HYDROLOGICAL DESIGN OF DESILTING TANK

   

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Design Discharge
Velocity in the Desilting Tank
Assumed Average Depth
Width Required
Width Adopted
Size of water conductor from Inlet to Desilting Tank
Length required for Hopper
Total required length
Width
Depth
(B)

HYDROLOGICAL DIMENSIONS OF TANK
(a)

Tank Full and Soil Dry

Since the Bending moment due to saturated soil near the water face will be more than that due to dry soil
Hence, this case need not to be considered
(b)

TANK IS FULL AND SOIL SATURATED

NET B.M.

BM AT LOWER EDGE

(a)

RESULTANT OF WATER PRESSURE & Wt OF WATER
(b)

VERTICAL COMPONENET OF SELF Wt OF INCLINED WALL

NET BM

(c)

TANK IS FULL AND SOIL IS DRY

Since the B.M due to saturated soil near the water face will more than due to dry soil

(d)

Tank is full and no earth pressure Prominant case in the Present Situation critical condition at B' is considered
It is assumed that soil may be present up to level B

NET B.M.

(e)

TANK IS EMPTY AND SOIL SATURATED

NET B.M.

(f)

TANK IS EMPTY AND SOIL DRY

The BM due to dry soil will be less than for Saturated soil so case is not considered

D)

CALCULATION FOR REINFORCEMENT

MAX. B.M.

DEPTH REQUIRED

DEPTH PROVIDED

OVERALL DEPTH

STEEL REQUIRED

STEEL REQUIRED

DIA OF BAR

SPACING REQUIRED

SPACING OF BAR PROVIDED BOTH FACES

STEEL PROVIDED

STEEL PROVIDED >= MINIMUM STEEL REQUIRED

Curatilment of Reinforcement where 50% Reinforcement required

Asth/AstH

either 12F or 400mm whicher is greater

ACTUAL LENGTH OF CURTAILMENT

LENGTH OF BAR FROM BASE

DISTRIBUTION STEEL

DIA OF BAR

STEEL REQUIRED

SPACING REQUIRED

SPACING PROVIDED

STEEL PROVIDED

STEEL PROVIDED >= MINIMUM STEEL REQUIRED
E)

CHECK FOR STABILITY

WEIGHT OF DESILTING TANK

In concrete structure Buoyancy Through Pore Pressure is limited to 15% of Full Buoyancy on submerged portion

15% OF BUOYANCY

Wt DUE TO BUOYANCY < Wt OF DESILTING TANK

DESIGN OF ONE WAY SLAB:-

INPUT DATA

NO. OF PANELS

LENGTH

EFFECTIVE SPAN LEAST OF TWO

CENTRE TO CENTRE SPACING

EFFECTIVE SPAN=CLEAR SPAN+ EFFECTIVE DEPTH

WIDTH OF PANEL

SOLUTION:-

LOAD CALCULATIONS:

FROM DEFLECTION CRITERIA

ASSUME OVERALL THICKNESS OF SLAB =
EFFECTIIVE THICKNESS+ EFFECTIVE COVER

DEAD LOAD OF SLAB

IMPOSED LOAD

FACTORED TOTAL LOAD ON SPAN PER METER WIDTH

ULTIMATE MOMENT

SHEAR

CALCULATION FOR DEPTH OF SLAB:-

EFFECTIVE DEPTH

ASSUME OVER ALL DEPTH OF SLAB

EFFECTIVE DEPTH

If d>dreq than section is under reinforced

CALCULATION FOR SHEAR:

SHEAR STRESS tv

Percentage of Steel

FOR 120 MM DEPTH

check for shear

CALCUATIONS FOR REIFORCEMENT:

Area of Steel Ast

DIA OF BARS USED

AREA OF ONE BAR

SPACING OF BARS REQUIRED

PROVIDE SPACING OF BARS

AERA OF STEEL REQUIRED

STEEL PROVIDED

Ast at support

CHECK FOR CONTROL OF CRACK

MINIMUM % AGE OF STEEL

AREA OF STEEL

MAXIMUM DIA OF BAR

DIA OF BAR PROVIDED

MAX SPACING

SPACING PROVIDED

RECHECK FOR SHEAR

100* Astprov/bd

Shear Stress

SHEAR STRESS

SAFE IN SHEAR

CHECK FOR DEFLECTION

BASIC SPAN/ DEPTH RATIO

Percentage of Steel

steel stress of Service load fs

Modification Factor kt

(l/d)max

(L/d)provided

SAFE IN DEFLECTION

DISTRIBUTION STEEL

DISTRIBUTION STEEL

DIA OF BARS USED

AREA OF ONE BAR

SPACING OF BARS

PROVIDE SPACING OF BARS

STEEL PROVIDED

DESIGN OF BOTTOM SLAB

AS PER SITE THE BOTTOM PORTION COMPRISES
OF HARD ROCY STRATA SO THICKNESS OF
BOTTOM SLAB PROVIDED IS

THE MINIMUM REINFORCMENT

DIA OF BAR

SPACING OF BAR

SPACING OF BAR PROVIDED

STEEL PROVIDED