METHOD OF CONSTRUCTION OF CONCRETE SHIPS. § 



It was found that many of the castings, such as bollards, winches, etc., were 

 not drilled exactly according to plan, and many of the anchor bolts would not meet 

 up with the holes in the castings. It was found that the concrete could be readily 

 drilled and new bolts set, so this defect was not of great importance. It is prefer- 

 able, however, to set the fittings on the forms with holding-down bolts in sleeves 

 attached to the fittings, and pour the concrete around them, or another satisfactory 

 method is to drill the base of fittings from the templets used for setting the bolts. 



KIND AND QUALITY OF REINFORCING STEEL. 



It was originally intended to use deformed square bars of the structural steel 

 grade in sizes ranging from i}i to }4, inches. The square bar was selected with 

 the belief that it could be concentrated more readily into a thin section than the 

 round bar, and a deformed bar was specified on account of its bond value. The 

 square bars were found impracticable because they assumed a twist or wind when 

 bent to conform to the curves of the ship, thus requiring more space than the side 

 dimension, and the deformed feature was found objectionable from the construc- 

 tion standpoint because it was very difficult to weave the deformed bars on ac- 

 count of added friction due to the deformations. The bond stresses in the ship 

 members were generally low and therefore a deformed bar was not necessary, so 

 it was abandoned in favor of the plain, round bar ranging in size from i% to % 

 inches diameter, which has been used in all ships except the Atlantus and Polias, 

 the two experimental ships built by the Liberty Shipbuilding .Company and the Foug- 

 ner Concrete Shipbuilding Company. 



It was intended to use structural grade steel, but early in 1918 the War Indus- 

 tries Board ruled that, because of the great demand for this grade of steel (largely 

 caused by the steel ship program), no more structural grade steel reinforcing could 

 be rolled in the east. It was necessary to substitute rods rolled from the discard 

 croppings from shell ingots. This material, which may be classed as a hard steel, 

 had an ultimate tensile strength of about 95,000 pounds per square inch, and a yield 

 point of about 60,000 pounds per square inch. To provide for the use of this harder 

 steel, two alternate specifications were written. The first, for the structural grade 

 steel, is that recommended by the American Society for Testing Materials, Stand- 

 ard Specification for Billet Steel, Concrete Reinforcement, Structural Grade. The 

 second, for the shell discard material, may be epitomized as follows : — 



1. The steel must be made from new billet, open hearth stock. 



2. The steel must contain more than 0.06 per cent phosphorus. 



3. Its physical properties must conform to the following minimum require- 



ments : 



Yield point 50,000 pounds per square inch. 



Ultimate strength 80,000 pounds per square inch. 



Elongation in 8"%^ 1,200,000 



Ultimate strength. 



