TPF-5(264) Passive Force- Deflection Behavior for Skewed …sp.bridges.transportation.org/Documents/2016... · 2017-01-26 · TPF-5(264) Passive Force- Deflection Behavior for Skewed

TPF-5(264) Passive Force-Deflection Behavior for Skewed Abutments

Kyle RollinsCivil & Environmental EngineeringBrigham Young University

T-3 Technical Committee for Seismic DesignAASHTO Bridge Sub-Committee Annual MeetingMinneapolis, Minnesota

FHWA Pooled Fund Sponsors

Utah DOT – Lead Agency Oregon DOT Montana DOT California DOT New York DOT Minnesota DOT Wisconsin DOT FHWA

Background Passive Pressure for non-skewed abutments (Maroney (1995),

Duncan and Mokwa (2001), Rollins and Sparks (2002), Rollins and Cole (2006), Lemnitzer et al (2009)

Passive force best estimated using log-spiral method Peak passive force mobilized at displacement of 0.03H to 0.05H Hyperbolic curve best represents passive force-displacement curve

PP

Log Spiral Passive Force

γ = moist unit weightϕ = Soil friction angleδ = wall friction angleβ=backfill slope angleH= height of back wallWw = width of back wallKp=passive pressure

coefficient

Pp = 0.5γH2 Ww Kp

Presumptive Passive Pressure in Guide Spec.

pp=uniform passive pressure on wall (ksf)Hw = height of back wall (ft)Ww= width of back wall (ft)

pp=2Hw/3 for cohesionless soil (<30% fines)pp=5 ksf for cohesive soil (>15% clay) with undrained strength > 4 ksf

Pp = ppHw Ww

Background

Unclear: Effect of skew on passive force

PP

Skewed Bridge Abutment Overview ≈ 40% of 600,000 bridges in US are skewed Current AASHTO design code does not

consider any effect of skew on passive force Observations of poor performance of skewed

bridges

Shamsabadi et al. 2006

Damage to Skewed Integral Abutments

(Steinberg & Sargand, 2010)

Earthquake Damage to Skewed Bridges(Paine, Chile)

Top Bridge

Bottom Bridge

Top Bridge

Bridge decks have rotated and bridge was demolished

Bottom Bridge

Bridge deck was offset and was eventually demolished

Top Bridge

Bridge remained in service after the earthquake

Damage rate for skewed bridges was twice that of non-skewed bridges (Toro et al 2013)

Passive Force From Inertia

Passive force contributes to resistanceUsing smaller passive force (lower Kp)

may be conservative

Passive Force from Lateral Spreading

Passive force often drives displacement Selection of smaller passive force (lower Kp)

may be unconservative

Liquefaction

Driving Force on Skewed Abutments

Interaction of Forces on Bridge Abutment

Deck Length, L

Skew Angle, θ

PLPL

Numerical Analysis of Skewed Abutments

(5th NSC, Shamsabadi et al., 2006)

23 m (75 ft) wide abutment with 2.4 m (8 ft) high backwall

Results of Numerical Analysis

(5th NSC, Shamsabadi et al., 2006)

Objectives1. Determine static passive force-displacement curves for

skewed abutments from large-scale tests2. Provide comparisons of behavior of skewed abutments

with that of normal abutments.3. Evaluate the effect of wingwalls on skewed abutment

response.4. Develop design procedures for calculating passive

force-displacement curves and shear-displacement or skewed abutments.

“One good test is worth a thousand expert opinions.”

Werner Von Braun

Designer of Saturn V Moon Rocket

Healthy Skepticism for Tests A theory is something nobody believes,

except the person who proposed it. An experiment (test) is something

everybody believes,

--Albert Einsteinperformed it

except the person who

Initial Laboratory Testing

Test Layout

No Skew

Plan view:

Elevation view:

1.22 m (4 ft)

0.6 m (2 ft)

Test Procedure

Plan view:

Elevation view:

Test Procedure

Plan view:

Elevation view:

Test “Abutment”

15°

Test “Abutment”

30°

Test “Abutment”

45°

Displacement: 60 mm 2.5” (0.10H)Load measurements:• Longitudinal• Vertical• Transverse

Rollers Below Base of “Abutment”

Surface Failure Rupture - 30º Skew

30º

Backfill Soil Properties Gradation and Strength

Property ValueClassification SP or A-1-b

Cu 3.7

Cc 0.7

Rc 98%

γ 17.8 kN/m3

ϕ 46ºδ 33.2º

Passive Force-Displacement Curves

Reduction Factor for Skew Effects

Rskew= PP(skew)/Pp (No-skew)

where Rskew is a function of skew angle, and wall width is equal to non-skewed (projected) width.

Rskew= 8x10-5θ2 – 0.018 θ + 1.0

(ASCE, J. of Bridge Engrg., Rollins and Jessee 2013)

Passive Force Reduction Factor vs. Skew

Rskew = 8x10-05θ2 - 0.018θ + 1R² = 0.98

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 15 30 45 60 75 90

Red

uctio

n Fa

ctor

, Rsk

ew

Skew Angle, θ [degrees]

Lab Tests

Numerical Analysis

Proposed Reduction Line

(ASCE, J. of Bridge Engrg., Rollins and Jessee 2013)

Passive & Shear Stress vs. Skew


Large Scale Field Testing

Field Test Setup - Plan View

12.75 inch Dia. Steel Pipe Piles

11 ft wide x 5.5 ft high Pile Cap

24 ft

22 ft

Transverse Wingwalls2 x 4 ft Reinforced Concrete blocks

4 ft Dia. Bored PileSheet Pile Wall Section AZ-18

2 – 600 kip Actuators

Field Test Setup Elevation View

11 ft m wide x 5.5 ft high x 15 ft long Pile Cap

6 ft6.4m

4 ft Dia. Bored PileSheet Pile Wall Section AZ-18

2 – 600 kip Actuators 12.75 inch Dia. Steel Pipe Piles

Sand backfill properties

Poorly graded sand (SP/A-1-b) 96% relative compaction ϕ = 41° c = 100 lbs/ft2

γmax = 111.5lbs/ft3

No Skew - 0° Test Setup

15° Skew Test Setup



Test completed at 3.21 in (81.6 mm) of displacement

Test completed at 3.43 in (87.2 mm) of displacement

Heave Geometry at Test Completion0º Skew 45º Skew

Field Test Methodology 0 2 4 6 8

0

1,000

2,000

3,000

4,000

5,000

0

200

400

600

800

1,000

1,200

0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50

Pile Cap Deflection [cm]

Long

itudi

nal F

orce

[kN

]

Long

itudi

nal F

orce

[kip

s]

Pile Cap Deflection [in]

Total Load

Baseline Resistance

Lateral Backfill Resistance

Passive Force vs. Displacement0 2 4 6 8 10

0

500

1,000

1,500

2,000

2,500

0

100

200

300

400

500

600

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0


Pass

ive

Forc

e [k

N]

Pass

ive

Forc

e [k

ips]


0° Skew15° Skew30° Skew45° Skew

0.02

H

0.03

H

0.04

H

0.05

H


Rskew = 8x10-05θ2 - 0.018θ + 1R² = 0.98

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 15 30 45 60 75 90

Red

uctio

n Fa

ctor

, Rsk

ew


Lab TestsNumerical AnalysisField Tests (This Study)Proposed Reduction Line

Failure Geometry for Zero-Skew Test

0 1 2 3 4 5 6-0.30

0.20

0.70

1.20

1.70

-1.0

0.0

1.0

2.0

3.0

4.0

5.0

6.00 5 10 15 20

Distance from Cap Face on Line Parallel to Direction of Push [m]

Elev

atio

n B

elow

Top

of C

ap [m

]

Elev

atio

n B

elow

Top

of C

ap [f

t]

Distance from Cap Face on Line Parallel to Direction of Push [ft]

Upper Shear PlaneLower Shear PlaneHeave

𝜙𝜙𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚 = 41°

𝛼𝛼 = 45 − 𝜙𝜙′/2

𝜙𝜙 ≈ 40°α

Comparison of Failure GeometriesRankine Failure Geometry

Log-Spiral Failure Geometry

Ep

Interface Forces with Respect to Skew

Shear force vs. transverse displacement

020406080

100120140160180200

-0.3 -0.25 -0.2 -0.15 -0.1 -0.05 0

App

lied

Shea

r For

ce [k

ip]

Transverse Displacement [in]

30° skew15° skew

45º skew

Test Setup for MSE Wingwall Tests

15° Skew 30°

Skew

Welded Wire Grid Reinforcement (SSL)

No Skew - 0° Test Setup

15º Skew Test with MSE Wingwalls

Field Test with 30º Skew & MSE Walls

0.0

0.5

1.0

1.5

2.0

2.5

3.00.0 5.0 10.0 15.0 20.0 25.0

MSE

Win

gwal

l D

ispl

acem

ent (

in)

Distance From Pile Cap (ft)

0.24 0.831.72 2.733.18

0.0

0.5

1.0

1.5

2.0

2.5

3.00.0 5.0 10.0 15.0 20.0 25.0

MSE

Win

gwal

lD

ispl

acem

ent (

in)

Distance From Pile Cap (ft)

0.24 0.831.72 2.733.18

0ºSk

ew

3.35 m

45ºS

kew

11

Passive Force-Displacement curves

0.01

H

0.02

H

0.03

H

0.04

H

0.05

H

0.0 2.0 4.0 6.0 8.0 10.0

0

500

1,000

1,500

2,000

2,500

3,000

0

100

200

300

400

500

600

700

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

Pile Cap Displacement, Δ [cm]

Pass

ive

Forc

e [k

N]

Pass

ive

Forc

e [k

ips]

Backwall Displacement, Δ [in]

0 Degree Skew30 Degree Skew15 Degree Skew45 Degree Skew


Rskew = 8x10-05θ2 - 0.018θ + 1R² = 0.98

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 15 30 45 60 75 90

Red

uctio

n Fa

ctor

, Rsk

ew


Lab Tests

Numerical Analysis

Field Tests (This Study)


Geometry Effects? Field and Lab tests involved W/H ratios of 2.0

Does this ratio impact the results?

Laboratory Wall

2 ft

4 ft

Field Wall

5.5 ft

11 ft

Field Test with 3 ft Backfill - W/H=3.7

11 ft wide x 5.5 ft high x 15 ft long Pile Cap

3 ft

4 ft Dia. ReinforcedConcrete Shaft

12 in Dia. Steel Pipe Piles

2- 600 kip Actuators


0

20

40

60

80

100

120

140

160

180

200

0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00

Pass

ive

Forc

e [k

ips]

Pile Cap Displacement [in]

0 Degree Skew15 Degree Skew30 Degree Skew45 Degree Skew

0.01

H

0.02

H

0.03

H

0.04

H

0.05

H

0.06

H

0.07

H

0.08

H

0.09

H


Rskew = 8x10-05θ2 - 0.018θ + 1R² = 0.98

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 15 30 45 60 75 90

Red

uctio

n Fa

ctor

, Rsk

ew


Lab Tests

Numerical Analysis



45º Skew with RC Wingwalls



Tests with RC Wingwalls


Rskew = 8x10-05θ2 - 0.018θ + 1R² = 0.98

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 15 30 45 60 75 90

Red

uctio

n Fa

ctor

, Rsk

ew


Lab Tests

Numerical Analysis



Heave and Crack Patterns


Rskew = 8x10-05θ2 - 0.018θ + 1R² = 0.98

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 15 30 45 60 75 90

Red

uctio

n Fa

ctor

, Rsk

ew


Lab Tests

Numerical Analysis



Gravel Backfill Properties Sandy Gravel backfill material (A-1-a) Compacted to 95% of Modified Proctor Max. Density Proctor max density was 141 pcf at 6% optimum

moisture content GRS Select Backfill Gradation

Sieve Size Percent Passing

2 inch 100

1 inch85 - 100

3/8 inch60 – 75

No. 1030 – 42

No. 4014 – 24

No. 2006 –12

0 1 2 3 4 5 6 7 8 9 10

0

200

400

600

800

1000

1200

1400

1600

050

100150200250300350400450500

0 1 2 3 4

Longitudinal Deflection [cm]

Pass

ive

Forc

e [k

N]

Pass

ive

Forc

e [k

ip]

Longitudinal Deflection [in]

