CONNECTIONS - Prestressed Concrete Transmission Pole Structures - page 64

Concrete Bearing Failure
Concrete bearing failure occurs when the bearing capacity of the pole
wall is exceeded, resulting in a collapsing or crushing of the pole wall.
Bolt Shear or Tension Failure
Bolt failure occurs when the allowable shear or tensile capacity of the
bolt is exceeded. Bolt selection should be based on the applied shear and
tension loads and any combination thereof. Allowable loads are to be
determined from the latest edition of the AISC Steel Construction Manual ,
where applicable.
In most cases, bolts will be subjected to a combination of shear and
tension loads. AISC has specifi c methods to design for this condition.
Careful attention should be given to whether or not bolt threads can be
located within the shear plane.
Bolt Bearing Failure
Bearing failure occurs when the load applied to the bolt by the concrete
pole or appurtenance exceeds the bearing capacity of the bolt. This results
in deformation of the threads and possibly the shaft of the bolt itself.
The bearing stress can be calculated as the force on the bolt divided by
the product of the bolt diameter times the thickness of the connected part.
This calculated stress should not exceed 1.5 times the specifi ed minimum
tensile strength F u of the connected part or bolt. Generally, for concrete
poles, other failures likely will occur before a bolt bearing failure (see
Figs. 5-17 and 5-18).
Bolts Subject to Combined Shear and Tension
For bolts subject to combined shear and tension, refer to the appropri-
ate sections of AISC (2005).
Bolt Bending or Prying Action
When designing a connection, special consideration should be given to
the possibility of bending of the bolt and/or prying action, which can
result in bolt failure.
Appurtenance Connection Failures
The engineer should be aware of failures that can occur in the base of
the appurtenance where it connects to the pole. Shear or tear-out failures
as shown are the most common forms of failure (see Figs. 5-19 and 5-20).