Application of Advanced Materials and New Detailing for ABC

Column ConnectionsMostafa Tazarv, PhD

Assistant Professor

Department of Civil and Environmental Engineering

South Dakota State University (SDSU)

Presentation Prepared for ABC-UTC

Jan. 29, 2016

Outline

- Intro to ABC Column Connections

- Advanced Materials

- UHPC-Filled Duct Connections

- Low-Damage Precast Columns

-Columns w/ Couplers

-Cap Beam Pocket Connections

2

Bridge Column Roles

Conventional Columns:

Support superstructure

Provide sufficient resiliency

Dissipate energy

Allow for significant damage but

collapse is prevented

3

New Roosevelt Bridge in Stuart, Florida, USA

Bridge Column Roles

Can we develop precast columns with

better seismic performance compared

to cast-in-place columns?

Can we develop precast columns which

behave similarly to cast-in-place

columns in high seismic regions?

4

New Roosevelt Bridge in Stuart, Florida, USA

Column Connections:

Precast Column Connections

Column to Cap Beam

Column to

Footing

Pocket Connection Grouted Duct Connection Rocking Connection Bar Coupler Connection Pipe-pin connection Novel Plastic Hinges

Pocket/Socket Connection Grouted Duct Connection Rocking Connection Bar Coupler Connection Pipe-pin Connection Novel Plastic Hinges

5

Novel Materials

Introduction

6

Advanced Materials

Advanced Materials:

Reduce damage, reduce residual strains,enhance compressive and tensile strengths ofconcrete, enhance durability, and many more

Shape Memory Alloy (SMA)

Ultra-High Performance Concrete (UHPC)

Engineered Cementitious Composite (ECC)

Fiber Reinforced Polymer (FRP)

Built-in Rubber Pad

7

Advanced Materials: SMA

Shape memory effect

Superelastic effect

0

200

400

600

800

1000

0

25

50

75

100

125

150

0 5 10 15 20

Str

ess

(M

Pa

)

Str

ess

(k

si)

Strain (%)

#10 (32 mm) SMA Bar

#8 (25 mm) Mild Bar

Strain Recovery after

a 6% Strain CycleVideo from

youtube.com

Two Main Characteristics:

8

Advanced Material: UHPC

Fiber-reinforced cementitious concrete

Made with very fine aggregates in size of dust

Usually with 2% volumetric steel fibers

Better durability than concrete

More than 22,000 psi (150 MPa) compressive strength

Significantly higher tensile strength and strain capacity

Courtesy: Dr. Graybeal of FHWA9

Courtesy: Lafarge

Advanced Materials: ECC

Fiber-reinforced cementitious concrete

Made with fine aggregates

Usually with 2% volumetric PVA fibers

Compressive strength in the range of conventional concrete

Significantly higher tensile strain capacity, 4%

Li (2008)

Column Damage

Conventional Column Damage:

Cover concrete failure

Core concrete failure

Reinforcement yielding

Large residual strain in bars

Reinforcement buckling and fracture

Str

ess

Strain

Compression

Concrete

Str

ess Reinforcing

Steel

Cover

Strain

Tension

Core

Column Section

UHPC-Filled Duct Connections

Emulative Connection

12

Grouted Duct Connections

Column to Cap Beam Connection

Column to Footing Connection

Extended ColumnReinforcing Bar

PrecastColumn

Cap BeamGrouted Duct

Column Section A-A Column Section B-B

A A

B B

Column Section A-A

Extended

Column

Bars

PrecastColumn

Footing

Grouted

Duct

A A

B B

Section B-B

Grouted

Duct

Normal grout as duct filler

We proposed UHPC as duct filler to connect precast columns to shallow cap beams and footings

13

UHPC-Filled Duct Connections

Connection Bond Performance

Two experimental phases

Implementation in Bridge Columns

Concrete

Du

ct

Bar

UH

PC

Threads

Pull Force

14

UHPC-Filled Duct Connections

Concrete

Duct

Bar

UH

PC

Threads

Pull Force

UHPC-Filled Duct Connections: Bond Bond strength of bar in UHPC was eight times higher than

that in conventional concrete

Design Development Length:

Compared to conventional connections designed according to:

ACI 318-11

AASHTO LRFD 2010

Grout-Filled Ducts

At least 50%

Reduction of

Embedment

Length

Ld = max (Ld,duct, Ld,bar) (2-13)

