Method of erecting an elevated tank using formwork

A tank is constructed and formwork apparatus is attached to that formed tank. The formwork apparatus is used to construct a tank supporting wall and jacking mechanisms included in that formwork apparatus lift the tank as the support wall is being formed so that the tank is carried upwardly by and on the supporting wall as that wall is constructed. The formwork is preferably slipforms.

BACKGROUND OF THE INVENTION 
The present invention relates, in general, to elevated tanks and, more 
particularly, to methods of constructing elevated tanks. 
In slipforming, the forms are 3 to 4 feet high, and move upwardly at about 
one foot per hour either continuously or intermittently continuously. In 
the latter case, the crew may work on only one shift per day because of 
economics, or restrictions on noise, or lack of trained people for more 
than one shift. 
In any case, the concrete being exposed at the bottom edge of the form is 
stiff and of low but sufficient strength to carry the loads applied 
thereto. 
In jumpforming, the same type forms are used, but may be of a greater 
height and increased strength. The forms are positioned and filled with 
concrete. The concrete is allowed to set for hours or days until 
sufficiently strong, and then moved upward and the next portion cast. This 
process is not of a continuous nature, but intermittent. One jumps the 
forms upwardly between pours using jacks, or the like, similar to those 
used in slipforming. 
In the present disclosure, terms such as "forming", "formwork", and the 
like, will be used to include both slipforming and jumpforming. A specific 
embodiment using slipforming will be presented, but it is to be noted that 
such embodiment is not intended as a limitation, but is an example only. 
Slipforming concrete walls is a well known construction technique. 
Basically, slipforming comprises positioning a formwork, pouring concrete 
into the formwork, and then, while the concrete is setting, moving the 
same formwork upwardly to pour freshly mixed concrete on top of the first 
concrete. This procedure is repeated until the desired height is attained. 
The repetition may be continuous from start to finish or intermittently 
continuous such as may be accomplished during day shifts only. Known 
slip-forming apparatus uses a self-climbing formwork, and reinforcing 
steel is placed as the forms move upwardly. This technique has been 
successfully utilized in construction of buildings, water towers, bridge 
piers, chimneys, and the like. 
Methods of constructing elevated structures are disclosed in U.S. Pat. Nos. 
3,201,502, 3,805,369, 4,197,689, 3,092,216, 3,073,018; and U.S. Pat. No. 
4,206,162 discloses a method of constructing concrete enclosures using a 
bottomless form. 
All of the known methods of erecting elevated tanks either require the 
completed tank or the completed parts of the tank to be hoisted onto a 
completed supporting wall, thereby requiring heavy hoisting equipment, or 
requiring hoisting jacks to lift the completed tank plus the completed 
portions of the support wall, thereby again requiring heavy lifting 
equipment strong enough to support and lift the entire completed assembly. 
Also, it is advantageous from a safety and efficiency viewpoint to assemble 
as much of the structure as close to the ground as possible. In such a 
case, the structure is fully assembled at or near ground level where 
access is easier and subsequent concrete placement is done from 
substantial platforms attached to the slipforms. 
Thus, there is need for a method of erecting elevated tanks which does not 
require the use of extremely heavy hoisting equipment, and which utilizes 
manpower as close to the ground as is practically feasible. 
SUMMARY OF THE INVENTION 
The method embodying the teachings of the present invention utilizes 
formwork in the erection of elevated tanks, and does not require use of 
extremely heavy hoisting and/or jacking equipment. 
In the disclosed method, the forming apparatus is used as the jacking means 
for moving a tank to a prescribed position. In other words, in the 
invention disclosed herein, the jacking mechanism of the form apparatus is 
used to elevate a completed tank concurrently with the forming. 
