WA9302-SP 961017 (3)
5,000,000 Gallons Naples, FL
Cover:
5,000,000
Gallons
Cartersville,
Georgia
2,000,000 Gallons Ft. Myers, FL
, F
500,000 Gallons Jefferson City, TN
ADVANTAGES
Prestressed concrete tanks
mean lower total cost, minimum
maintenance and dependable
service over the life of your
system.
In the past thirty years, thousands of pre-
stressed concrete tanks have been constructed
and are now providing useful service. These types
of tanks encompass the areas of water storage,
water treatment, process, fuel storage, bulk stor-
age, and containment structures. During this peri-
od of time and with years of experience, pre-
stressed tanks have become a proven product.
Low initial cost and low maintenance costs
have led to prestressed tanks being recognized
as the paramount means of water storage.
There are two primary factors contributing
to the success of prestressed tanks. The first is
the steel shell diaphragm that is in the heart of
the wall, making the wall impermeable. The
second is the bonded prestressing which main-
tains permanent compression in the entire con-
crete wall. Shotcrete, fully encasing the pre-
stress wire, bonds it to the wall and prevents
corrosion.
These successful tanks have been con-
structed by specialty contractors responsible
for the entire tank construction. By combining
updated theoretical design with empirical con-
struction techniques, the specialty tank con-
tractors have perfected the art of prestressed
tank construction.
Low Initial Cost- The initial cost of pre-
stressed reservoirs is competitive with alternate
means of construction.
Low Maintenance Cost- The histori-
cal maintenance cost differential between pre-
stressed and steel tanks makes a prestressed
tank the more cost-effective tank.
Long Life - The construction materials: con-
crete, shotcrete, resteel and prestressing steel are
known for permanence.
Continuous Service- Prestressed
concrete tanks require no interior maintenance;
therefore, they do not require periodic mainte-
nance drawdowns.
Pleasing Appearance- Smooth lines
give prestressed tanks an attractive appearance.
Quality Construction - Prestressed
concrete tanks are built by specialists in the field
who have the specialized knowledge, equipment
and crews with a proven track record which
assures quality construction.
Wide Acceptance - over 1,00o pre-
stressed tanks have been constructed in the
Southeast for industry and municipal utilities.
Watertight - Prestressed tanks are con-
structed with a diaphragm in the wall which is
placed in ring compression, guaranteed to be
watertight.
Versatile - Prestressed tanks are custom
built in the field and they readily adapt to a wide
variety of applications and configurations.
Local Economic Impact - The con-
struction of prestressed tanks takes place on-site
utilizing local labor and materials for most of the
construction.
3
RESERVOIRS
2,000,000 Gallons
::". .'.:.'::/:'!:~":~
...........
5,000,000 Gallons
5,000,000 Gallons
4
400,000 Gallons
500,000 Gallons
WASTEWATER
Digesters
Effluent Storage
Clarifier
Clarifiers
Chlorine Contact
Digester
5
RESERVOIR COMPONENTS
OVERFLOW
PRESTRESSED -.m-..
WALL
MANHOLE. e,. -
,,,,,.,-VENTILATOR PRESTRESSED
a~ /DOME ROOF
/ACCESS HATCH
~'~,,',e-LADDERS
DIAMETER
/.,REINFORCED FLOOR
The components which make up the reservoir are:
FLOOR - A highly reinforced, membrane concrete
slab that has proven to be watertight. The floor
design lends well to withstanding differential set-
tlement.
WALL - A prestressed cylinder which is construct-
ed watertight. The wall will accept significant differ-
ential settlement and varying backfills.
ROOF - A prestressed spherical shell which is
freespan and supported by the wall without interior
columns. The low rise allows safe and easy
access to the entire dome roof.
DIMENSIONS - The tank is field-fabricated with
the diameter and water depth tailored to meet the
job requirements. (A table of typical dimensions is
shown on Page 18.)
ACCESSORIES - Normal tank accessories are
shown on the above diagram, all of which are con-
structed of low maintenance materials known for
their endurance and longevity.
LADDERS - Aluminum interior and exterior lad-
ders allow safe access to the roof and tank interi-
or. Cages and safety climbing devices are incor-
porated as required.
ROOF HATCH - A hatch with an aluminum or
fiberglass lockable cover for easy access to the
tank interior.
VENTILATOR - Fiberglass ventilator allows ade-
quate ventilation and air displacement.
OVERFLOW - Properly sized concrete overflows
provide added ventilation while ensuring that the
tank is not overfilled.
MANHOLE - Galvanized steel manhole allows
easy access when the tank is empty.
PAINTING - Exterior masonry paint is available
for beautification, if desired. Interior coating can
be applied where required.
6
WALL COMPONENTS
~RCING STEEL
~ . SHOTCRETE
PRESTRESSING
WIRE "~. / DIAPHRAGM
COAT
SHOTCRETE
.-_,
-,
The components that make up the prestressed tank wall are:
COREWALL - The portion of the wall that is
placed in compression when the prestressing is
applied.
