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/


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THANK YOU

Date post:	03-Apr-2018
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Composite Tank Final

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