View
239
Download
2
Category
Preview:
Citation preview
8/11/2019 Design of Thrust Blocks_London_Ted
1/21
JOINT RESTRAINTJOINT RESTRAINT
of EngineersKansas City District
PRESSURIZED PIPEPRESSURIZED PIPE
Presented by:
Ted London, PE
US Army Corps of EngineersKansas City District
8/11/2019 Design of Thrust Blocks_London_Ted
2/21
8/11/2019 Design of Thrust Blocks_London_Ted
3/21
How Thrust is Generatedof EngineersKansas City District
Equilibrium
8/11/2019 Design of Thrust Blocks_London_Ted
4/21
How Thrust is Generatedof EngineersKansas City District
What changes equilibrium:
Transient Pressure (surge)
Velocit Head
Changing direction of flow
Changing diameter of pipe
Thermal changes
8/11/2019 Design of Thrust Blocks_London_Ted
5/21
How Thrust is Generatedof EngineersKansas City District
Changes in equilibrium are developed at:
Vertical bends
Dead ends
Tees
Wyes
Reducers
Fire Hydrants
8/11/2019 Design of Thrust Blocks_London_Ted
6/21
How Thrust is Generatedof EngineersKansas City District
8/11/2019 Design of Thrust Blocks_London_Ted
7/21
How Thrust is Generatedof EngineersKansas City District
8/11/2019 Design of Thrust Blocks_London_Ted
8/21
Bearin Ca acitof EngineersKansas City District
versus
Passive Resistance
BEARING CAPACITY FAILURE: The thrust generated
exceeds the bearing capacity of the soil times the bearing
PASSIVE RESISTANCE FAILURE: The thrust
generated slides a wedge of soil
8/11/2019 Design of Thrust Blocks_London_Ted
9/21
Bearin Ca acitof EngineersKansas City District
8/11/2019 Design of Thrust Blocks_London_Ted
10/21
8/11/2019 Design of Thrust Blocks_London_Ted
11/21
thrust block by bearing pressure (AWWA m23)
Known Internal ressure of EngineersKansas City District
Pipe outside Diamter D 9.050in
Deflection angle 45
Depth to bottom of thrust block h 7ft
Safety Factor Sf 1.5
Soil Bearing B 1500psf
Solve
Internal Area A D
2
4
Unbalanced Force T 2 P A sin
2 180
Ab TSf
B
b
Passive resistance thrust block design is required if the height of the thrust block is
greater than 1/2 * depth.
In the above example, thrust block has a height of 2 and length of 4. 2 ft tall is less than
three (1/2*7)
8/11/2019 Design of Thrust Blocks_London_Ted
12/21
thrust block by Passive Resistance (AWWA m23)
Known
Internal pressure P 150psiof EngineersKansas City District Pipe outside Diamter D 9.050in
Pipe Deflection angle 45
Safety Factor Sf 1.5
Soil Bearing B 1500psf
Unit Wei ht of Soil 110 cfSoil Internal Friction angle 30
Cs 0psf
Internal AreaD
2
4
Unbalanced Force T 2 P A sin
2 180
Nd tan 45
2
180
2
Ab TSf
h Nd 2 Cs Nd.5
Ab
In the above example, a height of 2 and length of 4.5 ft. 2 ft tall is less than three(1/2*4.5)
8/11/2019 Design of Thrust Blocks_London_Ted
13/21
Tables should have correct bearing
of EngineersKansas City District
8/11/2019 Design of Thrust Blocks_London_Ted
14/21
8/11/2019 Design of Thrust Blocks_London_Ted
15/21
of EngineersKansas City District
Ductile Iron Bolted
8/11/2019 Design of Thrust Blocks_London_Ted
16/21
8/11/2019 Design of Thrust Blocks_London_Ted
17/21
Types of Restrained Joints
of EngineersKansas City District
and
How The Work
8/11/2019 Design of Thrust Blocks_London_Ted
18/21
Errors and OmissionsErrors and Omissionsof EngineersKansas City District
Not considering passive resistance
Over-estimating bearing capacity of soil
Use same table over and over without thinking
Poor installation
Not considering saturated soil
required to resist the force
8/11/2019 Design of Thrust Blocks_London_Ted
19/21
Results of Errors
of EngineersKansas City District
sengagemen o p pes
Displacement of soil Wedges
Poor construction blamed in lieu of design
Root cause ma not be determined
8/11/2019 Design of Thrust Blocks_London_Ted
20/21
References
of EngineersKansas City District
AWWA M23: PVC Pipe Design and Installation
AWWA M41: Ductile Iron Pipe and FittingsDuctile Iron Pipe Research Association (DIPRA)
EBAA Iron
American Ductile Iron Pipe Co. (ACIPCO)
8/11/2019 Design of Thrust Blocks_London_Ted
21/21
of EngineersKansas City District
Questions
Recommended