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7/28/2019 Composite Tank Final
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COMPOSITE
ELEVATEDWATER TANK
-HARSH SONI
SD1910
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What is a Composite Elevated Tank?
A composite elevated water tank is comprised of a welded
steel tank for watertight containment, a single pedestal
concrete support structure, a foundation, and accessories.
These tanks are also sometimes referred to as concrete
pedestal elevated tanks.
The steel tank provides a proven, watertight container derived
from the AWWA D100 Standard for welded steel tanks which
has demonstrated superior performance through decades of
use by the water industry.
The reinforced concrete support column provides a cost
effective, structurally robust pedestal with minimal
maintenance.
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HISTORY:
Although water storage tanks were constructed fromdifferent tank and tower materials since the early1800s.
the modern composite elevated water storage tankwas initially developed in Canada in the late 1970sand slowly advanced into the US during the last halfof the 1980s.
The first composite elevated water storage tankerected in the US was built in Southlake, Texas in1985.
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History Cntd
More than 600 composite tanks have been
constructed since 1978.
The initial US focus was in the southwestern regions,
but in recent years numerous tanks of this type havebeen constructed in mid-western and eastern
regions of the country.
Now a days, tanks storing 3 million gallons and up to
a height of 230 feet have been erected in the US.
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1978 - 1985
1978-1993
1978-2001
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In all, nearly 450 composite tanks have been
constructed since 1978, storing over million gallonsof water even though there is no AWWA or other
recognized national standard for this structure.
Most of these tanks were constructed according to
manufacturers proprietary designs and job-specificengineers specifications.
In 1992, AWWA and others recognized the need for a
standard and began the development process that isstill ongoing today.
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Spring, 1992 AWWA Standards Council created
Standards Committee D170Composite Tanks for
Water Storage and several associated Subcommittees.
This standard is not yet complete.
May, 1992 Steel Plate Fabricators Association published
a Guideline Specification for Composite Elevated WaterStorage Tanks.
Fall, 1992 American Concrete Institute authorized
development of the Recommended Practice 371R -
Guide for the Analysis, Design, and Construction ofConcrete Pedestal Water Towers which was published in
1998. The scope of this document is limited to the
concrete portion of the structure.
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Construction
Step 1- Foundation
Step 2- Pedestal Wall Construction
Step 3- Tank Erection In Place
Step 4- Completing Tank Step 5 - Interior of Pedestal
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Step 1- Foundation
The foundation is usually a
spread footing for average soilbearing conditions since the
tank footprint is relatively
large although deep
foundations may be requiredin some locations.
It is important that the
foundation and wall starter
rebar be located within
tolerance so the wall
construction can start with the
correct geometry.
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Step 2- Pedestal Wall Construction
From the footing, the wall forms
are erected and the process of
building the wall begins.
The forms typically have Todays
Composite Elevated Storage Tanksstrips fastened to the formwork
that create rustications in the
concrete that hide construction
joints and give a pleasing panel-like appearance.
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care should be taken to ensurewall tolerances on thickness and
plumbness are met.
Additional reinforcement near
openings, block outs for the wall
openings and embedment
installation should bemonitored.
The concrete mix, placement
and vibration should be
implemented in such a way toachieve good consolidation and
minimal surface defects (fins,
bugholes, etc) and shading.
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Step 3- Tank Erection In Place
One popular method of
construction is to construct the
steel tank in-place similar to that
used in welded steel
elevated tanks.
After the pedestal and domeare erected, the subassemblies
of the tank sections are lifted
and fit into position.
Welding, radiographicand tolerance examinations,
and coating work are also done
in final position.
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JACKING:
For this erection method,
supports are erected around
base of the tank and the
conical sections and vertical
shell are fit and welded.
Lifting supports are installedon the tank.
Radiographic and the coating
work may also be completed
while the tank is in lowposition.
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Lifting frames and hydrauliccable jacks are supported on
the top of the pedestal/dome and used to hoist the
tank into final position.
When the tank reaches the
final position, the tank is
pinned in place with
proprietary locking systems
until the final concreteplacement can be made to
permanently lock the tank
and tower together.
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Step 4 -Completing tank
After tank is secured to thepedestal the lifting equipmentis removed and the tank roofand any internals are installed.
The floor liner is installed and,if required, the space betweenthe liner and dome is grouted.
The remainder of accessories,roof handrails andcommunication antennas (ifrequired) are installed.
Coatings are applied to roofand remaining tankcomponents.
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Step 5 Interior of Pedestal
If specified, the interior of thepedestal can be finished for a
variety of uses storage, office
space, training areas and other
imaginative uses.
If the tank is used for
communication antennas, the
interior may be sub-divided toprovide space for the
communication carriers.
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Specifying a Composite Tank
Since no national or AWWA standard exists as yet,specifying a new composite tank is more demanding than atank type with an AWWA Standard.
In the US, the tank builders often perform detailengineering for several of the components based on theirproprietary designs, fabrication techniques and erectionmethods.
Therefore, each tank builder has unique designcharacteristics for their product. Over the past decade,through the development efforts of writing the AWWAStandard for the composite tanks, the major tank buildershave reached consensus on some of the designrequirements but areas of disagreement remain.
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Water-cementitious material ratioThe watercementitiousmaterial ratio should not exceed 0.50.
Specified compressive strength
The minimum specified compressive strength of concrete
should conform to the following:
(a) concrete support structure = 4000 psi (28 MPa);
(b) foundations and intermediate floors = 3500 psi (24
MPa);(c) slabs-on-grade (see Table 5.8.2).
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Dead loadsThe weight (mass) of structuralcomponents
and permanent equipment.
Water load
The load produced by varying waterlevelsranging from empty to overflow level.
Minimum reinforcementReinforcement shouldnot be less
than 0.002 times the gross concrete area in each direction.
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Advantages :
Maintenance
Concrete support structure requires minimal maintenance
Maintenance access to all exterior surfaces is unhindered.
Multi-Purpose Interior Space
Dual use as offices, meeting rooms, pump station, firestation, equipment and machinery storage, etc.
Reinforced concrete support structure
Easily integrates with interior structural steel for multiplefloors
Allows exterior windows
Offset riser pipe maximizes available interior space
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Aesthetic Design
Clean modern appearance
Vertical and horizontal architectural lines blend well with
surrounding structures and landscapes
Economics
Can be economical in larger capacities
Effective cost is reduced when the value of the interior
space is considered
Turnkey supply of foundation and painting offers cost andschedule savings
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References :
Guide for the Analysis, Design, and Construction of
Concrete-Pedestal Water Towers Reported by ACI
Committee 371
Todays Composite Elevated Storage Tanks Stephen W.
Meier, P.E., S.E. Vice President of Engineering and
Technology Tank Industry Consultants Indianapolis, IN
Landmark pvt. Ltd.
www.google.com www.wikipedia.com
http://www.google.com/http://www.wikipedia.com/http://www.wikipedia.com/http://www.google.com/7/28/2019 Composite Tank Final
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THANK YOU