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27_HWKTTE 4004c

# 27_HWKTTE 4004c - 18 E Rated Hammer Energy Per Blow(ft-lb...

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17 ) 1 . 0 ( + = s F h W P r a (3-3) where P a Allowable Pile Load W r Hammer Ram Weight h Hammer Stroke (the distance the hammer falls) F Factor of Safety s Pile Set (penetration) per Blow in Inches Wellington (1888) recommended using a Safety Factor of 6.0. Modified Engineering News Record formula In 1961, the Michigan Highway Department (Housel, 1966) performed a series of pile driving tests with the objective of evaluating the accuracy of the ENR formula. After evaluating 88 piles, the investigators found that the ENR formula overpredicted the pile capacities by a factor of 2 to 6. The findings mean that piles designed with a SF of 6 will have a real factor of safety of 1 and 3. Based on their results, the Michigan Highway Department developed the Modified Engineering News Formula: ) )( 1 . 0 ( ) ( 0025 . 0 2 P r P r a W W s W e W E P + + + = (3-4) where P a Allowable Pile Load (kips)

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Unformatted text preview: 18 E Rated Hammer Energy Per Blow (ft-lb) W P Weight of Pile plus Driving Appurtenances (lb) W r Weight of Hammer Ram (lb) s Pile Set (in/blow) e Coefficient of Restitution FDOT The Florida Department of Transportation under specification 455-3.3 (1991) recommends the following bearing formula (FDOT, 1991). P S E R 01 . 1 . 2 + + = (3-5) where R Safe Bearing Value in Tons P Weight of Pile as Driven, in Tons S Average Penetration per Blow, in Inches E Energy per Blow of Hammer, in Foot-Tons The last formula was used for concrete piles, composite concrete-steel piles and steel piles. The bearing capacity obtained using the latter FDOT approach either coincided or exceed the design capacity (suggested FS = 1.0)....
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27_HWKTTE 4004c - 18 E Rated Hammer Energy Per Blow(ft-lb...

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