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Page 1
IDOT Pile Design Training Handout
Training on Bridge Pile Design by Spreadsheet
April 2021
Michael Nop, PE 515-239-1233 [email protected] Iowa DOT, Bridges and Structures Bureau
Page 2
TABLE OF CONTENTS County Problem 1A J30 - Integral Abutment - HP10x42, Modified IDOT ENR Formula, Cohesive Soil 3 County Problem 1B J30 - Integral Abutment - HP10x42, WEAP, Cohesive Soil, Setup 8 County Problem 2 H30 - Integral Abutment - HP10x57, WEAP, Cohesive Soil, Downdrag, Bedrock 10 County Problem 3 H30 - Pile Bent - HP14x73, WEAP, Non-cohesive Soil, Scour 16 Appendices
A. Friction and End Bearing Soil Charts 22 B. Soil Categories 24 C. Recommended Pile Penetration 25
DISCLAIMER: Neither the State of Iowa, the Iowa Department of Transportation nor their employees make any representations or warranties, express or implied, with respect to the use of or reliance on the data provided herewith, regardless of its format or means of transmission. There are no guarantees or representations to the user as to the accuracy, currency, completeness, suitability or reliability of this data for any purpose. THE USER ACCEPTS THE DATA "AS IS" AND ASSUMES ALL RISKS ASSOCIATED WITH ITS USE. The Iowa Department of Transportation assumes no responsibility for actual, consequential, incidental, special or exemplary damages resulting from, caused by or associated with any user's reliance on or use of this data, even if appraised of the likelihood of such damages occurring.
Page 3
County Problem 1A J30 - Integral Abutment - HP10x42
Modified IDOT ENR Formula, Cohesive Soil J30-06 Continuous Concrete Slab (CCS) Bridge Standards (https://iowadot.gov/bridge/standards/english/j30-06.pdf)
• 30’ roadway width • 0° skew • 140’ long bridge • 3 Spans: 42.5’ – 55’ – 42.5’ • Integral abutment • Pile type: HP10x42 • 10’ prebore required • Pu = 92.3 kips per pile • Generalized Soil Category: Cohesive • Construction Control: Modified IDOT ENR Formula
Page 4
See blow-up on next page.
ALL PILING HP10x42.
Page 5 Standard Sheet J30-34-06
Note: The Structural Resistance Level 1 (SRL-1) limit from BDM Table 6.2.6.1-1
(https://iowadot.gov/bridge/policy/06-02-00PileLRFD.pdf) for an HP10x42 is 179 kips of nominal resistance. The factored resistance is (0.60)*(179 kips) = 107.4 kips which should be and, in fact, is greater than Pu = 92.3 kips.
Standard Sheet J30-34-06
Note: The above statement is in conflict with the statement in the J-standards on sheet J30-01A-6 which
prohibits the use of these standards when rock is less than 15 feet from the bottom of the footing – see next page. Note that both statements conflict with the 2020 BDM update in BDM Article 6.1.6.1.1.1 which requires 34 feet from the bottom of the footing to the top of the rock for an integral abutment with HP10x42 piles and 10 feet of prebore if no further analysis is performed (https://iowadot.gov/bridge/policy/06-01-00SubsLRFD.pdf).
Pu = (646 k)/(7 piles) = 92.3 kips per pile
Page 6
Standard Sheet J30-01A-06, GENERAL NOTES
Note: The above statement is in conflict with the 2020 BDM update in BDM Article 6.1.6.1.1.1 which
requires 34 feet from the bottom of the footing to the top of the rock for an integral abutment with HP10x42 piles and 10 feet of prebore if no further analysis is performed (https://iowadot.gov/bridge/policy/06-01-00SubsLRFD.pdf). BDM Table 6.1.6.1.1.1-1 contains the full range of values for various conditions.
A reference to CADD note E177 is made in the plan notes above, but this note is no longer available in the BDM and is not required in the plan set.