US Customary Unit SI Unit

𝐿𝑑 ,𝑑𝑢𝑐𝑡 =𝑑𝑏

2 .𝑓𝑠

27𝑑𝑑 . 𝑓′𝑐

𝐿𝑑 ,𝑑𝑢𝑐𝑡 =𝑑𝑏

2 . 𝑓𝑠

2.24𝑑𝑑 . 𝑓′𝑐

(2-14)

𝐿𝑑 ,𝑏𝑎𝑟 =𝑑𝑏 .𝑓𝑠

120 𝑓 ′ 𝑈𝐻𝑃𝐶

𝐿𝑑 ,𝑏𝑎𝑟 =𝑑𝑏 . 𝑓𝑠

9.96 𝑓 ′ 𝑈𝐻𝑃𝐶

(2-15)

(psi, in)

15

UHPC-Filled Duct Connections

UHPC-Filled Duct Connections: Column Test Two Column Models

- Conventional Materials in Plastic Hinge (“PNC”)

- SMA-ECC in Plastic Hinge (“HCS”)

Connection

- UHPC-Filled Duct Connections

Column Geometry

- Half-Scale

- Height: 9 ft (2.74 m)

- Diameter: 24 in. (610 mm)

- 11- #8 (Ø25 mm) Longitudinal Bars (ρl=1.92%)

- Spiral, ρs=1.0%

- Axial Load Index: 10% (200-kip axial load)

16

UHPC-Filled Duct Connections

UHPC-Filled Duct Connections: Column Test

-356

-256

-156

-56

44

144

244

344

-80

-60

-40

-20

0

20

40

60

80

-12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12

Ba

se S

hea

r

(kN

)

Ba

se S

hea

r

(kip

s)

Drift (%)

PNC Column

CIP Column

No UHPC-filled duct connection damage

after10% drift ratio cycles 17

Field Applications

Caltrans is designing a multi-span bridge based on this study

18

UHPC-Filled Duct Connections:

Precast SMA-ECC Column

Improved Seismic Performance

19

A Low-Damage Precast Column

Goal: Develop precast columns with improved

seismic performance over CIP

Ultra-High Performance Concrete (UHPC)

Shape Memory Alloy (SMA)

Engineered Cementitious Composite (ECC)

Also used:

Self-Consolidating Concrete (SCC)

Conventional Concrete

Conventional Steel Bars

Corrugated Steel Ducts (or PT Ducts)

Headed Bar Couplers (or Mechanical Splices)

20

Low-Damage Precast Column

21

Low-Damage Precast Column

0

50

100

150

200

250

300

350

0

10

20

30

40

50

60

70

80

0 1 2 3 4 5 6 7 8 9 10 11

Base S

hear

(kN

)

Base S

hear

(kip

s)

Drift (%)

HCS Column

CIP Column

AASHTO

Displacement

Demand Limit

μ =7.36

22

Low-Damage Precast Column

SMA-ECC Precast Column

@ 10% Drift Ratio

Cast-in-Place Column

23

Low-Damage Precast Column

79% Lower Residual Displacements

0

1

2

3

4

5

6

7

8

0 1 2 3 4 5 6 7 8 9 10 11

Resid

ual D

rift

(%

)

Peak Drift (%)

HCS Column

CIP Column

After 10% drift cycle24

Field Applications

SR99 (Alaskan Way) Viaduct, Seattle, Washington

25

SMA-Reinforced ECC Columns:

http://www.wsdot.wa.gov/projects/viaduct

Mechanical Bar Splice Connections

26

Bar Coupler Connections

Mechanical Bar Couplers:

Headed Bar Coupler[hrc-usa.com]

Threaded Bar Coupler[erico.com]

Grouted Sleeve Coupler

Bar Grip Coupler Shear Screw Coupler[barsplice.com]

[splicesleeve.com]

[daytonsuperior.com]

Bar Coupler Connections

Column to Cap Beam Connections

Connection Type:

Column to Footing Connections

PrecastColumn

Cap Beam

Bar Coupler

Connections are possible for many types of couplers but test data is very limited

PrecastColumn

Footing

Grouted

Sleeve

CIPPedestal

Bar

Couplers

PrecastColumn

Cap Beam

ClosurePour

Footing

PrecastColumn

Bar

CouplersClosurePour

28

Bar Couplers in Bridge Columns (Only Grouted)

