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Reinforced Concrete Pipe. Structural Design Overview Jason Kruger CPAM Engineer. RCP strength design. Concrete pipe strength Bedding Factor, B f Fill height Traffic loads. RCP strength design. Pipe Classes Class II – least strong Class III – stronger than Class II
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Reinforced Concrete Pipe Structural Design Overview Jason Kruger CPAM Engineer
RCP strength design • Concrete pipe strength • Bedding Factor, Bf • Fill height • Traffic loads
RCP strength design • Pipe Classes • Class II – least strong • Class III – stronger than Class II • Class IV – stronger than Class III • Class V - strongest
RCP manufacturing • Prescriptive requirements (C76, M170) • Steel reinforcing cage • Area • Yield strength • Concrete strength • Wall thickness
Three-edge bearing test (3-EB) • 3-EB is a proof test • Obtain piece of pipe from production run • Insert pipe in 3-EB test machine • Load it to pre-determined value • Inspect loaded pipe for compliance
Three-edge bearing test (3-EB) • 3-EB history • “Gold Standard” • Since 1930’s • Relates pipe strength to the bedding factor, Bf
Three-edge bearing test (3-EB) • 3-EB test load is dependent on • Pipe class • Inside diameter • Pipe length • Loading condition (D.01 or Dult)
Three-edge bearing test (3-EB) • D-Load • Each pipe class is associated with a specific “D-Load” • Definition: • “The D-Load is the supporting strength of a concrete pipe loaded under three-edge bearing test conditions, expressed in pounds per linear foot per foot of inside diameter”
Three-edge bearing test (3-EB) • D-Load • There are two D-Loads that define the strength of a given concrete pipe
Three-edge bearing test (3-EB) • D-load.01 (or simply D.01) “the maximum three-edge bearing test load supported by a concrete pipe before a crack occurs having a width of .01” measured at close intervals throughout a length of at least one foot, expressed as D-load”
Three-edge bearing test (3-EB) • D-loadult (or simply Dult) “the maximum three-edge bearing test load supported by a concrete pipe, expressed as D-load” NOTE: D.01is the basis for concrete pipe strength design
Three-edge bearing test (3-EB) • D-Loads for each pipe class
Three-edge bearing test (3-EB) • 3-EB test load – SAMPLE CALCULATION • Test pipe: 36”i.d.Class III • Required D.01 = 1,350 • Total 3-EB test load = Pipe i.d.X Length X D.01 = (36/12) X 8 X 1350 = 32,400 lbs
Three-edge bearing test (3-EB) • 3-EB test: passing criteria: • Cracks are no wider than .01” • .01” cracks less than 12” in length are considered passing
ASTM C76 - Tested pipe allowable for project
State crack specifications assessed