SHOTCRETE - A dense, durable, rich concrete
mixture composed of cement, aggregate, and
admixtures.
REINFORCING STEEL - Steel bars that with-
stand bending moments and shrinkage forces.
PRESTRESSING WIRE - A high strength steel
wire applied continuously under full load to assure
uniform stress in the wall. The tensile stress in the
wire can be measured at any point.
DIAPHRAGM - A steel barrier that functions as a
4~lFcontinuous waterstop throughout the wall and as
steel reinforcing. The dovetail corrugations
mechanically bond both sides of the wall.
COVER COAT - A shotcrete cover placed over
the prestress wire to protect the wire against cor-
rosion. The cover coat totally encases the wire
and continuously bonds it to the corewall.
FLOOR CONSTRUCTION
The floor of the prestressed tank is typically constructed
as a reinforced concrete membrane slab. The floor, acting as a
membrane, transmits the hydrostatic load of the contents
directly to the supporting soil.
The essential elements of a watertight membrane floor
slab are: high percentage of reinforcing steel, positive thick-
ness control of the slab, quality control of concrete, proper
positioning of reinforcing steel, and adequate curing.
The high percentage of reinforcing steel in a membrane
slab is for crack control. The positive thickness is maintained
by vibratory screeding. Admixtures aid in achieving adequate
concrete strength with moderate slumps. Bolsters assure the
accurate positioning of the rebar within the slab. Adequate cur-
ing is achieved either by a membrane or by flooding with water.
In addition to creating a watertight slab, these require-
ments provide a concrete slab which is flexible and will accept
significant differential settlements.
CONCRETE:
ASTM C-94 3,500 psi, 28-day compressive strength
Slump: 3 to 5 inches
REINFORCING BARS:
ASTM A-615 Grade 40
Minimum lap 24 bar diameters
26 GA. STEEL SHELL DIAPHRAGM
WALL
PRESTRESS WIRES '-'---'--'-~/~---r-':~
~ i I_= ,.s,DE vERT. RESTEEL:
OUTSIDE FACE VERT. RESTEEL. ' i" ~" -'~
·
' 3 - #4
!..,--
;
..
4"
". ......·
~, · ...... ~4AT12"O.CE ~4 AT10" O.C. EA.'
, ' - " RADIUSe
" RADIUS
t
FLOOR - WALL JOINT DETAIL
8
COREWALL CONSTRUCTION
The corewall is the tank wall which has been constructed to the point
where it is ready for prestressing. It is that part of the wall that is placed in
compression by the prestressing steel. The corewall is composed of a steel
diaphragm, shotcrete, concrete, and reinforcing steel bars.
The diaphragm is a metal liner which is located in the heart of the pre-
stressed tank wall. The diaphragm acts as a water barrier for the wall and
as reinforcing steel for the wall. The diaphragm is composed of panels of
formed metal with abutting edges that are sealed watertight. The diaphragm
runs the height and the circumference of the tank wall.
The diaphragm panels are placed against formwork which has been
custom-fabricated to the height and curvature of the tank wall. A special fas-
tening system is used to support the diaphragm against the formwork with-
out causing penetrations in the metal.
The diaphragm panels are formed so that dovetails are placed vertically.
These dovetails mechanically lock the shotcrete, which will be placed on
the exterior portion of the diaphragm, with the shotcrete which will be placed
on the interior portion of the diaphragm.
In order for the diaphragm to be watertight, the edges of the panels
must be sealed in a positive manner. There are several methods of sealing
the abutting edges in a watertight manner. It is important that one of the
proven methods be used.
Reinforcing bars are placed in the wall, as required by design, for
shrinkage, temperature, and bending stresses.
Shotcrete is applied to the exterior of the diaphragm encasing the rein-
forcing steel to build up the wall to its required design thickness.
After the wall formwork has been removed, the interior portion of the
wall receives a shotcrete layer. This layer is also part of the required design
thickness of the wall and acts as a coating to protect the diaphragm against
corrosion. A soft broom finish is applied to the final layer of shotcrete on the
inside surface of the wall.
SHOTCRETE:
ACI-506 4,000 psi, 28-day compressive strength
Cement: aggregate ratio equal to 0.33 minimum for prestress wire
STEEL DIAPHRAGM:
ASTM A-366 (Black) or ASTM A-525 (Galvanized)
Minimum thickness equal to 26 gauge
10
:/
11
DOME ROOF CONSTRUCTION
The dome roof is a free span spherical shell that is
supported along its edge by circumferential prestressing.
The dome roof generally is tied integrally to the tank wall.
The dome is constructed of reinforced concrete with a
typical rise of one-tenth of the tank diameter. Domes with
both higher and lower rises are also periodically construct-
ed to meet project requirements.
The dome roof has no interior columns or supporting
beams.
A soft broom finish is applied to the dome surface.
