1. 1 Driven Pile Foundation Support- Cost Components Wagner Komurka Geotechnical Group, Inc. 2009 PDCA Professors’ Driven Pile Institute June 15-16, 2009 Van E. Komurka, P.E.

2. 2 Discuss support-cost components:Discuss support-cost components: –Pile ConventionalConventional Profile (as a function of depth)Profile (as a function of depth) –Cap –Column (matching allowable pile loads to structure column loads) –System Talk Outline Define support cost.Define support cost. Present case histories (large and small) illustrating load-matching approach.Present case histories (large and small) illustrating load-matching approach.

3. 3 The cost of an installed or constructed foundation element or system divided by its allowable load, usually expressed in dollars per ton (i.e., how many dollars it costs to support one ton of load). Support' Cost (Sŭpōrt' Kŏst)

4. 4 As a normalized parameter, allows direct (apples-to-apples) economic comparison of different foundation alternatives:As a normalized parameter, allows direct (apples-to-apples) economic comparison of different foundation alternatives: –Shallow vs. deep (e.g., spread footings vs. piles) –Deep vs. deep (e.g., drilled piers vs. piles) –Pile section vs. pile section (e.g., 10.75” vs. 12.75”) –Pile capacity vs. pile capacity (e.g., 70 T vs. 150 T ) Support' Cost (Sŭpōrt' Kŏst) Allows economic evaluation and optimization of deep foundation system cost componentsAllows economic evaluation and optimization of deep foundation system cost components

5. 5 Cap Piles Design Column Load Column Deep Foundation System Components

6. 6 Pile Support Cost Pile Cost Allowable Pile Load In general, higher allowable pile loads result in lower pile support costs: Spread pile length invested to penetrate through poor soils over more capacity Spread pile length invested to penetrate through poor soils over more capacity In competent soils, capacity generally increases faster with depth than does costIn competent soils, capacity generally increases faster with depth than does cost =

7. 7 Pile Support Cost Pile Support Cost = Pile Cost Allowable Pile Load $1,500 per pile 50-ton allow. load = $30 / ton $3,000 per pile 150-ton allow. load = $20 / ton

8. 8 WKG 2 Pile Support Costs Project NamePile Type Allowable Pile Load, tons Pile Support Cost, dollars per allowable ton Midwest Express (Wisconsin) Center, Phase 1 10.75 x 0.365 12.75 x 0.365 100 150 12.12 11.52 Miller Park 16-inch Monotube20012.20 Johnson Controls Brengel Technology Center 12.75 x 0.31214813.48 Potawatomi Casino Expansion Potawatomi Casino Parking Structure 10.75 x 0.250 80 83 Overall Project Average15.55 Milwaukee Journal-Sentinel Production Facility 10.75 x 0.307 40 65 75 80 85 20.59 16.97 15.12 15.34 14.81 Overall Project Average15.64 Sixth Street Viaduct Replacement 10.75 x 0.250 12.75 x 0.375 65 154 182 190 20.47 10.50 8.62 13.92 Overall Project Average15.28 State Fair Park Exposition Hall 9.625 x 0.5452009.40 Great Lakes Aquatarium/Discovery World Museum (Pier Wisconsin) 10.75 x 0.365 13.375 x 0.480 91 180 251 14.73 13.36 9.91

9. 9 Pile Support Costs – WKG 2 Projects Pile Support Cost, dollars per allowable ton Allowable Pile Load, tons (factor of safety = 2.0)

10. 10 Pile Support Costs – Sixth Street Viaduct Replacement Allowable Pile Load, tons Pile Support Cost, dollars per allowable ton Various:  Pile Diameters (10.75- and 12.75-inch- O.D.)  Safety Factor (from 2.0 to 2.5)  Installation Criteria (WEAP, Modified EN)  Subsurface Conditions (from till at 4 feet, to 60 feet of organic silt)

11. 11 Achieving Higher-Capacity Piles  Use larger section, larger hammer, drive piles “harder,” perhaps deeper.  Increase design stresses (e.g., from 9-12 ksi to 16 ksi)  Incorporate soil/pile set-up:  Use displacement pile.  Adjust testing program (wait longer to test, restrike testing, etc.).  Use higher-strength concrete (e.g., in concrete-filled pipe piles from 3-4 ksi to 6 ksi)

12. 12 Cap Support Cost Cap Cost Design Column Load Higher allowable pile loads result in fewer piles, smaller caps, and therefore lower cap support costs. Minimized cap support cost results from using the minimum required number of piles. =

13. 13 Cap Support Costs Cap Support Cost, dollars per allowable ton Design Column Load, kips

14. 14 Column Support Cost Pile Cap Cost + Σ Pile Costs Design Column Load Measures how well the allowable pile load, in conjunction with the minimum required number of piles, matches the design column load. Minimum column support cost results from using the optimum allowable pile load. =

15. 15 Optimum Allowable Pile Load Design Column Load Minimum Req’d No. of Piles  Design Column Load = 900 kips  Minimum Req’d No. of Piles = 3  Optimum Allowable Pile Load = 900 kips 3 piles = 300 kips/pile = 150 tons/pile 900 K =

16. 16 Lower-Than-Optimum Allowable Pile Loads  Increased pile support costs – each ton of allowable pile load costs more than it would have with higher- capacity piles.  Increased cap support costs – each cap is larger than it would have been with higher-capacity piles.  Increased column support costs – for a given column load, pile and cap costs are higher than they would have been with higher-capacity (closer to optimum allowable load) piles.  Increased number of pile installations – may increase total project drive time.

17. 17 Higher-Than-Optimum Allowable Loads  Increased column support costs – although pile support costs are low, and cap costs are minimized, unnecessary capacity is installed (unnecessary cost is incurred). Low unit cost. All you need.

18. 18 Match Allowable Pile Loads to Column Loads!  Piles are below-grade structural extensions of above- grade structural elements; their design should be integrated with the above-grade design.  Using one allowable pile load for a project is analogous to using one beam or column design throughout a building.  Two fixed design components:  Structural loads to support (column load schedule).  Soil/pile resistance behavior to support structural loads (depth vs. capacity relationships).  Deep foundation system design flexibility (choice of pile type, section, allowable load, safety factor, etc.) allows accommodating fixed design components.

19. 19 System Support Cost Σ Deep Foundation System Costs Σ Column Design Loads Measures overall cost- effectiveness of deep foundation system. Provides basis for comparison of viable design and installation options. =

20. 20 Load-Matching Design Approach  Obtain foundation layout, column load schedule, and the minimum required number of piles at each cap, from structural engineer.  Calculate optimum allowable pile load for each cap.  If desired, calculate required “ultimate” pile capacity for each cap. To evaluate the cost-effectiveness of field testing, this can be done for a range of factors of safety.

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23. 23 Pier Wisconsin Pier Wisconsin

24. 24 Load-Matching Design Approach  Obtain foundation layout, column load schedule, and an indication of the minimum required number of piles at each cap, from structural engineer.  Calculate optimum allowable pile load for each cap.  Calculate required “ultimate” pile capacity for each cap. To evaluate the cost-effectiveness of field testing, this can be done for a range of factors of safety.  Generate histogram of optimized allowable pile loads (or of “ultimate” pile capacities).

25. 25 Allowable Pile Load Histogram Pier Wisconsin Optimum (Minimum) Required Number of Piles Allowable Pile Load, tons

26. 26 Load-Matching Design Approach  Obtain foundation layout, column load schedule, and an indication of the minimum required number of piles at each cap, from structural engineer.  Calculate optimum allowable pile load for each cap.  Calculate required ultimate pile capacity for each cap. To evaluate the cost-effectiveness of field testing, this can be done for a range of factors of safety.  Generate histogram of optimized allowable, and/or ultimate, pile capacities.  Select appropriate allowable pile loads (or “ultimate” pile capacities), with design-team input.

27. 27 Allowable Pile Load Histogram Pier Wisconsin Optimum (Minimum) Required Number of Piles Allowable Pile Load, tons 180 tons251 tons91 tons

28. 28 Load-Matching Design Approach (continued)  Select viable pile type(s) and section(s) for selected allowable loads/capacities (91 T, 180 T, and 251 T ) {borings}.  Estimate individual pile lengths required for selected pile capacities.

