Gin Pole Services

The gin pole is unique to the tower industry. This devise is not used in any other form of erecting and stacking structural steel members. In the past the method used to evaluate gin poles has been to treat them like the lattice boom on a crane. While a gin pole may resemble a crane's boom, they are simply not the same device. The stresses and loading are very different and the forces are not related. This is due to large compression forces applied at the top of the vertical gin pole with little or no lateral support at the top, and the ever changing stiffness of the bridle and basket supports. These support conditions change with the stiffness of the tower as it goes up in height.

The gin pole standard was developed over a five year period with special research conducted which included past study of theoretical models of gin pole type structures, along with small scale and large scale gin pole load testing.

Theoretical Models Compared

This mathematical model (below) of a compression member on its side is supported identically to a gin pole bridle and basket arrangement. Text book models like this were used to verify the accuracy of computer analysis models used to develop gin pole buckling factors provided in Chart B-1 of the Gin Pole Standard.

Small scale tubes were supported in a vertical position in a special fixture supported with bridle and basket arrangements, including a mid-level connection between the bridle and basket in some cases. These models were provided with lateral springs to simulate the conditions of the guyed tower supports that move when loading is applied. Then, these tubes were buckled under load with results compared to computer models using methods provided in the Gin Pole Standard.

In the real gin pole situation movement at gin pole supports occurs when the tower moves laterally with the loading of gin pole lift forces. Relationships between the stiffness of the tower and the stiffness of the gin pole were developed in these tested models and verified by calculation procedures. These results were used to develop correct buckling factors added in the standard.

Full Scale
Testing

Full scale gin pole testing was conducted at the ERI (Electronics Research, Inc.) testing facility in Chandler, Indiana. This final testing was used to verify accuracy of procedures specified in the standard for determining the strength of a vertical gin pole under the combination of both moment and compression loading, which represents actual gin pole loading conditions.

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Glogal Engineering Documents

Cover Page of the TIA 1019-Gin Poles Standard: