Economics of Driven Pile Foundations

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

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

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

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., 10.75 vs. 12.75 ) Pile capacity vs. pile capacity (e.g., 70 T vs. 150 T ) Allows economic evaluation and optimization of deep foundation system cost components 4

Design Column Load Deep Foundation System Components Column Cap Piles 5

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

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

WKG 2 Pile Support Costs Project Name Pile Type Midwest Express (Wisconsin) Center, Phase 1 10.75 x 0.365 12.75 x 0.365 Allowable Pile Load, tons 100 150 Pile Support Cost, dollars per allowable ton 12.12 11.52 Miller Park 16-inch Monotube 200 12.20 Johnson Controls Brengel Technology Center 12.75 x 0.312 148 13.48 Potawatomi Casino Expansion Potawatomi Casino Parking Structure 10.75 x 0.250 10.75 x 0.250 80 83 Overall Project Average 15.55 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 Average 15.64 Sixth Street Viaduct Replacement 10.75 x 0.250 12.75 x 0.375 12.75 x 0.375 12.75 x 0.375 65 154 182 190 20.47 10.50 8.62 13.92 Overall Project Average 15.28 State Fair Park Exposition Hall 9.625 x 0.545 200 9.40 Great Lakes Aquatarium/Discovery World Museum (Pier Wisconsin) 10.75 x 0.365 13.375 x 0.480 13.375 x 0.480 91 180 251 14.73 13.36 9.91 8

Pile Support Cost, dollars per allowable ton Pile Support Costs WKG 2 Projects 22 20 18 16 y = 90.662x -0.402 R 2 = 0.712 14 12 10 8 40 60 80 100 120 140 160 180 200 220 240 260 9 Allowable Pile Load, tons (factor of safety = 2.0)

Pile Support Cost, dollars per allowable ton Pile Support Costs Sixth Street Viaduct Replacement 40 35 30 25 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) 20 15 y = 245.41x -0.5529 R 2 = 0.4787 10 y = 35.326e -0.0058x R 2 = 0.5423 5 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 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. 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

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

Cap Support Cost, dollars per allowable ton Cap Support Costs 12 11 10 3-Pile Minimum 9 8 7 50-Ton Piles 6 75-Ton Piles 5 100-Ton Piles 150-Ton Piles 200-Ton Piles 4 250-Ton Piles 3 2 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 Design Column Load, kips 13

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

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

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

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

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

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-8.5 1 158 79 158 0.A-0.5 1 180 90 180 Pier Wisconsin P-3.3 1 181 91 181 P-3.7 1 181 91 181 P-4.5 1 181 91 181 P-5 1 181 91 181 P-5.5 1 181 91 181 P-6 1 181 91 181 0.A-8 1 203 102 203 M.5-8 1 228 114 228 N-8.5 1 360 180 360 P.7-8.5 1 360 180 360 P-0.5 1 360 180 360 P-8.5 1 360 180 360 Q.8-3 1 360 180 360 Q-0.5 1 360 180 360 M.5-4 1 368 184 368 J-5 2 748 187 374 G-7 3 1479 247 493 H-7 3 1479 247 493 K-6 3 1484 247 495 B-7 3 1487 248 496 B-6 3 1507 251 502 C-8 3 1508 251 503 R1-5.9 3 1510 252 503 K-7 3 1529 255 510 C-4 3 1874 312 625 F-6 3 1879 313 626 J-6 3 1942 324 647 J-4 3 1995 333 665 Q-9 3 2003 334 668 R-9 3 2003 334 668 448 21

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

Optimum (Minimum) Required Number of Piles 91 tons Allowable Pile Load Histogram Pier Wisconsin 180 tons 194 tons 227 tons 70 60 50 40 30 20 10 0 75 100 125 150 175 200 225 250 275 300 325 350 375 Allowable Pile Load, tons 23

