(3) Wheel reactions of the hoist carriage resulting from a hangup of the rake, assuming a 25-kip pull on the drawrope attached to the rake 30 inches above the tracks to cause a couple on the carriage wheels.

The beams were assumed to be continuously supported on the lateral bents. Positive or negative thrusts which could be produced by temperature expansion or shrinkage were neglected in the analysis, since expansion joints were provided intermittently along the beams about every third span.

(f) Bents Above Elevation 5535.-- The lateral members which support the inclined trashrack guide beams are formed as sloping legged bents. This shape was adopted to permit the beam to flex under temperature expansion and shrinkage, and thereby reduce the high moments and shears which would otherwise exist. Weight components parallel to the plane of the racks are sustained by transverse bending of the bents. The bents are tied monolithically into the abutment slabs.

(g) Abutment Walls Above Elevation 5535.--The 3-foot minimum-thickness abutment slabs are anchored into the rock foundation, in a similar manner to that adopted for the arch thrust slabs. Thrusts and moments from the lateral bents are distributed into the abutments by uniformly spaced anchor bars embedded into the abutment rock.

(h) Bridge and Gantry Parking Structure.-- The bridges and the gantry support structure at the top of the intake structures were designed to support an AASHO Standard Specifications highway loading H20-44. The gantry parking structure beams and bents were designed to support gantry crane wheel loads of 12, 500 pounds, and a lateral windload equal to 30 pounds per square foot of exposed area. The bases of the supporting columns of the bents are anchored to the foundation rock to provide added restraint against lateral loads. Roller bearing supports are provided at the bridge seats to accommodate movements of the bridge from temperature change. A camber of 1 inch is provided for each bridge span to allow for deflection of the bridge under dead load.

41. Inlet Lining and Inclined Transition. The inlet linings downstream from the trashracks and upstream from the fixed-wheel gates are reinforced to withstand the differential hydrostatic loadings occasioned by a clogging of the rack bars, on the basis that full hydrostatic uplift pressures might develop behind the lining. A differential head of 40 feet between the uplift and the pressure inside the rack was assumed for design. The lining as reinforced will also withstand flexural stresses induced by the fixity of the anchor bars which tie the lining to the foundation rock. The gate slot seats are reinforced to withstand the stresses induced by the wheel loadings of the fixed-wheel gates.

The inclined shaft lining downstream from the fixed-wheel gates and the lining at the vertical elbow connecting the inclined shaft to the horizontal tunnel are reinforced to withstand an external hydrostatic pressure caused by a reservoir head corresponding to the minimum power head level, elevation 5497. This assumed loading condition was based on the presumption that reservoir storage would be initiated before the power installations or the outlet control gates would be completed, and that full uplift pressures could develop while the tunnels were unwatered awaiting completion of the downstream facilities. It was also assumed in the design of the lining that the tunnel plug at the elbow would not be installed before the external hydrostatic pressure could develop. With the plug installed and the joint between the plug and the lining grouted, the reinforcement design was checked assuming that an external hydrostatic pressure could develop equal to the maximum reservoir head. For this condition the reinforcement was permitted to develop a stress approaching 24, 000 pounds per square inch.

42. Tunnel Linings. The outlet and power tunnels were excavated to a diameter of 31 feet and lined with a concrete lining 2 feet 6 inches thick to provide a 26-foot inside-diameter waterway. Because of poor rock conditions encountered in excavating the tunnels, structural steel rib supports were used throughout their lengths. In the lower reaches of the tunnels the concrete linings encase steelplate liners to insure watertightness. The concrete linings were reinforced with varying amounts of steel reinforcement along different portions of the length of the tunnels. The loadings assumed to act on the tunnel lining, for ascertaining the reinforcement requirement, were as follows:

(1) From the P.T. (point of tangency) of the vertical elbow, station 4+20, to a point opposite the upstream edge of the impervious zone of the dam, station 7+50, for normal design conditions the external hydrostatic pressure was assumed to be equal to the internal pressure. Except along certain reaches where the surrounding rock was severely shattered, the tunnel lining was reinforced for the condition of an empty tunnel and of the superimposition of a 90° rock wedge resting on the crown of the lining. Along the shattered rock zones, from station 5+20 to station 7+10 in the outlet tunnel and from station 5+70 to station 6+80 in the power tunnel, it is possible for the surrounding rock to deform without assuming stress. The lining was therefore reinforced to resist the full internal pressure load, on the assumption that external resistance, either from external hydrostatic pressure or from external restraint, would not develop to counterbalance this load.

(2) From station 7+50 to station 10+12 (the beginning of the steel-lined section) the external hydrostatic pressure was assumed to vary linearly from full head at the upper end to zero head at the downstream end. The lining was reinforced to resist the differential loading between the full internal pressure and the diminishing external pressure. The surrounding rock was assumed to take none of the load. The concrete was assumed to take no tensile stress.

