CONNECTIONS - Prestressed Concrete Transmission Pole Structures - page 51

5
CONNECTIONS
The physical attachment of arms, brackets, insulators, climbing provi-
sions, and other appurtenances to concrete poles is a highly important
consideration to the overall structure design. These attachments, or “con-
nections,” serve the explicit purpose of transferring load to the supporting
pole or frame structure (see example in Fig. 5-1).
Pole line hardware, attachment brackets, and additional appurtenances,
such as in Figs. 5-2 and 5-3, are typically attached to the concrete pole using
bolts placed through holes defi ned in the pole cross section during manu-
facture. However, external bands wrapping the pole—or some forms of
threaded inserts embedded into the pole cross section—have also been
used, depending on the type and magnitude of load. Factors to consider in
connection design include the load transfer mechanism, ductility, durabil-
ity, required pole and bracket fabrication tolerances, aesthetics, constructa-
bility issues, maintenance, and general economics.
Because of the thin shell nature of spun-cast concrete poles and the
important composite material interaction of concrete and steel in concrete
poles in general, connections for concrete poles should be developed by
an engineer experienced in this type of connection details. In some
instances, the pole line hardware supplier may also be able to provide
valuable assistance with typical connection design details, such as those
shown in Figs. 5-4 and 5-5. In either event, the Purchaser's specifi cations
should be clear about who is responsible for design and coordination of
the adequacy of the connections being made to the concrete pole.
The structural adequacy of connections can be determined empirically
through full-scale component testing or by using accepted engineering
modeling or other rational design methods. The connections should be
designed such that the allowable stresses in both the connecting part and
51