Field Application

• Utah• Florida• Colorado

Project in Florida, Column Section Project in Utah, Grouted Coupler(Culmo, 2009) (NCHRP Scan Team Report, 2012)

I-225 and Colfax Ave-Denver CO

29

Generic Model for Couplers

30

Cou

ple

r

Reg

ion

Lsp

db

a.db

Bar

Reg

ion

a.db

ß.Lsp

Bar

Reg

ion

Rig

id

Len

gth

Lcr

Str

ess

Strain

Bar Region

CouplerRegion

Column Section

Hsp

Lsp

Elem. 1

Elem. 2

Ele

m.

3

L

Footing

Co

up

lers

𝜇𝑠𝑝

𝜇𝐶𝐼𝑃= (1 − 0.18𝛽)

𝐻𝑠𝑝

𝐿𝑠𝑝

0.1𝛽

Stress-strain model, design equation, and the plastic hinge length were verified using test data.

Couplers can reduce the displacement ductility by 40%.

Cap Beam Pocket Connections

Emulative Behavior

31

Cap Beam Pocket Connection

Pocket/Socket Connections

Extended ColumnReinforcing Bar

PrecastColumn

Precast Cap Beam

Steel Pipe

Extended Column

PrecastColumn

Precast Cap BeamSteel Pipe

Cap Beam Pocket Connection

Connection Type:

Footing Pocket Connection Footing Pocket Connection

Some studies differentiated the two connections but they are essentially thesame and can be generally categorized as “Pocket Connections”

Precast orCast-in-Place

Footing

Extended Column

Steel Pipe

PrecastColumn

PrecastColumn

Pile Shaft

Steel

Pipe

Field Applications:

Pocket/Socket Connections

Florida Iowa Louisiana Minnesota South Carolina Texas Washington

Redfish Bay Project Steel Pile to Pile Cap, IA

(Brenes et al., 2006)

(Khaleghi et al., 2012)

No

n-S

eism

ic D

etai

ling

Seis

mic

Det

ailin

g

Constructability

Five alternatives evaluated

(a) Cast-in-Place Pocket Connections

PrecastColumn

Precast Cap Beam

Steel Pipe

CIP Pocket

Alt-1

Steel Bars

Cap Beam Sectionw/ Pocket

Pocket

PrecastColumn

Precast Cap Beam

Steel Pipe

Steel Bars

Cap Beam Sectionw/ Pocket

Pocket

CIP Pocket

Alt-2 Lumped

Bars

Steel Bars

Cap Beam Sectionw/ Pocket

Pocket

CIP Pocket

Alt-3

PrecastColumn

Precast Cap Beam

Steel Pipe

PrecastColumn

Precast Cap Beam

Steel Pipe

Steel Bars

Cap Beam Sectionw/ Pocket

Pocket

CIP Pocket

Alt-4 Lumped

Bars

Design Guidelines and Examples

35

Design Guideline:

SMA-ECC Columns

• Tazarv and Saiidi (2014)• Also Journal Publications

http://wolfweb.unr.edu/homepage/saiidi/caltrans/NextGen/PDFs/CCEER-14-06-Tazarv-Saiidi.pdf

Design Guideline:

Pocket/Socket Connections

http://www.abc-utc.fiu.edu/

Design Guideline:

Mechanically Spliced Columns

http://www.abc-utc.fiu.edu/

• Utah• Florida• Tazarv and Saiidi (2015)

Conclusions

Advanced materials can be used to

build longer-lasting bridges faster

with continuous functionality even

after severe earthquakes

39

Questions?

40

Mostafa TazarvAssistant Professor

Department of Civil and Environmental Engineering

South Dakota State University (SDSU)