In the method according to the teaching of the present invention, a tank 
will be erected on a foundation using blocking at the center and falsework 
around the perimeter. A steel fluted skirt in a preferred embodiment will 
be erected in place. In the preferred embodiment, when tank erection is 
complete, a slipforming crew sets up a form under the steel skirt. Yokes 
are attached rigidly to a base plate of the skirt, and possibly to the 
skirt itself, then cross braced to the tank bottom. Steel forms can be 
used, although wood forms can be adequate. Approximately forty small jacks 
are required in a preferred embodiment of the disclosed method. The jack 
rods of these jacks are restrained from buckling by a pipe collar located 
at the yoke and surrounding the jack rod, and holes are drilled in the 
skirt base plate. Vertical reinforcement bars may also be held in place by 
the skirt base plate. The latter base plate acts as a template for 
positioning the jack rods and any vertical reinforcement or anchors. As 
such it has holes drilled therein to properly locate such elements. 
The main advantage of the forming method embodying the teachings of the 
present invention is that the tank can be fabricated at ground level. 
Typically, the metal tank will be constructed with the bottom thereof 
blocked just slightly above foundation level. Another advantage of the 
method embodying the teachings of the present invention is that only a 
limited amount of equipment and a small crew have to be transported to the 
tank erection site. Still other advantages of the disclosed method include 
the formwork platform, which provides an ideal work deck for installing 
ladders, blockouts, and painting. The blockouts may be left in the wall to 
act as supports for subsequent flooring members. 
OBJECTS OF THE INVENTION 
It is a main object of the present invention to erect an elevated tank 
without requiring use of heavy hoisting and/or lifting equipment. 
It is another object of the present invention to erect an elevated tank 
using the form jack mechanism as the means of elevating the tank. 
It is yet another object of the present invention to reduce the cost and 
increase the safety of elevated tank construction by building the tank as 
near the ground as is feasible. 
These together with other objects and advantages which will become 
subsequently apparent reside in the details of construction and operation 
as more fully hereinafter described and claimed, reference being had to 
the accompanying drawings forming part hereof, wherein like reference 
numerals refer to like parts throughout.

DETAILED DESCRIPTION OF THE INVENTION 
Schematically shown in FIGS. 4-8 is a method of erecting an elevated tank 
according to the teaching of the present disclosure. FIG. 1 shows 
equipment used in practicing the invention, and FIGS. 9 and 10 show an 
alternative form of the method. 
As discussed above, the essence of the invention is the elevation of a 
completed tank by formwork methods, and preferably slipform methods, with 
the formwork being positioned so that only the tank need be raised by 
mechanical means, such as jacks, or the like, which jacks are included 
with the formwork apparatus. The ensuing disclosure will clarify this 
invention. 
Adverting first to FIG. 1, it is seen that the preferred equipment used to 
raise a completed tank T includes a slipform 10 movably mounted on a wall 
12 at or near the top rim 14 thereof. As will be evident from the ensuing 
discussion, wall top rim 14 moves upwardly as the wall 12 is constructed. 
The slipform 10 includes sheeting 20 and 22 contacting inner surface 24 and 
outer surface 26, respectively, of the wall 12. Wales 30 and bracing 32 
reinforce the sheeting and transmit lifting forces in the manner usual to 
slipforms. As shown in FIG. 1, sheeting 20 includes an upper portion 36 
which extends above top rim 14, and sheeting 22 includes a splash board 
forming portion 38. 
A yoke assembly 42 includes a cross member 44 and a pair of frame members 
46 and 48 associated with sheeting 20 and sheeting 22, respectively. The 
frames are attached to the wales and to the cross member to transmit 
forces to the wales and to maintain proper spacing between the sheeting 
members. 
A jack 50 is mounted on the cross member 44, and includes a jacking rod 52 
extending through a support guide tube 54 attached to the cross member 44. 
The jacking rods 52 extends downwardly through the wall 12 and have the 
lowermost terminal ends thereof resting on the ground located footing, or 
the like. Vertical reinforcement bars are located between the jacking 
rods, and both the jacking rods and vertical reinforcement bars are formed 
of a plurality of sections which are placed end-to-end as the wall is 
erected. The jack 50 is suitably powered from a suitable source (not 
shown). The jack can be a screw-type, hydraulic, pneumatic, or the like, 
as suitable. There are a plurality of jacks each located in a flute F of 
the tank fluted skirt, as best shown in FIG. 3. The jacks thus create 
stresses which are directed essentially linearly through the jack into the 
support wall as the tank is elevated. The mechanical advantage of such 
stress distribution permits use of jacks which are smaller than those 
required if the tank were lifted using some other distribution of hoisting 
equipment. 
A wheel 60 is supported from the inner frame member 48 via frame extensions 
62 and 64 to contact the wall inner surface 24. The wheel serves to 
transfer lateral forces into the hardened concrete of the wall. The wheel 
transfers laterally directed wind forces into the wall. 
Cross bracing 70 is connected to tank T and to yoke frame member 48. The 
cross bracing distributes forces and supports the slipform in a manner 
known to those skilled in the art. 
Also included is inner platform 80, outer platform 82 and finishing 
platform 84, all supported from cleats 86 on the tank T via cables 89, 
with platforms 80 and 82 also being attached to the slipform 10. The 
platforms serve purposes usual to this art. The finishing platform 
supports workmen performing the usual finishing operations and is hung in 
place after slipping commences. The finishing platform can be enclosed and 
heated in cold weather, if desired. The inner platform 80 is used for 
placement of the vertical reinforcement bars in the wall. 
It is noted that if extra head room is required at the inside work platform 
(for example, in placement of heavy reinforcement bars for Zone 3 seismic 
loads), the height of the tank skirt can be increased by blocking the tank 
up on a foundation slab. Slipforms may be positioned after tank 
completion. The tank falsework should be self-supporting to avoid damage 
thereto when slipforming commences. 
It is also noted that the work platforms should be integral with the 
slipform during the slipping operation. However, these platforms should be 
detachable so that they can be lowered independently using "window 
washing" type cable jacks. These platforms can then be used to dismantle 
the slipforms at the top of the pedestal and then lowered for dismantling 
at ground level. 
Any suitable means for transporting concrete, reinforcement bars, and the 
like, to the slipform work area can be used. One such means is shown in 
FIG. 1 and includes a monorail assembly 100. The monorail assembly 100 
includes a rail 102 mounted on the tank and a carriage 104 riding in the 
rail 102. Cable 106 includes reaches 108 and 110 and is trained around a 
pulley 112 in the carriage and a pulley 114 mounted on the ground. 
Concrete from a source (not shown) is moved in buckets, or the like, to the 
level of the outside platform. Workmen than decant the concrete into the 
slipform gap 120 formed between the sheeting members. Vertical 
reinforcement bars 122 and horizontal reinforcement bars 124 are embedded 
as suitable. 
As is evident from the above, the slipform and all of the equipment 
associated therewith is affixed to the tank T to move therewith. A 
multiplicity of jacks 50 are placed and spaced circumferentially about the 
tank T and lift that tank as work progresses. As one level of the wall 12 
hardens sufficiently, the tank and attached slipform equipment are raised 
by the jacks 50 so the next wall level can be poured. 
Work progresses until the tank T has been raised to a suitable height. At 
such time a closure pour is performed using a closure form 130 attached to 
upper portion 36 of sheeting 20 shown in phantom lines in FIG. 1 to 
indicate that this closure form is detachably mounted on the sheeting 20 
when the closure pour is to be executed and is not present at other times. 
The tank has a fluted skirt S appended thereto and the jacks 50 are located 
in the flutes on the skirt as shown in FIGS. 1 and 3. The cross members 44 
also support the vertical reinforcement bars and the jacking rods. 
As best shown in FIG. 2, a gap or blockout 144 is left in the closure port 
to allow removal of the yoke means, jack means, the support tube 54, and 
the like. 
As can be seen, the slipform means is affixed to the tank T via the yokes, 
cross braces and platforms, and hence moves with that tank. The tank is 
moved upwardly as the wall is completed, and hence is carried upwardly as 
work progresses. The jacks 50 thus need only lift the tank, slipforms, 
platforms, and the like. The weight of the wall 12 need not be lifted by 
the jacks. 
FIGS. 4-8 illustrate the method of erection disclosed herein. Erection is 
begun by dfining an excavation 160 at a suitable location in groundG and 
forming a footing 162 therein. Falsework 166, anchor bolts and the like 
are mounted in the footing as shown in FIG. 4. Suitable bracing and the 
like is also erected. The anchor bolts 70 temporarily hold the tank, and 
tierods or the like for the concrete wall are also cast in place in the 
footing. 
The tank T is then formed on the falsework as shown in FIG. 5, and has 
suitable compression rings 168 thereon. The tank is complete except for 
the bottom which will be formed on the ground and lifted into place after 
the tank has been elevated to the desired height. Bracing and the like is 
attached to the tank. 
The slipforms, jacks and other associated equipment are then attached to 
the bracing and to the tank and to the falsework. Concrete is then poured 
into the slipform and tank elevation above the FIG. 5 level commences. 
Concrete can be conducted to the tank site via a wet application system WS 
as shown in FIG. 7, or by other suitable means, such as the 
above-discussed monorail assembly 100, or the like. Tank movement is 
indicated in FIG. 7 by arrow TM. The platforms are also suitably attached 
to the tank. 
The tank is superincumbent the upper rim of the wall 12 as that wall is 
built upwardly as above discussed and is progressively elevated upwardly 
until the desired height thereof is reached. Such desired height is shown 
in FIG. 8. Tank bottom 170 is formed and then hoisted into position and 
suitably attached to the tank. Finish work and closure pours are performed 
as suitable and as will be known to those skilled in the art from this 
disclosure. Permanent tank anchor means are also installed at this point. 
The tank is then lowered onto the permanent anchor means, the slipforms are 
removed where suitable, the tank base plate is grouted to the wall and the 
concrete surface is finished as necessary. Piping, and like equipment, is 
then installed. It is noted that the slipform equipment located inside the 
wall may be left in place, if suitable. 
An alternative method of carrying out the erection method disclosed herein 
is illustrated in FIGS. 9 and 10. In the alternative method, a tank 
compression ring is modified and the slipform 10 is attached thereto in 
place of the tank skirt shown in the above-disclosed embodiment. The top 
edge of the slipform is welded to the tank. 
As best shown in FIG. 10, the tank has an annular opening H defined 
therein. Annular reinforcement plates P1 and P2 are located on the tank 
along the edges of the opening. Closure plates CP cover the hole H, after 
slipforming. A reinforcement template TR is mounted on the tank wall and 
reinforcement plates, and the jack rod 52 is received through the opening 
in the reinforcement template. A jack 50 is mounted on the template TR. 
Pouring during the slipforming is accomplished from inside the tank through 
the opening H with the closure plate removed. Once the wall is completed, 
the closure plate is welded in place, the jack is removed and the 
reinforcement template is dismantled. Of particular interest here is that 
the skirt disclosed above is replaced by the slipform and concrete pouring 
is initiated from inside the tank. 
Preferably, the slipforms remain in place after the tank has reached the 
desired height. 
A platform 190 is affixed to the tank T to span the bottom of that tank. A 
hoist mechanism 192 is mounted in the tank and concrete is transported in 
a bucket 194 via an access hole 196 in the platform to the tank and then 
to the slipform from inside the tank. 
In the alternative method, the wall is formed to an intermediate height 
before tank construction is begun. However, once the tank is formed, the 
procedure is similar to the procedure described above with reference to 
FIGS. 4-8. 
When the tank has attained the desired height, the yoke means are removed 
and a closure plate is welded in the tank to cover the concrete wall. The 
slipforms, preferably, are left in place and not removed upon completion 
of the FIG. 9 tank erection method. Reinforcement bars as well as concrete 
and other material are hoisted to the work area by the hoist mechanism 
192. 
As this invention may be embodied in several forms without departing from 
the spirit or essential characteristics thereof, the present embodiment 
is, therefore, illustrative and not restrictive, since the scope of the 
invention is defined by the appended claims rather than by the description 
preceding them, and all changes that fall within the metes and bounds of 
the claims or that form their functional as well as conjointly cooperative 
equivalents are, therefore, intended to be embraced by those claims.