Due Diligence

There are some concepts that some codes do not spell out explicitly, but are expected to be addressed, through tools or otherwise, by competent engineers. The extent that Pole Line Design Software Tools cover these is important for an engineer to know and for suppliers to report.

1. The first one is that all clauses in the code need to be satisfied. This means that the final design solution needs to consider the worst case scenario for each individual clause. In other words, the worst case scenario to address one clause may not be the right choice for another. The supplier should either indicate what scenario would be used (alternatively how it would be chosen) to address each clause, or provide the means for the engineer to choose the scenario themselves.
2. The second one is related to weather/storm loads. Both NESC and CSA codes require that the wind direction be chosen to result in the maximum load applied to the structure and its supports (guys, anchors, pole braces, internal members). In other words – wind can come from any direction, so be sure to evaluate the worst condition. For simply supported poles this means just one direction. For more complicated poles, additional wind directions will need to be evaluated to be sure that each component (guy/anchor) experiences its worst condition as well. Since the wind can come from any direction, it is possible that wind directions where the structure is more lightly loaded could cause higher loads in some of the guys and anchors.
1. For Deterministic Storm Loadings, it is implied that the required amount of ice loading at the freezing point with no wind is an additional load case that needs to be considered. This is primarily for clearance tests as it may be the maximum sag condition. The applicability of Extreme Wind, Extreme Ice, and Ice with Wind Loading should be considered.
3. The base elevation of poles and changes in attachment heights along the pole line can impact clearances, separations, sags and tensions. Therefore, the most accurate results are obtained when the actual geometry of the line is used in the analysis of structures.
4. The materials used in wires for span attachments generally have a non-linear Modulus of Elasticity. Therefore the permanent stretch possible in certain wires under creep or under load can impact the design values used for Sags & Tensions.
5. Maximum Sag and Maximum Tension Load Conditions for span attachments are rarely the same.
6. There is more than one type of Nonlinear Analysis that can be performed on Structures. The more nonlinear considerations utilized, the more accurate will be the final result. Some codes have minimum requirements for non-linear considerations. If a supplier's software performs a Non-linear Analysis, it should clearly identify the extent of the Non-linear considerations; including but not limited to:
1. Non-linearity of member reactions due to structure deflection (Geometric Non-linearity)
2. Material Non-linearity of Wire attachments (Non-linear Sags & Tensions)
3. Material Non-linearity of Guy attachments (Stretching of guy wires under load)
4. Non-linearity of loads due to structure deflection (Load Non-linearity).
5. Non-linearity/flexibility of attachment supports .