Concrete Construction Part 46

B. M. were bought and about twice this much would be needed to enclose the concrete if used only once, we will a.s.sume that all lumber was used twice. Including the props there were about 60,000 ft. B. M., or 70 ft.

B. M. per cu. yd. of concrete. The cost of the lumber was $1,520.86, and the cost of labor on the forms was $1,660.60, so that the cost of forms was:

Item. Per cu. yd. Per M. ft. Per sq. ft.

Lumber $1.74 $13.50 $0.038 Labor 1.90 14.07 0.041 ----- ------ ------ Total $3.64 $27.57 $0.079

If the lumber had been used only once the cost per cubic yard would have been $5.38, and per M. ft. B. M., $41.07.

_Concrete._--A railway track was run the full length of the building upon what was eventually the fourth track of the car barn and a Ransome mixer was set up as close to the track as possible allowing a platform to be built between it and the track. Cars were brought up to this platform and the materials handled by wheelbarrows direct from cars to mixer. Both platform and mixer were moved twice as the work progressed.

The concrete was taken by wheelbarrows on runways to the side walls. For the roof it was hoisted by a horse by means of a mast having an arm with a three-quarters swing; the barrows were hoisted direct using a hook for the wheel and two rings for the handles.

The cost of the concrete for materials was:

1.1 bbl. cement at $1.21, per cu. yd. $1.33 ton sand at 75 cts., per cu. yd. 0.55 Aggregate, per cu. yd. 0.88 61 lbs. steel at 1.9 cts., per cu. yd. 1.15 Lumber, 70 ft. B. M. at $27, per cu. yd. 1.74 ----- Total per cu. yd. $5.65

The cost of labor per cubic yard was:

Forms, per cu. yd. $1.900 Mixing, per cu. yd. 0.210 Placing, per cu. yd. 0.310 Finishing, per cu. yd. 0.143 Handling cement, per cu. yd. 0.017 Handling sand, per cu. yd. 0.104 Handling steel, per cu. yd. 0.270 Handling aggregate, per cu. yd. 0.222 Coal, at $4.25 per ton, per cu. yd. 0.010 Foreman, per cu. yd. 0.133 Teams and laying pipe line, per cu. yd. 0.087 ------ Total, per cu. yd. $3.406

Summarizing, we have the following cost per cubic yard:

Concrete materials, per cu. yd. $2.76 Labor mixing and placing concrete 1.01 Forms, materials and labor 3.64 Reinforcement, materials and labor 1.42 Fuel, foreman and pipe line labor 0.23 ----- Total, per cu. yd. $9.06

The cost for handling steel, making stirrups, welding, etc., was $8.90 per ton, or 0.45 ct. per lb.

_CONSTRUCTING WALL COLUMNS FOR A ONE-STORY MACHINE SHOP._--The building was 53600 ft.; each side wall consisted of 40 columns of channel section carried on footings of channel section somewhat heavier than that of the column. The columns were s.p.a.ced 15 ft. on centers and each was 7 ft. wide so that there were 7 ft. s.p.a.ces between columns, which were filled with 3-in. curtain walls extending 7 ft. above the floor.

Figures 228 and 229 show the column and footing construction. Each column contained 125 cu. ft., or 4.63 cu. yds. of 1-3-5 1-in. crushed slag concrete above the footing and the costs given here relate only to the columns above footings. In the 80 columns there were 370 cu. yds. of concrete.

_Forms._--A column form is shown by Fig. 230; it contains approximately 1,000 ft. B. M. of lumber. Ten of these forms were used, so that 10,000 ft. B. M. of form lumber were required for 370 cu. yds. of concrete, or 27 ft. B. M. per cu. yd. of concrete. Each column had a superficial area excluding ends of about 420 sq. ft., so that 420 80 = 33,600 sq. ft.

was the superficial area of all the columns and 10,000 ft. B. M.

33,600 sq. ft. = 0.3 ft. B. M., or, say, 1/3 ft. B. M., of form lumber was used per square foot of concrete enclosed. The cost of the forms per 1,000 ft. B. M., and, therefore, per form, was:

Lumber, 1,000 ft. B. M., at $31.75 $31.75 Labor constructing form 16.39 ------ Total per 1,000 ft. B. M. $48.14

[Ill.u.s.tration: Fig. 228.--Channel Section Wall Column for Factory Building.]

This gives us a cost per cubic yard of concrete for materials and labor constructing forms of $480 370 = $1.30, and per square foot of outside wall area of $480 (146 80) = 4.1 cts.

The erection and taking down of the forms, owing to the weight of some of the pieces, was done by means of special derricks. The footings were brought to within in. of grade and a tenon form of the exact shape of the channel section of the column was placed on top and filled with grout to a depth of 1 in. These tenons served as guides in setting the column forms, and proved to be much quicker and more accurate than points.

[Ill.u.s.tration: Fig. 229.--Footing for Wall Column Shown by Fig. 228.]

The forms were a.s.sembled on the ground and erected by a 35-ft. A-frame derrick mounted on wheels. The construction is shown by Fig. 231. This derrick had a capacity of about 4 tons and carried a Ransome friction crab hoist driven by a 5 h.p. Meitz & Weiss kerosene oil engine. It was the practice to set a number of forms before filling any. This enabled the carpenter gang to be plumbing up the first form while the erecting gang were setting others. The forms had to be very securely guyed and braced to withstand the impact of the falling concrete. Very little trouble was had in keeping them well lined up.

[Ill.u.s.tration: Fig. 230.--Form for Molding Wall Column Shown by Fig.

228.]

