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RestrainingRestrainingThrust ForcesThrust ForcesThrust ForcesThrust Forces
Forces Causing ThrustForces Causing Thrust
Static forcesStatic forces
(Internal pressure)(Internal pressure)
Dynamic forcesDynamic forces
(Fluid velocity) (Fluid velocity)
Thrust ForceThrust Force
Straight RunStraight Run
PAPA PAPA
Thrust ForceThrust Force
BendBend
2PA Sin(2PA Sin(/2)/2)
Resultant Thrust: 90Resultant Thrust: 90°° BendBend
NominalNominal
Pipe SizePipe Size
(i )(i )
ThrustThrust
ForceForce
(lb )(lb )
Pressure at 150 psiPressure at 150 psi
(in)(in) (lbs)(lbs)
66 7,9327,932
1212 29,03029,030
2424 110,901110,901
3636 244,396244,396
4848 429,956429,956
6464 718,506718,506
22
Restraining TechniquesRestraining Techniques
Thrust blocksThrust blocks
Restrained joint systemRestrained joint system
Tie rodsTie rods
Combined systemsCombined systems
Types of Thrust BlocksTypes of Thrust Blocks
BearingBearinggg
GravityGravity
Bearing Thrust BlockBearing Thrust Block
Undisturbed SoilUndisturbed SoilUndisturbed SoilUndisturbed Soil Bearing AreaBearing AreaBearing AreaBearing Area
4545°°4545°°
Bearing Area (ftBearing Area (ft22) =) =Bearing Area (ftBearing Area (ft22) =) =Safety Factor • Thrust Force (lbs)Safety Factor • Thrust Force (lbs)Safety Factor • Thrust Force (lbs)Safety Factor • Thrust Force (lbs)
Bearing Capacity of Undisturbed Soil (lbs/ftBearing Capacity of Undisturbed Soil (lbs/ft22))Bearing Capacity of Undisturbed Soil (lbs/ftBearing Capacity of Undisturbed Soil (lbs/ft22))
Soil Bearing Strength SSoil Bearing Strength SBB
SoilSoil SSB B (lb/ft(lb/ft22))
MuckMuck 00
Soft claySoft clay 1,0001,000Soft claySoft clay 1,0001,000
SiltSilt 1,5001,500
Sandy siltSandy silt 3,0003,000
SandSand 4,0004,000
Sandy claySandy clay 6,0006,000
Hard clayHard clay 9,0009,000
Bearing Thrust BlockBearing Thrust Block
HHHHtt
hh
h h ≤≤ 1/2H1/2Htt
TT
A = hb =A = hb =TTSSBB
(S(Sff))
Bearing Block ConstructionBearing Block Construction
RightRight WrongWrong
4545°°4545°°
TT TT
33
Thrust RestraintThrust Restraint
Gravity Thrust BlockGravity Thrust Block
Gravity Block Size (ftGravity Block Size (ft33) =) =Gravity Block Size (ftGravity Block Size (ft33) =) =Safety Factor • Thrust Force (lb)Safety Factor • Thrust Force (lb)Safety Factor • Thrust Force (lb)Safety Factor • Thrust Force (lb)
Density of Block Material (lb/ftDensity of Block Material (lb/ft33))Density of Block Material (lb/ftDensity of Block Material (lb/ft33))
Gravity BlockGravity BlockGravity BlockGravity Block
44
Restrained Joint Force SystemRestrained Joint Force System
PAPA
PA Tan(PA Tan(/2)/2)
FFff + ½ R+ ½ Rss
L =L =
LL
FFff
RRss
PA Sin(PA Sin(/2)/2)
[F[Fff + ½ R+ ½ Rss]LCos(]LCos(/2)/2)
LL
Mechanical Joint Retainer GlandsMechanical Joint Retainer Glands
SetSet--ScrewScrewMechanical JointMechanical JointRetainer GlandRetainer Gland
WedgeWedge--actionactionMechanical JointMechanical JointRetainer GlandRetainer Gland
Restrained JointsRestrained Joints
55
Designing Thrust SystemsDesigning Thrust Systems
Thrust Restraint BrochureThrust Restraint Brochure
A brochure outlining design theoryA brochure outlining design theoryand a design aid of restrainedand a design aid of restrained
joint systems for ductile iron pipe.joint systems for ductile iron pipe.
Restrained Joint Force SystemRestrained Joint Force System
PAPA
PA Tan(PA Tan(/2)/2)
FFff + ½ R+ ½ Rss
L =L =
LL
FFff
RRss
PA Sin(PA Sin(/2)/2)
[F[Fff + ½ R+ ½ Rss]LCos(]LCos(/2)/2)
LL
Restrained Length Dependant UponRestrained Length Dependant Upon
Pipe sizePipe size
Type of fittingType of fitting
Internal pressureInternal pressure
Depth of coverDepth of cover
Soil characteristicsSoil characteristics
Laying conditionsLaying conditions
Suggested Values for Soil PropertiesSuggested Values for Soil Propertiesand Reduction Constantand Reduction Constant
Soil Soil DesignationDesignation
Soil DescriptionSoil Description
(deg)(deg)ff
CCss
(psf)(psf)ffcc
γγ(deg)(deg)
K K nn
A21.50 Laying A21.50 Laying ConditionCondition
2*2* 33 44 55
Clay 1Clay 1Clay of medium to low plasticity, Clay of medium to low plasticity, LL<50, <25% coarse particlesLL<50, <25% coarse particles
[CL & CL[CL & CL ML]ML]00 00 300300
.50.50
.80.809090 .20.20 .40.40 .60.60 .85.85
[CL & CL[CL & CL--ML]ML] .80.80
CohCoh--grangranCohesive granular soils,Cohesive granular soils,
> 50% coarse particles [GC & SC]> 50% coarse particles [GC & SC]2020
.40.40
.65.65200200 .40.40 9090 .40.40 .60.60 .85.85 1.01.0
Sand SiltSand SiltSand or gravel w/silt,Sand or gravel w/silt,
> 50% coarse particles [GM & SM]> 50% coarse particles [GM & SM]3030
.50.50
.75.7500 00 9090 .40.40 .60.60 .85.85 1.01.0
Good SandGood SandClean sand, >95% coarse particles, Clean sand, >95% coarse particles,
[SW & SP][SW & SP]3636
.75.75
.80.8000 00 100100 .40.40 .60.60 .85.85 1.01.0
Consult Table 3 of thrust brochure for pertinent notes.Consult Table 3 of thrust brochure for pertinent notes.
Laying ConditionsLaying Conditions
Type 1Type 1
Type 4Type 4
Type 2Type 2 Type 3Type 3
Type 5Type 5
Thrust Restraint Thrust Restraint -- ResearchResearch
12” MJ Pipe and fittings12” MJ Pipe and fittingswith DI retainer glandswith DI retainer glands
MovementMovementsensingsensing
Measurement TrenchMeasurement Trench
sensingsensingprobesprobes
Railroad CrossRailroad CrossTie BulkheadTie Bulkhead
MeasuringMeasuringFrameFrame
ProbeProbe
BackfilledBackfilled ApproximatelyApproximately3’ of cover3’ of cover
Bedding compactionBedding compactionvaried during testvaried during test
Section “ASection “A--A”A”
66
Designing Thrust SystemsDesigning Thrust Systems
t i
Thrust Restraint Computer ProgramThrust Restraint Computer Program
A computer program to aid inA computer program to aid inthe design of restrained jointthe design of restrained jointsystems for ductile iron pipe.systems for ductile iron pipe.
