Filled with concrete, a nail keg counterbalanced the rooftop crane

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Commentary by Neil A. Lieb, with photo from his archive

See the little cornice atop the tank? Those are forms for the cornice, the overhang. They call them eaves on a house.

The roof was poured before the headhouse went up.

That crane is a concrete-hoisting crane.

The headhouse is quite an operation because you had to hoist the concrete up to the top of the tank. And then they had a deck crane, and you had to hoist it [the concrete] to the top.

Every job I worked on, they used a nail keg that had been filled with concrete as a counterbalance weight. When you went up and down on the cable to go to work, that’s what you stood on—two guys, one foot each. That’s all there was room for.

It didn’t take that long, about fifteen or twenty seconds.

The motor and cable were down on the ground.

The operator had a shed to keep him out of the rain and sun.

 

DN Tanks builder explains differences between concrete tanks and elevators

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A water tank built by D N Tanks in Cary, Illinois

Story and photos by Kristen Cart

At first glance, a water storage tank and a grain elevator seem to have a few things in common, both in function and appearance, though they present a number of differing engineering challenges. I had the opportunity to interview Joseph Carroll, a project superintendent for D N Tanks, while flying on a commercial airline to start one of my trips. When he realized the lady sitting next to him had some engineering background, and actually was interested in concrete construction methods, he warmed to his subject with enthusiasm.

I wanted to find out how the construction of a tank answered the problems that grain elevator designs had to address–the management of stress (both vertical and lateral), the aging of the tank, interior access, wrecking out, weather considerations, and basic construction methods.

D N Tanks had been in the business since 1949, and some of their tanks (still in service) were built before 1950. During the heyday of elevator building, when our grandfathers operated at the cutting edge of concrete design, water tank builders were innovating right alongside them. The types of problems they had to solve had common elements with those of elevator designers, but their solutions were widely divergent.

After looking at our Tillotson construction specifications, Mr. Carroll commented that the design bearing load (the pressure of the water against the tank walls, expressed in pounds per square inch) of his tanks is about double the bearing load in a grain elevator.  Elevator builders relied on a continuous concrete pour and steel reinforcement to provide the required strength. Obviously, something had to be done differently to build a water tank that would sustain that kind of load.

D N Tanks, instead, builds tank panels which are poured in curved sections separately, then tensioned externally with wire winding as they are assembled on site.

Cold weather also creates a design challenge for concrete construction. I mentioned that in Canada, wood construction for grain elevators was preferred, because rigid concrete could crack under differential heating–an elevator would experience freezing temperatures on one side and solar heating on the other. Water tanks require insulation to prevent freezing, though they can handle surface freezing to the depth of about six inches. The tank walls are built thicker, and an insulating material of styrofoam blankets the tank exterior for installations in Alaska and other northern locations.

After the concrete roof is poured, wrecking-out is required (internal wooden concrete forms are removed). It is a process required for both elevator bins and tanks. Elevators retain the manholes used to remove the wrecking-out debris for later access to bin bottoms for cleaning. For water tanks, an access opening is left at the side to permit this process, but it is sealed afterwards. No access is needed from the side, because under normal use, the tank remains filled with water. Access to electrical systems for the pumps is from the top.

Concrete elevators are subject to much more wear and tear than water tanks. Internal friction is an issue with grain elevators:  filling and emptying of grain bins abrades the inner concrete surfaces, eventually causing cracking and damage after many years.  Tanks suffer from no such problems.

Fire is an ever present danger in grain elevators, and cleanliness is a constant battle. Tanks tend to be cleaner and safer, and if built correctly from the start, will long outlast the most robust grain elevator.

DSC_9898I happened upon one of these water storage facilities, built by D N Tanks, while attending my son’s football game at Cary Junior High School in northern Illinois. It appeared just as Mr. Carroll described as a typical D N Tank project: it was bordered with a two-foot wide lip, and topped with a white vent.

The tanks are built in cities and towns to comply with a requirement for an emergency water supply. The tank or tanks must hold enough water to last for three days after normal municipal service is lost. Unlike the many grain elevators that dot the Midwest, which rise to monumental heights, these tanks are designed to blend seamlessly into the community with as little visual impact as possible. The D N Tank website pictures a number of disguises, including architectural treatments, and fully underground construction.

D N Tanks also produces tanks for glycol used for aircraft deicing, water treatment tanks, and various other tank types.

