Economics of Driven Pile Foundations

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1 Economics of Driven Pile Foundations 2013 PDCA Professors Driven Pile Institute ( PDPI ) June 24-28, 2013 Van E. Komurka, P.E., D.GE, F.ASCE Wagner Komurka Geotechnical Group, Inc. 1

2 Talk Outline Define support cost. Discuss major support-cost components: Pile Cap Discuss load-matching approach. Present case histories (large and small) illustrating load-matching approach. 2

3 Sup port' Cost (Sŭ pōrt' Kŏst) 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). 3

4 Sup port' Cost (Sŭ pōrt' Kŏst) 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., vs ) Pile capacity vs. pile capacity (e.g., 70 T vs. 150 T ) Allows economic evaluation and optimization of deep foundation system cost components 4

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

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 In competent soils, capacity generally increases faster with depth than does cost 6

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 7

8 WKG 2 Pile Support Costs Project Name Pile Type Midwest Express (Wisconsin) Center, Phase x x Allowable Pile Load, tons Pile Support Cost, dollars per allowable ton Miller Park 16-inch Monotube Johnson Controls Brengel Technology Center x Potawatomi Casino Expansion Potawatomi Casino Parking Structure x x Overall Project Average Milwaukee Journal-Sentinel Production Facility x Overall Project Average Sixth Street Viaduct Replacement x x x x Overall Project Average State Fair Park Exposition Hall x Great Lakes Aquatarium/Discovery World Museum (Pier Wisconsin) x x x

Pile Support Cost, dollars per allowable ton Pile Support Costs WKG 2 Projects 22 20 18 16 y = 90.662x -0.

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

10 Pile Support Cost, dollars per allowable ton Pile Support Costs Sixth Street Viaduct Replacement Various: Pile Diameters ( and 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) y = x R 2 = y = e x R 2 = Allowable Pile Load, tons 10

Achieving Higher-Capacity Piles Use larger section, larger hammer, drive piles harder, perhaps deeper. Incorporate soil/pile set-up: Use displacement pile.

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

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. 12

13 Cap Support Cost, dollars per allowable ton Cap Support Costs Pile Minimum Ton Piles 6 75-Ton Piles Ton Piles 150-Ton Piles 200-Ton Piles Ton Piles ,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 Design Column Load, kips 13

14 900 K Load Matching Approach 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 14

15 Lower-Than-Optimum Allowable Pile Loads Increased pile support costs each ton of allowable pile load costs more with low-allowable-load piles than it would have with higher-allowable-load piles. Increased cap support costs each cap has a larger footprint, and contains more concrete, than it would have with higher-allowable-load piles. This cost differential is increased if environmentally impacted soils are excavated for cap construction. Increased number of pile installations may increase total project drive time. This can be most-important project consideration. 15

16 Higher-Than-Optimum Allowable Pile Loads Unused capacity installed 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. 16

17 Match Allowable Pile Loads to Column Loads! Piles are below-grade structural extensions of abovegrade 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, testing, safety factor, etc.) allows accommodating fixed design components. 17

18 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. 18

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21 F.S. = 2.00 Maximum Optimum Required Allowable "Ultimate" Column Min. Column Pile Pile Line No. Load, Load, Capacity, Designation of Piles kips tons tons 0.A A Pier Wisconsin P P P P P P A M N P P P Q Q M J G H K B B C R K C F J J Q R

22 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). 22

23 Optimum (Minimum) Required Number of Piles 91 tons Allowable Pile Load Histogram Pier Wisconsin 180 tons 194 tons 227 tons Allowable Pile Load, tons 23

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, and/or ultimate, pile capacities. Select appropriate allowable pile loads (or ultimate pile capacities), with design-team input. 24

25 Optimum (Minimum) Required Number of Piles 91 tons Allowable Pile Load Histogram Pier Wisconsin 180 tons 194 tons 227 tons tons 180 tons 251 tons Allowable Pile Load, tons 25

26 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. 26

Pile Toe Elevation, feet Estimated Ultimate Pile Capacity - Borings 13.

27 Pile Toe Elevation, feet Estimated Ultimate Pile Capacity - Borings inch-diameter Pipe Piles Estimated Ultimate Pile Capacity, tons 27

28 Pile Toe Elevation, feet EOID Capacity Set-Up Long-term Capacity Pile Test Program Capacity Profile Estimated Ultimate Capacity, tons 28

29 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. 29

30 Optimum (Minimum) Required Number of Piles 91 tons Allowable Pile Load Histogram Pier Wisconsin 180 tons 194 tons 227 tons tons 180 tons 251 tons Allowable Pile Load, tons 30

31 F.S. = 2.00 Maximum Optimum Required Allowable "Ultimate" 3 Capacities (91, 180, and 251 tons) Column Min. Column Pile Pile Est. Pile Est. Pile(s) Est. Pile(s) Line No. Load, Load, Capacity, No. Length, Footage, Cost, Designation of Piles kips tons tons of Piles feet feet dollars 0.A ,340 0.A ,340 $21.61 / ft P , ton max. P ,340 allow. load: P , P , x0.365 P ,340 feet: P ,340 4,402 0.A ,405 M ,405 $27.97 / ft N , ton max. P ,405 allow. load: P , P , /8" Q ,405 feet: Q ,405 9,288 M ,657 J ,314 G , ton max. H ,971 allow. load: K , B , /8" B ,971 feet: C ,971 16,815 R ,629 K ,629 C , ton max. F ,629 allow. load: J , J , /8" Q ,629 feet: R ,629 11, ,380 $1,157,416 31

32 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. 32

33 $19.16 / ft F.S. = 2.00 Maximum Optimum Required Allowable "Ultimate" 3 Capacities (91, 180, and 251 tons) 1 Capacity (10.75 x 0.188, 63 tons) Column Min. Column Pile Pile Est. Pile Est. Pile(s) Est. Pile(s) Est. Pile Est. Pile(s) Est. Pile(s) Line No. Load, Load, Capacity, No. Length, Footage, Cost, Number Length, Footage, Cost, Designation of Piles kips tons tons of Piles feet feet dollars of Piles feet feet dollars 0.A , ,223 0.A ,340 $21.61 / ft ,223 P , ton max ,223 P ,340 allow. load: ,223 P , ,223 P , x ,223 P ,340 feet: ,223 P ,340 4, ,223 0.A , ,223 M ,405 $27.97 / ft ,223 N , ton max ,334 P ,405 allow. load: ,334 P , ,334 P , /8" ,334 Q ,405 feet: ,334 Q ,405 9, ,334 M , ,334 J , ,668 G , ton max ,335 H ,971 allow. load: ,335 K , ,335 B , /8" ,335 B ,971 feet: ,335 C ,971 16, ,335 R , ,335 K , ,447 C , ton max ,669 F ,629 allow. load: ,669 J , ,780 J , /8" ,780 Q ,629 feet: ,780 R ,629 11, , ,380 $1,157,416 1,560 90,480 $1,733,597 $576,181 33

34 $19.16 / ft F.S. = 2.00 Maximum Optimum Required Allowable "Ultimate" 3 Capacities (91, 180, and 251 tons) 1 Capacity (10.75 x 0.188, 63 tons) Column Min. Column Pile Pile Est. Pile Est. Pile(s) Est. Pile(s) Est. Pile Est. Pile(s) Est. Pile(s) Line No. Load, Load, Capacity, No. Length, Footage, Cost, Number Length, Footage, Cost, Designation of Piles kips tons tons of Piles feet feet dollars of Piles feet feet dollars 0.A , ,223 0.A ,340 $21.61 / ft ,223 P , ton max ,223 P ,340 allow. load: ,223 P , ,223 P , x ,223 P ,340 feet: ,223 P ,340 4, ,223 0.A , ,223 M ,405 $27.97 / ft ,223 N , ton max ,334 P ,405 allow. load: ,334 P , ,334 P , /8" ,334 Q ,405 feet: ,334 Q ,405 9, ,334 M , ,334 J , ,668 G , ton max ,335 H ,971 allow. load: ,335 K , ,335 B , /8" ,335 B ,971 feet: ,335 C ,971 16, ,335 R , ,335 K , ,447 C , ton max ,669 F ,629 allow. load: ,669 J , ,780 J , /8" ,780 Q ,629 feet: ,780 R ,629 11, , ,380 $1,157,416 1,560 90,480 $1,733,597 $576,181 34

35 Pile Support Cost, dollars per allowable ton Pile Support Costs WKG 2 Projects y = x R 2 = Allowable Pile Load, tons (safety factor = 2.0) 35

36 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. 36

37 Optimum (Minimum) Required Number of Piles Optimum Allowable Pile Load Histogram First Place Condominiums Allowable Pile Load, tons 37

38 First Place Condominiums - Proposed Designs Allowable Number Estimated Design Load, tons of Piles Footage Original ,580 38

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

40 First Place Condominiums - Proposed Designs Allowable Number Estimated Design Load, tons of Piles Footage Original ,580 Revised ,040 SAVE: 25 1,540 $34,250 + cap costs on $346,500 worth of piles 40

41 First Place Condominiums - Proposed Designs Allowable Number Estimated Design Load, tons of Piles Footage Original ,580 Revised ,040 Alternate $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? 41

42 Optimum (Minimum) Required Number of Piles Optimum Allowable Pile Load Histogram First Place Condominiums Allowable Pile Load, tons 42

43 72-ton allowable 100-ton allowable 72 tons 72 tons 72 tons 100 tons 100 tons 100 tons 43

44 First Place Condominiums - Proposed Designs Allowable Number Estimated Design Load, tons of Piles Footage Original ,580 Revised ,040 Alternate ,744 SAVE: 16 (not 50) -1,704 ($37,897) (if same pile section is used) 44

45 Conclusions 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 loads - Lower column support cost Evaluate design options/alternatives using actual column loads and allowable pile load histogram All should result in more-cost-effective driven pile foundations 45

46 Questions / Comments? 46

A Technique for Selecting Appropriate Allowable Pile Loads for Driven-Pile Projects: Load Matching

A Technique for Selecting Appropriate Allowable Pile Loads for Driven-Pile Projects: Load Matching Pile Driving Contractors Association 2015 Professor s Driven Pile Institute June 25, 2015 Van E. Komurka,