Niagara Falls 100.000-Hp. Development

20 ] Niagara Falls 100,000 Hp. Development charge of the turbine. The draft tube of the I. P. Morris Co. unit consists of heavy flared reinforced-con- crete wings suspended from the foundation slab of the unit and a center cone extending up between and cen- tering these wings. The foundations for the units outside of the draft tube are practically the same. A cross section through both units is shown in an accom- panying drawing. Condition of Turbine Loading In the Allis-Chalmers unit the generator is sup- ported by a heavy cast-iron frame called the “pit liner,” having a top diameter of 22 ft. 4 in., a diameter at the bottom of 17 ft. 2 in. and a height of 9 ft. 4 in. This is carried by the speed ring which is a circular steel casting that acts as a stationary guide for the water entering the runner. The speed ring in turn is sup- ported by another circular casting called the “discharge ring.” This casting rests on the foundation slab, and the concrete inside of this casting is cut out and formed to the shape of the draft tube. The diameter of the opening at the top of the foundation slab is 10 ft. The opening gradually increases in size through the slab and becomes tangent at the bottom. The diameter at the point of tangency is 24 ft. 4 in. In the I. P. Morris unit the generator is supported by massive concrete piers which rest directly on the heavy cast-iron wheel case. The load is transferred from the wheel case to the foundation slab and the dis- tribution is more favorable than in the other unit. The flared wings of the draft tube are attached to the bot- tom of the main foundation slab with three rings of reinforcing bars. The opening in the main slab is similar to that of the Allis-Chalmers unit. The actual weight of one complete unit consisting of one generator and turbine is in excess of 1000 tons. The entire weight from power house floor to the top of the tailrace on the neat inside line of the foundation piers is 5‘500 tons per unit. It was assumed that this entire load was carried by the main foundation slab. The amount of arch action was impossible to determine owing to the nature of the load concentration of the machine in the vicinity of the opening for the draft tube. The main foundation slab is 11 ft. thick. It has a clear span of 45 ft. The reinforcing consists of eight bands of steel bars, each band containing twenty-five 14-in. square bars. In addition to this there are about 450 vertical 1-in. square bars, spaced about 2 ft. centers over the entire area acting like stirrups. It was thought advisable to tie this large mass of concrete together since there is about 1000 yd. of concrete in each slab, and for construction reasons it was decided to pour this slab in two sections. In addition to these vertical bars, limestone plums were placed so that about one-half of the stones projected above the neat line of the first pour to act as an additional horizontal tie. The entire surface was picked, roughened and thoroughly cleaned before the final pour was made. In the design of the main foundation slab each band was considered acting as a beam and assumed to carry one-eighth of the total load inside the neat line of the foundation piers, the load being considered as uni- formly distributed. Based upon this assumption the unit stress in the reinforcing steel is 15,000 lb. per square inch and in the concrete 450 lb. per square inch. FIG. 28—TAIL RACE EXIT OF EXTENSION TO PLANT NO. 3 The unit shear on the neat line of the foundation piers is 45 lb. per square inch. The foundation slab is carried by the main power house piers, which are spaced 53 ft. centers, and one smaller center pier. The main piers are 13 ft. thick at the river face of the power house and gradually taper down until they are 8 ft. thick at the center line of the unit. These piers are joined together from this point by a concrete wall 4 ft. thick, against the bedrock, hav- ing a radius of 22 ft. 6 in. to the inside face. This makes a horse-shoe shaped tailrace, semi-circular at the rear end and slightly contracting until it reaches the river face of the power house. The piers are rounded off to a radius of half their thickness at the river face of the foundation. Superstructure of Power House The power house, which is located in the gorge, is a building 60 ft. wide inside with a 6-ft. space between the back wall and the cliff, this space being used for cable and hot air passages. It extends 225 ft. upstream from old Station No. 3. The floor of the power house is at EL 365, which is 7 ft. above the highest known water level and is 23 ft. 6 in. above mean water level. The roof is 80 ft. above mean water level. The operating gallery is 20 ft. wide and extends along the entire west side of the building and is 13 ft. 3 in. above the power house floor, being on a level with the walks leading to the top of the generators and around the Kingsbury bearings, The east wall of the power house is of concrete and the west wall which faces the river is of rough rubble masonry, being the same as all masonry walls used in the construction of Station No. 3. This type of masonry is used as it harmonizes the best with the existing cliffs. The weight of the rotating parts of one unit is about 200 tons. Two 100-ton cranes and a lifting beam con- stituted the crane equipment for the installation of the new plant. The total moving load transverse to the building consists of the live crane load, the weight of the lifting beam and the crane trucks, making a total load of 260 tons. The moving load in the longitudinal direction of the building consists of the weight of the crane bridge in addition to the transverse loading, mak- ing a total load of 340 tons. The coefficient of sliding friction between the wheel and the truck was assumed