Within O-Calc Pro Line Design, users can model a line of poles. This is typically accomplished between dead-end poles, since when the conductors were originally strung, they were tensioned based on the ruling span concept and typically the ruling span is determined between dead-end poles.
Users have the option to perform the pole loading calculations a few different ways. This document describes these methods, how they are accomplished, what the underlying calculations are doing, and the pros/cons for each method.
Disabling the Auto-Solve causes the user to need to click the Ready button to view the % of Allowed MCU results on the currently selected pole. When the user makes any change or selects a different pole within the Line Design the user must manually rerun the calculation using the Ready button, at the user’s discretion.
Users must ‘manually’ run the calculation (click the Ready button) for the selected pole before various features would be available; % of Allowed MCU results in the Capacity meter; reports/charts; auto-guying functionality, etc. When modeling a line of poles, the Single Pole Sweep Wind Calculation can be manually performed in the following ways:
Note: When the Batch Pole Reporting is used for the line design, it is using the Single Pole Sweep Wind Calculation method.
The reader should also recall that for single pole calculations, O-Calc Pro model’s guys dynamically with the far end of the guy (attached at the anchor or stub pole) as a rigid fixed constrain point. This implies that the guy tensions will vary as a function of wind angle. In summary, the Single Pole Sweep Wind Calculation method is as follows:
Note: When performing the calculations in batch reporting mode, the full complement of information is presented as if the single pole report was run on each individual pole.
2. Single Pole Fixed Wind CalculationIn classic O-Calc Pro (V5.03 or early), the Single Pole Fixed Wind Calculation was accomplished by selecting the active Load Case and setting the attribute ‘Override Wind’ to “Yes”. This will enable the attribute ‘Override Wind Angle’ where the user can enter a fixed wind angle. Then when the pole loading calculation is run, instead of sweeping the wind in all directions, the calculation is performed at the single, specified wind direction only.
To perform this Single Pole Fixed Wind Calculation within Line Design, begin with locking the wind direction. This is accomplished using the option in the Line Design tab under Edit -> Lock Wind -> {All Poles, Checked Poles, Current Pole}.
This option will present the ‘Wind Angle Deg’ dialog box that lets the user enter a fixed wind angle value.
When the OK button is selected, the active Load Case for {All Poles, Checked Poles, Current Pole} will be set to Override Wind with a Wind Angle that is specified for the Lock Wind option.
The Single Pole Fixed Wind Calculation can then be manually performed using the same three methods as before, where options a.) and b.) occur for the currently selected pole and option c.) occurs for all poles within the line:
Note, since the user can set the fixed wind directions for each pole individually or via sets of poles, it is incumbent on the user to know which fixed wind angle to use for each pole. Like in classic O-Calc Pro, this method of fixing the wind direction is typically used for either local known prevailing wind directions or for testing purposes.
To reset all the Load Cases back to wind sweep mode, use the option within the Line Design tab called Edit -> Lock Wind -> Un-Lock All Wind.
The Single Pole Fixed Wind Calculation can be summarized as:
There are a few significant differences between the Single pole and Line Design calculations. When performing a fixed wind or sweep wind calculation in Line Design the connected spans or span guys will transfer some of the load to a neighboring pole. How this transfer of load is accomplished needs to be explained in more detail.
The diagram below depicts a simple 2-pole segment of a line design. The two poles have a single span connected between the tips of the poles (depicted as a red catenary curve) and a single span head guy connected between the poles halfway up (depicted as a black straight line).
The bottom diagram is a schematic view depicting the key elements used in the Finite Element Analysis (FEA) when performing the calculations on the full line design. During the FEA calculations the poles are modeled as a series of truncated conic sections, or frustums. The span head guy is modeled as a beam in tension only mode using the physical properties of the span head guy. The span is modeled as load only based on their weight, tension, and elastic parameters as well as the ice and wind loading as required. The spans do not transfer load between the poles via the insulator and/or crossarms.
O-Calc Pro will then apply the full FEA calculations as one composite entity using this model and determines how the composite entity reacts to each wind direction specified by the user. The user has two options: pick a single wind direction or a series of wind directions using a specified increment and a specified start/end wind direction.
a. To perform a Full Line Design in Fixed Wind Mode calculation, within the Line Design tab, select the option Calculate -> Line Analysis -> Entire Line -> Fixed Wind. O-Calc Pro will display the ‘Solver Parameter’ dialog that allows the user to pick a fixed wind angle value.
b. To perform a Full Line Design in Sweep Wind Mode, within the Line Design tab, select the option Calculate -> Entire Line -> Sweep Wind.
c. O-Calc Pro will display the ‘Solver Parameter’ dialog that allows the user to pick the following sweep wind angle and increment values:
In both cases, O-Calc Pro will present to the user with a summary capacity utilization report for each structure and each guy within Line Design grouped by the specified sweep angles, as depicted below. This summary report is used to help the user determine where loading issues may be occurring within the line design; to help focus the user on the potential problem poles based on the loading.
The Line Design with Dynamic Guy Tension Calculation can be summarized with the following bullet points:
4. Line Design Calculation in Fixed/Sweep Wind Mode (Static Guy Tension)
When the wind is swept at various incremental angles, the tensions in the various guys will change with each wind direction. Users have the option to fix the tensions of the guys based on one set wind angle.
In Line Design go to Edit -> Freeze Guys -> Freeze Span/Head Guys -> {All Poles, Checked Poles, Current Pole}
Picking one of these options O-Calc Pro will display the ‘Wind Angle Deg’ dialog that will enable the user to enter a wind angle.
When this option is selected, the Line Design in Fixed Wind Mode calculation will be executed to determine the necessary guy tension values. Each of the guys will be set to ‘Manual Tension’ mode and the tension will be set based on, the Line Design in Fixed Wind Mode calculation.
The Line Design with Static Guy Tension Calculation can be summarized with the following bullet points: