applied, 91 N (< 8167 N OK, the downward force * friction coefficient limit) to the RIGHT.
The GT1P1{1} combination gives you the final state of support forces which as mentioned is 7,210 N acting to the Left direction.