Page 7
Soil Profile at West Abutment
Ftg Bot Elev 933
Prebore Elev 923
10’ prebore
Final ground surface
Existing ground surface
11’
Surface Elev 937
30’
Soft Silty Clay
Silty Sand
Firm Glacial Clay
Very Firm Glacial Clay
2’
9’
10’
Layer Elev 917
Layer Elev 907
Layer Elev 926
Fill
N = 4
N = 6
N = 12
N = 20 35’
Boring Bot Elev 872
SPT N values are in units of blows per foot
4’
Page 8
County Problem 1B J30 - Integral Abutment - HP10x42
WEAP, Cohesive Soil, Setup J30-06 Continuous Concrete Slab (CCS) Bridge Standards (https://iowadot.gov/bridge/standards/english/j30-06.pdf)
• 30’ roadway width • 0° skew • 140’ long bridge • 3 Spans: 42.5’ – 55’ – 42.5’ • Integral abutment • Pile type: HP10x42 • 10’ prebore required • Pu = 92.3 kips per pile • Generalized Soil Category: Cohesive with Setup • Construction Control: WEAP
Page 9
Soil Profile at West Abutment
Ftg Bot Elev 933
Prebore Elev 923
10’ prebore
Final ground surface
Existing ground surface
11’
Surface Elev 937
30’
Soft Silty Clay
Silty Sand
Firm Glacial Clay
Very Firm Glacial Clay
4’
9’
10’
Layer Elev 917
Layer Elev 907
Layer Elev 926
Fill
N = 4
N = 6
N = 12
N = 20 35’
Boring Bot Elev 872
SPT N values are in units of blows per foot
2’
Page 10
County Problem 2 H30 - Integral Abutment - HP10x57
WEAP, Cohesive Soil, Downdrag, Bedrock H30-06 Pretensioned Prestressed Concrete Beam (PPCB) Bridge Standards (https://iowadot.gov/bridge/standards/english/h30-06.pdf)
• 30’ roadway width • 0° skew • 188’-10” long bridge • 3 Spans: 59.917’ – 69’ – 59.917’ (B59 and B67 beams) • Integral abutment • Pile type: HP10x57 • Use maximum of 15’ prebore (due to presence of downdrag) • Pu = 135 kips per pile • Generalized Soil Category: Cohesive (bedrock present) • Construction Control: WEAP
Page 11
See blow-up on next page.
Page 12 Standard Sheet H30-05-06
Note: The Structural Resistance Level 1 (SRL-1) limit from BDM Table 6.2.6.1-1 for an HP10x57 is 243 kips
of nominal resistance. The factored resistance is (0.60)*(243 kips) = 145.8 kips which should be and, in fact, is greater than Pu = 135 kips.
Pu = 135 kips per pile
Page 13
Standard Sheet H30-01A-06, GENERAL NOTES
Note: The above statement is in conflict with the 2020 BDM update in BDM Article 6.1.6.1.1.1 which
requires 34 feet from the bottom of the footing to the top of the rock for an integral abutment with HP10x57 piles and 10 feet of prebore if no further analysis is performed (https://iowadot.gov/bridge/policy/06-01-00SubsLRFD.pdf). If prebore is increased to 15 feet then 37 feet from the bottom of the footing to the top of the rock is required. BDM Table 6.1.6.1.1.1-1 contains the full range of values for various conditions.
A reference to CADD note E177 is made in the plan notes above, but this note is no longer available in the BDM and is not required in the plan set.
Page 14
BDM Table 6.2.4.2-1. Prebored hole depths for abutments (https://iowadot.gov/bridge/policy/06-02-00PileLRFD.pdf)
BDM Table 6.2.4.2-2. Recommended H-pile penetration into bedrock (https://iowadot.gov/bridge/policy/06-02-00PileLRFD.pdf)
Rock classification Recommended penetration, feet
Broken limestone 8 - 12 where practical Shale or firm shale 8 – 12 Medium hard shale, hard shale, or siltstone with 50 ≤ N ≤ 200
4 – 8
Sandstone, siltstone, or shale with N ≥ 200
3
Solid limestone 1 – 3
BDM 6.2.4.6. Target Driving Resistance – Consider Setup? (https://iowadot.gov/bridge/policy/06-02-00PileLRFD.pdf) In the case of H-piles and cohesive soils with WEAP construction control the designer shall consider the benefit of setup in the determination of the target driving resistance except in the following cases:
• Piles driven to bedrock, • Piles subjected to downdrag, • Piles in contact with cohesive soil with an overall average N of less than 5, and • Piles used in accelerated bridge construction.
Even though the piles are steel H-piles, WEAP will be used for construction control, and the soil will be classified as cohesive the benefits of setup will not be considered for these piles since they are being driven to bedrock and downdrag is present.
Page 15
Soil Profile at West Abutment
Ftg Bot Elev 933
Prebore Elev 918
15’ prebore *
Final ground surface
Existing ground surface 7’
54’
Soft Silty Clay
Firm Silty Clay
Very Firm Glacial Clay
23’
15’
Layer Elev 888
Layer Elev 903
Surface Elev 926
Fill Assumed N = 20
N = 4
N = 12
N = 20 15’
Boring Bot Elev 872
SPT N values are in units of blows per foot
15’
Neutral Plane
Downdrag Zone
Bearing Zone
1’
Hard Shale, N = 162
Layer Elev 873
* Prebore was increased from 10’ to the maximum allowed of 15’ to reduce downdrag.