Table BTable B--55
A21 50A21 50 L i C ditiL i C diti
22 33 44 55
ff 0.400.40 0.650.65 0.650.65 0.650.65
ff cc 0.400.40 0.400.40 0.400.40 0.400.40
KK nn 0.400.40 0.600.60 0.800.80 1.001.00
A21.50 A21.50 –– Laying ConditionsLaying ConditionsSoil Type: CohSoil Type: Coh--grangranSoil ParametersSoil Parameters
CCss
= 20 degrees= 20 degrees= 200 psf= 200 psf= 90 pcf= 90 pcf
SizeSize
(in)(in)
DepthDepth
(ft)(ft)
A21.50 A21.50 –– Laying ConditionsLaying Conditions
22 33 44 55
RestrainedRestrained
Length (ft)Length (ft)
RestrainedRestrained
Length (ft)Length (ft)
RestrainedRestrained
Length (ft)Length (ft)
RestrainedRestrained
Length (ft)Length (ft)
3030 2.52.5 97 97 (112)(112) 69 69 (79)(79) 56 56 (62)(62) 50 50 (55)(55)
3030 3.03.0 91 91 (105)(105) 65 65 (74)(74) 52 52 (58)(58) 47 47 (51)(51)
3030 4.04.0 81 81 (93)(93) 57 57 (65)(65) 46 46 (51)(51) 41 41 (45)(45)
3030 6.06.0 66 66 (76)(76) 46 46 (52)(52) 37 37 (41)(41) 33 33 (36)(36)
3030 8.08.0 56 56 (64)(64) 38 38 (44)(44) 31 31 (34)(34) 28 28 (30)(30)
3030 10.010.0 48 48 (56)(56) 33 33 (38)(38) 26 26 (30)(30) 24 24 (26)(26)
Horizontal Bend MultiplierHorizontal Bend Multiplier
Tan(Tan(/2)/2)
9090°° 1 0001 0009090 1.0001.000
4545°° 0.4140.414
2222½½°° 0.1990.199
1111¼¼°° 0.0980.098
Vertical Down BendVertical Down Bend
/2/2 2PA Sin(2PA Sin(/2)/2)
FFss
FFss
PA Tan(PA Tan(/2)/2)
FFff
L =L = SSff
LL
TeeTee
PAPAbb
LLrr
PAPAbb --1/2 R1/2 RssLLrr
(F(Fff ))bb
LLbb == SSff
LLbb
LLbb(F(Fff))bb
Extend Restrained Joints at:Extend Restrained Joints at:
CasingsCasings
Bridge crossingsBridge crossingsBridge crossingsBridge crossings
Aboveground applicationsAboveground applications
Poor soil conditionsPoor soil conditions
Closely located fittingsClosely located fittings
77
Combined Horizontal BendsCombined Horizontal Bends
RRssRRss
2PA Sin(2PA Sin(/2)/2) 2PA Sin(2PA Sin(/2)/2)
FFffFFff
2PA Tan(2PA Tan(/2)/2)
FFf f ++ 1/2R1/2Rss
LL11 == SSff -- LL
LL11 LL11
LLLL
KnownKnown KnownKnown
Vertical OffsetVertical Offset
FFff
2PA Tan(2PA Tan(/2)/2)
FFf f ++ 1/2R1/2Rss
LL22 == SSff -- LL
2PA Sin(2PA Sin(/2)/2)
FFff
LL11 LL
LL22LL
RRss
2PA Tan(2PA Tan(/2)/2)
FFff
LL11 == SSff -- LL
2PA Sin(2PA Sin(/2)/2)
Combined Vertical Equal Angle OffsetsCombined Vertical Equal Angle Offsets
FFffFFff
2PA Tan(2PA Tan(/2)/2)
FFff
LL11 == SSff -- LL
LL
LL11LL11
LL
LLLL
88
Thrust Restraint Thrust Restraint -- ClosuresClosures
LL
LL22
ClosureClosure
LL11LL11
LL22
ClosureClosure
Thrust Restraint Thrust Restraint –– Deflected JointsDeflected Joints
Second unrestrained jointSecond unrestrained jointbegin deflectbegin deflect
First unrestrained jointFirst unrestrained jointdo not deflectdo not deflect
Horizontal Bend / Vertical Up BendHorizontal Bend / Vertical Up Bend
PAPA
LL
PA Tan(PA Tan(/2)/2)
FFff + ½ R+ ½ Rss
L =L = SSff
FFff
RRss
PA Sin(PA Sin(/2)/2)
[F[Fff + ½ R+ ½ Rss]LCos(]LCos(/2)/2)
LL
TieTieRodsRods
99
Calculating Number of Tie RodsCalculating Number of Tie Rods
F = SAF = SA
N = N = SSff TT(X or Y)(X or Y)
FFFFWhere:Where:
F = Force Developed per Rod (lbs.)F = Force Developed per Rod (lbs.)
S = Tensile Strength of Rod Material (psi)S = Tensile Strength of Rod Material (psi)
A = Cross Sectional Area of Rod (in.A = Cross Sectional Area of Rod (in.22))
N = Number of Rods RequiredN = Number of Rods Required
TT(X or Y)(X or Y) = Thrust Force Component (lbs.)= Thrust Force Component (lbs.)
SSff = Safety Factor (usually 1.5)= Safety Factor (usually 1.5)
CombinedCombinedSystemsSystems
DUCTILE IRON PIPEDUCTILE IRON PIPETHE RIGHT DECISIONTHE RIGHT DECISION
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