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New Paradigm in Earthquake Engineering of Bridges- Resilient, Fast, Recyclable

M. Saiid Saiidi

http://wolfweb.unr.edu/homepage/saiidi/Professor, Department of Civil and Environmental Engineering

Director, Center for Advanced Technology in Bridges and Infrastructure

Co-Director, ABC-UTC

Research AssistantsZachary Haber, PhD, Project Engineer

Genex Systems, Washington, DC

Mostafa Tazarv, PhD, Asst. Prof.

S. Dakota State Univ., Brookings

Melissa O’Brien, MSCE, Structural Engineer

Sebastian Varela, PhD, Freese & Nickols, Forth Worth, Texas

Fatemeh Kavianipour, PhD, Staff Engineer,

Kleinfelder, San Diego, California

Brian Nakashoji, MSCE, Structural Engineer,

Professional Service Industries, Washington, DC

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UNR EQ Engineering Lab—Largest facility in the US w/ 4

shake tables

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Modern Concepts in Bridges

1- Novel materials

2- Novel construction approach

Novel Materials in Earthquake-Resistant Concrete Bridges

• Performance during earthquake

• Serviceability after earthquakeNew

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Target performance for standard bridges during earthquake: No Collapse

Damaged Bridges Have to Be Closed

-Ambulances and fire trucks-Other emergency response vehicles-Public transportation-Major economic impact (locally; can be regional and global)

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• Serviceability after earthquake:

Minimize permanent drift and damage

• Advanced materials/details

Shape memory alloys

Ductile concrete/UHPC

Columns w/ built-in elastomeric pads

Fiber-reinforced polymers

Post-tensioning

Concrete + Steel >> One Combination

Advanced Materials/Details >> Over 40 Combinations

Only 8 have been proof tested!

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Novel Columns – NCHRP 12-101

Footing

FRP Jacket

ReinforcingSteel

Concrete

Footing

FRP Jacket

ReinforcingSteelC

oncr

ete

FR

P T

endo

n

Footing

FRP Jacket

ReinforcingSteelC

oncr

ete

Ste

el T

endo

n

Footing

FRP Jacket

ReinforcingSteelC

oncr

ete

FR

P

Rubber

Ten

don

Footing

FRP Jacket

ReinforcingSteelC

oncr

ete

Stee

l

Rubber

Ten

don

Footing

ReinforcingSteelC

oncr

ete

FRP

Rubber

Ten

don

Footing

ReinforcingSteelC

oncr

ete

Ste

el

Rubber

Ten

don

Footing

FRP Jacket

ReinforcingSMA

Concrete

Cou

pler

Footing

FRP Jacket

ReinforcingFRP

Concrete

Footing

FRP Jacket

ReinforcingSMA

Concrete

RubberCou

pler

Footing

FRP Jacket

ReinforcingSMA

RubberCou

pler

FR

PT

endo

n

Con

cret

e

Footing

FRP Jacket

ReinforcingFRP

Rubber

FRP

Ten

don

Con

cret

e

Footing

FRP Jacket

ReinforcingSMA

RubberCou

pler

Ste

elT

endo

n

Con

cret

e

Footing

ReinforcingSteel

UHPC

Footing

ReinforcingSteel

UHPC

FRP Jacket

Footing

ReinforcingSteelU

HPC

FRP

Ten

don

Column Type 1 to 16

Evolution in SMA (Nickel Titanium) Use/Research

Also military applications

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Shape Memory Alloy• Superelastic

response

• Shape memory effects

• NiTi SMA developed in1962

• Cu-Al-Mn SMA being developed

• Fe-based SMAs–not superelastic

NiTi Bar Application

• Very expensive! Approx. 90 x steel cost

• Limit its use only in plastic hinges

Steel

NiTi

Steel

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Combining SMA Bars with Engineered Cementitious Composites(ECC, Ductile Concrete)

1. Fiber-reinforced cementitious composite2. Tensile strain-hardening behavior3. Typically 2% or less fiber content by

volume

Combining SMA Bars with Engineered Cementitious Composites (ECC, Ductile Concrete)

Polyvinyl AlcoholFiber

0

200

400

600

800

1000

0 0.5 1 1.5 2 2.5 3 3.5 4Strain (%)

Ten

sile

Str

ess

(ps

i)

0

1.4

2.8

4.2

5.6

7T

ensi

le S

tres

s (M

Pa

)

Conventional Concrete

ECC

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SR99-RC (8% Drift) SR99-LSE (12%