29. 29 Estimated Ultimate Pile Capacity - Borings 13.375-inch-diameter Pipe Piles Pile Toe Elevation, feet Estimated “Ultimate” Pile Capacity, tons

30. 30 Estimated “Ultimate” Capacity, tons Pile Toe Elevation, feet Pile Test Program Capacity Profile Long-term Capacity EOID Capacity Set-Up

31. 31 Load-Matching Design Approach (continued)  Select viable pile type and section for selected pile capacities.  Estimate individual pile lengths required for selected pile capacities.  Estimate total pile lengths required for project.  Using representative prices, estimate total pile cost for project.

32. 32 Allowable Pile Load Histogram Pier Wisconsin Optimum (Minimum) Required Number of Piles Allowable Pile Load, tons 180 tons 251 tons 91 tons

33. 33 $21.61 / ft $27.97 / ft

34. 34 Load-Matching Design Approach (continued)  Select viable pile type and section for selected pile capacities.  Estimate individual pile lengths required for selected pile capacities.  Calculate total pile lengths required for project.  Calculate total pile cost for project.  Perform additional iterations as desired.

35. 35 $19.16 / ft $21.61 / ft $27.97 / ft

36. 36 $19.16 / ft $21.61 / ft $27.97 / ft

37. 37 Pile Support Costs – WKG 2 Projects Pile Support Cost, dollars per allowable ton Allowable Pile Load, tons (safety factor = 2.0)

38. 38 First Place Condominiums  Relatively small project, approximately 200 piles required.  Renovation of a former storage warehouse into condominiums.  Piles required only beneath small building addition.  Existing geotechnical engineering report prepared for different site development plans.  A review of existing recommendations relative to currently proposed development was desired.

39. 39 Optimum (Minimum) Required Number of Piles Allowable Pile Load, tons Optimum Allowable Pile Load Histogram First Place Condominiums

40. 40 First Place Condominiums - Proposed Designs AllowableNumberEstimated DesignLoad, tonsof PilesFootage Original7020515,580

41. 41 Optimum (Minimum) Required Number of Piles Allowable Pile Load, tons Optimum Allowable Pile Load Histogram First Place Condominiums

42. 42 First Place Condominiums - Proposed Designs AllowableNumberEstimated DesignLoad, tonsof PilesFootage Original7020515,580 Revised7218014,040 SAVE:251,540 $34,250 + cap costs on $346,500 worth of piles

43. 43 First Place Condominiums - Proposed Designs AllowableNumberEstimated DesignLoad, tonsof PilesFootage Original7020515,580 Revised7218014,040 Alternate 100130$60,000 savings 72 tons per pile x 180 piles = 12,960 tons to support 12,960 tons / 100 tons per pile = 130 piles Save 50 piles & $60,000 ? Save 50 piles & $60,000 ?

44. 44 Optimum (Minimum) Required Number of Piles Allowable Pile Load, tons Optimum Allowable Pile Load Histogram First Place Condominiums

45. 45 72-ton allowable 100-ton allowable 72 tons 100 tons

46. 46 First Place Condominiums - Proposed Designs AllowableNumberEstimated DesignLoad, tonsof PilesFootage Original7020515,580 Revised7218014,040 Alternate10016415,744 SAVE:16 (not 50)-1,704 ($37,897) (if same pile section is used) ($37,897) (if same pile section is used)

47. 47 Conclusions Consider using higher-capacity piles (when building loads warrant)Consider using higher-capacity piles (when building loads warrant) -Lower pile support cost -Lower cap support cost Consider matching (optimizing) allowable pile loads to column loadsConsider matching (optimizing) allowable pile loads to column loads -Lower column support cost All should result in more-cost-effective driven pile foundationsAll should result in more-cost-effective driven pile foundations Evaluate design options/alternatives using actual column loads and allowable pile load histogramEvaluate design options/alternatives using actual column loads and allowable pile load histogram

48. 48 Questions / Comments?