cost-effective pile design using measured

Cost-Effective Pile Design Using Measured Set-up for the I-480 Valley View Bridge

Benjamin White, P.E.

GRL Engineers, Inc.

---Table of Contents---

• Existing Bridge information

• Current Project Information

• Design Phase Pile Test Program Details

• Test Program Results

• Production Testing Info

• Depth Variable Criteria Development

• Thoughts on Cost Savings

• Discussion Topics

Only Required for after lunch presentations

Existing Bridges

• Constructed in 1971

• 4,150 feet in length and 250 feet in height

• Current ADT 180,000

Side Note

One of the first projects where dynamic measurements were collected and CAPWAP performed

I-480 Valley View Bridge ProjectPut a bridge between the bridges

Before After

Project Information

• Design Build letting awarded to Walsh Construction

• Very early recognized the need for a design phase pile test program

• Piers at set locations to match existing structures

• Foundation selection complicated by site soil conditions

Soil Conditions

• Cuyahoga River Valley Alluvial and Glacial Deposits• Primarily silts and/or clays with occasional thin

sand/gravel layers• Sloping bedrock shallow on the Eastern side and 300+

feet near Cuyahoga River

A VERY BORING SOIL BORING

Pile Type Selection

• Analysis was not too in-depth

• Desired crane size → biggest possible hammer → reasonable pile size for hammer

• 18” Closed-End pipe piles

• ICE I-46 Hammer

Design Phase Pile Test Program Goals

• Quantify soil set-up vs. depth through a dynamic testing program at piers 1 through 11. One test pile at each pier (except SLT locations)

• Apply the measured soil set-up to production phase pile testing and create depth dependent driving criteria to optimize pile lengths

• Utilize a resistance factor of 0.8 by performing 3 static load tests, Piers 1, 4, and 9 (results not incorporated into driving criteria directly)

• SLT piers had 5 test piles (reaction piles)

Soil Set-up

• Increase of soil resistance with time

• Disturbed soil remolds around pile

• Pore water pressure dissipates and effective stress of soil against pile increases over time

• Occurs to some degree in almost all soil conditions

Pile Test Program Details• 18” dia closed end pipe piles, 0.5” wall thickness; 120 to 180 feet long

• 1,100 kip (target) nominal resistance

• EOID, BOR1, BOR3, BOR7, BOR30+

ICE I-46 Diesel hammer APPLE 4 – 28 tons

Pile Test Program Details

• 3 Instrumented Static Load Tests, 2000 kip maximum load

• Piles filled with concrete after short term restrikes and SLT performed before BOR30+

Initial Drive and Short-Term Restrike

• 23 piles tested during initial drive• 14 piles tested during just a single restrike (between 1 and 9 days) > 20 bpi on restrike• 3 SLT piles did not have short term restrikes• 5 piles had multiple short term restrikes as initially planned (probably not necessary)• High variability in set-up magnitude, across the site, and within same pier


0

1

2

3

4

5

6

7

0 1 2 3 4 5 6 7 8 9 10

No

rmal

ized

Sh

aft

Res

ista

nce

Time (days)

Normalized Shaft Resistance (CAPWAP) vs. Time (days)


0

1

2

3

4

5

6

7

0.01 0.1 1 10

No

rmal

ized

Sh

aft

Res

ista

nce

Log Time (days)

Normalized Shaft Resistance (CAPWAP) vs. Log Time (days)

Long-Term Restrikes

• 20 piles tested during restrike between 26 and 57 days after ID

• 28 ton drop weight; 3’ to 4’ drop; ~0.25” to ~0.5” permanent set

Ignore this guy who is falling down, Safety First

Long-Term Restrikes

0

2

4

6

8

10

12

14

0 10 20 30 40 50 60

No

rmal

ized

Sh

aft

Res

ista

nce

Time (days)

Normalized Shaft Resistance (CAPWAP) vs. Time (days)

Long-Term Restrikes

0

2

4

6

8

10

12

14

0.01 0.1 1 10 100

No

rmal

ized

Sh

aft

Res

ista

nce

Log Time (days)

Normalized Shaft Resistance (CAPWAP) vs. Log Time (days)

0

200

400

600

800

1000

1200

1400

1600

1800

WA P1 P2 P3 P4 P5 P6 P7 P8 P9 P10 P11

kip

s

EOID Restrike

Comparison of End of Drive and Long term Restrike Resistances

Static Load Testing Instrumentation

• Design/build team was willing to add strain gages to piles at GRL’s request

• Embedded data to be used to refine CAPWAP resistance distribution and justify very high unit resistances, 6 ksf in some cases

• 12 to 15 sister bar strainmeters in each pile, 4 exterior strain gages above grade

PVC isolation for long term measurements

Production pile cut-off was approximately 15 feet below existing grade.ODOT asked that the wires were isolated above the cut-off elevation so they could remove the top section and continue to monitor strains long termThis is not typical and was a HUGE pain to accomplish (all 3 successful!)

Bundled wires after removal of top section

Force = ƐEA

Ɛ – Strain – is measured

A – Area – is known

E – is composite elastic modulus

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

2.6

2.8

3.0

3.2

3.4

3.6

3.8

4.0

4.2

4.4

4.6

4.8

5.0

0 100 200 300 400 500 600 700 800 900 1,000 1,100 1,200

Incre

men

tal

Rig

idit

y, Δ

P/Δ

µε,

kip

s x

10

6(E

A)

Measured Microstrain

Valley View Bridge - Static Load Test - Test Pile P1-1 Incremental Rigidity (ΔP/Δµε) vs. Microstrain

SG Level External - Elev. 635 SG Level 1 - Elev. 635

SG Level 2 - Elev. 621 SG Level 3 - Elev. 607







y = -3.2558E-04x + 1.7950E+00R² = 6.6261E-01

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

2.6

2.8

3.0

3.2

3.4

3.6

3.8

4.0

4.2

4.4

4.6

4.8

5.0

0 100 200 300 400 500 600 700 800 900 1,000 1,100 1,200

Incre

men

tal

Rig

idit

y, Δ

P/Δ

µε,

kip

s x

10

6(E

A)

Measured Microstrain

Valley View Bridge - Static Load Test - Test Pile P1-1 -Incremental Rigidity (ΔP/Δµε) vs. Microstrain

SG Level 3 - Elev. 607 Linear (SG Level 3 - Elev. 607)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

1.6

1.7

1.8

1.9

2.0

2.1

2.2

2.3

2.4

2.5

2.6

2.7

2.8

2.9

3.0

3.1

0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700

Dis

pla

cem

ent

(in

ches

)

Applied Load (Kips)

Static Load Test Results - P1-1

Elastic Compression Davisson Failure Line Load-Displacement Curve

SLT – PDA Comparison

Pile SLT (Davisson) CAPWAP

P1-1 1,450 kips 1,495 kips

P4-1 940 kips 945 kips

P9-1 1,870+ kips (no failure) 2,081+ kips (0.05” set)

NOT TOO BAD!

Depth Variable Driving Criteria

• Implemented based on test program results as well as production pile testing

• ɸ=0.8 for resistance measured at EOID

• ɸ=0.55 or 0.6 as negotiated by ODOT

420

440

460

480

500

520

540

560

580

600

0 100 200 300 400 500 600 700 800 900

Ele

vati

on

, ft

Shaft Resistance, kip

(Pier 3) - Shaft Resistance versus Elevation

EOID

BOR-1: 0.667 days - notmobilized, underestimated

BOR-2: 39.153 days

420

440

460

480

500

520

540

560

580

600

0 100 200 300 400 500 600 700

Ele

vati

on

, ft

Capacity, kip

(Pier 3) - Long-Term Set-Up versus Elevation

420

440

460

480

500

520

540

560

580

600

0 100 200 300 400 500 600 700

Ele

vati

on

, ft

Factored Resistance, kips

(Pier 3) - Factored Compressive Resistance (EOID + Long-Term Set-Up) vs. Elevation

Resistance

factors:

EOID: φ=0.8

Set-Up: φ=0.6

420

440

460

480

500

520

540

560

580

600

0 100 200 300 400 500 600 700

Pil

e T

oe E

levati

on

, ft

Resistance, kips

Figure __ (Pier 3) - Required EOID Resistance vs. Pile Toe Elevation

Theoretical curve based on designsetup values

P3-17

P3-1

Target factored capacity is 555 kips.

Plot assumes following resistance

factors:

EOID: φ=0.8

Set-Up: φ=0.6

Rough Savings Comparison• Existing structures averaged 118 piles per pier and a total of 130,000

lineal feet of pile for each structure

• If based only on EOID and ɸ=0.8, roughly 170,000 lineal feet of piling required

• Final design ~64,000 lineal feet needed

Advantages of Design Phase Test Program

• Once production begins, long term restrike values already realized, no delays, piling well ahead of subsequent operations

• Pile lengths are refined for ordering

• Equipment can be adjusted to optimize production

• Risk and unknowns are minimized

Drawbacks of Design-Phase Test Program

• Project schedule must allow for test program

• Physical location of test program may not be representative

• $$$

• Time

Pile Nerd Discussion Topics…

• Soil Set-up Resistance Factors

• Soil set-up mechanisms, how does installation affect results?

• Is adding instrumentation to SLT worth it? Analysis methods?

• Reliance on CAPWAP analysis results

Final Thought:Always take a close look at your foundations

Thank You

cost-effective pile design using measured

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