363. Notable Examples of Concrete Buildings

Perhaps the best known of all concrete buildings in the United States are the hotels Ponce de Leon and Alcazar, at St. Augustine, Florida, Messrs. Carrere & Hastings, architects.

These buildings, composed entirely of concrete, and exhibiting all the strains to which building material can be subjected, present an example of the almost limitless use to which concrete can be put.

For the construction of these buildings an elevator was built at a -central point of the operation, to the full height of the intended building, and as the walls progressed, story upon story, runways were made to each floor, and the concrete, mixed by two capacious mixing machines on the ground level, was lifted in barrels and run off to the place of deposit. At times in the progress of the work 400 pounds of cement were used in the concrete in a single day.

The time transpiring between the wetting of the concrete and the final running in place, even at the fifth story, was not more than ten minutes at any time.

The concrete was composed of 1 part imported Portland cement, 2 parts sand and 3 parts coquina (a shell), the greater part passing through a -inch mesh.

The cost of the concrete in place was about $8 a yard, including arches, columns, etc. In plain thick walls the cost was often much less.

In the basement of the Alcazar is a bathing pool 100 feet long, 60 feet wide and 3 to 10 feet deep, all made of concrete. Rising from this pool are concrete columns, 6 feet square at the base and 40 feet high. These columns support concrete beams of 25 feet span, hollowed out in arch form, which support the glazed roof covering the interior court.

364. The Leland Stanford, Jr., Museum, at Palo Alta, California, a very large and costly building, is also constructed entirely of concrete. This building was built on the Ransome system - using twisted iron rods imbedded in the concrete to give tensile strength where required.

The following description of this building, written by the architect, Mr. Geo. W. Percy, gives some idea of the method of construction and also of the cost.

This building was designed to have dressed sandstone for the external walls, backed up with brick, and to have brick partitions with concrete floors. Owing to the great cost of stonework, it was decided to build the walls of cement concrete, colored to match the sandstone used in the other university buildings, and to carry out the classic design first adopted. This led to making the entire structure walls, partitions, floors, roof and dome of concrete, making it, in that respect, a unique building.

363 Notable Examples of Concrete Buildings 100257

Fig. 240.

Having some knowledge of the disadvantages and defects natural to a mono"-lithic building, such as result from the shrinkage and the expansion and contraction of walls, floor and roof, several new experiments were tried to overcome them, with varying results of success and failure. It was thought to overcome the cracking of walls by inserting sheets of felting through the walls, following the lines of the joints as near as practicable on each side of the windows. The lapping bond of the concrete, however, proved too strong to allow the cracking to follow these joints; in most cases the weakest points were found at the openings, and small cracks appear from window head to sills above.

Joints were formed through the floors about 15 feet apart and in most cases the cracking has followed these joints and been confined to them. To prevent the possibility of moisture penetrating through the walls, and also to render them less resonant, hollow spaces 5 inches in diameter were moulded in the walls within 2 inches of the inside face, and with about 2 inches of concrete between them. These are successful for the primary object, and partially so for the secondary. The roof being the greatest innovation, and the first attempt known to the writer of forming a finished and exposed roof entirely in concrete, required the greatest care and consideration. The result in form and appearance is shewn by Fig. 240, A and B, and may be described as follows: The roof is supported on iron trusses 10 feet on centre, and has a pitch of 20 degrees. The horizontal concrete beams rest on the iron rafters, and with the half arches form the horizontal lines of tiles about 2 feet 6 inches wide, with the joints lapping 2 inches and a strip of lead inserted as shown. Vertical joints are made through the concrete over each rafter with small channels on each side. These joints and channels are covered with the covering tiles shown on drawings, and similar rows of covering tiles are placed 2 feet 6 inches apart over the entire roof, thus forming a perfect representation of flat Gre-cian tile or marble roof. Notwithstanding the precautions taken, this roof presented several unexpected defects. The most serious proved to be in the Venetian red used for coloring matter and mixed with the cement. This material rendered the covering tiles absolutely worthless, many of them slacking like lumps of lime, and all were condemned and re-made. The same material injured the general surface of the roof, rendering it porous and necessitating painting. The roof over the central pavilion being hidden behind parapets, is made quite flat and covered with asphaltum and gravel over the concrete. This roof, with its low, flat dome, is without question the largest horizontal span in concrete to be found anywhere on earth, being 46 feet by 56 feet, the flat dome having all its ribs and rings of concrete, with the panels or coffers filled with 1-inch thick glass and weighing about 80,000 pounds.*

363 Notable Examples of Concrete Buildings 100258

Fig. 241.

This structure covers 21,000 feet and contains over 1,100,000 cubic feet of space. It required about 260,000 cubic feet of concrete, and was completed in seven months from the commencement of the foundations.

The cost of the building per cubic foot, including marble stairs and wainscoting, cast iron window frames and sashes, and other parts to correspond, was about eighteen cents, which is a very low figure for a thoroughly substantial and fireproof building.

Other important buildings which have been executed in concrete in the vicinity of San Francisco are the Girls' Dormitory at the Stanford University (a three-story building completed in ninety days from the time the plans were ordered), the Science and Art building, Mills College; the Torpedo Station on Goat Island, 80x250 feet, and an addition to the Borax Works at Alameda. In the latter the walls, interior columns and all floors are of concrete, and are remarkable for the lightness of the construction and great strength.

All of these buildings were built on the Ransome system.

365. The Alabama Hotel, Buffalo, N. Y - The only large building constructed of concrete in the Eastern States in recent years that the author is acquainted with is the Alabama House, at Buffalo, N. Y., Mr. Carlton Strong, architect. This building is 60x180 feet in size and six stories high, with all walls, floors and partitions built of concrete.

The general plan of the wall and floor construction is shown by Fig. 242, which represents a partial section at level of third floor.

The whole thickness of the wall is 24 inches from top to bottom, the inner portion being 2 inches thick for the whole height; the outer portion is 8 inches thick in first story, and diminishes by 1 inch in each story.

Vertical twisted rods are built in the walls, as shown in the figure, except that they are spaced about 15 feet apart lengthways of the wall. Opposite these vertical rods the withes are 3 inches thick, elsewhere 1 inches thick. In each withe are built inch twisted rods, extending across the wall, and placed 12 inches apart vertically. At each floor level -inch horizontal bars are imbedded in the walls as shown. These twisted steel bars unite perfectly with the concrete and tie the walls together in all directions, while the shape of the wall gives the greatest stability with the least amount of material. If will be noticed that the plan of this wall is very similar to that of the wall shown in Fig. 155. The concrete wall has this advantage over the brick wall, that moisture does not pass through the solid concrete withes, while there is a possibility of its doing so in brick withes. The spaces in the wall are stopped at each floor level, except that for purposes of smoke flues or ventilation some of them are more or less continuous.

* Fig. 241 shows an interior view of this dome and the hallway and corridors beneath. All the construction shown in this view is of concrete. In the first story the walls are cased with marble slabs, above they are finished with plaster.

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Fig. 242.

The floors in this building are built on the Ransome system, of concrete with twisted rods. Most of the floors are of the paneled construction shown in Fig. 188 A, although some portions are flat, and of the type shown in Fig. 188.

The partitions are also constructed of concrete, with twisted rods, and, being monolithic, add greatly to the stiffness of the building.

Most of the concrete used in the construction of this building was made in the proportion of 1 part Portland cement to 6 parts aggregates.

The contractors state that the average cost of the wall was twenty-five cents per square foot of outside surface.

This building was commenced in 1894 and completed in 1896.