mostafa.tazarv@sdstate.edu

Mechanically Spliced Columns

Construction Time (Day) for Precast Columns with Couplers

Construction Step CIP Shear

Screw

Headed

Bar

Grouted

Sleeve Threaded Swaged

Column-to-Footing Connections

Excavate Footing 1 1 1 1 1 1

Build Footing Formwork 2 2 2 2 2 2

Set Footing Rebar 1 1 1 1 1 1

Set Column Steel 1 N/A N/A N/A N/A N/A

Pour Footing Concrete 1 1 1 1 1 1

Grout Bedding Layer N/A N/A N/A 0.25 N/A N/A

Set/Level Column N/A 0.25 0.25 0.25 0.25 0.25

Fasten Screws/Couplers N/A 0.25 0.5 N/A 0.5 1

Grout Couplers N/A N/A N/A 0.5 N/A N/A

Grout Curing Time N/A N/A N/A 1 N/A N/A

Additional Steps for Different

Detailing* N/A 1 1 N/A 1 1

Build Column Formwork 1.5 N/A N/A N/A N/A N/A

Pour Column Concrete 1 N/A N/A N/A N/A N/A

Cure Time to 80% (Min 5 Days) 5 N/A N/A N/A N/A N/A

Construction Time 13.5 6.5 6.75 7 6.75 7.25

Time Saving for Column-to-Footing -- 7 6.75 6.5 6.75 6.25

Column-to-Cap Beam Connections

Build Shoring/Soffit 4 N/A N/A N/A N/A N/A

Set Cap Beam Rebar 2 N/A N/A N/A N/A N/A

Finish Formwork/Pour Concrete 1 N/A N/A N/A N/A N/A

Set Shims/Shoring, Sealing, and

Surveying N/A 0.25 0.25 1 0.25 0.25

Grout Bedding Layer N/A N/A N/A 0.25 N/A N/A

Set/Level Cap Beam N/A 0.25 0.25 0.25 0.25 0.25

Grout Couplers N/A N/A N/A 0.5 N/A N/A

Fasten Screws/Couplers N/A 0.25 0.5 N/A 0.5 1

Additional Steps for Different

Detailing* N/A 1 1 N/A 1 1

Grout Cure Time N/A N/A N/A 1 N/A N/A

Cure Time to 80% (Min 5 Days) 5 N/A N/A N/A N/A N/A

Construction Time 12 1.75 2 3 2 2.5

Time Saving for Column-to-Cap

Beam -- 10.25 10 9 10 9.5

Total Construction Time for Bent

Total Bent Construction Time 25.5 8.25 8.75 10 8.75 9.75

Total Time Saving for Precast Bent -- 17.25 16.75 15.5 16.75 15.75

Total Time Saving for Precast Bent

(%) -- 68 66 61 66 62

Note: Construction time for the CIP and the grouted coupler bent are based on Marsh et al. (2011).

It is assumed that columns and the cap beam are precast.

* It is not possible to complete a precast connection without taking additional steps. For example, to

be able to use headed bar couplers in the plastic hinge area, a space is needed to fit the couplers

inside the precast column thus casting of this space imposes extra step.

Three times faster in construction

Plastic Hinge Length for Couplers

42

Cou

ple

r

Reg

ion

Lsp

db

a.db

Bar

Reg

ion

a.db

ß.Lsp

Bar

Reg

ion

Rig

id

Len

gth

Lcr

Column Section

Hsp

Lsp

Elem. 1

Elem. 2

Ele

m.

3

L

Footing

Co

up

lers

A modified plastic hinge length for coupler columns

𝐿𝑝𝑠𝑝= 𝐿𝑝 − (1 −

𝐻𝑠𝑝

𝐿𝑝)𝛽𝐿𝑠𝑝 ≤ 𝐿𝑝

Generic Model for Couplers

43

Column Section

Hsp

Lsp

Elem. 1

Elem. 2

Ele

m.

3

L

Footing

Co

up

lers

𝜇𝑠𝑝

𝜇𝐶𝐼𝑃= (1 − 0.18𝛽)

𝐻𝑠𝑝

𝐿𝑠𝑝

0.1𝛽

Coupler Rigid Length Factor 1

Coupler type 𝜺𝒔𝒑

𝜺𝒔 from Test Measured 𝜷 Suggested(a)

Shear Screw N/A N/A 0.5

Headed Bar 0.7 0.77 0.75

Grouted Sleeve 0.42 0.64 0.65

Threaded N/A N/A 0.25

Swaged N/A N/A 0.5

Note: “Suggested” values need to be verified for 2

different coupler types and coupler series. 3 Validation of Design Equation Accounting for Coupler Effects 1

Reference / Specimen Title Calculated Measured

Haber et al. (2014) / GCNP

Column with grouted couplers

immediately above the footing

surface

𝛽 = 0.65

𝐻𝑠𝑝 = 0. use 𝐻𝑠𝑝 = 0.1 𝑖𝑛. (2.5 𝑚𝑚)

