HomeMy WebLinkAboutStructural Certification Letter prepared by Valmont I �"
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February 19,2015
Town of Southhold
Building&Planning Departments
Town of Southold Annex Building
54375 Route 25
Southold,NY 11971
Re: Design and failure modes for a 120-ft Tapered Monopole w/Cell Silo
Quality of Steel and Fabrication of a Monopole Structure
Valmont Quote No.211580-03
Site Location:Mattituck,NY
Pole Designed with a Theoretical Fall Radius of 51-ft
To Whom it May Concern:
As detailed below,the 120 ft multi-carrier disguised monopole proposed by Elite Towers,LP,at the
captioned site,and as depicted in Construction Drawings prepared by Herbst Musciano,Revision 8,dated
91112014,will comply with all applicable federal,state and local structural standards.Valmont,as
manufacturer of the monopole,offers the following in order to assure you of the high quality of all Valmont
products:
Tapered Monopole Design Standards and Failure Modes:
• Communications monopole structures designed by Valmont are sized in accordance with the latest
governing revision of the ANSIOTiA 222,which is a referenced standard for communication structures by
the New York State Building Code, 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 ft's 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. Valmont
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 a greater wind load than the bask:design wind speed because of
these conservative coefficients.
• Design and loading assumptions that are used for the analyses of these structures are very
conservative in nature when compared to other codes,which makes structural failure highly improbable.
• Failure of a steel monopole occurs when a point is reacted 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 budding 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 load. Therefore,wind induced loads could not conceivably bring this type of structure to the
ground due to the excelient ductile properties,design criteria,and failure mode.
• Valmont's communication poles have proven to be very reliable products. Valmont has provided
structures that have performed well during earthquakes In California,hurricanes In the South(including
Page 1 oft Specialty Structures Group,Valmont Industries,Inc.
3575 25'h Strect Salem,OR 97302-1123 USA
Toll Free 800-547-2151 Fax.503-3162040 www valmont.com
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STRUCTURES
Hugo,Andrew,Opal and Katrina),and a number of lomad s. In over 25 years of engineering and
fabricating thousands of monopoles,to our Irnowtedge Valmont has never,experienced an la ser viae
failure of a communication pole due to weather induced overloading,evert lbough,as in the cases of
Hurricanes Hugo,Andrew and Katrina,the wind speeds exceeded tare design wind speed. We use tete
latest standards,wind speed information,and sophisticated analytical tools to ensure ii°aat we maintain
our unblemished record for quality.
Valmont Quality of Steel and Manufacturing:
• Monopoles are fabricated from A Tlwi A57Grade 65 material with a conitrolled siillicon content of 0.06%
maximum to ensure a uniform galvanized coating. Tile baso material is fabricated from Grade fid
material. All plate material meets a V-Notch toughness requirement 0115(bibs°a-20 degrees
Fahrenheit. By meeting the strict roughness requirement.monopoles are best suited to resist the
cyclic tigue type loading(I.e.wind induced loading)these structures exhibit
• Valmont's anchor boas are fabricated from A615 Grade 75 material. The bolts are typically 2%in
diameter,made from#18J bar stock. Anchor boas come complete with five(5)A194 Grade 2H hex
nuts.
• For the past 40 years,our company has always guaranteed the quality of the steel used in building our
structures. Material Certifications are available on afi material at the time of fabrication. Fabrication of
the monopole Is performed in accordance vrith the provisions of the AISC Manual of Steel Construction
and ASCF',s Design of Steel,Transmi"lon,'Pole Structures All welding and inspection is in accordance
With the American MIding Society's Spedfi'cation D1.149lest revision_ Testing and inspection reports
are available upon request at the time of fabrication.
In addition„this monopole can be designed to theoretically fail at approxlmatety the 69-ft elevation by
purposely over designing the pole sections below this point,lin the unlikely event tine pole were to fall at this
point,the significant loading reduction caused by the removal of the toter wlnd area and weight above
would greatly reduce any chance that the remaining tower would have any structural damage,thereby
providing a theoretical failure radius of approximately 51-ft as designed.
I hope these comments address any Issues that you might encountilir relative to the anticipated perfon'na clew
of,the monopole structure and ib quality of steel fatmmcatlon. to consideration of the pararrteters above and
given the fact that the replacement pole Is being located in approximately the same location es the existing
pole(withl'n approximately "),we rewWfuilly request that the Planning hoard waive ttue'fall zone'
requirements of the Code.
If you have additional questions or comments,l may be reached at(503)589.6618.
Sincerely,
01F N EF.
David Casey � ) yf 0
Project Eng wee
FEB
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