"As already stated, the only possible disadvantages that the unit-system might have are those of transporta tion of heavy members for long distances from the fac tory, and the absence of continuity between members.
"The economies of shop manufacture and erection, combined with the fact that much less volume of concrete is required to produce the same results on account of more economical sections and higher quality of material, will more than overcome the difference in the cost of transportation.
"As to the advantage of continuity of members and rigidity obtained by monolithic construction, here, with out doubt, lies the real problem in the development of the unit-system. However, the problem admits of ready solution by proper care and ingenuity in the fabrication of reinforcement. The members can be made with pro jecting connections, which can be rigidly attached to each other in the field similar to the manner in which structural steel is erected, and these connections can afterwards be fireproofed with a small amount of field concrete.
"The bolting of connections can be substituted for the expense of riveting, as is required in structural steel. For buildings of few stories, the combination of the adhe sion of mortar and the use of projecting dowels is all that is necessary. Such construction requires slightly more steel than is ordinarily used in concrete construc tion, but the expense of this is more than overcome by other economies.
"In cities where the cost of structural steel is not excessive it has been found that a very economical, rapid, safe, and efficient mode of construction is to erect a light structural steel frame, which is designed for dead load only, and is afterwards fireproofed by supporting forms on the members and filling in around them with concrete, the steel being designed just within its elastic limit, and the additional strength required to resist live load and provide for a factor of safety being supplied by the concrete. In the specifications of one designer, this form
of construction is referred to as 'reinforced steel con struction.' Certainly this form of construction could be made much more economical if the concrete fireproof ing were put on at the factory, as it would entirely elim inate the cost of field forms, and enable the designer to take advantage of the fact that the member has the additional strength of the concrete added, enabling him him to reduce the amount of steel. The only additional cost of erecting a reinforced steel frame of this nature over that of a regular structural steel frame designed for both dead and live load, would be the additional cost of transporting and erecting the heavier members. How ever, recent calculations made on a four-story apartment building showed that this form of construction could be carried out using the customary loads for this style of building, and spans of sixteen feet, in which no member weighed more than one ton, the actual weight of the members being a trifle over twice what the weight would be if a structural steel frame were used and designed for both dead and live loads. The saving in forms, the greater speed of erection, the economy of design in this form of construction, certainly warrant its careful con sideration by designing engineers."