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2016 Mw7.8 Ecuador Earthquake: Relevance to NYC & US Critical InfrastructureEERI-NYNE and ASCE Met Section Infrastructure Group Mini-Symposium
Unreinforced Masonry BuildingsSeismic Risk andMitigation Technologies
Prof. A. Whittaker, U. BuffaloGSMT, New York City
May 30, 2017Seismic Performance of the SeismicallyIsolated Los Caras Bridge
Dr. Enrique MoralesProfessor and Chair of the Department of Civil Engineering at ESPE
UniversityMarcelo Romo M.S.
Professor of ESPE Universityand Consultant of Ecuador Army Corps of Engineers
INTRODUCTION AND SEISMIC HAZARDEcuador Location · Seismic Hazard · Site-Specific Ground Motions
LOS CARAS BRIDGE DESCRIPTION AND SEISMIC DESIGNCRITERIA
Seismically Isolated Bridges · Project Description · Structural Systems Selected · Seismically IsolatedStructure Design Criteria
SEISMIC PERFORMANCE OF ISOLATED SYSTEMRelevant Recorded Ground Motions · Seismic Performance of the Isolation System
SEISMIC PERFORMANCE OF NON-ISOLATED SYSTEMSeismic Protection System Components · Displacement Control Devices · Seismic Performance of
Displacement Control Components
MONITORING AND MAINTENANCEIsolation System · Non-Isolation System
SEISMIC PERFORMANCE IN OTHER BRIDGES
ACKNOWLEDGEMNT AND CONCLUSIONS
OUTLINE
Ecuador
(ESPE 2016)
(Source ephotopix)
Seismic Hazard of Ecuador
(Yepes 2016)
(Egred 2009)
2
Geodynamic Setting of Ecuador, theGalapagos Islands and the Carnegie
Ridge
(Toulkeridis 2013)
Response Spectrum and Code-Based Design Spectra NEC-2015
QUITO
Pedernales
MantaPortoviejo
Chone
Esmeraldas
GuayaquilGround motions provided by the Seismology Department, Instituto Geofísico, Escuela Politecnica Nacional, Ecuador with details intheir report Singaucho, J., Laurendeau, A., Viracucha, C., Ruiz, M. (2016). “Observaciones del Sismo del 16 de Abril de 2016 deMagnitud Mw 7.8”
The Ecuador 2016 Muisne Earthquake
Seismically Isolated Bridges in Ecuador
North Bridge 1 Esmeraldas (GPS: 0°58'4.31"N;79°38'42.34"W)
The Los Caras Bridge(GPS: 0°36'33.6"S, 80°24'58.7"W)
152 Triple Friction Pendulum BearingsThere are three seismically isolated bridges
(Total 36 Triple Friction Pendulum Bearings)
Source Ecuador Army Corps of Engineers (EACE) Source Aguiar R
Seismically Isolated Bridges in Ecuador
San Pedro Bridge(GPS: 0°13'10.90"S, 78°25'29.56"W)
El Chiche Bridge(GPS: 0°12'40.88"S, 78°22'9.16"W)
4 Simple Friction Pendulum Bearings 8 Simple Friction Pendulum Bearings
Source El Universo Source Google Earth
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Seismic Protection Industry
Japan Society of Seismic Isolation
Location of the Seismically IsolatedLos Caras Bridge
Source (EACE)
BAHIA DECARAQUEZ
SAN VICENTE
Chone RiverEstuary
BahíaAccess
CentralSection
San VicenteAccess
Project Description
Source (EACE)
BAHIA DE CARAQUEZ
SAN VICENTE
Chone River Estuary
Central SectionBahía Access
Los Caras Bridge
San VicenteAccess
Site-Bridge
Source (EACE)
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Lamp
Road of Bicycle
Tubular PileASTM A 588
Slab
Column
Footing
Girder
13.20 m
Base isolation
Parapet
Pier
FOUNDATION
SUBSTRUCTURE
SUPERSTRUCTURE
FINISHES
N+11.95
N+9.288
N+7.688
N+2.330
N+0.68
N+0.00
TYPICAL SECTION OF THE PIERTYPICAL SECTION OF THE PIER
Source (EACE)
Structural System Selected
• Base Isolation on Top of Piles andUnder the Bridge DeckTriple Friction Pendulum (TFP) byEarthquake Protection Systems(EPS)
• Frictional Pile Deep Foundation
• Pile Driving Analyzer (PDA) forTesting Piles
Source (EACE)
• Pier Stability ThroughRedundant Pile Linesand Redundant PierFrames
Structural System Selected
• Bridge Deck Continuity: 180 m (4 spans) and 90 m (2 spans)
Source (EACE)
Soil Condition
Source (EACE)
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• GLOBAL• Seismic System and Structural
Elements Above Isolation SystemR=1.0
• Seismic System and StructuralElements Below Isolation System
R=1.25
• SUPERSTRUCTURE• Movement Synchronizers: Local
Design• Large Displacement Seismic
Joints: Local Design• SUBSTRUCTURE
• Basic Ductility Detailing• Frictional Pile Deep Foundation
Seismically Isolated Structure DesignCriteria
Source (EACE)
Seismically Isolated Structure –DesignCriteria
• SEISMIC DESIGN HYPOTHESIS• Seismic Hazard Local Study• Seismic Provisions (CEC 2002)• Peak Rock Acceleration (from
seismic hazard map and fromseismic hazard study):ar = 0.40 g; ar = 0.42 g
• Peak Ground Acceleration:ag = 0.80 g; ag = 0.84 g
Source (EACE)
Isolator Idealization for Design
DE MCE
Target Properties
Source (EACE)
Isolator Geometry and BearingCapacities (FPT8836/14-12/10-7)
· Bearing Capacities Lateral Displacement Capacity = 23.0 inches +/- 0.3 inches.
· Average Vertical Dead Load = 600 kips used for bearing property tests.
· Maximum Vertical D+L Load Capacity = 1200 kips maximum.
· Maximum Vertical D+L+E Load Capacity = 1900 kips maximum.
· Maximum vertical load capacities are based on concave plates bearing against 5000psi concrete.
· Minimum Rotation Capacity = +/- 2 deg.
· Ri = Radius of curvature sliding surface i.
· µi = Friction coefficient of sliding surface i.
· hi = Height of sliding interface i.
· di = Displacement capacities of sliding interface i.
(Constantinou 2011)
Earthquake Protection Systems (EPS)
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Prototype Bearing Real-Time DynamicTest Program
(Total 152 Bearings)
Earthquake Protection Systems (EPS)
Relevant Recorded Ground Motions
-1500
-1000
-500
0
500
1000
0 5 10 15 20 25 30 35 40 45
-400-300-200-100
0100200300400500600
0 5 10 15 20 25 30 35 40 45
E-W Pedernales Ground Motion (PGA = 1.43 g)
N-S Manta Ground Motion (PGA = 0.53 g)
cm/s2
cm/s2
T(sec)
T(sec)
During the Ecuador 2016 Muisne Earthquake
Seismic Performance of the IsolationSystem
During the Ecuador 2016 Muisne Earthquake
Seismic Performance of the IsolationSystem
0
10
20
30
40
50
60
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48
Total Displacement(cm) of the TFPcm
Piers
Source (EACE)
During the Ecuador 2016 Muisne Earthquake
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• Seismic Movement Synchronizers –Shock Absorbers
Seismic Protection System Components
Source (EACE)
• Large Displacement Seismic Joints and Joint Seals
Seismic Protection System Components
• Seismic Movement Synchronizers
Seismic Protection System Components
Source (EACE)
• Seismic Large Displacement Joints and Joint Seals
Source (EACE)
Seismic Performance of DisplacementControl Components
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Monitoring and Maintenance of IsolationSystem
Source (EACE)
Bolts
BoltsGrout
• Seismic Movement Synchronizers• Bolt rust• Impact traces in neoprene• Superficial overheating
Source (EACE)
Monitoring and Maintenance of IsolationComponents
• Large Displacement Seismic Joint and Joint Seal• More than 35 cm displacement in any
direction• Vertical displacement
Source (EACE)
Monitoring and Maintenance of IsolationComponents
Seismic Performance of Non-IsolatedAccesses
• Longitudinal NeopreneShock Absorbers
• Steel Bar VerticalAnchorages
Source (EACE)
Displacement Control Devices in Non-Isolated Accesses
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• Transversal Seismic Shear keys
Source (EACE)
• Neoprene Bearings in San Vicente Access
Seismic Performance of Non-IsolatedComponents
Seismic Performance inOther Bridges
• Esmeraldas Bridges (PGA = 0.23 g) /Major displacements (D < 15 cm)
Source (EACE)
• Ecuador Army Corps of Engineers.
• ESPE University.
• Buffalo University.
• Earthquake Protection Systems (EPS).
• Professor Michael Constantinou.
• General Pedro Mosquera, Jorge Landazuri andFrancisco Beltran.
AcknowledgementContributions are gratefully acknowledged:
The Las Caras Bridge at 2 km length is the longest bridge in Ecuador.
It stretches across the Bahia de Caraquez'es bay and was significantly affected by the April16, 2016 M7.8 earthquake offshore the west coast of northern Ecuador.
It is seismically isolated with a triple FP isolation system designed to have a displacementcapacity of 585 mm.
The bridge remained functional during and after the earthquake and it represented asignificant link in reaching the most affected cities by the earthquake for providing aid.
Records of ground shaking at stations before and after the bridge in the direction ofpropagation of the earthquake rupture show peak ground accelerations between 0.5g and1.4g.
It was evident that was significant variability in the ground shaking from pier (within about 120m) as the bearing displacement recorded varied from about 100 mm to about 650 mm. Thiswas without doubt the largest ever recorded motion of a seismically isolated structure.
Conclusions
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The Mw 7.8 Earthquake in Muisne, Ecuador in 2016 produced large transversal movementson seismic joints in Los Caras Bridge, up to 32 cm, equivalent to 90% of DE intensity level.
Seismic joints designed for Los Caras Bridge worked as expected.
Vertical movements of seismic joints proved to be important for major earthquakes.
Synchronizers employed in isolated bridges, designed according to a conceptual methodbehaved adequately under a major Mw 7.8 earthquake, with ground accelerations similar to aDE earthquake.
It demonstrated the significance of a proper philosophy for design that ensures a smallenough risk of damage and collapse.
Conclusions