Summer 1950: All finished with the main house in Alta, Iowa

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Commentary by Neil A. Lieb and photo from his archive

From a telephone interview on July 22, 2014

It’s all done. It looks like they’re putting scaffolding up for painting. The main hoist is on the left. That’s a Georgia buggy hanging on the hoist. The guy that’s standing there is going to push it as soon as it hits the deck. They might be just starting on the headhouse. I can’t figure that scaffolding out. It’s a rigid scaffolding.

Memories of cranes and pushing the Georgia buggy in Alta, Iowa

The formwork is clearly seen at the Alta elevator rises. The catwalk around the bottom was for the concrete finisher, who smoothed and patched the freshly formed surface. Photo from the Neil A. Lieb Archive.

Commentary by Neil A. Lieb, photo from his archive.

From a telephone interview on July 22, 2014

On the upper left-hand corner, there’s a crane. That crane we used to haul the steel up to the top, the rebar, the jackrods. That’s all we used it for. You didn’t tie up the other hoist, you used that one. I think it’s called a jack crane. It was an electrically operated crane. The railroad tracks are on the bottom, that’s the end of a box car in the lower right. That doorway—that’s used when you’re loading grain after the thing was all over with.

When I first started, I pushed the Georgia buggy.  It’s probably the worst job in the world because it’s very physical. They weighed 1000 pounds. At Alta, I progressed to laying steel. All the new hires always got to push the concrete because that was the hardest work. There was a big turnover when you started out because pushing Georgia buggies wasn’t very much fun.

The Tillotson elevator in Boxholm, Iowa, afforded unique photographic possibilities

DSC_0535Story and photos by Kristen Cart

The Boxholm elevator located in central Iowa was an intriguing destination, particularly since I had knowingly passed it by, missing it by a few miles on more than one trip. It became imperative to make the detour to see it. I was glad I did, since the elevator made beautiful pictures on that early summer day. I used a wide-angle lens that added pronounced distortion to the scene, causing the buildings on the edges to lean in dramatically. But the leaning lines pointed to the beautifully clouded sky.

You can use a wide-angle lens to include more of the scene from close quarters than would be possible with another lens, but you forfeit realism. This is not a problem for certain artistic photos, but it is not ideal for documentary shots. When photographing buildings where you want to preserve parallel lines, you must stand farther away and use a longer focal-length lens. At Boxholm, I did not have that option.

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Wide-angle lens distortion is maximized in this view.

At extremely close quarters, the wide-angle lens exaggerates height and adds drama. But the distortion becomes more pronounced.

The Tillotson Construction Company of Omaha, Neb., built the elevator in 1955. An annex stands beside it, and an old wooden feed mill is beside that. A much newer elevator with the West Central logo was built later, after it became customary to leave the concrete plain, without the white finish.

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A more conventional view of the elevator complex.

The specifications for the Boxholm elevator are among the Tillotson Company construction records. We learned some details about the elevator from a few stray sources before my visit; for instance, the elevator has exactly 96 light bulbs installed. Its construction followed the Drummond plan. Other projects using the same architectural plan were the elevators at Waverly, Neb., and Lahoma and Drummond, Okla.

Specifications

Capacity per plans (with Dock): 199,400 bushels

Capacity per foot of height: 2,002 bushels

Reinforced concrete per plans (total): 1,797 cubic yards

Plain concrete (3″ hoppers): 33 cubic yards

Reinforcing steel per plans (includes jack rods): 85.71 tons

Average steel per cubic yard reinforced concrete: 95.4 pounds

Steel and reinforced concrete itemized per plans:

Below main slab: 6,861 pounds steel, 59.2 cubic yards concrete

Main slab: 25,603 pounds steel, 202 cubic yards concrete

Drawform walls: 103,192 pounds steel, 1,295 cubic yards concrete

Driveway and Work floor : 3,820 pounds steel, 23.8 cubic yards concrete

Deep bin bottoms (including columns): 7,271 pounds steel, 39.3 cubic yards concrete

Overhead Bin bottoms: 6,040 pounds steel, 27.6 cubic yards concrete

Bin roof and Extension Roofs: 7,210 pounds steel, 41.7 cubic yards concrete

Scale floor (or garner complete): 160 pounds steel, 2.5 cubic yards concrete

Cupola walls (including leg & head): 7,257 pounds steel, 76 cubic yards concrete

Distributor floor: 1,560 pound steel, 9.4 cubic yards concrete

Cupola roof: 2,147 pounds steel, 15.6 cubic yards concrete

Misc. (track sink, steps, etc.): 173 pounds steel, 3.5 cubic yards concrete

Attached driveway: none

Bridge and/or Tunnel: none

Pit Liner–plain: 16 cubic yards concrete

Drier Bin Bottom: 134 pounds steel, 1.3 cubic yards concrete

Coffer Dam, Cleaner Floor: Wood

Remarks: 10 Bin Hot spot; 8 Bin Aeration tubes; Dryer bin

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The rounded headhouse is a reliable indicator of a Tillotson elevator

Construction details

Like Waverly: construction details were identical to Waverly and not listed separately in the records.

Main slab dimensions (drive length first dimension): 56 1/2′ x 70′

Main slab area (actual outside on ground): 3,850 square feet

Weight reinforced (total) concrete (4000 pounds per cubic yard plus steel): 3,747 tons

Weight plain concrete (hoppers; 4000 pounds per cubic yard): 98 tons

Weight hopper fill sand (3000 pounds per cubic yard): 732 tons

Weight of grain (at 60 pounds per bushel): 5,982 tons

Weight of structural steel and machinery: 20 tons

Gross weight loaded: 10,579 tons

Bearing pressure: 2.75 tons per square foot

Main slab thickness: 24″ with 3″ pile cap

Main slab steel: straight #9 at 7″ spacing

Tank steel and bottom (round tanks): #4 at 12″ spacing

Lineal feet of drawform walls & extension: 606′

Height of drawform walls: 120′

Pit depth below main slab: 15’3″

Cupola dimensions (outside width x length x height): 22 1/4′ x 48 1/2′ x 35′

Pulley centers: 160.75′

Number of legs: 1

Distributor floor: yes

Track sink: yes

Full basement: yes

Electrical room: yes

Driveway width clear: 13′

Dump grate size: 2 at 9′ x 5′ and 9′ x 15′

Column under tanks size: 16″ square

Boot legs and head: concrete

DSC_0531Machinery details

Boot pulley: 72″ x 14″ x 4 15/16″

Head pulley: 72″ x 14″ x 2 7/16″

R.P.M. Head pulley: 42

Belt: 335′, 14″ 6 ply Calumet

Cups: 12″ x 6″ at 8″ spacing

Head drive: Howell 40 horsepower [4 circled here]

Theoretical leg capacity (cup manufacturers rating): 8,440 bushels per hour

Actual leg capacity (80% of theoretical rating): 6,750 bushels per hour

Horsepower required for leg (based on actual capacity): 32 horsepower

Man lift: 1 1/2 horsepower Ehr.

Load out scale: 25 Bushel

Load out spout: 10″ diameter

Truck lift: 7 1/2 horsepower Ehr.

Dust collector system: Fan to bin

Cupola spouting: 10″ diameter

Driveway doors: 2 overhead rolling

Conveyor: provision

Remarks

see page 10 (above)

Night and day in 1950, Tillotson’s grain elevator rose in Alta, Iowa

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Commentary by Neil A. Lieb, photos from his archive

From a telephone interview on July 22, 2014:

It was commercial power for the lamps. The only thing that was noisy was the mixer and the hoist. Once you got about 40 feet off the ground, all that anybody heard was people talking to each other. That’s the top of the driveway (seen in the photo), about 16 feet, so they’re about 25 or 30 feet off the ground. On a construction site, there’s lumber all over everywhere. Today they keep track of it very carefully because people steal it. But when we were building these, nobody stole lumber. People in Iowa and the Midwest, they didn’t steal lumber from a construction site like they do out here (California.) See the scaffolding below the forms? A cement finisher finished the concrete as it came out of the forms. That’s all he did, all night long.

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Those cars…I didn’t have a car at Alta. Those shacks were probably, lower right, the office, and the other was where we kept the tools. We built a lot of those things and then we tore them down. Slip-form construction was a major engineering feat. They built concrete grain elevators before slip-forms. They had steel forms they’d fill with concrete.

 

 

 

The gun fired, and continuous action of many processes began in Alta, Iowa

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In this post, Charles J. Tillotson elaborates on Neil A. Lieb’s previous comments, describing the above photo from his archive. The jack rods referred to in the text are the tall, slender steel poles seen throughout the photo.  

They often say, a picture is worth a thousand words and this one fits the bill perfectly. The photo is truly an aid to describing the method of slipform construction that was used in grain elevator construction. Neil mentions the one-handed placement of the jack rod, so I’ll start with that.
 
Slipform construction is made up of many complex disciplines which have to all work together in order to provide the final poured-in-place concrete product.

As mentioned prior to this, the slipping of the formwork used in this type of construction was provided by a series of screw jacks placed apart by an engineered calculation sufficient to lift each jack’s portion of the formwork assembly.

Each screw jack was supported by a wooden, U-shaped yoke, the legs of which were attached to the vertical concrete formwork. Inserted in the top (or horizontal) portion of each yoke was a screw jack (similar to that used in jacking building foundations). A smooth one-inch jack rod was then inserted into the top head of the jack and threaded down through it until stopping at the foundation slab. 

The formwork is clearly seen at the Alta elevator rises. The catwalk around the bottom was for the concrete finisher, who smoothed and patched the freshly formed surface. Photo from the Neil A. Lieb Archive.

The wooden formwork is clearly seen at the Alta elevator rises. The scaffolding around the bottom was for the cement finishers, who smoothed and patched the freshly formed surface. Photo from the Neil A. Lieb Archive. 

A series of horizontal wooden rails at about waist height (looks like a railroad track) were then built directly above the open formwork, the “ties” of which were placed at prescribed intervals and used as a template spacer for inserting the actual vertical reinforcing steel. (See the small, half-inch rebar rods extending vertically out of the open bin forms at each cross tie). The vertical rebar was staggered slightly in an alternating fashion so as to allow the half-inch horizontal rebar to be threaded through the vertical rebar. On the vertical 2x4s that are attached to the exterior side of the formwork and rise above the entire deck assembly, so-called targets placed on their tops were used in leveling the deck in order to provide a final elevator that rose plumb and straight above the foundation.

As the screw jacks were turned (each jack was turned the same amount), the foreman on deck used a leveling instrument and sighted on each target to insure that the formwork was rising true plumb and level. If any of the targets did not align with true level, the portion of the deck out of plumb was corrected by extra turns of the screw jack or jacks as necessary to bring that portion of the deck up level with the rest of the formwork. 

Not shown in the photo is the horizontal rebar that was required to form a steel reinforced grid integrally cast in the concrete to form a reinforced concrete structure. Initially, the horizontal steel was wire-tied in place to the vertical rebar prior to one side of the forms being installed.  This placement occurred only to the height of the wood bin forms. Once the form-lifting began, the horizontal steel was placed by hand by pushing and threading the rebar horizontally through the vertical rebar. Because of the vertical movement of the formwork, close attention was required as to the spacing between horizontal rebar. 

Now, try to imagine: the start gun is fired and the continuous action of the many processes begins, never to stop until the wooden forms and finished structure reaches the prescribed vertical height (some 120 feet) eight days later. Manual labor is involved in each discipline. Personnel changes occur, but each position is filled by a replacement. The gun is fired, cement is mixed and lifted to the deck of the formwork via a Georgia buggy, and the content is dumped into the open form. The pouring of the cement into the formwork is continued in a circular fashion around the entire deck until it reaches a prescribed height in the form. 

The finished elevator. Photo from the Neil A. Lieb Archive.

The finished elevator. Photo from the Neil A. Lieb Archive.

Once the cement is allowed to solidify in the forms on the foundation slab, the jacking operation begins and the formwork starts its vertical lifting and slipping process. The jacks are turned, the cement is poured, the vertical rebar and jackrods are placed and spliced, and all the while the horizontal rebar is positioned at the proper height and spacing. Pour cement, turn jacks, place rebar, check deck level, and on and on through night and day until the construction reaches final height. The most problematic aspect of this system is the placing of the horizontal steel at the correct spacing, the placement of formed openings in the bins, keeping the hoist in operation, mixing the cement, and obtaining enough set time of the cement mixture so that as the finished concrete walls do not fall apart or slough off.     

Also, hanging beneath the formwork structure is the scaffolding for the cement finishers who dutifully serve to patch and smoothly finish the concrete surfaces appearing at the bottom of the vertically slipping formwork.