53 



inforcement is bent into hoops by means of rolls and the ends are welded, 

 or overlapped and tied together with wire, or bent to form hooks and a 

 longitudinal rod passed through the eye of the hooks. 



The pipes may be made in short sections cast in moulds as the non- 

 reinforced pipe described above, or they may be built continuously in the 

 trench. The latter method has the advantage that it does away with the 

 joints which are usually the point of weakness, but it requires a thicker 

 pipe and is only used for the larger sizes of pipes. For pipes up to 4 or 

 even 5 feet in diameter the first method is generally used and the pipes 

 are cast in sections 3 to 8 feet long. The thickness of the shell seldom 

 exceeds 2 % to 3 x /i inches. When the reinforcement consists of a spiral, 

 the wire is wound by machinery and kept to the proper spacing by means 

 of longitudinal rods tied to the spiral wire. When hoops are used, they 

 are also tied to the longitudinal reinforcement. 



Two companies in the United States make a specialty of the construc- 

 tion of reinforced concrete pipes. One is known as the Meriwether pipe 

 made by the Lock Joint Pipe Co., of New York, with branches at Win- 

 nipeg arid at Seattle, Washington. The other is made by the Reinforced 

 Concrete Pipe Co., of Los Angeles, California. These manufacturers make 

 pipe lip to 72 inches in diameter, from 2% to 7 inches thick, in sections 3 

 feet long. On the Umatilla project, in Oregon, several miles of reinforced 

 concrete pipe 30, 46 and 47 inches in diameter have been constructed. 

 The sections were made 4 feet long for the 30 inch pipe and 8 feet long for 

 the larger size. The Roswell park project in Idaho has four miles of re- 

 inforced pipe, some of it resisting heads of 70 feet. 



1. Method of Casting Reinforced Concrete Pipe. (Umatilla Project, 

 Oregon.) 



The pipes are usually cast in moulds which consist of an inside col- 

 lapsible core, an outside sectional jacket and a base ring. The process of 

 casting used on the Umatilla project is a good illustration of this form 

 of construction. For the large size pipe cast in sections 8 feet lon, the 

 inside core is made of two main pieces of curved steel plate % inch thick, 

 held together by a vertical hinge, and a third narrow closing piece or wedge 

 which fits between the other two pieces when the core is set up and is re- 

 moved when the core is collapsed. The outside jacket is made of twelve 

 curved parts, each 2 feet high and 1-3 of a circumference in length, which 

 when joined in sets of three form a section of the jacket 2 feet high. 

 These parts are made of % inch steel plate and to the edges of each part 

 are riveted angles by means of which the parts can be bolted together. 

 The base ring which forms the bell end of the pipe is made of cast iron. 

 (Figs. 40, 41). 



To set up the moulds the inside collapsible core is placed in position 

 fitting inside the base ring, and the lowest section of the outside jacket is 

 formed by bolting the three parts around the base ring. The reinforcing 

 skeleton is placed around the inside core, then the concrete, which is a wet 

 mixture of 1 part of cement to 1.8 parts of sand and 3 parts of gravel, is 

 poured between the forms and worked down by means of thin tamping 

 bars. (Fig. 37). The outside jacket is built up in sections, each being 

 filled nearly to the top before the next one is bolted on. To fill the last 

 section a funnel shaped collar is placed around the inside core and bolted 

 to the top of the section. When filled the collar is removed and the upper 

 end of the pipe is finished by hand. The forms are removed 24 hours 



