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N. Wall plates are placed in the side walls to provide a track for the seals and Wall Plates guide rollers. The wall plates are supported on clip angles and anchor bolts. The assembly is adjustable so that the plates can be lined up before grouting. Tolerances should be shown on the installation drawing for the distance between the wall plates as follows:

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O. Molded rubber seals are bolted to the upstream side of the faceplate Rubber Seals along both sides and the bottom. The side seals are installed in contact with the wall plates. The bottom seal should have 1/4-inch compression when the gate is closed.

P. The following are drawings showing radial gate installations: Reference
Radial Gate and Hoist Installation
(Figure 31) 214-D-15664

10- to 12-foot Radial Gate, Heads
10 to 11 Feet (Figure 30) 40-D-4658

.22 Large-type radial gates are now designed to serve the particular needs of large RADIAL spillways on power dams, reservoirs, and river outlet works, which represents GATES -a relatively new field of application for radial-type gates. Because the design SPECIAL is governed directly by individual operating characteristics, crest contours, TYPES piers, etc., these gates are classified as a special type. Operated by electric hoists, the gates permit either an increase in the active storage capacity of a reservoir with a resulting increased operating head at the powerhouse turbines, or the drawing down and regulation of the storage reservoir in case of an impending flood.

The largest radial gate designed by the Bureau is 50 feet in width and 70 feet
in height and probably is near the upper practical design limit. If the require-
ments for a larger size should arise, it is believed that a gate of the drum-gate
type would prove to be more economical.

Designs of large-type radial gates are illustrated on the following drawings:

51-foot by 34.5-foot Radial Gate Installation--
Canyon Ferry Dam (Figure 32) 296–D–86

51-foot by 34.5-foot Radial Gate Assembly--
Canyon Ferry Dam (Figure 33) 296–D–87

50-foot by 30-foot Radial Gate Assembly--
Enders Dam (Figure 34) 328-D-215

The high-head radial gate is employed for flow control in submerged openings

or sluiceways. The limits of operating head on this gate are governed by practical limitations of spouting velocity and other hydraulic behavior, which

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have not been fully explored. However, promising hydraulic and economic
features are indicated and the hoisting effort for operation is less than for
other types of regulating gates. A design of a high-head radial gate is
illustrated on the following drawing:

22-foot by 19-foot High-head Radial Gate--
Davis Dam (Figure 35) 351-D-637

A. The principal moving gate members of the special-type gates consist of skin plates, longitudinal main girders, intermediate and arm diaphragms, seals, guide rollers, and gate arms with bearings for trunnion pins. Principal stationary and embedded gate members consist of trunnion pins, anchor girders or castings, anchor bolts, and bottom sill and wall plates.

B. The gate leaf and arms for large units are fully enclosed, primarily for
strength reasons, secondarily for added protection against spilling waves,
overflowing debris, and snow and ice loads. The gate interior is vented
and made accessible through covered manholes which are necessary for
field erection, inspection, and Servicing Subsequent to installation. Trunnion
pins are fully enclosed to prevent dust, Sand, or excessive moisture from
entering between the finished surfaces of steel pins and bronze bushings.

To assure trouble-free operation and proper functioning of the seals, precise alinement of arm bearings, bottom Sill, and wall plates, is important. In certain instances, the gate anchorages are designed to permit realinement of trunnion bearings subsequent to installation, in case any unequal pier settlement occurs which would require such corrective procedures. (See Figure 34.)

The location of the pin bearing and anchorage must be outside the discharge flow nappe to permit free flow. The rubber side seals are constructed and mounted on the gate leaf in such a manner as to cause minimum frictional resistance against the wall plates, and to permit longitudinal gate expansion or contraction without sacrificing seal tightness. Freedom for lateral gate movement is, however, limited by the established clearance between the guide rollers and wall plates.

The discharging gate is free from drawdown effect or “flutter” as long
as gate contours at the bottom will convert rapidly from static to velocity
head. The extended sharp-edged bottom lip compels the water to spring
free and clear from the bottom enclosure of the gate for any opening. The
hydraulic behavior of the discharging water is good and the coefficient of
discharge relatively high.

The gates are closed by force of gravity, thereby permitting the use of steel ropes for hoisting. In certain instances of high-head installations, fixed links for hoisting are advantageous. (See Figure 35.)

If severe winter conditions cause ice thrust in front of the gates, the leaf
members must be sufficiently reinforced to absorb the thrust. In case
operation of gates under such conditions is required, it will be necessary
to keep ice clear from the face of the structure. This can be effectively
accomplished by agitating the water in front of the gate with compressed
i. and installing electrical resistance heat elements near wall plates
and Seals.

C. The resultant water pressure on large structures is a function of horizontal and positive and negative vertical forces. The component forces are separately computed by derived mathematical formulas. For preliminary design analysis, it is usual to evaluate the resultant water


pressure by graphical methods. This can be rapidly and accurately
accomplished by dividing the face of the gate into a series of small incre-
ments and assuming the water loads on these increments to be concentrated
at the center of gravity of each pressure area. The pressure distribution
on the gate, when raised nearly to full opening, may be determined by
analogy from previous designs or by piezometric model tests. These
tests are covered in other parts of this Volume.

D. Contrary to the usual practice in the design of standard canal gates, the Design of larger type structure is not provided with a corrosion allowance. In the Gate Leaf & majority of applications, an opportunity to service the units internally and Seals externally is provided. The upstream skin plate on large-type units is usually supported by continuous horizontal stiffeners. The bending stress of the continuous member, consisting of skin plate and stiffener, must be • combined with the primary plate stress to obtain the maximum equivalent design stress. Secondary stresses due to weight reactions on the bottom part of the skin plate must also be considered.