2’
Page 16
County Problem 3 H30 - Pile Bent - HP14x73
WEAP, Non-cohesive Soil, Scour H30-06 Pretensioned Prestressed Concrete Beam (PPCB) Bridge Standards (https://iowadot.gov/bridge/standards/english/h30-06.pdf)
• 30’ roadway width • 0° skew • 188’-10” long bridge • 3 Spans: 59.917’ – 69’ – 59.917’ (B59 and B67 beams) • Non-monolithic pile bent • Pile type: HP14x73 • 10’ scour • Pu = 168 kips per pile • Generalized Soil Category: Non-cohesive • Construction Control: WEAP
Page 17
See blow-up on next page.
Page 18
Standard Sheet H30-47-06
Note: The Structural Resistance Level 1 (SRL-1) limit from BDM Table 6.6.4.2.1.1 for an HP14x73 is 265 kips of nominal resistance. The factored resistance is (0.70)*(265 kips) = 185.5 kips which should be and, in fact, is greater than Pu = 168 kips.
Pu = 168 kips per pile
See P10L sheet on next page.
Page 19
See blow-up on next
page.
Page 20
Standard Sheet P10L
Note: The Structural Resistance Level 1 (SRL-1) limit from BDM Table 6.6.4.2.1.1 for an HP14x73 is (0.70)*(265 kips) = 185.5 kips. Additionally BDM Table 6.6.4.2.1.1 recommends a minimum height of the pile above the ground. For the HP14x73 this minimum height is 13’.
Page 21
Soil Profile at Pier 1
Cap Bot Elev 933
15’
Stream bed
1.5’
100’
Soft Silty Clay, N = 4
Fine Sand
Coarse Sand
7’
13’
Layer Elev 896
Layer Elev 913
Surface Elev 920
N = 13
N = 20 76’
Boring Bot Elev 820
SPT N values are in units of blows per foot
3’
Scour Zone
Bearing Zone
Pile encasement
4’ Layer Elev 909
Fine Sand, N = 2
9’
89’
Surface Elev 918 2’
Page 22
Appendix A. Friction and End Bearing Soil Charts End Bearing Soil Chart LRFD driven pile nominal unit geotechnical resistances for end bearing (BDM Table 6.2.7-1)
SOIL DESCRIPTION
BLOW COUNT ESTIMATED NOMINAL RESISTANCE VALUES FOR END BEARING PILE IN KIPS [KSI]
N60-VALUE (8) WOOD PILE (1),
(3)
STEEL “H” GRADE 50
PRESTRESSED CONCRETE (2)
STEEL PIPE (4)
MEAN RANGE 10 12 14 12 14 16 10 12 14 18 Granular material <15 --- (5) (5) (5) (5) (5) (5) (5) (5) (5) (5) (5)
Fine or medium sand
15 --- 32 (5) (5) (5) 60 84 108 32 48 64 108
Coarse sand 20 --- 44 (5) (5) (5) 84 116 148 44 64 88 144 Gravelly sand 21 --- 44 (5) (5) (5) 84 116 148 44 64 88 144 25 --- 56 (5) (5) (5) (7) (7) (7) (7) (7) (7) (7)
--- 25-50 (6) [ 2-4 ] [ 2-4 ] [ 2-4 ] (6), (7) (6), (7) (6), (7) (7) (7) (7) (7)
--- 50-100 (6) [ 4-8 ] [ 4-8 ] [ 4-8 ] (6) (6) (6) (7) (7) (7) (7)
--- 100-300 (6) [ 8-16 ] [ 8-16 ] [ 8-16 ] (6) (6) (6) (7) (7) (7) (7)
--- >300 (6) [ 18 ] [ 18 ] [ 18 ] (6) (6) (6) (7) (7) (7) (7)
Bedrock
--- 100-200 (6) [ 12 ] [ 12 ] [ 12 ] (6) (6) (6) (7) (7) (7) (7)
--- >200 (6) [ 18 ] [ 18 ] [ 18 ] (6) (6) (6) (7) (7) (7) (7)
Cohesive material
12 10-50 16 (5) (5) (5) 28 40 52 16 24 32 52 20 --- 24 [ 1 ] [ 1 ] [ 1 ] 44 64 84 28 36 52 84 25 --- 32 [ 2 ] [ 2 ] [ 2 ] 60 84 108 32 48 64 108 50 --- (6) [ 4 ] [ 4 ] [ 4 ] 116 (6) 164 (6) 212 (6) 56 96 128 212 100 --- (6) [ 7 ] [ 7 ] [ 7 ] (6) (6) (6) (6) (6) (6) (6)
Table notes: (1) Wood piles shall not be driven through soils with N > 25. (2) With prestressed concrete piles the preferred N for soil at the tip ranges from 25 to 35. Prestressed concrete piles have been proven to be difficult to drive
in very firm glacial clay and very firm sandy glacial clay. Prestressed concrete piles should not be driven in glacial clay with consistent N > 30 to 35. (3) End bearing resistance values for wood piles are based on a tip area of 72 in2. Values shall be adjusted for a different tip area. (4) Steel pipe piles should not be driven in soils with consistent N > 40. See the 1994 soils information chart [BDM 6.2.1.5] for end bearing when a conical
driving point is used. (5) Do not consider end bearing. (6) Use of end bearing is not recommended for timber piles when N > 25 or for prestressed concrete piles when N > 35 or for any condition identified with this
note. (7) End bearing resistance shall be 0.0389 x “N” value [ksi]. (8) Use uncorrected N-values until N60-values are available.
