Seismic Evaluation ofPrestressed and Reinforced ConcretePile-Wharf Deck Connections

Jennifer SoderstromUniversity of Washington

Introduction

• Ports represent a large economic investment for a region

• Direct damage to the port of Kobe, Japan estimated to exceed U.S.$11 billion

• It is worthwhile to evaluate the seismic performance of port facilities

Typical Wharf Section

Pile-Deck Connections

• Piles are the sole supports for large gravity loads

• Detailing must be sufficient to allow pile forces to develop and hinges to form

• Repair and inspection can be difficult, so a connection should remain undamaged in a large seismic event

Prototype Connections

• Survey of Wharves in Los Angeles, Oakland and Seattle

• Connection types used included:

– Precast Pile Connection

– Pile Extension Connection

– Batter Pile Connection

Precast Pile Connection

• Most common connection was a 24 in octagonal prestressed pile

• Pile set 2 in into deck

• Hooked dowels grouted in pile ducts

• Varying development lengths

Pile Extension Connection

• Cast prior to deck if length > 6 in

• Hooked dowels grouted in pile ducts and passing through extension

• Varying development lengths

• Extended spiral in some connections

Pile Section

• 24 in octagonal prestressed pile most common• Details varied

Test Methodology

Connection types investigated in this study:

– Pile Extension Connections

• No spiral reinforcement in joint region

• Moderate spiral reinforcement in joint region

– Precast pile connections

• No axial load

• 222 kip axial load

Specimen 1: Pile Extension

Specimen 2: Pile Extension w/Spiral

Specimens 3&4: Precast Pile

Test Setup

Axial Load System

Testing Procedure

• Modified ATC-24 loading sequence

• Lateral displacement from 0.05% to 10.6% drift

% drift = lateral deflection / pile length

-8

-6

-4

-2

0

2

4

6

8

0 5 10 15 20 25 30 35 40Cycles

0.05% drift

9.0% drift

Experimental Results

• Test observations

• Force-deflection history

• Moment-curvature history

– Average curvature

– Strain curvature

• Strain distribution

• Incremental strain distribution

Test Observations – pile cracking

Cracking at 1.0% drift

1 2 3 4

Test Observations – deck cracking

Specimen 2

Specimen 3

Specimen 1

Test Observations – end of tests 1, 2

Specimen 1 Specimen 2

Test Observations – end of tests 3, 4

Specimen 3 Specimen 4

Force-Deflection History – specimen 1Peak load = 26.5 kips at 4.5% drift

-40

-30

-20

-10

0

10

20

30

40

-10 -8 -6 -4 -2 0 2 4 6 8 10Lateral Deflection (in)

Force-Deflection History – specimen 3Peak load = 30.7 kips at 3.0% drift

-40

-30

-20

-10

0

10

20

30

40

-10 -8 -6 -4 -2 0 2 4 6 8 10Lateral Deflection (in)

Force-Deflection History – specimen 4Peak load = 38.1 kips at 1.5% drift

-40

-30

-20

-10

0

10

20

30

40

-10 -8 -6 -4 -2 0 2 4 6 8 10Lateral Deflection (in)

Moment-Curvature History

• Calculated over intervals 0 to ½ diam. and ½ to 1 diam.

Average curvatures

curcur

NSave hW

Moment-Average Curvature

• Specimen 1

• Lower curvature 2-3 times greater than upper curvature

-4000

-3000

-2000

-1000

0

1000

2000

3000

4000

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

Average Curvature (10-3

rad/in)

-4000

-3000

-2000

-1000

0

1000

2000

3000

4000

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

Average Curvature (10-3

rad/in)

½ to 1 diam. (upper)

0 to ½ diam. (lower)

Moment-Average Curvature

• Specimen 4

• Lower curvature 8-10 times greater than upper curvature

-4000

-3000

-2000

-1000

0

1000

2000

3000

4000

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

Average Curvature (10-3

rad/in)

-4000

-3000

-2000

-1000

0

1000

2000

3000

4000

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

Average Curvature (10-3

rad/in)

½ to 1 diam. (upper)

0 to ½ diam. (lower)

Moment-Curvature HistoryStrain curvatures

• Calculated at distances of 8.25, 0 and –5 in from interface

str

NSstr W

Moment-Strain Curvature

• Specimen 2

• Strain curvatures highest in pile section

-4000

-3000

-2000

-1000

0

1000

2000

3000

4000

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

Curvature (10-3 rad/in)

Mom

ent (

kip-

in)

-4000

-3000

-2000

-1000

0

1000

2000

3000

4000

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

Curvature (10-3 rad/in)

Mom

ent (

kip-

in)

-4000

-3000

-2000

-1000

0

1000

2000

3000

4000

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

Curvature (10-3 rad/in)

Mom

ent (

kip-

in)

8.25 in interface -5 in

Moment-Strain Curvature

• Specimen 4

• Strain curvatures highest in deck

-4000

-3000

-2000

-1000

0

1000

2000

3000

4000

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

Curvature (10-3 rad/in)

Mom

ent (

kip-

in)

-4000

-3000

-2000

-1000

0

1000

2000

3000

4000

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

Curvature (10-3 rad/in)

Mom

ent (

kip-

in)

-4000

-3000

-2000

-1000

0

1000

2000

3000

4000

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

Curvature (10-3 rad/in)

Mom

ent (

kip-

in)

8.25 in interface -5 in

Strain Distribution

Specimens 1, 2• Peak strains between interface and ½ diameter• Yield at 1.0% drift

-10

-5

0

5

10

15

-1000 1000 3000 5000 7000

Strain

Yield

Pile

Deck

Strain DistributionSpecimen 3• Peak strains in deck, 5 in below interface• Yield at 0.75% drift• High strains in lower bar

-10

-5

0

5

10

15

-1000 1000 3000 5000 7000

Strain

Pile

Deck

Yield

Strain Distribution

Specimen 4• Peak strains in deck, 5 in below interface• Yield at 1.0% drift

-10

-5

0

5

10

15

-1000 1000 3000 5000 7000

Strain

Pile

Deck

Yield

Incremental Strain Distribution

• Strains at 1000 kip-in moment, first cycles• Exponential distribution indicates good bond

-10

-5

0

5

10

15

-8000 -4000 0 4000 8000

Strain

0.75%

1.00%

1.25%

1.50%

1.75%

2.00%

3.00%

4.50%

6.00%

Specimen 2

Good bond within deck

Incremental Strain Distribution

• Strains at 1000 kip-in moment, specimen 3• Strains at 1500 kip-in moment, specimen 4

-10

-5

0

5

10

15

-8000 -4000 0 4000 8000

Strain

0.75%

1.00%

1.25%

1.50%

1.75%

2.00%

3.00%

4.50%

6.00%

Specimen 3

Slip in top 5 in of deck

Good bond in pile section

Conclusions

• All connections had large rotational capacities

• Precast pile connections were initially stiffer and stronger, but experienced greater deterioration than pile extensions• A moderate axial load increased strength by 25%, but caused greater deterioration at drift levels above 2.0%

Conclusions

• Pile extensions dissipated more energy at high drift levels through continued flexural cracking, while damage in the precast connection was concentrated in large cracks near the interface

• Precast pile connections experienced bond slip and rocking in early load cycles

Conclusions

• The addition of spiral reinforcement in the joint region did not appear to have a significant effect on pile extension performance

Seismic Evaluation ofPrestressed and Reinforced ConcretePile-Wharf Deck Connections

Jennifer SoderstromUniversity of Washington