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

Size: px

Start display at page:

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

Melinda Dennis
6 years ago
Views:

1 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, P.E., D.GE, F.ASCE Wagner Komurka Geotechnical Group, Inc. 1

2 Talk Outline Support Cost Define Pile Support Cost Based on Available Support Based on Utilized Support Load-Matching Evaluations Philosophy Define Optimum Allowable Pile Load Case Histories Medium/Large Small 2

3 Talk Outline Support Cost Define Pile Support Cost Based on Available Support Based on Utilized Support Load-Matching Evaluations Philosophy Define Optimum Allowable Pile Load Case Histories Medium/Large Small 3

Design Load = 700 T Structure Design Load = 300 T $ 5,000 250 T $ 20.

4 Pile Support Cost: Design Efficiency Based on Available Support Installed Cost = $ 5,000 Allowable Pile Load = 250 T Based on Utilized Support Large Resisted Loads Small Resisted Loads Structure Design Load = 700 T Structure Design Load = 300 T $ 5, T $ per available ton = 3 x $ 5, T = $ per structure design ton 3 x $ 5, T = $ per structure design ton 4

5 Talk Outline Support Cost Define Pile Support Cost Based on Available Support Based on Utilized Support Load-Matching Evaluations Philosophy Define Optimum Allowable Pile Load Case Histories Medium/Large Small 5

6 Load-Matching Evaluation 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, construction-control method, safety factor, etc.) allows optimally matching fixed design components. 6

7 Talk Outline Support Cost Define Pile Support Cost Based on Available Support Based on Utilized Support Load-Matching Evaluations Philosophy Define Optimum Allowable Pile Load Case Histories Medium/Large Small 7

8 900 K Load Matching Evaluation Optimum Allowable Pile Load = Column Design Load Minimum Req d No. of Piles 8

9 Minimum Required Number of Piles Minimum 1 Pile Required? Minimum 2 Piles Required Minimum 3 Piles Required 9

10 900 K Optimum Allowable Pile Load = Column Design Load Minimum Req d No. of Piles Column Design Load = 900 kips Minimum Req d No. of Piles = 3 Optimum Allowable Pile Load = 900 kips 3 piles = 300 kips/pile = 150 tons/pile 10

11 Lower-Than-Optimum Allowable Pile Loads Increased pile support costs each ton of allowable pile load costs more than it would have with higherallowable-load piles. Increased cap support costs each cap is larger than it would have been with higher-allowable-load piles; may increase excavation/material disposal costs, utility relocation costs. Increased number of pile installations. May increase total project drive time, construction control monitoring costs. 11

12 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). 12

13 Talk Outline Support Cost Define Pile Support Cost Based on Available Support Based on Utilized Support Load-Matching Evaluations Philosophy Define Optimum Allowable Pile Load Case Histories Medium/Large Small 13

14 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. 14

15 15

16 16

17 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 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

18 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 optimum allowable pile loads. 18

19 Number of Piles 194 tons 180 tons 227 tons 91 tons Allowable Pile Load Histogram Optimum Allowable Pile Load, tons 19

20 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 optimum allowable pile loads. Select appropriate allowable pile loads, with designteam input. 20

21 Number of Piles 194 tons 180 tons 227 tons 91 tons Allowable Pile Load Histogram tons 180 tons 251 tons Optimum Allowable Pile Load, tons 21

22 Number of Piles For Comparison - Different Case History 30 Number of Piles vs. Optimum Allowable Axial Compression Pile Load Tons 113 Tons Optimum Allowable Axial Compression Pile Load, tons 22

23 Load-Matching Design Approach (continued) Select viable pile type(s) and section(s) for selected allowable loads (91 T, 180 T, and 251 T ). {borings} Estimate individual pile lengths required for selected pile capacities. 23

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

24 Pile Toe Elevation, feet Estimated Ultimate Pile Capacity - Borings Inch-Diameter Pipe Piles Estimated Ultimate Pile Capacity, tons 24

25 Pile Toe Elevation, feet EOID Capacity Set-Up Pile Test Program Results Long-term Capacity Capacity Profiles Estimated Ultimate Capacity, tons 25

26 Load-Matching Design Approach (continued) Select viable pile type(s) and section(s) for selected allowable pile loads (91 T, 180 T, 251 T ). 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. 26

27 Number of Piles 194 tons 180 tons 227 tons 91 tons Allowable Pile Load Histogram tons 180 tons 251 tons Optimum Allowable Pile Load, tons 27

28 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 28

29 Load-Matching Design Approach (continued) Select viable pile type(s) and section(s) for selected allowable pile loads (91 T, 180 T, 251 T ). 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. 29

30 $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 30

31 $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 31

32 Talk Outline Support Cost Define Pile Support Cost Based on Available Support Based on Utilized Support Load-Matching Evaluations Philosophy Define Optimum Allowable Pile Load Case Histories Medium/Large Small 32

33 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. 33

34 Number of Piles Optimum Allowable Pile Load Histogram Condominiums Optimum Allowable Pile Load, tons 34

35 Condominiums - Proposed Designs Allowable Number Estimated Design Load, tons of Piles Footage Original ,580 35

36 Number of Piles Optimum Allowable Pile Load Histogram Condominiums Optimum Allowable Pile Load, tons 36

37 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 37

38 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? 38

39 Number of Piles Optimum Allowable Pile Load Histogram Condominiums Optimum Allowable Pile Load, tons 39

40 216-ton column load 216-ton column load 72 tons 72 tons 72 tons 100 tons 100 tons 100 tons 40

Condominiums - Proposed Designs Allowable Number Estimated Design Load, tons of Piles Footage Original 70 205

41 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) 41

42 Conclusions Consider using higher-capacity piles (when building loads warrant) Consider matching (optimizing) allowable pile loads to column loads Evaluate design options/alternatives using actual column loads and allowable pile load histogram All should result in more-cost-effective driven-pile foundations 42

43 Questions / Comments? 43

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