𝐿𝑠𝑝 = 14.57 𝑖𝑛. ( 370 𝑚𝑚)

thus

𝜇𝑠𝑝

𝜇𝐶𝐼𝑃= (1 − 0.18𝛽)

𝐻𝑠𝑝

𝐿𝑠𝑝

0.1𝛽

= 0.64

𝜇𝑠𝑝

𝜇𝐶𝐼𝑃=

4.52

7.36= 0.61

Haber et al. (2014) / HCNP

Column with headed bar couplers

5 in. (127 mm) above the column-

to-footing interface

𝛽 = 0.75

𝐻𝑠𝑝 = 4 𝑖𝑛. (122 𝑚𝑚)

𝐿𝑠𝑝 = 3.13 𝑖𝑛. (79 𝑚𝑚)

thus

𝜇𝑠𝑝

𝜇𝐶𝐼𝑃= (1 − 0.18𝛽)

𝐻𝑠𝑝

𝐿𝑠𝑝

0.1𝛽

= 0.88

𝜇𝑠𝑝

𝜇𝐶𝐼𝑃=

6.49

7.36= 0.88

Pantelides et al. (2014) / GGSS-1

Column with grouted couplers

immediately above the footing

surface

𝛽 = 0.65

𝐻𝑠𝑝 = 0. use 𝐻𝑠𝑝 = 0.1 𝑖𝑛. (2.5 𝑚𝑚)

𝐿𝑠𝑝 = 14.57 𝑖𝑛. ( 370 𝑚𝑚)

thus

𝜇𝑠𝑝

𝜇𝐶𝐼𝑃= (1 − 0.18𝛽)

𝐻𝑠𝑝

𝐿𝑠𝑝

0.1𝛽

= 0.64

𝜇𝑠𝑝

𝜇𝐶𝐼𝑃=

5.4

8.9= 0.61

2

Both design equation and the modified plastic hinge length equation were verified using available test data

Pocket/Socket Connections

Construction Time (Day) for Cap Beam Pocket Connections

Construction Step CIP Alt-1 Alt-2 Alt-3 Alt-4 Alt-5

Build Shoring/Soffit 4 4 4 4 4 N/A

Set Cap Beam Rebar 2 N/A N/A N/A N/A N/A

Finish Formwork/Pour Concrete 1 N/A N/A N/A N/A N/A

Set Shims/Shoring, Sealing and Surveying N/A 1 1 1 1 1

Set/Level Cap Beam N/A 0.5 0.5 0.5 0.5 0.5

Pour Pocket Concrete/Grout N/A 0.5 0.5 0.5 0.5 0.5

Grout Cure Time* N/A 1 1 1 1 1

Cure Time to 80% (Min 5 Days)* 5 N/A N/A N/A N/A N/A

Total Construction Time 12 7 7 7 7 3

Total Time Saving (Day) -- 5 5 5 5 9

Total Time Saving (%) -- 42 42 42 42 75

Note: Construction time for CIP is based on Marsh et al. (2011)

* It was assumed that the pocket is filled with grout. If concrete or SCC is used, the cure time is 5

days thus the time saving for Alt-1 to 4 is minimal (8%).

Can be four times faster in construction

Advanced Materials: SMA

We developed “design specifications”:

Strain (%)

Str

ess

k1

k 2fy

ß.f y

k3Nonlinear

Model

u

k 2

k1

=a.k1

Parameter Minimum(a) Expected(b)

Austenite modulus, 𝑘1 4500 ksi (31025 MPa) 5500 ksi (37900 MPa)

Post yield stiffness, 𝑘2 -- 250 ksi (1725 MPa)

Austenite yield strength, 𝑓𝑦 45 ksi (310 MPa) 55 ksi (380 MPa)

Lower plateau stress factor, 𝛽 0.45 0.65

Recoverable superelastic strain, 𝜀𝑟 6% 6%

Secondary post-yield stiffness ratio, 𝛼 -- 0.3

Ultimate strain, 𝜀𝑢 10% 10%

Reinforcing Superelastic

NiTi SMA Bars

80% softer and 20% weaker than steel45

Novel Columns

Novel Column

Minimized Damage

Mechanism

Large Disp. Capacity

Minimized Residual

Disp.

For Seismic

Applications