The broom finish and low profile allow access to all por-
tions of the dome roof.
CONCRETE:
ASTM C-94 3,500 psi, 28-day compressive strength
Slump: 3 to 5 inches
REINFORCING BARS:
ASTM A-615 Grade 40
Minimum lap 24 bar diameters
WELDED WIRE FABRIC:
ASTM A-185
3" CONCRETE AT 6' - 0" FROM WALL
4 X 4 4/4 WIRE MESH . .
FIELD BEND O,UTSIDE V,,ERTICAL RESTEEL
DIAPHRAGM F .f.L I ' ~ .r__._ 4 #4
SPRINGLINE
I,."'.,...,.,~
_1.
i
OUTSIDE VERTICAL RESTEEL:
STEEL DIAPHRAGM
CORE WALL + COVERCOAT OVER
DOME RING DETAIL
12
PRESTRESSING
The tank wall and ring supporting the dome
roof are typically prestressed by continuously
wrapping a high strength steel wire under ten-
sion. This places the tank wall and dome roof in
permanent ring compression. Sufficient pre-
stressing is applied to maintain compression in
the wall when the tank is fully loaded.
The tension in each wrap of prestressing
wire is accurately measured and recorded. Plac-
ing the wire onto the tank under tension ensures
a continuous and uniform prestress force. The
use of a prestressing wire permits the measure-
ment of the actual, in-place tension of each
strand.
PRESTRESSING STEEL: ASTM A-648 Class II
Minimum wire size diameter 0.162" (8 gauge)
PRESTRESSING STEEL
TANK WALL
14
15
COVERCOAT AND ACCESSORIES
A shotcrete covercoat is applied over the
prestressed wires to permanently bond the wires
to the tank wall to protect the wire against corro-
sion and mechanical attack. A one-inch-thick
covercoat is sufficient to provide this protection.
The final layer of shotcrete in the covercoat
receives a soft broom finish which gives a pleas-
ing appearance.
If desired, the exterior of the tank can be
painted.
The materials used in the construction of
prestressed tank accessories are corrosive-resis-
tant materials, such as fiberglass, aluminum,
stainless steel, and galvanized steel.
AVAILABLE ACCESSORIES: [] Roof hatch for access to tank interior
~ Roof vent
~ Exterior wall ladder
~ Interior wall ladder
[~ Roof overflow - vents
[~ Manhole through wall to floor of tank
~ Inlet/outlet piping
E~ Drain piping
[~ Overflow piping
[] Piping vortex breaker
[~ Cage for exterior ladder
[] Liquid level indicator - visual gauge board
[] Handrail around roof hatch
E~ Water level sensing openings
E~ Interior baffle wall
~ Natural draft aerator
16
17
RESERVOIR CAPACITIES AND DIMENSIONS
TYPICAL DIMENSIONS:
Inside Capacity in Millions of Gallons
Diameter
in Feet .1 ,25 ,4 .5 .75
30 18'11"
35 13'11"
40 10' 8" 26' 7"
45 8' 5" 21'0"
50 17'0" 27'3"
55 ' 14'1" 22'6"
1.0 1.5 2.0 3.0 4.0 5.0 6.0
28' 2"
Liquid Depth
60 ~ 11'10": 18'11" 23'8" 35'5"
65 16'1" 20'2" 30'3"
70 j 13'11" 17'4" 26'1" 34'9"
75 12'1" 15'2" 22'8" 30'3"
80 13'4" 19'11" 26'7" 39'11"
85 11'9" 17'8" 23'7" 35'4"
90 15'9" 21'0" 31'6"
95 14'2" 18'10" 28'3"
100 12'8" 17'0" 25'6"
105
110
115
120
125
130
135
140
145
150
155
160
Bold figures indicate most
economical dimensions.
Formula for Volume: V=5.875 D2H
'Where V = Volume in Gallons
D = Inside Diameter in Feet
H = Liquid Depth in Feet
165
170
175
180
37' 9"
34'0" ~
15' 5" 23' 2" 30'10",
,;:
28' 0" 37' 4"
26' 1" 34' 9"
24' 3" 32' 5"
30' 3"
28' 4"
26LT'
25' 0"
40' 6"
37'10"
35'5" 42'6"
33!3" 39'10"
31'3" 37'6
29'5" 35'4"
27'9" 33'4"
31'6"
I
18
500,000 Gallons Daytona Beach, FL
5,000,000 Gallons Naples, FL
1,000,000 Gallons Cumming, GA
Back cover:
100,000
Gallons
Inglis,
Florida
..... ~EW TEXAS OFFICE:
Laurence Gossett, Ph.D.
PRECON CORP
~07 W. Seventh St., Suite
Fort Worth, TX 76102
(817) 335-6905
1800
PRECON CORPORATION
115 S.W. 140TH TERRACE
NEWBERRY, FLORIDA 32669
(904) 332-1200 FAX 332-1199