Optimum (Minimum) Required Number of Piles 91 tons Allowable Pile Load Histogram Pier Wisconsin 180 tons 194 tons 227 tons 70 91 tons 180 tons 251 tons 60 50 40 30 20 10 0 75 100 125 150 175 200 225 250 275 300 325 350 375 Allowable Pile Load, tons 25

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 13.375-inch-diameter Pipe Piles 10 0-10 -20-30 -40-50 -60-70 -80-90 -100-110 0 100 200 300 400 500 600 700 Estimated Ultimate Pile Capacity, tons 27

Pile Toe Elevation, feet 10 0-10 -20-30 -40-50 -60-70 -80-90 -100-110 -120 EOID Capacity Set-Up Long-term Capacity Pile Test Program Capacity Profile -130 0 50 100 150 200 250 300 350 Estimated Ultimate Capacity, tons 28

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

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-8.5 1 158 79 158 1 62 62 1,340 0.A-0.5 1 180 90 180 1 62 62 1,340 $21.61 / ft P-3.3 1 181 91 181 1 62 62 1,340 91-ton max. P-3.7 1 181 91 181 1 62 62 1,340 allow. load: P-4.5 1 181 91 181 1 62 62 1,340 71 P-5 1 181 91 181 1 62 62 1,340 10.75x0.365 P-5.5 1 181 91 181 1 62 62 1,340 feet: P-6 1 181 91 181 1 62 62 1,340 4,402 0.A-8 1 203 102 203 1 86 86 2,405 M.5-8 1 228 114 228 1 86 86 2,405 $27.97 / ft N-8.5 1 360 180 360 1 86 86 2,405 180-ton max. P.7-8.5 1 360 180 360 1 86 86 2,405 allow. load: P-0.5 1 360 180 360 1 86 86 2,405 108 P-8.5 1 360 180 360 1 86 86 2,405 13-3/8" 0.480 Q.8-3 1 360 180 360 1 86 86 2,405 feet: Q-0.5 1 360 180 360 1 86 86 2,405 9,288 M.5-4 1 368 184 368 1 95 95 2,657 J-5 2 748 187 374 2 95 190 5,314 G-7 3 1479 247 493 3 95 285 7,971 251-ton max. H-7 3 1479 247 493 3 95 285 7,971 allow. load: K-6 3 1484 247 495 3 95 285 7,971 177 B-7 3 1487 248 496 3 95 285 7,971 13-3/8" 0.480 B-6 3 1507 251 502 3 95 285 7,971 feet: C-8 3 1508 251 503 3 95 285 7,971 16,815 R1-5.9 3 1510 252 503 4 95 380 10,629 K-7 3 1529 255 510 4 95 380 10,629 C-4 3 1874 312 625 4 95 380 10,629 251-ton max. F-6 3 1879 313 626 4 95 380 10,629 allow. load: J-6 3 1942 324 647 4 95 380 10,629 125 J-4 3 1995 333 665 4 95 380 10,629 13-3/8" 0.480 Q-9 3 2003 334 668 4 95 380 10,629 feet: R-9 3 2003 334 668 4 95 380 10,629 11,875 448 481 42,380 $1,157,416 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. Calculate total pile lengths required for project. Calculate total pile cost for project. Perform additional iterations as desired. 32