The skin plate loads are transmitted through the intermediate diaphragms into the main girders, which are supported by the arm diaphragms. The girders are designed in a conventional manner to resist moments and shears created by the hydraulic loads. The intermediate diaphragm plates are investigated for possible buckling due to the concentrated loads on relatively thin plates. The arm diaphragms are investigated for stresses : by distributed hydraulic loads and concentrated loads from the glrders.

In order to reduce seal friction and hoisting effort, end seals are
brass clad and slide over the stainless-steel wall plates. Submerged
high-head radial gates are additionally equipped with a brass-clad top
seal, mounted on a head-wall structure. This seal makes sliding contact
with the faceplate. The high-head radial gate leaf is very similar in design
and construction to the large-type unit except for the top sealing device on
the upper edge.

The bottom sill and side wall plates are grouted in place prior to the erection of the gates and these plate faces must be flush with the surface of the concrete.

E. The geometric location of gate arms must be such as to obtain approximately Design equal strut loads. The individual arm struts are primarily loaded as a of Gate Arms column but also carry high secondary stresses induced by the angular rotation of the joints at the gate leaf and arms. Weight stresses of the relatively long arms are reduced by the introduction of struts at the midpoint of the span. The slenderness ratio, 1/r, of the individual strut is limited to 100. The converging arm members are usually welded to a cast-steel hub containing the self-lubricating bushing. Whenever possible, the arm members are fully enclosed to prevent ice, Snow, or debris from piling into pockets.

On gate structures having extended arms for concrete balancing weights,
the arms must be designed to also absorb major bending and shear stresses.

F. Arm loads are transmitted through bearings into protruding trunnion pins, Pin Anchorage and, depending on pier conditions mentioned previously, to heavy anchor girders or castings which are grouted in place. (See Figures 33 and 34.) On high-head gate installations, the anchorage consists of cast-steel hinges mounted on adjustable pedestals. (See Figure 35.) The trunnion pins must be investigated for major bending and shear stresses and secondary torsional shear stresses.

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Horizontal and vertical pin anchorage component forces are further absorbed by heavy anchor bolts which are mounted in two principal directions. These anchor bolts are of sufficient length to develop full bond strength and are formed to distribute the respective loads in the mass concrete. Large-diameter anchor bolts are provided with upset ends. The maximum anchor bolt stresses depend on the load distribution caused by the gate during the entire cycle of operation.

The successful operation of gates and seals depends to a great extent on accurate alinement of pin anchorages and bottom sill and side wall plates. Therefore, ample adjustment provisions prior to, as well as during gate erection are necessary

Drum gates afford a movable crest in a spillway, thus permitting either an
increase in the active storage capacity of the reservoir simultaneously with
an increased operating head at the turbines in the power plant, or the drawing
down and regulation of the reservoir in case of impending floods. Since the
flow is over the top of the gate, the discharge height is not limited and trash
and debris can flow over without difficulty. The drum gate is operated by
reservoir pressure, thus eliminating the need of hoists or external power
Supply. The control is either automatic, manual, or remote electric. A
general installation drawing of a 100- by 18-foot drum gate is shown in
Figure 36.


The gate is a buoyant vessel and is anchored through hinges to the upstream
lip of the weir. The reservoir water, when allowed to flow into the recess
chamber, will cause pressure on the bottom face of the gate, thereby
rotating it slowly upward about the hinge-pin until raised. The fully
lowered gate occupies the recess chamber of the spillway, with the upper
gate tip resting on the downstream side of the concrete ledge. The contour
of the upstream face of the gate conforms with the ogee crest outline, thus
insuring a high discharge coefficient when the gate is fully open or in the
down position.

Conventional drum gate sizes vary from 12 to 28 feet nominal height and the ratio for gate breadth to height usually ranges from 4 to 7. Ordinarily, the range of arc of rotation varies from 67 to 75 degrees.

Basically, the shape of the crest contour of the lowered drum gate is
patterned very similarly to that of the lower surface of water flowing
freely over a sharp-crested weir.

The discharge capacity of the fully lowered gate is computed from the

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C. The structural-steel gate, when floated, is loaded by water pressure and Water Loads & auxiliary forces. The gate will be held in any position as long as all forces Auxiliary are in equilibirum and satisfy the fundamentals of statics: Forces

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The composite curvature of the upstream face does not allow a direct Solution for the upstream loading. It is therefore recommended that the resultant water load, R1, on the upstream face of the gate be computed through a combined analytical and graphic method, assuming that the curvature is composed of a series of straight-faced panels or elements loaded in a trapezoidal manner. By Selecting the element length 3.2 feet and the element width 1 foot, the panel load can then be determined quite Speedily and accurately by plotting the gate curvature and head ordinates to scale.

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The value p should be determined for each element of length of the upstream face of the gate, and the evaluation of the resultant load R1 required simply a graphic integration.

For intermediate gate positions and actual overflow, the true pressure

heads of the element loads are experimentally obtained through piezometer

tests applied on a hydraulic model and plotted in the form of curves for

various gate positions. Through interpolation of values, the resultant

water load R1 can therefore be determined for any gate position and any ... quantity of discharge.

D. By summation of moments about the hinge-pin center, the gate-seat Reactions on

reaction can be directly evaluated: Hinge-Pin & Gate-Seat

R1a + Wb + STc - R2d = 0 Anchorages

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