Preparing a pattern for supports spotting on the line profile.

It is necessary to prepare a pattern for supports spotting on the line profile.

When the lowest wire АС120/19 is attached at the height of 13.8 m with the clearance to the ground of 6.0 m and 0.5 m reserve on an ideally even surface, the result of mechanical calculation will be the span (overall span) of 232 m. The maximum sag will occur at the given maximum temperature of + 40ºС, not in case of ice accumulation without wind. Otherwise, the supports-spotting pattern should be prepared for ice-without-wind conditions.

The sag of the wire is 7.3 m, the tension in the wire for the given conditions is 3.25 daN/mm2.

The data should be taken eiter from “manual” calculation or from LineMech program by our company.

The equivalent load is 0.00344 daN/m*mm2.

So, the sagging curve of the wire is:

 

Insert the values for and and draw the sagging curve of the wire at the scale of, for instance, 1:500 (5 m in 1 cm) vertically, 1:5000 (50 m in 1 cm) horizontally.

Place the same curve 6.5 m lower, and you will get the so called “clearance” curve. Place one more curve 7.3 m lower, and you will get the “ground” curve.

The distance between the upper and the lower curves at any point will give you the height of attachment for the lowest wire, and the length of the horizontal line drawn at the basis of the middle curve from the left to the right branch of the lowest curve will constitute to the length of the overall span, 232 m.

 

 

When spotting the supports, the “ground” curve denotes the places for supports-spotting in case of touching the “clearance” curve.

For more details, see manuals.

 

After the initial spotting of the supports on the line profile prepared based on the overall span, there is an opportunity to perform the calculation of the equivalent span for each strain sector.

Based on the values for equivalent spans, the supports-spotting patterns are prepared once again and the clearances are checked in regards to the initial spotting of the supports on the line profile.

The sagging curves of the wire at different temperatures could be drawn in the same way, which is useful when making decisions in cases of crossings with engineering objects and natural obstacles, as well as for evaluating the wires positions at lowest temperatures in cases when the middle support is positioned lower than the neighboring ones.

Supports-spotting patterns and sagging curves of wires in AutoCad could be prepared with the help of LineMechCad program by our company.