Page 23 Friction Soil Chart LRFD driven pile nominal unit geotechnical resistances for friction bearing (BDM Table 6.2.7-2)
SOIL DESCRIPTION BLOW COUNT ESTIMATED NOMINAL RESISTANCE VALUES FOR FRICTION PILE IN KIPS/FOOT N60-VALUE (5) WOOD
PILE STEEL “H” GRADE 50
PRESTRESSED CONCRETE
STEEL PIPE
MEAN RANGE 10 12 14 12 14 16 10 12 14 18 Alluvium or Loess Very soft silty clay 1 0 - 1 0.8 0.4 0.8 0.8 0.8 0.8 0.8 0.4 0.4 0.4 0.8
Soft silty clay 3 2 - 4 1.2 0.8 1.2 1.2 0.8 0.8 0.8 0.8 0.8 0.8 1.2 Stiff silty clay 6 4 - 8 1.6 1.2 1.6 2.0 1.2 1.6 2.0 1.2 1.2 1.6 2.0 Firm silty clay 11 7 - 15 2.4 2.0 2.4 2.8 2.4 2.8 3.2 1.6 2.0 2.4 2.8
Stiff silt 6 3 - 7 1.6 1.2 1.6 1.6 1.6 1.6 1.6 1.2 1.2 1.6 1.6 Stiff sandy silt 6 4 - 8 1.6 1.2 1.6 1.6 1.6 1.6 1.6 1.2 1.2 1.6 1.6 Stiff sandy clay 6 4 - 8 1.6 1.2 1.6 2.0 2.0 2.0 2.4 1.2 1.6 1.6 2.0
Silty sand 8 3 - 13 1.2 1.2 1.2 1.6 1.6 1.6 1.6 0.8 0.8 1.2 1.6 Clayey sand 13 6 - 20 2.0 1.6 2.0 2.8 2.4 2.4 2.8 1.6 2.0 2.4 2.8
Fine sand 15 8 - 22 2.4 2.0 2.4 2.8 2.4 2.8 3.2 1.6 2.0 2.4 2.8 Coarse sand 20 12 - 28 3.2 2.8 3.2 3.6 3.2 3.6 4.0 2.0 2.4 2.8 3.6 Gravely sand 21 11 - 31 3.2 2.8 3.2 3.6 3.6 3.6 4.0 2.0 2.4 2.8 3.6
Granular material > 40 --- (2) 4.0 4.8 5.6 (2) (2) (2) (2) (2) (2) (2) Glacial Clay
Firm silty glacial clay 11 7 - 15 2.8 2.4 2.8 3.2 2.8 3.2 3.6 2.0 2.4 2.4 3.2 Firm clay (gumbotil) 12 9 - 15 2.8 2.4 2.8 3.2 2.8 3.2 3.6 2.0 2.4 2.4 3.2 Firm glacial clay(1) 11 7 - 15 2.4
[ 3.2 ] 2.8
[ 3.2 ] 3.2
[ 4.0 ] 3.6
[ 4.4 ] 3.2
[ 4.0 ] 3.6
[ 4.4 ] 4.0
[ 4.8 ] 2.0
[ 2.4 ] 2.4
[ 2.8 ] 2.8
[ 3.2 ] 3.6
[ 4.4 ] Firm sandy glacial
clay(1) 13 9 - 15 2.4
[ 3.2 ] 2.8
[ 3.2 ] 3.2
[ 4.0 ] 3.6
[ 4.4 ] 3.2
[ 4.0 ] 3.6
[ 4.4 ] 4.0
[ 4.8 ] 2.0
[ 2.4 ] 2.4
[ 2.8 ] 2.8
[ 3.2 ] 3.6
[ 4.4 ] Firm - very firm glacial
clay(1) 14 11 - 17 2.8
[ 3.6 ] 2.8
[ 4.0 ] 3.2
[ 4.8 ] 3.6
[ 5.6 ] 4.0
[ 4.8 ] 4.4
[ 5.2 ] 4.8
[ 5.6 ] 2.4
[ 3.2 ] 2.8
[ 3.6 ] 3.2
[ 4.0 ] 4.0
[ 5.2 ] Very firm glacial clay(1) 24 17 - 30 2.8
[ 3.6 ] 2.8
[ 4.0 ] 3.2
[ 4.8 ] 3.6
[ 5.6 ] 3.2 (3)
[4.8] 3.6 (3)
[5.6] 4.4 (3)
[6.4] 2.4
[ 3.2 ] 2.8
[ 3.6 ] 3.2
[ 4.0 ] 4.0
[ 5.2 ] Very firm sandy glacial
clay(1) 25 15 - 30 3.2
[ 4.0 ] 2.8
[ 4.0 ] 3.2
[ 4.8 ] 3.6
[ 5.6 ] 3.2 (3)
[4.8] 3.6 (3)
[5.6] 4.4 (3)
[6.4] 2.4
[ 3.2 ] 2.8
[ 3.6 ] 3.2
[ 4.0 ] 4.0
[ 5.2 ] Cohesive or glacial
material(1) > 35 --- (2) 2.8
[ 4.0 ] 3.2
[ 4.8 ] 3.6
[ 5.6 ] (2)
(2)
(2)
2.0 (4) [ 3.2 ]
2.4 (4) [ 4.0 ]
2.8 (4) [ 4.4 ]
3.6 (4) [ 5.6 ]
Table notes: (1) For double entries the upper value is for an embedded pile within 30 feet of the natural ground elevation, and the lower value [ ] is for pile depths more
