where a dry concrete is used, however, some sort of mechanical bond between the reinforcing and the concrete would be advisable.

TABLE XIV.-QUANTITY OF MATERIAL FOR FENCE POSTS.* All posts are 4 X 5 inches at top; all posts are 5 X 6 inches at bottom. One-half small single load † of sand required per barrel of cement; one small single load of screened gravel or stone required per barrel of cement. Proportion: 1 part "Atlas" Portland cement; 2 parts sand; 4 parts gravel or stone.

Methods of Fastening Fence to Posts.-Various methods of fastening the fence to the post are in use at the pres

FIG. 45. Method of Fas

tening Fence to

Post.

ent time, a few of which follow.

Removable pins in the moulds form holes through the concrete posts, which holes receive long wire staples which clinch at the back of the post. These staples can be replaced at any time.

Another method consists of a tie wire passed around the post and then twisted tightly around the longitudinal fence wire. This method would appear to be particularly satisfactory where the face of the post is corrugated.

A variation of the above in which one continuous binding wire is used instead of a number of short pieces.

The advantage of this and the above method is that the position of the ties does not have to be determined in advance, but may be readily shifted to suit any position of the fence wires.

In another method, holes are made in the concrete into which wires are inserted. These wires

* From "Concrete Construction Around the Home and on the Farm," published by the Atlas Portland Cement Co.

†Small single load 15 cubic feet.

are then carried to the front of the post and wrapped tightly around the fence wire.

In the "Monarch" Fasteners and Spring Steel Staples, the fastener is inserted in the post while same is being manufactured.

FIG. 46.-Method of Hanging Gate on Fence Post.

The staple is inserted in the fastener by means of a pair of pliers made especially for the purpose.

The "Tautwire" Fence fastener is moulded into the post when

TABLE XV.-QUANTITY OF MATERIAL FOR CORNER POSTS.* One-half small single load of sand required per barrel of cement; one small single load of screened gravel or stone required per barrel of cement. Proportions: 1 part "Atlas" Portland cement to 2 parts sand to 4 parts gravel.

* From "Concrete Construction Around the Home and on the Farm," published by the Atlas Portland Cement Co.

same is being manufactured. To hold the fence a common wire staple is driven into the fastener.

In all wire fences considerable tension must be put on the wires if a satisfactory fence is to result. To resist this tension occasional fence posts should be braced, and in no case should this bracing be omitted at the corner posts, and the post in many cases should be made heavier than the posts in the rest of the fence.

SECTION IV

PRINCIPLE OF DESIGN AND CONSTRUCTION IN REINFORCED CONCRETE

CHAPTER XVI

ESSENTIAL FEATURES AND ADVANTAGES OF REINFORCED CONCRETE

REINFORCED Concrete is the term applied to that combination of concrete and steel wherein each element of the combination lends a helping hand to make up for the deficiency in strength of the other. The proverb that "In Union There is Strength," was never more exemplified than in the combination of two materials, different in so many respects yet acting together as a unit in resisting any influences that tend to disrupt the structure built therefrom.

Beginning with the building of flower pots by a French gardener 40 years ago, the business of reinforced concrete had a haphazard growth for over twenty years, owing to unfamiliarity with the nature of the materials, distrust on the part of consumers and antagonism of union labor. Through the establishment of safe, rational, and scientific methods of design, made possible by tests and studies carried on consistently by men like Melan, Hennebique, Ransome, Considère, Hyatt, Thatcher, Thompson, and others, confidence has given place to distrust and what only ten years ago was looked upon with suspicion is now hailed as a blessing. The fire at Baltimore and the earthquake and fire at San Francisco have removed the last lingering doubt, and constructors are now agreed that in point of fireproofness, and the ability to withstand severe shock and strains, reinforced concrete has no equal among structural materials.

Concrete itself is very weak in resisting tension, or pulling strains, and possesses but little elasticity, while steel, on the other hand, possesses both these qualities in a high degree. It is thus that the introduction of steel converts a practically inelastic body into one possessing a high degree of elasticity, and thus results in a material having the following inherent qualities: strength, which increases with time, lightness, rapidity of construction, and many other important advantages. So much are the resisting properties increased that reinforced concrete is bound to supplant almost entirely brick and stone masonry in most all of the forms of construction into

PLAIN CONCRETE BEAM

6'8"

REINFORCED CONCRETE BEAM

6'8"

FIG. 47. Comparative Sizes of Plain and Reinforced Concrete Beam for Same Span and Loading.

which the latter so largely enters, particularly in such structures as factories, walls, sewers, aqueducts, bridges, arches, chimneys, dams, tanks, foundations, etc.

The economy of reinforced concrete arises also from the fact that unskilled labor may be employed in the work, and owing to its inherent strength a great saving in material and space is made possible over ordinary brick and stone construction. There are also some disadvantages attending its use, such as the necessity for wooden forms and the difficulties which attend their use, but these are more than offset by the accompanying benefits.

Ease and rapidity of erection arise from the fact that walls can be quickly moulded and floors and roofs are moulded at the same time as the beams which support them. No dressing or dimension cutting is required and material is readily procured in all localities.

The fire proofness of concrete is due to the fact that it is a very poor heat conductor. It expands and contracts at the same rate as the reinforcing steel and there is no tendency of separation be