0 deg 3.5ft

30 deg scaled to 3.5ft

0.01

H

0.09

H

0.08

H

0.07

H

0.06

H

0.05

H

0.04

H

0.03

H

0.02

H

Test with Gravel Backfill


Rskew = 8x10-05θ2 - 0.018θ + 1R² = 0.98

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 15 30 45 60 75 90

Red

uctio

n Fa

ctor

, Rsk

ew


Lab Tests

Numerical Analysis



Passive Force Tests with GRS Backfill

GRS fabric - 0° Test

GRS fabric - 30° Test

Passive Force-Deflection for GRS

0 1 2 3 4 5 6 7 8 9 10

0

200

400

600

800

1000

1200

1400

1600

0.0

50.0

100.0

150.0

200.0

250.0

300.0

350.0

400.0

0 1 2 3 4

Longitudinal Deflection [cm]

Pass

ive

Forc

e [k

N]

Pass

ive

Forc

e [k

ip]

Longitudinal Deflection [in]

0° 3.5 ft GRS

30° 3.5 ft GRS


Rskew = 8x10-05θ2 - 0.018θ + 1R² = 0.98

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 15 30 45 60 75 90

Red

uctio

n Fa

ctor

, Rsk

ew


Lab Tests

Numerical Analysis



Overall Best Fit – Without 90º Skew Point

00.10.20.30.40.50.60.70.80.9

1

0 15 30 45 60 75 90

Redu

ctio

n fa

ctor

, Rsk

ew

Skew Angle, θ (Degrees)

Shamsabadi & Rollins 2014

Rskew = e(-ϴ/45°)

Conclusions: Significant decrease in passive force with increase in

skew angle.• Numerical Analysis• 8 Small Scale Lab Tests• 11 Large Scale Field tests

Simple reduction factor can account for the effect of skew angle on passive force

Reduction factor not much affected by wall W/H ratio Reduction factor not much affected by sand, gravel, or

GRS backfill type Passive force typically mobilized at Δ/H ≈ 3 to 5% Shear resistance largely mobilized with 0.2 to 0.3 inches

of movement at interface

Proposed Revisions to Guide SpecWhen an abutment is skewed at an angle,θ,relative to the alignment as shown in Figure XX, the passive force, Pp, shall be reduced using the equation

Pp = Pp no-skew Rskew

Where: Pp no-skew is the passive force obtained using analysis procedures or presumptive pressures for no skew and Rskew = e-(θ /45) and where, θ, is the skew angle in degrees. The backwall width, Ww, shall be measured normal to the lane width.

Proposed Revisions to Guide Spec

When an abutment is skewed at an angle,θ, relative to the alignment as shown in Figure XX, the passive force, Pp, shall be reduced using the equation

Pp = Pp no-skew Rskew

Where: Pp no-skew is the passive force obtained using analysis procedures or presumptive pressures for no skew and Rskew = e-(θ /45) and where, θ, is the skew angle in degrees. The backwall width, Ww, shall be measured normal to the lane width.

Ww

θ

Adjustment for Width & Skew

PpH = 28.5 k/ft

50 ft

θ = 30º

For 0º skew conditionPpH = (28.5 k/ft) (50ft) = 1425 k

Compute skew reduction factorRskew= e(-ϴ/45º) = e(-30º/45º) = 0.51

For 30º skew conditionPpH = (1425 k)(0.51) = 727 k

PpH

Passive Force-Displacement

50 ft

θ = 30ºPpH

PpH

Displacement (in)

For a 6 ft high backwall:Peak at 0.03H = 0.03(6 ft)(12in/ft)

= 2.2 in

2.2 in

727 k

= 727k

Shear Force-Displacement

50 ft

θ = 30º For a δ=28º = 0.70φT = cA + PpHtanδ

= 0 + (727 k) tan(28º) = 387k

PpH=727k

T

Displacement (in)

Peak at 0.25 in

0.25 in

387k

T = 387k

Bi-linear Passive Force vs. Displacement

0 2 4 6 8 10

0

500

1,000

1,500

2,000

2,500

0

100

200

300

400

500

600

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0


Pass

ive

Forc

e [k

N]

Pass

ive

Forc

e [k

ips]



0.02

H

0.03

H

0.04

H

0.05

H

Hyperbolic Passive Force vs. Displacement

0 2 4 6 8 10

0

500

1,000

1,500

2,000

2,500

0

100

200

300

400

500

600

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0


Pass

ive

Forc

e [k

N]

Pass

ive

Forc

e [k

ips]



0.02

H

0.03

H

0.04

H

0.05

H

Questions?

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