than 30 feet below the natural ground elevation. (2) Do not consider use of this pile type for this soil condition, wood with N > 25, prestressed concrete with N > 35, or steel pipe with N > 40. (3) Prestressed concrete piles have proven to be difficult to drive in these soils. Prestressed piles should not be driven in glacial clay with consistent N >
30 to 35. (4) Steel pipe piles should not be driven in soils with consistent N > 40. (5) Use uncorrected N-values until N60-values are available.
Page 24
Appendix B. Soil Categories Geotechnical resistance factors for design (contract length) and for construction (target driving resistance) were statistically calibrated by Iowa State University researchers for three generalized soil categories based on a 70% rule. Therefore the designer will need to use these same categories when selecting geotechnical resistance factors for design:
• Cohesive: Along the pile length in contact with soil, 70% or more of the length is through soils classified as cohesive according to the table below.
• Mixed: Along the pile length in contact with soil, 31% to 69% of the length is through soils classified as cohesive according to the table below (or 31% to 69% of the length is through soils classified as non-cohesive according to the table below).
• Non-Cohesive: Along the pile length in contact with soil, 70% or more of the length is through soils classified as non-cohesive according to the table below.
Soil category based on soil classification (BDM Table 6.2.8)
Friction Pile Charts BDM Table 6.2.7-2
Page 25
Appendix C. Recommended Pile Penetration If an H-pile is designed with end bearing resistance in bedrock the pile contract length should include the penetration length as indicated in Table 6.2.4.2-2. Prestressed concrete and steel pipe piles should be driven to bedrock only with approval of the Soils Design Section. Timber piles shall not be driven to bear on bedrock.
Recommended H-pile penetration into bedrock (BDM Table 6.2.4.2-2) Rock classification Recommended
penetration, feet Broken limestone 8 - 12 where practical Shale or firm shale 8 – 12 Medium hard shale, hard shale, or siltstone with 50 ≤ N ≤ 200
4 – 8
Sandstone, siltstone, or shale with N ≥ 200
3
Solid limestone 1 – 3 The design penetration for any pile should be a minimum of 10 feet into hard cohesive or dense granular soil and a minimum of 20 feet into soft cohesive or loose granular soil. Piles driven through embankments should penetrate 10 feet into original ground unless refusal on bedrock or a competent layer occurs at a lesser elevation. (BDM 6.2.4.2)