new paradigm in earthquaker engineering of bridges-resilient, fast, recyclable
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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
15
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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.
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