There are various degrees or levels of Nonlinear Analysis for Pole Line Structures. The various Codes/Standards do not specify a level of sophistication in the analysis, just that some kind of Nonlinear Analysis is performed on the pole or structure.
The most basic and minimum requirement is what we call Level 1. Other levels are possible which increasingly model the pole/structure(s) in the line with more accuracy to how they would respond to the required loads. These levels are:
1) Level 1 - Model the pole/structure to respond (deflect) in response to the applied loads. No changes to the assumed loads or guy attachments is taken into account as the pole moves.
2) Level 2 - In addition to Level 1 ability, also take into account the change in position/angles of guying attachments as the pole deflects. This more accurately models guys when they are not completely inline with the resultant loads. Guying can also accurately show partial support for loads that are as much as 90 degrees out of line.
3) Level 3 - In addition to Level 2, also consider the change in angle of load attachments as the pole deflects, PLUS the change in the load. As the pole moves in response to the applied loads, the wire attachments will become stretched or slackened, which changes the previously calculated load to apply to the pole. With this level, these loads and their resulting force angle will be updated on every iteration of the Nonlinear Analysis.
4) Level 4 - In addition to Level 3, the project or area containing poles and pole lines, is evaluated as a complete SYSTEM. The pole deflection effects of one pole are considered within each iteration for its impact on the attachment loads and angle of other poles. This is the ultimate goal for any tool claiming to accurately model how poles behave and are loaded.
Most Pole Line Design tools only perform a Level 1 analysis today; if they do Nonlinear Analysis at all. Quick Pole is announcing today that it now performs a Level 2 analysis and is committed to reaching Level 4 in the very near future.