HomeMy WebLinkAboutStructural Report Letter ua eC s
sr°uDraj engineers
September 22,2023
Town of Southhold
Building&Planning Departments
Town of Southhold Annex Building
54375 Route 25
Southhold,NY 11971
Re: Design and failure modes for a 150-Ft.Slimline Pole
(Pole Designed with a Theoretical Fall Radius of 72'-0")
.,�..�.�...._�.. µ..,..__. —µM Site Name: Albertson Marine/Southhold 4
2023 Property Address: Budd's Pond Marina,Inc.
61405 Main Road
u � ) fwnSouthold,NY 11971
Planning Board
C&C Project No: T230140029.1.022
To Whom it May Concern:
As detailed below,the 150-ft multi-carrier slimline pole designed by Carpenter&Cross—Structural Engineers
and fabricated by AIIFasteners at the captioned site,and as depicted in the Preliminary Design prepared by
Carpenter&Cross—Structural Engineers(Project Number T230140029.2.026 dated 9/21/2023),will comply
with all applicable federal,state,and local structural standards. Final Construction Drawings will be provided
at a later date.
o le—Dolen StandardA and Failur MOOSE
• This slimline pole structure was designed in accordance with the latest revision of the ANSI/TIA 222
Structural Standard for Antenna Supporting Structures, Antennas and Small Wind Turbine Support
Structures unless otherwise requested by our customer.This standard has been approved by ANSI/ASCE,
which has dealt with the design of antenna support structures for over 40 years.The TIA standard,based
on provisions of this nationally known specification,has a long history of reliability.At its core philosophy
is its first and foremost priority to safeguard and maintain the health and welfare of the public.
• The TIA standard designates a minimum wind loading for each county in the United States.Carpenter&
Cross uses the wind loading listed in the TIA standard unless a greater value is specified by our customer.
Structures are also designed for radial ice at a code-specified reduced design wind loading. Code
designated coefficients are used to ensure that the structure will survive the designed wind speed.The
structure can usually survive even greater wind loads than the basic design wind speed because of these
conservative coefficients.
• Failure of a steel monopole occurs when a point is reached where the induced stresses exceed the yield
strength of the material.At this point,the deflections induced in the material are no longer temporary.
Hence,a permanent deflection in the monopole would exist.
The term failure above refers to local buckling at a designated point on the pole.Local buckling does not
cause a free-falling pole; rather it relieves the stresses from the pole at this location. Monopoles are
flexible,forgiving structures,which are not generally susceptible to damage by impact loads such as wind
gust or earthquake shocks.
When local buckling occurs,a relatively small portion of the shaft distorts and"kinks"the steel.When the
pole begins to bend,the exposure area is reduced and,therefore,the force due to wind is decreased as
well. Even though buckling exists,the cross section of the pole is capable of carrying the entire vertical
5650 Blazer Parkway,Dublin,Ohio 43017
T 614 289-2977 www.CarpenterandCross.com Fall Zone Letter
T230140029.1.022-Albertson Marine/Southhold 4-150 Slimline Pole
September 22,2023
Page 2
load.Therefore,wind induced loads would not conceivably bring this type of structure to the ground due
to the excellent ductile properties,design criteria,and failure mode.
In addition, the monopole can be designed to theoretically fail at the 78' elevation by purposely over
designing the pole sections below this point. In the unlikely event the pole was to fail at this point, the
significant loading reduction caused by the removal of the tower wind area and weight above would greatly
reduce any chance that the remaining tower would collapse,thereby providing a theoretical failure radius
of approximately 72'-0"for the 150-ft AGL slimline pole.
We are aware of Southold Town Code section 280-70G, which generally requires a "fall zone" of an area
surrounding the proposed antenna support structure by two times the height of the structure.However,we
submit that the Town allow the smaller fall zone as stated in this letter.
Monopole Coordinates: 41°4'33.69"N,721 24'21.72"W
I hope these comments address any issues that you might encounter relative to the anticipated performance
of monopole structures and quality of steel fabrication.If you have additional questions or comments,I may
be reached at(614)289.2977.
Sincerely,
Christopher M.Cullinan,P.E.
fCarpenter&Cross LLC
CCullinan@CarpenterandCross.com
9/22/2023
5650 Blazer Parkway,Dublin,Ohio 43017
T 614289-2977 W28yX&W=, C=UdCEMU= Fall Zone Letter