(3) From station 10+12 to the downstream portal, the lining was designed to resist the entire internal pressure loading, considering that no external hydrostatic pressure exists and that the surrounding rock takes none of the load. The 3/8-inchthick steel liner was assumed to absorb one-fifth of the internal pressure load, with the surrounding reinforcement taking the remaining four-fifths of the load. The concrete was assumed to take none of the tensile stress. The cut-and-cover conduit section at the downstream portion of the power penstock waterway was designed to assume full internal water pressure, considering no support from the surrounding material, on a basis similar to that assumed for the tunnel lining design. However, the design was checked for a condition of external fill load, considering the conduit to be unwatered. This analysis showed the condition of full internal hydrostatic load to govern the design.

The hydrostatic pressure gradient used for determining the internal pressure loads in the outlet tunnel was assumed uniform at elevation 5620. For the power penstock tunnel, the pressure gradient was assumed to increase from elevation 5620 at station 3+72 to elevation 5724 at station 19+03. This pressure rise would be a water hammer effect resulting from a sudden closure of the turbine wicket gates. No pressure rise assumptions were considered for the outlet works tunnel, since it was reasoned that an instantaneous closure of the control gates would be a remote possibility and that the water hammer effect therefore could not occur.

For the reinforcement steel embedded in the tunnel and conduit lining, an allow

able stress of 24, 000 pounds per square inch was assumed.

43. Penstock Manifold Anchorages and Embedments. - The steel power tunnel penstock manifold pipe was designed to withstand the full hydrostatic head and waterhammer loadings, considering that no stress would develop in the encasing concrete until the pipe had reached its allowable design stress. The concrete encasement placed around the manifold serves as a protective covering for the steel pipe and as an anchorage to resist the unbalanced horizontal hydrostatic thrust components which will be induced at the pipe bends and branches. The encasement also provides stability to resist uplift forces resulting from tailwater seepage under the anchor blocks. To further assist in stabilizing the anchorage at the downstream end of the manifold, 15-foot-deep anchor bars tieing the encasement to the foundation rock are provided. The concrete encasement is nominally reinforced and it is expected that under maximum head the concrete will crack to allow elongation and full development of stress in the pipe shell. The encasement is reinforced sufficiently, however, to sustain external loadings from backfilling or from movement of construction equipment over the manifold when the manifold is not under internal pressure.

The steel outlet manifold pipe and its encasement were designed on the same basis assumed in designing the power penstock manifold and encasement, except that the assumption of pressure rise due to internal water hammer was not included.

44. Outlet Works Control House Structure. Loading assumptions used in the design of the outlet works control house structure are indicated on figure 71. Assumed working stresses for the structure concrete and reinforcement are shown on figure 51.

The concrete in the control house substructure, which embeds the manifold transitions and gates, is reinforced to withstand the full internal pressure plus waterhammer loadings where applicable. For this assumption it was considered that no load would be taken by the transition liners and the gate housing castings.

The superstructure frame was designed as a rigid bent assuming various combinations of loading listed on figure 71. The design analysis was based on procedures and criteria outlined in Technical Memorandum 637 7/. Allowable increase in working stresses for extraordinary loadings were assumed as listed in figure 71.

The end of the control house building adjacent to the steep abutment slope was designed to resist a loading occasioned by a snowslide. The loading is indicated on figure 71 as an avalanche load listed under the heading of miscellaneous loads.

45. Stilling Basin Floor and Walls. The stilling basin floor and left side lining are anchored to the foundation rock with anchor bars at about 5-foot centers embedded a minimum distance of 8 feet into the rock. The lining slabs are nominally reinforced with a top and a bottom layer of steel reinforcement to resist the flexural stresses in the lining induced by the fixity of the anchor bars resulting from an unbalanced uplift loading under the slab. It is expected that the relief offered by the underdrains, along with the anchorage of the slab to the foundation rock, will prevent displacement of the lining occasioned by unbalanced uplift pressure load.

The counterforted wall along the right side of the stilling basin was designed to be stable against either the condition of an empty basin or the condition of the most severe sweepout condition occasioned by maximum flow through the outlets. Stress analyses for determining reinforcement requirements were in accordance with standard procedures for the design of counterforted walls.

The dividing walls in the stilling basin are cantilevered from the floor slabs and were designed to resist unbalanced loadings arising from different discharge combinations through the outlet works. Reinforcement is provided in the cantilever stem and in the floor lining to resist the moments and shears induced by the most severe loading assumptions.

D. Outlet Works Control House

46. Architecture. The architectural design of the outlet works control house superstructure is quite similar to the powerplant. The cast-in-place concrete walls, 7 feet 2 inches high, provide a base for the reinforced grouted brick masonry walls and grouted brick veneer walls. The architectural treatment, in harmony with that of the powerhouse, is simple and devoid of unnecessary ornamentation. The windows in this structure are not continuous, but are individually placed just above the concrete basewall. The control house superstructure measures 162 feet long by 40 feet wide and rises approximately 32 feet above the operating floor level. The substructure height from the discharge channel floor level to the operating room floor level is approximately 20 feet. The walls of the superstructure at the front and back sides and at the end facing the powerplant consist of a 7-foot-high wainscot band of reinforced concrete, above which they are constructed of brick masonry to match the architecture of the powerplant building. The left wall, facing the hillside, is of reinforced concrete, to withstand loads occasioned by possible snowslides or landslides originating along the steep abutment slope.

7/Reinforced Concrete Design Data, U. S. Bureau of Reclamation, Technical Memorandum No. 637, June 1949.