FACTORY VS. FIELD-MADE In regard to the relative merits of factory made reinforced concrete structural work and field-made work, Mr. Charles D. Watson says: "A careful analysis of the present conditions under which reinforced concrete is constructed cannot help but lead one to the conclusion that present methods are still crude and unscientific; and like the history of all such developments, we must abandon the use of hand-made materials, which are subject to faults due to human errors, and adopt the machine-made. If so, the final out come must be the use of factory-made reinforced concrete. Factory-made concrete has obviously every advantage over field-made, except in the matter of continuity of members and the cost of transportation for long distances. As to continuity—with the present development toward the shop fabrication of reinforcement and rigid connections of members, it is doubtful if the monolithic method of construction really has so much advantage in this par ticular. Certainly, more rigidity can be obtained than in a structural steel frame. Furthermore, in the majority of cases it is impossible to get a truly monolithic struc ture by present field methods, since the cost of placing concrete continuously makes it practically prohibitive. There are other positive disadvantages in monolithic designs, due to the absence of expansion joints, the dif ferential expansion of members of different sections, and the consequent thermal stresses set up in such struc tures, which arc beyond the engineer's power to calculate.
"As regards transportation of factory separately moulded members, there can be little doubt that in the larger centers of population the cost of transporting the finished product is overcome by the many other advan tages of the factory-made members, such as: first, elim ination of forms; second, concrete of much greater strength and consequently of much smaller volume to carry equal loads; third, the use of more economical sec tions; fourth, the economy of shop methods of handling and mixing the materials; fifth, the greater speed of erec tion; sixth, certainty of results on account of mechanical methods of fabrication of the reinforcement and casting of members; seventh, the opportunity to test same before subjection of load; eighth, ease of alterations; ninth, absence of accidents during erection ; and tenth, high grade finish made possible by better forms.
"First, as to saving of field forms : It is obvious that any system of concrete construction which will eliminate the present expense of the forms required in field work would be of the greatest advantage. The moulding of concrete in this way is not only expensive, but fraught with great danger, inasmuch as the members are com pletely covered until the forms are removed, which ob scures d?,fects and prevents inspection.
"Second, as to the quality of concrete and section of members: Recent experiments have demonstrated the enormous variation which may occur in the strength of concrete due to its quality. The profession is now giving this question of high-grade material considerable prom inence. IVe constantly hear references to the great strength of concrete with the common expression 'as hard as rock'; but the real conditions under which it is used for structural purposes are such that we are compelled to use working values in compression, which are about half of what we use for soft timber. The result is one of the greatest objections to concrete construction; that is, to get sufficient strength to carry loads, we are com pelled to erect such massive beams and columns that our buildings become architectural monstrosities, besides being uneconomical on account of the space wasted. In entering a concrete building of considerable height and with long spans designed for heavy loads, the massiveness of the beams and columns gives one the impression of clumsiness rather than stability. Development of the science is gradually eliminating this defect ; but the pri mary reason still remains, and can be solved only by the use of a higher-grade material which will have greater strength, so that a smaller section may be used.