$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-8.5 1 158 79 158 1 62 62 1,340 2 58 116 2,223 0.A-0.5 1 180 90 180 1 62 62 1,340 $21.61 / ft 2 58 116 2,223 P-3.3 1 181 91 181 1 62 62 1,340 91-ton max. 2 58 116 2,223 P-3.7 1 181 91 181 1 62 62 1,340 allow. load: 2 58 116 2,223 P-4.5 1 181 91 181 1 62 62 1,340 71 2 58 116 2,223 P-5 1 181 91 181 1 62 62 1,340 10.75x0.365 2 58 116 2,223 P-5.5 1 181 91 181 1 62 62 1,340 feet: 2 58 116 2,223 P-6 1 181 91 181 1 62 62 1,340 4,402 2 58 116 2,223 0.A-8 1 203 102 203 1 86 86 2,405 2 58 116 2,223 M.5-8 1 228 114 228 1 86 86 2,405 $27.97 / ft 2 58 116 2,223 N-8.5 1 360 180 360 1 86 86 2,405 180-ton max. 3 58 174 3,334 P.7-8.5 1 360 180 360 1 86 86 2,405 allow. load: 3 58 174 3,334 P-0.5 1 360 180 360 1 86 86 2,405 108 3 58 174 3,334 P-8.5 1 360 180 360 1 86 86 2,405 13-3/8" 0.480 3 58 174 3,334 Q.8-3 1 360 180 360 1 86 86 2,405 feet: 3 58 174 3,334 Q-0.5 1 360 180 360 1 86 86 2,405 9,288 3 58 174 3,334 M.5-4 1 368 184 368 1 95 95 2,657 3 58 174 3,334 J-5 2 748 187 374 2 95 190 5,314 6 58 348 6,668 G-7 3 1479 247 493 3 95 285 7,971 251-ton max. 12 58 696 13,335 H-7 3 1479 247 493 3 95 285 7,971 allow. load: 12 58 696 13,335 K-6 3 1484 247 495 3 95 285 7,971 177 12 58 696 13,335 B-7 3 1487 248 496 3 95 285 7,971 13-3/8" 0.480 12 58 696 13,335 B-6 3 1507 251 502 3 95 285 7,971 feet: 12 58 696 13,335 C-8 3 1508 251 503 3 95 285 7,971 16,815 12 58 696 13,335 R1-5.9 3 1510 252 503 4 95 380 10,629 12 58 696 13,335 K-7 3 1529 255 510 4 95 380 10,629 13 58 754 14,447 C-4 3 1874 312 625 4 95 380 10,629 251-ton max. 15 58 870 16,669 F-6 3 1879 313 626 4 95 380 10,629 allow. load: 15 58 870 16,669 J-6 3 1942 324 647 4 95 380 10,629 125 16 58 928 17,780 J-4 3 1995 333 665 4 95 380 10,629 13-3/8" 0.480 16 58 928 17,780 Q-9 3 2003 334 668 4 95 380 10,629 feet: 16 58 928 17,780 R-9 3 2003 334 668 4 95 380 10,629 11,875 16 58 928 17,780 448 481 42,380 $1,157,416 1,560 90,480 $1,733,597 $576,181 33

Pile Support Cost, dollars per allowable ton Pile Support Costs WKG 2 Projects 22 20 18 16 y = 90.662x -0.402 R 2 = 0.712 14 12 10 8 40 60 80 100 120 140 160 180 200 220 240 260 Allowable Pile Load, tons (safety factor = 2.0) 35

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

Optimum (Minimum) Required Number of Piles Optimum Allowable Pile Load Histogram First Place Condominiums 36 42 50 54 72 108 125 129 215 30 25 20 15 10 5 0 30 50 70 90 110 130 150 170 190 210 Allowable Pile Load, tons 37

First Place Condominiums - Proposed Designs Allowable Number Estimated Design Load, tons of Piles Footage Original 70 205 15,580 38

First Place Condominiums - Proposed Designs Allowable Number Estimated Design Load, tons of Piles Footage Original 70 205 15,580 Revised 72 180 14,040 SAVE: 25 1,540 $34,250 + cap costs on $346,500 worth of piles 40

First Place Condominiums - Proposed Designs Allowable Number Estimated Design Load, tons of Piles Footage Original 70 205 15,580 Revised 72 180 14,040 Alternate 100 130 $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

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

First Place Condominiums - Proposed Designs Allowable Number Estimated Design Load, tons of Piles Footage Original 70 205 15,580 Revised 72 180 14,040 Alternate 100 164 15,744 SAVE: 16 (not 50) -1,704 ($37,897) (if same pile section is used) 44

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

Questions / Comments? 46