Two gangs were employed in a.s.sembling forms and a portion of the men in each gang also shaped and placed the reinforcement and placed and tamped the concrete in the forms so that no exact division of labor is possible. The organization of these gangs and the wages paid were as follows:

Derrick Gang:

1 foreman, at 36 cts. per hour $ 3.94 1 crabman, at 30 cts. per hour 2.70 2 topmen, at 27 cts. per hour 4.86 2 bottom men, at 23 cts. per hour 4.14 ------ Total per 9-hour day $15.64

a.s.sembling Gang:

1 boss carpenter, at 47 cts. per hour $ 4.23 2 carpenters, at 36 cts. per hour 6.48 2 carpenters, at 30 cts. per hour 5.40 2 carpenters' helpers, at 25 cts. per hour 4.50 4 men forming and placing reinforcing steel and rethreading bolts, at 23 cts. per hour 8.28 ------ Total per 9-hour day $28.89 ------ Grand total $44.53

These gangs a.s.sembled and erected the molds and concreted 80 columns in 22 working days, including 2 days lost on account of cold weather, so that 4 columns were completed per day of 9 hours. We can subdivide the cost as follows:

Item. Per cu. yd.

Erecting forms and concreting $0.81 a.s.sembling forms and reinforcement 1.56 ----- Total $2.37

Charging the 4 men placing reinforcement and rethreading bolts to forming and placing reinforcement alone we can figure the cost of fabrication and erection of reinforcement very closely. There were 160 lbs. of reinforcing steel in each column, hence $8.28 (160 4) = 1.3 cts., was the cost per pound of forming and placing it. This includes handling.

The stripping of the forms was carried on by another gang using a derrick similar to the first one described, except it could be of lighter construction as it had to handle only the separate parts of each form and not the forms a.s.sembled. The derrick shown in Fig. 232 was a 33-ft. A-frame, with wheels at the bottom of each leg. It had a friction crab hoist driven by an electric motor, both of which were fastened to the derrick frame between the shear legs.

[Ill.u.s.tration: Fig. 231.--Derrick for Erecting Wall Column Forms Shown by Fig. 230.]

The operation of stripping required only four men and the crabman. The outside flat panel was removed first, and left leaning up against the concrete while the inside trough shaped panel was pried loose and lowered onto the ground with its inside face uppermost. The side panels being comparatively light, were stripped without the use of the derrick, and these panels were a.s.sembled on the ground with the inside piece. The derrick then picked up the outside panel again, and placed it in its proper place. After the bolts were put in place, the a.s.sembled form was moved on rollers to another point in the line of columns where it was again erected. The arrangement of derricks for erecting and stripping forms is shown in Fig. 233.

The gang stripping forms was made up as follows:

1 foreman, at 30 cts. per hour $ 2.70 1 crabman, at 27 cts. per hour 2.43 1 topman, at 27 cts. per hour 2.43 2 bottom men, at 23 cts. per hour 4.14 ------ Total per 9-hour day $11.70

[Ill.u.s.tration: Fig. 232.--Derrick for Stripping Wall Column Forms Shown by Fig. 230.]

This gang of five men stripped 4 columns containing 18.52 cu. yds. of concrete each day, so that the cost of stripping was $11.70 18.52 = 62.7 cts. per cu. yd.

_Concrete._--The concrete was mixed in a No. 2 Ransome mixer and delivered to the work in Ransome concrete carts. These carts were pushed along a runway which terminated in a slight incline under the derrick so that their contents could be emptied into the derrick buckets.

The concrete was hoisted in an 8-ft. bottom dump bucket, using the derrick described above. It was necessary to stir up the concrete thoroughly with long-handled slicers as it was being deposited in order to prevent segregation. This expedient combined with a wet mixture and tight molds was found to overcome this difficulty very effectually.

The gang mixing and wheeling concrete was made up as follows:

1 mixer foreman and engineer at 27 cts. per hour $ 2.43 4 laborers charging mixer at 18 cts per hour 6.48 4 laborers wheeling concrete at 18 cts. per hour 6.48 ------ Total per 9-hour day $15.39

This gang mixed and wheeled concrete for four columns, or 18.52 cu.

yds., hence the cost per cubic yard was 82.6 cts.

With cement at $1.60 per bbl., sand at $1 per cu. yd. and slag at $1.10 per cu. yd. the cost of materials per cubic yard of concrete was $3.

[Ill.u.s.tration: Fig. 233.--Arrangement of Derricks for Erecting and Stripping Forms.]

Summarizing the above figures we have the following cost per cubic yard of concrete in place:

Item. Per cu. yd.

Concrete materials $3.00 Reinforcing steel 0.73 Forms, lumber and framing 1.30 Forms, erecting and concreting 0.81 Forms, a.s.sembling and reinforcement 1.56 Forms, stripping 0.63 Mixing and wheeling concrete 0.83 ----- Total $8.86

~CONSTRUCTING ONE-STORY WALLS WITH MOVABLE FORMS AND GALLOWS FRAMES.~--In constructing the walls for an 8530-ft. factory building at Old Bridge, N. J., Mr. A. E. Budell made use of movable forms and gallows frames to construct the curtain walls and columns in one piece. Each side wall was built its full height in successive 50-ft. lengths by depositing the concrete between two forms which were moved upward as the concreting progressed. Fig. 234 indicates the mode of procedure. The form was raised and lowered by means of two gallows frames fitted with blocks and tackle. A steel cable, with a trolley affixed, extending from one frame to the other, provided a convenient mode of hoisting material to the form, and the gallows frames took the place of ladders for climbing onto the structure. No scaffolding whatever was used and only one man was required overhead to dump the buckets and tamp the concrete into place.