Drift)SR99-SSE (10%

Drift)

Damage at End of Testing

SR99-RC Force-Displacement Hysteresis

10

0

1

2

3

4

5

6

7

0 2 4 6 8 10 12

Res

idu

al D

rift

(%

)

Drift (%)

Measured Residual Drift Ratios

SR99-RC

SR99-LSE

SR99-SSE

Novel Construction Concept-Precast Bridges>> Accelerated Bridge

Construction (ABC) • Motivation: Minimize traffic interruption

• Main advantages: – Better quality bridges because of casting in

plants

– Reduced construction zone accidents

• Main disadvantages:– Requires more precision

– Connections in high seismic areas- limited test data (emerging)

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Why high seismic zone matters?

• ABC relies on precast members that are connected in the field.

Connecting Columns to Cap Beams/Footings

Coupler OptionGrouted sleevesHeaded bar couplersSwagedShear screw

Non-Coupler OptionGrouted ductsPrestressed systemsPocket connectionsEmbedded columns

OthersPins/hingesReplaceable connectionsEtc.

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Coupler (Mechanical Bar Splice) Connections

Code Coupler Type Plastic Hinge

AASHTO Full Mech. Connection No

Caltrans Service No

Ultimate No

ACI Type 1 No

Type 2 Yes

Recent Seismic Studies of Columns w/ Couplers

Grouted Couplers in Nevada, Utah, FloridaDisplacement ductility of 4.5 or

more

Headed Bar Couplers in NevadaDisplacement ductility of 7- same

as CIP

QUESTION: Should the ban on couplers in plastic hinges be removed?

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Grouted ducts

Prestressed Systems

Non-Coupler OptionGrouted ductsPrestressed systemsPocket connectionsEmbedded columns

4 New Details

Post-tensioned segmental columns wrapped with

CFRPConcrete filled tube

CIP columnsConcrete filled tube

precast columns

Pipe pin

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Precast Pier

Segmental Pier

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After Final Run (9% drift)

CIP Bent Precast Bent

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Current ABC System Studies at UNRPI: Saiidi

• Three 0.35-scale, 2-span bridge models

• Two with concrete superstructure; one with steel superstructure

• One concrete and the steel bridge under construction- Testing: Sept. 2017 and Jan. 2018

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Caltrans Bridge 1Study the performance under bidirectional earthquakes of two

large-scale bridge systems incorporating ABC connections

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Bridge 1

• Deck: ts=8”’ 5ksi

• Girders: CAWF-4834 0.6”-dia.

strands’ 8ksi

• Columns: =4.5’18#14 ( 1.77%)#8@4” ( 1.61%)’ 4ksi

• Caltrans SDC and BDSCaltrans Amendments to AASHTO

LRFDAASHTO-LRFD

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Abutment End Diaphragm

Intermediate Diaphragms

Deck Pockets

Extended bars to splice over the pier

Shear Connectors

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Test Day: Sept 20, 2017

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Deconstructible bridges w/ advanced materials

Combines novel materials and ABC

Objectives:

Develop bridge columns that1- Withstand strong earthquakes with no or minor damage so they are useable after earthquakes.2- Can be disassembled and reused.

6% of CO2 emission in the world is from cement factories.

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Plastic Hinge Elements

Longitudinal Reinforcement in PHShape Memory Alloys (SMA)

Ni-Ti Cu-Al-MN

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Capacity-protected column outside PH

ECC; NiTi; Copper Based SMA; Rubber; CFRP Shell

Rubber Pad

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Apparent damage in CE-R

Two-Span Bridge Model

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Original Bridge- Test to 6% Drift

After disassembly

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Reassembled Bridge Test to Failure (10% drift)

Implementation of SMA/ECC in Showcase Bridge

• Alaska Way Viaduct Replacement, Seattle, WA

• Three Spans (110ft; 180ft, 110ft)

• Precast Post-Tensioned Splice Tub Girder

• Single Column Piers

• Square Columns (5ft x 5ft) w/ Circular Core

• ECC Full Length of Column

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Nickel-Titanium Bars

• Challenges with including SMA in a contract– Cost

• ASTM A706 = $1 / lb.

• SMA = $87 / lb.

– Schedule – 6 month delivery, not including process to head bar for mechanical splice

– Mechanical splice required in hinge region

HRC Couplers in Seattle Alaska Way Viaduct- CIP

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Message

• Embracing novel materials and construction concepts could transform the bridge engineering field to more resilient and durable bridges that better serve the public.